Ziad Abou Saleh - Academia.edu (original) (raw)

Papers by Ziad Abou Saleh

Journal of Contemporary Brachytherapy, 2020

Purpose AccuBoost is a complex non-invasive brachytherapy procedure for breast treatment. This te... more Purpose AccuBoost is a complex non-invasive brachytherapy procedure for breast treatment. This technique requires a radiation oncologist to manually select applicator grid position and size by overlaying transparencies over a mammographic image to encompass surgical clips and resected tumor bed. An algorithm was developed in MATLAB™ to automate the selection of round applicators based on surgical clip position. Material and methods A total of 42 mammograms belonging to 10 patients were retrospectively analyzed. Images were pre-processed by masking imprinted localization grid and regions around the grid. A threshold was applied to isolate high-intensity pixels and generate a binary image. A set of morphological operations including region dilation, filling, clearing border structures, and erosion were performed to segment the different regions. A support vector machine classification model was trained to categorize segmented regions as either surgical clips or miscellaneous objects b...

Journal of applied clinical medical physics, Jan 13, 2018

The deep inspiration breath hold (DIBH) and prone (P) position are two common heart-sparing techn... more The deep inspiration breath hold (DIBH) and prone (P) position are two common heart-sparing techniques for external-beam radiation treatment of left-sided breast cancer patients. Clinicians select the position that is deemed to be better for tissue sparing based on their experience. This approach, however, is not always optimum and consistent. In response to this, we develop a quantitative tool that predicts the optimal positioning for the sake of organs at risk (OAR) sparing. Sixteen left-sided breast cancer patients were considered in the study, each received CT scans in the supine free breathing, supine DIBH, and prone positions. Treatment plans were generated for all positions. A patient was classified as DIBH or P using two different criteria: if that position yielded (1) lower heart dose, or (2) lower weighted OAR dose. Ten anatomical features were extracted from each patient's data, followed by the principal component analysis. Sequential forward feature selection was imp...

Medical Physics, 2014

Purpose:Dose accumulation following deformable image registration (DIR) is challenging. In this s... more Purpose:Dose accumulation following deformable image registration (DIR) is challenging. In this study, we used a statistical sampling approach, which takes into account both DIR uncertainties and patient‐specific organ motion, to study the distribution of possible true dose distributions.Methods:The study included ten patients (six CT scans/patient) treated with radiotherapy for prostate cancer. For each patient, the planned dose was re‐calculated on the repeated geometries, following rigid registration based on fiducial markers. The dose re‐calculated on the first CT served as our snapshot dose distribution (D1) and the average of the first five repeat scans as our treatment course reference dose distribution (Dref). Patient‐specific motion and DIR‐uncertainties, at each voxel in CT1, were assessed using a previously developed DIR performance measure, the distance discordance metric (DDM). To sample the distribution of possible true, predicted dose distributions (Dpred), we resampl...

International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, 2017

Physics and Imaging in Radiation Oncology, 2017

Physics in medicine and biology, Jan 21, 2016

Deformable image registration (DIR) is essential for adaptive radiotherapy (RT) for tumor sites s... more Deformable image registration (DIR) is essential for adaptive radiotherapy (RT) for tumor sites subject to motion, changes in tumor volume, as well as changes in patient normal anatomy due to weight loss. Several methods have been published to evaluate DIR-related uncertainties but they are not widely adopted. The aim of this study was, therefore, to evaluate intra-patient DIR for two highly deformable organs-the bladder and the rectum-in prostate cancer RT using a quantitative metric based on multiple image registration, the distance discordance metric (DDM). Voxel-by-voxel DIR uncertainties of the bladder and rectum were evaluated using DDM on weekly CT scans of 38 subjects previously treated with RT for prostate cancer (six scans/subject). The DDM was obtained from group-wise B-spline registration of each patient's collection of repeat CT scans. For each structure, registration uncertainties were derived from DDM-related metrics. In addition, five other quantitative measures,...

