Patent Publication Number: US-2020281659-A1

Title: Calibration apparatus and methods for calibrating a medical instrument

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This document is a utility application claiming the benefit of, and priority to: U.S. Design application Ser. No. 29/588,647 filed on Dec. 22, 2016, entitled “CALIBRATION APPARATUS” all of which are both hereby incorporated by reference in their entirety herein for all purposes. 
     TECHNICAL FIELD 
     The present disclosure is generally technically related to image guided medical procedures. More particularly, the present disclosure is generally technically related to a calibration apparatus for a medical tool. Even more particularly, the present disclosure is generally technically related to a calibration apparatus for a medical tool used in image guided medical procedures. 
     BACKGROUND 
     The related art generally involves image guided medical procedures using a surgical instrument, such as a fiber optic scope, an optical coherence tomography (OCT) probe, a micro ultrasound transducer, an electronic sensor or stimulator, or an access port-based surgery. In the example of a port-based surgery, a surgeon or robotic surgical system may perform a surgical procedure involving tumor resection in which the residual tumor remaining after is minimized, while also minimizing trauma to the intact white and grey matter of the brain. In such procedures, trauma may occur, for example, due to contact with the access port, stress to the brain matter, unintentional impact with surgical devices, and/or accidental resection of healthy tissue. A key to minimizing trauma is ensuring that the spatial reference of the patient and the medical tools used in the procedure as understood by the surgical system is as accurate as possible. 
       FIG. 1  illustrates the insertion of an access port into a human brain, for providing access to internal brain tissue during a medical procedure, in accordance with the related art. In  FIG. 1 , an access port  12  is inserted into a human brain  10 , providing access to internal brain tissue. The access port  12  may include such instruments as catheters, surgical probes, or cylindrical ports, such as the NICO® BrainPath®. Surgical tools and instruments may then be inserted within the lumen of the access port in order to perform surgical, diagnostic, or therapeutic procedures, such as resecting tumors, as necessary. The present disclosure applies equally well to catheters, deep brain stimulation (DBS) needles, a biopsy procedure, and also to biopsies and/or catheters in other medical procedures performed on other parts of the body. 
     In the example of a port-based surgery, a straight or linear access port  12  is typically guided down a sulci path of the brain. Surgical instruments would then be inserted down the access port  12 . Optical tracking systems, used in a medical procedure, track the position of a part of the instrument that is within the line-of-site of the optical tracking camera. These optical tracking systems require a knowledge of the dimensions of the instrument being tracked so that, for example, the optical tracking system knows the position in space of a tip of a medical instrument relative to the tracking markers being tracked. 
     Conventional systems have shortcomings with respect to establishing and maintaining the reference between the tracking markers located on a medical instrument and the point of interest on the instrument relative to those tracking markers for reasons, such as instruments bending or deforming over time. Additionally, the related art calibration devices face challenges in relation to tools having a variety of cross-sectional shapes and cross-sectional areas, e.g., having various diameters. Also, the related art calibration devices use software that is challenged by tools of various sizes. Therefore, a need exists for an improved calibration of optical tracking systems with respect to the various medical instruments that those tracking systems must track. 
     SUMMARY 
     To address at least the challenges experienced in the related art, in an embodiment of the present disclosure, a calibration apparatus for calibrating a medical tool having a tool tracking marker is provided. The medical tool and the calibration apparatus are for use with a medical navigation system. The calibration apparatus comprises a frame, a frame tracking marker attached to the frame, and a reference point feature formed on the frame or the body. The reference point feature provides a known spatial reference point relative to the frame tracking marker. 
     In addition, the calibration apparatus increases accuracy of an entire navigation system, such as an image-guided navigation system, in accordance with embodiments of the present disclosure. By calibrating a tracked tool via the calibration apparatus, at least the following solutions are provided: (a) the navigation system is adaptable for using tools having higher tolerances than those in the related art, whereby the calibration apparatus is configured to correct for variations from a nominal variation to a large variation (relative to calibration devices in the related art), and whereby tool fabrication costs are decreased, (b) a tracked tool is configurable by an end user, e.g., by configuring a suction tool in relation to a plurality of possible tool tip locations, and (c) a tracked tool is configurable, regardless of tip geometry, e.g., providing a solution for both a pointed tool tip which seat well in relation to a bottom portion of a conical divot and for a cylindrical tool tip (such as for a suction tool) which may, otherwise, seat at a location above a bottom portion of a conical divot and may not be centered when seated. 
     In relation to the foregoing solution (c), related art challenges are addressed by the calibration apparatus of the present disclosure via a feature for abutting all tips against a flat surface while using a feature for centering the axis of the tool in a known position, whereby any tool, regardless of diameter, cross-sectional area, cross-sectional shape, or other tip geometry, seats in the calibration apparatus in the same manner. Also, the calibration apparatus increases accuracy of an entire navigation system, such as a non-image-guided navigation system, in accordance with embodiments of the present disclosure. For a non-image-guided navigation system, the calibration apparatus is configured for use with the Synaptive® Drive® system, wherein the foregoing solution (b) is applicable, and wherein calibration information is used to align an optical payload. 
     In embodiments of the present disclosure, a frame tracking marker comprises at least one of a passive reflective tracking marker, such as at least one of a passive reflective tracking sphere and a passive reflective tracking disk, an active infrared (IR) marker, an active light emitting diode (LED), and a graphical pattern. The frame may have at least three tracking markers attached to a same side of the frame. 
     In an embodiment of the present disclosure, a medical navigation system comprises a medical tool, a calibration apparatus, and a controller. The medical tool has a tool tracking marker. The calibration apparatus is configured to calibrate the medical tool and comprises a frame, a frame tracking marker attached to the frame, and a reference point feature disposed in relation to the frame. The reference point feature provides a known spatial reference point relative to the frame tracking marker. The medical navigation system further comprises a sensor coupled with the controller for detecting the tracking markers, e.g., the frame tracking markers. The sensor provides a signal to the controller to indicate the positions of the tracking markers in space. The reference point feature may include a divot whereby the tip of the medical tool (which has at least three tracking markers attached thereto) is insertable into the divot to abut against the floor of the divot for calibrating and verifying the medical tool dimensions by the medical navigation system. 
     In an embodiment of the present disclosure, a method of verifying dimensions of a medical tool having an attached tool tracking marker comprises using a calibration apparatus having a frame, a frame tracking marker attached to the frame, and a reference point feature disposed in relation to the frame. The reference point feature provides a known spatial reference point relative to the frame tracking marker. The method further comprises: detecting the tool tracking marker and the frame tracking marker; calculating the expected spatial relationship of the tool tracking marker relative to the frame tracking marker; and re-registering the tool when the dimensions of the medical tool have changed beyond a given, predetermined, defined, or predefined threshold. 
     In an embodiment of the present disclosure, a calibration apparatus, operable with a medical navigation system, for calibrating a medical tool having a tip, comprises: a calibration body configured to accommodate a plurality of tool dimensions and having a plurality of cooperating spring-loaded cams for accommodating a plurality of tool cross-sectional dimensions; a frame configured to couple with the calibration body and having at least one frame tracking marker coupled therewith; and a reference point feature coupled with the calibration body, the reference point feature providing a known spatial reference point relative to the at least one frame tracking marker. 
     In an embodiment of the present disclosure, a method of fabricating a calibration apparatus, operable with a medical navigation system, for calibrating a medical tool having a tip, comprises: providing a calibration body configured to accommodate a plurality of tool dimensions and having a plurality of cooperating spring-loaded cams for accommodating a plurality of tool cross-sectional dimensions; providing a frame configured to couple with the calibration body and having at least one frame tracking marker coupled therewith; and providing a reference point feature coupled with the body, the reference point feature providing a known spatial reference point relative to the at least one frame tracking marker. 
     In an embodiment of the present disclosure, a method of calibrating a medical tool, having a tip, by way of a calibration apparatus, operable with a medical navigation system, comprises: providing the calibration apparatus comprising: providing a calibration body configured to accommodate a plurality of tool dimensions and having a plurality of cooperating spring-loaded cams for accommodating a plurality of tool cross-sectional dimensions; providing a frame configured to couple with the calibration body and having at least one frame tracking marker coupled therewith; and providing a reference point feature coupled with the calibration body, the reference point feature providing a known spatial reference point relative to the at least one frame tracking marker; detecting the at least one tool tracking marker and the at least one frame tracking marker; calculating the expected spatial relationship of the at least one tool tracking marker relative to the at least one frame tracking marker; and re-calibrating the tool if at least one tool dimension if the medical tool is altered beyond a threshold value in relation to the expected spatial relationship. The method of calibrating further comprises verifying a tool, wherein verifying the tool comprises abutting a tip of the tool against a floor of a divot. 
     A further understanding of the functional and structural features as well as aspects of the present disclosure is provided by the following Detailed Description and the Drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The above, and other, aspects and features of several embodiments of the present disclosure will be more apparent from the following Detailed Description as presented in conjunction with the following several figures of the Drawing. 
         FIG. 1  is a diagram illustrating, in a side view, the insertion of an access port into a human brain, for providing access to internal brain tissue during a medical procedure, in accordance with the related art. 
         FIG. 2  is a diagram illustrating, in a perspective view, a surgical environment, such as an operating room, wherein an exemplary navigation system to support minimally invasive surgery may be implemented, in accordance with an embodiment of the invention. 
         FIG. 3  is a block diagram illustrating a control and processing system useable in the navigation system, as shown in  FIG. 2 , in accordance with an embodiment of the invention. 
