Feasibility of Synchrotron-Based Ultra-High Dose Rate (UHDR) Proton Irradiation with Pencil Beam Scanning for FLASH Research.

Background: This study aims to present the feasibility of developing a synchrotron-based proton ultra-high dose rate (UHDR) pencil beam scanning (PBS) system.

Methods: The RF extraction power in the synchrotron system was increased to generate 142.4 MeV pulsed proton beams for UHDR irradiation at ~100 nA beam current.

Dual-Energy Computed Tomography Proton-Dose Calculation with Scripting and Modified Hounsfield Units.

Purpose: To describe an implementation of dual-energy computed tomography (DECT) for calculation of proton stopping-power ratios (SPRs) in a commercial treatment-planning system. The process for validation and the workflow for safe deployment of DECT is described, using single-energy computed tomography (SECT) as a safety check for DECT dose calculation.

Materials And Methods: The DECT images were acquired at 80 kVp and 140 kVp and were processed with computed tomography scanner software to derive the electron density and effective atomic number images.

Current delivery limitations of proton PBS for FLASH.

Purpose: Proton Pencil Beam Scanning (PBS) is an attractive solution to realize the advantageous normal tissue sparing elucidated from FLASH high dose rates. The mechanics of PBS spot delivery will impose limitations on the effective field dose rate for PBS.

Methods: This study incorporates measurements from clinical and FLASH research beams on uniform single energy and the spread-out Bragg Peak PBS fields to extrapolate the PBS dose rate to high cyclotron beam currents 350, 500, and 800 nA.

Prompt gamma imaging for the identification of regional proton range deviations due to anatomic change in a heterogeneous region.

Objectives: Prompt gamma (PG) imaging has previously been demonstrated for use in proton range verification of a brain treatment with a homogeneous target region. In this study, the feasibility of PG imaging to detect anatomic change within a heterogeneous region is presented.

Methods: A prompt gamma camera recorded several fractions of a patient treatment to the base of skull.

Dose to Highly Functional Ventilation Zones Improves Prediction of Radiation Pneumonitis for Proton and Photon Lung Cancer Radiation Therapy.

Purpose: We hypothesized that the radiation dose in high-ventilation portions of the lung better predicts radiation pneumonitis (RP) outcome for patients treated with proton radiation therapy (PR) and photon radiation therapy (PH).

Methods And Materials: Seventy-four patients (38 protons, 36 photons) with locally advanced non-small cell lung cancer treated with concurrent chemoradiation therapy were identified, of whom 24 exhibited RP (graded using Common Terminology Criteria for Adverse Events v4.0) after PR or PH, and 50 were negative controls.

Influence of intravenous contrast agent on dose calculation in proton therapy using dual energy CT.

The purpose of this study is to evaluate the effect of an intravenous (IV) contrast agent on proton therapy dose calculation using dual-energy computed tomography (DECT). Two DECT methods are considered. The first one, [Formula: see text], attempts to accurately predict the proton stopping powers relative to water (SPR) of contrast enhanced (CE) DECT images, while the second generates a virtual non-contrast (VNC) volume that can be processed as a native non-contrast (NC) one.

Stereotactic body proton therapy for liver tumors: Dosimetric advantages and their radiobiological and clinical implications.

Background And Purpose: Photon Stereotactic Body Radiotherapy (SBRT) for primary and metastatic tumors of the liver is challenging for larger lesions. An comparison of paired SBRT and Stereotactic Body Proton Therapy (SBPT) plans was performed to understand the potential advantages of SBPT as a function of tumor size and location.

Methods And Materials: Theoretical tumor volumes with maximum diameter of 1-10 cm were contoured in the dome, right inferior, left medial, and central locations.

Automated Knowledge-Based Intensity-Modulated Proton Planning: An International Multicenter Benchmarking Study.

Radiotherapy treatment planning is increasingly automated and knowledge-based planning has been shown to match and sometimes improve upon manual clinical plans, with increased consistency and efficiency. In this study, we benchmarked a novel prototype knowledge-based intensity-modulated proton therapy (IMPT) planning solution, against three international proton centers. A model library was constructed, comprising 50 head and neck cancer (HNC) manual IMPT plans from a single center.