Radiotherapy and Oncology, 2011

Terrestrial Gamma-ray Flashes (TGFs) are intense bursts of gamma-rays first observed from space u... more Terrestrial Gamma-ray Flashes (TGFs) are intense bursts of gamma-rays first observed from space using the BATSE instrument onboard the Compton Gamma Ray Observatory. Recent measurements from the RHESSI spacecraft, along with modeling, show that these flashes most likely originate from altitudes between 15 and 21 km, making it difficult to detect such events on the ground due to atmospheric attenuation. However, in 2004, Dwyer et al. reported a gamma-ray burst at ground level during the initial stage of a rocket-triggered lightning that had a similar energy spectrum and time duration to TGFs. These results suggest that the processes that produce TGFs may also occur at lower altitudes within thunderclouds, beamed downwards instead of upwards like TGFs observed from space, making it possible to observe such events on the ground. In 2009, we launched a ground campaign to search for such TGF-like gamma-ray events during thunderstorms in coordination with ADELE (Airborne Detector for Ener...

Physics in Medicine and Biology, 2014

Medical Physics, 2012

ABSTRACT Purpose: To explore the correlation between spatial dose distribution and toxicity of no... more ABSTRACT Purpose: To explore the correlation between spatial dose distribution and toxicity of normal tissue by mapping 3D dose distribution onto a reference patient. Methods: In order to facilitate the direct correlation between dose to a certain tissue sub-volume and toxicity, 3D dose distributions of a patient cohort are deformed onto a single reference patient using deformable image registration. Spatial Spearman rank correlations between warped dose and toxicity are then computed on a point-by-point basis over the entire voxel space of the reference patient. We illustrate this approach using a cohort of 37 right-sided H&N cancers of the oropharynx regarding the endpoint of trismus. Patients were treated with definitive IMRT and concurrent chemotherapy with a prescription dose of 70 Gy between Jan. 2004 and April 2009 at MSKCC with a median follow-up time of 34 months (range, 6-68). 12 patients developed trismus (Grade >=1). Dose volume histograms (DVH) of the mastication muscles were also exported to perform logistic regression. Results: The standard logistic regression model based on DVH derived parameters for contoured muscles provided a moderate Spearman correlation (Rs=0.45, p<0.05). Meanwhile, examining the 3D Spearman map reveals a region with high correlation (Rs=0.58, p<0.001). Interestingly, a close up view shows that this potentially 'radio-sensitive' region is located on the contralateral side at the attachment point of the medial and lateral pterygoid muscles with the pterygoid plate. Conclusions: This study demonstrates the feasibility of studying the spatial correlation between dose and toxicity in normal tissues. The validity of this method was demonstrated in H&N patients. This technique preserves the spatial information of the dose distribution and provides an unbiased approach to identify critical anatomic structures since it does not require prior assumptions about the organs at risk. In addition, this method is generic and can be extended to study other complication endpoints. Partially supported by NIH grant ROI CA85181.

Journal of Geophysical Research: Atmospheres, 2010

Using an eight‐station array of electric field derivative (dE/dt) sensors and colocated NaI X‐ray... more Using an eight‐station array of electric field derivative (dE/dt) sensors and colocated NaI X‐ray detectors, we have obtained 3‐D RF source locations during the leaders and attachment processes of three first strokes initiated by stepped leaders in natural cloud‐to‐ground lightning and one stroke initiated by a dart‐stepped leader in a rocket‐and‐wire triggered flash. Stepped leader and dart‐stepped leader dE/dt pulses are tracked from a few hundred meters to a few tens of meters above ground, after which pulses of different characteristics than the step pulses are observed to occur at lower altitudes. These postleader pulses include: (1) the “leader burst,” a group of pulses in the dE/dt waveform occurring just prior to the slow front in the corresponding return‐stroke electric field waveform; (2) dE/dt pulses occurring during the slow front; and (3) the fast‐transition or dominant dE/dt pulse that is usually associated with the rapid transition to peak in the return‐stroke electri...

