Method and system for performing a scan of an object

A method for generating an image of an object using a scanning system includes performing a first portion of a scan in a first scanning mode to acquire a first dataset, receiving a halt command for a conveyor within the scanning system, decelerating the conveyor to a halt based on the halt command using a conveyor controller, and, when the object is present within an examination region after the conveyor has halted, performing a second portion of the scan in a second scanning mode to acquire a second dataset. The second scanning mode is different than the first scanning mode. The method also includes reconstructing the first dataset using a first reconstruction algorithm and reconstructing the second dataset using a second reconstruction algorithm. The second reconstruction algorithm is different than the first reconstruction algorithm. The image is generated using the first reconstructed dataset and the second reconstructed dataset.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The embodiments described herein relate generally to a scanning system for scanning a stream of objects and, more particularly, to a scanning system for scanning a stream of objects that halts and resumes motion.

2. Description of the Related Art

At least some known scanning systems use a computer tomography (CT) system as an imaging section of the scanning system to scan a stream of objects. At least some known volumetric CT systems use helical scan protocols. However, proper image reconstruction using a helical scan protocol with a stream of objects generally requires that objects being scanned move at a constant velocity through the CT system. In at least some applications, for example, in scanning of airline luggage, it may become necessary to halt the stream of objects while being conveyed through the CT system. Such halting is also referred to as “die-back.” After a time period, the scanning of the stream of objects resumes. However, during the halting of the stream of objects, and subsequent acceleration from the halt, the constant speed assumption used for image reconstruction under the helical scan protocol is violated. Accordingly, during halting and acceleration conditions, at least some known CT systems are unable to scan and reconstruct an object within the stream of objects properly.

One known scanning system that includes a CT system does not scan a stream of objects and, as such, does not require the constant velocity assumption to reconstruct images of each object. Accordingly, halting the stream of objects within the scanning system does not adversely affect image reconstruction. However, when a stream of objects is not scanned, throughput of the scanning system may be reduced. Another known scanning system that includes a CT system generates three-dimensional images by scanning a stream of objects. In such a scanning system, when the stream of objects is halted, data acquired regarding an object within the CT system is discarded and the entire object is manually inspected. However, manually inspecting objects may be time consuming and costly.

Accordingly, there is a need for a scanning system that can scan a stream of objects and reconstruct an image of an object within the stream even if the stream of objects is halted and accelerated while the object is within an imaging section of the scanning system and a scan is being performed.

BRIEF SUMMARY OF THE INVENTION

In one aspect, a method for generating an image of an object using a scanning system is provided. The method includes performing a first portion of a scan in a first scanning mode to acquire a first dataset using a scan controller, receiving a halt command for a conveyor within the scanning system at at least a conveyor controller, decelerating the conveyor to a halt based on the halt command using the conveyor controller, and, when the object is present within an examination region after the conveyor has halted, performing a second portion of the scan in a second scanning mode to acquire a second dataset using the scan controller. The second scanning mode is different than the first scanning mode. The method also includes reconstructing the first dataset using a first reconstruction algorithm within a control system and reconstructing the second dataset using a second reconstruction algorithm within the control system. The second reconstruction algorithm is different than the first reconstruction algorithm. The image is generated by the control system using the first reconstructed dataset and the second reconstructed dataset.

In another aspect, a scanning system is provided. The scanning system includes a conveyor configured to convey a stream of objects through the scanning system, a conveyor controller in operative control communication with the conveyor, a computer tomography (CT) system, a scan controller in operative control communication with the CT system, and a control system in communication with the conveyor controller and the scan controller. The control system is configured to perform a first portion of a scan in a first scanning mode to acquire a first dataset using the scan controller, issue a halt command to at least the conveyor controller, decelerate the conveyor to a halt based on the halt command using the conveyor controller, and, when an object is present within an examination region after the conveyor has halted, perform a second portion of the scan in a second scanning mode to acquire a second dataset using the scan controller. The second scanning mode is different than the first scanning mode. The control system is also configured to reconstruct the first dataset using a first reconstruction algorithm and reconstruct the second dataset using a second reconstruction algorithm. The second reconstruction algorithm is different than the first reconstruction algorithm. An image is generated using the first reconstructed dataset and the second reconstructed dataset.

