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Title: Accuracy and stability of positioning in radiosurgery: Long term results of the Gamma Knife system

Abstract

The primary aim of this investigation was to determine the long term overall accuracy of an irradiation position of Gamma Knife systems. The mechanical accuracy of the system as well as the overall accuracy of an irradiation position was examined by irradiating radiosensitive films. To measure the mechanical accuracy, the GafChromic registered film was fixed by a special tool at the unit center point (UCP). For overall accuracy the film was mounted inside a phantom at a target position given by a two-dimensional cross. Its position was determined by CT or MRI scans, a treatment was planned to hit this target by use of the standard planning software and the radiation was finally delivered. This procedure is named ''system test'' according to DIN 6875-1 and is equivalent to a treatment simulation. The used GafChromic registered films were evaluated by high resolution densitometric measurements. The Munich Gamma Knife UCP coincided within x;y;z: -0.014{+-}0.09 mm; 0.013{+-}0.09 mm; -0.002{+-}0.06 mm (mean{+-}SD) to the center of dose distribution. There was no trend in the measured data observed over more than ten years. All measured data were within a sphere of 0.2 mm radius. When basing the target definition in the system test on MRImore » scans, we obtained an overall accuracy of an irradiation position in the x direction of 0.21{+-}0.32 mm and in the y direction 0.15{+-}0.26 mm (mean{+-}SD). When a CT-based target definition was used, we measured distances in x direction 0.06{+-}0.09 mm and in y direction 0.04{+-}0.09 mm (mean{+-}SD), respectively. These results were compared with those obtained with a Gamma Knife equipped with an automatic positioning system (APS) by use of a different phantom. This phantom was found to be slightly less accurate due to its mechanical construction and the soft fixation into the frame. The phantom related position deviation was found to be about {+-}0.2 mm, and therefore the measured accuracy of the APS Gamma Knife was evidently less precise by additional {+-}0.2 mm. These measurements demonstrate that an irradiation position defined by a CT scan can be hit within the intrinsic system precision. In radiosurgery with the Gamma Knife, a fixation with the Leksell stereotactic frame is applied. As this frame is considered to add no further uncertainties due to patient movements, the measured accuracy applies to a real patient treatment situation. The major contribution to the overall accuracy of an irradiation position is given by the MRI scans.« less

Authors:
; ; ; ;  [1];  [2];  [2];  [2]
  1. Gamma Knife Munich, Ingolstaedterstrasse 166, 80939 Munich (Germany)
  2. (Germany)
Publication Date:
OSTI Identifier:
20951164
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 34; Journal Issue: 4; Other Information: DOI: 10.1118/1.2710949; (c) 2007 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; ACCURACY; COMPUTER CODES; COMPUTERIZED TOMOGRAPHY; DOSIMETRY; IRRADIATION; NMR IMAGING; PATIENTS; PHANTOMS; PLANNING; QUALITY ASSURANCE; RADIATION DOSE DISTRIBUTIONS; RADIOTHERAPY; SURGERY

Citation Formats

Heck, Bernhard, Jess-Hempen, Anja, Kreiner, Hans Juerg, Schoepgens, Hans, Mack, Andreas, GKS GmbH, Ingolstaedterstrasse 166, 80939 Munich, Gamma Knife Center Krefeld, Lutherstrasse 54, 47805 Kefeld,, and Gamma Knife Frankfurt, Schleusenweg 2-16, 60528. Accuracy and stability of positioning in radiosurgery: Long term results of the Gamma Knife system. United States: N. p., 2007. Web. doi:10.1118/1.2710949.
Heck, Bernhard, Jess-Hempen, Anja, Kreiner, Hans Juerg, Schoepgens, Hans, Mack, Andreas, GKS GmbH, Ingolstaedterstrasse 166, 80939 Munich, Gamma Knife Center Krefeld, Lutherstrasse 54, 47805 Kefeld,, & Gamma Knife Frankfurt, Schleusenweg 2-16, 60528. Accuracy and stability of positioning in radiosurgery: Long term results of the Gamma Knife system. United States. doi:10.1118/1.2710949.
Heck, Bernhard, Jess-Hempen, Anja, Kreiner, Hans Juerg, Schoepgens, Hans, Mack, Andreas, GKS GmbH, Ingolstaedterstrasse 166, 80939 Munich, Gamma Knife Center Krefeld, Lutherstrasse 54, 47805 Kefeld,, and Gamma Knife Frankfurt, Schleusenweg 2-16, 60528. Sun . "Accuracy and stability of positioning in radiosurgery: Long term results of the Gamma Knife system". United States. doi:10.1118/1.2710949.
@article{osti_20951164,
title = {Accuracy and stability of positioning in radiosurgery: Long term results of the Gamma Knife system},
author = {Heck, Bernhard and Jess-Hempen, Anja and Kreiner, Hans Juerg and Schoepgens, Hans and Mack, Andreas and GKS GmbH, Ingolstaedterstrasse 166, 80939 Munich and Gamma Knife Center Krefeld, Lutherstrasse 54, 47805 Kefeld, and Gamma Knife Frankfurt, Schleusenweg 2-16, 60528},
abstractNote = {The primary aim of this investigation was to determine the long term overall accuracy of an irradiation position of Gamma Knife systems. The mechanical accuracy of the system as well as the overall accuracy of an irradiation position was examined by irradiating radiosensitive films. To measure the mechanical accuracy, the GafChromic registered film was fixed by a special tool at the unit center point (UCP). For overall accuracy the film was mounted inside a phantom at a target position given by a two-dimensional cross. Its position was determined by CT or MRI scans, a treatment was planned to hit this target by use of the standard planning software and the radiation was finally delivered. This procedure is named ''system test'' according to DIN 6875-1 and is equivalent to a treatment simulation. The used GafChromic registered films were evaluated by high resolution densitometric measurements. The Munich Gamma Knife UCP coincided within x;y;z: -0.014{+-}0.09 mm; 0.013{+-}0.09 mm; -0.002{+-}0.06 mm (mean{+-}SD) to the center of dose distribution. There was no trend in the measured data observed over more than ten years. All measured data were within a sphere of 0.2 mm radius. When basing the target definition in the system test on MRI scans, we obtained an overall accuracy of an irradiation position in the x direction of 0.21{+-}0.32 mm and in the y direction 0.15{+-}0.26 mm (mean{+-}SD). When a CT-based target definition was used, we measured distances in x direction 0.06{+-}0.09 mm and in y direction 0.04{+-}0.09 mm (mean{+-}SD), respectively. These results were compared with those obtained with a Gamma Knife equipped with an automatic positioning system (APS) by use of a different phantom. This phantom was found to be slightly less accurate due to its mechanical construction and the soft fixation into the frame. The phantom related position deviation was found to be about {+-}0.2 mm, and therefore the measured accuracy of the APS Gamma Knife was evidently less precise by additional {+-}0.2 mm. These measurements demonstrate that an irradiation position defined by a CT scan can be hit within the intrinsic system precision. In radiosurgery with the Gamma Knife, a fixation with the Leksell stereotactic frame is applied. As this frame is considered to add no further uncertainties due to patient movements, the measured accuracy applies to a real patient treatment situation. The major contribution to the overall accuracy of an irradiation position is given by the MRI scans.},
doi = {10.1118/1.2710949},
journal = {Medical Physics},
number = 4,
volume = 34,
place = {United States},
year = {Sun Apr 15 00:00:00 EDT 2007},
month = {Sun Apr 15 00:00:00 EDT 2007}
}