Omar A Zeidan

Omar A Zeidan
Orlando Health · Radiation Physics

PhD

About

143
Publications
10,057
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1,752
Citations
Citations since 2017
15 Research Items
470 Citations
2017201820192020202120222023020406080
2017201820192020202120222023020406080
2017201820192020202120222023020406080
2017201820192020202120222023020406080

Publications

Publications (143)
Article
Purpose/Objective(s) There is an increasing concern about rising carbon dioxide (CO2) levels and its hazardous impact on human health and climate change. Radiation oncology uses high energy machines; however, their carbon footprint is not well understood. This study estimates the energy utilization of photon therapy, and estimates corresponding car...
Article
Purpose/Objective(s) There is an increasing concern about rising carbon dioxide (CO2) levels and its hazardous impact on human health and climate change. Patients travel sometimes significant distances for their daily radiation treatments, especially for rare modalities such as proton therapy; the carbon footprint of this commute is not well unders...
Article
Purpose/Objective(s) There is an increasing concern about rising carbon dioxide (CO2) levels and its hazardous impact on human health and climate change. Radiation oncology uses high energy machines; however, their carbon footprint is not well understood. This study quantifies the energy utilization of proton therapy, and estimates corresponding ca...
Article
Purpose We present an analysis of various operational metrics for a novel compact proton therapy system, including clinical case mix, subsystems utilization, and quality assurance trends in beam delivery parameters over a period of 5 years. Materials and Methods Patient-specific data from a total of 850 patients (25,567 fractions) have been collec...
Article
Purpose/Objective(s) Single-fraction palliative spine radiation is an attractive option for patients with poor prognosis because of its convenience and effectiveness in terms of pain relief. However, the associated large doses to normal tissues can lead to toxicities that negatively impact quality of life. Proton therapy offers a dosimetric solutio...
Article
Though potentially beneficial, proton beam stereotactic radiosurgery has not been adopted widely secondary to the technical challenge of safely delivering multiple focused beams of proton radiation. In this study, we describe the design and characterization of a proton beam stereotactic radiosurgery system that can be adopted by existing passive sc...
Article
Purpose To present quantitative dosimetric evaluations of five proton pencil beam spot placement techniques. Materials and Methods The spot placement techniques that were investigated include two grid-based (rectilinear grid and hexagonal grid, both commonly available in commercial planning systems) and three boundary-contoured (concentric contour...
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Purpose: Real-time magnetic resonance guided radiation therapy (MRgRT) uses 2D cine imaging for target tracking. This work evaluates the percent image uniformity (PIU) and spatial integrity of cine images in the presence of multileaf collimator (MLC) and gantry motion in order to simulate sliding window and volumetric modulated arc therapy (VMAT)...
Article
PURPOSE An episode-based payment model, the Radiation Oncology Alternative Payment Model (RO-APM), has been proposed for Medicare reimbursement of radiation services provided to oncology patients. RO-APM may have significant impact on reimbursement for specific patient populations. METHODS This investigation compares historical fee-for-service tec...
Article
Maintaining a sharp lateral dose falloff in pencil beam scanning (PBS) proton therapy is crucial for sparing organs at risk (OARs), especially when they are in close proximity to the target volume. The most common approach to improve lateral dose falloff is through the use of physical beam shaping devices, such as brass apertures or collimator base...
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Purpose: The purpose of this study was to investigate daily repositioning accuracy by analyzing inter- and intra-fractional uncertainties associated with patients treated for intracranial or base of skull tumors in a compact proton therapy system with 6 degrees of freedom (DOF) robotic couch and a thermoplastic head mask indexed to a base of skull...
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Purpose: To describe the commissioning of AIRO mobile CT system (AIRO) for adaptive proton therapy on a compact double scattering proton therapy system. Methods: A Gammex phantom was scanned with varying plug patterns, table heights, and mAs on a CT simulator (CT Sim) and on the AIRO. AIRO-specific CT-stopping power ratio (SPR) curves were creat...