The embodiments described herein scan a stream of objects and reconstruct an image of an object within the stream even if the stream of objects is halted and accelerated while the object is within an imaging section of the scanning system and a scan is being performed. Further, data acquired prior to the halt is used to reconstruct the image of the object rather than discarded.

DETAILED DESCRIPTION OF THE INVENTION

In order to accurately inspect and reconstruct an image of an object within an imaging section of a scanning system when a halt/dieback situation occurs, a method of scanning an object includes scanning an object using a first scanning mode and, after a halt/dieback situation occurs, scanning the object using a second mode. Hereinafter, the term “halt/dieback” is referred to as a “halt” and/or “halting.” Data from the first scanning mode is reconstructed using a first reconstruction algorithm, and data from the second scanning mode is reconstructed using a second reconstruction algorithm. Such a method may be implemented using any suitable scanning methods.

Three example implementations include: (1) a first implementation that includes recording a motion of a conveyor as an object is accelerated, and using this recorded motion to modify a reconstruction algorithm for the second scanning mode; (2) a second implementation includes scanning an object in an imaging section in a “step-and-shoot” mode after resuming motion and accelerating the conveyor to full speed after the object exits the imaging section; and (3) a third implementation includes scanning an object in an imaging section at a reduced constant velocity after motion is resumed until the object exits the imaging section. In each of the three examples, the scanning system is configured to perform a different reconstruction technique during a time in which an object within the imaging section resumes motion.

As used herein, the phrase “reconstructing an image” is not intended to exclude embodiments in which data representing an image is generated but a viewable image is not. Therefore, as used herein the term “image” broadly refers to both viewable images and data representing a viewable image. However, many embodiments generate (or are configured to generate) at least one viewable image. Additionally, although described in detail in a CT inspection setting, it is contemplated that the benefits accrue to all imaging modalities including, for example, ultrasound, Magnetic Resonance Imaging (MRI), Electron Beam CT (EBCT), Positron Emission Tomography (PET), Single Photon Emission Computed Tomography (SPECT), and in both non-medical settings and medical settings. Further, as used herein, “a scan” refers to a continuous scan that begins when a first object of a stream of objects enters a scanning system and ends when a last object of the stream of objects exits the scanning system.

In the embodiments described herein, a scanning mode of the scan is switched between a first scanning mode and a second mode while the scan is continuously performed. More specifically, when a conveyor halts during the continuous scan, a scanning mode of the scan switches from the first scanning mode to the second scanning mode. After an object has cleared an imaging section after the halt, the scanning mode of the scan switches from the second scanning mode back to the first scanning mode. During the scanning mode switches, even if the conveyor halts, the scan continues to be performed.

FIG. 1is a schematic view of an exemplary scanning system10. Scanning system10includes a conveyor12and an imaging section or a CT system14positioned at least partially within a housing16. CT system14may also be referred to herein as an imaging section of scanning system10. Conveyor12extends between an inlet18of housing16and an outlet20of housing16. Further, conveyor12is configured to transport a stream22of objects24through scanning system10. In the exemplary embodiment, stream22includes at least one object24. Conveyor12extends through CT system14and conveys objects24sequentially through CT system14such that each object24is scanned by CT system14. CT system14is configured to scan objects24one at a time in the exemplary embodiment.

A control system26is in operational control communication with conveyor12and CT system14. As used herein, “operational control communication” refers to a link, such as a conductor, a wire, and/or a data link, between two or more components of scanning system10that enables signals, electric currents, and/or commands to be communicated between the two or more components. The link is configured to enable one component to control an operation of another component of scanning system10using the communicated signals, electric currents, and/or commands. Further, as used herein, the term “control system” is not limited to just those integrated circuits referred to in the art as a control system, but broadly refers to a computer, microcontroller, a microcomputer, a programmable logic controller, an application specific integrated circuit, and/or any other programmable circuit.

