A MODIFIED TECHNIQUE ALLOWING INTERACTIVE ULTRASOUND-GUIDED 3-DIMENSIONAL TRANSPERINEAL PROSTATE IMPLANTATION

Purpose: Ultrasound-guided transperineal prostate implantation is a ne w technique for performing permanent isotope implants of the prostate, The details of the technique are presented to demonstrate its ability to place radioactive seeds three-dimensionally within the prostate gl and to achieve uniform dose distribution without the need for complica ted preplanning. Methods and Materials: An accurate measurement of the prostate volume is made using biplanar transrectal ultrasound, The to tal activity to be implanted is derived from a look-up table based on prostate volume, The basic plan is to implant 60-70% of the total acti vity in the periphery of the gland and the remaining activity in the i nterior of the gland, The ultrasound transducer provides visualization of the prostate through transverse, longitudinal and oblique cuts and allows for accurate placement of implant needles, approximately 1 cm apart, In addition, these needles can be moved through the prostate un der constant visualization, thus allowing for precise seed placement. Results: The setup of the transrectal ultrasound device as well as pro state volume measurements are performed in 10 to 15 min, The actual pl acement of the needles and seed implantation takes 1 to 1.5 h to perfo rm, Postimplantation dosimetric evaluation is performed using orthogon al x-ray films and 3 mm thick CT slices taken at 3 mm intervals, This evaluation has confirmed accurate seed placement within the prostate g land. Conclusion: Interactive ultrasound guided transperineal prostate implantation is a fast and accurate method of performing permanent ra dioactive isotope prostate implants.