Evaluation of a Monte Carlo-based algorithm for the influence of totally implantable venous access ports in external rad
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ORIGINAL ARTICLE
Evaluation of a Monte Carlo‑based algorithm for the influence of totally implantable venous access ports in external radiation therapy Toshiki Takeshita1,2 · Taiki Magome3 · Ryuji Watanabe1 · Shiro Onozawa1 · Konatsu Tsuchiya4 · Masao Tago1 · Masayuki Sasaki2 Received: 20 July 2020 / Accepted: 17 October 2020 © Japan Radiological Society 2020
Abstract Purpose This study aimed to assess whether a Monte Carlo (MC)-based algorithm reflects the influence of totally implantable venous access ports (TIVAPs) in external radiation therapy. Materials and Methods The present study comprised two steps: experimental measurements of depth doses and surface doses with and without TIVAPs and calculation with an MC-based algorithm. Results The TIVAP-associated maximum dose reduction compared with the dose at the same depths without TIVAPs was 7.8% at 4 MV, 6.9% at 6 MV, and 5.7% at 10 MV in measurement, and 7.4% at 4 MV, 6.6% at 6 MV, and 5.5% at 10 MV in calculation. Relative surface doses were higher with TIVAPs made of titanium, due to a higher fluence of backscattered electrons from the TIVAPs, than with plastic TIVAPs. There were no significant differences in the relative differences between the measured and calculated doses of the titanium TIVAP group and the plastic TIVAP group at 4 MV (p = 0.99), 6 MV (p = 0.67), and 10 MV (p = 0.54). Conclusion TIVAPs caused target dose reductions and dose increase near the TIVAP, especially when made of titanium. The influences are reflected in the MC-based algorithm. Keywords Totally implantable venous access port · Radiation therapy · Dose distribution · X-ray voxel-based monte carlo
Introduction
* Masayuki Sasaki [email protected]‑u.ac.jp Toshiki Takeshita [email protected] 1
Department of Radiology, Teikyo University School of Medicine Mizonokuchi Hospital, 5‑1‑1 Futago Takatsu‑ku, Kawasaki, Kanagawa 213‑8507, Japan
2
Division of Medical Quantum Science, Department of Health Sciences, Kyushu University Graduate School of Medical Sciences School of Medicine, 3‑1‑1 Maidashi, Higashi‑ku, Fukuoka 812‑8582, Japan
3
Department of Radiological Sciences, Komazawa University Faculty of Health Sciences Graduate School of Health Sciences, Tokyo, Japan
4
Tokyo Radiation Oncology Clinic, Tokyo, Japan
Totally implantable venous access port (TIVAP) systems are used in patients receiving chemotherapy, blood products, parenteral nutrition, and long-term antimicrobial treatment [1]. TIVAPs are made of silicone and titanium or silicone and plastic (polyoxymethylene), and the influence of TIVAPs on radiation therapy has been investigated [2, 3]. With titanium TIVAPs, a dose increase due to electron backscatter was observed. Since TIVAPs are inserted near the body surface, there is a concern about dose reduction in deep regions and dose increase at the surface level due to backscatter. Gossman et al. evaluated the pencil beam convolution algorithm, the analytic anisotropic algorithm (AAA) and the full Monte Carlo algorithm; only the full Monte Ca
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