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Publications (301)
Background:
Stereotactic ablative radiotherapy (SABR) is the standard treatment for medically inoperable early-stage non-small-cell lung cancer (NSCLC), but regional or distant relapses, or both, are common. Immunotherapy reduces recurrence and improves survival in people with stage III NSCLC after chemoradiotherapy, but its utility in stage I and...
Purpose:
To quantify the potential error in outputs for flattening filter free (FFF) beams associated with use of a lead foil in beam quality determination per the addendum protocol for TG-51, we examined differences in measurements of the beam quality conversion factor kQ when using or not using lead foil.
Methods:
Two FFF beams, a 6 MV FFF and...
Purpose
We investigated the feasibility of biology-guided radiotherapy (BgRT), a technique that utilizes real-time positron emission imaging to minimize tumor motion uncertainties, to spare nearby organs at risk.
Methods
Volumetric modulated arc therapy (VMAT), intensity-modulated proton (IMPT) therapy, and BgRT plans were created for a paratrache...
Purpose:
To better meet clinical needs and facilitate optimal treatment planning, we added two new electron energy beams (7 and 11 MeV) to two Varian TrueBeam linacs.
Methods:
We worked with the vendor to create two additional customized electron energies without hardware modifications. For each beam, we set the bending magnet current and then o...
Purpose
In this study, we applied the failure mode and effects analysis (FMEA) approach to an automated radiation therapy contouring and treatment planning tool to assess, and subsequently limit, the risk of deploying automated tools.
Methods and Materials
Using an FMEA, we quantified the risks associated with the Radiation Planning Assistant (RPA...
Purpose: Radiation epidemiology studies of childhood cancer survivors treated in the pre-computed tomography (CT) era reconstruct the patients’ treatment fields on computational phantoms. For such studies, the phantoms are commonly scaled to age at the time of radiotherapy treatment because age is the generally available anthropometric parameter. S...
Background
A previous pooled analysis of the STARS and ROSEL trials showed higher survival after stereotactic ablative radiotherapy (SABR) than with surgery for operable early-stage non-small-cell lung cancer (NSCLC), but that analysis had notable limitations. This study reports long-term results of the revised STARS trial, in which the SABR group...
Purpose:
Establish and compare two metrics for monitoring beam energy changes in the Halcyon platform and evaluate the accuracy of these metrics across multiple Halcyon linacs.
Method:
The first energy metric is derived from the diagonal normalized flatness (FDN ), which is defined as the ratio of the average measurements at a fixed off-axis equ...
Purpose
To provide a series of suggestions for other Medical Physics practices to follow in order to provide effective radiation therapy treatments during the COVID-19 pandemic.
Methods and Materials
We reviewed our entire Radiation Oncology infrastructure to identify a series of workflows and policy changes that we implemented during the pandemic...
With the advancement of data‐intensive technologies, such as image‐guided radiation therapy (IGRT) and intensity‐modulated radiation therapy (IMRT), the amount and complexity of data to be transferred between clinical subsystems have increased beyond the reach of manual checking. As a result, unintended treatment deviations (e.g., dose errors) may...
Purpose:
We previously developed an age-scalable 3D computational phantom that has been widely used for retrospective whole-body dose reconstructions of conventional two-dimensional historic radiation therapy (RT) treatments in late effects studies of childhood cancer survivors. This phantom is modeled in the FORTRAN programming language and is no...
Purpose
Between July 2013 and August 2019, 22% of the imaging and radiation oncology core (IROC) spine, and 15% of the moving lung phantom irradiations have failed to meet established acceptability criteria. The spine phantom simulates a highly modulated stereotactic body radiation therapy (SBRT) case, whereas the lung phantom represents a low‐to‐n...
Background & purpose:
Stereotactic ablative radiation therapy (SABR) is an emerging treatment option for patients with pulmonary metastases; identifying patients who would benefit from SABR can improve outcomes.
Materials & methods:
We retrospectively analyzed local failure (LF), distant failure (DF), overall survival (OS), and toxicity in 317 p...
