Abstract:
A detection device for detecting X rays and signaling the detection to a computer-assisted surgery processor system comprises an X ray detector unit having an X ray detector adapted to be positioned within a radiation field. The X ray detector emits a detection signal upon being excited by an X ray of a given intensity. A transmitter outputs the detection signal in radio frequency. A receiver receives the detection signal in radio frequency and forwards the detection signal to a computer-assisted surgery processor system to signal the detection of the X ray. A method is provided as well.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims U.S. Provisional Patent Application No. 61/083,985, filed on Jul. 28, 2008. 
     
    
     FIELD OF THE APPLICATION 
       [0002]    The present application relates to computer-assisted surgery, and more particularly to C-arm imaging and tracking. 
       BACKGROUND OF THE ART 
       [0003]    C-arm units are commonly used in order to obtain X-ray images of bodily parts during surgery. C-arm trackers have been integrated in computer-assisted surgery (CAS), by the addition of a C-arm tracker to a C-arm unit, in order to allow image-based navigation. As the accuracy of the computer-assisted surgery is dependent on the quality of the images, the C-arm tracker is used to relate the X-ray image to the tracking of the bodily part. 
         [0004]    The relation between the X-ray image and the tracking of the bodily part is obtained by tracking the C-arm tracker to provide a scale relation between the image and the bodily part. Because of accuracy requirements for CAS surgery, the positional relation between the C-arm tracker and the tracked bodily part must be recorded at the time that the image is taken, for instance to avoid errors due to movement between the patient and the C-arm tracker, from the moment the X-ray is taken and to the moment the X-ray image file is converted to navigation data. 
         [0005]    Accordingly, diodes are commonly used to detect X-rays. More specifically, diodes are provided on the C-arm tracker and are wired to the CAS processor system so as to detect and signal the detection of X-rays. With the signaling of the X-ray, the CAS processor system simultaneously records the positional relation between the C-arm tracker and the patient. The positional relation is then used in the conversion of the X-ray image to navigation data, for instance to adjust the orientation of the image. 
       SUMMARY OF THE APPLICATION 
       [0006]    It is therefore an aim of the present disclosure to provide a novel X-ray detection device for C-arm tracker, and a method of signaling detection. 
         [0007]    It is a further aim of the present disclosure to provide a novel method for the calibration of a C-arm tracker. 
         [0008]    Therefore, in accordance with a first embodiment, there is provided a detection device for detecting X-rays and signaling the detection to a computer-assisted surgery processor system, comprising: an X-ray detector unit having an X-ray detector adapted to be positioned within a radiation field, the X-ray detector emitting a detection signal upon being excited by an X-ray of a given intensity; a transmitter for outputting the detection signal in radio frequency; and a receiver for receiving the detection signal in radio frequency and for forwarding the detection signal to a computer-assisted surgery processor system to signal the detection of the X-ray. 
         [0009]    Further in accordance with the first embodiment, the detection device is adapted to detect X-rays from a C-arm, and the X-ray detector unit further comprises a memory for storing a definition file of a C-arm tracker used with the C-arm, the transmitter and the receiver wirelessly transmitting in radio frequency the definition file to the computer-assisted surgery processor system. 
         [0010]    Still further in accordance with the first embodiment, the detection device is adapted to detect X-rays from a C-arm, and the X-ray detector is mounted directly to a C-arm tracker. 
         [0011]    Still further in accordance with the first embodiment, the X-ray detector comprises a plurality of scintillator diodes mounted to a rim of the C-arm tracker. 
         [0012]    Still further in accordance with the first embodiment, X-ray detector comprises at least one scintillator diode emitting the detection signal when excited by an X-ray, the detection signal being proportional to an intensity of the X-ray. 
         [0013]    Still further in accordance with the first embodiment, the X-ray detector unit has a processor measuring an intensity of the detection signal, the transmitter outputting the detection signal if the measured intensity is above a threshold intensity. 
         [0014]    Still further in accordance with the first embodiment, the X-ray detector unit has a processor measuring an intensity of the X-ray, the processor emitting the detection signal if the measured intensity is above a threshold intensity. 
         [0015]    Still further in accordance with the first embodiment, the transmitter outputs the detection signal is in synchronization with a falling edge of a radiation wave of the X-ray detected by the X-ray detector. 