         FIG. 4A  is a flow diagram illustrating a method of using the navigation system, as shown in  FIG. 2 , for a surgical procedure, in accordance with an embodiment of the invention. 
         FIG. 4B  is a flow diagram illustrating alternative steps of registering a patient for a surgical procedure, in the method of using the navigation system, as shown in  FIG. 4A , in accordance with an embodiment of the invention. 
         FIG. 5  is a diagram illustrating, in a perspective view, an exemplary tracked instrument with which embodiments of the present disclosure may be implemented. 
         FIG. 6  is a diagram illustrating, in a frontal perspective view, the tracked instrument, as shown in  FIG. 5 , inserted into a calibration apparatus, in accordance with an embodiment of the invention. 
         FIG. 7  is a diagram illustrating, in a frontal perspective view, the calibration apparatus, as shown in  FIG. 6 , in accordance with an embodiment of the invention. 
         FIG. 8  is a diagram illustrating, in a front view, the calibration apparatus, as shown in  FIG. 7 , in accordance with an embodiment of the invention. 
         FIG. 9  is a diagram illustrating, in a rear view, the calibration apparatus, as shown in  FIG. 7 , in accordance with an embodiment of the invention. 
         FIG. 10  is a diagram illustrating, in a side view, the calibration apparatus, as shown in  FIG. 7 , in accordance with an embodiment of the invention. 
         FIG. 11  is a diagram illustrating, in an opposing side view, the calibration apparatus, as shown in  FIG. 7 , in accordance with an embodiment of the invention. 
         FIG. 12  is a diagram illustrating, in a top view, the calibration apparatus, as shown in  FIG. 7 , in accordance with an embodiment of the invention. 
         FIG. 13  is a diagram illustrating, in a bottom view, the calibration apparatus, as shown in  FIG. 7 , in accordance with an embodiment of the invention. 
         FIG. 14  is a flow diagram illustrating a method of verifying and re-registering a medical tool, in accordance with an embodiment of the invention. 
         FIG. 15A  is a diagram illustrating, in a cutaway perspective view, a calibration body, as included in a calibration apparatus, operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 15B  is a diagram illustrating, in an alternate cutaway perspective view, a calibration body, as included in a calibration apparatus and shown in  FIG. 15A , operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 15C  is a diagram illustrating, in a perspective view of a calibration body, as included in a calibration apparatus and shown in  FIG. 15A , operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 16A  is a diagram illustrating, in a perspective view, a calibration body, as included in a calibration apparatus, operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 16B  is a diagram illustrating, in a cutaway perspective view, a calibration body, as included in a calibration apparatus and shown in  FIG. 16A , operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 17A  is a diagram illustrating, in a perspective view, a calibration body, as included in a calibration apparatus, operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 17B  is a diagram illustrating, in a cutaway top perspective view, a calibration body, as included in a calibration apparatus and shown in  FIG. 17A , operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 18  is a diagram illustrating, in a frontal perspective view, a calibration apparatus, operable with a medical navigation system, for calibrating a medical device having a tip, such as a tracked instrument, wherein the medical tool is inserted into the calibration apparatus, in accordance with an embodiment of the present disclosure. 
         FIG. 19A  is a diagram illustrating, in a perspective view, a calibration apparatus, operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 19B  is a diagram illustrating, in a cutaway perspective view, a calibration apparatus, as shown in  FIG. 19A , operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 19C  is a diagram illustrating, in an alternate perspective view, a calibration apparatus, operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 19D  is a diagram illustrating, in an alternate cutaway perspective view, a calibration apparatus, as shown in  FIG. 19C , operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 19E  is a diagram illustrating, in an exploded perspective view, a calibration apparatus, operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 20A  is a diagram illustrating, in a perspective view, a calibration apparatus, operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 20B  is a diagram illustrating, in an alternate perspective view, a calibration apparatus, as shown in  FIG. 20A , operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 20C  is a diagram illustrating, in a top view, a calibration apparatus, as shown in  FIG. 20A , operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 20D  is a diagram illustrating, in a bottom view, a calibration apparatus, as shown in  FIG. 20A , operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 20E  is a diagram illustrating, in a side view, a calibration apparatus, as shown in  FIG. 20A , operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 20F  is a diagram illustrating, in an opposing side view, a calibration apparatus, as shown in  FIG. 20A , operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 20G  is a diagram illustrating, in a front view, a calibration apparatus, as shown in  FIG. 20A , operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 20H  is a diagram illustrating, in a rear view, a calibration apparatus, as shown in  FIG. 20A , operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 21  is a flow diagram illustrating a method of fabricating a calibration apparatus, operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 22  is a flow diagram illustrating a method of calibrating a medical device, having a tip, by way of a calibration apparatus, operable with a medical navigation system, in accordance with an embodiment of the present disclosure. 
         FIG. 23  is a diagram illustrating, in a frontal perspective view, a calibration apparatus, operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 24  is a diagram illustrating, in a rearward perspective view, a calibration apparatus, operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 25  is a diagram illustrating, in a rear view, a calibration apparatus, operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 26  is a diagram illustrating, in a side view, a calibration apparatus, operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 27  is a diagram illustrating, in an opposing side view, a calibration apparatus, operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 28  is a diagram illustrating, in a front view, a calibration apparatus, operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 29  is a diagram illustrating, in a top view, a calibration apparatus, operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 30  is a diagram illustrating, in a bottom view, a calibration apparatus, operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 31  is a diagram illustrating, in an alternate frontal perspective view, a calibration apparatus, operable with a medical navigation system, for calibrating a medical device having a tip, wherein the upper holder ring is removed to show internal components, in accordance with an embodiment of the present disclosure. 
         FIG. 32  is a diagram illustrating, in an alternate rearward perspective view, a calibration apparatus, operable with a medical navigation system, for calibrating a medical device having a tip, wherein the upper holder ring is removed to show internal components, in accordance with an embodiment of the present disclosure. 
         FIG. 33  is a diagram illustrating, in an exploded frontal perspective view, a calibration apparatus, operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 34  is a flow diagram illustrating a method of fabricating a calibration apparatus, as shown in  FIG. 23 , operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. 
         FIG. 35  is a flow diagram illustrating a method of calibrating a medical device having a tip by way of a calibration apparatus, as shown in  FIG. 23 , operable with a medical navigation system, in accordance with an embodiment of the present disclosure. 
     
    
    
     Corresponding reference numerals or characters indicate corresponding components throughout the several figures of the Drawing. Elements in the several figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be emphasized relative to other elements for facilitating understanding of the various presently disclosed embodiments. Also, common, but well-understood, elements that are useful or necessary in commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present disclosure. 
     DETAILED DESCRIPTION 
     Various embodiments and aspects of the present disclosure are described with reference to below-discussed details. The following description and drawings are illustrative of the present disclosure and are not to be construed as limiting the present disclosure. Numerous specific details are described to provide a thorough understanding of various embodiments of the present disclosure. However, in certain instances, well-known or conventional details are not described in order to provide a concise discussion of embodiments of the present disclosure. 
     As used herein, the terms, “comprises” and “comprising” are to be construed as being inclusive and open ended, and not exclusive. Specifically, when used in the specification and claims, the terms, “comprises,” “comprising,” and variations thereof denote the specified features, steps, or components that are included, but not limited thereto. These terms are not to be interpreted to exclude the presence of other features, steps, or components. 
     As used herein, the term “exemplary” denotes “serving as an example, instance, or illustration,” and should not be construed as preferred over other configurations disclosed herein. 
     As used herein, the terms “about” and “approximately” denote covering variations that may exist in the upper and lower limits of the presently disclosed ranges of values, such as variations in properties, parameters, and dimensions. In one non-limiting example, the terms “about” and “approximately” denote plus or minus 10 percent or less. 
     Unless defined otherwise, all technical and scientific terms used herein are intended to have the same definition as commonly understood by one of ordinary skill in the art. Unless otherwise indicated, such as through context, as used herein, the following terms are intended to have the following definitions: 
     As used herein, the phrase “access port” refers to a cannula, conduit, sheath, port, tube, or other structure that is insertable into a subject, in order to provide access to internal tissue, organs, or other biological substances. In some embodiments, an access port may directly expose internal tissue, for example, via an opening or aperture at a distal end thereof, and/or via an opening or aperture at an intermediate location along a length thereof. In other embodiments, an access port may provide indirect access, via one or more surfaces that are transparent, or partially transparent, to one or more forms of energy or radiation, such as, but not limited to, electromagnetic waves and acoustic waves. 
     As used herein, the phrase “intraoperative” refers to an action, process, method, event, or step that occurs, or is carried out, during at least a portion of a medical procedure. Intraoperative, as defined herein, is not limited to surgical procedures, and may refer to other types of medical procedures, such as diagnostic and therapeutic procedures. 
     Embodiments of the present disclosure provide imaging devices that are insertable into a subject, or patient, for imaging internal tissues, and methods of use thereof. Some embodiments of the present disclosure relate to minimally invasive medical procedures that are performed via an access port, whereby surgery, diagnostic imaging, therapy, or other medical procedures, e.g., minimally invasive medical procedures, are performed based on access to internal tissue through the access port. 