Linac calibration is done in water, but patients are comprised primarily of soft tissue. Conceptually, and specified in NRG/RTOG trials, dose should be reported as dose‐to‐muscle to describe the dose to the patient. Historically, the dose‐to‐water of the linac calibration was often converted to dose‐to‐muscle for patient calculations through manual...
Validate that a two‐dimensional (2D) ionization chamber array (ICA) combined with a double‐wedge plate (DWP) can track changes in electron beam energy well within 2.0 mms as recommended by TG‐142 for monthly quality assurance (QA). Electron beam profiles of 4–22 MeV were measured for a 25 × 25 cm2 cone using an ICA with a DWP placed on top of it al...
We tested whether an ionization chamber array (ICA) and a one‐dimensional water scanner (1DS) could be used instead of a three‐dimensional water scanning system (3DWS) for acceptance testing and commissioning verification of the Varian Halcyon–Eclipse Treatment Planning System (TPS). The Halcyon linear accelerator has a single 6‐MV flattening‐filte...
The purpose of this study is to investigate the dosimetric impact of multi‐leaf collimator (MLC) positioning errors on a Varian Halcyon for both random and systematic errors, and to evaluate the effectiveness of portal dosimetry quality assurance in catching clinically significant changes caused by these errors. Both random and systematic errors we...
Purpose
Breast cancer is the most common cancer in women globally and radiation therapy is a cornerstone of its treatment. However, there is an enormous shortage of radiotherapy staff, especially in low‐ and middle‐income countries. This shortage could be ameliorated through increased automation in the radiation treatment planning process, which ma...
A large number of surveys have been sent to the medical physics community addressing many clinical topics for which the medical physicist is, or may be, responsible. Each survey provides an insight into clinical practice relevant to the medical physics community. The goal of this study was to create a summary of these surveys giving a snapshot of c...
Data S1. Tabulated responses to all multiple choice surveys analyzed.
Background and purpose
Postmastectomy radiotherapy (PMRT) is complex to plan and deliver, but could be improved with 3D-printed, patient-specific electron tissue compensators. The purposes of this study were to develop an algorithm to design patient-specific compensators that achieve clinical goals, to 3D-print the planned compensators, and validat...
Background:
Current standard radiotherapy for oropharynx cancer (OPC) is associated with high rates of severe toxicities, shown to adversely impact patients' quality of life. Given excellent outcomes of human papilloma virus (HPV)-associated OPC and long-term survival of these typically young patients, treatment de-intensification aimed at improvi...
Purpose:
To evaluate the ability of the machine performance check (MPC) on the Halcyon to detect errors, with comparison with the TrueBeam.
Methods:
MPC is an automated set of quality assurance (QA) tests that use a phantom placed on the couch and the linac's imaging system(s) to verify the beam constancy and mechanical performance of the Halcyo...
Purpose
We assessed automated contouring of normal structures for patients with head-and-neck cancer (HNC) using a multiatlas deformable-image-registration algorithm to better provide a fully automated radiation treatment planning solution for low- and middle-income countries, provide quantitative analysis, and determine acceptability worldwide.
M...
The Radiation Planning Assistant (RPA) is a system developed for the fully automated creation of radiotherapy treatment plans, including volume-modulated arc therapy (VMAT) plans for patients with head/neck cancer and 4-field box plans for patients with cervical cancer. It is a combination of specially developed in-house software that uses an appli...
We developed a novel technique to study the impact of geometric distortion of magnetic resonance imaging (MRI) on intensity-modulated radiation therapy treatment planning.
The measured 3D datasets of residual geometric distortion (a 1.5-T MRI component of an MRI linear accelerator system) was fitted with a second-order polynomial model to map the s...
Purpose:
Using a new linear accelerator with high dose rate (800 MU/min), fast MLC motions (5.0cm/s), fast gantry rotation (15sec/rotation), and 1cm wide MLCs, we aimed to quantify the effects of complexity, arc number, and fractionation on interplay for breast and lung treatments under target motion.