Control system26includes a central processing unit and may include a device, such as a floppy disk drive or a compact-disc read-only memory (CD-ROM) drive, for reading data from a computer-readable medium, such as a floppy disk, a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), and/or a digital versatile disc (DVD). In an alternative embodiment, control system26executes instructions stored in firmware. In the exemplary embodiment, control system26controls speed, acceleration, deceleration, starting, stopping, and/or any other suitable function of conveyor12. Further, control system26controls CT system14and/or conveyor12to acquire data relating to objects24, as described in more detail below. In the exemplary embodiment, control system26is also in communication with an input device28and a display device30. Display device30may include, without limitation, a liquid crystal display (LCD), a cathode ray tube (CRT), and/or any other suitable output device. Input device28includes, without limitation, a mouse and a keyboard.

In the exemplary embodiment, CT system14includes a radiation source32for emitting radiation34and a detector36for detecting emitted radiation34. An examination region38is defined between radiation source32and detector36. In the exemplary embodiment, radiation source32and detector36are coupled to a gantry40for rotation about examination region38. Alternatively, radiation source32and/or detector36are coupled within CT system14such that radiation source32and/or detector36are stationary with respect to examination region38. In the exemplary embodiment, CT system14performs a continuous helical scan as stream22of objects24passes through examination region38unless conveyor12is halted, as described in more detail herein.

Radiation source32emits radiation34as X-rays in a cone-beam in the exemplary embodiment. Alternatively, radiation source32may emit any suitable radiation having any suitable beam shape, such as a fan beam. Detector36includes a plurality of rows42and columns (not shown) of detector elements44. Each row42extends in a direction that is substantially perpendicular to a direction of object travel as indicated by directional arrow46. The columns are substantially parallel to the object travel direction indicated by directional arrow46. Each detector element44produces an electrical signal that represents an intensity of an impinging radiation beam and, hence, the attenuation of the beam as the beam passes through object24. The electrical signals produced by detector elements44are transmitted to control system26.

In the exemplary embodiment, a scan controller is in operative control communication with CT system14. Control system26is in operational control communication with scan controller48, which controls radiation source32, detector36, and gantry40. Scan controller48controls emission of radiation34from radiation source32and receives data from detector36. Scan controller48transmits data received from detector36to control system26. Further, scan controller48controls components of CT system14in any suitable manner that enables CT system14to function as described herein.

Further, in the exemplary embodiment, a conveyor controller50is in operative control communication with conveyor12. Control system26is in operational control communication with conveyor controller50, which controls motion of conveyor12. More specifically, conveyor controller50controls acceleration, deceleration, velocity, and/or any motion parameter of conveyor12. Conveyor controller50receives commands from control system26to control conveyor12, as described herein.

FIG. 2is a flowchart of an exemplary method100of performing a scan of an object24(shown inFIG. 1) that may be used with scanning system10(shown inFIG. 1). In the exemplary embodiment, method100is used when stream22of objects24(shown inFIG. 1) is being scanned by CT system14(shown inFIG. 1) using a continuous scan. In the exemplary embodiment, method100is performed by control system26(shown inFIG. 1), scan controller48(shown inFIG. 1), and conveyor controller50(shown inFIG. 1).

Referring toFIGS. 1 and 2, method100includes performing102a first portion of a scan in a first scanning mode to acquire a first dataset using scan controller48. More specifically, the first portion of the scan in the first scanning mode is continuously performed102by scanning system10to acquire data of stream22of objects24as conveyor12transports objects24through CT system14. During the first scanning mode, gantry40rotates about examination region38, and conveyor12transports objects24through examination region38.

The first portion of the scan in the first scanning mode is performed102until a halt command is issued by control system26. More specifically, conveyor controller50receives104the halt command for conveyor12from control system26. Further, scan controller48also receives104the halt command for gantry40. The halt command instructs conveyor controller50to halt conveyor12and instructs scan controller48to stop acquiring image data of object24.

