Uncertainty in magnetic resonance imaging-based prostate postimplant dosimetry: Results of a 10-person human observer study, and comparisons with automatic postimplant dosimetry.

PURPOSE: Uncertainties in postimplant quality assessment (QA) for low-dose-rate prostate brachytherapy (LDRPBT) are introduced at two steps: seed localization and contouring. We quantified how interobserver variability (IoV) introduced in both steps impacts dose-volume-histogram (DVH) parameters for MRI-based LDRPBT, and compared it with automatically derived DVH parameters. METHODS AND MATERIALS: Twenty-five patients received MRI-based LDRPBT. Seven clinical observers contoured the prostate and four organs at risk, and 4 dosimetrists performed seed localization, on each MRI. Twenty-eight unique manual postimplant QAs were created for each patient from unique observer pairs. Reference QA and automatic QA were also performed for each patient. IoV of prostate, rectum, and external urinary sphincter (EUS) DVH parameters owing to seed localization and contouring was quantified with coefficients of variation. Automatically derived DVH parameters were compared with those of the reference plans. RESULTS: Coefficients of variation (CoVs) owing to contouring variability (CoVcontours) were significantly higher than those due to seed localization variability (CoVseeds) (median CoVcontours vs. median CoVseeds: prostate D90-15.12% vs. 0.65%, p < 0.001; prostate V100-5.36% vs. 0.37%, p < 0.001; rectum V100-79.23% vs. 8.69%, p < 0.001; EUS V200-107.74% vs. 21.18%, p < 0.001). CoVcontours were lower when the contouring observers were restricted to the 3 radiation oncologists, but were still markedly higher than CoVseeds. Median differences in prostate D90, prostate V100, rectum V100, and EUS V200 between automatically computed and reference dosimetry parameters were 3.16%, 1.63%, -0.00 mL, and -0.00 mL, respectively. CONCLUSIONS: Seed localization introduces substantially less variability in postimplant QA than does contouring for MRI-based LDRPBT. While automatic seed localization may potentially help improve workflow efficiency, it has limited potential for improving the consistency and quality of postimplant dosimetry.

Fully Balanced SSFP Without an Endorectal Coil for Postimplant QA of MRI-Assisted Radiosurgery (MARS) of Prostate Cancer: A Prospective Study.

PURPOSE: To investigate fully balanced steady-state free precession (bSSFP) with optimized acquisition protocols for magnetic resonance imaging (MRI)-based postimplant quality assessment of low-dose-rate (LDR) prostate brachytherapy without an endorectal coil (ERC). METHODS AND MATERIALS: Seventeen patients at a major academic cancer center who underwent MRI-assisted radiosurgery (MARS) LDR prostate cancer brachytherapy were imaged with moderate, high, or very high spatial resolution fully bSSFP MRIs without using an ERC. Between 1 and 3 signal averages (NEX) were acquired with acceleration factors (R) between 1 and 2, with the goal of keeping scan times between 4 and 6 minutes. Acquisitions with R >1 were reconstructed with parallel imaging and compressed sensing (PICS) algorithms. Radioactive seeds were identified by 3 medical dosimetrists. Additionally, some of the MRI techniques were implemented and tested at a community hospital; 3 patients underwent MARS LDR prostate brachytherapy and were imaged without an ERC. RESULTS: Increasing the in-plane spatial resolution mitigated partial volume artifacts and improved overall seed and seed marker visualization at the expense of reduced signal-to-noise ratio (SNR). The reduced SNR as a result of imaging at higher spatial resolution and without an ERC was partially compensated for by the multi-NEX acquisitions enabled by PICS. Resultant image quality was superior to the current clinical standard. All 3 dosimetrists achieved near-perfect precision and recall for seed identification in the 17 patients. The 3 postimplant MRIs acquired at the community hospital were sufficient to identify 208 out of 211 seeds implanted without reference to computed tomography (CT). CONCLUSIONS: Acquiring postimplant prostate brachytherapy MRI without an ERC has several advantages including better patient tolerance, lower costs, higher clinical throughput, and widespread access to precision LDR prostate brachytherapy. This prospective study confirms that the use of an ERC can be circumvented with fully bSSFP and advanced MRI scan techniques in a major academic cancer center and community hospital, potentially enabling postimplant assessment of MARS LDR prostate brachytherapy without CT.

IMRT planning parameter optimization for spine stereotactic radiosurgery.

