MOSFET dosimeter characterization in MR-guided radiation therapy (MRgRT) Linac.

Purpose: With the increasing use of MR-guided radiation therapy (MRgRT), it becomes important to understand and explore accuracy of medical dosimeters in the presence of magnetic field. The purpose of this work is to characterize metal-oxide-semiconductor field-effect transistors (MOSFETs) in MRgRT systems at 0.345 T magnetic field strength.

Characterization of positional accuracy of a double-focused and double-stack multileaf collimator on an MR-guided radiotherapy (MRgRT) Linac using an IC-profiler array.

Purpose: With advance magnetic resonance (MR)-guided online adaptive radiotherapy (MRgoART) relying on calculation-based intensity-modulated radiation therapy (IMRT) quality assurance (QA), accurate and sensitive QA of the multileaf collimator (MLC) becomes an increasingly essential component for routine machine QA. As such, it is important to assure compliance with the AAPM TG142 guidelines to supplement calculation-based QA methods for an online adaptive radiotherapy program. We have developed and implemented an efficient and highly sensitive QA procedure using an ionization chamber profiler (ICP) array to enable real-time characterization of the positional accuracy of a double-focused and double-stacked MLC on a clinical MR-guided radiotherapy (MRgRT) system and to supplement calculation-based QA for an MRgoART program.

A Multi-Institutional Experience of MR-Guided Liver Stereotactic Body Radiation Therapy.

Purpose: Daily magnetic resonance (MR)-guided radiation has the potential to improve stereotactic body radiation therapy (SBRT) for tumors of the liver. Magnetic resonance imaging (MRI) introduces unique variables that are untested clinically: electron return effect, MRI geometric distortion, MRI to radiation therapy isocenter uncertainty, multileaf collimator position error, and uncertainties with voxel size and tracking. All could lead to increased toxicity and/or local recurrences with SBRT.

A New Era of Image Guidance with Magnetic Resonance-guided Radiation Therapy for Abdominal and Thoracic Malignancies.

Magnetic resonance-guided radiation therapy (MRgRT) offers advantages for image guidance for radiotherapy treatments as compared to conventional computed tomography (CT)-based modalities. The superior soft tissue contrast of magnetic resonance (MR) enables an improved visualization of the gross tumor and adjacent normal tissues in the treatment of abdominal and thoracic malignancies. Online adaptive capabilities, coupled with advanced motion management of real-time tracking of the tumor, directly allow for high-precision inter-/intrafraction localization.

Dosimetric Comparison of Real-Time MRI-Guided Tri-Cobalt-60 Versus Linear Accelerator-Based Stereotactic Body Radiation Therapy Lung Cancer Plans.

Purpose: Magnetic resonance imaging-guided radiation therapy has entered clinical practice at several major treatment centers. Treatment of early-stage non-small cell lung cancer with stereotactic body radiation therapy is one potential application of this modality, as some form of respiratory motion management is important to address. We hypothesize that magnetic resonance imaging-guided tri-cobalt-60 radiation therapy can be used to generate clinically acceptable stereotactic body radiation therapy treatment plans.

Dosimetric differences in flattened and flattening filter-free beam treatment plans.

This study investigated the dosimetric differences in treatment plans from flattened and flattening filter-free (FFF) beams from the TrueBeam System. A total of 104 treatment plans with static (sliding window) intensity-modulated radiotherapy beams and volumetric-modulated arc therapy (VMAT) beams were generated for 15 patients involving three cancer sites. In general, the FFF beam provides similar target coverage as the flattened beam with improved dose sparing to organ-at-risk (OAR).

Characterization of a 0.35T MR system for phantom image quality stability and in vivo assessment of motion quantification.

ViewRay is a novel MR-guided radiotherapy system capable of imaging in near real-time at four frames per second during treatment using 0.35T field strength. It allows for improved gating techniques and adaptive radiotherapy.

Gadoxetate for direct tumor therapy and tracking with real-time MRI-guided stereotactic body radiation therapy of the liver.

SBRT is increasingly utilized in liver tumor treatment. MRI-guided RT allows for real-time MRI tracking during therapy. Liver tumors are often poorly visualized and most contrast agents are transient.

Rapid Automated Target Segmentation and Tracking on 4D Data without Initial Contours.

Purpose. To achieve rapid automated delineation of gross target volume (GTV) and to quantify changes in volume/position of the target for radiotherapy planning using four-dimensional (4D) CT. Methods and Materials.

A dose homogeneity and conformity evaluation between ViewRay and pinnacle-based linear accelerator IMRT treatment plans.

ViewRay, a novel technology providing soft-tissue imaging during radiotherapy is investigated for treatment planning capabilities assessing treatment plan dose homogeneity and conformity compared with linear accelerator plans. ViewRay offers both adaptive radiotherapy and image guidance. The combination of cobalt-60 (Co-60) with 0.

Dosimetric comparison of photon and proton treatment techniques for chondrosarcoma of thoracic spine.

Chondrosarcomas are relatively radiotherapy resistant, and also delivering high radiation doses is not feasible owing to anatomic constraints. In this study, the feasibility of helical tomotherapy for treatment of chondrosarcoma of thoracic spine is explored and compared with other available photon and proton radiotherapy techniques in the clinical setting. A patient was treated for high-grade chondrosarcoma of the thoracic spine using tomotherapy.

