We propose a new computational method for predicting rotational diffusion properties of proteins in solution. The method is based on the idea of representing protein surface as an ellipsoid shell. In contrast to other existing approaches this method uses principal component analysis of protein surface coordinates, which results in a substantial increase in the computational efficiency of the method. Direct comparison with the experimental data as well as with the recent computational approach (Garcia de la Torre; et al. J. Magn. Reson. 2000, B147, 138-146), based on representation of protein surface as a set of small spherical friction elements, shows that the method proposed here reproduces experimental data with at least the same level of accuracy and precision as the other approach, while being approximately 500 times faster. Using the new method we investigated the effect of hydration layer and protein surface topography on the rotational diffusion properties of a protein. We found that a hydration layer constructed of approximately one monolayer of water molecules smoothens the protein surface and effectively doubles the overall tumbling time. We also calculated the rotational diffusion tensors for a set of 841 protein structures representing the known protein folds. Our analysis suggests that an anisotropic rotational diffusion model is generally required for NMR relaxation data analysis in single-domain proteins, and that the axially symmetric model could be sufficient for these purposes in approximately half of the proteins.

PurposeThe goal of this study was to evaluate the use of 3D ultrasound (3DUS) breast IGRT for electron and photon lumpectomy site boost treatments.Materials and methods20 patients with a prescribed photon or electron boost were enrolled in this study. 3DUS images were acquired both at time of simulation, to form a coregistered CT/3DUS dataset, and at the time of daily treatment delivery. Intrafractional motion between treatment and simulation 3DUS datasets were calculated to determine IGRT shifts. Photon shifts were evaluated isocentrically, while electron shifts were evaluated in the beam's-eye-view. Volume differences between simulation and first boost fraction were calculated. Further, to control for the effect of change in seroma/cavity volume due to time lapse between the 2 sets of images, interfraction IGRT shifts using the first boost fraction as reference for all subsequent treatment fractions were also calculated.ResultsFor photon boosts, IGRT shifts were 1.1 ± 0.5 cm and 50% of fractions required a shift >1.0 cm. Volume change between simulation and boost was 49 ± 31%. Shifts when using the first boost fraction as reference were 0.8 ± 0.4 cm and 24% required a shift >1.0 cm. For electron boosts, shifts were 1.0 ± 0.5 cm and 52% fell outside the dosimetric penumbra. Interfraction analysis relative to the first fraction noted the shifts to be 0.8 ± 0.4 cm and 36% fell outside the penumbra.ConclusionThe lumpectomy cavity can shift significantly during fractionated radiation therapy. 3DUS can be used to image the cavity and correct for interfractional motion. Further studies to better define the protocol for clinical application of IGRT in breast cancer is needed.

Purpose: The project intent is to transit from frame based SRS to frameless SRS procedure and workflow in a community hospital setting. Methods: The clinic has strong experience in a wide verity of frame based SRS procedures using Novalis 600N linac equipped with BrainLab Micro‐MLC and ExacTrac systems. The addition of new Novalis TX system has opened an opportunity to explore and implement frameless SRS treatment procedure. Phantom End to End studies were performed for this purpose. A calibrated Ionization Chamber was inserted into the phantom and the phantom was positioned on the CT scan couch and SRS immobilization mask was made. A CT scan of the Immobilized phantom was generated with the localization box in place. The CT scan was localized and the ionization Chamber active volume was contoured as a target on the IPlan planning system. A 5 Dynamic Conformal Arcs plan was generated on the Iplan planning system. The Phantom was positioned on the treatment Couch with the SRS Mask and frameless array system in place, and the initial target treatment ISO position was achieved. The chamber was then connected to an electrometer. The two Orthogonal KV images were taken and the final treatment position was achieved within 1mm and 1 degree using ExacTrac. The Five arcs were delivered and the electrometer reading was noted. In addition, RPC SRS head phantom study was performed following RPC procedure. Results: The average absolute dose delivered to the in‐house phantom target was in agreement within 1.5% of the planning dose. The RPC SRS phantom results were within the criteria set by RPC. Conclusion: This work gave the confidence to our clinic to move from invasive frame based to non invasive and efficient frameless SRS and SRT treatments. The clinic has now frameless SRS and SRT treatment procedures and workflow.

Purpose: To transition from an in‐house incident reporting system to a ROILS standards system with the intent to develop a safety focused culture in the Department and enroll in ROILS. Methods: Since the AAPM Safety Summit (2010) several safety and reporting systems have been implemented within the Department. Specific checklists and SBAR reporting systems were introduced. However, the active learning component was lost due to reporting being viewed with distrust and possible retribution.To Facilitate introducing ROILS each leader in the Department received a copy of the ROILS participation guide. Four specific tasks were assigned to each leader: develop a reporting tree, begin the ROILS based system, facilitate adopting ROILS Terminology, and educate the staff on expectations of safety culture. Next, the ROILS questions were broken down into area specific questions (10–15) per departmental area. Excel spreadsheets were developed for each area and setup for error reporting entries. The Role of the Process Improvement Committee (PI) has been modified to review and make recommendations based on the ROILS entries. Results: The ROILS based Reporting has been in place for 4 months. To date 64 reports have been entered. Since the adoption of ROILS the reporting of incidents has increased from 2/month to 18/month on average. Three reports had a dosimetric effect on the patient (<5%) dose variance. The large majority of entries have been Characterized as Processes not followed or not sure how to Characterize, and Human Behavior. Conclusion: The majority of errors are typo's that create confusion. The introduction of the ROILS standards has provided a platform for making changes to policies that increase patient safety. The goal is to develop a culture that sees reporting at a national level as a safe and effective way to improve our safety, and to dynamically learn from other institutions reporting.

Conclusion: Using MRI as a primary image set to define a pancreatic adenocarcinoma GTV resulted in volumetrically smaller contours and a reduced standard deviation as compared with CT. No differences in DSC or the CI were seen between MR and CT. A stepwise contouring consensus method was established to define a systematic approach for contouring pancreatic adenocarcinoma GTV using MRI. Finally, visual contour heterogeneity amongst this expert group of participants calls attention to the considerable difficulty of accurate pancreatic GTV delineation.