Once conveyor controller50receives104the halt command, conveyor controller50decelerates106conveyor12from a motion during the first scanning mode to a halt based on the halt command. Control system26then determines108whether object24is present within examination region38. More specifically, control system26determines108a presence of object24within examination region38using any suitable method and/or technique, such as using sensors within scanning system10. When control system26determines108object24is not present within examination region38, control system26commands conveyor controller50to resume110motion of conveyor12. More specifically, conveyor12resumes110a motion for performing102the first scanning mode. After conveyor12resumes110motion, the first portion of the scan in the first scanning mode is performed102. When control system26determines108object24is present within examination region38, control system26reconstructs112the first dataset using a first reconstruction algorithm. However, in the exemplary embodiment, reconstruction112of the first dataset yields a partial image of object24within examination region38.

Further, when control system26determines108object24is present within examination region38, control system26issues a resume command. When scan controller48and/or conveyor controller50receives114the resume command, scan controller48and/or conveyor controller50perform116a second portion of the scan in a second scanning mode to acquire a second dataset. In the exemplary embodiment, the second scanning mode is different than the first scanning mode, and the first scanning mode and the second scanning mode are any suitable scanning modes.

After the scan in the second scanning mode is performed116, control system26reconstructs118the second dataset using a second reconstruction algorithm. In the exemplary embodiment, the second reconstruction algorithm is different than the first reconstruction algorithm, and the first reconstruction algorithm and the second reconstruction algorithm are any suitable reconstruction algorithms. Reconstruction118of the second dataset yields another partial image of object24. In the exemplary embodiment, the partial image from the first dataset reconstruction112and the partial image from the second dataset reconstruction118form a whole or complete image of object24within examination region38.

More specifically, control system26generates120an image of object24using the first reconstructed dataset and the second reconstructed dataset. In the exemplary embodiment, the first reconstructed dataset and the second reconstructed dataset are combined to generate120the image. As such, a whole or complete image of object24is reconstructed even though motion of object24was halted and resumed during the continuous scan. The generated image is optionally output122to display device30. The generated image may also be transmitted to any suitable system for further processing and/or inspection. In the exemplary embodiment, the generated image is used to determine contents of object24. In a transportation setting, for example, such as at an airport, the generated image is used to determine if contraband, such as weapons, narcotics, explosives, and/or other prohibited materials or objects, is present within object24. Method100is performed each time a halt command is received104during performance102of the first portion of scan in the first scanning mode.

FIG. 3is a flowchart of a first example method200of method100(shown inFIG. 2). Method200includes the steps of method100and, as such, similar components are labeled with similar references.

Referring toFIGS. 1 and 3, method200includes performing102a first portion of a scan in a first scanning mode to acquire a first dataset using scan controller48. More specifically, the first portion of the scan in the first scanning mode is continuously performed102by scanning system10to acquire data of stream22of objects24as conveyor12transports objects24through CT system14. During the first scanning mode, gantry40rotates about examination region38, and conveyor12transports objects24through examination region38. In method200, the first portion of the scan is performed202in a helical mode to acquire the first dataset. Performing102the first portion of the scan in the first scanning mode also includes recording204first motion trajectory data of conveyor12as conveyor12decelerates to a halt, as described in more detail below.

The first portion of the scan in the first scanning mode is performed202until a halt command is issued by control system26. More specifically, conveyor controller50receives104the halt command for conveyor12from control system26. Further, scan controller48also receives104the halt command for gantry40. The halt command instructs conveyor controller50to halt conveyor12and instructs scan controller48to stop acquiring image data of object24.

Once conveyor controller50receives104the halt command, conveyor controller50decelerates106conveyor12from a motion during the first scanning mode to a halt based on the halt command. More specifically, in method200, deceleration206of conveyor12is controlled by controlling a rate of deceleration. The first portion of the scan in helical mode continues to be performed202while conveyor decelerates206. A motion trajectory of conveyor12as conveyor12decelerates206is recorded204in control system26as part of the performance102of the first portion of the scan in the first scanning mode. More specifically, the motion trajectory, such as the rate of deceleration, is recorded204as the first motion trajectory data in control system26.

