Cardiac CT: are we underestimating the dose? A radiation dose study utilizing the 2007 ICRP tissue weighting factors and a cardiac specific scan volume.
OBJECTIVE
To calculate the effective dose from cardiac multidetector computed tomography (MDCT) using a computer-based model utilizing the latest International Commission on Radiation Protection (ICRP) 103 tissue-weighting factors (2007), to compare this dose with those calculated with previously published chest conversion factors and to produce a conversion factor specific for cardiac MDCT.


METHODS
An observational study of 152 patients attending for cardiac MDCT as part of their usual clinical care in a university teaching hospital. The dose for each examination was calculated using the computer-based anthropomorphic ImPACT model (the imaging performance assessment of CT scanners) and this was compared with the dose derived from the dose-length product (DLP) and a chest conversion factor.


RESULTS
The median effective dose calculated using the ImPACT calculator (4.5 mSv) was significantly higher than the doses calculated with the chest conversion factors (2.2-3 mSv).


CONCLUSIONS
The use of chest conversion factors significantly underestimates the effective dose when compared to the dose calculated using the ImPACT calculator. A conversion factor of 0.028 would give a better estimation of the effective dose from prospectively gated cardiac MDCT.
Plymouth Hospitals NHS Trust, Derriford Hospital, Plymouth, Devon, UK. Oliver.gosling@pms.ac.uk
O
O
Gosling
R
R
Loader
P
P
Venables
N
N
Rowles
G
G
Morgan-Hughes
C
C
Roobottom
D001822:Body Burden; D003198:Computer Simulation; D006321:Heart / Q000000981:diagnostic imaging*; D006801:Humans; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000517:prevention & control*; D011874:Radiometry / Q000379:methods; D012542:Scattering, Radiation; D014057:Tomography, X-Ray Computed / Q000379:methods*