1
|
Ogawa S, Yasui K, Hayashi N, Saito Y, Hayashi S. Impact of Dose Perturbations Around Brachytherapy Seeds in External-Beam Radiotherapy Planning: A Fundamental and Clinical Validation Using Treatment Planning System-Based Monte Carlo Simulations. Cureus 2023; 15:e48041. [PMID: 38046495 PMCID: PMC10689119 DOI: 10.7759/cureus.48041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/31/2023] [Indexed: 12/05/2023] Open
Abstract
Background This study evaluates dose perturbations caused by nonradioactive seeds in clinical cases by employing treatment planning system-based Monte Carlo (TPS-MC) simulation. Methodology We investigated dose perturbation using a water-equivalent phantom and 20 clinical cases of prostate cancer (10 cases with seeds and 10 cases without seeds) treated at Fujita Health University Hospital, Japan. First, dose calculations for a simple geometry were performed using the RayStation MC algorithm for a water-equivalent phantom with and without a seed. TPS-independent Monte Carlo (full-MC) simulations and film measurements were conducted to verify the accuracy of TPS-MC simulation. Subsequently, dose calculations using TPS-MC were performed on CT images of clinical cases of prostate cancer with and without seeds, and the dose distributions were compared. Results In clinical cases, dose calculations using MC simulations revealed hotspots around the seeds. However, the size of the hotspot was not correlated with the number of seeds. The maximum difference in dose perturbation between TPS-MC simulations and film measurements was 3.9%, whereas that between TPS-MC simulations and full-MC simulations was 3.7%. The dose error of TPS-MC was negligible for multiple beams or rotational irradiation. Conclusions Hotspots were observed in dose calculations using TPS-MC performed on CT images of clinical cases with seeds. The dose calculation accuracy around the seeds using TPS-MC simulations was comparable to that of film measurements and full-MC simulations, with differences within 3.9%. Although the clinical impact of hotspots occurring around the seeds is minimal, utilizing MC simulations on TPSs can be beneficial to verify their presence.
Collapse
Affiliation(s)
- Shuta Ogawa
- Department of Radiation Oncology, Tohoku University Graduate School of Medicine, Sendai, JPN
- Department of Radiation Physics and Technology, Southern Tohoku Proton Therapy Center, Koriyama, JPN
| | - Keisuke Yasui
- School of Medical Sciences, Fujita Health University, Toyoake, JPN
| | - Naoki Hayashi
- School of Medical Sciences, Fujita Health University, Toyoake, JPN
| | - Yasunori Saito
- Division of Radiology, Fujita Health University Hospital, Toyoake, JPN
- School of Medical Sciences, Fujita Health University, Toyoake, JPN
| | - Shinya Hayashi
- Department of Radiation Oncology, Fujita Health University School of Medicine, Toyoake, JPN
| |
Collapse
|
2
|
Kanda D, Hanada T, Yoshida K, Tanaka T, Eriguchi T, Yorozu A, Ohashi T, Shigematsu N. Evaluation of dose perturbations around iodine-125 seed sources in supplemental external beam prostate radiotherapy. JOURNAL OF RADIATION RESEARCH 2023:7152939. [PMID: 37154504 DOI: 10.1093/jrr/rrad023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2022] [Revised: 02/07/2023] [Accepted: 03/13/2023] [Indexed: 05/10/2023]
Abstract
We investigated dose perturbations caused by 125I seeds in patients undergoing supplemental external beam radiotherapy (EBRT) for prostate cancer. We examined two types of nonradioactive seed models: model 6711 and model STM1251. All experiments were performed using a water-equivalent phantom. Radiochromic film was used to measure the dose distributions adjacent to the seeds upstream and downstream of the external beam source. Single and clusters of multiple seeds were placed in slots in a solid water (SW) slab to measure dose perturbations with separate versus dense seed placement at beam energies of 6 or 10 MV. Monte Carlo simulations (MCSs) were also performed to include the theoretical basis against film dosimetry. Distinct patterns of dose enhancement (buildup [BU]) were upstream, and dose reduction (builddown [BD]) were downstream of the radiation source. Model 6711 with lower photon beam energies produced larger dose perturbations of BU and BD than the model STM1251. The results showed the same tendency with different seed placements and beam energies. However, these differences were not observed in the rotational irradiation measurement, which replicated a clinical plan. Dose perturbations around seeds result in dose enhancement and dose reduction with varying impact depending on the photon beam energy and seed type. This has the potential to cancel out these perturbations using multiple beam direction fields.
Collapse
Affiliation(s)
- Daisuke Kanda
- Department of Radiology, Tokyo Medical Center, National Hospital Organization, Higashigaoka 2-5-1, Meguro-ku, Tokyo 152-8902, Japan
| | - Takashi Hanada
- Department of Radiology, Tokyo Medical Center, National Hospital Organization, Higashigaoka 2-5-1, Meguro-ku, Tokyo 152-8902, Japan
- Department of Radiology, Keio University School of Medicine, Shinanomachi 35, Shinjuku-ku, Tokyo 160-8582, Japan
| | - Kayo Yoshida
- Department of Radiology, Keio University School of Medicine, Shinanomachi 35, Shinjuku-ku, Tokyo 160-8582, Japan
| | - Tomoki Tanaka
- Department of Radiology, Keio University School of Medicine, Shinanomachi 35, Shinjuku-ku, Tokyo 160-8582, Japan
| | - Takahisa Eriguchi
- Radiation Oncology Center, Ofuna Chuo Hospital, Ofuna 6-2-24, Kamakura, Kanagawa 247-0056, Japan
| | - Atsunori Yorozu
- Department of Radiology, Tokyo Medical Center, National Hospital Organization, Higashigaoka 2-5-1, Meguro-ku, Tokyo 152-8902, Japan
| | - Toshio Ohashi
- Department of Radiology, Keio University School of Medicine, Shinanomachi 35, Shinjuku-ku, Tokyo 160-8582, Japan
| | - Naoyuki Shigematsu
- Department of Radiology, Keio University School of Medicine, Shinanomachi 35, Shinjuku-ku, Tokyo 160-8582, Japan
| |
Collapse
|