Comparison and Assessment of Different Small Volume Radiation Detectors for Small Field Dosimetry in Stereotactic Radiotherapy.

OBJECTIVE

The small fields are used in the treatment of stereotactic radiosurgery (SRS), stereotactic radiotherapy (SRT), and stereotactic body radiation therapy (SBRT).  The aim of this study is to compare and assess various small-volume radiation detectors for small-field dosimetry.

METHODS

The small field dosimetry was performed with the High Definition Versa Linear Accelerator (HD-LINAC) from Elekta. The 6MV flattening filter (FF) and 6MV flattening filter free (FFF) radiation energies were chosen for the measurement.  The field sizes of 2x2cm2, 4x4cm2, 5x5cm2, 7x7cm2, 8x8cm2, and 10x10cm2 were selected. The quality assurance (QA) included percentage depth dose (PDD), dose profile measurement, and output factor (OF) measurement. The three radiation detectors, pinpoint ionization chamber type 31014, microDiamond detector type 60019, and Dosimetry diode SRS detector type 60018, from PTW-Freiburg, Germany, were utilized for the dosimetry. The measurements were performed with a radiation field analyzer (RFA) water phantom from PTW Freiburg.

RESULT

PDD values for all the detectors were similar except for Ds, which increased with the increase in field size in all detectors for the 6MV FF and 6MV FFF beams. Beam profile data gave similar results in all the detectors, with penumbra width having statistically significant differences in the 6MV FF beam between the three detectors. Penumbra width was found lower in pinpoint and microDiamond detectors for both energies compared to the SRS dosimetry diode.

CONCLUSION

The performance of all the detectors used in this study was similar with less noticeable differences between each other. As there was no great difference found in the results between the detectors, it can be concluded from this study that all three radiation detectors are suitable for the small field dosimetry performed for SRS and SBRT treatments.