Robotic-assisted cystogastrostomy for a patient with a pancreatic pseudocyst.

Pancreatic pseudocysts are generally treated by endoscopic cystogastrostomy. However, difficult cases involving abscess, necrosis, or risk of hemorrhage often require surgical intervention. Here, we report a case of a robotically assisted cystogastrostomy. The patient presented with an infected pseudocyst with adjacent varices. Use of the da Vinci Surgical System allowed us to create a widely patent anastomosis between the pseudocyst and the stomach. The patient tolerated the procedure well without any complications. This report demonstrates the feasibility of robotic cystogastrostomy.

Correlation of gross tumor volume excursion with potential benefits of respiratory gating.

PURPOSE: To test the hypothesis that the magnitude of thoracic tumor motion can be used to determine the desirability of respiratory gating. METHODS AND MATERIALS: Twenty patients to be treated for lung tumors had computed tomography image data sets acquired under assisted breath hold at normal inspiration (100% tidal volume), at full expiration (0% tidal volume), and under free breathing. A radiation oncologist outlined gross tumor volumes (GTVs) on the breath-hold computed tomographic images. These data sets were registered to the free-breathing image data set. Two sets of treatment plans were generated: one based on an internal target volume explicitly formed from assessment of the excursion of the clinical target volume (CTV) through the respiratory cycle, representing an ungated treatment, and the other based on the 0% tidal volume CTV, representing a gated treatment with little margin for residual motion. Dose-volume statistics were correlated to the magnitude of the motion of the center of the GTV during respiration. RESULTS: Patients whose GTVs were >100 cm(3) showed little decrease in lung dose under gating. The other patients showed a correlation between the excursion of the center of the GTV and a reduction in potential lung toxicity. As residual motion increased, the benefits of respiratory gating increased. CONCLUSION: Gating seems to be advantageous for patients whose GTVs are <100 cm(3) and for whom the center of the GTV exhibits significant motion, provided residual motion under gating is kept small.

Quality assurance evaluation of delivery of respiratory-gated treatments.

We describe a method for evaluating the quality of respiratory-gated radiation delivery using a commercially available device. During irradiation, gating traces for one field for each treatment were extracted from the system for each of 14 patients. The data were then transferred to a spreadsheet. Software was developed to evaluate the following parameters: duty cycle, amplitude of fiducial motion, fraction of amplitude of motion during gated delivery, and respiratory cycle time. Criteria were established for acceptability of gating traces. In our sample, over 85% of the traces indicated acceptability. An example of results for one patient extracted from analyzed gating traces is as follows: mean duty cycle, 57%, average amplitude of motion, 0.89 cm, average fraction of motion during gated delivery, 0.45; mean respiratory cycle time, 4.5 s. This technique can be used to evaluate delivery of respiratory-gated radiation therapy for quality assurance purposes and to assess various techniques for improving delivery of gated therapy. A hardcopy of the gating traces can be used to document gated treatment delivery for potential billing of the gated delivery process.