         [0016]    In accordance with a second embodiment embodiment, there is provided a method for signaling a detection of an X-ray to a computer-assisted surgery processor system, comprising: activating an X-ray detection in a radiation field; producing a detection signal upon detecting an X-ray of a given intensity in the radiation field; and transmitting the detection signal to a computer-assisted surgery processor system using radio frequency. 
         [0017]    Further in accordance with the second embodiment, the method is used to detect X-rays from a C-arm, the method further comprising storing a definition file of a C-arm tracker, and transmitting the definition file to the computer-assisted surgery system using radio frequency. 
         [0018]    Still further in accordance with the second embodiment, producing a detection signal comprises determining whether the intensity of the X-ray is above an intensity threshold, and transmitting the detection signal comprises transmitting the detection signal if the intensity of the X-ray is above the intensity threshold. 
         [0019]    Still further in accordance with the second embodiment, the method is used to detect X-rays from a C-arm, and further wherein activating the X-ray detection comprises mounting an X-ray detector to a C-arm tracker. 
         [0020]    Still further in accordance with the second embodiment, transmitting the detection signal comprises synchronizing the transmission with a falling edge of a radiation wave of the detected X-ray. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0021]      FIG. 1  is a block diagram of a computer-assisted surgery processor system used with a C-arm and with an X-ray detection device in accordance with a preferred embodiment of the present disclosure; and 
           [0022]      FIG. 2  is a flow chart illustrating a method for signaling an X-ray to a CAS processor system in accordance with another preferred embodiment of the present disclosure. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0023]    Referring to  FIG. 1 , an X-ray detection device as used with a computer-assisted surgery (CAS) processor system  10  is generally illustrated at  11 . The X-ray detection device  11  is used in combination with the CAS processor system  10  to signal the acquisition of an image from a C-arm unit  13 . The X-ray detection device  11  has an X-ray detection unit  12  and is used during computer-assisted surgical procedures in which image-based navigation is performed, such as spine surgery (pedical screw placement) and some types of traumatology surgery or any type of surgery using fluoroscopy technology for image-based navigation. 
         [0024]    As known in the art, the C-arm unit  13  is connected to a C-arm  14  obtaining X-ray images of a bodily part, such as a spine. A C-arm tracker  16  is physically mounted to the C-arm  14  for the subsequent image-based navigation during the surgical procedure. 
         [0025]    As known in the art, the C-arm tracker  16  provides a plate with a bead pattern for the calibration of the image, in order to ensure its accurate reproduction (e.g., dewarping) by the CAS processor system  10  in view of the navigation. The CAS processor system  10  tracks a position and orientation of the C-arm tracker  16  so as to relate the images obtained from the C-arm  14  to the tracking of the bodily part. As a known solution for the tracking, both the C-arm tracker  16  and the bodily part are tracked using passive optical tracking (e.g., a Northern Digital™ system). Alternatives to passive optical tracking are considered and used as well (e.g., active sensors, such as infrared LEDs, magnetic emitters, and any other suitable tracking system, etc). 
         [0026]    The image-based navigation data is output on an interface  18 . For instance, visual representations of tools are provided in real-time with respect to X-ray images of a portion of a spine. 
         [0027]    The X-ray detection device  11  is a self-powered (e.g., battery operated) device that detects X-rays and signals the X-ray detection to a CAS processor system  10 . The X-ray detection unit  12  has an X-ray detector  20  to detect the X-rays. Accordingly, the X-ray detector  20  is positioned in the field of radiation of the C-arm  14 . In an embodiment, the X-ray detector  20  is physically mounted to the C-arm tracker  16 , so as to avoid any obstruction of the detector  20  in the field of radiation, for instance by the presence of metallic tools or the like. 
         [0028]    In an embodiment, the X-ray detector  20  has scintillator diodes that are excited by the X-ray. Scintillator diodes generate a signal proportional to an X-ray intensity. Other types of diodes excited by the detection of X-rays are also considered. In another embodiment, one or more scintillator diodes are distributed on the circular rim of the C-arm tracker  16 , to ensure that at least one of the scintillator diodes detects the X-ray emission. 