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Purpose: The purpose of this study was to characterize the Mobius AIRO Mobile CT System for localization and image-guided proton therapy. This is the first known application of the AIRO for proton therapy. Methods: Five CT images of a Catphan(®) 504 phantom were acquired on the AIRO Mobile CT System, Varian EDGE radiosurgery system cone beam CT...
Article
Accurate assessment of range uncertainty is critical in proton therapy. However, there is a lack of data and consensus on how to evaluate the appropriate amount of uncertainty. The purpose of this study is to quantify the range uncertainty in various treatment conditions in proton therapy, using transmission measurements through various animal tiss...
Article
We present a quantitative methodology to measure head interfraction movements within intracranial masks of commercial immobilization devices used for proton radiotherapy. A three-points tracking (3PtTrack) method was developed to measure the mask location for each treatment field over an average of 10 fractions for seven patients. Five patients wer...
Article
Radiation therapy has been a major modality employed in the treatment of head and neck (H&N) cancer for decades. In that time, radiation technology has evolved considerably. Thirty years ago radiation therapy for H&N cancer consisted of two-dimensional techniques using plain field radiographs, bony anatomy, and hand drawn blocks [1]. Beam set ups w...
Article
Purpose: An optical tracking and positioning system (OTPS) was developed to validate the software-driven isocentric (SDI) approach to control the six-degrees-of-freedom movement of a robotic couch. Methods: The SDI approach to movements rotating around a predefined isocenter, referred to as a GeoIso, instead of a mechanical pivot point was devel...
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The main purposes of this study were to 1) investigate the dosimetric quality of uniform scanning proton therapy planning (USPT) for prostate cancer patients with a metal hip prosthesis, and 2) compare the dosimetric results of USPT with that of volumetric-modulated arc therapy (VMAT). Proton plans for prostate cancer (four cases) were generated in...
Article
Purpose: We present a quantitative methodology utilizing an optical tracking system for monitoring head inter-fraction movements within brain masks to assess the effectiveness of two intracranial immobilization techniques. Methods and Materials: A 3-point-tracking method was developed to measure the mask location for a treatment field at each fract...
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Radiation therapy is an effective cancer treatment solution, involving complex machinery and careful planning. Physicians find difficulty in visualizing the relative three-dimensional positions of linac (linear accelerator) components. We propose a graphical simulator for linacs that will improve the planning process, saving time and resources in g...
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External beam radiation therapy (EBRT) is an effective and widely accepted form of treatment for many types of cancer that requires extensive planning. Unfortunately, current treatment planning systems have limited or no available visual aid that combines patient volumetric models extracted from patient specific CT data with the treatment device in...
Article
Purpose: The main purposes of this study were to (1) investigate the dependency of lateral penumbra (80%-20% distance) of uniform scanning proton beams on various factors such as air gap, proton range, modulation width, compensator thickness, and depth, and (2) compare the lateral penumbra calculated by a treatment planning system (TPS) with measu...
Article
Purpose: The purpose of this study is to investigate the accuracy of XiO treatment planning system (TPS) in predicting lateral penumbra (80%-20% distance) for different air gap (AG) and compensator thickness (COMP) in uniform scanning proton therapy. Methods: First, the dependency of lateral penumbra on AG was investigated for AG 0, 5, 10, 15, 2...
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Purpose: To present a practical image-guided method to position an endorectal balloon that improvesin vivo thermoluminiscent dosimeter (TLD) measurements of rectal doses in proton therapy for prostate cancer.
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We describe the design and use of a daily quality assurance (QA) system for proton therapy. The QA system is designed to check the overall readiness of proton therapy system consistently within certain reference tolerances by a home-made QA device (the QA device). The QA device is comprised of a commercially available QA device, rf-Daily QA 3, a ho...
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Background: Nuclei in the A≈190 mass region show gradual shape changes from prolate through nonaxial deformed shapes and ultimately towards spherical shapes as the Pb region is approached. Exploring how this shape evolution occurs will help us understand the evolution of collectivity in this region.Purpose: The level scheme of the 192Au nucleus in...
Article
Neutron exposure is of concern in proton therapy, and varies with beam delivery technique, nozzle design, and treatment conditions. Uniform scanning is an emerging treatment technique in proton therapy, but neutron exposure for this technique has not been fully studied. The purpose of this study is to investigate the neutron dose equivalent per the...
