Yoshiaki Takagawa

Analysis of operative duration of image-guided brachytherapy for cervical cancer

The present study aimed to analyze the operative duration of image-guided brachytherapy (IGBT) for cervical cancer performed at our institution. We enrolled cervical cancer patients who had undergone tandem and ovoid-based intracavitary brachytherapy (ICBT) or intracavitary and interstitial brachytherapy (IC/ISBT) between 2020 and 2024. Cone beam computed tomography (CBCT), CT, or CT + MRI were used for IGBT. For each IGBT session, we retrospectively reviewed the following: application time (AT-defined as the duration from entry into the operating room to the initial image acquisition); planning time (PT-defined as the duration from the initial image acquisition to the start of irradiation); and total operation time (TOT- defined as the duration from entry to exit of the operating room). We analyzed a total of 126 sessions in 36 patients, consisting of 99 ICBT-only sessions and 27 IC/ISBT sessions. The IC/ISBT sessions had a significantly longer mean operative duration than the ICBT-only sessions. The IC/ISBT sessions with three or more interstitial needles had significantly longer AT and TOT. However, the IC/ISBT sessions with one needle showed no significant difference in operative duration compared to ICBT-only sessions. CBCT, CT, and CT + MRI were used in 42, 76, and 8 sessions, respectively. In the ICBT patients, CT + MRI had the longest PT. However, there was no significant differences in TOT among CBCT, CT, and CT + MRI. IC/ISBT sessions with one needle had no significant difference in operative duration compared to ICBT-only sessions. There was no significant difference in TOT between CT + MRI-based IGBT and CT-based IGBT.

Efficient workflow and clinical validation of in-house 3D-printed vaginal cylinders for high-dose-rate brachytherapy for gynecologic malignancies

This study developed an efficient methodology for in-house 3D-printed vaginal cylinders for gynecologic tumor treatment by evaluating their radiation attenuation, geometric accuracy, and efficacy. Ultimately, we aim to establish a simple, cost-effective approach that facilitates broad clinical adoption. Patient-specific vaginal cylinders were designed based on anatomical contours from the treatment planning system (TPS) using CAD software. The process was optimized to minimize manpower and time costs. Radiation attenuation of the 3D printer material was compared with that of water using the Monte Carlo method. Geometric accuracy was automatically analyzed via an in-house MATLAB program. Efficacy was assessed in cases of postoperative vaginal stump recurrence and vaginal cancer with paravaginal invasion. The tumor shape, delineated by TPS, was imported into CAD software, and the catheter pathway model, designed via subtraction processing, was placed at the optimal position and angle. The design process took approximately 15 min, and the entire workflow was completed within a week, demonstrating its practicality for clinical use. The radiation attenuation error was < 3% compared with water, and the geometric accuracy error was < 0.2 mm. The patient-specific vaginal cylinder provided a favorable dose distribution and was effective in complex cases. A feasible workflow was established, allowing in-house design and manufacturing with reduced manpower and time costs. With no material or processing issues, this approach is safe, practical, and promising for widespread adoption in personalized brachytherapy.

Laminaria tent insertion in preplanning MRI for CT-based cervical cancer brachytherapy

Preplanning magnetic resonance imaging (MRI) is routinely used in image-guided adaptive brachytherapy (IGABT) for cervical cancer. However, a preplanning MRI performed without an applicator does not have good accuracy of image fusion with a planning computed tomography (CT) performed with an applicator. This study aimed to evaluate the efficacy of laminaria tent insertion during pre-planning MRI for cervical cancer brachytherapy (BT). Sixteen patients with cervical cancer were enrolled in the study. Images obtained from a single preplanning MRI performed with a laminaria tent inserted into the cervix were fused with images from the planning CT performed with an applicator during each BT session. The alignment between the high-risk clinical target volume on MRI (HR-CTV Fifty-nine BT sessions were analyzed. Fusion images for 39 (66%) sessions were categorized as excellent, and those for the remaining 12 (20%) sessions were available, and 8 (14%) were not available. Complications reported after laminaria tent insertion were grade-1 fever for 5 (8%) BT sessions in 5 patients and grade-1 pain for 8 (13%) sessions in 5 patients. Laminaria tent insertion during pre-planning MRI may improve the accuracy of image fusion with planning CT and may help delineate the HR-CTV in CT-based IGABT for cervical cancer.

A novel dose-based intra-preplan method for high-dose-rate brachytherapy in cervical cancer using modeling and optimization algorithms

This study presents the dose-based intra-preplan (DIP) method for intracavitary/interstitial brachytherapy (IC/ISBT) in cervical cancer, optimizing catheter configurations based on dose distribution. This study aimed to assess the DIP method's clinical feasibility and efficacy. The DIP method incorporates the implant modeling function and the hybrid inverse planning optimization algorithm in Oncentra Brachy. Virtual applicator and catheter models were created and merged with patient-specific computed tomography images. Subsequently, an optimization algorithm was used to automatically determine the optimal catheter configuration-including the number, positions, and insertion depths. The workflow was retrospectively validated in 14 IC/ISBT patients treated with the Geneva applicators. Catheter configurations from the DIP and conventional intra-preplan (IP) methods were compared in terms of catheter number and dose-volume histogram (DVH) parameters for high-risk clinical target volume (CTV The DIP workflow was successfully established. Compared to the IP method, the DIP method achieved similar DVH parameters for both CTV The DIP method enables patient-specific optimization of minimal catheter configurations and supports the broader implementation of high-quality IC/ISBT.