The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

L Ren - One of the best experts on this subject based on the ideXlab platform.

  • an interprojection sensor fusion approach to estimate blocked projection signal in synchronized moving grid based cbct system
    Medical Physics, 2015
    Co-Authors: Hong Zhang, L Ren, V Kong, W Giles, You Zhang, Jian Yue Jin
    Abstract:

    Purpose: A preobject grid can reduce and correct scatter in cone beam computed tomography(CBCT). However, half of the signal in each projection is blocked by the grid. A synchronized moving grid (Smog) has been proposed to acquire two complimentary projections at each gantry position and merge them into one complete projection. That approach, however, suffers from increased scanning time and the technical difficulty of accurately merging the two projections per gantry angle. Herein, the authors present a new Smog approach which acquires a single projection per gantry angle, with complimentary grid patterns for any two adjacent projections, and use an interprojection sensor fusion (IPSF) technique to estimate the blocked signal in each projection. The method may have the additional benefit of reduced imagingdose due to the grid blocking half of the incident radiation. Methods: The IPSF considers multiple paired observations from two adjacent gantry angles as approximations of the blocked signal and uses a weighted least square regression of these observations to finally determine the blocked signal. The method was first tested with a simulated Smog on a head phantom. The signal to noise ratio (SNR), which represents the difference of the recovered CBCTimage to the original image without the Smog, was used to evaluate the ability of the IPSF in recovering the missing signal. The IPSF approach was then tested using a Catphan phantom on a prototype Smog assembly installed in a bench top CBCT system. Results: In the simulated Smog experiment, the SNRs were increased from 15.1 and 12.7 dB to 35.6 and 28.9 dB comparing with a conventional interpolation method (inpainting method) for a projection and the reconstructed 3D image, respectively, suggesting that IPSF successfully recovered most of blocked signal. In the prototype Smog experiment, the authors have successfully reconstructed a CBCTimage using the IPSF-Smog approach. The detailed geometric features in the Catphan phantom were mostly recovered according to visual evaluation. The scatter related artifacts, such as cupping artifacts, were almost completely removed. Conclusions: The IPSF-Smog is promising in reducing scatter artifacts and improving image quality while reducing radiationdose.

  • we ef 207 04 an inter projection sensor fusion ipsf approach to estimate missing projection signal in synchronized moving grid Smog system
    Medical Physics, 2015
    Co-Authors: L Ren, V Kong, W Giles, You Zhang, Hong Zhang
    Abstract:

    Purpose: A synchronized moving grid (Smog) has been proposed to reduce scatter and lag artifacts in cone beam computed tomography (CBCT). However, information is missing in each projection because certain areas are blocked by the grid. A previous solution to this issue is acquiring 2 complimentary projections at each position, which increases scanning time. This study reports our first Result using an inter-projection sensor fusion (IPSF) method to estimate missing projection in our prototype Smog-based CBCT system. Methods: An in-house Smog assembling with a 1:1 grid of 3 mm gap has been installed in a CBCT benchtop. The grid moves back and forth in a 3-mm amplitude and up-to 20-Hz frequency. A control program in LabView synchronizes the grid motion with the platform rotation and x-ray firing so that the grid patterns for any two neighboring projections are complimentary. A Catphan was scanned with 360 projections. After scatter correction, the IPSF algorithm was applied to estimate missing signal for each projection using the information from the 2 neighboring projections. Feldkamp-Davis-Kress (FDK) algorithm was applied to reconstruct CBCT images. The CBCTs were compared to those reconstructed using normal projections without applying the Smog system. Results: The Smog-IPSF method may reduce image dose by half due to the blocked radiation by the grid. The method almost completely removed scatter related artifacts, such as the cupping artifacts. The evaluation of line pair patterns in the CatPhan suggested that the spatial resolution degradation was minimal. Conclusion: The Smog-IPSF is promising in reducing scatter artifacts and improving image quality while reducing radiation dose.

