afterloader

An afterloader is a medical device used in brachytherapy to remotely place and retrieve radioactive sources within or near a patient’s tumor. It enables clinicians to deliver precise, localized radiation doses while minimizing occupational exposure. Afterloaders are commonly used in treatments for gynecologic, prostate, breast, head and neck, and certain skin cancers.

Modern afterloaders are usually electronic remote afterloaders that deploy a small sealed radioactive source (often iridium-192 or cobalt-60) along flexible catheters or applicators already positioned in the patient. The system controls source position and dwell time at multiple locations, allowing three-dimensional dose shaping. Low-dose-rate (LDR) brachytherapy historically used manual loading of long-lived sources; contemporary practice favors high-dose-rate (HDR) afterloaders for shorter, outpatient procedures, though LDR and pulsed-dose-rate approaches remain in some settings.

Key components include the shielded source storage, drive mechanism, applicator connections, treatment planning interface, and safety interlocks. Safety features typically incorporate redundant interlocks, door and motion sensors, emergency source retraction, and on-board radiation monitors. Operation requires specialized training, quality assurance, and adherence to regulatory and licensing requirements to ensure patient and staff safety.

Advantages of afterloading include improved dose conformity, reduced staff exposure, and flexible treatment planning. Limitations and considerations include the need for careful applicator placement, potential for source or applicator displacement, and strict maintenance and inspection protocols. Alternative techniques include electronic brachytherapy and external beam radiotherapy depending on clinical indications.