Analysis of applicator displacement in accelerated partial breast irradiation using a strut-based design brachytherapy applicator

Tadashi Kubo; Chie Kurokawa; Tatsuya Inoue; Tomoki Fujii; Kazunori Miyaura; Hidenori Shinjo; Yoshikazu Kagami; Naoto Shikama

doi:10.1016/j.brachy.2023.05.007

Analysis of applicator displacement in accelerated partial breast irradiation using a strut-based design brachytherapy applicator

Brachytherapy. 2023 Sep-Oct;22(5):655-664. doi: 10.1016/j.brachy.2023.05.007. Epub 2023 Jul 14.

Authors

Tadashi Kubo¹, Chie Kurokawa², Tatsuya Inoue², Tomoki Fujii³, Kazunori Miyaura⁴, Hidenori Shinjo⁵, Yoshikazu Kagami⁵, Naoto Shikama²

Affiliations

¹ Department of Radiation Oncology, Graduate School of Medicine, Juntendo University, Tokyo, Japan; Department of Radiotechnology, Showa University Northern Yokohama Hospital, Kanagawa, Japan. Electronic address: t-kubo@juntendo.ac.jp.
² Department of Radiation Oncology, Juntendo University, Tokyo, Japan.
³ Department of Radiotechnology, Showa University Hospital, Tokyo, Japan.
⁴ Graduate School of Health Sciences, Showa University, Tokyo, Japan.
⁵ Division of radiation oncology, Department of Radiology, Showa University School of Medicine, Tokyo, Japan.

PMID: 37455152
DOI: 10.1016/j.brachy.2023.05.007

Abstract

Purpose: This study aimed to identify factors associated with strut-adjusted volume implant (SAVI) displacement in accelerated partial breast irradiation (APBI) using a SAVI device.

Methods and materials: We retrospectively analyzed computed tomography scans taken at the time of treatment planning and immediately before treatment in 61 patients (median age; 55 years, range; 40-85) treated with SAVI and determined the amount of SAVI displacement that occurred between the time from planning to the treatment. The displacement was calculated for the CT axis and SAVI axis, which is related to the SAVI structure. To investigate the cause of the displacement, multivariate analysis was performed on the calculated standard deviation and the insertion angle of SAVI with respect to the sternum in each cross-section, breast density, amount of air around the SAVI, and SAVI length inside the patient to obtain the β coefficient (p-value).

Results: On the CT coordinate system, positive correlations were observed between the SAVI insertion angle and air volume in the lateral (β coefficient:0.255-0.483) and rotational directions (β coefficient:0.341). On the SAVI coordinate system, positive correlations were observed between the SAVI insertion angle and air volume in all lateral (β coefficient:0.270-0.354) and rotational directions (β coefficient:0.294). A negative correlation was observed between the SAVI length inside the patient and the rotational direction (β coefficient: -0.262).

Conclusion: SAVI insertion angle, the amount of the air outside SAVI and SAVI insertion length are factors which affect the displacement of the applicator. From the results, the applicator displacement and rotation must be <3 mm and 10^o in order to meet all the dose criteria. Thus, we should be aware of these factors during insertion of the device to avoid the problem in treatment delivery for the APBI.

Keywords: Accelerated partial breast irradiation (APBI); Breast cancer; Displacement; Strut adjusted volume implant (SAVI).

MeSH terms

Brachytherapy* / methods
Breast Neoplasms* / diagnostic imaging
Breast Neoplasms* / radiotherapy
Female
Humans
Prostheses and Implants
Radiotherapy Dosage
Retrospective Studies