         [0029]    According to the type of X-ray detector  20  used, the signal from the X-ray detector  20  may require to be amplified. The X-ray detection unit  12  with the scintillator diodes has a processing circuit  22 . The processing circuit  22  also filters out detected light of insufficient intensity. For instance, residual radiation and backscatter should not be detected by the X-ray detector  20 , whereby the processing circuit  22  has a threshold value for the radiation intensity. If the intensity of the amplified detected radiation is above the threshold value, the processing circuit  22  produces a detection signal that is transmitted to the CAS processor system  10 . Filtering out of detected light of insufficient intensity may be performed by the CAS processor system  10 . 
         [0030]    The X-ray detection device  11  also has a radio-frequency (RF) transmitter  24  that is connected to the processing circuit  22  to produce an RF transmission indicative of the detection signal. In the embodiment in which the X-ray detectors  20  are mounted to the C-arm tracker  16 , the processing circuit  22  and the RF transmitter  24  are also mounted to the C-arm tracker  16 . 
         [0031]    The X-ray detection device  11  also has an RF receiver  26  is connected to the CAS processor system  10 , and is configured to receive the RF transmission from the RF transmitter  24 , for wireless transmission of the detection signal. The RF transmitter  24  and the RF receiver  26  may be self-powered and configured to send appropriate signals to the CAS processor system  10 . 
         [0032]    By using RF technology for the transmission of the detection signal, there is no need for a line of sight between the sensor unit of the CAS processor system  10  and the X-ray detection device  11 . Moreover, by the use of self-powered wireless transmission, there are no wires relating the X-ray detection device  11  to the CAS processor system  10 , whether it be for the transmission of data or to supply power to the device  11 . Bluetooth, wi-fi, Zigbee standards are amongst the various standards considered for the RF transmission. 
         [0033]    According to an embodiment, the X-ray detection device  11  is part of the C-arm tracker  16 , and stores C-arm calibration data  28 . The C-arm calibration data  28  is used by the CAS processor system  10  to identify the C-arm tracker  16 . As each C-arm tracker  16  has individual specifications (e.g., orientation of plate and bead pattern, types of trackers used, position and orientation of trackers on the C-arm tracker  16 ), the CAS processor system  10  must calibrate the C-arm tracker  16 , for instance by receiving a definition file for the C-arm tracker  16 . The definition file may simply consist of an identification of the C-arm tracker for the CAS processor system  10  to obtain a calibration data from another source, or may comprise additional information (e.g., orientation data). In an embodiment, the definition file comprises relational data related to the bead pattern of the plate of the C-arm tracker  16 . 
         [0034]    Referring to  FIG. 2 , now that the X-ray detection device  11  has been described, a method  40  of using the X-ray detection device  11  is described. 
         [0035]    According to Step  42 , the X-ray detection unit  12  is positioned within the field of radiation of the C-arm  14 , whereby emission of radiation by the C-arm  14  is detected by the X-ray detection device  11 . 
         [0036]    According to Step  44 , the X-ray detection unit  12  is activated to a detection mode. 
         [0037]    According to Step  45 , the X-ray is detected by the X-ray detection unit  12  when the X-ray is performed. 
         [0038]    At Decision  46 , upon detecting radiation and treating the resulting radiation signal, the X-ray detection unit  12  compares the intensity of the radiation to a threshold value. If the X-ray detection signal is below the threshold value, the X-ray detection unit  12  is idle. 
         [0039]    According to Step  48 , if the intensity is above the threshold value, an X-ray detection signal is transmitted to the CAS processor system  10  using RF transmission to indicate that an X-ray is detected. In an embodiment, the transmission of the X-ray detection signal by the RF transmitter  24  is synchronized with the falling edge of the radiation wave detected by the X-ray detector  20 . The definition file is optionally transmitted to the CAS processor system  10  using RF transmission, to calibrate the C-arm tracker  16  with the CAS processor system  10 . The definition file may be transmitted at any other time prior to Step  48 . 
         [0040]    According to Step  50 , the positional relation between the C-arm tracker  16  and the tracked bodily part is recorded by the CAS processor system  10  upon reception of the RF transmission from the X-ray detector device  11 . Therefore, the image file, the positional relation and optionally the definition file are used to convert the X-ray image to navigation data.