Regional disparities in IMRT utilization in Japan: analysis of trends and associated medical resources from 2015 to 2019†.

Intensity-modulated radiation therapy (IMRT) uses intensity-modulated photon beams from multiple directions to achieve conformal dose delivery to a target with a complex shape while reducing the dose to organs at risk. We analyzed the trends in IMRT utilization rates across Japanese prefectures from 2015 to 2019 and investigated their relationship with medical resources. Data from the National Database of Health Insurance Claims and the Japanese Society for Radiation Oncology Structure Survey were analyzed.

Independent verification system for intracavitary brachytherapy based on a reference plan and statistical model.

High dose rate (HDR) intracavitary brachytherapy (ICBT) with a remote afterloading system plays a vital role in the treatment of cervical cancer. We aimed to develop a new verification system for ICBT for cervical cancer and evaluate the feasibility for clinical plans (PlanClin) generated for different remote afterloaders, applicators and treatment techniques. In total, 517 PlansClin of patients were treated with Elekta 192Ir microSelectron HDR v2r.

Assessing the robustness of dose distributions in carbon ion prostate radiotherapy using a fast dose evaluation system.

Purpose: We developed a software program for swiftly calculating dose distributions for carbon ion beams. This study aims to evaluate the accuracy of dose calculations using this software and assess the robustness of dose distribution in treating prostate cancer.

Methods: At the Osaka Heavy Ion Therapy Center, markers are inserted into the prostate gland and used for position verification.

Optimization of Fluence Map for CyberKnife Raster Scanning Intensity Modulated Radiotherapy.

Background/aim: Stereotactic body radiotherapy for prostate cancer using CyberKnife with circular cone requires a long treatment time. Raster scanning intensity modulated radiotherapy (RS-IMRT) has a potential of improving treatment efficacy, introducing shorter treatment time, better target dose uniformity, and lower organ at risk (OAR) dose. The purpose of the study was to develop a fluence optimization system for RS-IMRT.

Evaluation of Lung and Liver Tumor Dose Coverage Treated With the CyberKnife Synchrony System With Consideration of Measured Tracking Errors.

Background/aim: Lung and liver tumor dose coverage was evaluated for the CyberKnife synchrony respiratory tracking system (SRTS) with consideration of the motion tracking accuracy measured for motion patterns of individual patients.

Patients And Methods: Seven treatment plans of six cases treated with the SRTS were evaluated. The motion phantom was moved with the motion data derived from the treatment log files.

Dosimetric Evaluation of CyberKnife Synchrony System for Liver Tumors With Respiratory Phase Shifts.

Background/aim: This study evaluated the effects of the respiratory phase shifts between liver tumor and chest wall motions on the dose distribution for the CyberKnife Synchrony respiratory tracking system (SRTS).

Patients And Methods: Eight patients who received stereotactic body radiotherapy for hepatocellular carcinoma or liver metastases were analyzed. Three-dimensional (3D) motion of the implanted fiducial markers and vertical motion of the sternal bone were derived from the four-dimensional computed tomography (4D-CT) images acquired with a 320-row area detector CT.

Long-term Outcomes of Radiation Therapy for Prostate Cancer in Elderly Patients Aged ≥75 Years.

Background/aim: This study aimed to evaluate the treatment outcomes of radiation therapy (RT) for localized prostate cancer in elderly patients aged ≥75 years.

Patients And Methods: We retrospectively investigated data of patients aged ≥75 years with prostate cancer who underwent intensity-modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT) with doses of 70-78 Gy in 35-39 fractions between September 2008 and June 2016. Overall survival (OS), recurrence-free (RF) rates, and occurrence rates of toxicities were calculated.

Poly (ADP-ribose) polymerase inhibitors sensitize cancer cells to hypofractionated radiotherapy through altered selection of DNA double-strand break repair pathways.

Purpose: Poly (ADP-ribose) polymerase inhibitors (PARPi) are known to induce radiosensitization. However, the exact mechanisms of radiosensitization remain unclear. We previously reported that PARPi may have a unique radiosensitizing effect to enhance β-components of the linear-quadratic model.

Characteristics of microSilicon diode detector for electron beam dosimetry.

A microSilicon™ (PTW type 60023), a new unshielded diode detector succeeding Diode E (model 60017, PTW), was characterized for electron beam dosimetry and compared with other detectors. Electron beams generated from a TrueBeam linear accelerator were measured using the microSilicon, Diode E, and microDiamond synthetic single-crystal diamond detector. Positional accuracy of microSilicon was measured by data collected in air and water.