  • we ef 207 08 improve cone beam ct using a synchronized moving grid an inter projection sensor fusion and a probability total variation reconstruction
    Medical Physics, 2015
    Co-Authors: L Ren, V Kong, W Giles, You Zhang, Hong Zhang
    Abstract:

    Purpose: To present a cone beam computed tomography (CBCT) system, which uses a synchronized moving grid (Smog) to reduce and correct scatter, an inter-projection sensor fusion (IPSF) algorithm to estimate the missing information blocked by the grid, and a probability total variation (pTV) algorithm to reconstruct the CBCT image. Methods: A prototype Smog-equipped CBCT system was developed, and was used to acquire gridded projections with complimentary grid patterns in two neighboring projections. Scatter was reduced by the grid, and the remaining scatter was corrected by measuring it under the grid. An IPSF algorithm was used to estimate the missing information in a projection from data in its 2 neighboring projections. Feldkamp-Davis-Kress (FDK) algorithm was used to reconstruct the initial CBCT image using projections after IPSF processing for pTV. A probability map was generated depending on the confidence of estimation in IPSF for the regions of missing data and penumbra. pTV was finally used to reconstruct the CBCT image for a Catphan, and was compared to conventional CBCT image without using Smog, images without using IPSF (Smog + FDK and Smog + mask-TV), and image without using pTV (Smog + IPSF + FDK). Results: The conventional CBCT without using Smog shows apparent scatter-induced cup artifacts. The approaches with Smog but without IPSF show severe (Smog + FDK) or additional (Smog + TV) artifacts, possibly due to using projections of missing data. The 2 approaches with Smog + IPSF removes the cup artifacts, and the pTV approach is superior than the FDK by substantially reducing the noise. Using the Smog also reduces half of the imaging dose. Conclusion: The proposed technique is promising in improving CBCT image quality while reducing imaging dose.

  • feasibility study of a synchronized moving grid Smog system to improve image quality in cone beam computed tomography cbct
    Medical Physics, 2012
    Co-Authors: L Ren, Indrin J Chetty, F. Yin, David A. Jaffray, Jian Yue Jin
    Abstract:

    Purpose: To evaluate the feasibility of a synchronized moving grid (Smog) system to remove scatter artifacts, improve the contrast-to-noise ratio (CNR), and reduce image lag artifacts in cone-beam CT (CBCT). Methods: The Smog system proposed here uses a rapidly oscillating, synchronized moving grid attached to the kV source. Multiple partial projections are taken at different grid positions to form a complete projection in each gantry position, before the gantry moves to the next position during a scan. The grid has a low transmission factor, and it is used for both scatter reduction and scatter measurement for postscan scatter correction. Experimental studies using a static grid and an enlarged CATphan phantom were performed to evaluate the potential CNR enhancement for different Smog exposure numbers (1, 2, and 4). Simulation studies were performed to evaluate the image lag correction for different exposure numbers (2, 3, and 4) and grid interspace widths in Smog using the data from an anthropomorphic pelvis phantom scan. Imaging dose of Smog was also estimated by measuring the imaging dose in a CIRS CT dose phantom using a static grid. Results: Smog can enhance the CNR by 16% and 13% when increasing exposure number from 1 to 2more » and from 2 to 4, respectively. This enhancement was more dramatic for larger phantoms and smaller initial exposure numbers. Simulation results indicated that Smog could reduce the lag to less than 4.3% for 2-exposure mode and to less than 0.8% for 3-exposure mode when the grid interspace width was 1.4 cm. Increasing the number of exposures in Smog dramatically reduced the residual lag in the image. Reducing the grid interspace width somewhat reduced the residual lag. Skin line artifacts were removed entirely in Smog. Point dose measurement showed that imaging dose of Smog at isocenter was similar as that of a conventional CBCT. Conclusions: Compared to our previously developed static-grid dual-rotation method, the proposed Smog technique has the advantages of enhancing the CNR, correcting the image lag, and reducing the delivery time. Once implemented, Smog has the potential to remove scatter and image lag artifacts, and significantly enhance CNR for CBCT using the same scanning time as conventional CBCT.« less

  • tu a 213cd 02 contrast to noise ratio cnr enhancement and lag correction in cone beam ct cbct using a synchronized moving grid Smog system
    Medical Physics, 2012
    Co-Authors: L Ren, J Jin, F. Yin
    Abstract:

