skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: SU-F-J-54: Towards Real-Time Volumetric Imaging Using the Treatment Beam and KV Beam

Abstract

Purpose: Existing real-time imaging uses dual (orthogonal) kV beam fluoroscopies and may result in significant amount of extra radiation to patients, especially for prolonged treatment cases. In addition, kV projections only provide 2D information, which is insufficient for in vivo dose reconstruction. We propose real-time volumetric imaging using prior knowledge of pre-treatment 4D images and real-time 2D transit data of treatment beam and kV beam. Methods: The pre-treatment multi-snapshot volumetric images are used to simulate 2D projections of both the treatment beam and kV beam, respectively, for each treatment field defined by the control point. During radiation delivery, the transit signals acquired by the electronic portal image device (EPID) are processed for every projection and compared with pre-calculation by cross-correlation for phase matching and thus 3D snapshot identification or real-time volumetric imaging. The data processing involves taking logarithmic ratios of EPID signals with respect to the air scan to reduce modeling uncertainties in head scatter fluence and EPID response. Simulated 2D projections are also used to pre-calculate confidence levels in phase matching. Treatment beam projections that have a low confidence level either in pre-calculation or real-time acquisition will trigger kV beams so that complementary information can be exploited. In casemore » both the treatment beam and kV beam return low confidence in phase matching, a predicted phase based on linear regression will be generated. Results: Simulation studies indicated treatment beams provide sufficient confidence in phase matching for most cases. At times of low confidence from treatment beams, kV imaging provides sufficient confidence in phase matching due to its complementary configuration. Conclusion: The proposed real-time volumetric imaging utilizes the treatment beam and triggers kV beams for complementary information when the treatment beam along does not provide sufficient confidence for phase matching. This strategy minimizes the use of extra radiation to patients. This project is partially supported by a Varian MRA grant.« less

Authors:
; ; ; ;  [1]
  1. UT Southwestern Medical Center, Dallas, TX (United States)
Publication Date:
OSTI Identifier:
22632186
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; BEAMS; DATA PROCESSING; FLUOROSCOPY; IMAGES; IN VIVO; PATIENTS; RADIATION DOSES; SIMULATION

