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TH‐C‐BRA‐11: First Experiments of a Prototype Device for Simultaneous Imaging and Dose Verification in Radiotherapy

Journal Article


Abstract


  • Purpose: Current model electronic portal imaging devices (EPIDs) used in radiotherapy are optimised for imaging but problematic for accurate dosimetry. The aim of this project is to develop a new EPID capable of simultaneous imaging and water equivalent dosimetry. This work reports our first experimental results. Methods: A prototype device based on a segmented plastic scintillator (SegmentedPS) was developed. The prototype device was tested in comparison with three other detector configurations, all utilising the same a‐Si photodiode array used in conventional EPIDs. The configurations tested were; i) standard indirect configuration with phosphor/copper (STANDARD), ii) direct configuration with 1.5 cm solid water build‐up (DIRECT), iii) 2 cm thick sheet of plastic scintillator (PSsheet), and iv) 1.5 cm thick prototype SegmentedPS. The sensitivity, dose response and image quality was assessed in each configuration. The dose response was assessed in terms of field size response and off‐axis response relative to reference dose in water measurements at the equivalent depth. The image quality was assessed using an image quality phantom. Results: The sensitivity of each device relative to the STANDARD configuration was 0.03(DIRECT), 0.63(PSsheet), and 0.35(SegmentedPS). The agreement in field size response relative to dose in water data for square field sizes 4 cm to 15 cm was within 4.8%(STANDARD), 0.9%(DIRECT), 22%(PSsheet), and 1.3%(SegmentedPS). The agreement in off‐axis ratios at 15 cm off‐axis, relative to dose in water data, was within 23%(STANARD), 4%(DIRECT), 5%(PSsheet), and 4%(SegmentedPS). Image quality parameters (f50/CNR) for each configuration were 0.41/993(STANDARD), 0.30/167(DIRECT), 0.22/125(PSsheet) and 0.23/214(SegmentedPS). Conclusions: First experiments with the prototype SegmentedPS EPID demonstrated the potential for simultaneous imaging and water equivalent dosimetry. Further design optimisation is required to approach the imaging performance of STANDARD a‐Si EPIDs, while maintaining water equivalent dose response. Cancer Council NSW Research Project Grant (RG 11‐06) Cancer Institute NSW Research Equipment Grant (10/REG/1‐20). © 2012, American Association of Physicists in Medicine. All rights reserved.

UOW Authors


  •   Holloway, Lois (external author)

Publication Date


  • 2012

Citation


  • Vial, P., Deshpande, S., Blake, S., Mcnamara, A., Holloway, L., Greer, P., & Kuncic, Z. (2012). TH‐C‐BRA‐11: First Experiments of a Prototype Device for Simultaneous Imaging and Dose Verification in Radiotherapy. Medical Physics, 39(6), 4002. doi:10.1118/1.4736327

Scopus Eid


  • 2-s2.0-84878334421

Web Of Science Accession Number


Start Page


  • 4002

Volume


  • 39

Issue


  • 6

Abstract


  • Purpose: Current model electronic portal imaging devices (EPIDs) used in radiotherapy are optimised for imaging but problematic for accurate dosimetry. The aim of this project is to develop a new EPID capable of simultaneous imaging and water equivalent dosimetry. This work reports our first experimental results. Methods: A prototype device based on a segmented plastic scintillator (SegmentedPS) was developed. The prototype device was tested in comparison with three other detector configurations, all utilising the same a‐Si photodiode array used in conventional EPIDs. The configurations tested were; i) standard indirect configuration with phosphor/copper (STANDARD), ii) direct configuration with 1.5 cm solid water build‐up (DIRECT), iii) 2 cm thick sheet of plastic scintillator (PSsheet), and iv) 1.5 cm thick prototype SegmentedPS. The sensitivity, dose response and image quality was assessed in each configuration. The dose response was assessed in terms of field size response and off‐axis response relative to reference dose in water measurements at the equivalent depth. The image quality was assessed using an image quality phantom. Results: The sensitivity of each device relative to the STANDARD configuration was 0.03(DIRECT), 0.63(PSsheet), and 0.35(SegmentedPS). The agreement in field size response relative to dose in water data for square field sizes 4 cm to 15 cm was within 4.8%(STANDARD), 0.9%(DIRECT), 22%(PSsheet), and 1.3%(SegmentedPS). The agreement in off‐axis ratios at 15 cm off‐axis, relative to dose in water data, was within 23%(STANARD), 4%(DIRECT), 5%(PSsheet), and 4%(SegmentedPS). Image quality parameters (f50/CNR) for each configuration were 0.41/993(STANDARD), 0.30/167(DIRECT), 0.22/125(PSsheet) and 0.23/214(SegmentedPS). Conclusions: First experiments with the prototype SegmentedPS EPID demonstrated the potential for simultaneous imaging and water equivalent dosimetry. Further design optimisation is required to approach the imaging performance of STANDARD a‐Si EPIDs, while maintaining water equivalent dose response. Cancer Council NSW Research Project Grant (RG 11‐06) Cancer Institute NSW Research Equipment Grant (10/REG/1‐20). © 2012, American Association of Physicists in Medicine. All rights reserved.

UOW Authors


  •   Holloway, Lois (external author)

Publication Date


  • 2012

Citation


  • Vial, P., Deshpande, S., Blake, S., Mcnamara, A., Holloway, L., Greer, P., & Kuncic, Z. (2012). TH‐C‐BRA‐11: First Experiments of a Prototype Device for Simultaneous Imaging and Dose Verification in Radiotherapy. Medical Physics, 39(6), 4002. doi:10.1118/1.4736327

Scopus Eid


  • 2-s2.0-84878334421

Web Of Science Accession Number


Start Page


  • 4002

Volume


  • 39

Issue


  • 6