2Department of Radiation Oncology, Balikesir Atatürk City Hospital, Balıkesir-Türkiye
3Department of Radiation Oncology, Bursa Medicana Hospital, Bursa-Türkiye
4Department of Radiation Oncology, Bahçeşehir Memorial Hospital, İstanbul-Türkiye
5Department of Radiation Oncology, Koru Hospital, Ankara-Türkiye
6Department of Radiation Oncology, Kocaeli University Hospital, Kocaeli-Türkiye
7Department of Radiation Oncology, Bursa City Hospital, Bursa-Türkiye
8Department of Radiation Oncology, Manisa City Hospital, Manisa-Türkiye
9Department of Radiation Oncology, Eskişehir City Hospital, Eskisehir-Türkiye
10Department of Radiation Oncology, Ankara Memorial Hospital, Ankara-Türkiye
11Department of Radiation Oncology, Yedikule Chest Disease Hospital, İstanbul-Türkiye
12Department of Radiation Oncology, Vehbi Koç University Hospital, İstanbul-Türkiye
13Department of Radiation Oncology, Çam and Sakura City Hospital, İstanbul-Türkiye
14Department of Radiation Oncology, Yeni Yüzyil University Hospital, İstanbul-Türkiye DOI : 10.5505/tjo.2023.4115 OBJECTIVE
The objective of the present study was to assess the impact of detector type on measurements of small fields for the 6MV-FFF beam within 13 institutes of Elekta Versa HD linear accelerator users.
METHODS
Using various ion chambers, measurements of the percent depth dose (PDD), off-center ratio (OCR),
and output factor (OF) datasets in square areas between 2×2 and 50×50 mm2 for beam modelling in
Monaco TPS were collected, and dosimetric differences were compared. The types of used detectors
were PTW PinPoint 31014, IBA CC04, IBA CC01, IBA CC13 and Exradin A16, respectively. The effect
of the detector type on the OCR was evaluated by including penumbra width of fields, full width half
maximum value (FWHM) and FFF beam specific unflatness value. The PDDs were compared using
depth of dmax, d5 and d10. Also, the differences between OFs of each field and institution were analyzed
with and without correction factor.
RESULTS
The largest observed variance in dmax was 3 mm for a few institutions, whereas the majority of institutions
agreed with GBD dmax values within 2 mm. The agreement of the median PDD values with GBD was all within ±2%. The maximum deviation was under 2% for the shoulder part and 1% for the center
part of the OCR profiles for all field sizes. The maximum deviation of the penumbra and FWHM
value observed for all field sizes at certain institute OCR data was considered a user-dependent effect
instead of a detector. The relative percent difference both the OFuncorr and the OFcorr compared with
GBD for all field sizes was within ±3%.
CONCLUSION
The findings of this study obtained via a large multicentre study can be considered as an external crossverification
for Versa HD users doing beam data collection of Monaco and should help to offer accurate
TPS modelling of small fields and minimize the uncertainty of SRS and SBRT. Our results emphasized
that the use of several dosimetric systems, comparison of golden beam data, and multi-institutional
review are required.