Alignment of seed order to prostate shape

4. Alignment of seed order to prostate shape

• In the transverse view on the planning computer, using the uploaded needle and seed order, identify the largest prostate image, (maximum perimeter), and move the needle positions so they are spaced evenly around the perimeter. Keep the approximate configuration of four needles across both the anterior (top) and posterior (bottom) portion of the gland. The central loose needles are then spaced in the standard fashion within the centre of the gland.
• Review the calculated dosimetry ensuring the isodose curves cover the entire gland and adjust the needle positions as required. If the predicted dose to the prostate is too high despite adjusting the number of central sources, remove 2 lateral or one posterior peripheral stranded needles. Do not implant any seeds until a satisfactory dosimetry is obtained.
• The needle positions are then transferred from the planning computer to the ultrasound screen. (Technical Note: Positioning the stranded needles: If the perimeter of the prostate is larger than expected and it is difficult to cover the prostate outer edge of the gland with the 100% isodose, move the posterior needles such that a wider than usual space is created between the middle two needles. In doing this the rest of the needles can be better spaced around the perimeter to optimise the 100% isodose coverage. The “cold” under dosed area posteriorly that is created can be managed by using an extra central needle to ensure the dosimetry is optimised.)