Article
Topic of interest: Clinical applications of AlignRT 3-cameras real-time surface image-guided positioning system (IGPS) for positioning patients to reduce the number of X-ray images and tracking intra-fractional movements in proton therapy.Purposes: To position patients and track the intra-fractional movements, the AlignRT system was implemented in...
Article
Purpose: to present and validate a method for modeling three-dimensional positron emission (PE) activity distributions induced by proton beam irradiation for PET/CT delivery verification studies in homogeneous media. Methods: the method relies on modeling the 3D proton flux distribution by combining the analytical expression for the depth reduction...
Article
Purpose: Currently, no commercial proton treatment planning systems have been FDA-approved for Monitor Unit (MU) prediction. Patient and field specific MU numbers and output factors are therefore determined by either measurements or in-house modeling. The purpose of this project is to assess the modeling accuracy and determine in which cases measur...
Article
Purpose: Quality assurance (QA) is essential in safe and accurate delivery of radiation therapy. However, QA in proton therapy is challenging due to complicated and often facility-specific beam delivery systems and limited beam time for QA. The purpose of this study is to develop an efficient and comprehensive QA procedure for a multi-room proton t...
Article
Purpose: We describe the design and use of a daily QA device for proton therapy. The device is designed for therapists to check the readiness of the IBA Proton Therapy System (IBA, Louvain-la-Neuve, Belgium) during morning QA. The checks include connectivity, positioning, mechanical, imaging and dosimetric parameters of the proton therapy system. M...
Article
Purposes: A chair, coupled to a robotic patient positioning system (PPS) was manufactured to treat an intracranial tumor in a proton incline beam-line system. Treating patients in the seated position as accurately and efficiently as a treatment table requires the essential functions of isocentric rotation and a weight-sagging-correction algorithm f...
Article
An overview of current status of clinical protondosimetry is presented. Absolute dosimetry in proton beams using IAEA TRS 398 and ICRU 59 dosimetry protocols is presented. An overview of the use of various detectors for proton therapy beam characterization is presented including Ion Chambers for point measurements, Multi‐Layer Ionization Chambers (...
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Linear energy transfer (LET) of clinical proton beams is an important parameter influencing the biological effects of radiation. This work demonstrates LET-induced response enhance_ment in novel formulations of polymer gel dosimeters, potentially useful for LET mapping of clinical proton beams. A series of four polymer gel dosimeters (labeled A thr...
Article
Organ motion in proton therapy affects treatment dose distribution during both double-scattering (DS) and uniform-scanning (US) deliveries. We investigated the dosimetric impact of target motion using three-dimensional polymer gel dosimeters and a programmable motion platform. A simple one-beam treatment plan with 16 cm range and 6 cm modulation wa...
Article
A spatial resolution investigation of the OCTOPUSTM-IQ scanner in combination with the new BANG3-Pro2(r) polymer gel was performed by scanning a high-contrast needle phantom. The phantom contained five thin needles (0.3_mm diameter) embedded in gel positioned in different patterns: needles were inserted (a) at 45° angle from the center of the gel c...
Article
This work demonstrates a novel application of BANG3-Pro2 polymer gel dosimeter as a dosimetric phantom able to accurately capture both dose and induced activity. BANG3-Pro2 dosimeters were irradiated with a clinical proton beam using an unmodulated beam and a spread-out Bragg peak (SOBP) modulation, the latter with a Lucite compensator to introduce...
Article
Purpose: To experimentally investigate target motion impact on protondosimetry and the spatiotemporal interplay in double scattering (DS) and uniform scanning (US) deliveries using 3D polymergel dosimeters and a programmable motion platform. Methods: A one beam proton plan with 16cm range and 6cm modulation (total 13 energy layers) in both DS and U...
Article
Purpose: The Inclined Beam Line (IBL) is an innovative partial gantry design which provides two beam angles at 30 and 90 degrees with full flexibility of the patient positioning system of the gantry design. Compared to the full gantry design in proton therapy, the IBL is a simplified design allowing for less equipment maintenance, physics quality a...