Journal of Geophysical Research: Atmospheres, 2009

The Thunderstorm Energetic Radiation Array (TERA) is located at the University of Florida, Florid... more The Thunderstorm Energetic Radiation Array (TERA) is located at the University of Florida, Florida Tech International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida. The array includes forty‐five 7.6‐cm‐diameter NaI/photomultiplier tube detectors enclosed in 24 separate aluminum boxes that shield the detectors from light, moisture, and RF noise. The array covers the ∼1 km2 ICLRT facility, centered on the rocket launch tower, used to trigger lightning. From 2005 to 2007, TERA recorded seven rocket‐triggered lightning flashes. In this paper we present an analysis of the X‐ray emission of three of these flashes. The X‐ray emission is observed to occur during the dart leader phase of each stroke, just prior to the time of the return stroke. Significant X‐rays are observed on all the detectors to a distance of 500 m from the lightning channel for times up to 200 μs prior to the start of the return stroke. Using Monte Carlo simulations to model the X‐ray propa...

Journal of Geophysical Research, 2008

Journal of Geophysical Research, 2011

Journal of Geophysical Research: Atmospheres, 2010

Using recent X‐ray and gamma‐ray observations of terrestrial gamma‐ray flashes (TGFs) from spacec... more Using recent X‐ray and gamma‐ray observations of terrestrial gamma‐ray flashes (TGFs) from spacecraft and of natural and rocket‐triggered lightning from the ground, along with detailed models of energetic particle transport, we calculate the fluence (integrated flux) of high‐energy (million electronvolt) electrons, X rays, and gamma rays likely to be produced inside or near thunderclouds in high electric field regions. We find that the X‐ray/gamma‐ray fluence predicted for lightning leaders propagating inside thunderclouds agrees well with the fluence calculated for TGFs, suggesting a possible link between these two phenomena. Furthermore, based on reasonable meteorological assumptions about the magnitude and extent of the electric fields, we estimate that the fluence of high‐energy runaway electrons can reach biologically significant levels at aircraft altitudes. If an aircraft happened to be in or near the high‐field region when either a lightning discharge or a TGF event is occur...

International Journal of Radiation Oncology*Biology*Physics, 2012

International Journal of Radiation Oncology*Biology*Physics, 2011

Journal of Contemporary Brachytherapy, 2020

Purpose AccuBoost is a complex non-invasive brachytherapy procedure for breast treatment. This te... more Purpose AccuBoost is a complex non-invasive brachytherapy procedure for breast treatment. This technique requires a radiation oncologist to manually select applicator grid position and size by overlaying transparencies over a mammographic image to encompass surgical clips and resected tumor bed. An algorithm was developed in MATLAB™ to automate the selection of round applicators based on surgical clip position. Material and methods A total of 42 mammograms belonging to 10 patients were retrospectively analyzed. Images were pre-processed by masking imprinted localization grid and regions around the grid. A threshold was applied to isolate high-intensity pixels and generate a binary image. A set of morphological operations including region dilation, filling, clearing border structures, and erosion were performed to segment the different regions. A support vector machine classification model was trained to categorize segmented regions as either surgical clips or miscellaneous objects b...

Journal of applied clinical medical physics, Jan 13, 2018

The deep inspiration breath hold (DIBH) and prone (P) position are two common heart-sparing techn... more The deep inspiration breath hold (DIBH) and prone (P) position are two common heart-sparing techniques for external-beam radiation treatment of left-sided breast cancer patients. Clinicians select the position that is deemed to be better for tissue sparing based on their experience. This approach, however, is not always optimum and consistent. In response to this, we develop a quantitative tool that predicts the optimal positioning for the sake of organs at risk (OAR) sparing. Sixteen left-sided breast cancer patients were considered in the study, each received CT scans in the supine free breathing, supine DIBH, and prone positions. Treatment plans were generated for all positions. A patient was classified as DIBH or P using two different criteria: if that position yielded (1) lower heart dose, or (2) lower weighted OAR dose. Ten anatomical features were extracted from each patient's data, followed by the principal component analysis. Sequential forward feature selection was imp...