    Purpose: To develop a synchronized moving grid (Smog) system to enhance the contrast‐to‐noise ratio (CNR) and correct image lag in cone‐beam CT(CBCT).Methods: The Smog system uses a rapidly oscillating, synchronized moving grid attached to the kV source. Multiple exposures are taken at each gantry angle with the grid offset by a distance equal to the grid interspace width after each exposure, before the gantry moves to the next position during a scan. In each projection image, patient image data are acquired within the grid interspace area and scatter is measured under the area blocked by the grid for post‐scan scatter correction. The grid provides direct scatter reduction by blocking part of the beam, which enhances CNR in the reconstructedCBCTimages.Image lag was also estimated from the blocked area and used for lag correction in the image area since both areas have similar radiation history during Smog acquisition. Experimental studies were performed to evaluate the CNR enhancement for different numbers of exposures (1, 2, and 4) taken at each gantry angle using an enlarged CATphan. Simulation studies were performed to evaluate the lag correction using a lag model. Results: Experimental results showed that Smog enhanced the CNR by 16% and 13% when increasing exposure number from 1 to 2 and from 2 to 4, respectively. This enhancement was more dramatic for large phantoms. The gain in CNR by increasing the exposure number gradually diminished as the exposure number became large. The CNR values from 4‐exposure Smog were similar to those from the quasi‐fan beam scan. Simulation results showed that image lag was reduced from 19% to 0.6% using 4‐exposure Smog.Conclusions:Smog has the advantages of substantially enhancing the CNR and correcting image lag while removing the scatter artifacts in CBCT with similar scanning time and imaging dose as conventional CBCT.

W Giles - One of the best experts on this subject based on the ideXlab platform.

  • an interprojection sensor fusion approach to estimate blocked projection signal in synchronized moving grid based cbct system
    Medical Physics, 2015
    Co-Authors: Hong Zhang, L Ren, V Kong, W Giles, You Zhang, Jian Yue Jin
    Abstract:

    Purpose: A preobject grid can reduce and correct scatter in cone beam computed tomography(CBCT). However, half of the signal in each projection is blocked by the grid. A synchronized moving grid (Smog) has been proposed to acquire two complimentary projections at each gantry position and merge them into one complete projection. That approach, however, suffers from increased scanning time and the technical difficulty of accurately merging the two projections per gantry angle. Herein, the authors present a new Smog approach which acquires a single projection per gantry angle, with complimentary grid patterns for any two adjacent projections, and use an interprojection sensor fusion (IPSF) technique to estimate the blocked signal in each projection. The method may have the additional benefit of reduced imagingdose due to the grid blocking half of the incident radiation. Methods: The IPSF considers multiple paired observations from two adjacent gantry angles as approximations of the blocked signal and uses a weighted least square regression of these observations to finally determine the blocked signal. The method was first tested with a simulated Smog on a head phantom. The signal to noise ratio (SNR), which represents the difference of the recovered CBCTimage to the original image without the Smog, was used to evaluate the ability of the IPSF in recovering the missing signal. The IPSF approach was then tested using a Catphan phantom on a prototype Smog assembly installed in a bench top CBCT system. Results: In the simulated Smog experiment, the SNRs were increased from 15.1 and 12.7 dB to 35.6 and 28.9 dB comparing with a conventional interpolation method (inpainting method) for a projection and the reconstructed 3D image, respectively, suggesting that IPSF successfully recovered most of blocked signal. In the prototype Smog experiment, the authors have successfully reconstructed a CBCTimage using the IPSF-Smog approach. The detailed geometric features in the Catphan phantom were mostly recovered according to visual evaluation. The scatter related artifacts, such as cupping artifacts, were almost completely removed. Conclusions: The IPSF-Smog is promising in reducing scatter artifacts and improving image quality while reducing radiationdose.

  • we ef 207 04 an inter projection sensor fusion ipsf approach to estimate missing projection signal in synchronized moving grid Smog system
    Medical Physics, 2015
    Co-Authors: L Ren, V Kong, W Giles, You Zhang, Hong Zhang
    Abstract:

