Imad Ali

• University of Oklahoma Health Sciences Center

Purpose A 4D-dosimeter and quality assurance phantom prototype was developed to quantify the effects of respiratory motion. Methods The dose distributions were measured using two-dimensional detectors that were mounted on a mobile platform capable of sinusoidal motion in one direction with different patterns using adjustable motion amplitude and f...

Purpose The goal of this study is to investigate treatment planning of total marrow irradiation (TMI) using intensity-modulated spot-scanning proton therapy (IMPT). The dosimetric parameters of the intensity-modulated proton plans were evaluated and compared with the corresponding TMI plans generated with volumetric modulated arc therapy (VMAT) usi...

Introduction Although many studies have investigated small electron fields, there are several dosimetric issues that are not well understood. This includes lack of charged particle equilibrium, lateral scatter, source occlusion and volume averaging of the detectors used in the measurement of the commissioning data. High energy electron beams are al...

In the electron beam radiation therapy, customized blocks are mostly used to shape treatment fields to generate conformal doses. The goal of this study is to investigate quantitatively dosimetric uncertainties associated with heterogeneities, detectors used in the measurement of the beam data commissioning, and modeling of the interactions of high...

Aim The purpose of this study is to investigate the feasibility of proton arc therapy (PAT) using the double-scattering MEVION-S250 proton system. The treatment planning and dose delivery parameters from PAT were compared with conventional treatment planning techniques. Materials and methods PAT was simulated with multiple conformal and fixed-aper...

Aim The purpose of this study is to investigate quantitatively the correlation of displacement vector fields (DVFs) from different deformable image registration (DIR) algorithms to register images from helical computed tomography (HCT), axial computed tomography (ACT) and cone beam computed tomography (CBCT) with motion parameters. Materials and m...

Growing cities always have parking challenges and they are in need for creative ideas to solve this issue and avoid the time wasted in searching for empty parking spots. To overcome the problem, this paper proposes a simple solution using a low-cost cloud-based system design. The design will be initially implemented on campus in one parking lot at...

Growing cities always have parking challenges and they are in need for creative ideas to solve this issue and avoid the time wasted in searching for empty parking spots. To overcome the problem, this paper proposes a simple solution using a low-cost cloud-based system design. The design will be initially implemented on campus in one parking lot at...

The goal of this project is to investigate quantitatively the performance of different deformable image registration algorithms (DIR) with helical (HCT), axial (ACT), and cone-beam CT (CBCT). The variations in the CT-number values and lengths of well-known targets moving with controlled motion were evaluated. Four DIR algorithms: Demons, Fast-Demon...

The objective of this study is to quantitatively evaluate variations of dose distributions deposited in mobile target by measurement and modeling. The effects of variation in dose distribution induced by motion on tumor dose coverage and sparing of normal tissues were investigated quantitatively. The dose distributions with motion artifacts were mo...

Purpose:To compare the impact of MLC width on the dose conformity, doses received by the normal brain tissue, and other critical structures for single isocenter (SI) and multiple isocenter (MI) stereotactic IMRT (SRT) treatments for patients with at least four brain tumors. Methods:Six patients (three with seven and three with four lesions) planned...

Purpose:To investigate quantitatively positioning and dosimetric uncertainties due to 4D-CT intra-phase motion in the internal-target-volume (ITV) associated with radiation therapy using respiratory-gating for patients setup with image-guidance-radiation-therapy (IGRT) using free-breathing or average-phase CT-images. Methods:A lung phantom with an...

Purpose:To model patient motion and produce four-dimensional (4D) optimized dose distributions that consider motion-artifacts in the dose calculation during the treatment planning process. Methods:An algorithm for dose calculation is developed where patient motion is considered in dose calculation at the stage of the treatment planning. First, opti...

Purpose:To investigate quantitatively the displacement-vector-fields (DVF) obtained from different deformable image registration algorithms (DIR) in helical (HCT), axial (ACT) and cone-beam CT (CBCT) to register CT images of a mobile phantom and its correlation with motion amplitudes and frequencies. Methods:HCT, ACT and CBCT are used to image a mo...

Purpose:To quantitatively investigate the surface dose deposited in patients imaged with a kV on-board-imager mounted on a radiotherapy machine using different clinical imaging techniques and filters. Methods:A high sensitivity photon diode is used to measure the surface dose on central-axis and at an off-axis-point which is mounted on the top of a...