Methods:
To study lung interplay, eight VMAT...
Routine quality assurance for linear accelerators (linacs) usually involves verification of beam steering with a water scanning system. We established a beam steering procedure that uses a 2D ionization chamber array (ICA) and verified the equivalence of beam symmetry between the ICA and a water scanning system. The ICA calibration accuracy, reprod...
Purpose:
The purpose of this study was to develop and test a set of illustrated instructions for effective training for mechanical quality assurance (QA) of medical linear accelerators (linac).
Methods:
Illustrated instructions were created for mechanical QA and underwent several steps of review, testing, and refinement. Eleven testers with no r...
Purpose:
The aim of this study was to measure and compare the mega-voltage imaging dose from the Halcyon medical linear accelerator (Varian Medical Systems) with measured imaging doses with the dose calculated by Eclipse treatment planning system.
Methods:
An anthropomorphic thorax phantom was imaged using all imaging techniques available with t...
Purpose
To report the feasibility of conducting a randomized study to compare the toxicity and efficacy of stereotactic body radiotherapy (SBRT) versus stereotactic body proton therapy (SBPT) for high-risk medically inoperable early-stage non-small cell lung cancer (NSCLC).
Methods and Materials
We randomly assigned patients with medically inopera...
Purpose
To develop a practical approach for accurate contour deformation when deformable image registration (DIR) is used for atlas‐based segmentation or contour propagation in image‐guided radiotherapy.
Methods
We developed a contour deformation approach based on 3D mesh operations. The 2D contours represented by a series of points in each slice...
In radiation treatment planning, the esophagus is an important organ-at-risk that should be spared in patients with head and neck cancer or thoracic cancer who undergo intensity-modulated radiation therapy. However, automatic segmentation of the esophagus from CT scans is extremely challenging because of the structure's inconsistent intensity, low...
Purpose:
The objective of this work was to assess both the perception of failure modes in Intensity Modulated Radiation Therapy (IMRT) when the linac is operated at the edge of tolerance given in AAPM TG-40(1) and TG-142(2) as well as the application of FMEA to this specific section of the IMRT process.
Methods:
An online survey was distributed...
Radiomics is the use of quantitative imaging features extracted from medical images to characterize tumor pathology or heterogeneity. Features measured at pretreatment have successfully predicted patient outcomes in numerous cancer sites. This project was designed to determine whether radiomics features measured from non–small cell lung cancer (NSC...
Background:
The authors evaluated the efficacy, patterns of failure, and toxicity of stereotactic ablative radiotherapy (SABR) for patients with medically inoperable, clinical stage I non-small cell lung cancer (NSCLC) in a prospective clinical trial with 7 years of follow-up. Clinical staging was performed according to the seventh edition of the...
Objectives:
Our goal was to evaluate stereotactic ablative radiotherapy (SABR) as a salvage option for isolated recurrence of non-small-cell lung cancer (NSCLC) in the lung parenchyma following definitive treatment of stage I-III disease.
Methods:
Patients who had histologically confirmed, positron emission tomography (PET) staged, isolated NSCL...
Purpose: The efficiency of radiation delivery via volumetric modulated arc therapy (VMAT) is indisputable, but outcomes after VMAT for thoracic esophageal carcinoma are largely unknown.
Methods and materials: We retrospectively analyzed 65 patients with thoracic esophageal cancer who received VMAT to 50.4 Gy (range, 45-50.4 Gy) with concurrent chem...
Radiotherapy in a seated position may be indicated for patients who are unable to lie on the treatment couch for the duration of treatment, in scenarios where a seated treatment position provides superior anatomical positioning and dose distributions, or for a low-cost system designed using a fixed treatment beam and rotating seated patient. In thi...
PurposeMore than 6,500 megavoltage teletherapy units are needed worldwide, many in low-resource settings. Cobalt-60 units or linear accelerators (linacs) can fill this need. We have evaluated machine performance on the basis of patient throughput to provide insight into machine viability under various conditions in such a way that conclusions can b...
