Publications by authors named "Tatsuya Sakasai"
Article Synopsis
- The study focused on tracking the movements of the uterus during radiation treatment in patients with cervical cancer, using MR imaging to analyze changes in uterus and cervix positioning as well as bladder and rectal volume effects.
- Findings indicated that the uterus moved more than the cervix and was more closely linked to bladder movements, which could affect treatment dosage.
- The research underlines the importance of adjusting treatment plans in real-time for moving organs, suggesting that personalized planning is necessary to ensure effective radiation delivery, though this can lead to longer treatment times.
Article Synopsis
- The study investigates how the dose distribution is affected by different target motions and gating latency in a magnetic resonance-guided radiotherapy (MRgRT) system using a specially designed phantom.
- It tests various target movements, including periodic and continuous motions, while measuring the dose distributions with radiochromic film to analyze accuracy under different conditions.
- Results indicate that as beam switching and target velocity increase, the accuracy of dose distribution decreases, and the overall gating latencies were estimated to be around 0.51 seconds for beam-hold and 0.35 seconds for beam-on.
The first magnetic resonance (MR)-guided radiotherapy system in Japan was installed in May 2017. Implementation of online MR-guided adaptive radiotherapy (MRgART) began in February 2018. Online MRgART offers greater treatment accuracy owing to the high soft-tissue contrast in MR-images (MRI), compared to that in X-ray imaging.
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- - The study focuses on enhancing quality control for online magnetic resonance-guided adaptive radiotherapy (MRgART) by identifying risks through a detailed failure mode and effect analysis (FMEA).
- - A multidisciplinary team identified 153 failure modes and categorized them into MRgRT, online ART, and conventional RT, highlighting high-risk areas related to structure segmentation, treatment planning, and beam delivery.
- - The findings from the FMEA provide insights into risk characteristics, aiming to improve quality assurance programs specifically for online MRgART technologies.
Purpose: In this study, we report on our proposed phantom based on the new end-to-end (E2E) methodology and its results. In addition, we verify whether the proposed phantom can replace conventional phantoms.
Methods: The hexagonal-shaped newly designed phantom has pockets on each side for a film dosimeter of size 80 × 90 mm , which is easily removable, considering the Co penumbra.
Objective: This study aimed to assess the dosimetric effect of intestinal gas of stereotactic magnetic resonance (MR)-guided adaptive radiation therapy (SMART) on target and critical organs for pancreatic cancer without online electron density correction (EDC).
Methods: Thirty pancreatic cancer patients who underwent online SMART were selected for this study. The treatment time of each stage and the total treatment time were recorded and analyzed.
In our institution, we installed MRI-guided radiotherapy system (MRIdian, ViewRay Inc.), allowing to perform on-line adaptive radiotherapy (ART). The MRIdian has three Co sources with 120 degrees apart, equipped with MRI system using a static magnetic field of 0.
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- The study aimed to establish the commissioning procedure for Monte Carlo modeling in an MRI-guided radiotherapy system (MRIdian) under a magnetic field of 0.345 T using experimental data and Geant4 simulations.
- Key objectives included assessing depth-dose and lateral profiles with EBT3 film and comparing calculation accuracy under the specified magnetic field.
- Results showed that Geant4 produced accurate depth-dose profiles and a significant reduction in surface dose due to electron contamination, confirming the system's reliability with a high pass rate in gamma analysis.