     Referring to  FIG. 2 , this diagram illustrates, in a perspective view, a navigation system environment  200 , wherein an exemplary medical navigation system  205  for supporting minimally invasive access port-based surgery is implemented, in accordance with an embodiment of the present disclosure. The exemplary navigation system environment  200  may be used to support navigated image-guided surgery. A surgeon  201  conducts a surgery on a patient  202  in an operating room (OR) environment. A medical navigation system  205  comprising an equipment tower (not shown), a tracking system  321  ( FIG. 3 ), displays or display devices  211   a ,  211   b , and tracked instruments, such as a pointer tool  500  comprising a fiducial pointer tool ( FIG. 5 ) and any other type of medical instrument, such as medical instruments  360  ( FIG. 3 ), to assist the surgeon  201  during the medical procedure. An operator  203  is also present to operate, control and provide assistance for the medical navigation system  205 . The tracked instruments, such as the pointer tool  500 , may be calibrated by way of the herein presently disclosed calibration methods. 
     Referring to  FIG. 3 , this block diagram illustrates a control and processing system  300  operable in the medical navigation system  200 , e.g., as part of the equipment tower, in accordance with an embodiment of the present disclosure. In one example, the control and processing system  300  comprises at least one processor  302 , a memory  304 , a system bus  306 , at least one input/output (I/O) interface  308 , a communications interface  310 , and storage device  312 . Control and processing system  300  may be interfaced with other external devices, such as tracking system  321 , data storage  342 , and external user input and output devices  344 , which may include, for example, at least one of a display, a keyboard, a mouse, sensors attached to medical equipment, a foot pedal, a microphone, and a speaker. The data storage  342  comprises any suitable data storage device, such as a local or remote computing device, e.g. a computer, hard drive, digital media device, or server, having a database stored thereon. In the example shown in  FIG. 3 , the data storage device  342  comprises identification data  350  for identifying one or more medical instruments  360  and configuration data  352  that associates customized configuration parameters with at least one medical instrument  360 . The data storage device  342  also comprises at least one of preoperative image data  354  and medical procedure planning data  356 . Although data storage device  342  is shown as a single device, understood is that, in other embodiments, the data storage device  342  comprises multiple storage devices. 
     Still referring to  FIG. 3 , the medical instruments  360  are identifiable by the control and processing unit  300 . The medical instruments  360  may be connected to, and controlled by, the control and processing unit  300 , or the medical instruments  360  operable, or otherwise employable, independent of the control and processing unit  300 . The tracking system  321  may be employed to track at least one medical instrument  360  and spatially register the at least one medical instrument  360  to an intraoperative reference frame. For example, medical instruments  360  may include tracking spheres that are recognizable by at least one of a tracking camera  307  and the tracking system  321 . In one example, the tracking camera  307  comprises an infrared (IR) tracking camera. In another example, a sheath placed over a medical instrument  360  is connected to, and controlled by, the control and processing unit  300 . The control and processing unit  300  may also interface with a number of configurable devices, and may intraoperatively reconfigure at least one of such devices based on configuration parameters obtained from configuration data  352 . Examples of the devices  320  include at least one external imaging device  322 , at least one illumination device  324 , a robotic arm  305 , at least one projection device  328 , and at least one display or display device  311 . 
     Still referring to  FIG. 3 , exemplary aspects of the disclosure can be implemented via at least one of the at least one processor  302  and the memory  304 . For example, the functionalities described herein are partially implementable via hardware logic in the at least one processor  302  and by partially using the instructions stored in memory  304  as at least one processing module or engine  370 . Example processing modules  370  include, but are not limited to, a user interface engine  372 , a tracking module  374 , a motor controller  376 , an image processing engine  378 , an image registration engine  380 , a procedure planning engine  382 , a navigation engine  384 , and a context analysis module  386 . While the example processing modules or engines  370  are shown separately, in one example, the processing modules or engines  370  may be stored in the memory  304 ; and a plurality of processing modules may be collectively referred to as processing modules  370 . 
     Still referring to  FIG. 3 , understood is that the system  205  is not intended to be limited to the components shown. One or more components of the control and processing system  300  may be provided as an external component or device. In one example, navigation module  384  may be provided as an external navigation system that is integrated with control and processing system  300 . 
     Still referring to  FIG. 3 , some embodiments may be implemented using processor  302  without additional instructions stored in memory  304 . Some embodiments may be implemented using the instructions stored in memory  304  for execution by one or more general purpose microprocessors. Thus, the disclosure is not limited to a specific configuration of hardware and/or software. While some embodiments can be implemented in fully functioning computers and computer systems, various embodiments are capable of being distributed as a computing product in a variety of forms and are capable of being applied regardless of the particular type of machine or computer readable media actually used to effect the distribution. At least some aspects disclosed can be embodied, at least in part, in software. That is, the techniques may be carried out in a computer system or other data processing system in response to its processor, such as a microprocessor, executing sequences of instructions contained in a memory, such as read only memory (ROM), volatile random access memory (RAM), non-volatile memory, cache or a remote storage device. 
     Still referring to  FIG. 3 , a computer readable storage medium can be used to store software and data which, when executed by a data processing system, causes the system to perform various methods. The executable software and data may be stored in various places including for example ROM, volatile RAM, non-volatile memory and/or cache. Portions of this software and/or data may be stored in any one of these storage devices. Examples of computer-readable storage media include, but are not limited to, recordable and non-recordable type media such as volatile and non-volatile memory devices, ROM, RAM, flash memory devices, floppy and other removable disks, magnetic disk storage media, optical storage media (e.g., compact discs (CDs), digital versatile disks (DVDs), etc.), among others. The instructions may be embodied in digital and analog communication links for electrical, optical, acoustical or other forms of propagated signals, such as carrier waves, infrared signals, digital signals, and the like. The storage medium may be an Internet cloud, or a computer readable storage medium such as a disc. 
     Still referring to  FIG. 3 , at least some of the methods described herein are capable of being distributed in a computer program product comprising a computer readable medium that bears computer usable instructions for execution by one or more processors, to perform aspects of the methods described. The medium may be provided in various forms such as, but not limited to, one or more diskettes, compact disks, tapes, chips, USB keys, external hard drives, wire-line transmissions, satellite transmissions, internet transmissions or downloads, magnetic and electronic storage media, digital and analog signals, and the like. The computer useable instructions may also be in various forms, including compiled and non-compiled code. 
     Still referring to  FIG. 3  and referring back to  FIG. 2 , in accordance with an embodiment of the present disclosure, an implementation of the navigation system  205 , which may include the control and processing unit  300 , involves providing tools to the neurosurgeon that will lead to the most-informed and the least-damaging neurosurgical operations. In addition to removal of brain tumours and intracranial hemorrhages (ICH), the navigation system  205  can also be applied to a brain biopsy, a functional/deep-brain stimulation, a catheter/shunt placement procedure, open craniotomies, endonasal/skull-based/ENT, spine procedures, and other parts of the body, such as breast biopsies, liver biopsies, etc. While several examples have been provided, aspects of the present disclosure may be applied to any suitable medical procedure. 
     Referring to  FIG. 4A , this flow diagram illustrates a method  400  of performing a port-based surgical procedure by way of using a navigation system, such as the medical navigation system  205 , as described in relation to  FIG. 2 , in accordance with an embodiment of the present disclosure. At a first block  402 , the port-based surgical plan is imported. Once the plan has been imported into the navigation system at the block  402 , the method  400  comprises positioning and affixing the patient into position using a body holding mechanism, as indicated by block  404 . The head position is also confirmed with the patient plan in the navigation system, as indicated by block  404 , which in one example may be implemented by the computer or controller forming part of the equipment tower (not shown). Next, registration of the patient is initiated, as indicated by block  406 . The phrase “registration” or “image registration” refers to the process of transforming different sets of data into one coordinate system. Data may include multiple photographs, data from different sensors, times, depths, or viewpoints. The process of “registration” is used in the present application for medical imaging in which images from different imaging modalities are co-registered. Registration is used in order to be able to compare or integrate the data obtained from these different modalities. 
     Still referring to  FIG. 4A , appreciated is that the present disclosure encompasses numerous registration techniques and at least one of the techniques may be applied to the present example. Non-limiting examples include intensity-based methods that compare intensity patterns in images via correlation metrics, while feature-based methods find correspondence between image features such as points, lines, and contours. Image registration methods may also be classified according to the transformation models they use to relate the target image space to the reference image space. Another classification can be made between single-modality and multi-modality methods. Single-modality methods typically register images in the same modality acquired by the same scanner or sensor type, for example, a series of magnetic resonance (MR) images may be co-registered, while multi-modality registration methods are used to register images acquired by different scanner or sensor types, for example in magnetic resonance imaging (MRI) and positron emission tomography (PET). In the present disclosure, multi-modality registration methods may be used in medical imaging of the head and/or brain as images of a subject are frequently obtained from different scanners. Examples include registration of brain computerized tomography (CT)/MRI images or PET/CT images for tumor localization, registration of contrast-enhanced CT images against non-contrast-enhanced CT images, and registration of ultrasound and CT. 
     Referring to  FIG. 4B , this flow chart illustrates the alternative steps, as respectively indicated by blocks  440  and  450 , of registering a patient for a surgical procedure, following the step of initiating registration as indicated by block  406 , and prior to the step of confirming registration, as indicated by block  408 , in the method  400  of using the navigation system, as shown in  FIG. 4A , in accordance with an embodiment of the present disclosure. If the use of fiducial touch points is contemplated, the method  400  further comprises performing step  440 , wherein performing step  440  comprises first identifying fiducials on images, as indicated by block  442 , then touching the touch points with a tracked instrument, as indicated by block  444 . Next, the navigation system computes the registration to reference markers, as indicated by block  446 . The medical navigation system  205  knows the relationship of the tip of the tracked instrument relative to the tracking markers of the tracked instrument with a high degree of accuracy for performing step, as indicated by blocks  444  and  446 , to provide useful and reliable information to the medical navigation system  205 . An example tracked instrument is discussed below with reference to  FIG. 5 ; and a calibration apparatus for verifying and establishing this relationship is discussed below in connection with  FIGS. 6-13 . 