Spine stereotactic radiosurgery (SSRS) is a noninvasive treatment for metastatic spine lesions. MD Anderson Cancer Center reports a quality assurance (QA) failure rate approaching 15% for SSRS cases, which we hypothesized is due to difficulties in accurately calculating dose resulting from a large number of small-area segments. Clinical plans typically use 9 beams with an average of 10 segments per beam and minimum segment area of 2-3 cm2. The purpose of this study was to identify a set of intensity-modulated radiation therapy (IMRT) planning parameters that attempts to optimize the balance among QA passing rate, plan quality, dose calculation accuracy, and delivery time for SSRS plans. Using Pinnacle version 9.10, we evaluated the effects of 2 IMRT parameters: maximum number of segments and minimum segment area. Initial evaluation of the data revealed that 5 segments per beam along with minimum segment area of 4 cm2 and 4 monitor units (MU) per segment (5-4-4 plans) was the most promising. IMRT QA was performed using a PTW OCTAVIUS 4D phantom with a 2D detector array. Our data showed no significant plan quality change with decreased number of segments and increased minimum segment area. The average coverage of GTV and CTV was 82.5 ± 13% (clinical) vs 82.5 ± 13% (5-4-4) and 92.3 ± 8% (clinical) vs 91.5 ± 8% (5-4-4). Maximum point dose to cord was 11.4 ± 3.5 Gy (clinical) vs 11.0 ± 4.0 Gy (5-4-4). Total plan delivery time was decreased by an average of 11.3% for the 5-4-4 plans. For IMRT QA, the gamma index passing rate (distance to agreement: 2.5 mm, local dose difference: 4%) for the original plans vs the 5-4-4 plans averaged 90.3% and 91.9%, respectively. In conclusion, IMRT parameters of 5 segments per beam and 4 cm2 minimum segment areas provided a better balance of plan quality, delivery efficiency, and plan dose calculation accuracy for SSRS.

IMRT planning parameter optimization for spine stereotactic radiosurgery.

Spine stereotactic radiosurgery (SSRS) is a noninvasive treatment for metastatic spine lesions. MD Anderson Cancer Center reports a quality assurance (QA) failure rate approaching 15% for SSRS cases, which we hypothesized is due to difficulties in accurately calculating dose resulting from a large number of small-area segments. Clinical plans typically use 9 beams with an average of 10 segments per beam and minimum segment area of 2 to 3 cm2. The purpose of this study was to identify a set of intensity-modulated radiation therapy (IMRT) planning parameters that attempts to optimize the balance among QA passing rate, plan quality, dose calculation accuracy, and delivery time for SSRS plans. Using Pinnacle version 9.10, we evaluated the effects of 2 IMRT parameters: maximum number of segments and minimum segment area. Initial evaluation of the data revealed that 5 segments per beam along with minimum segment area of 4 cm2 and 4 minimum Monitor Units (MU) per segment (544 plans) was the most promising. IMRT QA was performed using an OCTAVIUS 4D phantom with a 2D detector array. Our data showed no significant plan quality change with decreased number of segments and increased minimum segment area. The average coverage of GTV and CTV was 82.5 ± 13% (clinical) vs 82.5 ± 13% (544) and 92.3 ± 8% (clinical) vs 91.5 ± 8% (544). Maximum point dose to cord was 11.4 ± 3.5 Gy (clinical) vs 11.0 ± 4.0 Gy (544). Total plan delivery time was decreased by an average of 11.3% for the 544 plans. In addition, the QA passing rate for the original plan vs the 544 plan averaged 90.3% and 91.9%, respectively. In conclusion, IMRT parameters of 5 segments per beam and 4 cm2 minimum segment area provided a better balance of plan quality, delivery efficiency, and plan dose calculation accuracy for SSRS.

Silastic ring vertical gastric bypass: cohort study with 83% rate of 5-year follow-up.

BACKGROUND: Silastic ring vertical gastric bypass (SRVGB) with jejunal interposition is our standard operation for morbidly obese patients. We present the results of 5 years of follow-up in a cohort of patients who underwent SRVGB in 2001. METHODS: The records of all 160 consecutive patients who underwent SRVGB from January to December 2001 were reviewed. Of the 160 procedures, 143 were primary open cases, 14 were revisions from restrictive procedures, and 3 were laparoscopic cases. At 5 years, the body mass index and percentage of excess weight loss was available for 133 patients (83%) at office visits (n = 91, 68.4%), by telephone (n = 40, 30.1%), or by e-mail (n = 2, 1.5%). RESULTS: Of the 160 patients, 121 were women and 39 were men, with a mean age of 33.15 +/- 10.0 years, percentage of ideal body weight of 195.7% +/- 40.8%, and body mass index of 44.6 +/- 9.3 kg/m(2). The mean hospital stay was 3 +/- 1 days. One patient (.6%) died of a pulmonary embolus. Early complications included 3 cases (1.87%) of upper gastrointestinal bleeding and 4 gastric leaks (2.5%): 2 (1.36%) from primary cases and 2 (14.29%) from revisional cases. Late complications included 32 patients (20%) with incisional hernias, 20 (12.5%) with anemia, 14 (8.8%) with dumping, 4 (2.5%) with gastrojejunal stricture, 2 (1.25%) with intestinal obstruction, and 2 (1.25%) requiring silastic ring surgical removal. The 5-year follow-up data were available for 133 patients (83%). The mean body mass index in this group was 27 +/- 5 kg/m(2), with a percentage of excess weight loss of 83% +/- 18.3% at 5 years postoperatively. CONCLUSION: The results of our study have shown that SRVGB is an effective operation for promoting lasting weight loss, with acceptable mortality and complication rates.

Self-expandable metal stents to treat gastric leaks.