Purpose:To investigate quantitatively the performance of different deformable-image-registration algorithms (DIR) with helical (HCT), axial (ACT) and cone-beam CT (CBCT) by evaluating the variations in the CT-numbers and lengths of targets moving with controlled motion-patterns. Methods:Four DIR-algorithms including demons, fast-demons, Horn-Schunk...

Purpose: A motion algorithm has been developed to extract length, CT number level and motion amplitude of a mobile target from cone-beam CT (CBCT) images. Materials and methods: The algorithm uses three measurable parameters: Apparent length and blurred CT number distribution of a mobile target obtained from CBCT images to determine length, CT-n...

The purpose of this study is to evaluate patient setup accuracy and quantify indi-vidual and cumulative positioning uncertainties associated with different hardware and software components of the stereotactic radiotherapy (SRS/SRT) with the frameless 6D ExacTrac system. A statistical model is used to evaluate positioning uncertainties of the differ...

Purpose: To quantify the variations in the length and position of fiducial markers induced by motion in axial (ACT), helical (HCT) and cone-beam CT (CBCT) imaging and associated uncertainty in image-guided radiotherapy (IGRT) by measurement and modeling. Methods: A mobile thorax phantom containing markers of various lengths was imaged using ACT,...

Dosimetric consequences of positional shifts were studied using frameless Brainlab ExacTrac X‐ray system for hypofractionated (3 or 5 fractions) intracranial stereotactic radiotherapy (SRT). SRT treatments of 17 patients with metastatic intracranial tumors using the stereotactic system were retrospectively investigated. The treatments were simulate...

The aim of this study was to investigate quantitatively the dosimetric factors that increase the risk of clinical complications of rib fractures or chest wall pain after stereotactic body radiation therapy (SBRT) to the lung. The correlations of clinical complications with standard-uptake values (SUV) and FDG-PET activity distributions from post-tr...

To evaluate quantitatively the performance of different deformable image registration algorithms using a mobile thorax phantom with well-defined targets and controlled motion-patterns imaged with helical, axial and cone-beam CT. A thorax phantom was scanned using helical, axial and cone-beam CT imaging while it is moving and stationary. The phantom...

To evaluate patient setup accuracy and quantify individual and cumulative positioning uncertainties associated with different hardware and software components of the stereotactic radiotherapy (SRS/SRT) with the frameless-6D-ExacTrac system. A statistical model was used to evaluate positioning uncertainties of the different components of SRS/SRT tre...

To determine the dosimetric impact of jaw tracking and beam energies on dose conformity and normal-brain-tissue doses for intracranial tumors using VMAT (RapidArc). Seven patients with 1-2 and three patients with 4-6 intracranial tumors were planned using RapidArc for Varian TrueBeam STx machine with beam energies 6MV-FFF (Flattening-Filter-Free),...

To develop 4D-cone-beam CT (CBCT) algorithm by motion modeling that extracts actual length, CT numbers level and motion amplitude of a mobile target retrospective to image reconstruction by motion modeling. The algorithm used three measurable parameters: apparent length and blurred CT number distribution of a mobile target obtained from CBCT images...

To evaluate quantitatively dose distributions from helical, axial and cone-beam CT clinical imaging techniques by measurement using a two-dimensional (2D) diode-array detector. 2D-dose distributions from selected clinical protocols used for axial, helical and cone-beam CT imaging were measured using a diode-array detector (MapCheck2). The MapCheck2...

To investigate correlation of displacement vector fields (DVF) calculated by deformable image registration algorithms with motion parameters in helical axial and cone-beam CT images with motion artifacts. A mobile thorax phantom with well-known targets with different sizes that were made from water-equivalent material and inserted in foam to simula...

To develop accurate three-dimensional (3D) empirical dose calculation model for kV diagnostic beams for different radiographic and CT imaging techniques. Dose was modeled using photon attenuation measured using depth dose (DD), scatter radiation of the source and medium, and off-axis ratio (OAR) profiles. Measurements were performed using single-di...