     Still referring to  FIG. 4B , alternatively, registration can also be completed by conducting a surface scan procedure, as indicated by block  450 . The block  450  is presented to show an alternative approach, but may not typically be used when using a fiducial pointer. First, the face is scanned using a 3D scanner, as indicated by block  452 . Next, the face surface is extracted from MR/CT data, as indicated by block  454 . Finally, surfaces are matched to determine registration data points, as indicated by block  456 . Upon completion of either the fiducial touch points  440  or surface scan  450  procedures, the data extracted is computed and used to confirm registration at block  408 , shown in  FIG. 4A . 
     Still referring to  FIG. 4B  and referring back to  FIG. 4A , once registration is confirmed, as indicated by block  408 , the patient is draped, as indicated by block  410 . Typically, draping involves covering the patient and surrounding areas with a sterile barrier to create and maintain a sterile field during the surgical procedure. The purpose of draping is to eliminate the passage of microorganisms, e.g., bacteria, between non-sterile and sterile areas. At this point, conventional navigation systems require that the non-sterile patient reference is replaced with a sterile patient reference of identical geometry location and orientation. Numerous mechanical methods may be used to minimize the displacement of the new sterile patient reference relative to the non-sterile one that was used for registration but it is inevitable that some error will exist. This error directly translates into registration error between the surgical field and pre-surgical images. In fact, the further away points of interest are from the patient reference, the worse the error will be. 
     Referring back to  FIG. 4A , upon completion of draping, as indicated by block  410 , the patient engagement points are confirmed, as indicated by block  412 , and then the craniotomy is prepared and planned, as indicated by block  414 . Upon completion of the preparation and planning of the craniotomy, as indicated by block  414 , the craniotomy is cut and a bone flap is temporarily removed from the skull to access the brain, as indicated by block  416 . Registration data is updated with the navigation system at this point, as indicated by block  422 . Next, the engagement within craniotomy and the motion range are confirmed, as indicated by block  418 . Next, the procedure advances to cut the dura at the engagement points and identify the sulcus, as indicated by block  420 . 
     Still referring back to  FIG. 4A , after the dura has been cut and the sulcus identified  420 , the trajectory plan is executed as indicated by block  424  via cannulation. Cannulation involves inserting a port into the brain, typically along a sulci path as identified at  420 , along a trajectory plan. Cannulation is typically an iterative process that involves repeating the steps of aligning the port on engagement and setting the planned trajectory, as indicated by block  432 , and then cannulating to the target depth, as indicated by block  434 , until the complete trajectory plan is executed, as indicated by block  424 . Once cannulation is complete, the surgeon then performs resection, as indicated by block  426 , to remove part of the brain and/or tumor of interest. The surgeon then decannulates, as indicated by block  428 , by removing the port and any tracking instruments from the brain. Finally, the surgeon closes the dura and completes the craniotomy, as indicated by block  430 . Some aspects, shown in  FIG. 4A , are specific to port-based surgery, such as portions indicated by blocks  428 ,  420 , and  434 , but the appropriate portions of these steps may be skipped or suitably modified when performing non-port based surgery. 
     Still referring back to  FIG. 4A  and referring back to  FIG. 4B , when performing a surgical procedure using a medical navigation system  205 , the medical navigation system  205  must acquire and maintain a reference of the location of the tools in use as well as the patient in three dimensional (3D) space. In other words, during a navigated neurosurgery, there needs to be a tracked reference frame that is fixed relative to the patient&#39;s skull. During the registration phase of a navigated neurosurgery, as indicated by block  406 , a transformation is calculated that maps the frame of reference of preoperative MRI or CT imagery to the physical space of the surgery, specifically the patient&#39;s head. This may be accomplished by the navigation system  205  tracking locations of markers fixed to the patient&#39;s head, relative to the static patient reference frame. The patient reference frame is typically rigidly attached to a head fixation device, such as a Mayfield clamp. Registration is typically performed before the sterile field has been established, as indicated by blocks  406 ,  408 ,  410 . 
     Referring to  FIG. 5 , this diagram illustrates, in a perspective view, an exemplary tracked instrument, such as a pointer tool  500 , to which aspects of calibration apparatus, such as the calibration apparatus  600  ( FIG. 6 ), are operable, in accordance with an embodiment of the present disclosure. In one example, the pointer tool  500  comprises a fiducial pointer tool. The pointer tool  500  may be considered an exemplary instrument for navigation having either a straight or slightly blunt tip  502 . The slenderness of the tip  502  on a handheld pointer allows for precise positioning and localization of external fiducial markers on the patient. The tip  502  is located at the end of a shaft  504 . The shaft  504  is connected to a handle portion  506 . The handle portion  506  connects to a frame  508  that supports a number of tracking markers  510 . 
     Still referring to  FIG. 5 , the pointer tool  500  has four passive reflective tracking markers or spheres, but any suitable number of tool tracking markers  510  may be used and any suitable type of tool tracking marker  510  may be used, including at least one of an active infrared (IR) marker, an active light emitting diode (LED), and a graphical pattern. Important is that the medical navigation system  205  know the dimensions of the pointer tool  500  such that the precise position of the tip  502  relative to the tool tracking markers  510 , e.g., that the medical navigation system  205  sees the tool tracking markers  510  using the camera  307 , is known. If the shaft  504  becomes slightly bent or deformed, the relationship of the tip  502  relative to the tool tracking markers  510  may change, which can cause inaccuracies in medical procedures using the medical navigation system  205 , thereby becoming problematic. 
     Referring to  FIG. 6  and ahead to  FIGS. 7-13 , this diagram illustrates, in a perspective view, a trackable instrument, such as the pointer tool  500 , as shown in  FIG. 5 , being inserted into a calibration apparatus  600  for calibration thereby, in accordance with an embodiment of the present disclosure. 
     Referring to  FIG. 7 , this diagram illustrates, in a perspective view, the calibration apparatus  600 , as shown in  FIG. 6 . For simplicity, the calibration apparatus  600  will be referred to throughout as either the calibration apparatus  600  or a calibration block, although the calibration apparatus  600  need not necessary take the form of a block. Referring to  FIG. 8 , this diagram illustrates, in a front view, the calibration apparatus  600 , in accordance with an embodiment of the present disclosure. Referring to  FIG. 9 , this diagram illustrates, in a rear view, the calibration apparatus  600 , in accordance with an embodiment of the present disclosure. Referring to  FIG. 10 , this diagram illustrates, in a side view, the calibration apparatus  600 , in accordance with an embodiment of the present disclosure. Referring to  FIG. 11 , this diagram illustrates, in an opposing side view, the calibration apparatus  600 , in accordance with an embodiment of the present disclosure. Referring to  FIG. 12 , this diagram illustrates, in a top view, the calibration apparatus  600 , in accordance with an embodiment of the present disclosure. Referring to  FIG. 13 , this diagram illustrates, in a bottom view, the calibration apparatus  600 , in accordance with an embodiment of the present disclosure. 
     Still referring to  FIGS. 7-13 , together, the calibration block apparatus  600  may be used to calibrate a medical tool having a tool tracking marker, e.g., a trackable instrument, such as the pointer tool  500  having the tracking markers  510 . The medical tool and the calibration apparatus  600  are typically used in conjunction with a medical navigation system, such as the medical navigation system  205  that includes the control and processing unit  300 . The calibration apparatus  600  includes a frame  602 , at least one frame tracking marker  604  attached to the frame  602 , and a reference point feature  606  formed on the frame  602 . In one example, the reference point feature  606  comprises a divot that is of an appropriate shape for securely receiving the tip  502  of the pointer tool  500 . For the purposes of this example, the reference point  606  will be referred to throughout as the reference point feature  606  or the divot  606 ; however, any reference point feature or surface may be used to meet the design criteria of a particular application. The divot  606  may provide a known spatial reference point relative to the frame tracking markers  604 . For example, the medical navigation system  205  may have data saved therein, e.g., in data storage device  342 , so that the medical navigation system  205  knows the position in space of a floor of the divot  606  relative to the frame tracking markers  604  to a high degree of accuracy. In one example, a high degree of accuracy may refer to a tolerance of approximately 0.08 mm, but any suitable tolerance may be used according to the design criteria of a particular application. 
     Still referring to  FIGS. 7-13 , together, the calibration apparatus  600  has has four passive reflective tracking spheres, but any suitable number of frame tracking markers  604  may be used and any suitable type of frame tracking marker  604  may be used according to the design criteria of a particular application, including at least one of an active infrared (IR) marker, an active light emitting diode (LED), and or a graphical pattern. When passive reflective tracking spheres are used as the frame tracking markers  604 , typically at least three frame tracking markers  604  will be attached to a same side of the frame  602 . Likewise, when a trackable instrument, such as the pointer tool  500  having passive reflective tracking spheres, is used in conjunction with the calibration apparatus  600 , the medical instrument will typically have at least three tool tracking markers  510  attached thereto. 