    Purpose: A synchronized moving grid (Smog) has been proposed to reduce scatter and lag artifacts in cone beam computed tomography (CBCT). However, information is missing in each projection because certain areas are blocked by the grid. A previous solution to this issue is acquiring 2 complimentary projections at each position, which increases scanning time. This study reports our first Result using an inter-projection sensor fusion (IPSF) method to estimate missing projection in our prototype Smog-based CBCT system. Methods: An in-house Smog assembling with a 1:1 grid of 3 mm gap has been installed in a CBCT benchtop. The grid moves back and forth in a 3-mm amplitude and up-to 20-Hz frequency. A control program in LabView synchronizes the grid motion with the platform rotation and x-ray firing so that the grid patterns for any two neighboring projections are complimentary. A Catphan was scanned with 360 projections. After scatter correction, the IPSF algorithm was applied to estimate missing signal for each projection using the information from the 2 neighboring projections. Feldkamp-Davis-Kress (FDK) algorithm was applied to reconstruct CBCT images. The CBCTs were compared to those reconstructed using normal projections without applying the Smog system. Results: The Smog-IPSF method may reduce image dose by half due to the blocked radiation by the grid. The method almost completely removed scatter related artifacts, such as the cupping artifacts. The evaluation of line pair patterns in the CatPhan suggested that the spatial resolution degradation was minimal. Conclusion: The Smog-IPSF is promising in reducing scatter artifacts and improving image quality while reducing radiation dose.

  • we ef 207 08 improve cone beam ct using a synchronized moving grid an inter projection sensor fusion and a probability total variation reconstruction
    Medical Physics, 2015
    Co-Authors: L Ren, V Kong, W Giles, You Zhang, Hong Zhang
    Abstract:

    Purpose: To present a cone beam computed tomography (CBCT) system, which uses a synchronized moving grid (Smog) to reduce and correct scatter, an inter-projection sensor fusion (IPSF) algorithm to estimate the missing information blocked by the grid, and a probability total variation (pTV) algorithm to reconstruct the CBCT image. Methods: A prototype Smog-equipped CBCT system was developed, and was used to acquire gridded projections with complimentary grid patterns in two neighboring projections. Scatter was reduced by the grid, and the remaining scatter was corrected by measuring it under the grid. An IPSF algorithm was used to estimate the missing information in a projection from data in its 2 neighboring projections. Feldkamp-Davis-Kress (FDK) algorithm was used to reconstruct the initial CBCT image using projections after IPSF processing for pTV. A probability map was generated depending on the confidence of estimation in IPSF for the regions of missing data and penumbra. pTV was finally used to reconstruct the CBCT image for a Catphan, and was compared to conventional CBCT image without using Smog, images without using IPSF (Smog + FDK and Smog + mask-TV), and image without using pTV (Smog + IPSF + FDK). Results: The conventional CBCT without using Smog shows apparent scatter-induced cup artifacts. The approaches with Smog but without IPSF show severe (Smog + FDK) or additional (Smog + TV) artifacts, possibly due to using projections of missing data. The 2 approaches with Smog + IPSF removes the cup artifacts, and the pTV approach is superior than the FDK by substantially reducing the noise. Using the Smog also reduces half of the imaging dose. Conclusion: The proposed technique is promising in improving CBCT image quality while reducing imaging dose.

Hong Zhang - One of the best experts on this subject based on the ideXlab platform.

  • an interprojection sensor fusion approach to estimate blocked projection signal in synchronized moving grid based cbct system
    Medical Physics, 2015
    Co-Authors: Hong Zhang, L Ren, V Kong, W Giles, You Zhang, Jian Yue Jin
    Abstract:

    Purpose: A preobject grid can reduce and correct scatter in cone beam computed tomography(CBCT). However, half of the signal in each projection is blocked by the grid. A synchronized moving grid (Smog) has been proposed to acquire two complimentary projections at each gantry position and merge them into one complete projection. That approach, however, suffers from increased scanning time and the technical difficulty of accurately merging the two projections per gantry angle. Herein, the authors present a new Smog approach which acquires a single projection per gantry angle, with complimentary grid patterns for any two adjacent projections, and use an interprojection sensor fusion (IPSF) technique to estimate the blocked signal in each projection. The method may have the additional benefit of reduced imagingdose due to the grid blocking half of the incident radiation. Methods: The IPSF considers multiple paired observations from two adjacent gantry angles as approximations of the blocked signal and uses a weighted least square regression of these observations to finally determine the blocked signal. The method was first tested with a simulated Smog on a head phantom. The signal to noise ratio (SNR), which represents the difference of the recovered CBCTimage to the original image without the Smog, was used to evaluate the ability of the IPSF in recovering the missing signal. The IPSF approach was then tested using a Catphan phantom on a prototype Smog assembly installed in a bench top CBCT system. Results: In the simulated Smog experiment, the SNRs were increased from 15.1 and 12.7 dB to 35.6 and 28.9 dB comparing with a conventional interpolation method (inpainting method) for a projection and the reconstructed 3D image, respectively, suggesting that IPSF successfully recovered most of blocked signal. In the prototype Smog experiment, the authors have successfully reconstructed a CBCTimage using the IPSF-Smog approach. The detailed geometric features in the Catphan phantom were mostly recovered according to visual evaluation. The scatter related artifacts, such as cupping artifacts, were almost completely removed. Conclusions: The IPSF-Smog is promising in reducing scatter artifacts and improving image quality while reducing radiationdose.