Recently published Medical Physics Practice Guideline 5.a. (MPPG 5.a.) by American Association of Physicists in Medicine (AAPM) sets the minimum requirements for treatment planning system (TPS) dose algorithm commissioning and quality assurance (QA). The guideline recommends some validation tests and tolerances based primarily on published AAPM tas...
Introduction
We are using the Eclipse Application Programming Interface (API) and Mobius 3D QA system, together with in-house code, to develop an automated treatment planning system for cervix, breast (and chest wall), and head/neck cancers. The goal is to develop a system that includes multiple layers of internal QA that can be used by junior staf...
Purpose:
We report our single-institution experience with stereotactic ablative radiotherapy (SABR) for adrenal metastasis and identify factors influencing outcomes, patterns of failure, and dosimetric thresholds for toxicity.
Methods and materials:
We identified patients with adrenal metastases treated with SABR from 2009 to 2015. Toxicity was...
Background: Radiomics features have been used in a variety of studies to predict patient outcomes or aid in the diagnosis of non-small cell lung cancer. However, no guidelines exist for the best way to calculate these features to maximize their prognostic potential. The purpose of the current study was to evaluate how different image pre-processing...
Purpose:Newly published medical physics practice guideline (MPPG 5.a.) has set the minimum requirements for commissioning and QA of treatment planning dose calculations. We present our experience in the validation of a commercial treatment planning system based on MPPG 5.a.
Methods:In addition to tests traditionally performed to commission a model-...
Purpose:To evaluate correlation between the reproducibility of tumor position under feedback guided voluntary deep inspiration breath hold gating at simulation and at treatment.
Methods:All patients treated with breath hold (BH) have 3-6 BH CTs taken at simulation (sim). In addition, if the relationship between the tumor and nearby bony anatomy on...
Purpose:To determine how radiomics features change during radiation therapy and whether those changes (delta-radiomics features) can improve prognostic models built with clinical factors.
Methods:62 radiomics features, including histogram, co-occurrence, run-length, gray-tone difference, and shape features, were calculated from pretreatment and wee...
Purpose:For some head and neck patients, positioning in the supine position is not well tolerated. For these patients, treatment in a seated position would be preferred. We have evaluated inter- and intra- fraction uncertainty of patient set-up in a novel treatment chair which is compatible with modern linac designs.
Methods:Five head-and-neck canc...
Purpose:To investigate and validate the use of an independent deformable-based contouring algorithm for automatic verification of auto-contoured structures in the head and neck towards fully automated treatment planning.
Methods:Two independent automatic contouring algorithms [(1) Eclipse’s Smart Segmentation followed by pixel-wise majority voting,...
Purpose:To evaluate the dosimetric impact of MR image distortion in treatment planning.
Methods:Based on the realistic MRI distortion measurement data from an integrated MRI-Linac system, we created a generalized distortion model and applied it to CT images to simulate distorted MRI images. Ten patients with IMRT plans generated in Pinnacle treatme...
Purpose:To develop and test clear illustrated instructions for training of monthly mechanical QA of medical linear accelerators.
Methods:Illustrated instructions were created for monthly mechanical QA with tolerance tabulated, and underwent several steps of review and refinement. Testers with zero QA experience were then recruited from our radiothe...
Purpose:To develop and test two independent algorithms that automatically create the photon treatment fields for a four-field box beam arrangement, a common treatment technique for cervical cancer in low- and middle-income countries.
Methods:Two algorithms were developed and integrated into Eclipse using its Advanced Programming Interface:3D
Method...
Purpose:(A) To assess the role of Varian MPC in our daily QA routine, and (B) evaluate the accuracy and precision of MPC.
Methods:The MPC was performed weekly, for five months, on a Varian TrueBeam for five photon (6x, 10x, 15x, 6xFFF, and 10xFFF) and electron (6e, 9e, 12e, 16e, and 20e) energies. Output results were compared to those determined wi...
Purpose:
To identify the optimal dose parameters predictive for local/lobar control after stereotactic ablative radiation therapy (SABR) in early-stage non-small cell lung cancer (NSCLC).
