Maida Ranjbar - Academia.edu (original) (raw)
Papers by Maida Ranjbar
Lung phantoms are dynamic systems that simulate lung motion to predict tumor position for lung ra... more Lung phantoms are dynamic systems that simulate lung motion to predict tumor position for lung radiotherapy These predictions make cancer radiotherapy more precise, as lung tumors move during breathing Unfortunately, current lung motion phantoms don't account for complex motion and deformation of surrounding organs Now, researchers at the University of Maryland, Baltimore, have developed a lung phantom that can produce complex and irregular motions by using a motion platform with two independently programmable linear actuators The phantom provides reliable measurements of the tumor as well as surrounding organs at risk and can simulate variation in abdominal and thoracic engagement While the new lung phantom can't fully reproduce human breathing, it comes pretty close It is a valuable tool for evaluating motion management strategies in lung radiotherapy Ranjbar et al. "A novel deformable lung phantom with programably variable external and internal correlation." Medical Physics (2019)
Medical Physics, Oct 25, 2019
Purpose: We develop and validate a motion model that uses real-time surface photogrammetry acquir... more Purpose: We develop and validate a motion model that uses real-time surface photogrammetry acquired concurrently with four-dimensional computed tomography (4DCT) to estimate respiration-induced changes within the entire irradiated volume, over arbitrarily many respiratory cycles. Methods: A research, couch-mounted, VisionRT (VRT) system was used to acquire optical surface data (15 Hz, ROI = 15 × 20 cm 2) from the thoraco-abdominal surface of a consented lung SBRT patient, concurrently with their standard-of-care 4DCT. The end-exhalation phase from the 4DCT was regarded as reference and for each remaining phase, deformation vector fields (DVFs) with respect to the reference phase were computed. To reduce dimensionality, the first two principal components (PCs) of the matrix of nine DVFs were calculated. In parallel, ten phaseaveraged VRT surfaces were created. Surface DVFs and corresponding PCs were computed. A principal least squares regression was used to relate the PCs of surface DVF to those of volume DVFs, establishing a relationship between time-varying surface and the underlying time-varying
International Journal of Radiation Oncology Biology Physics, Nov 1, 2020
We propose a novel volumetric surrogate-based motion model (SMM) to address limitations of single... more We propose a novel volumetric surrogate-based motion model (SMM) to address limitations of single cycle respiratory-correlated 4DCT in capturing breathing variations. SMMs are constructed based on the a priori correlation between an external surrogate and the internal motion observed during the planning CT acquisition. Our machine-learning based volumetric SMM exploits the internal-external correlation observed at the time of treatment delivery, minimizing the loss of accuracy resulting from commonly occurring changes in this correlation. We evaluated improvements in target position estimation from our SMM compared to 4DCT by analyzing 2,369 fluoroscopic (FL) images.
Medical Physics, Apr 22, 2019
Purpose: Lung motion phantoms used to validate radiotherapy motion management strategies have fai... more Purpose: Lung motion phantoms used to validate radiotherapy motion management strategies have fairly simplistic designs that do not adequately capture complex phenomena observed in human respiration such as external and internal deformation, variable hysteresis and variable correlation between different parts of the thoracic anatomy. These limitations make reliable evaluation of sophisticated motion management techniques quite challenging. In this work, we present the design and implementation of a programmable, externally and internally deformable lung motion phantom that allows for a reproducible change in external-internal and internal-internal correlation of embedded markers. Methods: An in-house-designed lung module, made from natural latex foam was inserted inside the outer shell of a commercially available lung phantom (RSD, Long Beach, CA, USA). Radiopaque markers were placed on the external surface and embedded into the lung module. Two independently programmable high-precision linear motion actuators were used to generate primarily anterior-posterior (AP) and primarily superior-inferior (SI) motion in a reproducible fashion in order to enable (a) variable correlation between the displacement of interior volume and the exterior surface, (b) independent changes in the amplitude of the AP and SI motions, and (c) variable hysteresis. The ability of the phantom to produce complex and variable motion accurately and reproducibly was evaluated by programming the two actuators with mathematical and patient-recorded lung tumor motion traces, and recording the trajectories of various markers using kV fluoroscopy. As an example application, the phantom was used to evaluate the performance of lung motion models constructed from kV fluoroscopy and 4DCT images. Results: The phantom exhibited a high degree of reproducibility and marker motion ranges were reproducible to within 0.5 mm. Variable correlation was observed between the displacements of internal-internal and internal-external markers. The SI and AP components of motion of a specific marker had a correlation parameter that varied from À11 to 17. Monitoring a region of interest on the phantom's surface to estimate internal marker motion led to considerably lower uncertainties than when a single point was monitored. Conclusions: We successfully designed and implemented a programmable, externally and internally deformable lung motion phantom that allows for a reproducible change in external-internal and internal-internal correlation of embedded markers.
