Brachytherapy (Arip Nurahman)

Brachytherapy (from the Greek brachy, meaning "short"), also known as sealed source radiotherapy or endocurietherapy, is a form of radiotherapy where a radioactive source is placed inside or next to the area requiring treatment. Brachytherapy is commonly used to treat localized prostate cancer^[1][2], cervical cancer ^[1] and cancers of the head and neck.^[3] Brachytherapy to prevent restenosis after stenting associated with coronary angioplasty has been proven safe and effective in clinicals trials, such the START and START 40/20 Trials.

External links

• The GEC ESTRO Handbook of Brachytherapy
• 3D illustration of how the procedure is commonly performed for prostate cancer
• Social community focused on breast brachytherapy

Types

Brachytherapy exists in numerous forms:

• Mold brachytherapy. Superficial tumours can be treated using sealed sources placed close to the skin. Dosimetry is often performed with reference to the Manchester system; a rule-based approach designed to ensure that the dose to all parts of the target volume is within 10% of the prescription dose.

• Strontium plaque, used for very superficial lesions less than 1 mm thick. The plaque is a hollow, thin silver casing that encloses a radioactive strontium-90 powdered salt. The beta (electron) particles produced from strontium's radioactive decay have a very shallow penetration. Typically the Sr-90 plaque is placed on the bed of a resected pterygium. A stat dose of around 10-12 Gy is delivered by timing the contact. As the electrons only penetrate a few mm of air, radiation protection issues are slightly less but very different from other radiation sources. Cleaning the plaques that are placed on the eye sclera is required but must be gentle because the silver casing is thin and easily damaged. Strontium belongs to the same chemical class as calcium, i.e., an alkaline earth metal, and so will co-locate in the bone if any strontium salt makes contact with the eye and is absorbed. Operators can prevent exposure to the beta rays by facing the applicator away from their bodies.

• Interstitial brachytherapy. Here the sources are inserted into tissue. The first treatments of this kind used needles containing radium-226, arranged according to the Manchester system, but modern methods tend to use iridium-192 wire. Iridium wire can be arranged either using the Manchester or the Paris system; the latter was designed specifically to take advantage of the new nuclide. This also includes the removal of small lung cancers through wedge resection followed by placement of a brachymesh device, consisting of absorbable suture containing iodine-125 seeds to reduce the risk of recurrence. LDR prostate brachytherapy treats prostate cancer using iodine-125 or palladium-103 seeds . This latter treatment type differs from other interstitial treatments as the sources are left in the prostate permanently, rather than being removed after the intended treatment time. For details of the gamma emitters please see commonly used gamma emitting isotopes.

• Intracavitary brachytherapy places the sources inside a pre-existing body cavity. The most common applications of this method are gynaecological in nature,^[2] although it can also be performed on the nasopharynx.

• Intravascular brachytherapy places a catheter inside the vasculature through which sources are sent and returned. The most common application of this method is the treatment of coronary in-stent restenosis, although the therapy has also been investigated for use in the treatment of peripheral vasculature stenoses and also considered for the treatment of atrial fibrillation. Although a few systems have been used successfully for intravascular brachytherapy, the only device currently available is the Novoste Beta-Cath System from Best Vascular, Inc. which uses beta-emitting sources of Sr/Y-90.

• Electronic brachytherapy places a miniature low energy (<>

(Arip Nurahman)