Verification of surface-guided radiation therapy (SGRT) alignment for proton breast and chest wall patients by comparison to CT-on-rails and kV-2D alignment.

Background: Surface-guided radiation therapy (SGRT) systems have been widely installed and utilized on linear accelerators. However, the use of SGRT with proton therapy is still a newly developing field, and published reports are currently very limited.

Purpose: To assess the clinical application and alignment agreement of SGRT with CT-on-rails (CTOR) and kV-2D image-guided radiation therapy (IGRT) for breast treatment using proton therapy.

Measurements of fetal dose with Mevion S250i proton therapy system with HYPERSCAN.

Purpose: To characterize potential dose to the fetus for all modes of delivery (dynamic adaptive aperture, static adaptive aperture, and no adaptive aperture) for the Mevion S250i Proton Therapy System with HYPERSCAN and compare the findings with those of other available proton systems.

Materials And Methods: Fetal dose measurements were performed for all three modes of dose delivery on the Mevion S250i Proton therapy system with HYPERSCAN (static aperture, dynamic aperture and uncollimated). Standard treatment plans were created in RayStation for a left-sided brain lesion treated with a vertex field, a left lateral field, and a posterior field.

An evaluation of the use of DirectSPR images for proton planning in the RayStation treatment planning software.

An important source of uncertainty in proton therapy treatment planning is the assignment of stopping-power ratio (SPR) from CT data. A commercial product is now available that creates an SPR map directly from dual-energy CT (DECT). This paper investigates the use of this new product in proton treatment planning and compares the results to the current method of assigning SPR based on a single-energy CT (SECT).

A novel approach for Venezia ovoid commissioning with a comprehensive analysis of source positions in high-dose-rate brachytherapy.

Purpose: The lunar design of a Venezia ovoid makes commissioning of the applicator very challenging with traditional autoradiography. In this study, we propose a novel solution to ovoid commissioning and a quality assurance (QA) workflow to effectively assess the entire source path.

Methods And Materials: A two-step commissioning process, using electron radiation and radiochromic films, was developed to verify the most distal source position.

Surface-Guided Patient Setup Versus Traditional Tattoo Markers for Radiation Therapy: Is Tattoo-Less Setup Feasible for Thorax, Abdomen and Pelvis Treatment?

Purpose: In this study, patient setup accuracy was compared between surface guidance and tattoo markers for radiation therapy treatment sites of the thorax, abdomen and pelvis.

Methods And Materials: A total of 608 setups performed on 59 patients using both surface-guided and tattoo-based patient setups were analyzed. During treatment setup, patients were aligned to room lasers using their tattoos, and then the six-degree-of-freedom (6DOF) surface-guided offsets were calculated and recorded using AlignRT system.

Impact of detector selection on commissioning of Leipzig surface applicators with improving immobilization in high-dose-rate brachytherapy.

Purpose: Commission and treatment setup of Leipzig surface applicators, because of the steep dose gradient and lack of robust immobilization, is challenging. We aim to improve commissioning reliability by investigating the impact of detector choice on percentage depth dose (PDD) verifications, and to enhance accuracy and reproducibility in calibration/treatment setup through a simple and novel immobilization device.

Methods And Materials: PDD distributions were measured with radiochromic films, optically stimulated luminescent dosimeters (OSLDs), a diode detector, and both cylindrical and parallel plate ionization chambers.

Evaluation of the effects of implementing a diode transmission device into the clinical workflow.

Purpose: This work investigated effects of implementing the Delta Discover diode transmission detector into the clinical workflow.

Methods: PDD and profile scans were completed with and without the Discover for a number of photon beam energies. Transmission factors were determined for all beam energies and included in Eclipse TPS to account for the attenuation of the Discover.

Using failure mode and effects analysis (FMEA) to generate an initial plan check checklist for improved safety in radiation treatment.

Purpose: To apply failure mode and effect analysis (FMEA) to generate an effective and efficient initial physics plan checklist.

Methods: A team of physicists, dosimetrists, and therapists was setup to reconstruct the workflow processes involved in the generation of a treatment plan beginning from simulation. The team then identified possible failure modes in each of the processes.

FMEA-guided transition from microSelectron to Flexitron for HDR brachytherapy.

Purpose: To utilize failure mode and effects analysis (FMEA) to effectively direct the transition from the Elekta microSelectron to the Flexitron high dose-rate afterloader system.

Materials And Methods: Our FMEA was performed in two stages. In the first stage, the lead brachytherapy physicists used FMEA to guide the brainstorming sessions and to identify vulnerabilities during this transition.

Technical Note: The use of DirectDensity and dual-energy CT in the radiation oncology clinic.

Purpose: Two new tools available in Radiation Oncology clinics are Dual-energy CT (DECT) and Siemens' DirectDensity™ (DD) reconstruction algorithm, which allows scans of any kV setting to use the same calibration. This study demonstrates why DD scans should not be used in combination with DECT and quantifies the magnitude of potential errors in image quality and dose.