Control system26then determines108whether object24is present within examination region38. More specifically, control system26determines108the presence of object24within examination region38using any suitable method and/or technique, such as using sensors within scanning system10. When control system26determines108object24is not present within examination region38, control system26commands conveyor controller50to resume110motion of conveyor12. More specifically, conveyor12resumes110a motion for performing202the first portion of the scan in the helical mode. After conveyor12resumes110motion, the first portion of the scan in the helical mode continues to be performed202. When control system26determines108object24is present within examination region38, control system26reconstructs112the first dataset using a first reconstruction algorithm. More specifically, method200includes reconstructing208the first dataset using a known variable pitch helical reconstruction algorithm that accounts for the recorded first motion trajectory data. One example of a known variable pitch helical reconstruction algorithm is the variable pitch helical reconstruction algorithm described in by Alexander Katsevich, Samit Basu, and Jiang Hsieh, “Exact filtered backprojection reconstruction for dynamic pitch helical cone beam computed tomography,” 2004 Phys. Med. Biol. 49, pgs. 3089-3103 (referred to hereinafter as the “Katsevich algorithm”). However, in the exemplary embodiment, reconstruction208of the first dataset yields a partial image of object24within examination region38.

Further, when control system26determines108object24is present within examination region38, control system26issues a resume command. When scan controller48and/or conveyor controller50receives114the resume command, scan controller48and/or conveyor controller50perform116a second portion of the scan in a second scanning mode to acquire a second dataset. In the exemplary embodiment, the second scanning mode is different than the first scanning mode. The resume command in method200is transmitted to conveyor controller50to control the motion of conveyor12during the second scanning mode and is transmitted to scan controller48to control at least a motion of gantry40.

More specifically, in method200, performing116the second portion of the scan in the second scanning mode includes resuming210motion of conveyor12at a controlled acceleration, recording212second motion trajectory data of conveyor12as conveyor12accelerates, and performing214the second portion of the scan in a helical mode to acquire the second dataset. When resuming210motion of conveyor12, conveyor controller50accelerates conveyor12from the halt after receiving114the resume command. Control system26records212data relating to the motion of conveyor12as the second motion trajectory data. The second motion trajectory data includes data related to acceleration of conveyor12and/or velocity of conveyor12before, during, and/or after the acceleration. In the exemplary embodiment, conveyor12accelerates to a velocity that is substantially equal to a velocity of conveyor12before the halt command was received104. The second portion of the scan in helical mode is performed214while conveyor12accelerates and after conveyor12is at a substantially constant velocity.

After the second portion of the scan in the second scanning mode is performed116, control system26reconstructs118the second dataset using a second reconstruction algorithm. In the exemplary embodiment, the second reconstruction algorithm is different than the first reconstruction algorithm. More specifically, in the exemplary embodiment, the second dataset is reconstructed216using a known variable pitch helical reconstruction algorithm that accounts for the recorded second motion trajectory data. One example of a known variable pitch helical reconstruction algorithm that can be used to reconstruct216the second dataset is the Katsevich algorithm. Reconstruction216of the second dataset yields another partial image of object24. In the exemplary embodiment, the partial image from the first dataset reconstruction208and the partial image from the second dataset reconstruction216form a whole or complete image of object24within examination region38.

More specifically, control system26generates120an image of object24using the first reconstructed dataset and the second reconstructed dataset. In the exemplary embodiment, the first reconstructed dataset and the second reconstructed dataset are combined to generate120the image. As such, a whole or complete image of object24is reconstructed even though motion of object24was halted and resumed during the continuous scan. The generated image is optionally output122to display device30. The generated image may also be transmitted to any suitable system for further processing and/or inspection. In the exemplary embodiment, the generated image is used to determine contents of object24. In a transportation setting, for example, such as at an airport, the generated image is used to determine if contraband, such as weapons, narcotics, explosives, and/or other prohibited materials or objects, is present within object24. Method200is performed each time a halt command is received104during performance102of the first portion of the scan in the first scanning mode.

FIG. 4is a flowchart of a second example method300of method100(shown inFIG. 2). Method300includes the steps of method100and, as such, similar components are labeled with similar references.

