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Background and purpose In permanent prostate brachytherapy the dose distributions 4 weeks post implant differ from the intraoperative dose distributions. The purpose of this study is to compare intraoperative planning and post implant dosimetry for loose and stranded seed implants. Materials and methods This study investigates prostate dose coverage in 389 patients with stage T1 or T2 prostate cancer treated in the years 2005, 2006 and 2007. The patients received either a loose seed or a stranded seed implant. All patients had US-based intraoperative planning and CT/MRI-based post implant dosimetry after 4 weeks. Results Intraoperative and post implant D 90 values amounted 183±13Gy (mean±standard deviation) and 161±30Gy, respectively. Decline of D 90 values (mean and 95% confidence interval) between intraoperative planning and post implant dosimetry for RAPID strand ( n =67), Intersource strand ( n =136) and loose selectSeeds ( n =186) implants amounted to −40 (−45 to −34)Gy, −25 (−28 to −21)Gy and −15 (−18 to −21)Gy, respectively. Conclusions The patients treated in the period 2005–2007 with stranded or loose seed implants had on average adequate D 90 values of 161±30Gy. Post implant D 90 values were 22±27Gy lower compared to intraoperative planning. Decline of dose coverage between intraoperative planning and post implant dosimetry was significantly larger for the stranded seed implants.

To compare the dosimetric results between MRI-based and TRUS-based preplanning in permanent prostate brachytherapy, and to estimate the accuracy of MRI-based preplanning by comparing with CT/MRI fusion-based postimplant dosimetry., Twenty-one patients were entered in this prospective study with written informed consent. MRI-based and TRUS-based preplanning were performed. The seed and needle locations were identical according to MRI-based and TRUS-based preplanning. MRI-based and TRUS-based preplanning were compared using DVH-related parameters. Following brachytherapy, the accuracy of the MRI-based preplanning was evaluated by comparing it with CT/MRI fusion-based postimplant dosimetry., Mean MRI-based prostate volume was slightly underestimated (0.73 cc in mean volume) in comparison to TRUS-based volume. There were no significant differences in the mean DVH-related parameters except with rectal V(100)(cc) between TRUS-based and MRI-based preplanning. Mean rectal V(100)(cc) was 0.74 cc in TRUS-based and 0.29 cc in MRI-based preplanning, respectively, and the values demonstrated a statistical difference. There was no statistical difference in mean rectal V(150)(cc), and rectal V(100)(cc) between MRI-based preplanning and CT/MRI fusion-based postimplant dosimetry., Prostate volume estimation and DVH-related parameters in MRI-based preplanning were almost identical to TRUS-based preplanning. From the results of CT/MRI fusion-based postimplant dosimetry, MRI-based preplanning was therefore found to be a reliable and useful modality, as well as being helpful for TRUS-based preplanning. MRI-based preplanning can more accurately predict postimplant rectal dose than TRUS-based preplanning.

Background and purpose The purpose of this study is to investigate the feasibility of adequate dose coverage in permanent prostate brachytherapy using divergent needle insertion methods. These methods can be useful in magnetic resonance imaging (MRI) guided needle insertion techniques to avoid pubic arch interference. Methods and materials MRI data were collected from 10 patients with T1–T2 prostate cancer. An inverse planning algorithm based on simulated annealing was used to optimize the dose distribution for three needle insertion methods: divergent needles with a single rotation point, divergent needles with a double rotation point, and current parallel needle insertion method. The dose constraints were based on our clinical criteria and the recent ESTRO/EAU/EORTC recommendations. Results If the planning target volume (PTV) surrounded the prostate and only intraprostatic seeds were allowed, the mean PTV volume that received 100% of the prescribed dose ( V 100 ) was 99% for all needle insertion methods. If the PTV was increased to the prostate with a 3mm margin, the mean PTV V 100 equalled 94%, 95%, and 94% for the single rotation point, double rotation point and current parallel needle insertion method, respectively. If in the latter case the tips of the seeds were placed 3mm outside the apex and base of the prostate, the mean PTV V 100 was 96% for all needle insertion methods. Conclusion This planning study shows that it is feasible to generate an adequate dose coverage using divergent needle insertion methods.

The aim of the study was to analyze source displacements and dose-volume changes in the first month after a permanent implant.In 51 consecutive patients, CT scans were performed at the postoperative day (day 1) and one month (day 30) after an (125)I implant with stranded seeds. Seed positions were determined relative to pelvic bones for five seeds at the base and five seeds at the apex for each patient (n=510) and compared. To verify these results, treatment margins (TM=distance of prescription isodose to prostate) and displacements of the prostate surface (anterior/posterior/right/left/superior/inferior) relative to pelvic bones were measured.Seed positions have moved significantly between day 1 and 30 in the posterior (mean 1.0mm; p0.001) and inferior (mean 3.8mm; p0.001) directions. TM increased particularly at the posterior (mean 2.2mm; p0.001) and apical (median 3.0mm; p0.001) prostate contour with decreasing oedema. With a stable apex position and a mean inward posterior surface displacement of 1.1mm (p0.001) relative to pelvic bones, seed displacements could be well correlated with prescription isodose displacements (Pearson correlation coefficientsor=0.81; p0.001).Both changes of prostate volume and seed displacements need to be considered to explain dosimetric changes after permanent prostate brachytherapy.