Permanent Seed Prostate Brachytherapy

The use of permanent seed implants for the treatment of early stage prostate cancer has become so prevalent in recent years that many people believe this specialized form of low dose rate (LDR) brachytherapy is the only form of brachytherapy.

In this technique, radioactive 'seeds' about the size of a grain of rice are positioned in the prostate using needles that are guided into position by ultrasound and a template or grid through which the needles are inserted to control their spacing.

From 50 to more than 100 individual seeds may be placed in a single session, using 20 to 50 needles. Radiation is then delivered to the prostate slowly over the following month or so as the sources decay.

The challenge is to place the seeds so the radiation dose adequately covers the entire prostate, but spares as much surrounding tissue as possible. To accomplish this task, Varian has developed the VariSeed™ treatment planning system, which uses trans-rectal ultrasound (TRUS) images to help design the intended placement of sources, and then provides ‘dynamic dosimetry' to update the dose map in real time as the individual seeds are deposited in the prostate. This allows the physician to compensate in real time for any gaps that may arise as a result of prostate deformation by the needles, or other needle placement issues that may occur.

VariSeed can also automatically detect seeds from a post implant computed tomography (CT) image set to confirm the received dose distribution.

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Tel: 1.650.424.5700
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