Referring toFIGS. 1 and 4, method300includes performing102a first portion of a scan in a first scanning mode to acquire a first dataset using scan controller48. More specifically, the first portion of the scan in the first scanning mode is continuously performed102by scanning system10to acquire data of stream22of objects24as conveyor12transports objects24through CT system14. During the first scanning mode, gantry40rotates about examination region38, and conveyor12transports objects24through examination region38. In method300, the first portion of the scan is performed302in a helical mode to acquire the first dataset.

The first portion of the scan in helical mode is performed302until a halt command is issued by control system26. More specifically, conveyor controller50receives104the halt command for conveyor12from control system26. Further, scan controller48also receives104the halt command for gantry40. The halt command instructs conveyor controller50to halt conveyor12and instructs scan controller48to stop acquiring image data of object24.

Once conveyor controller50receives104the halt command, conveyor controller50decelerates106conveyor12from a motion during the first scanning mode to a halt based on the halt command. More specifically, method300includes decelerating304conveyor12at a controlled rate of deceleration. Control system26then determines108whether object24is present within examination region38. More specifically, control system26determines108a presence of object24within examination region38using any suitable method and/or technique, such as using sensors within scanning system10. When control system26determines108object24is not present within examination region38, control system26commands conveyor controller50to resume110motion of conveyor12. More specifically, conveyor12resumes110a motion for performing302the first scanning mode. After conveyor12resumes110motion, the first portion of the scan in the helical mode is performed302. When control system26determines108object24is present within examination region38, control system26reconstructs112the first dataset using a first reconstruction algorithm.

More specifically, in method300, the first dataset is reconstructed306using a known helical reconstruction algorithm, such as a three-dimensional helical reconstruction algorithm. Examples of algorithms that can be used to perform reconstruction306are the algorithm described in World Intellectual Property Organization published application No. WO 08/036463 A2, “Ray Consistency Based Reconstruction of Helical Cone Beam Data,” (hereinafter referred to as the “Pack algorithm”) and the algorithm described in U.S. Pat. No. 6,574,299, “Exact filtered back projection (FBP) algorithm for spiral computer tomography,” to Alexander Katsevich (hereinafter referred to as the “Exact FBP algorithm”). However, in the exemplary embodiment, reconstruction306of the first dataset yields a partial image of object24within examination region38.

Further, when control system26determines108object24is present within examination region38, control system26issues a resume command. When scan controller48and/or conveyor controller50receives114the resume command, scan controller48and/or conveyor controller50perform116a second portion of the scan in a second scanning mode to acquire a second dataset. In the exemplary embodiment, the second scanning mode is different than the first scanning mode. The resume command in method300is transmitted to conveyor controller50to control the motion of conveyor12during the second scanning mode and is transmitted to scan controller48to control at least a motion of gantry40. More specifically, in the exemplary embodiment, the second scanning mode is a step-and-shoot mode. Performing116the second portion of the scan in the second scanning mode includes acquiring308data from a single rotation of gantry40about examination region38and advancing310conveyor12by a predetermined amount using conveyor controller50. The predetermined amount is selected to scan a subsequent portion of object24using another single rotation of gantry40.

After conveyor12is advanced310by control system26and conveyor controller50, control system26determines312whether object24is within examination region38using any suitable method and/or technique. When control system26determines312that object24is present within examination region38, control system26acquires308data from a subsequent single rotation of gantry40via scan controller48, and again advances310conveyor12via conveyor controller50.

When control system26determines312object24is not present within examination region38, control system26commands conveyor controller50to resume110motion of conveyor12. More specifically, conveyor12resumes110a motion for performing302the first scanning mode. Further, when control system26determines312object24is not present within examination region38, control system26reconstructs118the second dataset using a second reconstruction algorithm. In the exemplary embodiment, the second reconstruction algorithm is different than the first reconstruction algorithm. More specifically, in the exemplary embodiment, control system26reconstructs314the second dataset using a known axial reconstruction algorithm. One example of an algorithm used to perform reconstruction314is the algorithm described by L. A. Feldkamp, L. C. Davis, and J. W. Kreiss, “Practical Cone Beam Algorithms.” J of Opt. Soc. Am., A/Vol. 1, No. 6, pgs. 612-619 (June 1984) (hereinafter referred to as the “FDK algorithm”). Reconstruction314of the second dataset yields another partial image of object24. In the exemplary embodiment, the partial image from the first dataset reconstruction306and the partial image from the second dataset reconstruction314form a whole or complete image of object24within examination region38.

