Reference dosimetry data and modeling challenges for Elekta accelerators based on IROC-Houston site visit data.

Area of Science:

• Medical Physics
• Radiation Oncology
• Dosimetry

Background:

• Reference dosimetry data is crucial for validating treatment planning system (TPS) calculations.
• The Imaging and Radiation Oncology Core at Houston (IROC-Houston) has collected extensive data on linear accelerators (linacs).

Purpose of the Study:

• To analyze dosimetry data from numerous Elekta linacs to provide an independent check for TPS commissioning and validation.
• To compare measured dosimetric parameters with institutional TPS calculations for Elekta linacs.

Main Methods:

• Analysis of data from approximately 50 Elekta linacs collected between 2000 and 2014.
• Point dose measurements in a water phantom for parameters including percentage depth dose, output factors, small-field output factors, off-axis factors, and wedge factors.
• Comparison of measured data against TPS calculations for each linac, stratified by energy (6, 10, 15, 18 MV).

Main Results:

• Reference dosimetry values were compiled and analyzed by linac head type.
• Percentage depth dose and output factors generally showed good agreement between measurements and TPS.
• Small-field output factors, off-axis factors, and wedge factors frequently exhibited substantial disagreement with TPS calculations.

Conclusions:

• Collected reference data for Elekta linacs offers physicists an independent verification method to prevent significant treatment errors.
• Identified dosimetric parameters that are more prone to error, providing practical guidance for TPS commissioning in radiation oncology.