British Journal of Radiology, Mar 1, 2019
A, et al. Mild hyperthermia as a localized radiosensitizer for deep-seated tumors: investigation ... more A, et al. Mild hyperthermia as a localized radiosensitizer for deep-seated tumors: investigation in an orthotopic prostate cancer model in mice.
I would also like to express my gratitude to my defence committee members professors Hanli Liu, a... more I would also like to express my gratitude to my defence committee members professors Hanli Liu, and Michael Cho for their valuable feedback, guidance and time. Additionally, I am thankful to Dr. Rajiv Chopra for having provided me with the opportunity to serve in his research group. Finally, I would like to thank my dearest family and Pouya for their tremendous support over the course of my studies. Their positive reinforcement and encouragement has been my motivation for pushing forward and succeeding.
Physics in Medicine and Biology, Feb 11, 2021
Many surrogate-based motion models (SMMs), proposed to guide motion management in radiotherapy, a... more Many surrogate-based motion models (SMMs), proposed to guide motion management in radiotherapy, are constructed by correlating motion of an external surrogate and internal anatomy during CT-simulation. Changes in this correlation define model break down. We validate a methodology that incorporates fluoroscopic images (FL) acquired during treatment for SMM construction and update. Under a prospective IRB, 4DCT scans, VisionRT 25 surfaces, and orthogonal FLs were collected from five lung cancer patients. VisionRT surfaces and two FL timeseries were acquired pre-and post-treatment. A simulated annealing optimization scheme was used to estimate optimal lung deformations by maximizing the mutual information between digitally reconstructed radiographs (DRRs) of the SMM-estimated 3D images and FLs. Our SMM used partial-least-regression and was trained using the optimal deformations and VisionRT surfaces from the first breathing-cycle. SMM performance was evaluated 30 using the mutual information score between reference FLs and the corresponding SMM or phase-assigned 4DCT DRRs. The Hausdorff distance for contoured landmarks was used to evaluate target position estimation error. For four out of five patients, two principal components approximated lung surface deformations with submillimeter accuracy. Analysis of the mutual information score between more than 4,000 pairs of FL and DRR demonstrated that our model led to more similarity between the FL and DRR images compared to 4DCT and DRR images from 35 a model based on an a priori correlation model. Our SMM consistently displayed lower mean and 95 th percentile Hausdorff distances. For one patient, 95 th percentile Hausdorff distance was reduced by 11mm. Patient-averaged reductions in mean and 95 th percentile Hausdorff distances were 3.6mm and 7mm for right-lung, and 3.1mm and 4mm for left-lung targets. FL data were used to evaluate model performance and investigate the feasibility of model update. Despite variability in breathing, use of post-treatment FL preserved model fidelity and consistently 40 outperformed 4DCT for position estimation.
Advances in Radiation Oncology
مجله دانشکده پزشکی اصفهان, 2012
Background: In this study, we tried to choose the proper material to use on a magnetic resonance ... more Background: In this study, we tried to choose the proper material to use on a magnetic resonance imaging (MRI)-compatible robot. The robot is to take soft tissue samples in an image guided process. Since this robot is made of MRI-compatible material, its links are invisible in the MR images. Finding such markers would enable us to distinguish the position of links in the images and as a result in the real world. Methods: Four materials compatible with magnetic environments, including liquid paraffin, nitroglycerin, vitamin E pills, and silicon oil, were tested to find the most appropriate one to be used as the marker. In addition to compatibility with MRI environment, the material had to have suitable contrast to avoid blurry images. The tests were performed in a Philips MRI system at 1 and 1.5 Tesla. Findings: Liquid paraffin, nitroglycerin, vitamin E pills, and silicon oil scored 50, 62.35, 45.6, and 53.15, respectively. Most of the evaluated factors were satisfied by nitroglyceri...
