Purpose: To develop a procedure for conducting true 3D treatment planning and evaluation using a novel 3D display device integrated with a conventional treatment planning system for a multi‐institutional planning study. Method and Materials: The 3D display device, Perspecta, includes 3D cursor and beam placement tools and renders auto‐stereoscopic images with a resolution of about 100 million voxels. Treatment planning calculations occur within Pinnacle and scripts are used to transfer all plan information bidirectionally between Pinnacle and Perspecta. Perpsecta includes software (PerspectaRad) to integrate information for displaying and planning. The procedure includes: 1) Transfer of contour information from Pinnacle to Perspecta; 2) Determining or refining beam orientations utilizing Perspecta; 3) Transferring the plan back to Pinnacle for dose calculation; 4) Transferring the dose distribution to Perspecta for evaluation in 3D. Results: By using this procedure, true 3D treatment planning and evaluation has been conducted for the first 11 cases in a multi‐institutional study. Beam placement was readily accomplished on the 3D device. Geometric relationships of beams and target volumes were reproducible and consistent after transfer between the devices. All relevant target volumes and doses were visualized on both devices and evaluated on both 3D and conventional devices. Conclusions: We have successfully established reliable, bi‐directional integration of a true 3D display with a treatment planning system that calculates dose in 3D. We believe that this results in enhanced understanding of anatomic, dosimetric, and geometric relationships which can in turn be used to more readily improve and/or optimize DVH and isodose distributions beyond what can be done with multiplanar 2D and pseudo 3D displays on flat CRT screens. We are in the process of confirming this impression with a prospective, multi‐institutional study designed to test this issue. Conflict of Interest: Actuality Systems Inc. provided the 3D display Perspecta used in this study.

Purpose:To gauge the dosimetric impact of segmentation differences amongst experts and an automated system for intracranial organs at risk in the presence of large space‐occupying lesions being treated with IMRT.Methods:Eight expert raters and a single automated system were used to segment normal tissues of the brain using MR and CT for 20 patients. The expert segmentations were used to generate ground truth estimations. One hundred‐eighty IMRT plans were generated to test impact of segmentation differences on three dosimetric end points: target coverage, dose to ground truth, and dose reported versus dose to ground truth. Several dosimetric figures of merit with guidance from QUANTEC were used quantitate these differences: mean/maximum dose, V45, V54, V59, V64 and D1mL for the normal tissues; min, mean, maximum, and V95 for target coverage.Results:We found target coverage was not affected by segmentation differences. Inverse‐planning was also generally robust to segmentation differences and not result in marked over doses to the simulated ground truth structures. Dose reporting discrepancies, however, were commonplace and could be large; that is, the dose reported by the plan compared to that which was the best estimate of true dose, were over or under reported by as much as 30 Gy; one third of maximum doses were under‐ or over‐reported by 2 Gy or more.Conclusion:This work indicates that inverse‐planning in the context of large brain lesions may be generally robust to segmentation differences in terms of target coverage and true dose to the normal tissues. Discrepancies in dose reporting of maximum dose were large, could impact treatment decisions, and may contribute to lack of consensus regarding toxicity, especially relating to the brainstem and optic pathway. These results indicate using figures of merit for planning other than the maximum dose, such as the mean and volume doses.

Purpose: The goal of this study is to measure MTF of two dual‐screen CR systems, and to explain the correlation between their system resolution and the physical properties of phosphor screens. Method and Materials: Modulation transfer function (MTF) is commonly used method to characterize the performance of an imaging system. The well‐established edge method is used to quantify the MTF of digital radiographic systems. We use a sharply polished edge slanted with respect to sampling detector grid, which allows measurement of oversampled edge function profiles. The focus of this study is on the comparison of the presampled MTFs obtained for different thicknesses of phosphor screens and pixel sizes. MTFs were measured with both diagnostic and 6 MV x‐rays. The storage phosphors used in this study were two commercially available CR plates: Kodak EC‐L fast and Kodak EC‐L regular cassettes. Results: The scan times per pixel for both high (0.171 mm) and low (0.342 mm) resolution are much shorter than 558 μs of the dominant luminescence lifetime for Gd2O2S:Tb, used in this study. Consequently, the spatial resolution of KODAK 2000RT CR system is lower in the scan direction than in the moving direction due to the afterglow effect. A comparison of the MTFs with Kodak EC‐L fast and regular cassettes indicates that the spatial resolution of dual‐screen CR systems does not depend on the total thickness of phosphor screens but is determined by the thickness of the thicker phosphor screen in the dual‐screen CR system. Conclusion: MTFs in laser scan direction roll off faster than in phosphor transport direction with KODAK 2000RT CR system. The resolution is related to the thickness of individual phosphors layers.