Brachytherapy

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Brachytherapy, 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. Conversely, external beam radiotherapy, or teletherapy, is the application of radiation that has been externally produced by a linear accelerator. Brachytherapy is commonly used to treat localized prostate cancer^[1] and cancers of the head and neck.^[2]

Brachy is a Greek word for close by, so brachytherapy roughly translated is short distance therapy.

Brachytherapy can be split into four main types:

• Surface Applicator or "Mould" 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.

• 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. Prostate cancer treatment with Iodine-125 seeds is also classified as interstitial brachytherapy. 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, although it can also be performed on the nasopharynx.

• Intravascular brachytherapy places a catheter with the sources inside the vasculature. The most common application of this method uses Strontium-90 in the Novoste Beta-Cath System (now offered by Best Vascular), is the treatment of coronary in-stent restenosis, although the therapy has also been investigated for use in the treatment of peripheral vasculature stenoses.

Remote and Manual Afterloading Machines

"Afterloading" Machines as they are called are the machines that perform brachytherapy treatments.

Remote Afterloading Machines

Remote Afterloading machines are so called as they can deliver their treatment remotely. These means that the nurse or therapeutic radiographer that administers can leave the room (located either in theatre or ward) and start the treatment outside. Empty catheters are placed into the patient and the "live" source is entered at a later date. This means that the non active dummy guides can be repositioned & checked. This means that the source is not placed into the guides until the positioning is acceptable. The machine they runs a pnematic drive wire through the catheters and guide wires to check that there are no obstructions and the soure can safely run through the course of it. After this the check has been performed the source leaves its secure safe and the treatment begins. The development of the remote afterloading machines is a benefit to the many radiation safety issues surrounding manual afterloading machines.

Manual Afterloading Machines

Manual afterloading machines cannot be activated from outside the room.The source has to be manually inserted. It is prepared in a lab as a "source train" and inserted in either theatre or ward. The source cannot be unloaded for nursing visits. There are many radiation issues with the handling of patients and nursing of patients receive manual afterloading treatment.

Advantages of Remote over Manual

• No Radiation exposure in patient transit
• No exposure to theatre or ward staff

HDR brachytherapy

High Dose Rate (HDR) brachytherapy is a common brachytherapy method. Applicators in the form of catheters are arranged, usually according to the Manchester or Paris system on, or in, the patient. A high dose rate source (often iridium 192) is then driven along the catheters on the end of a wire by a machine while the patient is isolated in a room. The source dwells in a preplanned position for a preset time before stepping forward along the catheter and repeating, to build up the required dose distribution. The advantage of this treatment over implanting radioactive sources directly is that there is lower staff exposure and the source can be more active due to low staff exposure, thus making treatment times quicker.

LDR brachytherapy

Low dose rate (LDR) brachytherapy with a machine works in a similar way. Another variant is the sources being in the form of active and inactive balls which are again, driven into the patient using a machine.

References

Nuclear Technology [ v]·[ d]·[ e]
Nuclear engineering	Nuclear physics > Nuclear fission | Nuclear fusion | Radiation | Ionizing radiation | Atomic nucleus | Nuclear reactor | Nuclear safety
Nuclear material	Nuclear fuel > Fertile material | Thorium | Uranium | Enriched uranium | Depleted uranium | Plutonium
Nuclear power	Nuclear power plant > Radioactive waste | Fusion power | Future energy development | Inertial fusion power plant | Pressurized water reactor | Boiling water reactor | Generation IV reactor | Fast breeder reactor | Fast neutron reactor | Magnox reactor | Advanced gas-cooled reactor | Gas cooled fast reactor | Molten salt reactor | Liquid metal cooled reactor | Lead cooled fast reactor | Supercritical water reactor | Very high temperature reactor | Pebble bed reactor | Integral Fast Reactor | Nuclear propulsion | Nuclear thermal rocket | Radioisotope thermoelectric generator
Nuclear medicine	PET | Radiation therapy | Tomotherapy | Proton therapy | Brachytherapy
Nuclear weapons	History of nuclear weapons > Nuclear warfare | Nuclear arms race | Nuclear weapon design | Effects of nuclear explosions | Nuclear testing | Nuclear delivery | Nuclear proliferation | List of countries with nuclear weapons | List of nuclear tests

 

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