     Still referring to  FIGS. 7-13 , together, the tip  502  of a trackable instrument, such as the pointer tool  500  having passive reflective tracking spheres, is insertable into the divot  606  to abut against a floor of the divot  606  for validation of the pointer tool  500  dimensions by the medical navigation system  205 . Since the medical navigation system  205  knows the precise dimensions of the calibration apparatus  600 , e.g., saved in data storage device  342 , the medical navigation system  205  knows the precise dimensions of the trackable instrument, such as the pointer tool  500  having passive reflective tracking spheres, that was previously registered. A deformed medical tool is re-registrable with the medical navigation system  205  such that the medical navigation system  205  learns the new dimensions of the deformed tool. In other words, when the pointer tool  500  is placed in the calibration apparatus  600 , as shown in  FIG. 6 , the position of the tip  502  of the pointer tool  500 , relative to the tracking markers  510 , that the medical navigation system  205  is seeing, e.g., by using the camera  307 , such position is known to the system  205 . 
     Still referring to  FIGS. 7-13 , together, likewise, the position of the floor of the divot  606  relative to the tracking markers  604  on the calibration apparatus  600  that the medical navigation system  205  is seeing, e.g., using the camera  307 , is known. The medical navigation system  205  has enough information to calculate to a designed tolerance the expected location of the frame tracking markers  604  on the calibration apparatus  600  relative to the tool tracking markers  510  on the pointer tool  500 . In one example, the designed tolerance may be a tolerance of approximately 1.0 mm, but any suitable tolerance may be used according to the design criteria of a particular application. When this expected location differs, in the vast majority of cases and assuming the structural integrity of the calibration apparatus  600 , the cause will be a bent or deformed shaft  504 . When this occurs, the medical navigation system  200  may simply learn the new dimensions of the deformed or bent medical tool, such as the pointer tool  500 , e.g., re-registration, and save this information, for example in the data storage device  342  (See also  FIG. 14 , showing a method for verifying, and, if necessary, re-registering a medical tool.). 
     Still referring to  FIGS. 7-13 , together, the calibration apparatus  600  has a front side  608 , a back side  610 , a right side  612 , a left side  614 , a top side  616 , and a bottom side  618 . The calibration apparatus  600  exists in three dimensional space having an X-axis, a Y-axis, and a Z-axis. In one example, where passive reflective tracking spheres are used, at least one of the four frame tracking markers  604  differs in position in the X direction from the remaining tracking markers  604 , at least one of the four frame tracking markers  604  differs in position in the Y direction from the remaining tracking markers  604 , and at least one of the four at least three frame tracking markers  604  differs in position in the Z direction from the remaining frame tracking markers  604 . This feature may provide the medical navigation system  205  with a better degree of accuracy to detect the position of the calibration apparatus  600  in 3D space. 
     Still referring to  FIGS. 7-13 , together, the calibration apparatus  600  further has a cavity  620  between the right side  612  and the left side  614  of the frame  602  and between the top side  616  and the bottom side  618  of the frame  602 . The cavity  620  may have a top side  622 , a bottom side  624 , a right side  626 , and a left side  628 . In one example, the divot  606  may be positioned on the bottom side  624  of the cavity  620 . The calibration apparatus  600  may further have a retaining orifice  630  positioned on a top side  616  of the frame  602  and extending through to the top side  622  of the cavity  620 . The retaining orifice  630  may receive the medical tool such as the pointer tool  500 , as the tip  502  of the tool  500  is positioned in the divot  606 . The retaining orifice  630  may serve to hold the pointer tool  500  in an upright position when the tip  502  of the pointer tool  500  rests in the divot  606 . 
     Still referring to  FIGS. 7-13 , together, the calibration apparatus  600  further comprises a second reference point feature  632 , which, in one example, comprises a second divot  632 , formed on the frame  602  for further validating the pointer tool  500  dimensions by the medical navigation system  200 . The second reference point feature  632  may not have an associated retaining orifice  630 , which allows the pointer tool  500  to move around in free space as a user holds the pointer tool  500  with the tip  502  firmly abutted against the floor of the divot  632 . This condition may allow the medical navigation system  200  to perform an even increased level of analysis on the pointer tool  500  as the pointer tool  500  moves about in 3D space with the tip  502  firmly planted in the divot  632 , thereby allowing the medical navigation system  205  to detect multiple positions of the frame tracking markers  604  and to generate many different equations for the spatial position of the tip  502  relative to the frame markers  604 , and thereby allowing for an error minimization method, comprising an algorithm, to be executed. 
     Still referring to  FIGS. 7-13 , together, in one example, the calibration apparatus  600  comprises at least one material, such as stainless steel, aluminum, any other suitable metal, and any other suitable alloy. Alternatively, the calibration apparatus  600  comprises at least one material, such as plastic, a polymer, and any other synthetic material of a suitable weight and rigidity. The calibration apparatus  600  is fabricable using yet to be developed or known manufacturing techniques such as injected molding, machine tooling, and 3D printing. While some examples of suitable materials and manufacturing techniques are provided for the calibration apparatus  600 , any suitable material and manufacturing technique is useable according to criteria for a particular application. 
     Referring to  FIG. 14 , this flow diagram illustrates a method  1400  for verifying and re-registering a medical tool, such as a tracked instrument, e.g., the pointer tool  500  or a medical instruments  360 , in accordance with an embodiment of the present disclosure. The method  1400  may be executed by the medical navigation system  205  either as a precursor to the method  400 , as shown in  FIG. 4 , or during the method  400 , as shown in  FIG. 4 , if it becomes apparent to the surgeon performing the medical procedure that the dimensions of the pointer tool  500  may have changed. Performing the method  1400 , for example, comprises starting via executing the tool verification and re-registration process by providing appropriate input to the control and processing unit  300 , for example by way of the external I/O devices  344 , e.g., by the surgeon  201  or operator  203  or by an automated electronic system, as indicated by block  1402 . At this point, the surgeon  201  may ensure that the tracked instrument or the pointer tool  500  is disposed in the calibration apparatus  600  and that both the tracked instrument or the pointer tool  500  and the calibration apparatus  600  are clearly visible by the appropriate sensors, such as the camera  307  in the case of optical tracking markers, used by the control and processing unit  300 . 
     Still referring to  FIG. 14 , the method  1400  further comprises detecting the tracking markers of the pointer tool  500  and the calibration block  600  by the control and processing unit  300  via the sensors, as indicated by block  1404 . In the example of passive reflective tracking markers, the camera  307  may provide input to the processor  300 , which detects the locations of the tool tracking markers  510  and the frame tracking markers  604 . Next, the method  1400  further comprises calculating the spatial relationship of the tool tracking markers  510  on the pointer tool  500  relative to the frame tracking markers  604  on the calibration apparatus  600  by the control and processing unit  300 , as indicated by block  1406 . Calculating the expected acceptable range of locations of the tracking markers  604  relative to the tool tracking markers  510  comprises calculating the expected acceptable range of locations by way of the control and processing unit  300  processing data obtained relating to the expected dimensions of the pointer tool  500 , e.g., the location of the tip  502  relative to the tool tracking markers  510 , and data obtained relating to the dimensions of the calibration block  600 , e.g., the location of the floor of the reference point feature  606  relative to the frame tracking markers  604 . 
     Still referring to  FIG. 14 , the method  1400  further comprises assessing the relative positions of the frame tracking markers  604  to the tool tracking markers  510 , as indicated by block  1408 . If it is determined that the dimensions of the pointer tool  500  have changed, such as from a bending or deformation of the shaft  504 , the method  1400  further comprises relearning the dimensions of the pointer tool  500  and re-registering the pointer tool  500  by the control and processing unit  300 , as indicated by block  1410 . The method  1400  further comprises terminating the medical procedure, as indicated by block  1412 . If it is determined at block  1408  that the dimensions of the medical tool  500  have not changed beyond a specified threshold, then the dimensions of the medical tool  500  have been verified and the method  1400  ends, as indicated by block  1412 , without re-registering the pointer tool  500 . In one example, the threshold comprises a range of approximately 0.3 mm to approximately 1 mm, depending on the needs for a particular application; however, the method  1400  is performable with any suitable tolerance. 
     Referring to  FIGS. 15A, 15B, and 15C , together, in  FIG. 15A , this diagram illustrates, in a cutaway perspective view, a calibration body  603  of a calibration apparatus  600 ′ ( FIG. 19A-20D ), operable with a medical navigation system  205 , for calibrating a medical device having a tip, such as a pointer tool  500 , in accordance with an embodiment of the present disclosure. Referring to  FIG. 15B , this diagram illustrates, in an alternate cutaway perspective view, a calibration body  603  of a calibration apparatus  600 ′ ( FIGS. 19A-20D ), as shown in  FIG. 15A , operable with a medical navigation system  205 , for calibrating a medical device having a tip, such as a pointer tool  500 , in accordance with an embodiment of the present disclosure. Referring to  FIG. 15C , this diagram illustrates, in a perspective view, a calibration body  603  of a calibration apparatus  600 ′ ( FIGS. 19A-20D ), as shown in  FIG. 15A , operable with a medical navigation system  205 , for calibrating a medical device having a tip, such as a pointer tool  500 , in accordance with an embodiment of the present disclosure. 
