[Quality assurance in stereotactic space. Determination of the accuracy of aim and dose in single dose radiosurgery].
BACKGROUND
Single dose irradiation techniques require methods of quality assurance of high precision. The complete operational sequence of a treatment from imaging over irradiation planning up to the patient irradiation has to be controlled and verified in a phantom (Figure 2). These demands receive special topicality by the E-DIN 6875-1 [38], which will appear soon.


METHODS
A quality assurance package was developed to meet the requirements of the E-DIN 6875-1 [38]. It consists of versatile usable precision phantom (Figure 1), a dose measuring system for the tissue equivalent radiochromic film GAFCHROMIC trade mark type MD 55 II using a high-quality scanner, and a software for standardized test routines (Figures 2 to 4). Correction routines for film fog, darkening, temperature effect as well as for film inhomogeneities (double exposure technology) are implemented.


RESULTS
The measuring system permits routine dosimetry with inaccuracies typically < 5%, for the double exposure procedure typically < 3% with local dissolutions of approx. 1/100 mm in film plane, perpendicularly to it the film stack density and the film thickness (0.3 mm) are determining. The measuring system is designed to simulate the complete three-dimensional treatment of a patient (Figure 4).


CONCLUSIONS
The procedure achieves a high quality standard for all steps in radiosurgery. The simple handling permits the employment for the daily routine (according to E-DIN 6875-1 [38]), in addition, for the modelling of complicated 3-d of scattering conditions, e. g. close to risk structures.
Mack
Andreas
A
Gamma Knife Zentrum, Frankfurt am Main, Germany. a.mack@gkfrankfurt.de
Mack
Günther
G
Weltz
Dirk
D
Hönes
Andreas
A
Jess
Anja
A
Wowra
Berndt
B
Czempiel
Heinz
H
Heck
Bernd
B
Kreiner
Hans-Jürg
HJ
Seifert
Volker
V
Böttcher
Heinz
H
D005373:Film Dosimetry; D006801:Humans; D009464:Neuroma, Acoustic / Q000601:surgery; D019047:Phantoms, Imaging; D011785:Quality Assurance, Health Care; D016634:Radiosurgery / Q000592:standards*; D011879:Radiotherapy Dosage; D012984:Software; D014962:X-Ray Film