Program Information
Patient Organ Specific Dose Assessment in Coronary CT Angiograph Using Voxellaized Volume Dose Index in Monte Carlo Simulation
Fallal Mohammadi Gh.1 , Riyahi Alam N.1*, Graily Gh.1 , Paydar R.2 ,(1) Tehran University of Medical Scienced(TUMS), School of Medicine,Department of Nedical Physics and Biomedical Engineering, Tehran, Iran,(2) Iran University of Medical Sciences(IUMS), Allied Medicine Faculty, Department of radiation Sciences, Tehran, Iran
Presentations
SU-F-I-38 (Sunday, July 31, 2016) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose:
Clinical use of multi detector computed tomography(MDCT) in diagnosis of diseases due to high speed in data acquisition and high spatial resolution is significantly increased. Regarding to the high radiation dose in CT and necessity of patient specific radiation risk assessment, the adoption of new method in the calculation of organ dose is completely required and necessary. In this study by introducing a conversion factor, patient organ dose in thorax region based on CT image data using MC system was calculated.
Methods:
The geometry of x-ray tube, inherent filter, bow tie filter and collimator were designed using EGSnrc/BEAMnrc MC-system component modules according to GE-Light-speed 64-slices CT-scanner geometry. CT-scan image of patient thorax as a specific phantom was voxellised with 6.25mm3 in voxel and 64x64x20 matrix size. Dose to thorax organ include esophagus, lung, heart, breast, ribs, muscle, spine, spinal cord with imaging technical condition of prospectively-gated-coronary CT-Angiography(PGT) as a step and shoot method, were calculated. Irradiation of patient specific phantom was performed using a dedicated MC-code as DOSXYZnrc with PGT-irradiation model. The ratio of organ dose value calculated in MC-method to the volume CT dose index(CTDIvol) reported by CT-scanner machine according to PGT radiation technique has been introduced as conversion factor.
Results:
In PGT method, CTDIvol was 10.6mGy and Organ Dose/CTDIvol conversion factor for esophagus, lung, heart, breast, ribs, muscle, spine and spinal cord were obtained as; 0.96, 1.46, 1.2, 3.28. 6.68. 1.35, 3.41 and 0.93 , respectively.
Conclusion:
The results showed while, underestimation of patient dose was found in dose calculation based on CTDIvol, also dose to breast is higher than the other studies. Therefore, the method in this study can be used to provide the actual patient organ dose in CT imaging based on CTDIvol in order to calculation of real effective dose(ED) based on organ dose.
Funding Support, Disclosures, and Conflict of Interest: This work has been supported by the research chancellor of tehran university of medical sciences(tums), school of medicine, Tehran, Iran
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