The purpose of this study was to investigate quantitatively by measurement and modeling the variations in CT number distributions of mobile targets in cone-beam CT (CBCT) imaging. CBCT images were acquired for three targets manufactured from homogenous water-equivalent gel that was inserted into a commercial mobile thorax phantom. The phantom moved...

To investigate the doses received by the hippocampus and normal brain tissue during a course of stereotactic radiation therapy using a single isocenter (SI)-based or multiple isocenter (MI)-based treatment planning in patients with less than 4 brain metastases. In total, 10 patients with magnetic resonance imaging (MRI) demonstrating 2-3 brain meta...

The purpose of this study was to assess quantitatively elongation of mobile targets in cone‐beam CT (CBCT) imaging by measurement and modeling. A mathematical model was derived that predicts the measured lengths of mobile targets and its dependence on target size and motion patterns in CBCT imaging. Three tissue‐equivalent targets of differing size...

Purpose: To determine dosimetric impact of positioning errors in the stereotactic hypo-fractionated treatment of intracranial lesions using 3Dtransaltional and 3D-rotational corrections (6D) frameless BrainLAB ExacTrac X-Ray system.

Purpose: To investigate the dosimetric accuracy of multiple-diode-array detector (Mapcheck2) for high-dose-rate brachytherapy Ir-192 source. The two-dimensional (2D) dose distributions measured with MapCheck2 were validated with EBT2 Gafchromic film measurement and AAPM task-group- 43 (TG-43) modeling.

Purpose: To investigate the doses received by the hippocampus and normal brain tissue during a course of stereotactic radiotherapy utilizing a single isocenter (SI) versus multiple isocenter (MI) in patients with multiple intracranial metastases. Methods: Seven patients imaged with MRI including SPGR sequence and diagnosed with 2?3 brain metastases...

Purpose: A motion algorithm was developed to extract actual length, CT-numbers and motion amplitude of a mobile target imaged with cone-beam-CT (CBCT) retrospective to image-reconstruction. Methods: The motion model considered a mobile target moving with a sinusoidal motion and employed three measurable parameters: apparent length, CT number level...

Purpose: To investigate quantitatively patient motion effects on the localization accuracy of image-guided radiation with fiducial markers using axial CT (ACT), helical CT (HCT) and cone-beam CT (CBCT) using modeling and experimental phantom studies. Methods: Markers with different lengths (2.5 mm, 5 mm, 10 mm, and 20 mm) were inserted in a mobile...

Purpose: To evaluate setup accuracy and quantify individual systematic and random errors for the various hardware and software components of the frameless 6D-BrainLAB ExacTrac system. Methods: 35 patients with cranial lesions, some with multiple isocenters (50 total lesions treated in 1, 3, 5 fractions), were investigated. All patients were simulat...

Purpose: To investigate quantitatively the variations in dose-distributions induced by motion by measurements and modeling. A four-dimensional (4D) motion model of dose distributions that accounts for different motion parameters was developed. Methods: Variations in dose distributions induced by sinusoidal phantom motion were measured using a multi...

Purpose To assess the impacts that multileaf collimator (MLC) leaf width has on the dose conformity and normal brain tissue doses of single and multiple isocenter stereotactic IMRT (SRT) plans for multiple intracranial tumors. Methods Fourteen patients with 2–3 targets were studied retrospectively. Patients treated with multiple isocenter treatmen...

Purpose: To investigate variations in mobile target length induced by sinusoidal motion in helical (HCT) and axial CT (ACT) imaging. A mathematical model was derived that predicts the measured broadening of the apparent lengths of mobile targets and its dependence on motion parameters, target size, and imaging couch speed in CT images. Materials...

The purpose of this study was to assess quantitatively elongation of mobile targets in cone‐beam CT (CBCT) imaging by measurement and modeling. A mathematical model was derived that predicts the measured lengths of mobile targets and its dependence on target size and motion patterns in CBCT imaging. Three tissue‐equivalent targets of differing size...

IntroductionWe aim to quantify the variations in the gross tumour volume (GTV) during a course of stereotactic body radiotherapy (SBRT) and determine its impact on dosimetric coverage of the GTV. Methods The GTVs and dose coverage for 14 patients with 16 primary non-small-cell lung tumours treated with SBRT were investigated. Initial GTVs were calc...