Article
Purpose: Accurate determination of proton dose and penetration range is critical in proton therapy. The purpose of this study is to investigate the range and dosimetric calculation accuracy for a commercial proton therapytreatment planning system (TPS). Methods: A lamb leg and solid water plates were used as phantoms in this study. Radiochromic fil...
Article
Purpose: Neutron exposure is of concern in proton therapy, and varies with beam delivery technique and treatment conditions. The purpose of this study is to investigate the neutron dose equivalent per therapeutic dose, H/D, under various treatment conditions for uniform scanning beams employed at our proton therapy center. Methods: Using a wide ene...
Article
Purpose: preliminary investigation of the new unique formulation of BANG3‐Pro polymer gels for detecting and mapping local variations of LET in proton beam deliveries. Methods: Four polymergeldosimeters — labeled A through D and employing four different systems of free‐radical chain‐termination and chain‐transfer—were irradiated by a 230 MeV proton...
Article
Purpose: to investigate the potential of polymergeldosimeters for concurrent measurements of three‐dimensional positron emission activity and dose distributions; to evaluate the ability of this technique to identify dosimetric errors due to delivery uncertainties, including those due to range modification and target motion.Methods: three BANG3‐Pro2...
Article
Current commercial treatment planning systems are not able to accurately predict output factors and calculate monitor units for proton fields. Patient-specific field output factors are thus determined by either measurements or empirical modeling based on commissioning data. The objective of this study is to commission output factors for uniform sca...
Article
A feasibility study of proton beam PET/CT off-line quantitative dosimetry using polymer gels is presented. A newly developed proton-sensitive polymer gel dosimeter (BANG(®)3-Pro2) is used as a dosimeter and a tissue-equivalent phantom medium for this study. We explore a new approach to correlating measured proton 3-dimensional (3D) dose distributio...
Article
The structure and decay properties of high-K isomers in 176Hf have been studied using beam sweeping techniques and the Gammasphere multidetector array. A new ΔK=8 decay branch, from a Kπ=22-, six-quasiparticle, isomeric (t1/2=43μs) state at 4864 keV to the 20- state of a Kπ=14- band, has been identified. The reduced hindrance factor per degree of K...
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We report on our initial experience with daily image guidance for the treatment of a patient with a basal cell carcinoma of the nasal dorsum using bolus electron conformal therapy. We describe our approach to daily alignment using treatment machine‐integrated megavoltage (MV) planar imaging in conjunction with cone beam CT (CBCT) volumetric imaging...
Article
The aim of this study is to evaluate the dosimetric performance of a newly developed proton-sensitive polymer gel formulation for proton therapy dosimetry. Using passive scattered modulated and nonmodulated proton beams, the dose response of the gel was assessed. A next-generation optical CT scanner is used as the readout mechanism of the radiation...
Article
Purpose: An assessment of protonbeam in‐vivo dosimetry using PETimaging of dose distributions in polymergel phantoms is presented. The next‐generation 3D polymergeldosimeter (BANG®‐3‐PRO‐2) developed specifically for protonradiotherapydosimetry has the capability of accurately reproducing dose in water from ion chamber scan data. Previous studies h...
Article
To compare the geometric alignments of soft-tissue implanted markers to the traditional bony-based alignments in head-and-neck cancers, on the basis of daily image guidance. Dosimetric impact of the two alignment techniques on target coverage is presented. A total of 330 retrospective alignments (5 patients) were performed on daily megavoltage comp...
Article
Purpose: A dosimetric validation of the next‐generation 3D polymergeldosimeter (BANG®‐3‐PRO‐2) developed for protonradiotherapydosimetry is presented. Dose response curve is determined using both proton and electron beams. Lateral and depth profiles are compared to ion chamber measurements. 2D dose distributions are evaluated against those generate...
Article
Initial results of megavoltage computed tomography (MVCT) brachytherapy treatment planning are presented, using a commercially available helical tomotherapy treatment unit and standard low dose rate (LDR) brachytherapy applicators used for treatment of cervical carcinoma. The accuracy of MVCT imaging techniques, and dosimetric accuracy of the CT ba...