Feasibility study on effect and stability of adaptive radiotherapy on kilovoltage cone beam CT.

Background: We have analyzed the stability of CT to density curve of kilovoltage cone-beam computerized tomography (kV CBCT) imaging modality over the period of six months. We also, investigated the viability of using image value to density table (IVDT) generated at different time, for adaptive radiotherapy treatment planning. The consequences of target volume change and the efficacy of kV CBCT for adaptive planning issues is investigated.

Postmastectomy radiotherapy with integrated scar boost using helical tomotherapy.

The purpose of this study was to evaluate helical tomotherapy dosimetry in postmastectomy patients undergoing treatment for chest wall and positive nodal regions with simultaneous integrated boost (SIB) in the scar region using strip bolus. Six postmastectomy patients were scanned with a 5-mm-thick strip bolus covering the scar planning target volume (PTV) plus 2-cm margin. For all 6 cases, the chest wall received a total cumulative dose of 49.

Adaptive planning using megavoltage fan-beam CT for radiation therapy with testicular shielding.

This study highlights the use of adaptive planning to accommodate testicular shielding in helical tomotherapy for malignancies of the proximal thigh. Two cases of young men with large soft tissue sarcomas of the proximal thigh are presented. After multidisciplinary evaluation, preoperative radiation therapy was recommended.

A planning study for palliative spine treatment using StatRT and megavoltage CT simulation.

Megavoltage CT (MVCT) simulation on the TomoTherapy Hi·Art system is an alternative to conventional CT for treatment planning in the presence of severe metal artifact. StatRT is a new feature that was implemented on the TomoTherapy operator station for performing online MVCT scanning, treatment planning and treatment delivery in one session. The clinical feasibility of using the StatRT technique and MVCT simulation to palliative treatment for a patient with substantial spinal metallic hardware is described.

Dosimetric comparison of left-sided whole breast irradiation with 3DCRT, forward-planned IMRT, inverse-planned IMRT, helical tomotherapy, and topotherapy.

Background And Purpose: To compare left-sided whole breast conventional and intensity-modulated radiotherapy (IMRT) treatment planning techniques.

Materials And Methods: Treatment plans were created for 10 consecutive patients. Three-dimensional conformal radiotherapy (3DCRT), forward-planned IMRT (for-IMRT), and inverse-planned IMRT (inv-IMRT) used two tangent beams.

Helical tomotherapy versus single-arc intensity-modulated arc therapy: a collaborative dosimetric comparison between two institutions.

Purpose: Both helical tomotherapy (HT) and single-arc intensity-modulated arc therapy (IMAT) deliver radiation using rotational beams with multileaf collimators. We report a dual-institution study comparing dosimetric aspects of these two modalities.

Methods And Materials: Eight patients each were selected from the University of Maryland (UMM) and the University of Wisconsin Cancer Center Riverview (UWR), for a total of 16 cases.

The effect and stability of MVCT images on adaptive TomoTherapy.

Use of helical TomoTherapy-based MVCT imaging for adaptive planning is becoming increasingly popular. Treatment planning and dose calculations based on MVCT require an image value to electron density calibration to remain stable over the course of treatment time. In this work, we have studied the dosimetric impact on TomoTherapy treatment plans due to variation in image value to density table (IVDT) curve as a function of target degradation.

The American Society for Radiation Oncology's 2010 core physics curriculum for radiation oncology residents.

Purpose: In 2004, the American Society for Radiation Oncology (ASTRO) published its first physics education curriculum for residents, which was updated in 2007. A committee composed of physicists and physicians from various residency program teaching institutions was reconvened again to update the curriculum in 2009.

Methods And Materials: Members of this committee have associations with ASTRO, the American Association of Physicists in Medicine, the Association of Residents in Radiation Oncology, the American Board of Radiology (ABR), and the American College of Radiology.

Treatment planning for pulsed reduced dose-rate radiotherapy in helical tomotherapy.

Purpose: Pulsed reduced dose-rate radiotherapy (PRDR) is a valuable method of reirradiation because of its potential to reduce late normal tissue toxicity while still yielding significant tumoricidal effect. A typical method using a conventional linear accelerator (linac) is to deliver a series of 20-cGy pulses separated by 3-min intervals to give an effective dose-rate of just under 7 cGy/min. Such a strategy is fraught with difficulties when attempted on a helical tomotherapy unit.

Variability of textural features in FDG PET images due to different acquisition modes and reconstruction parameters.

Background: Characterization of textural features (spatial distributions of image intensity levels) has been considered as a tool for automatic tumor segmentation. The purpose of this work is to study the variability of the textural features in PET images due to different acquisition modes and reconstruction parameters.

Material And Methods: Twenty patients with solid tumors underwent PET/CT scans on a GE Discovery VCT scanner, 45-60 minutes post-injection of 10 mCi of [(18)F]FDG.

Advances in radiation therapy dosimetry.

During the last decade, there has been an explosion of new radiation therapy planning and delivery tools. We went through a rapid transition from conventional three-dimensional (3D) conformal radiation therapy to intensity-modulated radiation therapy (IMRT) treatments, and additional new techniques for motion-adaptive radiation therapy are being introduced. These advances push the frontiers in our effort to provide better patient care; and with the addition of IMRT, temporal dimensions are major challenges for the radiotherapy patient dosimetry and delivery verification.