WCB 2021 - Online

Session Item

May 06
09:00 - 10:15
Brachytherapy physics 2030 – Dosimetry for nuclides and radiation
09:00 - 09:18
Nuclides and dose delivery devices – An overview and Comparison
José Perez Calatayud, Spain


Nuclides and dose delivery devices – An overview and Comparison
Abstract Text
In this presentation, an overview of the available brachytherapy (BT) photon sealed sources and applicators is provided from a clinical practice perspective. In low energy (<50 keV) and low dose rate (LDR) modality the most used sources are based on I-125, Pd-103 and Cs-131. The main application is permanent implants in the prostate and the thoracic and abdominal cavities, and in temporary ophthalmic implants using plaques to a lesser extent. The pros and cons of each radionuclide are commented upon from physical, radiobiological and practical viewpoints. The most used radionuclide in BT is Ir-192, in high dose rate (HDR) or pulsed dose rate (PDR) mode. The main BT applications are post-surgery endometrium, prostate and cervix. The major developments in applicators are for the cervix case, with interstitial component compatible with magnetic resonance. In recent years there has been popular deployment of Co-60 due to its longer half-life advantage. Comparisons of HDR Ir-192 vs Co-60 are discussed considering different aspects as radiation protection, dose distribution, source change frequency, peripheral dose and treatment time. HDR electronic BT sources (x-rays 50-70 kV) are also utilized in BT within endocavitary with vaginal cylinders and in the breast with balloon applicators. Their advantages due to shielding for the patient and the treatment environment, ability to switch on and off, and lack of radioactivity waste and regulatory controls are discussed. Further, there has been a significant boost in the last decade with the use of BT to treat the skin and superficial targets. Electronic BT sources are well suited for these shallow lesions. Electronic BT has been strongly incorporated into this modality. Specific applicators using HDR Ir-192 sources include the Leipzig and Valencia for treatment of smaller lesions, i.e., diameters < 3 cm. The recent AAPM-ESTRO TG-253 Report produced specific recommendations for dosimetry and quality assurance for the treatment of superficial lesions. A brief summary is presented. As the assignment of radiation sources into the BT category (instead of being categorized as teletherapy sources) may be considered controversial, the ramifications of this decision are examined for some sources. Finally, innovative and unconventional BT sources, applicators, and delivery systems are examined as quickly advancing areas in the field of clinical BT. Current research and societal guidance reports including recommendations for clinical users are summarized, including the published and ongoing efforts of the joint AAPM+ESTRO TG-167, TG-292, and TG-337 Reports. These reports cover innovative BT devices and applications, robotic BT delivery systems, and intensity modulated BT sources and applicators using shielded BT sources or dynamic applicators, respectively.