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Introduction
Published in A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha, Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020
A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha
Absorbed dose is defined as the energy absorbed by tissue divided by the tissue mass and is measured in grays. The radiation output from the CT is described by using the volume CT dose index CTDIvol and the dose length product DLP. The CTDIvol is calculated using a standard head or body phantom and is an estimate of the average X-ray output for a CT examination. The DLP is the total X-ray output integrated throughout the entire examination and is calculated by multiplying the CTDIvol by the scanned length in centimetres. More accurate values can be achieved post-scan if an automatic exposure device is used. It is important to note that this calculation does not take a patient’s body habitus into account. The size specific dose estimate or SSDE is calculated by multiplying the CTDIvol by a correction factor based on patient size.
Optimization and Dose Reduction in Medical Imaging of the Pregnant Patient
Published in Lawrence T. Dauer, Bae P. Chu, Pat B. Zanzonico, Dose, Benefit, and Risk in Medical Imaging, 2018
Wesley E. Bolch, Matthew Maynard, William J. Godwin, Amy M. Geyer, Linda Kroger
Wagner et al. (1997) presented comprehensive methods for estimating fetal radiation dose from radiographic, fluoroscopic, and CT procedures, as well as doses from radionuclide studies. Radiographic and fluoroscopic procedures are combined separately from CT, and both categories are further separated into in-field and out-of-field calculation methods. Several presented methods for estimating fetal doses from in-field radiographic and fluoroscopic procedures are based on depth-dose and tissue-air ratios. Two methods are presented for in-field CT doses: one based on free-in-air techniques and the other based on CT dose index (CTDI) measurement techniques presented by Felmlee et al. (1990) (discussed further below). Methods are also presented for estimating nuclear medicine doses from cumulated activity and radionuclide S-values.
Radiation Dose and Exposure Indicators
Published in Ken Holmes, Marcus Elkington, Phil Harris, Clark's Essential Physics in Imaging for Radiographers, 2021
Absorbed dose in gray’s is defined as the energy absorbed by tissue per unit mass. The radiation output from a CT procedure is described by using the volume CT dose index (CTDIvol) and the dose length product (DLP). The CTDIvol is calculated using standard phantoms and is an estimate of the average X-ray output for any given CT examination. The DLP is the total X-ray output integrated throughout the entire examination and is calculated by multiplying the CTDIvol by the scanned length. This calculation does not take a patient’s body habitus into account therefore the size specific dose estimate (SSDE) is calculated by multiplying the CTDIvol by a correction factor based on patient size.
Optimal tube potential and tube current for radiation dose reduction in routine adult head computed tomography scanning
Published in Radiation Effects and Defects in Solids, 2018
Jae-Seung Lee, Dae Cheol Kweon
Figure 1 shows the procedure for establishing a new CT scan variable. The CT scan parameters and CT dose index (CTDI) of a brain CT scan were compared with those of the CT scanner (SOMATOM Definition AS+, Siemens Healthcare, Forchheim, Germany). The scan parameters were tube voltage, tube current, slice thickness, pitch, scan field of view (SFOV), and scan time, which are directly related to the exposure dose. CT dose index (CTDIvol) and dose length product (DLP) were used as CT dose indices. Tube voltages of 80, 100 and 120 kVp were used, and scanning was performed using the fixed tube current technique.