  • we ef 207 04 an inter projection sensor fusion ipsf approach to estimate missing projection signal in synchronized moving grid Smog system
    Medical Physics, 2015
    Co-Authors: L Ren, V Kong, W Giles, You Zhang, Hong Zhang
    Abstract:

    Purpose: A synchronized moving grid (Smog) has been proposed to reduce scatter and lag artifacts in cone beam computed tomography (CBCT). However, information is missing in each projection because certain areas are blocked by the grid. A previous solution to this issue is acquiring 2 complimentary projections at each position, which increases scanning time. This study reports our first Result using an inter-projection sensor fusion (IPSF) method to estimate missing projection in our prototype Smog-based CBCT system. Methods: An in-house Smog assembling with a 1:1 grid of 3 mm gap has been installed in a CBCT benchtop. The grid moves back and forth in a 3-mm amplitude and up-to 20-Hz frequency. A control program in LabView synchronizes the grid motion with the platform rotation and x-ray firing so that the grid patterns for any two neighboring projections are complimentary. A Catphan was scanned with 360 projections. After scatter correction, the IPSF algorithm was applied to estimate missing signal for each projection using the information from the 2 neighboring projections. Feldkamp-Davis-Kress (FDK) algorithm was applied to reconstruct CBCT images. The CBCTs were compared to those reconstructed using normal projections without applying the Smog system. Results: The Smog-IPSF method may reduce image dose by half due to the blocked radiation by the grid. The method almost completely removed scatter related artifacts, such as the cupping artifacts. The evaluation of line pair patterns in the CatPhan suggested that the spatial resolution degradation was minimal. Conclusion: The Smog-IPSF is promising in reducing scatter artifacts and improving image quality while reducing radiation dose.

  • we ef 207 08 improve cone beam ct using a synchronized moving grid an inter projection sensor fusion and a probability total variation reconstruction
    Medical Physics, 2015
    Co-Authors: L Ren, V Kong, W Giles, You Zhang, Hong Zhang
    Abstract:

    Purpose: To present a cone beam computed tomography (CBCT) system, which uses a synchronized moving grid (Smog) to reduce and correct scatter, an inter-projection sensor fusion (IPSF) algorithm to estimate the missing information blocked by the grid, and a probability total variation (pTV) algorithm to reconstruct the CBCT image. Methods: A prototype Smog-equipped CBCT system was developed, and was used to acquire gridded projections with complimentary grid patterns in two neighboring projections. Scatter was reduced by the grid, and the remaining scatter was corrected by measuring it under the grid. An IPSF algorithm was used to estimate the missing information in a projection from data in its 2 neighboring projections. Feldkamp-Davis-Kress (FDK) algorithm was used to reconstruct the initial CBCT image using projections after IPSF processing for pTV. A probability map was generated depending on the confidence of estimation in IPSF for the regions of missing data and penumbra. pTV was finally used to reconstruct the CBCT image for a Catphan, and was compared to conventional CBCT image without using Smog, images without using IPSF (Smog + FDK and Smog + mask-TV), and image without using pTV (Smog + IPSF + FDK). Results: The conventional CBCT without using Smog shows apparent scatter-induced cup artifacts. The approaches with Smog but without IPSF show severe (Smog + FDK) or additional (Smog + TV) artifacts, possibly due to using projections of missing data. The 2 approaches with Smog + IPSF removes the cup artifacts, and the pTV approach is superior than the FDK by substantially reducing the noise. Using the Smog also reduces half of the imaging dose. Conclusion: The proposed technique is promising in improving CBCT image quality while reducing imaging dose.

