How is Ctdivol calculated?
How is Ctdivol calculated?
The CTDI calculation assumes that the radiation decreases linearly from the outside to the center and is calculated as CTDI = (1/3) * radiationcenter + (2/3) * radiationperiphery. It is then divided by the length of the scan to give a CTDI per slice.
Why is CTDI used?
The CTDIvol is a standardized measure of the radiation output of a CT system, measured in a cylindrical acrylic phantom, that enables users to gauge the amount of emitted radiation and compare the radiation output between different scan protocols or scanners.
What does mGy cm mean?
Dose Length Product (mGy cm) As discussed above CTDI is a measure of the absorbed radiation dose, the absorbed dose for a given size phantom.
What is weighted CTDI?
Abstract. Purpose: The weighted computed tomography dose index (CTDIw ) uses measured CTDI values at the center and periphery of a cylindrical phantom. The CTDIw value is calculated using conventional, Bakalyar’s, and Choi’s weighting factors.
What is CTDI and DLP?
The term CTDI(vol), in the unit of milligray (mGy), is a reference value used for the measurement of radiation dose in a plastic cylinder. 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.
What is a CTDI phantom?
Computed Tomography Dose Index (CTDI) is a key part of your CT quality assurance program. The CTDI Phantom was designed to meet specifications outlined by the Food and Drug Administration (FDA 21CFR 1020.33) and the International Electrotechnical Commission (IEC 60601-2-44).
What is medical term CTDI?
CT dose index (CTDI) (measured in mGy) is a standardized measure of radiation dose output of a CT scanner which allows the user to compare radiation output of different CT scanners.
What is DLP score?
Dose length product (DLP) measured in mGy*cm is a measure of CT tube radiation output/exposure. It is related to volume CT dose index (CTDIvol), but CTDIvol represents the dose through a slice of an appropriate phantom. DLP accounts for the length of radiation output along the z-axis (the long axis of the patient).
What does total DLP mean?
Dose Length Product (DLP) • DLP is a proxy for the total absorbed dose in a phantom over the length of a scan. • DLP is useful for comparing exam doses if scan lengths are equivalent. • DLP is measured in milligray-centimeter (mGy-cm).
What is CT pitch?
Single slice CT (SSCT) The term detector pitch is used and is defined as table distance traveled in one 360° gantry rotation divided by beam collimation 2. For example, if the table traveled 5 mm in one rotation and the beam collimation was 5 mm then pitch equals 5 mm / 5 mm = 1.0.
What are CT phantoms made of?
Purpose: Currently, single-photon emission computed tomography (SPECT)/computed tomography (CT) lung phantoms are commonly constructed using polystyrene beads and interstitial radioactive water.
What’s the difference between ctdiw and ctdivol?
Therefore CTDIw represents the average radiation dose over the x and y direction whereas CTDIvol represents the average radiation dose over the x, y and z directions. Dose Length Product The dose length product (DLP) is the measure of ionizing radiation exposure during the entire acquisition of images.
What is the difference between DLP and ctdivol?
CTDIvol is based on measurements obtained when scanning either a 16cm or 32 cm phantom. Essentially, it represents scanner output. DLP is derived from CTDIvol, but incorporates a scan length component. Both function as reasonable proxiesfor absorbed dose but do not represent the actual patient dose.
How is the dose index of ctdivol calculated?
CTDIvol (mGy) is obtained by dividing CTDI w by pitch factor. Another commonly used index is the dose-length product (DLP) which factors in the length of the scan to show overall dose output
What is the ratio of pitch to ctdivol?
In helical CT the ratio of the I to (N x T) is the pitch; therefore in helical mode: CTDIvol = (1/pitch) x CTDIw. CTDIvol (or CTDI volume) represents the dose for a specific scan protocol which takes into account gaps and overlaps between the radiation dose profile from consecutive rotations of the x-ray source.
