Simulated Online Adaptive Magnetic Resonance-Guided Stereotactic Body Radiation Therapy for the Treatment of Oligometastatic Disease of the Abdomen and Central Thorax: Characterization of Potential Advantages.

Purpose: To characterize potential advantages of online-adaptive magnetic resonance (MR)-guided stereotactic body radiation therapy (SBRT) to treat oligometastatic disease of the non-liver abdomen and central thorax.

Methods And Materials: Ten patients treated with RT for unresectable primary or oligometastatic disease of the non-liver abdomen (n=5) or central thorax (n=5) underwent imaging throughout treatment on a clinical MR image guided RT system. The SBRT plans were created on the basis of tumor/organ at risk (OAR) anatomy at initial computed tomography simulation (P), and simulated adaptive plans were created on the basis of observed MR image set tumor/OAR "anatomy of the day" (P).

A GPU-accelerated Monte Carlo dose calculation platform and its application toward validating an MRI-guided radiation therapy beam model.

Purpose: The clinical commissioning of IMRT subject to a magnetic field is challenging. The purpose of this work is to develop a GPU-accelerated Monte Carlo dose calculation platform based on penelope and then use the platform to validate a vendor-provided MRIdian head model toward quality assurance of clinical IMRT treatment plans subject to a 0.35 T magnetic field.

A software tool to automatically assure and report daily treatment deliveries by a cobalt-60 radiation therapy device.

The aims of this study were to develop a method for automatic and immediate verification of treatment delivery after each treatment fraction in order to detect and correct errors, and to develop a comprehensive daily report which includes delivery verification results, daily image-guided radiation therapy (IGRT) review, and information for weekly physics reviews. After systematically analyzing the requirements for treatment delivery verification and understanding the available information from a commercial MRI-guided radiotherapy treatment machine, we designed a procedure to use 1) treatment plan files, 2) delivery log files, and 3) beam output information to verify the accuracy and completeness of each daily treatment delivery. The procedure verifies the correctness of delivered treatment plan parameters including beams, beam segments and, for each segment, the beam-on time and MLC leaf positions.

Methods to model and predict the ViewRay treatment deliveries to aid patient scheduling and treatment planning.

A software tool is developed, given a new treatment plan, to predict treatment delivery time for radiation therapy (RT) treatments of patients on ViewRay magnetic resonance image-guided radiation therapy (MR-IGRT) delivery system. This tool is necessary for managing patient treatment scheduling in our clinic. The predicted treatment delivery time and the assessment of plan complexities could also be useful to aid treatment planning.

A comparative study of automatic image segmentation algorithms for target tracking in MR-IGRT.

On-board magnetic resonance (MR) image guidance during radiation therapy offers the potential for more accurate treatment delivery. To utilize the real-time image information, a crucial prerequisite is the ability to successfully segment and track regions of interest (ROI). The purpose of this work is to evaluate the performance of different segmentation algorithms using motion images (4 frames per second) acquired using a MR image-guided radiotherapy (MR-IGRT) system.

Online Magnetic Resonance Image Guided Adaptive Radiation Therapy: First Clinical Applications.

Purpose: To demonstrate the feasibility of online adaptive magnetic resonance (MR) image guided radiation therapy (MR-IGRT) through reporting of our initial clinical experience and workflow considerations.

Methods And Materials: The first clinically deployed online adaptive MR-IGRT system consisted of a split 0.35T MR scanner straddling a ring gantry with 3 multileaf collimator-equipped (60)Co heads.

Characterization of the onboard imaging unit for the first clinical magnetic resonance image guided radiation therapy system.

Purpose: To characterize the performance of the onboard imaging unit for the first clinical magnetic resonance image guided radiation therapy (MR-IGRT) system.

Methods: The imaging performance characterization included four components: ACR (the American College of Radiology) phantom test, spatial integrity, coil signal to noise ratio (SNR) and uniformity, and magnetic field homogeneity. The ACR phantom test was performed in accordance with the ACR phantom test guidance.

Quality of Intensity Modulated Radiation Therapy Treatment Plans Using a ⁶⁰Co Magnetic Resonance Image Guidance Radiation Therapy System.

Purpose: This work describes a commercial treatment planning system, its technical features, and its capabilities for creating (60)Co intensity modulated radiation therapy (IMRT) treatment plans for a magnetic resonance image guidance radiation therapy (MR-IGRT) system.

Methods And Materials: The ViewRay treatment planning system (Oakwood Village, OH) was used to create (60)Co IMRT treatment plans for 33 cancer patients with disease in the abdominal, pelvic, thorax, and head and neck regions using physician-specified patient-specific target coverage and organ at risk (OAR) objectives. Backup plans using a third-party linear accelerator (linac)-based planning system were also created.

Benchmark IMRT evaluation of a Co-60 MRI-guided radiation therapy system.

A device for MRI-guided radiation therapy (MR-IGRT) that uses cobalt-60 sources to deliver intensity modulated radiation therapy is now commercially available. We investigated the performance of the treatment planning and delivery system against the benchmark recommended by the American Association of Physicists in Medicine (AAPM) Task Group 119 for IMRT commissioning and demonstrated that the device plans and delivers IMRT treatments within recommended confidence limits and with similar accuracy as linac IMRT.