     Referring to  FIGS. 16A and 16B , together, in  FIG. 16A , this diagram illustrates, in a perspective view, a calibration body  603  of an alternative calibration apparatus, operable with a medical navigation system  205 , for calibrating a medical device having a tip, such as a pointer tool  500  having a tip  502 , in accordance with an embodiment of the present disclosure. Referring to  FIG. 16B , this diagram illustrates, in a cutaway perspective view, a calibration body  603  of the alternative calibration apparatus, as shown in  FIG. 16A , operable with a medical navigation system  205 , for calibrating a medical device having a tip, such as the pointer tool  500  having the tip  502 , in accordance with an embodiment of the present disclosure. 
     Referring to  FIGS. 17A and 17B , together, in  FIG. 17A , this diagram illustrates, in a perspective view, a calibration body  603  of another alternative calibration apparatus, operable with a medical navigation system  205 , for calibrating a medical device having a tip, such as the pointer tool  500  having the tip  502 , in accordance with an embodiment of the present disclosure. Referring to  FIG. 17B , this diagram illustrates, in a cutaway top perspective view, a calibration body  603  of the other alternative calibration apparatus, as shown in  FIG. 17A , operable with a medical navigation system  205  for calibrating a medical device having a tip, such as the pointer tool  500  having the tip  502 , in accordance with an embodiment of the present disclosure. 
     Referring to  FIG. 18  and, ahead, to  FIGS. 19A through 19E , together, this diagram illustrates, in a perspective view, a calibration apparatus  600 ′, operable with a medical navigation system  205 , for calibrating a medical device having a tip, such as the pointer tool  500  having the tip  502 , wherein the pointer tool  500  is inserted into the calibration apparatus  600 ′, in accordance with an embodiment of the present disclosure. The calibration apparatus  600 ′ comprises: a calibration body  603  configured to accommodate a plurality of tool dimensions and having a plurality of cooperating spring-loaded cams  605  for accommodating a plurality of tool cross-sectional dimensions; a frame  602  configured to couple with the calibration body  603  and having at least one frame tracking marker  604  coupled therewith; and a reference point feature  606  ( FIGS. 7-9 ) coupled with the calibration body  603 , the reference point feature  606  ( FIGS. 7-9 ) providing a known spatial reference point relative to the at least one frame tracking marker  604 . 
     Still referring to  FIG. 18  and ahead to  FIGS. 19A through 19E , together, the at least one frame tracking marker  604  comprises at least one of a passive reflective tracking sphere, an active infrared marker, an active light emitting diode, and a graphical pattern. The at least one frame tracking marker  604  comprises at least three frame tracking markers  604 , and preferably at least four frame tracking markers  604 , disposed in relation to a same side of the frame  602 . The calibration apparatus  600 ′ further comprises at least one tool tracking marker  510 . The reference point feature  606  ( FIGS. 7-9 ) comprises a divot (not shown). The at least one tool tracking marker  510  is coupled with the medical tool, such as a pointer tool  500 . The divot comprises a floor and is configured to accept the tip  502  for validating at least one dimension of the medical tool by the medical navigation system  205 . 
     Still referring to  FIG. 18  and ahead to  FIGS. 19A through 19E , together, the at least one frame tracking marker  604  comprises at least four frame tracking markers  604 ; and the at least one tool tracking marker  510  comprises at least four tracking markers  510 , whereby the medical navigation system  205  is reconfigurable if the medical tool, e.g., the pointer tool  500 , is deformed by re-registration with at least one new dimension in relation to the medical tool, in accordance with an embodiment of the present disclosure. The frame  602  comprises a front side, a back side, a right side  612 , a left side  614 , a top side  616 , and a bottom side  618 ; and the frame  602  comprises at least four frame tracking markers  604  disposed in relation to a same side thereof. Alternatively, three frame tracking markers  604  may be used. 
     Still referring to  FIG. 18  and ahead to  FIGS. 19A through 19E , together, the calibration body  603  is definable in relation to a three-dimensional space having an X-axis, a Y-axis, and a Z-axis, wherein at least one frame tracking marker  604  of the at least four frame tracking markers  604  differs in an X-direction position from the remaining tracking markers  604  thereof, wherein at least one frame tracking marker  604  of the at least four frame tracking markers  604  differs in a Y-direction position from the remaining tracking markers  604  thereof, and wherein at least one frame tracking marker  604  of the at least four frame tracking markers  604  differs in a Z-direction position from the remaining tracking markers  604  thereof. 
     Still referring to  FIG. 18  and ahead to  FIGS. 19A through 19E , together, the calibration body  603  forms a cavity for accommodating the plurality of cooperating spring-loaded cams  605 . The reference point feature  606  ( FIGS. 7-9 ) is disposed in relation to the bottom side of the cavity. The calibration body  603  further forms an orifice  630 ′ disposed on a top side of the calibration body  603  and extending through to the top side of the cavity, the orifice  630 ′ configured to receive the medical tool, e.g., the pointer tool  500 , as the tip  502  thereof is disposed in the reference point feature  606  ( FIGS. 7-9 ), and the orifice  630 ′ retaining the medical tool, e.g., the pointer tool  500 , in an upright position when the tip  502  thereof rests in the reference point feature  606  ( FIGS. 7-9 ). The reference point feature  606  alternatively comprises a flat surface disposed in relation to a removable base, wherein a centerline is defined by a plurality of cams. 
     Referring to  FIGS. 19A through 19D , together, in  FIG. 19A , this diagram illustrates, in a perspective view of a calibration apparatus  600 ′, operable with a medical navigation system  205 , for calibrating a medical device having a tip, such as a pointer tool  500  and a suction instrument, by examples only, in accordance with an embodiment of the present disclosure. Referring to  FIG. 19B , this diagram illustrates, in a cutaway perspective view, a calibration apparatus  600 ′, as shown in  FIG. 19A , in accordance with an embodiment of the present disclosure. Referring to  FIG. 19C , this diagram illustrates, in an alternate perspective view, a calibration apparatus  600 ′, operable with a medical navigation system, for calibrating a medical device having a tip, in accordance with an embodiment of the present disclosure. Referring to  FIG. 19D , this diagram illustrates, in an alternate cutaway perspective view, a calibration apparatus  600 ′, as shown in  FIG. 19C , in accordance with an embodiment of the present disclosure. 
     Referring to  FIG. 19E  and referring back to  FIGS. 19A  though  19 D, this diagram illustrates, in an exploded perspective view, a calibration apparatus  600 ′, operable with a medical navigation system  205 , for calibrating a medical device having a tip  502 , in accordance with an embodiment of the present disclosure. The apparatus  600 ′ further comprises an upper torque spring  603   i  configured to operationally couple with the actuator  603   a  with the upper cam wheel  605   a  and a lower torque spring  603   i  configured to operationally couple with the actuator  603   a  with the lower cam wheel  605   b . The upper cam wheel  605   a  is retained by the upper holder ring  603   u . The lower cam wheel  605   b  is retained by the lower holder ring  6031 . The calibration apparatus  600 ′ comprises an upper adjustable retainer  610   u , the upper adjustable retainer  610   u  comprising a plurality of cams or a plurality of cooperating cams  605 , the upper adjustable retainer  610   u  actuable by way of the upper cam wheel  605   a . The calibration apparatus  600 ′ comprises a mid-body  611  for facilitating gripping, the mid-body  611  configured to couple with the actuator  603   a . The calibration apparatus  600 ′ comprises a base or lower portion  603   e , base or lower portion  603   e  having at least one gripping feature (not shown), such as knurling, indentations, channels, and the like ( FIG. 33 ). The base or lower portion  603   e  configured to couple with the frame  602 , e.g., via the frame coupling arm  602   a . The calibration apparatus  600 ′ comprises an upper enclosure  613   u  and a lower enclosure  6131 , respectively accommodating the upper adjustable retainer  610   u  the lower adjustable retainer  6101 . Fasteners  603   f  facilitate assembling and disassembling components of the calibration body  603 . 
     Referring to  FIG. 20A  and ahead to  FIGS. 20B through 20H , together, this diagram illustrates, in a perspective view, a calibration apparatus  600 ′, operable with a medical navigation system  205 , for calibrating a medical device having a tip, such as a pointer tool  500 , in accordance with an embodiment of the present disclosure. Referring to  FIG. 20B , this diagram illustrates, in an alternate perspective view, of a calibration apparatus  600 ′, as shown in  FIG. 20A , in accordance with an embodiment of the present disclosure. Referring to  FIG. 20C , this diagram illustrates, in a top view of a calibration apparatus  600 ′, as shown in  FIG. 20A , in accordance with an embodiment of the present disclosure. Referring to  FIG. 20D , this diagram illustrates, in a bottom view, a calibration apparatus  600 ′, as shown in  FIG. 20A , in accordance with an embodiment of the present disclosure. Referring to  FIG. 20E , this diagram illustrates, in a side view, a calibration apparatus  600 ′, as shown in  FIG. 20A , in accordance with an embodiment of the present disclosure. Referring to  FIG. 20F , this diagram illustrates, in an opposing side view, a calibration apparatus  600 ′, as shown in  FIG. 20A , in accordance with an embodiment of the present disclosure. Referring to  FIG. 20G , this diagram illustrates, in a front view, a calibration apparatus  600 ′, as shown in  FIG. 20A , in accordance with an embodiment of the present disclosure. Referring to  FIG. 20H , this diagram illustrates, in a rear view, a calibration apparatus  600 ′, as shown in  FIG. 20A , in accordance with an embodiment of the present disclosure. 
