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Remote High Dose Rate (HDR) Afterload Brachytherapy Explained

5 December, 2011 | Brachytherapy, Radiology

The Advantages of Brachytherapy
Brachytherapy is radiation therapy of cancer. The treatment is performed by placing radioactive sources in or near the tumor. In this way, the tumor is treated from inside the body so it receives the highest possible radiation dose with minimal exposure to the surrounding tissues. Teleradiotherapy, which is achieved by the aid of medical high-energy particles accelerators, is an alternative approach to radiotherapy treatment.

Remote afterloading brachytherapy means that the source is accurately positioned at the tumor by a special mechanical-electronic system through thin tubes or needles. After the treatment, the source is withdrawn into the shielded source-container, which is the major part of the brachytherapy system. Brachytherapy can be performed with short treatment times, high dose rate brachytherapy, or over a longer period of time, low dose or pulsed dose rate brachytherapy. 

Remote Afterloading Brachytherapy for Precision  

 Remote afterloading improves radiation control and provides technical advantages, such as isodose distribution optimization, that improve patient care. Replacing manual afterloading with remote afterloading reduces the radiation exposure to radiation oncologists, physicists, attending physicians, source curators, nurses, and other allied health personnel.

Remote afterloading is an application of the As Low As Reasonably Achievable (ALARA) principle in radiation control. Remote afterloading offers less probability of temporarily misplacing radioactive sources or actually losing sources, events that do occur with manual afterloading.

High dose rate remote afterloading devices yield dose rates greater than 0.2-Gy/min; doses of several gray generally are delivered in minutes. High dose rate remote afterloading is particularly appealing to facilities with large patient populations. If treated by conventional manual brachytherapy instead, prolonged hospitalizations would be indicated. Treating these patients as outpatients, using multiple fraction treatment regimens on a remote high dose rate device, is appealing to the patients. Freestanding radiation therapy centers that do not provide hospital rooms, find high dose rate units appealing, as well. A dedicated treatment suite with an overhead x-ray tube and fluoroscopy can accommodate many patients yearly, as large workloads are possible on a single unit. There is little radiation exposure to attending medical personnel and none to adjacent patients.

Applicators can be rigidly secured for the short treatment times common with high dose rate therapy. Consequently, undesired applicator movement observed during prolonged hospital stays required with brachytherapy is reduced. In some instances, the high dose rate remote afterloading sources can be configured more advantageously, yielding more desirable dose distributions than those achieved with conventional radioactive sources and manual afterloading. And last but not the least, the very small diameter of high activity source in high dose rate remote afterloading system allow treatments of interstitial and intraluminal sites previously untreated or treated only with difficulty with the conventional techniques.

The Features of Remote Afterload Brachytherapy Systems

All remote afterload systems offer four essential features:
• A primary storage safe to contain the sources when not in use.
• A mechanism to move the source from the storage safe to and from the applicator in the patient.
• A system to maintain the source in the applicator for a set time in desired positions and to determine their position.
• A mechanism to return the source to the storage safe at the end of treatment and during power failures or other emergencies.

Remote Afterloading Systems Offer Flexibility 
Remote afterloading of radioactive sources for brachytherapy is becoming increasingly popular as evidenced by the increased sales of remote afterloading systems. With low, medium, and high dose rate options, these units offer the potential for superior dose distributions and the practical advantages of better radiation protection. However, as with any new technology, these systems generate a host of new concerns that the users must address. Remote afterloading systems present a unique set of radiation control questions, particularly when the units fail to function adequately and the sources stick in the applicators. Also, there are no explicit protocols for source calibration. Often, calibration of these sources yields activities at odds with those provided by the manufacturers. This need for a dosimetry protocol is particularly important for the high-activity 192Ir sources which are exchanged frequently.
Often existing hospital rooms or teletherapy vaults not originally designed for the remote afterloading systems are used to house these units. Certain disadvantages in such uses should be considered.