Purpose: To evaluate dosimetric accuracy of a multiple-diode array detector (MapCHECK2 ) for high-dose-rate (HDR) brachytherapy Ir-192 source using two-dimensional dose distributions measured with MapCHECK2, EBT2 Gafchromic films, and TG-43 calculations. Materials and methods: Plans with different patterns of dwell positions and times were deliv...

Purpose: To assess by measurement the quantitative variations in dose distributions for different motion patterns. Mathematical modeling of dose variations induced by motion was developed. Materials and methods: The dose distributions from various plans that included open and intensity-modulated fields were measured using a multiple-diode-array...

Purpose: To investigate quantitatively the variations of gross tumor volume (GTV) as a function of time and cumulative dose during radiotherapy treatment and evaluate corresponding tumor control probability (TCP) in non‐small cell lung carcinoma (NSCLC). Methods and Materials: CT and cone‐beam CT images for 20‐patients NSCLC were reviewed, retrospe...

Purpose: To compare quality of single and multiple isocenter stereotactic IMRT treatment plans for multiple intracranial targets. Methods: Five patients (two with three and three with two brain metastatic tumors) treated with multiple isocenters using 9 to 12 non-coplanar beams per lesion were replanned for single isocenter 10 to 12 non-coplanar...

The purpose of this study was to investigate quantitatively by measurement and modeling the variations in CT number distributions of mobile targets in cone-beam CT (CBCT) imaging. CBCT images were acquired for three targets manufactured from homogenous water-equivalent gel that was inserted into a commercial mobile thorax phantom. The phantom moved...

To compare the doses calculated using the BrainLAB pencil beam (PB) and Monte Carlo (MC) algorithms for tumors located in various sites including the lung and evaluate quality assurance procedures required for the verification of the accuracy of dose calculation. The dose-calculation accuracy of PB and MC was also assessed quantitatively with measu...

Purpose: To investigate enlargement of prostate volume by edema during brachytherapy seed implantation and develop a nomogram model to calculate air-kerma strength (AKS) required for implantation of the enlarged transient prostatic volume. Materials and Methods: The prostate volume was measured prior and after seed implantation using trans-rectal u...

Purpose: To determine localization errors of fiducial markers using axial (ACT) and helical CT (HCT), cone beam CT (CBCT) and kV imaging. Methods and Materials: A thorax phantom containing markers of various sizes (2.5, 5, 10, 20mm) was imaged using ACT, HCT, CBCT and kV imaging. The phantom was imaged with and without motion (15mm amplitude, 15 cy...

Purpose: CT number variations due to image artifacts induced by respiratory motion in CT and cone-beam CT (CBCT) imaging were investigated. A model was developed to predict CT number variations observed in CT and CBCT images. Method and Materials: Three target volumes of differing sizes were constructed of tissue-equivalent gel material and embedde...

Purpose: Variations in the target volume and length in CT and cone-beam CT (CBCT) imaging by respiratory motion were investigated for different motion amplitude and frequency. A model that predicts the target volume dependence on motion amplitude, frequency, target size, speed of CT and CBCT scanning was developed. Method and Materials: Three targe...

Purpose: Evaluate the dosimetric impact of daily setup error and inter-fraction organ motion on the radiation treatment plan. Methods: Twelve patients undergoing definitive IMRT treatments for prostate cancer were evaluated. All patients underwent fiducial marker placement prior to treatment planning CT scan, and were treated to a dose of 8100cGy g...

Purpose: To investigate the dose rate and energy dependence of dosimetric systems radiographic film (EDR2), Gafchromic films (EBT, EBT2), and MapCheck2 diode system, using regular and flattening-filter-free (FFF) profiles from a Varian TrueBeam system. Methods: EBT, EBT2, EDR2 films and Mapcheck2 were exposed to open field regular beams with energi...

Purpose: Clinically relevant dose errors of small field brain IMRT were evaluated using planar per-beam dosimetry and planned dose perturbation (PDP; used in the Sun Nuclear 3DVH+MapCHEKC2) algorithm. Methods: Ten BrainLAB IMRT plans were retrospectively selected. PTVs ranged from 0.5 to 29.0 cc and most of the field sizes were smaller than 4×4 cm(...