Efficient double-scattering proton therapy with a patient-specific bolus.

Purpose: Passive scattering proton radiotherapy utilizes beam-specific compensators to shape the dose to the distal end of the tumor target. These compensators typically require therapists to enter the treatment room to mount between beams. This study investigates a novel approach that utilizes a single patient-specific bolus to accomplish the role of multi-field compensators to improve the efficiency of the treatment delivery.

Ex vivo validation of a stoichiometric dual energy CT proton stopping power ratio calibration.

A major source of uncertainty in proton therapy is the conversion of Hounsfield unit (HU) to proton stopping power ratio relative to water (SPR). In this study, we measured and quantified the accuracy of a stoichiometric dual energy CT (DECT) SPR calibration. We applied a stoichiometric DECT calibration method to derive the SPR using CT images acquired sequentially at [Formula: see text] and [Formula: see text].

Prompt Gamma Imaging for In Vivo Range Verification of Pencil Beam Scanning Proton Therapy.

Purpose: To report the first clinical results and value assessment of prompt gamma imaging for in vivo proton range verification in pencil beam scanning mode.

Methods And Materials: A stand-alone, trolley-mounted, prototype prompt gamma camera utilizing a knife-edge slit collimator design was used to record the prompt gamma signal emitted along the proton tracks during delivery of proton therapy for a brain cancer patient. The recorded prompt gamma depth detection profiles of individual pencil beam spots were compared with the expected profiles simulated from the treatment plan.

Quantification of vaginal motion associated with daily endorectal balloon placement during whole pelvis radiotherapy for gynecologic cancers.

Background And Purpose: To quantify intra-treatment vaginal motion in women treated with daily endorectal balloon (ERB) placement and external beam radiotherapy for gynecologic cancers.

Materials And Methods: Eighteen post-hysterectomy women with gynecologic cancers underwent computed tomography (CT) simulation scans and daily treatment with ERB. Fiducial markers were placed at the vaginal apex prior to simulation and patients were counseled on a pre-treatment bladder filling protocol.

Prospective MRI-based imaging study to assess feasibility of proton therapy for post-prostatectomy radiation.

Purpose/objectives: To optimize delivery of post-prostatectomy radiation (PPRT) with protons by examining dosimetric effects of variations in physician contouring, organ motion, and patient alignment during a course of PPRT.

Material And Methods: We enrolled 10 patients receiving PPRT in a prospective imaging study. All patients underwent combined computed tomography (CT)/magnetic resonance imaging (MRI) simulation with endorectal balloon (ERB) and received intensity modulated radiation therapy (IMRT) per institutional standards.

First Clinical Investigation of Cone Beam Computed Tomography and Deformable Registration for Adaptive Proton Therapy for Lung Cancer.

Purpose: An adaptive proton therapy workflow using cone beam computed tomography (CBCT) is proposed. It consists of an online evaluation of a fast range-corrected dose distribution based on a virtual CT (vCT) scan. This can be followed by more accurate offline dose recalculation on the vCT scan, which can trigger a rescan CT (rCT) for replanning.

Quantitative assessment of anatomical change using a virtual proton depth radiograph for adaptive head and neck proton therapy.

The aim of this work is to demonstrate the feasibility of using water-equivalent thickness (WET) and virtual proton depth radiographs (PDRs) of intensity corrected cone-beam computed tomography (CBCT) to detect anatomical change and patient setup error to trigger adaptive head and neck proton therapy. The planning CT (pCT) and linear accelerator (linac) equipped CBCTs acquired weekly during treatment of a head and neck patient were used in this study. Deformable image registration (DIR) was used to register each CBCT with the pCT and map Hounsfield units (HUs) from the planning CT (pCT) onto the daily CBCT.

Potential of 3D printing technologies for fabrication of electron bolus and proton compensators.