International Journal of Radiation Oncology*Biology*Physics, 2020
We propose a novel volumetric surrogate-based motion model (SMM) to address limitations of single... more We propose a novel volumetric surrogate-based motion model (SMM) to address limitations of single cycle respiratory-correlated 4DCT in capturing breathing variations. SMMs are constructed based on the a priori correlation between an external surrogate and the internal motion observed during the planning CT acquisition. Our machine-learning based volumetric SMM exploits the internal-external correlation observed at the time of treatment delivery, minimizing the loss of accuracy resulting from commonly occurring changes in this correlation. We evaluated improvements in target position estimation from our SMM compared to 4DCT by analyzing 2,369 fluoroscopic (FL) images.
International Journal of Radiation Oncology Biology Physics, 2020
Medical Physics, 2019
Purpose: We develop and validate a motion model that uses real-time surface photogrammetry acquir... more Purpose: We develop and validate a motion model that uses real-time surface photogrammetry acquired concurrently with four-dimensional computed tomography (4DCT) to estimate respiration-induced changes within the entire irradiated volume, over arbitrarily many respiratory cycles. Methods: A research, couch-mounted, VisionRT (VRT) system was used to acquire optical surface data (15 Hz, ROI = 15 × 20 cm 2) from the thoraco-abdominal surface of a consented lung SBRT patient, concurrently with their standard-of-care 4DCT. The end-exhalation phase from the 4DCT was regarded as reference and for each remaining phase, deformation vector fields (DVFs) with respect to the reference phase were computed. To reduce dimensionality, the first two principal components (PCs) of the matrix of nine DVFs were calculated. In parallel, ten phaseaveraged VRT surfaces were created. Surface DVFs and corresponding PCs were computed. A principal least squares regression was used to relate the PCs of surface DVF to those of volume DVFs, establishing a relationship between time-varying surface and the underlying time-varying
The British Journal of Radiology, 2019
A, et al. Mild hyperthermia as a localized radiosensitizer for deep-seated tumors: investigation ... more A, et al. Mild hyperthermia as a localized radiosensitizer for deep-seated tumors: investigation in an orthotopic prostate cancer model in mice.
Physics in Medicine & Biology, 2021
Many surrogate-based motion models (SMMs), proposed to guide motion management in radiotherapy, a... more Many surrogate-based motion models (SMMs), proposed to guide motion management in radiotherapy, are constructed by correlating motion of an external surrogate and internal anatomy during CT-simulation. Changes in this correlation define model break down. We validate a methodology that incorporates fluoroscopic (FL) images acquired during treatment for SMM construction and update. Under a prospective IRB, 4DCT scans, VisionRT (VRT) surfaces, and orthogonal FLs were collected from five lung cancer patients. VRT surfaces and two FL time-series were acquired pre- and post-treatment. A simulated annealing optimization scheme was used to estimate optimal lung deformations by maximizing the mutual information (MI) between digitally reconstructed radiographs (DRRs) of the SMM-estimated 3D images and FLs. Our SMM used partial-least-regression and was trained using the optimal deformations and VRT surfaces from the first breathing-cycle. SMM performance was evaluated using the MI score betwee...
Manipulating the K-Space for Reduction of Respiratory Induced Motion Artifacts Maida Ranjbar, M.S... more Manipulating the K-Space for Reduction of Respiratory Induced Motion Artifacts Maida Ranjbar, M.Sc. The University of Texas at Arlington, 2016 Supervising Professor: Dr. Ananth Madhuranthakam Respiratory induced motion artifacts, particularly those occurring in the abdomen and lung, pose a hefty problem in current diagnostic MR imaging. Application of images plagued with such artifacts not only hinder diagnosis, but may result in the enforcement of undesirably large safety margins in radiation therapy due to un-captured tumor characteristics that are concealed by the artifact. While several methods such as gated scans, breath-hold scans, variation of the K-Space acquisition trajectory, and reducing the scan time via partial acquisition or parallel imaging have been proposed as a solution, a robust and yet simple to implement remedy still remains to be proposed. This work investigates the application of partial K-Space acquisition/completion methods to correct for motion induced arti...
