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Single planar 'interstitial implants aim to irradiate 10 mm thickness of tissue to uniform dose.
Interstitial iridium implants are normally practised with the same linear activity throughout the implant. As a result, the peripheral regions of the implant get lesser dose contribution from the central wires. Out study with the Planning System for a 5 x 4 cm2 area of parallel implant geometry shows that the peripheral regions receive only 83% of the prescribed dose and the minimum treated thickness is 7.6 mm only. increasing either the activity or time weight to the peripheral wires by 25% enables the peripheral regions to receive a minimum of 92% of the prescribed dose and the minimum treated thickness increases to 8.80 mm. The removal time of peripheral wires with time weight option can be calculated manually by a simple formula.