More specifically, control system26generates120an image of object24using the first reconstructed dataset and the second reconstructed dataset. In the exemplary embodiment, the first reconstructed dataset and the second reconstructed dataset are combined to generate120the image. As such, a whole or complete image of object24is reconstructed even though motion of object24was halted and resumed during the continuous scan. The generated image is optionally output122to display device30. The generated image may also be transmitted to any suitable system for further processing and/or inspection. In the exemplary embodiment, the generated image is used to determine contents of object24. In a transportation setting, for example, such as at an airport, the generated image is used to determine if contraband, such as weapons, narcotics, explosives, and/or other prohibited materials or objects, is present within object24. Method300is performed each time a halt command is received104during performance102of the scan in the first scanning mode.

FIG. 5is a flowchart of a third example method400of method100(shown inFIG. 2). Method400includes the steps of method100and, as such, similar components are labeled with similar references.

Referring toFIGS. 1 and 5, method400includes performing102a first portion of a scan in a first scanning mode to acquire a first dataset using scan controller48. More specifically, the first portion of the scan in the first scanning mode is continuously performed102by scanning system10to acquire data of stream22of objects24as conveyor12transports objects24through CT system14. During the first scanning mode, gantry40rotates about examination region38, and conveyor12transports objects24through examination region38. In method400, the first portion of the scan is performed402in a helical mode at a first speed to acquire the first dataset. The scan performed402at the first speed is also referred to herein as a “full speed scan.” As used herein, the term “speed” refers to at least a velocity of conveyor12through scanning system10. The term “speed” may also refer to a rotational velocity of gantry40.

The first portion of the scan in helical mode is performed402until a halt command is issued by control system26. More specifically, conveyor controller50receives104the halt command for conveyor12from control system26. Further, scan controller48also receives104the halt command for gantry40. The halt command instructs conveyor controller50to halt conveyor12and instructs scan controller48to stop acquiring image data of object24.

Once conveyor controller50receives104the halt command, conveyor controller50decelerates106conveyor12from a motion during the first scanning mode to a halt based on the halt command. Control system26then determines108whether object24is present within examination region38. More specifically, control system26determines108a presence of object24within examination region38using any suitable method and/or technique, such as using sensors within scanning system10. When control system26determines108object24is not present within examination region38, control system26commands conveyor controller50to resume110motion of conveyor12. More specifically, conveyor12resumes110a motion for performing402the first scanning mode such that the first portion of the scan is performed402at the first speed. After conveyor12resumes110motion, the first portion of the scan in the full speed helical mode is performed402. When control system26determines108object24is present within examination region38, control system26reconstructs112the first dataset using a first reconstruction algorithm. More specifically, in method400, the first dataset is reconstructed404using a known helical reconstruction algorithm, such as a three-dimensional helical reconstruction algorithm. Examples of algorithms that can be used to perform reconstruction404are the Pack algorithm and the Exact FBP algorithm. However, in the exemplary embodiment, reconstruction404of the first dataset yields a partial image of object24within examination region38.

Further, when control system26determines108object24is present within examination region38, control system26issues a resume command. When scan controller48and/or conveyor controller50receives114the resume command, scan controller48and/or conveyor controller50perform116a second portion of the scan in a second scanning mode to acquire a second dataset. In the exemplary embodiment, the second scanning mode is different than the first scanning mode. The resume command in method400is transmitted to conveyor controller50to control the motion of conveyor12during the second scanning mode and is transmitted to scan controller48to control at least a motion of gantry40. More specifically, in the exemplary embodiment, the second scanning mode is a helical scan mode at a second speed that is less than the first speed. The second portion of the scan performed408at the second speed is also referred to herein as a “partial speed scan.” Performing116the second portion of the scan in the second scanning mode includes resuming406motion of conveyor12at the second speed, performing408a helical scan at the second speed, and recording410motion data of conveyor12as the helical scan is performed408. In the exemplary embodiment, the recorded motion data of conveyor12includes acceleration data and/or speed data.

