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Intercomparison of stranded seeds and loose seed from seedselectron
Abstracts / Brachytherapy 7 (2008) 91e194 Results: The procedures were performed in 10 patients and all patients have been successfully implanted. Our sequences allowed clear definition of the prostate, urethra, periprostatic tissues as well as the coaxial needles and brachytherapy catheters in all cases. No serious intervention related adverse events and no Common Toxicity Criteria Grade 3 or worse acute toxicities were observed. 88e100% of the target volumes received the prescribed dose and D0.1 cc for the urethra and the anterior rectal wall were consistently under 125% and 85%. The average difference between the calculated and measured doses at the different levels of the rectal detectors was !5%. The procedure times ranged from 5e7 hours. Conclusions: Based on our initial experiences our method seems to be a promising approach for performing feasible, accurate, reliable and highquality prostate MR guidance within a reasonable time span. Although the acute toxicity was minimal, higher number of patients, additional followup is required to determine the long side effects and efficacy. MR modeling of the rectal dosimeter is a promising device to provide a more accurate prediction about the rectal doses. Our preliminary results facilitate us to initiate fractionated boost in the near future. PO119 Novel catheter patterns for HDR prostate brachytherapy J. Adam M Cunha, Ph.D., I.-Chow Hsu, M.D., Jean Pouliot, Ph.D. Radiation Oncology, University of California (UCSF), San Francisco, CA. Purpose: To determine whether alternative prostate brachytherapy needle patterns can result in similar or improved dose distributions while providing better access and reducing trauma in the treatment of HDR prostate brachytherapy. Methods and Materials: HDR brachytherapy for prostate cancer uses a regular grid of parallel needle positions to guide the insertion of the catheters into the prostate. This geometry does not easily allow the physician to avoid piercing the penile bulb nor does it provide position flexibility in the case of pubic arch interference. In this study, CT data sets from 10 patients previously treated with HDR prostate brachytherapy were used and catheters were digitized by following three novel hypothetical catheter patterns: Conical, bi-conical, and firework. The conical patterns were used to accommodate an eventual robotic delivery using a single entry point. The bi-conical and firework patterns were specifically designed to avoid the bulb. For each catheter distribution, a plan was optimized with the inverse planning algorithm, IPSA, and compared with the plan used for treatment. Irrelevant of the geometry, a plan must fulfill the RTOG 0321 dose criteria for target dose coverage (V100O90%) and organ-at-risk dose sparing (V75!1 cc for the bladder and rectum, V125!!1 cc for the urethra). Results: The three non-standard catheter patterns used 16 non-parallel, straight divergent catheters, with the focal point(s) in the posterior area of the perineum. 30 plans from 10 patients with prostate sizes ranging from 26 to 89 cc were optimized. All non-standard patterns could fulfill the RTOG criteria when the clinical plan did. In addition a homogeneity index of more than 60% was achieved for all plans. In some cases, the dose distribution was improved by better sparing the organs at risk. Even for large contoured bulbs, the bulb-sparing patterns could be used. Conclusions: Alternative needle patterns can provide the physician with additional ways to treat patients previously considered unsuited for brachytherapy treatment (pubic arch interference) and to improve patient quality of life (avoidance of penile bulb), while fulfilling the RTOG criteria. This study is being extended to permanent prostate implant. This work is supported by Nucletron B.V., Veenendaal, Netherlands. PO120 Intercomparison of stranded seeds and loose seed from seedselectron Jan J. Battermann, M.D., Ph.D., Marco Van Vulpen, M.D., Ph.D., Marinus A. Moerland, Ph.D., Marijke Van Deursen, M.Sc., Ina Jurgenliemk-Schulz, M.D., Ph.D. Radiation-Oncology, University Medical Center, Utrecht, Utrecht, Netherlands. Purpose: To evaluate the differences of stranded seeds and loose seeds using the FIRST system for the definitive treatment of localized prostate cancer.
