open access

https://hdl.handle.net/2115/79366

Determination of appropriate conversion factors for calculating size-specific dose estimates based on X-ray CT scout images after miscentering correction

英語

Miscentering correction

2019-09

Springer

Radiological physics and technology

12(3)

283-289

In this study, we proposed and evaluated the validity of an optimized size-specific dose estimate, a widely used index of radiation dose in X-ray computed tomography (CT) examinations. Based on miscentering correction of scout images, we determined the appropriate conversion factors (CF) by using a phantom. Scans were conducted using a multi-detector CT system (Aquilion ONE, Canon Medical Systems). Four cylindrical phantoms were taken in the anteroposterior (AP) and axial directions to determine the relationship between pixel value and water-equivalent length (L-w). In the AP scout image, the pixel values at the selected slice positions were converted to L-w to calculate the water-equivalent diameter (D-w). The CF was derived from D-w and CF values before and after miscentering correction was calculated. Finally, the CF values were compared to those calculated from the axial image using the conventional methodology of the American Association of Physicists in Medicine. Before miscentering correction, the maximum difference between the CF values of the axial and scout images was 7.26%. However, after miscentering correction, the maximum difference was 1.34%. Validation using a whole-body phantom generally revealed low maximum differences between the CF from the axial image and the values from the miscentering-corrected scout images. These were 2.41% in the chest, 6.30% in the upper abdomen, 1.43% in the abdomen, and 2.45% in the pelvic region. Consequently, we concluded that our miscentering correction method for deriving the appropriate CF values based on scout images is advantageous.

学術雑誌論文

Accepted Manuscript

This is a post-peer-review, pre-copyedit version of an article published in Radiological Physics and Technology. The final authenticated version is available online at: http://dx.doi.org/10.1007/s12194-019-00519-5

1865-0333