Non-invasive coronary computed tomography angiography (CCTA) has become an important
tool for visualisation of coronary arteries since the introduction of 64-channel detector CCTA
in 2004. It has been proved to be especially beneficial for ruling out coronary artery disease
(CAD) in selected patient populations, due to the high negative predictive value (NPV).
The aim of this thesis was to study some aspects of the introduction, establishment and
development of a new method, retrospectively ECG-gated CCTA with 64-channel detector, to
evaluate coronary arteries.
In study I the diagnostic capacity and limitation of CCTA was compared to that of invasive
coronary angiography (ICA) in a newly established CCTA team. CCTA had a very high NPV
but the number of non-diagnostic scans was also high. The main limitations were motion
artifacts and vessel calcifications, while short experience in reading CCTA did not affect
image interpretation.
Study II described the learning-curve effect of the interpretation of 100 CCTA and also
compared the diagnostic accuracy of both radiologists and radiographers, after a common
introduction. The review time for novices was approximately halved during the first 100
cases, with maintained diagnostic accuracy. There was a learning-curve effect in positive
predictive value (PPV) for radiologists, but not for the radiographers. However, the diagnostic
accuracy of dedicated radiographers indicated that they might be considered as part of the
evaluation team.
Study III compared the radiation exposure in retrospectively ECG-gated CCTA and ICA in
the same population. Both mean estimated effective dose (ED) and organ doses (skin, breast,
lung and oesophagus) were higher in CCTA when compared to ICA. The relatively high
radiation dose to breast indicates that bismuth shielding should be used in women when
performing CCTA. When using the updated tissue weighting factors provided in ICRP 103
the calculated ED from CCTA were significantly higher than those obtained using outdated
ICRP 60.
In study IV the image quality and radiation doses were compared when decreasing X-ray tube
peak kilovoltage (kVp) from 120 to 100 kVp in patients undergoing CCTA. By reduction of
tube voltage the radiation dose was almost halved while the diagnostic image quality was kept
at a clinically acceptable level.
In conclusion, CCTA is increasingly available throughout the world as an alternative to gold
standard ICA, especially due to the excellent capability to rule out CAD. Still, retrospectively
ECG-gated 64-channel detector CCTA has limitations such as motion artifacts and vessel
calcifications. Another limitation is the high radiation doses required for CCTA compared to
ICA. By lowering the kVp from traditionally 120 kVp to 100 kVp the radiation dose is halved
while retaining diagnostic accuracy. There is a learning curve effect (regarded PPV and
review time) of the interpretation of CCTA. However, more than 100 reviewed CCTA cases
are necessary to reach a diagnostic accuracy that is acceptable