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Methods and Materials: Patients treated in the period January 2002 through September 2007 were evaluated for intercomparison of tumor characteristics, implant characteristics and side effects. In total 1023 were recorded, 47 patients were excluded for previous radiotherapy on the true pelvis (11), previous TURP (31), and patients with a half/half combination of strands and loose seeds (5). Patients were randomly chosen for treatment with FIRST (443) or with stranded seeds (523). Patient characteristics (age and symptoms) are identical for both techniques, as well as for tumor characteristics (T stage, Gleason sum, bilateral tumor, iPSA, risk group, prostate volume and hormonal pretreatment to downsize the prostate volume). Results: Prostate volumes (mean 34.5 and 35.8 cc) and number of needles (mean 24 and 24.7) were similar, while the number of seeds was somewhat larger with loose seeds (mean 71 and 75). In total 36,953 stranded seeds and 33,025 Selectseeds were used. The number of loose spacers in the FIRST system was approx. the same as the number of active seeds. Total implantation time was not different between both groups (average 1.5 hour). The number of seeds that disappeared was 172 for strands and 82 for FIRST, but migration within the body was higher with FIRST (61 vs. 5). Note that migration of spacers within the body cannot be detected. Toxicity was low and similar for both techniques, regarding voiding and rectal complaints. Acute retention was found in 24 FIRST patients (5.4%) and 33 strand patients (6.3%). Urinary symptoms more than 6 months were noticed in 6.1% (strands) and 9.4% (First). Infection was found in 2 strand patients and 4 First patients. Erectile dysfunction was found in 32% after FIRST and 28% after strands, but not assessed in about 50% of patients. One of the strand patients died of prostate cancer; intercurrent death was encountered in 7 FIRST and 11 strand patients and not related to brachytherapy. Secondary tumors were found in 7 strand and 5 First patients, the majority (8) within 2 years, with 4 bronchus carcinomas, but not related to migration of seeds to the lungs. Three appeared in the recto-sigmoid, at an interval of 3, 44 and 56 months. Conclusions: From the presented data we cannot favour one of the techniques. There is a higher incidence of migration with loose seeds as used in the FIRST system, but no detrimental effect was observed from this. The use of polylactide loose spacers in FIRST did not result in detectable adverse effects; neither did the polyglactin wires in the stranded patients.
PO121 MRI-compatible pneumatic robot (MRBot) for prostate brachytherapy: Preclinical evaluation of feasibility and accuracy Danny Y. Song, M.D.1 Doru Petrisor, Ph.D.2 Michael Muntener, M.D.2 Pierre Mozer, M.D., Ph.D.2 Bogdan Vigaru2 Alex Patriciu, Ph.D.2 Michael Schar, Ph.D.2 Dan Stoianovici, Ph.D.2 1Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, MD; 2URobotics, Brady Urological Institute, Johns Hopkins University School of Medicine, Baltimore, MD. Purpose: MRI offers potential advantages over other imaging modalities for prostate brachytherapy due to its superior anatomic and tumor detail, capability for intraoperative dosimetric feedback, and potential for molecular imaging. However, manual placement of intraprostatic sources in an MR scanner presents logistical and workflow challenges. We tested the preclinical feasibility and accuracy testing of an interventional robot (MRBot) which has the capability for automated precise delivery of radioactive sources. The robot is fully MR compatible, relying on a system of specifically engineered pneumatic motors with optical sensors, and drives a brachytherapy source delivery needle. Methods and Materials: The MRBot is fixed onto a standard MR couch with adjustable, powered suction cups. Spatial calibration to the MR is achieved using a gadolinium-containing fiducial encasing the needle hub. Needle penetration and source delivery are automated and controlled remotely. Tissue mockups of sausage embedded in clear gel were implanted with a total of 125 seeds, and CT images obtained with slice thickness 0.75 mm. Seeds were identified and the norm of the error vector (desired vs deployed position) recorded for each seed. Animal experiments were conducted on 4 anesthetized adult male dogs. A total of 18 dummy seeds were implanted under MR guidance in a 3T