As the helical scan at the second speed is performed408, control system26determines412whether object24is within examination region38using any suitable method and/or technique. When control system26determines412that object24is present within examination region38, control system26continues to perform408the helical scan at the second speed to acquire data via CT system14and continues to record410the motion of conveyor12.

When control system26determines412object24is not present within examination region38, control system26commands conveyor controller50to resume110motion of conveyor12at the first speed. More specifically, conveyor12resumes110a motion for performing402the first scanning mode. To resume110the first speed, control system26accelerates414conveyor12to the speed of the first helical mode using conveyor controller50when object24has exited examination region38. After conveyor12resumes110motion at the first speed, the first portion of the scan is performed102. Further, when control system26determines412object24is not present within examination region38, control system26reconstructs118the second dataset using a second reconstruction algorithm. In the exemplary embodiment, the second reconstruction algorithm is different than the first reconstruction algorithm. More specifically, in the exemplary embodiment, control system26reconstructs416the second dataset using a known two-dimensional variable pitch helical reconstruction algorithm. An example of an algorithm that can be used to perform reconstruction416is the algorithm described in U.S. Pat. No. 6,411,670, “Data Rebinning to Increase Resolution in CT Image Reconstruction” (hereinafter referred to as the “Besson algorithm”). Reconstruction416of the second dataset yields another partial image of object24. In the exemplary embodiment, the partial image from the first dataset reconstruction404and the partial image from the second dataset reconstruction416form a whole or complete image of object24within examination region38.

More specifically, control system26generates120an image of object24using the first reconstructed dataset and the second reconstructed dataset. In the exemplary embodiment, the first reconstructed dataset and the second reconstructed dataset are combined to generate120the image. As such, a whole or complete image of object24is reconstructed even though motion of object24was halted and resumed during the continuous scan. The generated image is optionally output122to display device30. The generated image may also be transmitted to any suitable system for further processing and/or inspection. In the exemplary embodiment, the generated image is used to determine contents of object24. In a transportation setting, for example, such as at an airport, the generated image is used to determine if contraband, such as weapons, narcotics, explosives, and/or other prohibited materials or objects, is present within object24. Method400is performed each time a halt command is received104during performance102of the first portion of the scan in the first scanning mode.

The above-described embodiments facilitate continuously scanning a stream of objects even when the stream of objects halts and resumes motion. More specifically, the embodiments described herein enable an object to continue to be scanned after the object has halted in an imaging section of a scanning system while a scan is being performed. Data acquired before the object is halted is not discarded and is used to reconstruct an image of the object. As such, the object is not required to be manually inspected when a halt within the imaging section occurs. Further, the second implementation of the exemplary method described herein facilitates maintaining a quality of the image after a halt has occurred. The above-described the third implementation of the exemplary method facilitates resuming a full speed scan after a halt because a conveyor continues to move through a second scanning mode.

A technical effect of the systems and method described herein includes at least one of: (a) performing a first portion of a scan in a first scanning mode to acquire a first dataset using a scan controller; (b) receiving a halt command for a conveyor within a scanning system at at least a conveyor controller; (c) decelerating a conveyor to a halt based on a halt command using a conveyor controller; (d) when an object is present within an examination region after a conveyor has halted, performing a second portion of a scan in a second scanning mode to acquire a second dataset using a scan controller, the second scanning mode different than a first scanning mode; (e) reconstructing a first dataset using a first reconstruction algorithm within a control system; (f) reconstructing a second dataset using a second reconstruction algorithm within a control system, the second reconstruction algorithm different than a first reconstruction algorithm; and (g) generating an image using a first reconstructed dataset and a second reconstructed dataset using a control system.

Exemplary embodiments of a method and a system for performing a scan of an object are described above in detail. The method and system are not limited to the specific embodiments described herein, but rather, components of the system and/or steps of the method may be utilized independently and separately from other components and/or steps described herein. For example, the method may also be used in combination with other scanning systems and methods, and is not limited to practice with only the computer tomography system and methods as described herein. Rather, the exemplary embodiment can be implemented and utilized in connection with many other imaging applications.