Improvement of image quality for pancreatic cancer using deep learning-generated virtual monochromatic images: Comparison with single-energy computed tomography.

Purpose: To construct a deep convolutional neural network that generates virtual monochromatic images (VMIs) from single-energy computed tomography (SECT) images for improved pancreatic cancer imaging quality.

Materials And Methods: Fifty patients with pancreatic cancer underwent a dual-energy CT simulation and VMIs at 77 and 60 keV were reconstructed. A 2D deep densely connected convolutional neural network was modeled to learn the relationship between the VMIs at 77 (input) and 60 keV (ground-truth).

Correction of lateral response artifacts from flatbed scanners for dual-channel radiochromic film dosimetry.

In this study, we evaluated the inter-unit variability of the lateral response artifact for multiple flatbed scanners, focusing on the dual-channel method, and investigated the correction method of the lateral non-uniformity. Four scanners with A3+ paper-size and five scanners with A4 paper-size were evaluated. To generate the dose-response curves, small pieces of the Gafchromic EBT3 and EBT-XD films were irradiated, and five of the pieces were repeatedly scanned by moving them on the scanner to evaluate the lateral non-uniformity.

Development of raster scanning IMRT using a robotic radiosurgery system.

Treatment time with the CyberKnife frameless radiosurgery system is prolonged due to the motion of the robotic arm. We have developed a novel scanning irradiation method to reduce treatment time. We generated treatment plans mimicking eight-field intensity-modulated radiotherapy (IMRT) plans generated for the Novalis radiosurgery system.

Technical Note: Characteristics of a microSilicon X shielded diode detector for photon beam dosimetry.

Purpose: This study investigated the characteristics of a new shielded diode detector, microSilicon X (model 60022: MSX), for small-field and large-field dosimetry.

Methods: The percent depth dose (PDD), beam profiles, detector output factor (OF ), temperature dependence, dose rate dependence, dose-per-pulse (DPP) dependence, and dose-response linearity of MSX were evaluated in Cyberknife and TrueBeam photon beams and compared with various detectors including microDiamond (PTW model 60019: MD), Sun Nuclear EDGE detector, Photon diode (PTW model 60016: PD), and semiflex ionization chamber (PTW model 31010: IC).

Results: For field sizes ranging from 50 × 50 mm to 400 × 400 mm , MSX-measured OF values were within 1% of the IC-measured values.

Repositioning accuracy of a novel thermoplastic mask for head and neck cancer radiotherapy.

Purpose: The aim of this study was to assess the reproducibility of patient shoulder position immobilized with a novel and innovative prototype mask (E-Frame, Engineering System).

Methods: The E-frame mask fixes both shoulders and bisaxillary regions compared with that of a commercial mask (Type-S, CIVCO). Thirteen and twelve patients were immobilized with the Type-S and E-Frame mask systems, respectively.

Characterization of a microSilicon diode detector for small-field photon beam dosimetry.

This study characterized a new unshielded diode detector, the microSilicon (model 60023), for small-field photon beam dosimetry by evaluating the photon beams generated by a TrueBeam STx and a CyberKnife. Temperature dependence was evaluated by irradiating photons and increasing the water temperature from 11.5 to 31.

Assessment of Daily Replanning and Geometrical Variation of High-dose-rate Brachytherapy for the Prostate.

Background: The present study aimed to estimate geometric changes in applicators and prostate over 3 days in patients with high-dose-rate brachytherapy (HDR-BT) and to assess the need for daily replanning.

Patients And Methods: This study retrospectively investigated 18 patients who underwent HDR-BT as monotherapy from February 2016 to October 2018.

Results: Without replanning, the planning target volume coverage significantly worsened on day 2 (p<0.

Impact of patient positioning uncertainty in noncoplanar intracranial stereotactic radiotherapy.

The aim of this study is to evaluate the patient positioning uncertainty in noncoplanar stereotactic radiosurgery or stereotactic radiotherapy (SRS/SRT) for intracranial lesions with the frameless 6D ExacTrac system. In all, 28 patients treated with SRS/SRT of 70 treatment plans at our institution were evaluated in this study. Two X-ray images with the frameless 6D ExacTrac system were first acquired to correct (XC) and verify (XV) the patient position at a couch angle of 0º.