Medical Physics, 2014

Purpose:Dose accumulation following deformable image registration (DIR) is challenging. In this s... more Purpose:Dose accumulation following deformable image registration (DIR) is challenging. In this study, we used a statistical sampling approach, which takes into account both DIR uncertainties and patient‐specific organ motion, to study the distribution of possible true dose distributions.Methods:The study included ten patients (six CT scans/patient) treated with radiotherapy for prostate cancer. For each patient, the planned dose was re‐calculated on the repeated geometries, following rigid registration based on fiducial markers. The dose re‐calculated on the first CT served as our snapshot dose distribution (D1) and the average of the first five repeat scans as our treatment course reference dose distribution (Dref). Patient‐specific motion and DIR‐uncertainties, at each voxel in CT1, were assessed using a previously developed DIR performance measure, the distance discordance metric (DDM). To sample the distribution of possible true, predicted dose distributions (Dpred), we resampl...

International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, 2017

Physics and Imaging in Radiation Oncology, 2017

Physics in medicine and biology, Jan 21, 2016

Deformable image registration (DIR) is essential for adaptive radiotherapy (RT) for tumor sites s... more Deformable image registration (DIR) is essential for adaptive radiotherapy (RT) for tumor sites subject to motion, changes in tumor volume, as well as changes in patient normal anatomy due to weight loss. Several methods have been published to evaluate DIR-related uncertainties but they are not widely adopted. The aim of this study was, therefore, to evaluate intra-patient DIR for two highly deformable organs-the bladder and the rectum-in prostate cancer RT using a quantitative metric based on multiple image registration, the distance discordance metric (DDM). Voxel-by-voxel DIR uncertainties of the bladder and rectum were evaluated using DDM on weekly CT scans of 38 subjects previously treated with RT for prostate cancer (six scans/subject). The DDM was obtained from group-wise B-spline registration of each patient's collection of repeat CT scans. For each structure, registration uncertainties were derived from DDM-related metrics. In addition, five other quantitative measures,...

Radiotherapy and Oncology, 2011

Terrestrial Gamma-ray Flashes (TGFs) are intense bursts of gamma-rays first observed from space u... more Terrestrial Gamma-ray Flashes (TGFs) are intense bursts of gamma-rays first observed from space using the BATSE instrument onboard the Compton Gamma Ray Observatory. Recent measurements from the RHESSI spacecraft, along with modeling, show that these flashes most likely originate from altitudes between 15 and 21 km, making it difficult to detect such events on the ground due to atmospheric attenuation. However, in 2004, Dwyer et al. reported a gamma-ray burst at ground level during the initial stage of a rocket-triggered lightning that had a similar energy spectrum and time duration to TGFs. These results suggest that the processes that produce TGFs may also occur at lower altitudes within thunderclouds, beamed downwards instead of upwards like TGFs observed from space, making it possible to observe such events on the ground. In 2009, we launched a ground campaign to search for such TGF-like gamma-ray events during thunderstorms in coordination with ADELE (Airborne Detector for Ener...

Physics in Medicine and Biology, 2014

Medical Physics, 2012

ABSTRACT Purpose: To explore the correlation between spatial dose distribution and toxicity of no... more ABSTRACT Purpose: To explore the correlation between spatial dose distribution and toxicity of normal tissue by mapping 3D dose distribution onto a reference patient. Methods: In order to facilitate the direct correlation between dose to a certain tissue sub-volume and toxicity, 3D dose distributions of a patient cohort are deformed onto a single reference patient using deformable image registration. Spatial Spearman rank correlations between warped dose and toxicity are then computed on a point-by-point basis over the entire voxel space of the reference patient. We illustrate this approach using a cohort of 37 right-sided H&N cancers of the oropharynx regarding the endpoint of trismus. Patients were treated with definitive IMRT and concurrent chemotherapy with a prescription dose of 70 Gy between Jan. 2004 and April 2009 at MSKCC with a median follow-up time of 34 months (range, 6-68). 12 patients developed trismus (Grade >=1). Dose volume histograms (DVH) of the mastication muscles were also exported to perform logistic regression. Results: The standard logistic regression model based on DVH derived parameters for contoured muscles provided a moderate Spearman correlation (Rs=0.45, p<0.05). Meanwhile, examining the 3D Spearman map reveals a region with high correlation (Rs=0.58, p<0.001). Interestingly, a close up view shows that this potentially 'radio-sensitive' region is located on the contralateral side at the attachment point of the medial and lateral pterygoid muscles with the pterygoid plate. Conclusions: This study demonstrates the feasibility of studying the spatial correlation between dose and toxicity in normal tissues. The validity of this method was demonstrated in H&N patients. This technique preserves the spatial information of the dose distribution and provides an unbiased approach to identify critical anatomic structures since it does not require prior assumptions about the organs at risk. In addition, this method is generic and can be extended to study other complication endpoints. Partially supported by NIH grant ROI CA85181.