Lung phantoms are dynamic systems that simulate lung motion to predict tumor position for lung ra... more Lung phantoms are dynamic systems that simulate lung motion to predict tumor position for lung radiotherapy These predictions make cancer radiotherapy more precise, as lung tumors move during breathing Unfortunately, current lung motion phantoms don't account for complex motion and deformation of surrounding organs Now, researchers at the University of Maryland, Baltimore, have developed a lung phantom that can produce complex and irregular motions by using a motion platform with two independently programmable linear actuators The phantom provides reliable measurements of the tumor as well as surrounding organs at risk and can simulate variation in abdominal and thoracic engagement While the new lung phantom can't fully reproduce human breathing, it comes pretty close It is a valuable tool for evaluating motion management strategies in lung radiotherapy Ranjbar et al. "A novel deformable lung phantom with programably variable external and internal correlation." Medical Physics (2019)
Medical Physics, Oct 25, 2019
Purpose: We develop and validate a motion model that uses real-time surface photogrammetry acquir... more Purpose: We develop and validate a motion model that uses real-time surface photogrammetry acquired concurrently with four-dimensional computed tomography (4DCT) to estimate respiration-induced changes within the entire irradiated volume, over arbitrarily many respiratory cycles. Methods: A research, couch-mounted, VisionRT (VRT) system was used to acquire optical surface data (15 Hz, ROI = 15 × 20 cm 2) from the thoraco-abdominal surface of a consented lung SBRT patient, concurrently with their standard-of-care 4DCT. The end-exhalation phase from the 4DCT was regarded as reference and for each remaining phase, deformation vector fields (DVFs) with respect to the reference phase were computed. To reduce dimensionality, the first two principal components (PCs) of the matrix of nine DVFs were calculated. In parallel, ten phaseaveraged VRT surfaces were created. Surface DVFs and corresponding PCs were computed. A principal least squares regression was used to relate the PCs of surface DVF to those of volume DVFs, establishing a relationship between time-varying surface and the underlying time-varying
International Journal of Radiation Oncology Biology Physics, Nov 1, 2020
We propose a novel volumetric surrogate-based motion model (SMM) to address limitations of single... more We propose a novel volumetric surrogate-based motion model (SMM) to address limitations of single cycle respiratory-correlated 4DCT in capturing breathing variations. SMMs are constructed based on the a priori correlation between an external surrogate and the internal motion observed during the planning CT acquisition. Our machine-learning based volumetric SMM exploits the internal-external correlation observed at the time of treatment delivery, minimizing the loss of accuracy resulting from commonly occurring changes in this correlation. We evaluated improvements in target position estimation from our SMM compared to 4DCT by analyzing 2,369 fluoroscopic (FL) images.
Medical Physics, Apr 22, 2019
Purpose: Lung motion phantoms used to validate radiotherapy motion management strategies have fai... more Purpose: Lung motion phantoms used to validate radiotherapy motion management strategies have fairly simplistic designs that do not adequately capture complex phenomena observed in human respiration such as external and internal deformation, variable hysteresis and variable correlation between different parts of the thoracic anatomy. These limitations make reliable evaluation of sophisticated motion management techniques quite challenging. In this work, we present the design and implementation of a programmable, externally and internally deformable lung motion phantom that allows for a reproducible change in external-internal and internal-internal correlation of embedded markers. Methods: An in-house-designed lung module, made from natural latex foam was inserted inside the outer shell of a commercially available lung phantom (RSD, Long Beach, CA, USA). Radiopaque markers were placed on the external surface and embedded into the lung module. Two independently programmable high-precision linear motion actuators were used to generate primarily anterior-posterior (AP) and primarily superior-inferior (SI) motion in a reproducible fashion in order to enable (a) variable correlation between the displacement of interior volume and the exterior surface, (b) independent changes in the amplitude of the AP and SI motions, and (c) variable hysteresis. The ability of the phantom to produce complex and variable motion accurately and reproducibly was evaluated by programming the two actuators with mathematical and patient-recorded lung tumor motion traces, and recording the trajectories of various markers using kV fluoroscopy. As an example application, the phantom was used to evaluate the performance of lung motion models constructed from kV fluoroscopy and 4DCT images. Results: The phantom exhibited a high degree of reproducibility and marker motion ranges were reproducible to within 0.5 mm. Variable correlation was observed between the displacements of internal-internal and internal-external markers. The SI and AP components of motion of a specific marker had a correlation parameter that varied from À11 to 17. Monitoring a region of interest on the phantom's surface to estimate internal marker motion led to considerably lower uncertainties than when a single point was monitored. Conclusions: We successfully designed and implemented a programmable, externally and internally deformable lung motion phantom that allows for a reproducible change in external-internal and internal-internal correlation of embedded markers.