F. Yin - One of the best experts on this subject based on the ideXlab platform.

  • feasibility study of a synchronized moving grid Smog system to improve image quality in cone beam computed tomography cbct
    Medical Physics, 2012
    Co-Authors: L Ren, Indrin J Chetty, F. Yin, David A. Jaffray, Jian Yue Jin
    Abstract:

    Purpose: To evaluate the feasibility of a synchronized moving grid (Smog) system to remove scatter artifacts, improve the contrast-to-noise ratio (CNR), and reduce image lag artifacts in cone-beam CT (CBCT). Methods: The Smog system proposed here uses a rapidly oscillating, synchronized moving grid attached to the kV source. Multiple partial projections are taken at different grid positions to form a complete projection in each gantry position, before the gantry moves to the next position during a scan. The grid has a low transmission factor, and it is used for both scatter reduction and scatter measurement for postscan scatter correction. Experimental studies using a static grid and an enlarged CATphan phantom were performed to evaluate the potential CNR enhancement for different Smog exposure numbers (1, 2, and 4). Simulation studies were performed to evaluate the image lag correction for different exposure numbers (2, 3, and 4) and grid interspace widths in Smog using the data from an anthropomorphic pelvis phantom scan. Imaging dose of Smog was also estimated by measuring the imaging dose in a CIRS CT dose phantom using a static grid. Results: Smog can enhance the CNR by 16% and 13% when increasing exposure number from 1 to 2more » and from 2 to 4, respectively. This enhancement was more dramatic for larger phantoms and smaller initial exposure numbers. Simulation results indicated that Smog could reduce the lag to less than 4.3% for 2-exposure mode and to less than 0.8% for 3-exposure mode when the grid interspace width was 1.4 cm. Increasing the number of exposures in Smog dramatically reduced the residual lag in the image. Reducing the grid interspace width somewhat reduced the residual lag. Skin line artifacts were removed entirely in Smog. Point dose measurement showed that imaging dose of Smog at isocenter was similar as that of a conventional CBCT. Conclusions: Compared to our previously developed static-grid dual-rotation method, the proposed Smog technique has the advantages of enhancing the CNR, correcting the image lag, and reducing the delivery time. Once implemented, Smog has the potential to remove scatter and image lag artifacts, and significantly enhance CNR for CBCT using the same scanning time as conventional CBCT.« less

  • tu a 213cd 02 contrast to noise ratio cnr enhancement and lag correction in cone beam ct cbct using a synchronized moving grid Smog system
    Medical Physics, 2012
    Co-Authors: L Ren, J Jin, F. Yin
    Abstract:

    Purpose: To develop a synchronized moving grid (Smog) system to enhance the contrast‐to‐noise ratio (CNR) and correct image lag in cone‐beam CT(CBCT).Methods: The Smog system uses a rapidly oscillating, synchronized moving grid attached to the kV source. Multiple exposures are taken at each gantry angle with the grid offset by a distance equal to the grid interspace width after each exposure, before the gantry moves to the next position during a scan. In each projection image, patient image data are acquired within the grid interspace area and scatter is measured under the area blocked by the grid for post‐scan scatter correction. The grid provides direct scatter reduction by blocking part of the beam, which enhances CNR in the reconstructedCBCTimages.Image lag was also estimated from the blocked area and used for lag correction in the image area since both areas have similar radiation history during Smog acquisition. Experimental studies were performed to evaluate the CNR enhancement for different numbers of exposures (1, 2, and 4) taken at each gantry angle using an enlarged CATphan. Simulation studies were performed to evaluate the lag correction using a lag model. Results: Experimental results showed that Smog enhanced the CNR by 16% and 13% when increasing exposure number from 1 to 2 and from 2 to 4, respectively. This enhancement was more dramatic for large phantoms. The gain in CNR by increasing the exposure number gradually diminished as the exposure number became large. The CNR values from 4‐exposure Smog were similar to those from the quasi‐fan beam scan. Simulation results showed that image lag was reduced from 19% to 0.6% using 4‐exposure Smog.Conclusions:Smog has the advantages of substantially enhancing the CNR and correcting image lag while removing the scatter artifacts in CBCT with similar scanning time and imaging dose as conventional CBCT.

Jian Yue Jin - One of the best experts on this subject based on the ideXlab platform.