Citation Formats

Chen, M, Rozario, T, Liu, A, Jiang, S, and Lu, W. SU-F-J-54: Towards Real-Time Volumetric Imaging Using the Treatment Beam and KV Beam. United States: N. p., 2016. Web. doi:10.1118/1.4955962.
Chen, M, Rozario, T, Liu, A, Jiang, S, & Lu, W. SU-F-J-54: Towards Real-Time Volumetric Imaging Using the Treatment Beam and KV Beam. United States. doi:10.1118/1.4955962.
Chen, M, Rozario, T, Liu, A, Jiang, S, and Lu, W. 2016. "SU-F-J-54: Towards Real-Time Volumetric Imaging Using the Treatment Beam and KV Beam". United States. doi:10.1118/1.4955962.
@article{osti_22632186,
title = {SU-F-J-54: Towards Real-Time Volumetric Imaging Using the Treatment Beam and KV Beam},
author = {Chen, M and Rozario, T and Liu, A and Jiang, S and Lu, W},
abstractNote = {Purpose: Existing real-time imaging uses dual (orthogonal) kV beam fluoroscopies and may result in significant amount of extra radiation to patients, especially for prolonged treatment cases. In addition, kV projections only provide 2D information, which is insufficient for in vivo dose reconstruction. We propose real-time volumetric imaging using prior knowledge of pre-treatment 4D images and real-time 2D transit data of treatment beam and kV beam. Methods: The pre-treatment multi-snapshot volumetric images are used to simulate 2D projections of both the treatment beam and kV beam, respectively, for each treatment field defined by the control point. During radiation delivery, the transit signals acquired by the electronic portal image device (EPID) are processed for every projection and compared with pre-calculation by cross-correlation for phase matching and thus 3D snapshot identification or real-time volumetric imaging. The data processing involves taking logarithmic ratios of EPID signals with respect to the air scan to reduce modeling uncertainties in head scatter fluence and EPID response. Simulated 2D projections are also used to pre-calculate confidence levels in phase matching. Treatment beam projections that have a low confidence level either in pre-calculation or real-time acquisition will trigger kV beams so that complementary information can be exploited. In case both the treatment beam and kV beam return low confidence in phase matching, a predicted phase based on linear regression will be generated. Results: Simulation studies indicated treatment beams provide sufficient confidence in phase matching for most cases. At times of low confidence from treatment beams, kV imaging provides sufficient confidence in phase matching due to its complementary configuration. Conclusion: The proposed real-time volumetric imaging utilizes the treatment beam and triggers kV beams for complementary information when the treatment beam along does not provide sufficient confidence for phase matching. This strategy minimizes the use of extra radiation to patients. This project is partially supported by a Varian MRA grant.},
doi = {10.1118/1.4955962},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = 2016,
month = 6
}
  • The Dynamic Analysis (DA) method, for the projection of quantitative elemental images using Proton Induced X-ray Emission (PIXE), has been extended for use with energy-dispersive Synchrotron X-ray Fluorescence (SXRF) data collected with the X-ray microprobe by making use of similarities and synergy with nuclear microscopy. The broad element sensitivity of PIXE is complemented by the selective nature of SXRF, where the beam energy can be tuned to optimize the sensitivity in a portion of the periodic table. PIXE combined with Proton Induced {gamma}-ray Emission (PIGE) in this study provided images of geological samples of 25 elements, including characteristic X-rays upmore » to the energy of the Nd K lines (37 keV). Maximum sensitivity was achieved for elements around Z {approx} 33 with detection limits of {approx}250 ppb (in 5 h). SXRF using a 16.1 keV photon microbeam provided images of 16 elements, with optimum sensitivity around Z {approx} 35 with detection limits of {approx}70 ppb (in 11 h), an improvement of {approx}2.4 times when corrected for acquisition time.« less
  • Purpose: To expedite on-board volumetric image reconstruction from limited-angle kV—MV projections for intrafraction verification. Methods: A limited-angle intrafraction verification (LIVE) system has recently been developed for real-time volumetric verification of moving targets, using limited-angle kV—MV projections. Currently, it is challenged by the intensive computational load of the prior-knowledge-based reconstruction method. To accelerate LIVE, we restructure the software pipeline to make it adaptable to model and algorithm parameter changes, while enabling efficient utilization of rapidly advancing, modern computer architectures. In particular, an innovative two-level parallelization scheme has been designed: At the macroscopic level, data and operations are adaptively partitioned, taking intomore » account algorithmic parameters and the processing capacity or constraints of underlying hardware. The control and data flows of the pipeline are scheduled in such a way as to maximize operation concurrency and minimize total processing time. At the microscopic level, the partitioned functions act as independent modules, operating on data partitions in parallel. Each module is pre-parallelized and optimized for multi-core processors (CPUs) and graphics processing units (GPUs). Results: We present results from a parallel prototype, where most of the controls and module parallelization are carried out via Matlab and its Parallel Computing Toolbox. The reconstruction is 5 times faster on a data-set of twice the size, compared to recently reported results, without compromising on algorithmic optimization control. Conclusion: The prototype implementation and its results have served to assess the efficacy of our system concept. While a production implementation will yield much higher processing rates by approaching full-capacity utilization of CPUs and GPUs, some mutual constraints between algorithmic flow and architecture specifics remain. Based on a careful analysis of the prototype performance, it will be feasible to resolve such issues through appropriate algorithmic modifications or special-purpose hardware, thus enabling target verification in seconds with the LIVE system. This work was partially supported by a research grant from Varian Medical Systems.« less