British Journal of Radiology, Mar 1, 2019
A, et al. Mild hyperthermia as a localized radiosensitizer for deep-seated tumors: investigation ... more A, et al. Mild hyperthermia as a localized radiosensitizer for deep-seated tumors: investigation in an orthotopic prostate cancer model in mice.
I would also like to express my gratitude to my defence committee members professors Hanli Liu, a... more I would also like to express my gratitude to my defence committee members professors Hanli Liu, and Michael Cho for their valuable feedback, guidance and time. Additionally, I am thankful to Dr. Rajiv Chopra for having provided me with the opportunity to serve in his research group. Finally, I would like to thank my dearest family and Pouya for their tremendous support over the course of my studies. Their positive reinforcement and encouragement has been my motivation for pushing forward and succeeding.
Physics in Medicine and Biology, Feb 11, 2021
Many surrogate-based motion models (SMMs), proposed to guide motion management in radiotherapy, a... more Many surrogate-based motion models (SMMs), proposed to guide motion management in radiotherapy, are constructed by correlating motion of an external surrogate and internal anatomy during CT-simulation. Changes in this correlation define model break down. We validate a methodology that incorporates fluoroscopic images (FL) acquired during treatment for SMM construction and update. Under a prospective IRB, 4DCT scans, VisionRT 25 surfaces, and orthogonal FLs were collected from five lung cancer patients. VisionRT surfaces and two FL timeseries were acquired pre-and post-treatment. A simulated annealing optimization scheme was used to estimate optimal lung deformations by maximizing the mutual information between digitally reconstructed radiographs (DRRs) of the SMM-estimated 3D images and FLs. Our SMM used partial-least-regression and was trained using the optimal deformations and VisionRT surfaces from the first breathing-cycle. SMM performance was evaluated 30 using the mutual information score between reference FLs and the corresponding SMM or phase-assigned 4DCT DRRs. The Hausdorff distance for contoured landmarks was used to evaluate target position estimation error. For four out of five patients, two principal components approximated lung surface deformations with submillimeter accuracy. Analysis of the mutual information score between more than 4,000 pairs of FL and DRR demonstrated that our model led to more similarity between the FL and DRR images compared to 4DCT and DRR images from 35 a model based on an a priori correlation model. Our SMM consistently displayed lower mean and 95 th percentile Hausdorff distances. For one patient, 95 th percentile Hausdorff distance was reduced by 11mm. Patient-averaged reductions in mean and 95 th percentile Hausdorff distances were 3.6mm and 7mm for right-lung, and 3.1mm and 4mm for left-lung targets. FL data were used to evaluate model performance and investigate the feasibility of model update. Despite variability in breathing, use of post-treatment FL preserved model fidelity and consistently 40 outperformed 4DCT for position estimation.
Advances in Radiation Oncology
مجله دانشکده پزشکی اصفهان, 2012
Background: In this study, we tried to choose the proper material to use on a magnetic resonance ... more Background: In this study, we tried to choose the proper material to use on a magnetic resonance imaging (MRI)-compatible robot. The robot is to take soft tissue samples in an image guided process. Since this robot is made of MRI-compatible material, its links are invisible in the MR images. Finding such markers would enable us to distinguish the position of links in the images and as a result in the real world. Methods: Four materials compatible with magnetic environments, including liquid paraffin, nitroglycerin, vitamin E pills, and silicon oil, were tested to find the most appropriate one to be used as the marker. In addition to compatibility with MRI environment, the material had to have suitable contrast to avoid blurry images. The tests were performed in a Philips MRI system at 1 and 1.5 Tesla. Findings: Liquid paraffin, nitroglycerin, vitamin E pills, and silicon oil scored 50, 62.35, 45.6, and 53.15, respectively. Most of the evaluated factors were satisfied by nitroglyceri...
