Publications by authors named "Toshijiro Yamamoto"
[6. Multidisciplinary Team Care and Non-technical Skills].
Nihon Hoshasen Gijutsu Gakkai Zasshi
June 2021
Article Synopsis
- - This study analyzed data from Varian C-series linear accelerators to assess the reliability of average beam data as reference points for verifying radiotherapy treatment planning systems.
- - Researchers collected and averaged data from 20 machines for 4, 6, and 10 MV photon beams, focusing on percent depth dose (PDD), off-center ratio (OCR), and output factor (OPF).
- - Results showed that dose differences from the average were very small (less than 1.0%), indicating that the average data can generally serve as reliable reference data for most field sizes in commissioning processes, except for small field sizes.
Article Synopsis
- * Eleven TrueBeam systems from nine institutions were analyzed, utilizing a VMAT plan created in Eclipse. Various measurements were conducted, including dose metrics from an ionization chamber and film dosimetry.
- * The findings revealed a low mean point dose difference (1.0% ± 0.6%) and high gamma pass rates (over 99% for 3%/2 mm criteria), suggesting reliable agreement between measured and calculated doses. This supports using consistent multi-leaf collimator parameters across institutions to enhance radiation treatment uniformity.
Article Synopsis
- * TG-100 is applicable to various advanced technologies in radiotherapy, aiming to improve safety measures and overall process efficiency.
- * The methodology focuses on identifying vulnerabilities in treatment procedures by evaluating potential failure modes, highlighting the need for skilled staff and proper resources in modern radiotherapy.
Article Synopsis
- Modern treatment machines like the TrueBeam have minimal differences in beam data across units, but lack specific multi-leaf collimator (MLC) parameters like leaf transmission factor (LTF) and dosimetric leaf gap (DLG) in their average data provided by vendors.
- A survey involving 69 sets of linear accelerator data from 58 institutions explored MLC measurement protocols for intensity-modulated (IMRT) and volumetric modulated radiotherapy (VMAT).
- Findings reveal that while LTF values showed small variability across units, DLG values varied significantly, with many institutions adjusting DLG upwards and standardizing measurement conditions, ultimately providing median values to improve MLC installation accuracy.
Purpose: Detector-dependent interinstitutional variations of the beam data may lead to uncertainties of the delivered dose to patients. Here we evaluated the inter-unit variability of the flattened and flattening filter-free (FFF) beam data of multiple TrueBeam (Varian Medical Systems) linear accelerators focusing on the small-field dosimetry.
Methods: The beam data of 6- and 10-MV photon beams with and without flattening filter measured for modeling of an iPLAN treatment planning system (BrainLAB) were collected from 12 institutions - ten HD120 Multileaf Collimator (MLC) and two Millennium120 MLC.
[A Human Factors Study Using VTA for Incident Cases in Radiotherapy].
Nihon Hoshasen Gijutsu Gakkai Zasshi
December 2019
Article Synopsis
- The increased precision of radiotherapy has raised workloads, making human errors more likely during treatment, which is a concern given the need for both efficiency and thoroughness.
- The study analyzed five incident cases across four facilities to identify human factors contributing to errors, highlighting that deviations from standard operations often stem from patient-specific issues and unfamiliar situations.
- Recommendations to reduce human errors include minimizing time pressure and multitasking, improving work conditions to enhance resilience, clarifying ambiguous procedures, and promoting standardized methods.
Article Synopsis
- - This study investigates how different types of detectors affect the variability in specific beam parameters for TrueBeam™ linear accelerators across 19 institutions, focusing on metrics like percent depth dose (PDD), off-center ratio (OCR), and output factor (OPF).
- - Data collected from 24 beam datasets revealed that while ionization chambers (CC13 and PTW31010) generally showed larger penumbra widths and consistent measurements, diode and diamond detectors exhibited significantly smaller penumbra values.
- - Overall, findings indicated that most beam-specific parameters, excluding penumbra measurements, had minimal inter-institutional variability, showing less than 1% differences, suggesting reliability in these measurements across various detectors, despite some exceptions in
If the vendor's representative beam data (RBD) for TrueBeam linear accelerators are to be valid for use in clinical practice, the variations in the beam data used for beam modeling must be small. Although a few studies have reported the variation of the beam data of the TrueBeam machines, the numbers of machines analyzed in those studies were small. In this study, we investigated the variation in the beam data for 21 TrueBeam machines collected from 17 institutions with their agreement.
View Article and Find Full Text PDFDetector selection and technical problems can result in large variations in small-field-dosimetry data among institutions. In this study, we evaluated inter-institutional variability in the small-field-beam data of the Novalis Tx linear accelerator (Varian Medical Systems and BrainLAB) with an HD120 multileaf collimator. Beam data for modeling an iPLAN treatment planning system (BrainLAB) were collected from 19 institutions and median values of percentage depth doses (PDD), diagonal profiles, transversal profiles, and ratios of detector readings (detector output factors; OF ) were calculated.
View Article and Find Full Text PDFArticle Synopsis
- A multi-institutional study was conducted to confirm the feasibility of using 3-5% action levels for independent monitor unit (MU) verification across 12 institutions, analyzing a total of 5936 fields.
- The results showed that the mean verification difference was 1.0 ± 3.6%, but larger discrepancies were noted specifically in breast and lung treatments, highlighting the need for careful analysis.
- It concluded that while the 5% action level is usable, clinicians must pay attention to the significant variations found in breast and lung treatment plans, especially related to field shape and reference point placements.
Article Synopsis
- A multi-institutional study was conducted to assess the discrepancies between radiotherapy treatment planning systems (TPSs) and verification programs for IMRT and VMAT.
- The analysis involved 477 IMRT/VMAT plans, revealing that the sliding window technique had greater negative systematic differences compared to the step-and-shoot technique, and that head and neck plans showed larger dose variations than prostate plans.
- The findings suggest that a local dose difference of ±5% may be a reasonable benchmark for institutions when evaluating agreement between primary calculations and verification for these radiation therapies.
Article Synopsis
- * Researchers conducted a multi-institutional investigation into the precision of independent dose verifications using a wedge off-axis calculation and found improved agreement with treatment planning systems.
- * Results indicated that using the wedge off-axis calculation led to better confidence limits (around 2% for both physical and non-physical wedges) compared to over 5% without it, suggesting a tolerance level of 5% for these plans similar to conventional techniques.
Purpose: The aim of the present investigation was to evaluate the dosimetric variation regarding the analytical anisotropic algorithm (AAA) relative to other algorithms in lung stereotactic body radiation therapy (SBRT). We conducted a multi-institutional study involving six institutions using a secondary check program and compared the AAA to the Acuros XB (AXB) in two institutions.
Methods: All lung SBRT plans (128 patients) were generated using the AAA, pencil beam convolution with the Batho (PBC-B) and adaptive convolve (AC).
[influence and improvement of metal artifacts in dental structures by CT for radiation treatment planning: reconstruction of transverse images using oblique images by gantry tilt scanning].
Nihon Hoshasen Gijutsu Gakkai Zasshi
March 2007
Article Synopsis
- Intensity-modulated radiation therapy (IMRT) requires precise treatment planning, which is often affected by metal artifacts from dental structures in CT images at the oropharynx region.
- These artifacts hinder the visualization of tumors and lymph nodes, leading to inaccurate CT values that can impact radiation treatment.
- To address this, researchers simulated treatment planning using both normal and artifact-affected CT images and found that using CT images without artifacts leads to more accurate target volume measurements and improved dose distribution.