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Updated: Jun 16, 2026
Dosimetry for Cell Irradiation using Orthovoltage (40-300 kV) X-Ray Facilities
Published on: February 20, 2021
Clinical performance of a transmission detector array for the permanent supervision of IMRT deliveries
Björn Poppe1, Hui Khee Looe, Ndimofor Chofor
1Working Group Medical Radiation Physics, Carl von Ossietzky University Oldenburg, Germany.
Background And Purpose:
Clinical evaluation of a novel dosimetric accessory serving the permanent supervision of MLC function.
Materials And 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.
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