International Journal of Radiation Oncology*Biology*Physics, 2020
We propose a novel volumetric surrogate-based motion model (SMM) to address limitations of single... more We propose a novel volumetric surrogate-based motion model (SMM) to address limitations of single cycle respiratory-correlated 4DCT in capturing breathing variations. SMMs are constructed based on the a priori correlation between an external surrogate and the internal motion observed during the planning CT acquisition. Our machine-learning based volumetric SMM exploits the internal-external correlation observed at the time of treatment delivery, minimizing the loss of accuracy resulting from commonly occurring changes in this correlation. We evaluated improvements in target position estimation from our SMM compared to 4DCT by analyzing 2,369 fluoroscopic (FL) images.
International Journal of Radiation Oncology Biology Physics, 2020
Medical Physics, 2019
Purpose: We develop and validate a motion model that uses real-time surface photogrammetry acquir... more Purpose: We develop and validate a motion model that uses real-time surface photogrammetry acquired concurrently with four-dimensional computed tomography (4DCT) to estimate respiration-induced changes within the entire irradiated volume, over arbitrarily many respiratory cycles. Methods: A research, couch-mounted, VisionRT (VRT) system was used to acquire optical surface data (15 Hz, ROI = 15 × 20 cm 2) from the thoraco-abdominal surface of a consented lung SBRT patient, concurrently with their standard-of-care 4DCT. The end-exhalation phase from the 4DCT was regarded as reference and for each remaining phase, deformation vector fields (DVFs) with respect to the reference phase were computed. To reduce dimensionality, the first two principal components (PCs) of the matrix of nine DVFs were calculated. In parallel, ten phaseaveraged VRT surfaces were created. Surface DVFs and corresponding PCs were computed. A principal least squares regression was used to relate the PCs of surface DVF to those of volume DVFs, establishing a relationship between time-varying surface and the underlying time-varying
The British Journal of Radiology, 2019
A, et al. Mild hyperthermia as a localized radiosensitizer for deep-seated tumors: investigation ... more A, et al. Mild hyperthermia as a localized radiosensitizer for deep-seated tumors: investigation in an orthotopic prostate cancer model in mice.
Physics in Medicine & Biology, 2021
Many surrogate-based motion models (SMMs), proposed to guide motion management in radiotherapy, a... more Many surrogate-based motion models (SMMs), proposed to guide motion management in radiotherapy, are constructed by correlating motion of an external surrogate and internal anatomy during CT-simulation. Changes in this correlation define model break down. We validate a methodology that incorporates fluoroscopic (FL) images acquired during treatment for SMM construction and update. Under a prospective IRB, 4DCT scans, VisionRT (VRT) surfaces, and orthogonal FLs were collected from five lung cancer patients. VRT surfaces and two FL time-series were acquired pre- and post-treatment. A simulated annealing optimization scheme was used to estimate optimal lung deformations by maximizing the mutual information (MI) between digitally reconstructed radiographs (DRRs) of the SMM-estimated 3D images and FLs. Our SMM used partial-least-regression and was trained using the optimal deformations and VRT surfaces from the first breathing-cycle. SMM performance was evaluated using the MI score betwee...
Manipulating the K-Space for Reduction of Respiratory Induced Motion Artifacts Maida Ranjbar, M.S... more Manipulating the K-Space for Reduction of Respiratory Induced Motion Artifacts Maida Ranjbar, M.Sc. The University of Texas at Arlington, 2016 Supervising Professor: Dr. Ananth Madhuranthakam Respiratory induced motion artifacts, particularly those occurring in the abdomen and lung, pose a hefty problem in current diagnostic MR imaging. Application of images plagued with such artifacts not only hinder diagnosis, but may result in the enforcement of undesirably large safety margins in radiation therapy due to un-captured tumor characteristics that are concealed by the artifact. While several methods such as gated scans, breath-hold scans, variation of the K-Space acquisition trajectory, and reducing the scan time via partial acquisition or parallel imaging have been proposed as a solution, a robust and yet simple to implement remedy still remains to be proposed. This work investigates the application of partial K-Space acquisition/completion methods to correct for motion induced arti...