     Referring to  FIG. 21 , this flow diagram illustrates a method M 1  of fabricating a calibration apparatus  600 ′, operable with a medical navigation system  205 , for calibrating a medical device having a tip, such as a pointer device  500 , in accordance with an embodiment of the present disclosure. The method M 1  comprises: providing a calibration body configured to accommodate a plurality of tool dimensions and having a plurality of cooperating spring-loaded cams for accommodating a plurality of tool cross-sectional dimensions, as indicated by block  2101 ; providing a frame couple-able with the calibration body and having at least one frame tracking marker coupled therewith, as indicated by block  2102 ; and providing a reference point feature coupled with the calibration body, the reference point feature providing a known spatial reference point relative to the at least one frame tracking marker, as indicated by block  2103 . 
     Referring to  FIG. 22 , this flow diagram illustrates a method M 2  of calibrating a medical device having a tip, such as a pointer tool  500 , by way of a calibration apparatus  600 ′, operable with a medical navigation system  205 , in accordance with an embodiment of the present disclosure. The method M 2  comprises: providing the calibration apparatus, as indicated by block  2200 , providing the calibration apparatus  600 ′ comprising: providing a calibration body configured to accommodate a plurality of tool dimensions and having a plurality of cooperating spring-loaded cams for accommodating a plurality of tool cross-sectional dimensions, as indicated by block  2201 ; providing a frame couple-able with the calibration body and having at least one frame tracking marker coupled therewith, as indicated by block  2202 ; and providing a reference point feature coupled with the calibration body, the reference point feature providing a known spatial reference point relative to the at least one frame tracking marker, as indicated by block  2203 ; detecting the at least one tool tracking marker, e.g., at least three tool tracking markers, and the at least one frame tracking marker, e.g., at least four frame tracking markers, as indicated by block  2204 ; calculating an expected spatial relationship of the at least one tool tracking marker relative to the at least one frame tracking marker, as indicated by block  2205 , thereby saving the expected spatial relationship, and thereby completing calibration of the tool; and re-calibrating the tool if at least one tool dimension of the medical tool is altered beyond a threshold value in relation to the expected spatial relationship, as indicated by block  2206 . Prior to the step of re-calibrating the tool, the method M 2  further comprises confirming calibration (not shown) by removing the tool needs from the orifice  630 ′; disposing the tool tip in a verification divot, e.g., the divot  632  ( FIG. 12 ), by example only; and calculating an expected spatial relationship between the tool and the verification divot. 
     Referring to  FIG. 23 , this diagram illustrates, in a perspective view, a calibration apparatus  600 ″, operable with a medical navigation system  205 , for calibrating a medical tool having a tip, such as a pointer tool  500 , comprises: a calibration body  603  configured to accommodate a plurality of tool dimensions and having a cam wheel, e.g., an upper cam wheel  605   a , with a plurality of cooperating spring-loaded cams  605  for accommodating a plurality of tool cross-sectional dimensions; a frame  602  configured to couple with the calibration body  603 , such as by way of a holder arm  602   a , and having at least one tracking marker fitting  604   a  for coupling at least one frame tracking marker  604  ( FIGS. 31-33 ) coupled therewith; and a reference point feature  606  ( FIG. 33 ) coupled with the calibration body  603 , the reference point feature  606  ( FIG. 33 ) providing a known spatial reference point relative to the at least one tracking marker fitting  604   a  for coupling at least one frame tracking marker  604 , e.g., at least four frame tracking markers  604 , in accordance with an embodiment of the present disclosure. 
     Still referring to  FIG. 23 , the at least one frame tracking marker  604  comprises at least one of a passive reflective tracking sphere, an active infrared marker, an active light emitting diode, or a graphical pattern. The at least one frame tracking marker  604  comprises at least four frame tracking markers  604  disposed in relation to a same side of the frame  602 . The calibration apparatus  600 ″ further comprises at least one tool tracking marker  510 , e.g., at least three tool tracking markers  510 , for use with the medical device having a tip  502 , such as a tracked instrument, e.g., a pointer device  500 . The reference point feature  606  comprises a divot ( FIG. 33 ). The at least one tool tracking marker  510  is coupled with the medical tool, such as a pointer tool  500 . The reference point feature  606  ( FIG. 33 ), comprising a divot, has a floor and is configured to accept the tip  502  for validating at least one dimension of the medical tool by the medical navigation system  205 . 
     Still referring to  FIG. 23 , the at least one tracking marker fitting  604   a  is configured to couple at least one frame tracking marker  604 , e.g., a at least four frame tracking markers  604  ( FIG. 33 ); and the at least one tool tracking marker  510  ( FIG. 18 ) comprises at least four tracking markers  510  ( FIG. 18 ), whereby the medical navigation system  205  is reconfigurable if the medical tool, e.g., the pointer tool  500 , is deformed by re-registration with at least one new dimension in relation to the medical tool, in accordance with an embodiment of the present disclosure. The frame  602  comprises a front side  602   b , a back side  602   c  ( FIG. 24 ), a right side  612 , a left side  614 , a top side  616 , and a bottom side  618  ( FIG. 24 ); and the frame  602  comprises at least four tracking marker fittings  604   a  for coupling at least four frame tracking markers  604  ( FIG. 33 ) disposed in relation to a same side thereof. 
     Still referring to  FIG. 23  and referring ahead to  FIG. 33 , the calibration body  603  is definable in relation to a three-dimensional space having an X-axis, a Y-axis, and a Z-axis, wherein at least one frame tracking marker  604  of the at least four frame tracking markers  604  differs in an X-direction position from the remaining tracking markers  604  thereof, wherein at least one frame tracking marker  604  of the at least four frame tracking markers  604  differs in a Y-direction position from the remaining tracking markers  604  thereof, and wherein at least one frame tracking marker  604  of the at least four frame tracking markers  604  differs in a Z-direction position from the remaining tracking markers  604  thereof. 
     Still referring to  FIG. 23 , the calibration body  603  forms a cavity for accommodating the plurality of cooperating spring-loaded cams  605  ( FIG. 33 ). The reference point feature  606  is disposed in relation to the bottom side of the cavity ( FIG. 33 ). The calibration body  603  further forms an orifice  630 ′ disposed on a top side of the calibration body  603  and extending through to the top side of the cavity, the orifice  630 ′ configured to receive the medical tool, e.g., the pointer tool  500 , as the tip  502  thereof is disposed in the reference point feature  606 , and the orifice  630 ′ retaining the medical tool, e.g., the pointer tool  500 , in an upright position when the tip  502  thereof rests in the reference point feature  606  ( FIGS. 7-9  and  FIG. 33 ). The calibration body  603  comprises an actuator  603   a  for actuating the plurality of cooperating spring-loaded cams  605  from a cam wheel  605   a  ( FIGS. 29 and 33 ), wherein depressing the actuator  603   a  opens the plurality of cooperating spring-loaded cams  605  from the cam wheel  605   a  in relation to the medical tool, and wherein releasing the actuator  603   a  closes the plurality of cooperating spring-loaded cams  605  from the cam wheel  605   a  in relation to the medical tool. 
     Referring to  FIG. 24 , this diagram illustrates, in a rearward perspective view, a calibration apparatus  600 ″, operable with a medical navigation system  205 , for calibrating a medical device, e.g., the pointer tool  500 , having a tip  502 , in accordance with an embodiment of the present disclosure. The calibration body  603  comprises a “locked” indicium  603   b , such as a “lock in a closed position” representation, for indicating that the calibration apparatus  600 ″ is in a “locked” position; and an “unlocked” indicium  603   c  ( FIG. 25 ), such as a “lock in an open position” representation, for indicating that the calibration apparatus  600 ″ is in an “unlocked” position. The calibration body  603  comprises a lower portion  603   e , the lower portion  603   e  comprising an indicium  603   d , such as an “arrow” representation, which cooperates with either the indicium  603   b  or the indicium  603   c  ( FIG. 25 ) for indicating the respective positions. The lower portion  603   e  is a removable base which can be removed by a user to allow for cleaning through the center axis of the calibration body  603 . The lower portion  603   e  is separately storable from the remaining components of the calibration apparatus  600 ″; and may be assembled by aligning an indicium  603   d  with an indicium  603   c  and rotating the lower portion  603   e  until the indicium  603   d  aligns with the indicium  603   b.    
     Referring to  FIG. 25 , this diagram illustrates, in a rear view, a calibration apparatus  600 ″, operable with a medical navigation system  205 , for calibrating a medical device having a tip  502 , in accordance with an embodiment of the present disclosure. In this example, the lower portion  603   e  is a removable base which can be removed by a user to allow for cleaning through the center axis of the calibration body  603 . The lower portion  603   e  is separately storable from the remaining components of the calibration apparatus  600 ″; and may be assembled by aligning an indicium  603   d  with an indicium  603   c  and rotating the lower portion  603   e  until the indicium  603   d  aligns with the indicium  603   b.    
     Referring to  FIG. 26 , this diagram illustrates, in a side view, a calibration apparatus  600 ″, operable with a medical navigation system  205 , for calibrating a medical device having a tip  502 , in accordance with an embodiment of the present disclosure. In this example, the lower portion  603   e  is a removable base which can be removed by a user to allow for cleaning through the center axis of the calibration body  603 . The lower portion  603   e  is separately storable from the remaining components of the calibration apparatus  600 ″; and may be assembled by aligning an indicium  603   d  with an indicium  603   c  and rotating the lower portion  603   e  until the indicium  603   d  aligns with the indicium  603   b.    