Methods: A CatPhan 504 phantom was scanned with a dual-pass DECT and reconstructed with many different kernels, including several DD kernels.

Daily breathing inconsistency in pancreas SBRT: a 4DCT study.

Background: Stereotactic body radiation therapy (SBRT) treatments of pancreatic cancer typically employ relatively small margins. This study characterizes the motion of high visibility structures in close proximity to the pancreas to determine how much the motion envelope of such a structure changes due to respiratory variation between fractions.

Methods: Fanbeam, four-dimensional computed tomography (4DCT) studies acquired initially for planning and again prior to each treatment for 6 patients were used to fully characterize the change in motion of high-contrast structures in close proximity to the pancreas.

An evaluation of the consistency of shifts reported by three different systems for non-coplanar treatments.

Treatment of intra-cranial lesions sometimes requires a non-coplanar beam configuration. One of the most commonly used IGRT modalities, kV conebeam CT, cannot typically be used when large couch rotations are introduced. However, multiple other systems allow for imaging/tracking the patient for such situations.

Skin dose estimation using virtual structures for Contura Multi-Lumen Balloon breast brachytherapy.

Purpose: To propose a workflow that uses ultrasound (US)-measured skin-balloon distances and virtual structure creations in the treatment planning system to evaluate the maximum skin dose for patients treated with Contura Multi-Lumen Balloon applicators.

Methods And Materials: Twenty-three patients were analyzed in this study. CT and US were used to investigate the interfractional skin-balloon distance variations.

A graphic user interface toolkit for specification, report and comparison of dose-response relations and treatment plans using the biologically effective uniform dose.

A toolkit (BEUDcal) has been developed for evaluating the effectiveness and for predicting the outcome of treatment plans by calculating the biologically effective uniform dose (BEUD) and complication-free tumor control probability. The input for the BEUDcal is the differential dose-volume histograms of organs exported from the treatment planning system. A clinical database is built for the dose-response parameters of different tumors and normal tissues.

Evaluation on lung cancer patients' adaptive planning of TomoTherapy utilising radiobiological measures and Planned Adaptive module.

Adaptive radiation therapy is a promising concept that allows individualised, dynamic treatment planning based on feedback of measurements. The TomoTherapy Planned Adaptive application, integrated to the helical TomoTherapy planning system, enables calculation of actual dose delivered to the patient for each treatment fraction according to the pretreatment megavoltage computed tomography (MVCT) scan and image registration. As a result, new fractionation treatment plans are available if correction is necessary.

Dosimetric impacts of gantry angle misalignment on prostate cancer treatment using helical tomotherapy.

During helical tomotherapy, gantry angle accuracy is one of the vital geometric factors that assure accurate dose delivery to the target and organs at risk adjacent to it. The purpose of this study is to investigate the dosimetric impact of gantry angle misalignment on the target volume and critical organs during helical tomotherapy treatment. Five prostate cases were chosen to calculate the effects of gantry angle deviations on both patient-specific delivery quality assurance (DQA) and helical tomotherapy treatment plans.

Clinical application of GAFCHROMIC EBT film for in vivo dose measurements of total body irradiation radiotherapy.

The GAFCHROMIC EBT film model is a fairly new film product designed for absorbed dose measurements of high-energy photon beams. In vivo dosimetry for total body irradiation (TBI) remains a challenging task due to the extended source-to-surface distance (SSD), low dose rates, and the use of beam spoilers. EBT film samples were used for dose measurements on an anthropomorphic phantom using a TBI setup.

Dosimetry characteristics of GAFCHROMIC EBT film responding to therapeutic electron beams.

For the last 50 years, high-energy electron beams have been used mainly for treatment of superficial targets. Accordingly, two-dimensional (2D) measurements are required to determine the margin between the surface and protected normal tissues in high-dose-gradient regions. As recommended by the AAPM, 2D electron beam dosimetry should be conducted primarily with films because of their high spatial resolution and because of the fact that they produce permanent records.

Disparity of activation onset in sensory cortex from simultaneous auditory and visual stimulation: Differences between perfusion and blood oxygenation level-dependent functional magnetic resonance imaging.

Purpose: To compare the temporal behaviors of perfusion and blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) in the detection of timing differences between distinct brain areas, and determine potential latency differences between stimulus onset and measurable fMRI signal in sensory cortices.

Materials And Methods: Inversion recovery (IR) spin-echo echo-planar imaging (EPI) and T2*-weighted gradient-echo EPI sequences were used for perfusion- and BOLD-weighted experiments, respectively. Simultaneous auditory and visual stimulations were employed in an event-related (ER) paradigm.

Temporal resolving power of perfusion- and BOLD-based event-related functional MRI.

Functional magnetic resonance imaging (fMRI) based on both perfusion and blood oxygenation level-dependent (BOLD) contrasts has been widely applied in spatiotemporal mapping of the human brain function. Temporal resolving power of fMRI is limited by the smoothed hemodynamic response function dispersed from the neuronal activity. In this study, temporal modulation transfer functions were utilized to quantify the resolving powers of perfusion and BOLD fMR signals in time domain.