Evaluation of cutout factors with small and narrow fields using various dosimetry detectors in electron beam keloid radiotherapy

Article type: Research Article

Authors: Lin, Yu-Fang^{a; b} | Hsieh, Chen-Hsi^{a; c; d; e} | Tien, Hui-Ju^{a; b} | Lee, Yi-Huan^a | Chen, Yi-Chun^a | Lai, Lu-Han^f | Hsu, Shih-Ming^{b; *} | Shueng, Pei-Wei^{a; c; *}

Affiliations: [a] Department of Radiology, Division of Radiation Oncology, Far Eastern Memorial Hospital, New Taipei City, Taiwan | [b] Department of Biomedical Imaging and Radiological Sciences, National Yang Ming Chiao Tung University, Taipei, Taiwan | [c] School of Medicine, College of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan | [d] Institute of Traditional Medicine, School of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan | [e] School of Nursing, Yuan Ze University, Taoyuan, Taiwan | [f] Department of Medical Imaging and Radiological Technology, Yuanpei University of Medical Technology, Hsinchu, Taiwan

Correspondence: [*] Corresponding authors: Pei-Wei Shueng, Professor, School of Medicine, College of Medicine, National Yang Ming Chiao Tung University, No. 155, Sec. 2, Linong Street, Taipei 11221, Taiwan. E-mail: shueng@mail.femh.org.tw and Shih-Ming Hsu, Professor, Department of Biomedical Imaging and Radiological Sciences, National Yang Ming Chiao Tung University, No. 155, Sec. 2, Linong Street, Taipei 11221, Taiwan. E-mail: smhsu@nycu.edu.tw.

Abstract: BACKGROUND:The inherent problems in the existence of electron equilibrium and steep dose fall-off pose difficulties for small- and narrow-field dosimetry. OBJECTIVE:To investigate the cutout factors for keloid electron radiotherapy using various dosimetry detectors for small and narrow fields. METHOD:The measurements were performed in a solid water phantom with nine different cutout shapes. Five dosimetry detectors were used in the study: pinpoint 3D ionization chamber, Farmer chamber, semiflex chamber, Classic Markus parallel plate chamber, and EBT3 film. RESULTS:The results demonstrated good agreement between the semiflex and pinpoint chambers. Furthermore, there was no difference between the Farmer and pinpoint chambers for large cutouts. For the EBT3 film, half of the cases had differences greater than 1%, and the maximum discrepancy compared with the reference chamber was greater than 2% for the narrow field. CONCLUSION:The parallel plate, semiflex chamber and EBT3 film are suitable dosimeters that are comparable with pinpoint 3D chambers in small and narrow electron fields. Notably, a semiflex chamber could be an alternative option to a pinpoint 3D chamber for cutout widths≥3 cm. It is very important to perform patient-specific cutout factor calibration with an appropriate dosimeter for keloid radiotherapy.

Keywords: Cutout factor, electron beam, dosimetry detector, narrow field, keloid

DOI: 10.3233/XST-240059

Journal: Journal of X-Ray Science and Technology, vol. 32, no. 4, pp. 1177-1184, 2024