     Referring to  FIG. 27 , this diagram illustrates, in an opposing side view, a calibration apparatus  600 ″, operable with a medical navigation system  205 , for calibrating a medical device having a tip  502 , in accordance with an embodiment of the present disclosure. In this example, the lower portion  603   e  is a removable base which can be removed by a user to allow for cleaning through the center axis of the calibration body  603 . The lower portion  603   e  is separately storable from the remaining components of the calibration apparatus  600 ″; and may be assembled by aligning an indicium  603   d  with an indicium  603   c  and rotating the lower portion  603   e  until the indicium  603   d  aligns with the indicium  603   b.    
     Referring to  FIG. 28 , this diagram illustrates, in a front view, a calibration apparatus  600 ″, operable with a medical navigation system  205 , for calibrating a medical device having a tip  502 , in accordance with an embodiment of the present disclosure. The frame  602  comprises a front side  602   b , a back side  602   c  ( FIG. 24 ), a right side  612 , a left side  614 , a top side  616 , and a bottom side  618 ); and the frame  602  comprises at least four frame tracking markers  604  ( FIG. 33 ) disposed in relation to a same side thereof. In this embodiment, the frame  602  is asymmetric, by example only, for facilitating recognizing position and orientation of the tool by a camera (if the markers are arranged in a square shape, the system  205  would have difficulty determining from which side of the four sides that the tool tip protrudes). 
     Referring to  FIG. 29 , this diagram illustrates, in a top view, a calibration apparatus  600 ″, operable with a medical navigation system  205 , for calibrating a medical device having a tip  502 , in accordance with an embodiment of the present disclosure. The frame  602  comprises at least one tracking marker fitting  604   a  for coupling the at least one tracking marker  604  ( FIG. 33 ). The tip  502  of the medical device is insertable into the orifice  630 ′, through the calibration body  603  and into the feature  606  ( FIG. 33 ). The calibration body  603  further comprises an upper cam wheel  605   a  from which a plurality of cams  605  ( FIG. 24 ) are deployable and an upper holder ring  603   u  ( FIG. 33 ). The upper holder ring  603   u  has at least one tap hole  603   h  ( FIG. 33 ) for accommodating at least one fastener  603   f.    
     Referring to  FIG. 30 , this diagram illustrates, in a bottom view, a calibration apparatus  600 ″, operable with a medical navigation system  205 , for calibrating a medical device having a tip  502 , in accordance with an embodiment of the present disclosure. The calibration body  603  further comprises a lower cam wheel  605   b  from which a plurality of cams  605  ( FIG. 29 ) are deployable and a lower holder ring  6031 . The lower holder ring  6031  has at least one tap hole  603   h  ( FIG. 29 ) for accommodating at least one fastener  603   f.    
     Referring to  FIG. 31 , this diagram illustrates, in an alternate frontal perspective view, a calibration apparatus  600 ″, operable with a medical navigation system  205 , for calibrating a medical device having a tip  502 , wherein the upper holder ring  603   u  ( FIG. 33 ) is removed to show internal components, in accordance with an embodiment of the present disclosure. 
     Referring to  FIG. 32 , this diagram illustrates, in an alternate rearward perspective view, a calibration apparatus  600 ″, operable with a medical navigation system  205 , for calibrating a medical device having a tip  502 , wherein the upper holder ring  603   u  ( FIG. 33 ) is removed to show internal components, in accordance with an embodiment of the present disclosure. 
     Referring to  FIG. 33 , this diagram illustrates, in an exploded frontal perspective view, a calibration apparatus  600 ″, operable with a medical navigation system  205 , for calibrating a medical device having a tip  502 , in accordance with an embodiment of the present disclosure. The apparatus  600 ″ further comprises an upper torque spring  603   i  configured to operationally couple with the actuator  603   a  with the upper cam wheel  605   a  and a lower torque spring  603   i  configured to operationally couple with the actuator  603   a  with the lower cam wheel  605   b . The upper cam wheel  605   a  is retained by the upper holder ring  603   u . The lower cam wheel  605   b  is retained by the lower holder ring  6031 . The calibration apparatus  600 ″ comprises an upper adjustable retainer  610   u , the upper adjustable retainer  610   u  comprising a plurality of cams or a plurality of cooperating cams, the upper adjustable retainer  610   u  actuable by way of the upper cam wheel  605   a , and a lower adjustable retainer  6101 , the lower adjustable retainer  6101  also comprising a plurality of cams or a plurality of cooperating cams, the lower adjustable retainer  6101  actuable by way of the lower cam wheel  605   b . The calibration apparatus  600 ″ comprises a mid-body  611  for facilitating gripping, the mid-body  611  configured to couple with the actuator  603   a  and the frame  602 , e.g., via the frame coupling arm  602   a . The calibration apparatus  600 ″ comprises a base or lower portion  603   e , base or lower portion  603   e  having at least one gripping feature  612 , such as knurling, indentations, channels, and the like. The calibration apparatus  600 ″ comprises an upper enclosure  613   u  and a lower enclosure  6131 , respectively accommodating the upper adjustable retainer  610   u  the lower adjustable retainer  6101 . Fasteners  603   f  facilitate assembling and disassembling components of the calibration body  603 . The at least one fastener  603   f  may comprises a threaded fastener, such as a screw and a bolt. At least one tap hole  603   h  accommodates the at least one fastener  603   f . The at least one tap hole  603   h  may comprise threading, e.g., screw-threading, for engaging the at least one fastener  603   f.    
     Referring to  FIG. 34 , this flow diagram illustrates a method M 3  of fabricating a calibration apparatus  600 ″, as shown in  FIG. 23 , operable with a medical navigation system  205 , for calibrating a medical tool having a tip  502 , comprises: providing a calibration body  603  configured to accommodate a plurality of tool dimensions and having at least one cam wheel with a plurality of cooperating spring-loaded cams  605  for accommodating a plurality of tool cross-sectional dimensions, as indicated by block  3401 ; providing a frame  602  configured to couple with the calibration body  603  and having at least one frame tracking marker  604  coupled therewith, as indicated by block  3402 ; and providing a reference point feature  606  coupled with the calibration body  603 , the reference point feature  606  providing a known spatial reference point relative to the at least one frame tracking marker  604 , as indicated by block  3403 , in accordance with an embodiment of the present disclosure. 
     Referring to  FIG. 35 , in an embodiment of the present disclosure, a method M 4  of calibrating a medical tool, having a tip  502 , by way of a calibration apparatus  600 ″, as shown in  FIG. 23 , operable with a medical navigation system  205 , comprises: providing the calibration apparatus  600 ″, as indicated by block  4000 , providing the calibration apparatus  600 ″ comprising: providing a calibration body  603  configured to accommodate a plurality of tool dimensions and having at least one cam wheel with a plurality of cooperating spring-loaded cams for accommodating a plurality of tool cross-sectional dimensions, as indicated by block  3401 ; providing a frame configured to couple with the calibration body and having at least one frame tracking marker, e.g., at least four frame tracking markers, coupled therewith, as indicated by block  3402 ; and providing a reference point feature coupled with the calibration body, the reference point feature providing a known spatial reference point relative to the at least one frame tracking marker, as indicated by block  3403 ; detecting at least one tool tracking marker, e.g., at least three tool tracking markers, and the at least one frame tracking marker, as indicated by block  4001 ; calculating an expected spatial relationship of the at least one tool tracking marker relative to the at least one frame tracking marker, as indicated by block  4002 ; and re-calibrating the tool if at least one tool dimension of the medical tool is altered beyond a threshold value in relation to the expected spatial relationship, as indicated by block  4003 . Prior to the step of re-calibrating the tool, the method M 2  further comprises confirming calibration (not shown) by removing the tool needs from the orifice  630 ′; disposing the tool tip in a verification divot, e.g., the divot  632  ( FIG. 12 ), by example only; and calculating an expected spatial relationship between the tool and the verification divot. 
     While the present disclosure describes various embodiments for illustrative purposes, such description is not intended to be limited to such embodiments. On the contrary, the applicant&#39;s teachings described and illustrated herein encompass various alternatives, modifications, and equivalents, without departing from the embodiments, the general scope of which is defined in the appended claims. Except to the extent necessary or inherent in the processes themselves, no particular order to steps or stages of methods or processes described in this disclosure is intended or implied. In many cases the order of process steps may be varied without changing the purpose, effect, or import of the methods described. 
     Information as herein shown and described in detail is fully capable of attaining the above-described object of the present disclosure, the presently preferred embodiment of the present disclosure, and is, thus, representative of the subject matter which is broadly contemplated by the present disclosure. The scope of the present disclosure fully encompasses other embodiments which may become obvious to those skilled in the art, and is to be limited, accordingly, by nothing other than the appended claims, wherein any reference to an element being made in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural and functional equivalents to the elements of the above-described preferred embodiment and additional embodiments as regarded by those of ordinary skill in the art are hereby expressly incorporated by reference and are intended to be encompassed by the present claims. 
     Moreover, no requirement exists for a system or method to address each and every problem sought to be resolved by the present disclosure, for such to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. However, that various changes and modifications in form, material, work-piece, and fabrication material detail may be made, without departing from the spirit and scope of the present disclosure, as set forth in the appended claims, as may be apparent to those of ordinary skill in the art, are also encompassed by the present disclosure. 
     INDUSTRIAL APPLICABILITY 
     The subject matter of the present disclosure industrially applies to the field of calibration apparatuses. More particularly, the subject matter of the present disclosure industrially applies to the field of calibration apparatuses for surgical tools. Even more particularly, the subject matter of the present disclosure industrially applies to the field of calibration apparatuses for surgical tools in relation to image guided medical procedures with surgical navigation.