In electron and proton radiotherapy, applications of patient-specific electron bolus or proton compensators during radiation treatments are often necessary to accommodate patient body surface irregularities, tissue inhomogeneity, and variations in PTV depths to achieve desired dose distributions. Emerging 3D printing technologies provide alternative fabrication methods for these bolus and compensators. This study investigated the potential of utilizing 3D printing technologies for the fabrication of the electron bolus and proton compensators.

Comparative assessment of liver tumor motion using cine-magnetic resonance imaging versus 4-dimensional computed tomography.

Purpose: To compare the extent of tumor motion between 4-dimensional CT (4DCT) and cine-MRI in patients with hepatic tumors treated with radiation therapy.

Methods And Materials: Patients with liver tumors who underwent 4DCT and 2-dimensional biplanar cine-MRI scans during simulation were retrospectively reviewed to determine the extent of target motion in the superior-inferior, anterior-posterior, and lateral directions. Cine-MRI was performed over 5 minutes.

Dynamic simulation of motion effects in IMAT lung SBRT.

Background: Intensity modulated arc therapy (IMAT) has been widely adopted for Stereotactic Body Radiotherapy (SBRT) for lung cancer. While treatment dose is optimized and calculated on a static Computed Tomography (CT) image, the effect of the interplay between the target and linac multi-leaf collimator (MLC) motion is not well described and may result in deviations between delivered and planned dose. In this study, we investigated the dosimetric consequences of the inter-play effect on target and organs at risk (OAR) by simulating dynamic dose delivery using dynamic CT datasets.

A comprehensive dosimetric study of pancreatic cancer treatment using three-dimensional conformal radiation therapy (3DCRT), intensity-modulated radiation therapy (IMRT), volumetric-modulated radiation therapy (VMAT), and passive-scattering and modulated-scanning proton therapy (PT).

With traditional photon therapy to treat large postoperative pancreatic target volume, it often leads to poor tolerance of the therapy delivered and may contribute to interrupted treatment course. This study was performed to evaluate the potential advantage of using passive-scattering (PS) and modulated-scanning (MS) proton therapy (PT) to reduce normal tissue exposure in postoperative pancreatic cancer treatment. A total of 11 patients with postoperative pancreatic cancer who had been previously treated with PS PT in University of Pennsylvania Roberts Proton Therapy Center from 2010 to 2013 were identified.

Effects on the photon beam from an electromagnetic array used for patient localization and tumor tracking.

One of the main components in a Calypso 4D localization and tracking system is an electromagnetic array placed above patients that is used for target monitoring during radiation treatment. The beam attenuation and beam spoiling properties of the Calypso electromagnetic array at various beam angles were investigated. Measurements were performed on a Varian Clinac iX linear accelerator with 6 MV and 15 MV photon beams.

Biological consequences of MLC calibration errors in IMRT delivery and QA.

Purpose: The purpose of this work is threefold: (1) to explore biological consequences of the multileaf collimator (MLC) calibration errors in intensity modulated radiotherapy (IMRT) of prostate and head and neck cancers, (2) to determine levels of planning target volume (PTV) and normal tissue under- or overdose flagged with clinically used QA action limits, and (3) to provide biologically based input for MLC QA and IMRT QA action limits.

Methods: Ten consecutive prostate IMRT cases and ten consecutive head and neck IMRT cases were used. Systematic MLC offsets (i.

Incorporating quantitative single photon emission computed tomography into radiation therapy treatment planning for lung cancer: impact of attenuation and scatter correction on the single photon emission computed tomography-weighted mean dose and functional lung segmentation.

Purpose: To assess the impact of attenuation and scatter corrections on the calculation of single photon emission computed tomography (SPECT)-weighted mean dose (SWMD) and functional volume segmentation as applied to radiation therapy treatment planning for lung cancer.

Methods And Materials: Nine patients with lung cancer underwent a SPECT lung perfusion scan. For each scan, four image sets were reconstructed using the ordered subsets expectation maximization method with attenuation and scatter corrections ranging from none to a most comprehensive combination of attenuation corrections and direct scatter modeling.