No abstract

Twenty-four beagles received intraoperative irradiation (IORT) with 6 meV electrons to the pancreas and the duodenum. Intraoperative irradiation doses of 17.5 to 40 Gy were given. Billroth I1 gastrojejunostomy was done to bypass the irradiated duodenum. Six control dogs received only the Billroth I1 surgery. Two weeks postoperatively, irradiated dogs were given 50 Gy of 6 MV X radiation (externalbeam radiation [EBRTJ) to the pancreas and duodenum in 2 Gy fractions over a 5-week period. Dogs were monitored clinically and exocrine pancreatic function was evaluated using an N-benzoyl-l-tyrosylpara-aminobenzoic acid (BT-PABA) test between 3 and 135 days postoperatively. Necropsies were performed on the dogs at 135 days postoperatively. The degree of gross pancreatic atrophy in the irradiated group was dose related. The mean percentage of normal acinar cells correlated with IORT doses and para-aminobenzoic acid (PABA) values (P < 0.1). Weight loss was significantly greater in the irradiated dogs compared to the control (P < 0.05) and the mean percentage of body weight loss correlated with the mean PABA values (P < 0.01). In this study, the use of the BT-PABA test to evaluate progressive exocrine pancreatic function following IORT and EBRT showed an expected trend. A progressive decrease in exocrine pancreatic function in the irradiated dogs as indicated by plasma PABA levels may have been partly due to late radiation damage to acinar cells, secondary to vascular and ductular damage. At 135 days postoperatively none of the dogs showed clinical signs of exocrine pancreatic insufficiency and the plasma PABA levels were within the normal presurgical range. The progressive decrease in plasma PABA levels indicated a potential for the late development of exocrine pancreatic insufficiency. The BT-PABA test could be useful for evaluating the progressive decrease in exocrine pancreatic function and residual radiation injury to the pancreas. Because the exocrine deficiency can be managed with replacement therapy, pancreatic injury may not be a serious complication after doses of less than 30 Gy IORT with 50 Gy EBRT. Data from this study are in agreement with previous clinical and experimental reports that the duodenum is dose-limiting for IORT. Doses of 20 Gy IORT or less plus 50 Gy EBRT for treatment of carcinoma of the pancreas may not result in serious long-term complications due to radiation injury of the duodenum.Cancer 62:1091-1095, 1988.NTRAOPERATIVE RADIOTHERAPY (IORT) for pancre-I atic adenocarcinoma is considered to be one of the most promising treatment modalities for this fatal disReports from several centers have indicated that the use of IORT for pancreatic adenocarcinoma increased the median survival time of patients as well as alleviated pain associated with this disease. The duodenum is considered to be dose-limiting in IORT for pancreatic adenocar~inoma.~ Intraoperative radiotherapy doses in excess of 20 Gy resulted in duodenal ~lceration.~ Duodenal fibroses and stenosis commonly occurred after IORT and for th...

Purpose: Prostate MRI plays an important role in diagnosis, biopsy guidance, and therapy planning for prostate cancer. Prostate MRI contours can be used to aid in image fusion for ultrasound biopsy guidance and delivery of radiation. Our goal in this study is to evaluate an automatic atlas‐based segmentation method for generating prostate and peripheral zone (PZ) contours on MRI. Methods: T2‐weighted MRIs were acquired on 3T‐Discovery MR750 System (GE, Milwaukee). The Volumes of Interest (VOIs): prostate and PZ were outlined by an expert radiation oncologist and used to create an atlas library for atlas‐based segmentation. The atlas‐segmentation accuracy was evaluated using a leave‐one‐out analysis. The method involved automatically finding the atlas subject that best matched the test subject followed by a normalized intensity‐based free‐form deformable registration of the atlas subject to the test subject. The prostate and PZ contours were transformed to the test subject using the same deformation. For each test subject the three best matches were used and the final contour was combined using Majority Vote. The atlas‐segmentation process was fully automatic. Dice similarity coefficients (DSC) and mean Hausdorff values were used for comparison. Results: VOIs contours were available for 28 subjects. For the prostate, the atlas‐based segmentation method resulted in an average DSC of 0.88+/−0.08 and a mean Hausdorff distance of 1.1+/−0.9mm. The number of patients (#) in DSC ranges are as follows: 0.60–0.69(1), 0.70–0.79(2), 0.80–0.89(13), >0.89(11). For the PZ, the average DSC was 0.72+/−0.17 and average Hausdorff of 0.9+/−0.9mm. The number of patients (#) in DSC ranges are as follows: <0.60(4), 0.60–0.69(6), 0.70–0.79(7), 0.80–0.89(9), >0.89(1). Conclusion: The MRI atlas‐based segmentation method achieved good results for both the whole prostate and PZ compared to expert defined VOIs. The technique is fast, fully automatic, and has the potential to provide significant time savings for prostate VOI definition. AS Nelson and J Piper are partial owners of MIM Software, Inc. AS Nelson, J Piper, K Curry, and A Swallen are current employees at MIM Software, Inc.

Purpose: Deformable registration algorithms are inherently difficult to characterize in the multi‐modality setting due to a significant differences in the characteristics of the different modalities (CT and MRI) as well as tissue deformations. We present a unique paradigm where this is overcome by utilizing a planning‐MRI acquired within an hour of the planning‐CT serving as a surrogate for quantifying MRI to CT deformation by eliminating the issues of multi‐modality comparisons. Methods: For nine subjects, T2 fast‐spin‐echo images were acquired at two different time points, the first several weeks prior to planning (diagnostic‐MRI) and the second on the same day as the planning‐CT (planning‐MRI). Significant effort in patient positioning and bowel/bladder preparation was undertaken to minimize distortion of the prostate in all datasets. The diagnostic‐MRI was rigidly and deformably aligned to the planning‐CT utilizing a commercially available deformable registration algorithm synthesized from local registrations. Additionally, the quality of rigid alignment was ranked by an imaging physicist. The distances between corresponding anatomical landmarks on rigid and deformed registrations (diagnostic‐MR to planning‐CT) were evaluated. Results: It was discovered that in cases where the rigid registration was of acceptable quality the deformable registration didn't improve the alignment, this was true of all metrics employed. If the analysis is separated into cases where the rigid alignment was ranked as unacceptable the deformable registration significantly improved the alignment, 4.62mm residual error in landmarks as compared to 5.72mm residual error in rigid alignments with a p‐value of 0.0008. Conclusion: This paradigm provides an ideal testing ground for MR to CT deformable registration algorithms by allowing for inter‐modality comparisons of multi‐modality registrations. Consistent positioning, bowel and bladder preparation may Result in higher quality rigid registrations than typically achieved which limits the impact of deformable registrations. In this study cases where significant differences exist, deformable registrations provide significant value. This work was funded by an NIH grant# 1R01CA189295‐01. PI: Alan Pollack, MD PhD. “MRI IMAGING AND GENETIC SIGNATURES TO MANAGE PROSTATE CANCER OVERDIAGNOSIS”