Methods and materials:
This study encompassed a total of 1092 patients (1200 lesions) with NSCLC of clinical stage T1-T2 N0M0 who were treated with SABR of 50...
Purpose:
Increasing evidence suggests radiomics features extracted from computed tomography (CT)
images may be useful in prognostic models for patients with nonsmall cell lung
cancer
(NSCLC). This study was designed to determine whether such features can be reproducibly obtained from cone-beam CT
(CBCT)
images taken using medical Linac onboard-ima...
Scitation is the online home of leading journals and conference proceedings from AIP Publishing and AIP Member Societies
Four‐dimensional computed tomography (4D CT) is used to account for respiratory motion in radiation treatment planning, but artifacts resulting from the acquisition and postprocessing limit its accuracy. We investigated the efficacy of three experimental 4D CT acquisition methods to reduce artifacts in a prospective institutional review board appro...
The standard of care for operable, stage I, non-small-cell lung cancer (NSCLC) is lobectomy with mediastinal lymph node dissection or sampling. Stereotactic ablative radiotherapy (SABR) for inoperable stage I NSCLC has shown promising results, but two independent, randomised, phase 3 trials of SABR in patients with operable stage I NSCLC (STARS and...
To evaluate the performance of commercially available automatic segmentation tools built into treatment planning systems (TPS) in terms of their segmentation accuracy and flexibility in customization.
Twelve head-and-neck cancer patients and twelve thoracic cancer patients were retrospectively selected to benchmark the model-based segmentation (MBS...
Establish a procedure for beam steering and profile measurement using a 2D ionization chamber array and show equivalence to a water scanning system.
Multiple photon beams (30×30cm ((2)) field) and electron beams (25×25cm ((2)) cone) were steered in the radial and transverse directions using Sun Nuclear's IC PROFILER (ICP). Solid water was added dur...
Quantitatively assess the clinical impact of 11 critical IMRT dose delivery failure modes.
Eleven step-and-shoot IMRT failure modes (FMs) were introduced into twelve Pinnacle v9.8 treatment plans. One standard and one highly modulated plan on the IROC IMRT phantom and ten previous H&N patient treatment plans were used. FMs included physics componen...
To determine the best dosimetric metric measured by our routine QA devices for diagnosing photon target failure on a Varian C-series linac.
We have retrospectively reviewed and analyzed the dosimetry data from a Varian linac with a target degradation that was undiagnosed for one year. A failure in the daily QA symmetry tests was the first indicatio...
To assess the perception of TG-142 tolerance level dose delivery failures in IMRT and the application of FMEA process to this specific aspect of IMRT.
An online survey was distributed to medical physicists worldwide that briefly described 11 different failure modes (FMs) covered by basic quality assurance in step- and-shoot IMRT at or near TG-142 t...
To assess the feasibility of treating lung SBRT patients with the ipsilateral arm adducted beside the body instead of elevated above the head.
Patients receiving lung SBRT at our institution are typically treated with both arms raised above their head. However, several patients had difficulty maintaining their arms in an elevated position. In this...
To determine whether tumor volume plays a significant role in the values obtained for texture features when they are extracted from computed tomography (CT) images of non-small cell lung cancer (NSCLC). We also sought to identify whether features can be reliably measured at all volumes or if a minimum volume threshold should be recommended.
Eleven...
To compare image quality metrics and dose of TrueBeam V2.0's 2.5MV imaging beam and kV and 6MV images.
To evaluate the MV image quality, the Standard Imaging QC-3 and Varian Las Vegas (LV) phantoms were imaged using the 'quality' and 'low dose' modes and then processed using RIT113 V6.3. The LEEDS phantom was used to evaluate the kV image quality....
To develop a practical approach for accurate contour deformation when deformable image registration (DIR) is used for atlas-based segmentation or contour propagation in image-guided radiotherapy.
A contour deformation approach was developed on the basis of 3D mesh operations. The 2D contours represented by a series of points in each slice were firs...