  • Purpose: To utilize image-guided radiotherapy (IGRT) in near real time by obtaining and evaluating the online positions of implanted fiducials from continuous electronic portal imaging device (EPID) imaging of prostate intensity-modulated radiotherapy (IMRT) delivery. Methods and Materials: Upon initial setup using two orthogonal images, the three-dimensional (3D) positions of all implanted fiducial markers are obtained, and their expected two-dimensional (2D) locations in the beam's-eye-view (BEV) projection are calculated for each treatment field. During IMRT beam delivery, EPID images of the megavoltage treatment beam are acquired in cine mode and subsequently analyzed to locate 2D locations of fiducials in the BEV.more » Simultaneously, 3D positions are estimated according to the current EPID image, information from the setup portal images, and images acquired at other gantry angles (the completed treatment fields). The measured 2D and 3D positions of each fiducial are compared with their expected 2D and 3D setup positions, respectively. Any displacements larger than a predefined tolerance may cause the treatment system to suspend the beam delivery and direct the therapists to reposition the patient. Results: Phantom studies indicate that the accuracy of 2D BEV and 3D tracking are better than 1 mm and 1.4 mm, respectively. A total of 7330 images from prostate treatments were acquired and analyzed, showing a maximum 2D displacement of 6.7 mm and a maximum 3D displacement of 6.9 mm over 34 fractions. Conclusions: This EPID-based, real-time IGRT method can be implemented on any external beam machine with portal imaging capabilities without purchasing any additional equipment, and there is no extra dose delivered to the patient.« less
  • Purpose: To identify achievable camera performance and hardware needs in a clinical Cherenkov imaging system for real-time, in vivo monitoring of the surface beam profile on patients, as novel visual information, documentation, and possible treatment verification for clinicians. Methods: Complementary metal-oxide-semiconductor (CMOS), charge-coupled device (CCD), intensified charge-coupled device (ICCD), and electron multiplying-intensified charge coupled device (EM-ICCD) cameras were investigated to determine Cherenkov imaging performance in a clinical radiotherapy setting, with one emphasis on the maximum supportable frame rate. Where possible, the image intensifier was synchronized using a pulse signal from the Linac in order to image with room lighting conditionsmore » comparable to patient treatment scenarios. A solid water phantom irradiated with a 6 MV photon beam was imaged by the cameras to evaluate the maximum frame rate for adequate Cherenkov detection. Adequate detection was defined as an average electron count in the background-subtracted Cherenkov image region of interest in excess of 0.5% (327 counts) of the 16-bit maximum electron count value. Additionally, an ICCD and an EM-ICCD were each used clinically to image two patients undergoing whole-breast radiotherapy to compare clinical advantages and limitations of each system. Results: Intensifier-coupled cameras were required for imaging Cherenkov emission on the phantom surface with ambient room lighting; standalone CMOS and CCD cameras were not viable. The EM-ICCD was able to collect images from a single Linac pulse delivering less than 0.05 cGy of dose at 30 frames/s (fps) and pixel resolution of 512 × 512, compared to an ICCD which was limited to 4.7 fps at 1024 × 1024 resolution. An intensifier with higher quantum efficiency at the entrance photocathode in the red wavelengths [30% quantum efficiency (QE) vs previous 19%] promises at least 8.6 fps at a resolution of 1024 × 1024 and lower monetary cost than the EM-ICCD. Conclusions: The ICCD with an intensifier better optimized for red wavelengths was found to provide the best potential for real-time display (at least 8.6 fps) of radiation dose on the skin during treatment at a resolution of 1024 × 1024.« less
  • Purpose: The scanning beam digital x-ray system (SBDX) is an inverse geometry fluoroscopic system with high dose efficiency and the ability to perform continuous real-time tomosynthesis in multiple planes. This system could be used for image guidance during lung nodule biopsy. However, the reconstructed images suffer from strong out-of-plane artifact due to the small tomographic angle of the system. Methods: The authors propose an out-of-plane artifact subtraction tomosynthesis (OPAST) algorithm that utilizes a prior CT volume to augment the run-time image processing. A blur-and-add (BAA) analytical model, derived from the project-to-backproject physical model, permits the generation of tomosynthesis images thatmore » are a good approximation to the shift-and-add (SAA) reconstructed image. A computationally practical algorithm is proposed to simulate images and out-of-plane artifacts from patient-specific prior CT volumes using the BAA model. A 3D image registration algorithm to align the simulated and reconstructed images is described. The accuracy of the BAA analytical model and the OPAST algorithm was evaluated using three lung cancer patients’ CT data. The OPAST and image registration algorithms were also tested with added nonrigid respiratory motions. Results: Image similarity measurements, including the correlation coefficient, mean squared error, and structural similarity index, indicated that the BAA model is very accurate in simulating the SAA images from the prior CT for the SBDX system. The shift-variant effect of the BAA model can be ignored when the shifts between SBDX images and CT volumes are within ±10 mm in the x and y directions. The nodule visibility and depth resolution are improved by subtracting simulated artifacts from the reconstructions. The image registration and OPAST are robust in the presence of added respiratory motions. The dominant artifacts in the subtraction images are caused by the mismatches between the real object and the prior CT volume. Conclusions: Their proposed prior CT-augmented OPAST reconstruction algorithm improves lung nodule visibility and depth resolution for the SBDX system.« less