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Methods and Materials: Patients treated in the period January 2002 through September 2007 were evaluated for intercomparison of tumor characteristics, implant characteristics and side effects. In total 1023 were recorded, 47 patients were excluded for previous radiotherapy on the true pelvis (11), previous TURP (31), and patients with a half/half combination of strands and loose seeds (5). Patients were randomly chosen for treatment with FIRST (443) or with stranded seeds (523). Patient characteristics (age and symptoms) are identical for both techniques, as well as for tumor characteristics (T stage, Gleason sum, bilateral tumor, iPSA, risk group, prostate volume and hormonal pretreatment to downsize the prostate volume). Results: Prostate volumes (mean 34.5 and 35.8 cc) and number of needles (mean 24 and 24.7) were similar, while the number of seeds was somewhat larger with loose seeds (mean 71 and 75). In total 36,953 stranded seeds and 33,025 Selectseeds were used. The number of loose spacers in the FIRST system was approx. the same as the number of active seeds. Total implantation time was not different between both groups (average 1.5 hour). The number of seeds that disappeared was 172 for strands and 82 for FIRST, but migration within the body was higher with FIRST (61 vs. 5). Note that migration of spacers within the body cannot be detected. Toxicity was low and similar for both techniques, regarding voiding and rectal complaints. Acute retention was found in 24 FIRST patients (5.4%) and 33 strand patients (6.3%). Urinary symptoms more than 6 months were noticed in 6.1% (strands) and 9.4% (First). Infection was found in 2 strand patients and 4 First patients. Erectile dysfunction was found in 32% after FIRST and 28% after strands, but not assessed in about 50% of patients. One of the strand patients died of prostate cancer; intercurrent death was encountered in 7 FIRST and 11 strand patients and not related to brachytherapy. Secondary tumors were found in 7 strand and 5 First patients, the majority (8) within 2 years, with 4 bronchus carcinomas, but not related to migration of seeds to the lungs. Three appeared in the recto-sigmoid, at an interval of 3, 44 and 56 months. Conclusions: From the presented data we cannot favour one of the techniques. There is a higher incidence of migration with loose seeds as used in the FIRST system, but no detrimental effect was observed from this. The use of polylactide loose spacers in FIRST did not result in detectable adverse effects; neither did the polyglactin wires in the stranded patients.
PO121 MRI-compatible pneumatic robot (MRBot) for prostate brachytherapy: Preclinical evaluation of feasibility and accuracy Danny Y. Song, M.D.1 Doru Petrisor, Ph.D.2 Michael Muntener, M.D.2 Pierre Mozer, M.D., Ph.D.2 Bogdan Vigaru2 Alex Patriciu, Ph.D.2 Michael Schar, Ph.D.2 Dan Stoianovici, Ph.D.2 1Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, MD; 2URobotics, Brady Urological Institute, Johns Hopkins University School of Medicine, Baltimore, MD. Purpose: MRI offers potential advantages over other imaging modalities for prostate brachytherapy due to its superior anatomic and tumor detail, capability for intraoperative dosimetric feedback, and potential for molecular imaging. However, manual placement of intraprostatic sources in an MR scanner presents logistical and workflow challenges. We tested the preclinical feasibility and accuracy testing of an interventional robot (MRBot) which has the capability for automated precise delivery of radioactive sources. The robot is fully MR compatible, relying on a system of specifically engineered pneumatic motors with optical sensors, and drives a brachytherapy source delivery needle. Methods and Materials: The MRBot is fixed onto a standard MR couch with adjustable, powered suction cups. Spatial calibration to the MR is achieved using a gadolinium-containing fiducial encasing the needle hub. Needle penetration and source delivery are automated and controlled remotely. Tissue mockups of sausage embedded in clear gel were implanted with a total of 125 seeds, and CT images obtained with slice thickness 0.75 mm. Seeds were identified and the norm of the error vector (desired vs deployed position) recorded for each seed. Animal experiments were conducted on 4 anesthetized adult male dogs. A total of 18 dummy seeds were implanted under MR guidance in a 3T