Purpose: To evaluate the immobilization accuracy of a novel vacuum bite block re‐locatable head frame (RHF) system in patients receiving intracranial stereotactic radiation therapy (SRT) by means of an infrared optical tracking system (OTS). Methods and Materials: The RHF was designed for multi‐session treatments on the Leksell GammaKnife Perfexion™. In the present REB approved study, the RHF was used for patients undergoing linac‐based SRT. A passive optical marker was placed on the bite block as a surrogate for patient motion. The OTS monitored patients continuously throughout each fraction. For each fraction, cone‐beam computed tomography (CBCT) was used to verify the patient position at three time points: after the initial setup, pre‐delivery following the automatic couch adjustments and post‐delivery. To investigate the reliability of the optical measurements, the OTS measurements were compared against the implemented couch shifts for patient setup. Intra‐fractional anatomical motion, as measured from the second and third CBCT scans, was compared with the difference in OTS marker positions. Real‐time OTS data throughout each fraction was assessed to determine if patients moved by more than 1 mm during treatments. Results: Currently, data from three patients have been analyzed. The couch motion measured from the OTS strongly correlated with the actual reported couch shift (Pearson correlation coefficient of 0.99). Mean differences between OTS and true couch motion were 0.01, 0.0, and 0.04 mm in the lateral, anterior‐posterior, and superior‐inferior directions, respectively. Mean differences between OTS and CBCT reported motion were 0.37, 0.07, and 0.01 mm respectively with a mean vector magnitude of 0.41 mm. The real‐time positional data indicated that there were few instances (3) of patient motion greater than 1mm. Conclusion: The OTS is a reliable tool for evaluation of intra‐fraction patient motion. The results of this study indicate that the RHF provides sufficient immobilization accuracy for SRT.
There is justification for a simulation model for assessing channel level protocols. The effect of the data link layer protocol parameters on the data transfer function is analyzed. The data link protocol parameters have been specified and split into two categories, which are customizable and not configurable. In the work, parameters such as the acceptable information frame size are related in detail to the tunable data link protocol parameter; service personnel format; time-out value; unconfirmed frame window size, etc. That nominal data transfer rate, error-correcting codes used, etc. are non-configurable parameters.
PURPOSE: To optimize the frame placement for patients receiving stereotactic radio surgery (SRS) using GammaKnife® Perfexion™, a simulation program was developed and its accuracy of collision clearance was compared with the planning system, Leksel Gamma Plan 8.0 (LGP). METHODS AND MATERIALS: A simulation program was designed in Matlab to do the following: import patient DICOM images with or without frame, automatically measure skull dimension from the images, simulate the frame, post, and pin placement, create isocenters, and check for collision for each isocenter. The program employs a graphical user interface that can be compiled to run on a personal computer. MR images from ten study patients were imported into the simulation program. Frame placement at the time of treatment was reproduced using the MR fiducial marker of the image in the simulation program. Post and pin length measured at the time of frame setup were used in the simulation. A total of 600 isocenters were selected for the comparison of clearance computed from the simulation program and from LGP. RESULTS: Average clearance at 600 isocenters tested was 6.7mm (standard deviation (SD) of 2.6 mm) from LGP and 6.9 mm (SD of 2.5 mm) from the simulation program. Mean differences between the computed clearance from the simulation program and LGP were −0.6, −0.3, 0.9 and 0.9 mm in anterior left (AL), anterior right (AR), posterior left (PL) and posterior right (PR) respectively. Standard deviations of the differences were 0.9, 1.0, 1.9, and 1.9 mm in the AL, AR, PL and PR directions respectively. CONCLUSION: A simulation program for virtual frame placement was developed to guide an optimal frame setup for patients receiving SRS using gamma knife Perfexion™. It is a reliable tool that can guide optimal frame setup to reduce the chance of collision.
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