Clinical performance of a transmission detector array for the permanent supervision of IMRT deliveries.
OBJECTIVE
Clinical evaluation of a novel dosimetric accessory serving the permanent supervision of MLC function.


METHODS
The DAVID system (PTW-Freiburg, Germany) is a transparent, multi-wire transmission ionization chamber, placed in the accessory holder of the treatment head. Since each of the 37 individual wires is positioned exactly below the associated leaf pair of the MLC, its signal records the opening of this leaf pair during patient treatment.


RESULTS
The DAVID system closes a gap in the quality assurance program, permitting the permanent in-vivo verification of IMRT plans. During dosimetric plan verification with the 2D-ARRAY (PTW-Freiburg, Germany), reference values of the 37 DAVID signals are collected, with which the DAVID readings recorded during daily patient treatment are compared. This comparison is visually displayed in the control room, and warning and alarm levels of any discrepancies can be defined. The properties of the DAVID system as a transmission device, its sensitivity to beam delivery and leaflet errors as well as its stability have been analyzed for clinically relevant examples. In a recent version, the DAVID system has been equipped with 80 wires.


CONCLUSIONS
The DAVID system permits the on-line detection of clinically relevant MLC discrepancies in IMRT deliveries.
Working Group Medical Radiation Physics, Carl von Ossietzky University Oldenburg, Germany.
Björn
B
Poppe
Hui Khee
HK
Looe
Ndimofor
N
Chofor
Antje
A
Rühmann
Dietrich
D
Harder
Kay C
KC
Willborn
D006801:Humans; D011785:Quality Assurance, Health Care; D011829:Radiation Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation* / Q000379:methods*