OBJECTIVES: Anastomotic leak is a major complication after gastric bypass (GBP) surgery, and it usually necessitates reoperation and is associated with long-term recovery and death. We present our experience with the use of self-expandable metal stents (SEMS) to treat this complication. METHODS: Seventeen patients (14 males and 3 females, mean body mass index of 43.7 kg/m(2)) with gastro-jejunal leak after GBP underwent covered SEMS placement 1 to 3 weeks after surgery: 8 laparoscopic, 5 open, and 4 revisional procedures. All patients who underwent laparoscopic and revisional procedures had abdominal drains placed at surgery. No drains were placed in the open cases. Five patients required surgery to drain an abdominal abscess. RESULTS: Tolerance for oral feeding was achieved between 2 and 3 days after SEMS placement. One patient persisted with a minimal leak for 2 weeks. To date, all stents have been removed endoscopically 3.2 +/- 1.2 months after placement. Four patients needed a second session to complete removal of the uncovered top of the stent. Two esophageal mucosal tears occurred; both were managed conservatively. Sixteen patients had a totally sealed leak. One remained with a gastro-gastric fistula. One stent spontaneously migrated to the splenic flexure and was removed colonoscopically. CONCLUSIONS: SEMS placement for gastro-jejunal leaks is a safe therapeutic option.

Silastic ring vertical gastric bypass: evolution of an open surgical technique, and review of 1,588 cases.

BACKGROUND: Silastic ring vertical gastric bypass (SRVGBP) has evolved from a stapled (SSRVGBP) to a transected (TSRVGBP), and finally to a transected pouch with jejunal interposition (TSRVGBP with J-I). The creation of the gastroenterostomy evolved from a hand-sewn to a stapled and finally to a combined stapled and hand-sewn anastomosis. The circumference of the ring was increased from 5.5 to 6.0 cm. We address the effect of these modifications on surgical outcome. METHOD: The records of 1,588 consecutive patients (mean BMI of 44.5) since 1990 who had a SRVGBP were indentified from a prospective data-base of all patients undergoing bariatric operations. 205 patients with a prior bariatric operation were excluded from the review, leaving 1,383 patients who had a primary SRVGBP. RESULTS: In the 193 SRVGBP patients, there was 1 gastric leak (0.5%) and 64 gastrogastric fistulas (33.2%). In the 165 TSRVGBP patients, there were 4 gastric leaks (2.4%) and 14 gastrogastric fistulas (8.5%). In the 1,025 patients with TSRVGBP with JI, there were 8 gastric leaks (0.8%) and no gastro-gastric fistulas. In the TSRVGBP with J-I, 367 patients had a hand-sewn, 16 a stapled, and 642 a combined stapled and hand-sewn anastomosis. Stricture rate was 3.8%, 31%, and 2.6% respectively. There were 7 ring migrations (0.7%), all in the totally hand-sewn group. Ring removal was necessary in 20 (5%) with a 5.5-cm and 4 (0.74%) with a 6.0-cm ring. CONCLUSION: TSRVGBP with J-I with a combined stapled and hand-sewn gastrojejunal anastomosis using a 6.0-cm ring decreased the incidence of complications, and is our current technique.

Resultados de la gastroplástia vertical en setenta y siete pacientes operados por obesidad grave / Results of the vertical gastroplasty in 77 operatory patients for severe obesity

Los pacientes con Obesidad Grave (excesos del 100% o cuando menos 45 Kgs. sobre el peso ideal), tienen 12 veces menos expectativas de vida que la población normal. El persistente fracaso de los tratamientos médicos y dietéticos ha conducido a la búsqueda de soluciones quirúrgicas. Desde Noviembre de 1985 hasta el presente, practicamos la GASTROPLASTIA VERTICAL en 77 casos. Esta intervención consiste en la construcción de un reservorio Gástrico de una capacidad no mayor de 40 cc. Las indicaciones fueron las de ser portadores de una Obesidad Grave por un período mínimo de 5 años y haber agotado todas las otras alternativas de tratamiento médico dietético. Se practicaron exámenes de laboratorio, endocrinológicos, evaluaciones Cardio-pulmonares, Digestivas y Psiquiátricas. La edad promedio fue 34 años con un rango de 16 a 60 años, 55 hembras y 22 varones. El peso promedio fue 122 kilogramos (195% de peso Corporal Ideal) con un rango de 90 a 281 Kg. Practicamos 23 procedimientos quirúrgicos asociados, siendo la Colecistectomía la más frecuente, en 14 casos. No se produjo ninguna muerte. Las complicaciones mayores fueron 2 perforaciones gástricas, 2 Fístula Esofágica, 1 Tromboembolismo Pulmonar y 1 Evisceración, morbilidad que correspondió al 6,5%. Hubo seguimiento del 95% a los 6 meses, 75% al año y 65% a los 2 años. Durante el primer trimestre perdieron el 40% del exceso Pre-Operatorio, el 54% al segundo trimestre, 70% y 75% a los doce meses y 18 meses respectivamente, aproximándose a sus pesos ideales a los dos años. Los parámetros nutricionales fueron normales, salvo en dos pacientes que desarrollaron anemia..