Experimental determination of stereotactic cone size and detector specific output correction factor
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2017-08-22 |
| Journal | British Journal of Radiology |
| Authors | Dayananda Sharma, Rahul Chaudhary, Sunil Dutt Sharma, Shaju Pilakkal, Sachin K Rasal |
| Institutions | Kokilaben Dhirubhai Ambani Hospital, Advanced Centre for Treatment, Research and Education in Cancer |
| Citations | 10 |
Abstract
Section titled “Abstract”Abstract: Objective: To investigate the effect of intermediate field size (fint), volume of reference ionization chamber (IC) and normalization conditions on output factor (OFdetfclin) measurement using small field detectors (SDs) and derive OFdetfclin correction factors kQclin,Qintfclin,fint(SD) for active and passive detectors. Methods: Measurements were made on Novalis-Tx accelerator for 6 MV photon at 1000 MU min-1. Six active SDs, high resolution diodes (SFD, EDGE, PTW 60008), CC01 IC, PTW 60003 natural diamond, Exradin W1 plastic scintillator and two passive detectors (Al2O3:C nanoDot-OSLD and Gafchromic EBT3 films) were used for measurement from small circular cones having 4 to 15 mm diameter. Effect of the choice of fint ranging from 20 × 20mm2 to 40 × 40 mm2 and reference ICs (FC65, PPC40, CC13) volume on OFdetfclin was investigated for all active SDs. Influence of direct normalization at reference field of 40 × 40mm2 or 100 × 100 mm2 and indirect normalization at 100 × 100 mm2 through fint using Daisy-chain strategy on OFdetfclin was also investigated. kQclin,Qintfclin,fint(SD) was calculated as ratio of the OFdetfclin of each SDs relative to Gafchromic EBT3. Results: For any combination of SDs and reference ICs, selection of fint of 40 × 40 mm2 will result in OFdetfclinvariation to within ±1.8%. Indirect normalization at 100 × 100 mm2 through fint of 40 × 40 mm2 and direct normalization at 40 × 40 mm2 showed comparable (≤2%) results for EDGE, PTW 60008 and CC01. Whereas, for PTW 60003 and Exradin W1 direct and indirect normalization at 100 × 100 mm2 agrees within −2%. OFdetfclin measurement by SDs following Daisy-chain strategy shows deviation as large as 23% for 4 mm cone which reduces to <2% for cone size >10 mm except for nanoDot. The calculated kQclin,Qintfclin,fint(SD) is least for SFD (0.992-1.013) and largest for nanoDot (1.047-1.294) which reduces to 0.99-1.023 after correcting for volume averaging effect. The long-term standard uncertainty (k = 2, 95%CI) was largest for nanoDot (2.93%) and least for PTW60003 (0.11%). Conclusion: Medium size IC is less sensitive to fint and could be a better alternative to standard volume ICs. Minimum fint of 40 × 40 mm2 is suggested in Daisy-chain strategy. Different normalization conditions could lead to OFdetfclin variation measured by same SD up to ±5%. kQclin,Qintfclin,fint(SD) varies largely with cone size and detector volume. Advances in knowledge: Comprehensive study of the influencing parameters and conditions on OFdetfclin measurement from single data set and estimation of kQclin,Qintfclin,fint(SD) for newly emerging detectors.
Tech Support
Section titled “Tech Support”Original Source
Section titled “Original Source”References
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