  • an interprojection sensor fusion approach to estimate blocked projection signal in synchronized moving grid based cbct system
    Medical Physics, 2015
    Co-Authors: Hong Zhang, L Ren, V Kong, W Giles, You Zhang, Jian Yue Jin
    Abstract:

    Purpose: A preobject grid can reduce and correct scatter in cone beam computed tomography(CBCT). However, half of the signal in each projection is blocked by the grid. A synchronized moving grid (Smog) has been proposed to acquire two complimentary projections at each gantry position and merge them into one complete projection. That approach, however, suffers from increased scanning time and the technical difficulty of accurately merging the two projections per gantry angle. Herein, the authors present a new Smog approach which acquires a single projection per gantry angle, with complimentary grid patterns for any two adjacent projections, and use an interprojection sensor fusion (IPSF) technique to estimate the blocked signal in each projection. The method may have the additional benefit of reduced imagingdose due to the grid blocking half of the incident radiation. Methods: The IPSF considers multiple paired observations from two adjacent gantry angles as approximations of the blocked signal and uses a weighted least square regression of these observations to finally determine the blocked signal. The method was first tested with a simulated Smog on a head phantom. The signal to noise ratio (SNR), which represents the difference of the recovered CBCTimage to the original image without the Smog, was used to evaluate the ability of the IPSF in recovering the missing signal. The IPSF approach was then tested using a Catphan phantom on a prototype Smog assembly installed in a bench top CBCT system. Results: In the simulated Smog experiment, the SNRs were increased from 15.1 and 12.7 dB to 35.6 and 28.9 dB comparing with a conventional interpolation method (inpainting method) for a projection and the reconstructed 3D image, respectively, suggesting that IPSF successfully recovered most of blocked signal. In the prototype Smog experiment, the authors have successfully reconstructed a CBCTimage using the IPSF-Smog approach. The detailed geometric features in the Catphan phantom were mostly recovered according to visual evaluation. The scatter related artifacts, such as cupping artifacts, were almost completely removed. Conclusions: The IPSF-Smog is promising in reducing scatter artifacts and improving image quality while reducing radiationdose.

  • feasibility study of a synchronized moving grid Smog system to improve image quality in cone beam computed tomography cbct
    Medical Physics, 2012
    Co-Authors: L Ren, Indrin J Chetty, F. Yin, David A. Jaffray, Jian Yue Jin
    Abstract:

    Purpose: To evaluate the feasibility of a synchronized moving grid (Smog) system to remove scatter artifacts, improve the contrast-to-noise ratio (CNR), and reduce image lag artifacts in cone-beam CT (CBCT). Methods: The Smog system proposed here uses a rapidly oscillating, synchronized moving grid attached to the kV source. Multiple partial projections are taken at different grid positions to form a complete projection in each gantry position, before the gantry moves to the next position during a scan. The grid has a low transmission factor, and it is used for both scatter reduction and scatter measurement for postscan scatter correction. Experimental studies using a static grid and an enlarged CATphan phantom were performed to evaluate the potential CNR enhancement for different Smog exposure numbers (1, 2, and 4). Simulation studies were performed to evaluate the image lag correction for different exposure numbers (2, 3, and 4) and grid interspace widths in Smog using the data from an anthropomorphic pelvis phantom scan. Imaging dose of Smog was also estimated by measuring the imaging dose in a CIRS CT dose phantom using a static grid. Results: Smog can enhance the CNR by 16% and 13% when increasing exposure number from 1 to 2more » and from 2 to 4, respectively. This enhancement was more dramatic for larger phantoms and smaller initial exposure numbers. Simulation results indicated that Smog could reduce the lag to less than 4.3% for 2-exposure mode and to less than 0.8% for 3-exposure mode when the grid interspace width was 1.4 cm. Increasing the number of exposures in Smog dramatically reduced the residual lag in the image. Reducing the grid interspace width somewhat reduced the residual lag. Skin line artifacts were removed entirely in Smog. Point dose measurement showed that imaging dose of Smog at isocenter was similar as that of a conventional CBCT. Conclusions: Compared to our previously developed static-grid dual-rotation method, the proposed Smog technique has the advantages of enhancing the CNR, correcting the image lag, and reducing the delivery time. Once implemented, Smog has the potential to remove scatter and image lag artifacts, and significantly enhance CNR for CBCT using the same scanning time as conventional CBCT.« less