Purpose: To investigate effects of metal artifacts on the dose calculation accuracy of three dose calculation algorithms on CT and cone-beam CT images. Methods: A phantom with and without metal objects was scanned using CT simulator and on-board kV CBCT. Conformal 5-field treatment plans with identical physical and dosimetric parameters were create...

The purpose of this study was to evaluate the impact of daily setup error and interfraction organ motion on the overall dosimetric radiation treatment plans. Twelve patients undergoing definitive intensity-modulated radiation therapy (IMRT) treatments for prostate cancer were evaluated in this institutional review board-approved study. Each patient...

With increasing popularity and complexity of intensity-modulated radiation therapy (IMRT) delivery modalities including regular and arc therapies, there is a growing challenge for validating the accuracy of dose distributions. Gafchromic films have superior characteristics for dose verification over other conventional dosimeters. In order to optimi...

Purpose: To quantify the dose differences between cone‐beam CT(CBCT) and conventional CT(CT) using dose calculation with pencil beam convolution (PBC) and analytical anisotropic algorithm (AAA). Methods: CBCT obtained from a kV on‐board imager integrated with a Varian Trilogy linear accelerator was used for dose calculation. CBCT and CTimages for 8...

Purpose: To investigate correlation of standard?uptake values (SUV) from post?treatment PETimaging representing clinical complications such as muscular inflammation with dose delivered in non?small cell lungcancer patients treated with large hypo?fractions using stereotactic body radiation therapy(SBRT). Method and Materials: Clinical complications...

Purpose: To measure quantitatively in‐vivo shrinkage of gross tumor volume (GTV) using CTimaging and model GTV as a function of delivereddose during treatment. Methods: The GTV of three selected non‐small cell lungtumors were outlined on CTimages acquired weekly during treatment course with regular fractionated regimens of 180 cGy over 35 fractions...

Purpose: To investigate the effects of optical density (OD) sensitivity and growth with time post?irradiation on intensity?modulated radiation therapy(IMRT)dosimetry with gafchromic films (EBT1 and EBT2). Method and Materials:EBT1 and EBT2 films were used to perform IMRTquality assurance, which were exposed to IMRT plans created in treatment planni...

The purpose of this work is to extract three-dimensional (3D) motion trajectories of internal implanted and external skin-attached markers from kV cone-beam projections and reduce image artifact from patient motion in cone-beam computed tomography (CBCT) from on-board imager. Cone beam radiographic projections were acquired for a mobile phantom and...

Purpose: To investigate image artifacts caused by a standard treatment couch on cone-beam CT (CBCT) images from a kV on-board imager and to develop an algorithm based on spatial domain filtering to remove image artifacts in CBCT induced by the treatment couch. Methods: Image artifacts in CBCT induced by the treatment couch were quantified by scanni...

To investigate image artifacts caused by a standard treatment couch on cone-beam CT (CBCT) images from a kV on-board imager and to develop an algorithm based on spatial domain filtering to remove image artifacts in CBCT induced by the treatment couch. Image artifacts in CBCT induced by the treatment couch were quantified by scanning a phantom used...

To investigate quantitatively the deformation of the mammosite balloon, eccentricity of the source position and their effects on the dose delivered to the tumor lumpectomy site and critical structures. The distances of the brachytherapy source to the surface of the mammosite balloon were measured in using radiographic images for fractions 1 to 10 f...

Purpose: To compare and assess accuracy of the doses calculated using the BrainLAB pencil beam (PB) and Monte Carlo(MC) algorithms for lung, prostate, brain, head and neck and paraspinal tumors.Methods and Material: Dose was calculated using PB convolution and MC algorithms in the IPLAN treatment planning system from BrainLAB for 5 lungs, 3 brains,...

Purpose: Single photon emission tomography(SPECT) was used to measure the distribution of radioactivity and obtain quantitative air‐kerma strength (AKS) of the seeds implanted in low‐dose rate prostate brachytherapy. A fast 3D discrete Fourier‐transform convolution algorithm that uses quantitative SPECT numbers was developed to calculate internal d...

The purpose of this study was to evaluate setup accuracy and quantify random and systematic errors of the BrainLAB stereotactic immobilization mask and localization system using kV on-board imaging. Nine patients were simulated and set up with the BrainLAB stereotactic head immobilization mask and localizer to be treated for brain lesions using sin...

