Abstract
We modified the Imaging Performance Assessment of CT scanners (ImPACT) to evaluate the organ doses and the effective dose based on the International Commission on Radiological Protection (ICRP) Publication 110 reference male/female phantom with the Aquilion ONE ViSION Edition scanner. To select the new CT scanner, the measurement results of the CTDI100,c and CTDI100,p for the 160 (head) and the 320 (body) mm polymethylmethacrylate phantoms, respectively, were entered on the Excel worksheet. To compute the organ doses and effective dose of the ICRP reference male/female phantom, the conversion factors obtained by comparison between the organ doses of different types of phantom were applied. The organ doses and the effective dose were almost identical for the ICRP reference male/female and modified ImPACT. The results of this study showed that, with the dose assessment of the ImPACT, the difference in sex influences only testes and ovaries. Because the MIRD‐5 phantom represents a partially hermaphrodite adult, the phantom has the dimensions of the male reference man including testes, ovaries, and uterus but no female breasts, whereas the ICRP male/female phantom includes whole‐body male and female anatomies based on high‐resolution anatomical datasets. The conversion factors can be used to estimate the doses of a male and a female accurately, and efficient dose assessment can be performed with the modified ImPACT.PACS number: 87.53.LY, 87.57.Q‐, 87.57.‐s
Highlights
To obtain the effective dose in computed tomography (CT), the effective dose per unit dose length product (DLP) conversion factor is required, known as the k-factor in the International Commission on Radiological Protection (ICRP) Publication 102.(7,8,9,10) The applicable DLP is displayed on the CT console at the end of the procedure and can be used to quantify the total amount of radiation received during any given scan.[11] the k-factors are practical, they are based on data averaged over many scanner makes and models and are, not specific to a selected scanner
Comparison of 320-MDCT and 16-MDCT Estimation of the organ doses and effective dose (Fig. 6) of two types of CT scanners for the scan region of the head showed that the organ doses of 320-MDCT were 1 mGy lower for the brain and salivary glands than those of 16-MDCT
Comparison of dose of ICRP 110 and MIRD-5 Estimation of the organ doses and the effective dose (Figs. 7 and 8) with the LightSpeed VCT scanner in the chest-pelvis examination showed that most organ doses of the MIRD-5 phantom were larger than those of the ICRP 110 male phantom estimated by Zhang.[18]. On the other hand, the breasts and thyroid doses of the MIRD-5 were smaller than those of the ICRP 110 female
Summary
The Imaging Performance Assessment of CT scanners (ImPACT) group, the Scanner Evaluation Center of the United Kingdom National Health Service, developed an Excel (Microsoft) spreadsheet to provide a convenient user interface for determining organ doses by using the National Radiological Protection Board (NRPB) Monte Carlo dose datasets (i.e., NRPB-SR250).(12,13) The ImPACT CT patient dosimetry version 1.04 (released in May 2011) reflects further development of a method to map results from the original 23 scanner datasets to new CT scanners by applying the so-called “ImPACT factors.” These factors are based on tube voltage-dependent CT dose index free-in-air (CTDI air) and CTDI in the center (CTDI100,c) with either a standard head or standard body polymethylmethacrylate (PMMA) phantom. We modified the ImPACT to evaluate the organ doses and the effective dose based on the ICRP Publication 110 reference male/female (ICRP male/female) phantom by using the conversion factors for the Aquilion ONE ViSION Edition scanner.[16]
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