# We are trying to measurement CTDI (CT Dose Index) and DLP (Dose Length Product) in Computed Tomography by MATLAB GUI or any other software. If anybody knows, please leave in …

21 Jul 2017 ter, a variety of measurement and calculation techniques will be reviewed for For a helical scan with pitch not equal to unity, CTDIvol.

SSDE attempts to make CT dose estimates more applicable to individual patients by applying a conversion factor, f size, to CTDI vol.The conversion factor, f size, is found via a lookup table in TG-204 (external link) and is based on the concept of effective diameter (equation below). Finally, each CT image header may contain a specific attribute tag for CTDI vol (0018,9345). The Attribute Description is given as “Computed Tomography Dose Index (CTDI vol), in mGy according to IEC 60601-2-44, Ed.2.1 (Clause 29.1.103.4), The Volume CTDI vol. It describes the average dose for this image for the selected CT conditions of CTDI (or CTDI vol), however, is not patient dose. 34 By definition, CTDI vol approximately represents the weighted average dose delivered to a uniform cylindrical phantom at a given size (either 16- or 32-cm diameter), which doesn’t represent any patient owing to the differences in size, body shape, and attenuation. CTDI CTDI w vol DLP CTDI L vol The dose-length product, DLP, includes the irradiated volume and represents the overall exposure for an examination and is calculated as following: where L is the scan length of a certain examination.

Equation: CTDI vol = CTDI w / pitch: Units: mGy Weighted CTDI: Volume CTDI: CTDI vol = CTDI w pitch CTDI w = ⅓ × CTDI 100 + ⅔ × CTDI 100 center periphery Since the CTDI is normalized to some given length across this direction we need to multiply by the scan length to calculate the dose length product (DLP). This is a nice name as Dose Length Product (DLP) directly describes what the quantity is as it is the product or multiplication of those two terms (DLP (mGy*cm) = CTDI (mGy) * Scan Length (cm). CTDIw = weighted or average CTDI given across the field of view N = number of simultaneous axial scans er x-ray source rotation T = thickness of one axial scan (mm) I = table increment per axial scan (mm) In helical CT the ratio of the I to (N x T) is the pitch; therefore in helical mode: CTDIvol = (1/pitch) x CTDIw 2016-08-23 · It is the CTDI vol multiplied by the length of the scan. The units are mGy centimeters (mGy cm). The DLP can be used to calculate a rough estimate of the effective dose. There is a relation between CTDIw and CTDIvol.

## The computed tomography dose index (CTDI) is a commonly used radiation exposure index in during a single rotation with a single beam, the CTDI is calculated by integrating over the dose profile for a C T D I v o l = C T D I w P {\

Dividing CTDIw by pitch (beam pitch in the case of multislice scanners) gives CTDIvol, which is an approximation to the average absorbed dose within the scanned volume. CTDI (Computed Tomography Dose Index 1. What Is Dose?

### (CTDI). The CTDI is a volume-averaged measure that is used in situ-ations where the table is incremented in conjunction with the tube ro-tation. Variants of the CTDI correct for averaging across the ﬁeld of view and for adjacent beam overlaps or gaps. CTDI is usually mea-sured with a pencil-shaped ionization chamber, although methods have

SSDE attempts to make CT dose estimates more applicable to individual patients by applying a conversion factor, f size, to CTDI vol.The conversion factor, f size, is found via a lookup table in TG-204 (external link) and is based on the concept of effective diameter (equation below). Effective diameter may also be estimated based on patient age using additional CTDI w alone only tells us what the average dose in a plane would be given a series of contiguous axial scans (stepped table feed) or helical scans with a pitch of unity. Dividing CTDIw by pitch (beam pitch in the case of multislice scanners) gives CTDIvol, which is an approximation to the average absorbed dose within the scanned volume.
Fotograferar Approximates the radiation dose for each section obtained during a helical scan. CTDIw is calculated by: CTDIw = 2/3 CTDI(periphery) + 1/3  for calculating DLP. The first one is CTDIvol which estimates the dose of the patient.

DLP stands for dose-length product. DLP is the CTDI (vol) multiplied by the scan length in centimeters and is given in units of mGy–cm. CTDI (or CTDI vol), however, is not patient dose.
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