IJMPCERO  Vol.7 No.2 , May 2018
In-Vivo Dosimetry Method for Measuring Peak Surface Dose Using Radiochromic Films during Computed Tomography Scanning of the Sinus
Abstract: Purpose: During computed tomography (CT) helical scanning mode the patient surface dose distribution is assumed to be non-uniform, therefore point dose measurement methods may lead to imprecise estimation of the radiation dose received by the patient skin in particular. We have used XRQA2 films as in-vivo dosimeters to measure the entrance skin dose during sinus exams. Methods: The films were placed under the patient head rest in order to sample the entrance surface dose in-vivo. We have performed in-vivo film irradiation on 23 patients in this study to verify the clinical suitability of the method and were found adequate. Results: The measured average ESD in the sinus exam was 11.7 ± 1.0 mGy, the PSD was 15.7 ± 1.7 mGy and the CTDI(vol) was 13.3 ± 0.1 mGy. The ratio of ESD/CTDI(vol) and PSD/CTDI(vol) was 0.88 and 1.18 respectively. The results indicate that the scanner registered CTDI(vol) underestimates the PSD and in the same time it overestimates the ESD by 18% and 13.6% respectively. Conclusion: The observed differences between the ESD, PSD and CTDI(vol) although seem small for the radiation dose range measured during CT of the sinus [13.2 - 13.4] mGy, but important for the medical physicist to know, since monitoring of patients’ doses from CT examinations is becoming more mandatory. The use of radiochromic film as in-vivo dosimeter does not interfere with the clinical radiological exam and does not produce any image artifacts. The method can be used to study other CT examinations specially the ones with large beam width, high pitch factor and high dose exams. The method allows measurement of the peak skin dose, examination of the CT dose profile and the 2D dose distribution in the XZ plan.
Cite this paper: Soliman, K. , Altimyat, S. , Alrushoud, A. , Alenezi, A. and Alkhorayef, M. (2018) In-Vivo Dosimetry Method for Measuring Peak Surface Dose Using Radiochromic Films during Computed Tomography Scanning of the Sinus. International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, 7, 151-159. doi: 10.4236/ijmpcero.2018.72013.

[1]   Hricak, H., Brenner, D.J., Adelstein, J.S., et al. (2011) Managing Radiation Use in Medical Imaging: A Multifaceted Challenge. Radiology, 258, 889-905.

[2]   ACR-AAPM (2012) ACR-AAPM Technical Standard for Diagnostic Medical Physics Performance Monitoring of Computed Tomography (CT) Equipment. (Resolution 34).

[3]   Cody, D.D., et al. (2013) AAPM Medical Physics Practice Guideline 1.a: CT Protocol Management and Review Practice Guideline, Task Group No.225. Journal Applied Clinical Medical Physics, 14, 3-12.

[4]   Brenner, D.J., McCollough, C.H. and Orton, C.G. (2006) It Is Time to Retire the Computed Tomography Dose Index (CTDI) for CT Quality Assurance and Dose Optimization? Medical Physics, 33, 1189-1191.

[5]   Huda, W. (2013) CT Dose Metrics. Radiology, 267, 964-967.

[6]   Seibert, A.J., Boone, J.M., Wotton-Gorges, S.L. and Lamba, R. (2014) Dose Is Not Always What It Seems: Where Very Misleading Values Can Result from Volume CT Dose Index and Dose Length Product. Journal of the American College of Radiology, 11, 233-237.

[7]   De Denaro, M., Bregant, P., Severgnini, M. and de Guarrini, F. (2007) In Vivo Dosimetry for Estimation of Effective Doses in Multislice CT Coronary Angiography. Medical Physics, 34, 3705-3710.

[8]   Tsalafoutas, I.A., Epistatou, A., Nikoletopoulos, S. and Tspaki, V. (2015) Measuring Skin Dose in CT Examinations under Complex Geometries: Instruments, Methods and Considerations. Physica Medica, 31, 1005-1014.

[9]   Devic, S., Seuntjens, J., Sham, E., et al. (2005) Precise Radiochromic Film Dosimetry Using a Flat-Bed Document Scanner. Medical Physics, 32, 2245-2253.

[10]   Niroomand-Rad, A., et al. (1998) AAPM Report No. 63, Recommendations of Radiation Therapy Committee Task Group No.55. Radiochromic Film Dosimetry. Medical Physics, 25, 2093-2115.

[11]   Martin, C.J., Gentle, D.J., Sookpeng, S., et al. (2011) Application of Gafchromic Film in the Study of Dosimetry Methods in CT Phantoms. Journal of Radiological Protection, 31, 389-409.

[12]   Rampado, O., Garelli, E., Deagostini, S., et al. (2006) Dose and Energy Dependence of Response of Gafchromic XR-QA Film for Kilovoltage X-Ray Beams. Physics in Medicine and Biology, 51, 2871-2881.

[13]   Niroomand-Rad, A., et al. (1998) Radiochromic Film Dosimetry: Recommendations of AAPM Radiation Therapy Committee Task Group No. 55. Medical Physics, 25, 2093-2115.

[14]   Mourão, A.P., Gonçalves Jr., R.G. and Alonso, T.C. (2014) Dose Profile Variation with Pitch in Head CT Scans using GAFCHROMIC Films. Recent Advances in Biomedical & Chemical Engineering and Materials Science, 1, 51-54.

[15]   Purwaningsih, S., Lubis, L.E., Pawiro, S.A. and Soejoko, D.S. (2016).Measurement of Computed Tomography Dose Profile with Pitch Variation using Gafchromic XR-QA2 and Thermoluminescence Dosimeter (TLD). Journal of Physics: Conference Series, 694, Article ID: 012046.

[16]   Lian, C.P.L., Wong, J.H.D., Young, A., Cutajar, D., Petasecca, M., Lerch, M.L.F. and Rosenfeld, A.B. (2013) Measurement of Multislice Computed Tomography Dose Profile with the Dose Magnifying Glass and the MOSkin Radiation Dosimeter. Radiation Measurements, 55, 51-55.

[17]   Tsalafoutas, I.A., Tsapaki, V., Triantopoulou, C., et al. (2008) Comparison of Measured and Calculated Skin Doses in CT-Guided Interventional Procedures. American Journal of Roentgenology, 191, 1601-1607.

[18]   Soliman, K. and Alenezi, A. (2014) Patient Entrance Surface Dose Measurements using XR-QA2 Gafchromic Films during Micturating Cystourethrography Procedures. Radiation Protection Dosimetry, 158, 170-174.

[19]   Boivin, J., Tomic, N., Fadlallah, B., Deblois, F. and Devic, S. (2011) Reference Dosimetry during Diagnostic CT Examination using XR-QA Radiochromic Film Model. Medical Physics, 38, 5119-5129.

[20]   De las Heras, H., Minniti, R., Wilson, S., et al. (2013) Experimental Estimates of Peak Skin Dose and Its Relationship to CT Dose Index using CTDI Head Phantom. Radiation Protection Dosimetry, 157, 536-542.

[21]   Zhang, D., Cagnon, C.H., Villablanca, P.J., et al. (2012) Peak Skin and Eye Lens Radiation Dose from Brain Perfusion CT Based on Monte Carlo Simulation. American Journal of Roentgenology, 198, 412-417.

[22]   Zhang, D., Savandi, A.S., Demarco, J., et al. (2009) Variability of Surface and Center Position Dose in MDCT: Monte Carlo Simulations using CTDI and Anthropomorphic Phantoms. Medical Physics, 36, 1025-1038.