Journal of Geophysical Research: Atmospheres, 2010

Using an eight‐station array of electric field derivative (dE/dt) sensors and colocated NaI X‐ray... more Using an eight‐station array of electric field derivative (dE/dt) sensors and colocated NaI X‐ray detectors, we have obtained 3‐D RF source locations during the leaders and attachment processes of three first strokes initiated by stepped leaders in natural cloud‐to‐ground lightning and one stroke initiated by a dart‐stepped leader in a rocket‐and‐wire triggered flash. Stepped leader and dart‐stepped leader dE/dt pulses are tracked from a few hundred meters to a few tens of meters above ground, after which pulses of different characteristics than the step pulses are observed to occur at lower altitudes. These postleader pulses include: (1) the “leader burst,” a group of pulses in the dE/dt waveform occurring just prior to the slow front in the corresponding return‐stroke electric field waveform; (2) dE/dt pulses occurring during the slow front; and (3) the fast‐transition or dominant dE/dt pulse that is usually associated with the rapid transition to peak in the return‐stroke electri...

Journal of Geophysical Research: Atmospheres, 2009

The Thunderstorm Energetic Radiation Array (TERA) is located at the University of Florida, Florid... more The Thunderstorm Energetic Radiation Array (TERA) is located at the University of Florida, Florida Tech International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida. The array includes forty‐five 7.6‐cm‐diameter NaI/photomultiplier tube detectors enclosed in 24 separate aluminum boxes that shield the detectors from light, moisture, and RF noise. The array covers the ∼1 km2 ICLRT facility, centered on the rocket launch tower, used to trigger lightning. From 2005 to 2007, TERA recorded seven rocket‐triggered lightning flashes. In this paper we present an analysis of the X‐ray emission of three of these flashes. The X‐ray emission is observed to occur during the dart leader phase of each stroke, just prior to the time of the return stroke. Significant X‐rays are observed on all the detectors to a distance of 500 m from the lightning channel for times up to 200 μs prior to the start of the return stroke. Using Monte Carlo simulations to model the X‐ray propa...

Journal of Geophysical Research, 2008

Journal of Geophysical Research, 2011

Journal of Geophysical Research: Atmospheres, 2010

Using recent X‐ray and gamma‐ray observations of terrestrial gamma‐ray flashes (TGFs) from spacec... more Using recent X‐ray and gamma‐ray observations of terrestrial gamma‐ray flashes (TGFs) from spacecraft and of natural and rocket‐triggered lightning from the ground, along with detailed models of energetic particle transport, we calculate the fluence (integrated flux) of high‐energy (million electronvolt) electrons, X rays, and gamma rays likely to be produced inside or near thunderclouds in high electric field regions. We find that the X‐ray/gamma‐ray fluence predicted for lightning leaders propagating inside thunderclouds agrees well with the fluence calculated for TGFs, suggesting a possible link between these two phenomena. Furthermore, based on reasonable meteorological assumptions about the magnitude and extent of the electric fields, we estimate that the fluence of high‐energy runaway electrons can reach biologically significant levels at aircraft altitudes. If an aircraft happened to be in or near the high‐field region when either a lightning discharge or a TGF event is occur...

International Journal of Radiation Oncology*Biology*Physics, 2012

International Journal of Radiation Oncology*Biology*Physics, 2011