Does slice thickness affect diagnostic performance of 64-slice CT coronary angiography in stable and unstable angina patients with a positive calcium score?
BACKGROUND
Coronary calcification can lead to over-estimation of the degree of coronary stenosis.


OBJECTIVE
To evaluate whether thinner reconstruction thickness improves the diagnostic performance of 64-slice CT coronary angiography (CTCA) in angina patients with a positive calcium score.


METHODS
We selected 20 scans from a clinical study comparing CTCA to conventional coronary angiography (CCA) in stable and unstable angina patients based on a low number of motion artifacts and a positive calcium score. All images were acquired at 64 x 0.625 mm and each CTCA scan was reconstructed at slice thickness/increment 0.67 mm/0.33 mm, 0.9 mm/0.45 mm, and 1.4 mm/0.7 mm. Two reviewers blinded for CCA results independently evaluated the scans for the presence of significant coronary artery disease (CAD) in three randomly composed series, with > or =2 weeks in between series. The diagnostic performance of CTCA was compared for the different slice thicknesses using a pooled analysis of both reviewers. Significant CAD was defined as >50% diameter narrowing on quantitative CCA. Image noise (standard deviation of CT numbers) was measured in all scans. Inter-observer variability was assessed with kappa.


RESULTS
Significant CAD was present in 8% of 304 available segments. Median total Agatston calcium score was 181.8 (interquartile range 34.9-815.6). Sensitivity at 0.67 mm, 0.9 mm, and 1.4 mm slice thickness was 70% (95% confidence interval 57-83%), 74% (62-86%), and 70% (57-83%), respectively. Specificity was 85% (82-88%), 84% (81-87%), and 84% (81-87%), respectively. The positive predictive value was 30 (21-38%), 29 (21-37%), and 28 (20-36%), respectively. The negative predictive value was 97% (95-98%), 97% (96-99%), and 97% (96-99%), respectively. Kappa for inter-observer agreement was 0.56, 0.58, and 0.59. Noise decreased from 32.9 HU at 0.67 mm, to 23.2 HU at 1.4 mm (P<0.001).


CONCLUSIONS
Diagnostic performance of CTCA in angina patients with a positive calcium score was not markedly affected by modest variations in reconstruction slice thickness.
Department of Cardiology, University Medical Center Utrecht, Utrecht, The Netherlands. m.meijs@umcutrecht.nl
Matthijs F L
MF
Meijs
Jan J J
JJ
de Vries
Annemarieke
A
Rutten
Ricardo P J
RP
Budde
Alexander M
AM
de Vos
W Bob
WB
Meijboom
Maarten J
MJ
Cramer
Pim J
PJ
de Feyter
Pieter A
PA
Doevendans
Mathias
M
Prokop
D000704:Analysis of Variance; D000787:Angina Pectoris / Q000000981:diagnostic imaging*; D000789:Angina, Unstable / Q000000981:diagnostic imaging*; D016477:Artifacts; D002114:Calcinosis / Q000000981:diagnostic imaging; D016009:Chi-Square Distribution; D003287:Contrast Media; D017023:Coronary Angiography; D006801:Humans; D007472:Iohexol / Q000031:analogs & derivatives; D011237:Predictive Value of Tests; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*
D003287:Contrast Media; D007472:Iohexol; C038192:iopromide