Magnetic resonance imaging-based treatment planning for prostate cancer: Use of population average tissue densities within the irradiated volume to improve plan accuracy.

Purpose: The purpose of this study was to investigate the feasibility of using population average tissue densities within the irradiated volume to improve the dosimetric accuracy of magnetic resonance imaging-based treatment plans for prostate cancer.

Methods And Materials: Computed tomography images and radiation therapy treatment plans from 20 patients with prostate cancer were reviewed retrospectively. Patient anatomy was segmented into fat, nonfat soft tissue, and bone.

Patient-specific quality assurance for the delivery of (60)Co intensity modulated radiation therapy subject to a 0.35-T lateral magnetic field.

Purpose: This work describes a patient-specific dosimetry quality assurance (QA) program for intensity modulated radiation therapy (IMRT) using ViewRay, the first commercial magnetic resonance imaging-guided RT device.

Methods And Materials: The program consisted of: (1) a 1-dimensional multipoint ionization chamber measurement using a customized 15-cm(3) cube-shaped phantom; (2) 2-dimensional (2D) radiographic film measurement using a 30- × 30- × 20-cm(3) phantom with multiple inserted ionization chambers; (3) quasi-3D diode array (ArcCHECK) measurement with a centrally inserted ionization chamber; (4) 2D fluence verification using machine delivery log files; and (5) 3D Monte Carlo (MC) dose reconstruction with machine delivery files and phantom CT.

Results: Ionization chamber measurements agreed well with treatment planning system (TPS)-computed doses in all phantom geometries where the mean ± SD difference was 0.

Automated radiation therapy treatment plan workflow using a commercial application programming interface.

Purpose: The objective of this study was to create a workflow for the automation and standardization of treatment plan generation and evaluation using an application programming interface (API) to access data from a commercial treatment planning system (Varian Medical Systems, Inc, Palo Alto, CA).

Methods And Materials: The automation workflow begins with converting electronic patient-specific physician treatment planning orders that specify demographics, simulation instructions, and dosimetric objectives for targets and organs at risk into XML files. These XML files are used to generate standard contour names, beam, and patient-specific intensity modulated radiation therapy (IMRT) optimization templates to be executed in a commercial treatment planning system (TPS) by the user.

Initial experience with TrueBeam trajectory log files for radiation therapy delivery verification.

Purpose: Traditionally, initial and weekly chart checks involve checking various parameters in the treatment management system against the expected treatment parameters and machine settings. This process is time-consuming and labor intensive. We explore utilizing the Varian TrueBeam log files (Varian Medical System, Palo Alto, CA), which contain the complete delivery parameters for an end-to-end verification of daily patient treatments.

Catching errors with patient-specific pretreatment machine log file analysis.

Purpose: A robust, efficient, and reliable quality assurance (QA) process is highly desired for modern external beam radiation therapy treatments. Here, we report the results of a semiautomatic, pretreatment, patient-specific QA process based on dynamic machine log file analysis clinically implemented for intensity modulated radiation therapy (IMRT) treatments delivered by high energy linear accelerators (Varian 2100/2300 EX, Trilogy, iX-D, Varian Medical Systems Inc, Palo Alto, CA). The multileaf collimator machine (MLC) log files are called Dynalog by Varian.

The use of exit detector sinograms to detect anatomical variations for patients extending beyond the TomoTherapy field of view: a feasibility study.

Purpose: This work describes an independent method to use the TomoTherapy Hi-ART megavoltage CT imaging system for daily monitoring of anatomical changes of cancer patients whose anatomy extends beyond the imaging field of view.

Methods: The imaging detector response to changes in attenuating media was measured using water-equivalent plastic. Weight loss was simulated using an anthropomorphic phantom and determining the system's ability to detect the weight loss.

Evaluation of the efficiency and effectiveness of independent dose calculation followed by machine log file analysis against conventional measurement based IMRT QA.

Experimental methods are commonly used for patient-specific IMRT delivery verification. There are a variety of IMRT QA techniques which have been proposed and clinically used with a common understanding that not one single method can detect all possible errors. The aim of this work was to compare the efficiency and effectiveness of independent dose calculation followed by machine log file analysis to conventional measurement-based methods in detecting errors in IMRT delivery.

A monthly quality assurance procedure for 3D surface imaging.

A procedure for periodic quality assurance of a video surface imaging system is introduced. AlignRT is a video camera-based patient localization system that captures and compares images of a patient's topography to a DICOM-formatted external contour, then calculates shifts required to accurately reposition the patient. This technical note describes the tools and methods implemented in our department to verify correct and accurate operation of the AlignRT hardware and software components.

A time-dependent dose model for glovebox processing of fissile material.

A new modeling system for high-intensity neutral particle radiation fields is presented. The code PANDEMONIUM calculates external effective dose rates from neutrons and photons produced at specific locations within an industrial-size plutonium processing facility. The new version of PANDEMONIUM introduces time-dependent neutronics for source multiplication coupled with transient source and detector positions.