A Short Note On Ct Dose Calculation ( Ct )

1217 Words Feb 20th, 2016 5 Pages
iSAP – CT Dose Calculation

The role of computed tomography (CT) in imaging has risen substantially in the previous decade (Hess et al. 2014). With its increasing demand, one of the most predominant concerns for radiation workers is the dose administered to the patient (Hess et al. 2014). Therefore, the calculation of dose is a parameter that must be monitored closely.

Task 1:

Exposure is the amount of electrical charge produced by ionising radiation per unit mass of air. It is measured in Coulomb per kilogram C kg-1, where its former unit was Roentgen (Schoepf 2005).

Absorbed dose
The absorbed dose is the energy (joules) deposited by ionising radiation per unit mass of material in kilograms, as a result of exposure to ionising radiation. The absorbed dose is therefore measured in J/kg or gray (Gy) where 1Gy = 1J/kg. The absorbed dose is calculated by multiplying exposure with W, where W is the conversion factor from exposure to absorbed dose depending on the absorbing medium (Siegel 2008).

Equivalent dose
The absorbed dose is a poor indicator of the likely biological effect, as the biological effect of the same absorbed dose will depend on the type of radiation. This is because the linear energy transfer of radiations that produce dense ionisation tracks cause more biological damage per unit dose than low linear energy transfer radiations, and thus must have higher radiation weighting factors. Therefore, the equivalent dose (HT) is measured…
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