Purpose: To investigate the increase in surface dose under immobilization thermoplastic masks by measurements and calculation in the build-up region using Gafchromic films and Monte Carlo simulation. Materials and methods: Surface doses were measured underneath three thermoplastic masks in open fields using 6 and 18 MV photon beams. These masks are...

To investigate the increase in surface dose under immobilization thermoplastic masks by measurements and calculation in the build-up region using Gafchromic films and Monte Carlo simulation. Surface doses were measured underneath three thermoplastic masks in open fields using 6 and 18 MV photon beams. These masks are used to immobilize patients for...

This work investigates variation in the volume of the prostate measured at different stages through the prostate brachytherapy procedure for 30 patients treated with I-125 radioactive seeds. The implanted seeds were localized on post-implantation ultrasound (US) images and the effect of prostate enlargement due to edema on dose coverage for 15 pati...

Purpose: To evaluate setup accuracy of the BrainLAB stereotactic radiotherapy head immobilization mask using orthogonal projections from on?board imaging.Materials and Methods: Eight patients were simulated and treated with the BrainLAB stereotactic head immobilization masks and CT?localizers for brain lesions using single and hypo?fractions. Ortho...

Purpose: To evaluate setup accuracy of the BrainLAB stereotactic radiotherapy head immobilization mask using orthogonal projections from on?board imaging.Materials and Methods: Eight patients were simulated and treated with the BrainLAB stereotactic head immobilization masks and CT?localizers for brain lesions using single and hypo?fractions. Ortho...

To investigate the effects of sagging shifts of three on-board kV imaging systems (OBI) on the isocenter positioning accuracy and image quality of cone-beam CT (CBCT). A cubical phantom having a metal marker in the center that can be aligned with the radiation isocenter was used to measure sagging shifts and their variation with gantry angle on thr...

It is well known that optical density (OD) of the radiochromic film (RCF) continues to grow after exposure at rates that have a complex dependence on dose, temperature, and densitometry wavelength. Dose rate and fractionation artifacts associated with variations in OD growth may limit the accuracy achievable by RCF dosimetry in brachytherapy and ex...

It is well known that optical density (OD) of the radiochromic film (RCF) continues to grow after exposure at rates that have a complex dependence on dose, temperature, and densitometry wavelength. Dose rate and fractionation artifacts associated with variations in OD growth may limit the accuracy achievable by RCF dosimetry in brachytherapy and ex...

Implanted gold markers and megavoltage (MV) portal imaging are commonly used for setup verification of paraspinal tumors treated with high-dose, single-fraction radiotherapy. We investigated whether the use of kilovoltage cone-beam computed tomography (CBCT) imaging eliminates the need for marker implantation. Patients with paraspinal disease who w...

Purpose: To study correlation of internal implanted vs. external skin markers for tracking respiratory motion in liver patients using radiographic projections from on?board kV cone?beam scans. Material and Method: Cone?beam projections were analyzed to extract 3D?motion of internal and external markers for five liver patients receiving hypofraction...

Radiochromic film (RCF) has been shown to be a precise and accurate two‐dimensional dosimeter for acute exposure radiation fields. However, “temporal history” mismatch between calibration and brachytherapy films due to RCF dose‐rate effects could introduce potentially large uncertainties in low dose‐rate (LDR) brachytherapy absolute dose measuremen...

Purpose: To evaluate artifacts caused by treatment couch attenuation on 3D image reconstruction for a new kV on‐board‐imager (OBI) and cone beam CT(CBCT) system and to develop an algorithm that filters couch effects from two‐dimensional radiographic projections prior to inputting to the 3D reconstruction algorithm. Material and methods: A standard...

Purpose: To develop Quality Assurance (QA) procedures that monitor mechanical stability and image quality performance of a new kV on?board?imager (OBI) and cone beam CT(CBCT) system. Material and Methods: QA of mechanical stability includes measurements of the OBI kV and Linac MV isocenters, shifts resulting from gantry rotation, translational of i...

Purpose: To quantify the geometric accuracy of the On Board Imager in both the kV radiographic and cone beam imaging modes. Method and Materials: The Winston‐Lutz test was performed to localize a 5mm tungsten sphere placed within +/− 0.25 mm of the radiation isocenter. The sphere was imaged with half fan cone beam scans, and kV radiographs at the 4...