Chapter
The most successful integration of megavoltage computed tomography (MVCT) imaging with radiation therapy devices is the TomoTherapy™ Hi-ART. It is currently the only type of patient treatment in which MVCT imaging is integrated as part of the treatment device itself. The Hi-ART II system can generate CT images from the same megavoltage X-ray beam i...
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Full-text available
We report a corrected level scheme of 193 Au. A 215.3 keV transition, which was placed in Band 1a to decay out of the 15/2 − level, was removed, and the level energies in the band were corrected as 1106.8 keV (11/2 −) and 1522.3 keV (15/2 −). An energy of 2100.8 keV was tentatively suggested for the (19/2 −) level, as indicated in Fig. 1. The corre...
Article
The performance of a next-generation optical computed tomography scanner (OCTOPUS-5X) is characterized in the context of three-dimensional gel dosimetry. Large-volume (2.2 L), muscle-equivalent, radiation-sensitive polymer gel dosimeters (BANG-3) were used. Improvements in scanner design leading to shorter acquisition times are discussed. The spati...
Article
Full-text available
Radiation therapy is an effective and widely accepted form of treatment for many types of cancer that requires extensive computerized planning. Unfortunately, current treatment planning systems have limited or no visual aid that combines patient volumetric models extracted from patient-specific CT data with the treatment device geometry in a 3D int...
Article
Purpose: Preliminary evaluation of a novel, large‐volume (2.2 liter), 3D polymer gel dosimeter (BANG®‐3‐PRO) developed for proton radiotherapy dosimetry is presented. The characteristics of dose response and its linear energy transfer (LET) dependence are addressed. The performance of the dosimeter is analyzed under the conditions of pristine and c...
Article
Purpose: Performance of an improved 3D dosimetry system consisting of polymergel dosimeters and a next‐generation optical CT scanner (OCT) is characterized. Following improvements are discussed: increased acquisition speed of the scanner; increased useful dosimeter volume achieved by reducing image reconstruction artifacts through background subtra...
Article
To compare different image-guidance strategies in the alignment of prostate cancer patients. Using data from patients treated using daily image guidance, the remaining setup errors for several different strategies were retrospectively calculated. The alignment data from 74 patients treated with helical tomotherapy were analyzed, resulting in a data...
Article
Prostate motion during external-beam radiotherapy can affect outcomes in patients with localized prostate cancer. Prostate motion and deformation are currently being characterized with different techniques. There is significant individual variation among patients with respect to the observed motion and its dosimetric consequences. There is also sig...
Article
Purpose: To compare different image‐guidance (IG) strategies in the alignment of prostate cancer patients. Using data from patients that were treated with daily IG, the remaining set‐up errors for several different strategies were retrospectively calculated. Method and Materials: Alignment data from 74 patients treated with helical tomotherapy were...
Article
Purpose: To evaluate tumor localization in H&N patients with implanted markers based on co‐registered MVCT and KVCT images using bony anatomy and marker‐based alignments Method and Materials: Daily MVCT images from a tomotherapy unit were acquired for a total of 35 fractions for a patient with two implanted gold markers in the base of tongue. The M...
Article
The aim of this study was to assess the residual setup error of different image-guidance (IG) protocols in the alignment of patients with head and neck cancer. The protocols differ in the percentage of treatment fractions that are associated with image guidance. Using data from patients who were treated with daily IG, the residual setup errors for...
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Full-text available
External beam radiation therapy is concerned with the precise and accurate delivery of radiation for cancer treatment. Highly-collimated beams are generated in a linear accelerator, consisting of several hardware components that move around the patient in a complex geometry to allow radiation target the tumor from every possible angle. The complex...
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Full-text available
High-spin states in the doubly-odd Z = 77 nucleus 188 Ir were populated in the 186 W 7 Li,5n reaction at 52 MeV. Two nearly degenerate I = 1 sequences with the same parity were established. Both bands have been assigned the h 9/2 i 13/2 configuration, based on the systematic behavior of these excitations in the Ir nuclei and on the measured values...