Respiratory-gated proton beam therapy for intrahepatic cholangiocarcinoma without fiducial markers.

Background: Intrahepatic cholangiocarcinoma (ICC) is a challenging primary liver cancer with a poor prognosis, especially in unresectable cases. Traditional palliative irradiation is limited in reducing liver doses. This study aimed to evaluate the efficacy and toxicity of respiratory-gated proton beam therapy without fiducial markers for intrahepatic cholangiocarcinoma.

Dose Evaluation in 2-Phase Method for Advanced Esophageal Cancer by Hybrid Irradiation Techniques.

Purpose: In concurrent chemoradiotherapy for advanced esophageal cancer, a 2-phase method consisting of initial irradiation of a wide elective nodal region and boost irradiation of the primary lesion is commonly employed. Although dose escalation to the primary lesion may be required to achieve higher local control rates, the radiation dose to critical organs must not exceed dose constraints. To achieve an optimum balance of dose prescription and dose reduction to surrounding organs, such as the lungs and heart, we compared hybrid dose distributions and investigated the best combination of the following recent irradiation techniques: volumetric modulation arc therapy (VMAT), proton broad-beam irradiation, and intensity-modulated proton beam therapy (IMPT).

[Estimation of Uncertainty of the VMAT Absolute Dose Measurement Due to the Phantom Setup Error Using a Treatment Planning System].

Purpose: When performing single-point dose verification in VMAT, it is necessary to avoid the regions with steep dose gradient. We propose a method to obtain the estimated value ( U) of uncertainty of the absolute dose measurement due to the phantom setup error by using dose gradient calculated from treatment planning system (TPS), for evaluating the appropriate measurement points.

Methods: The dose gradient was calculated from the planned dose values in the vicinity of the isocenter point using TPS.

Evaluation of Exposure Doses of Elective Nodal Irradiation in Chemoradiotherapy for Advanced Esophageal Cancer.

We evaluated elective nodal irradiation (ENI) doses during radical chemoradiotherapy (CRT) for esophageal cancer (EC). A total of 79 patients (65 men and 14 women) aged 52-80 years with T1-3, N0-3, and M0 (including M1ly) who underwent CRT for EC during November 2012-September 2019 were eligible for this retrospective analysis. Patients were divided into two groups: the high-dose group (HG), including 38 patients who received ≥40 Gy as ENI; and the low-dose group (LG), including 41 patients who received <40 Gy.

Long-Term Results of Proton Therapy for Hepatocellular Carcinoma Using Four-Dimensional Computed Tomography Planning without Fiducial Markers.

We report here the long-term results of marker-less respiratory-gated proton therapy (PT), without fiducial markers for hepatocellular carcinoma (HCC), which was planned using a four-dimensional computed tomography technique. Local tumor control (LTC) and overall survival (OS) were estimated using the Kaplan-Meier method. Toxicity was graded per CTCAE v5.

A robust optimization method for weighted-layer-stacking proton beam therapy.

The layer-stacking method can provide three-dimensional conformal dose distributions to the target based on a passive scattering method using mini-spread-out Bragg peak (SOBP). The purpose of this work is to demonstrate the effectiveness of a new weight optimization algorithm that can enhance the robustness of dose distributions against layer depth variation in layer-stacking proton beam therapy. In the robustness algorithm, the upper limit of the layer's weight was adapted to the conventional algorithm and varied for 620 weight set evaluations.

Erratum: Shibata S.; et al. Proton Beam Therapy without Fiducial Markers Using Four-Dimensional CT Planning for Large Hepatocellular Carcinomas. Cancers 2018, 10, 71.

The authors wish to make the following corrections to this paper [...

Effects of organ motion on proton prostate treatments, as determined from analysis of daily CT imaging for patient positioning.

Purpose: We quantified interfractional movements of the prostate, seminal vesicles (SVs), and rectum during computed tomography (CT) image-guided proton therapy for prostate cancer and studied the range variation in opposed lateral proton beams.

Materials/methods: We analyzed 375 sets of daily CT images acquired throughout the proton therapy treatment of ten patients. We analyzed daily movements of the prostate, SVs, and rectum by simulating three image-matching strategies: bone matching, prostate center (PC) matching, and prostate-rectum boundary (PRB) matching.

Proton Beam Therapy without Fiducial Markers Using Four-Dimensional CT Planning for Large Hepatocellular Carcinomas.

We evaluated the effectiveness and toxicity of proton beam therapy (PBT) for hepatocellular carcinomas (HCC) >5 cm without fiducial markers using four-dimensional CT (4D-CT) planning. The subjects were 29 patients treated at our hospital between March 2011 and March 2015. The median total dose was 76 Cobalt Gray Equivalents (CGE) in 20 fractions (range; 66-80.

Positioning accuracy and daily dose assessment for prostate cancer treatment using in-room CT image guidance at a proton therapy facility.

Purpose: To evaluate the effectiveness of CT image-guided proton radiotherapy for prostate cancer by analyzing the positioning uncertainty and assessing daily dose change due to anatomical variations.

Materials And Methods: Patients with prostate cancer were treated by opposed lateral proton beams based on a passive scattering method using an in-room CT image-guided system. The system employs a single couch for both CT scanning and beam delivery.

Respiratory-gated Proton Beam Therapy for Hepatocellular Carcinoma Adjacent to the Gastrointestinal Tract without Fiducial Markers.

The efficacy of proton beam therapy (PBT) for hepatocellular carcinoma (HCC) has been reported, but insertion of fiducial markers in the liver is usually required. We evaluated the efficacy and toxicity of respiratory-gated PBT without fiducial markers for HCC located within 2 cm of the gastrointestinal tract. From March 2011 to December 2015 at our institution, 40 patients were evaluated (median age, 72 years; range, 38-87 years).

Development of the breast immobilization system in prone setup: The effect of bra in prone position to improve the breast setup error.

Purpose/objective(s): Accurate and reproducible positioning of the breast is difficult due to its deformability and softness; thus, targeting a breast tumor or tumor bed with fractionated radiotherapy using external beam radiation is difficult. The aim of this study was to develop a novel bra to aid in breast immobilization in the prone position.

Materials & Methods: To assess the accuracy of prone position fixation of breast tumors, 33 breast cancer patients with 34 lesions were recruited.

Evaluation of Focal Liver Reaction after Proton Beam Therapy for Hepatocellular Carcinoma Examined Using Gd-EOB-DTPA Enhanced Hepatic Magnetic Resonance Imaging.

Background: Proton beam therapy (PBT) achieves good local control for hepatocellular carcinoma (HCC), and toxicity tends to be lower than for photon radiotherapy. Focal liver parenchymal damage in radiotherapy is described as the focal liver reaction (FLR); the threshold doses (TDs) for FLR in the background liver have been analyzed in stereotactic ablative body radiotherapy and brachytherapy. To develop a safer approach for PBT, both TD and liver volume changes are considered clinically important in predicting the extent of damage before treatment, and subsequently in reducing background liver damage.

Semi-analytical model for output factor calculations in proton beam therapy with consideration for the collimator aperture edge.

In the development of an external radiotherapy treatment planning system, the output factor (OPF) is an important value for the monitor unit calculations. We developed a proton OPF calculation model with consideration for the collimator aperture edge to account for the dependence of the OPF on the collimator aperture and distance in proton beam therapy. Five parameters in the model were obtained by fitting with OPFs measured by a pinpoint chamber with the circular radiation fields of various field radii and collimator distances.

A model-based analysis of a simplified beam-specific dose output in proton therapy with a single-ring wobbling system.

In radiation therapy, it is necessary to preset a monitor unit in an irradiation control system to deliver a prescribed absolute dose to a reference point in the planning target volume. The purpose of this study was to develop a model-based monitor unit calculation method for proton-beam therapy with a single-ring wobbling system. The absorbed dose at a calibration point per monitor unit had been measured for each beam-specific measurement condition without a patient-specific collimator or range compensator before proton therapeutic irradiation at Shizuoka Cancer Center.

The usefulness of vinyl polysiloxane dental impression material as a proton beam stopper to save normal tissue during irradiation of the oral cavity: basic and clinical verifications.

Purpose: To evaluate the feasibility and usefulness of vinyl polysiloxane (VPS) dental impression material as a proton beam stopper for oral cavity irradiation.

Methods: VPS compounds with different base-catalyst mixture ratios were created, and the relative linear stopping power (RLSP) of each VPS compound was measured to compare with the RLSPs obtained from converted CT data. Then, a model plan was created to simulate oral cancer, and depth-dose distributions that were calculated using radiation treatment planning (RTP) were investigated by comparing the distribution with the measurements.

Preliminary calculation of RBE-weighted dose distribution for cerebral radionecrosis in carbon-ion treatment planning.

Cerebral radionecrosis is a significant side effect in radiotherapy for brain cancer. The purpose of this study is to calculate the relative biological effectiveness (RBE) of carbon-ion beams on brain cells and to show RBE-weighted dose distributions for cerebral radionecrosis speculation in a carbon-ion treatment planning system. The RBE value of the radionecrosis for the carbon-ion beam is calculated by the modified microdosimetric kinetic model on the assumption of a typical clinical α/β ratio of 2 Gy for cerebral radionecrosis in X-rays.

Microdosimetric approach to NIRS-defined biological dose measurement for carbon-ion treatment beam.

The RBE-weighted absorbed dose, called "biological dose," has been routinely used for carbon-ion treatment planning in Japan to formulate dose prescriptions for treatment protocols. This paper presents a microdosimetric approach to measuring the biological dose, which was redefined to be derived from microdosimetric quantities measured by a tissue-equivalent proportional counter (TEPC). The TEPC was calibrated in (60)Co gamma rays to assure a traceability of the TEPC measurement to Japanese standards and to eliminate the discrepancies among matching counters.