European journal of nuclear medicine and molecular imaging 05/2012; 37(4):832-832. · 4.99 Impact Factor
ABSTRACT: PurposeCarimas™ (Cardiac Image Analysis System) is a new software package developed at the Turku PET Centre for the quantitation
of PET studies of the heart with a broad range of tracers. The goal of this study was to assess the reproducibility of results
the package provides for myocardial perfusion (MP) quantitation using 15O-labelled water.
MethodsFour observers with various levels of experience in nuclear medicine independently analysed 20 MP studies (10 rest flow: “rest”,
10 adenosine-induced hyperaemia: “stress”). Each study was analysed twice. The linear mixed model for repeated measures was
fitted to the data to calculate intraclass correlation coefficients (ICC), differences between the repeats (the intraobserver
differences) and differences between the observers (the interobserver differences). Also, Pearson correlation coefficients
(r) were calculated and Bland-Altman plots were drawn. The reproducibility of MP was assessed on global, regional and segmental
levels. Thereafter, this analysis was applied in 48 consecutive clinical patients with suspected coronary heart disease (CHD).
ResultsFor the experienced observer the Pearson r for all segments was 0.974 at rest and 0.978 at stress (p < 0.0001), and the repeatability coefficients were 0.145ml/g per min (15.5% of the average) and 0.389ml/g per min (14.9%),
correspondingly. The ICC reflected very good overall reproducibility. The intraobserver and interobserver differences were
small, and the difference between the most and the least experienced observers at stress was 8.5% for the global MP. The clinical
accuracy of the perfusion in the detection of CHD was excellent (positive predictive value 91% and negative predictive value
88%) against invasive angiography.
ConclusionThe results demonstrate high reproducibility of myocardial perfusion quantitation with 15O-labelled water PET using Carimas™. The results support the feasibility of robust analysis and good clinical accuracy.
European journal of nuclear medicine and molecular imaging 04/2012; 36(10):1594-1602. · 4.99 Impact Factor
ABSTRACT: The standard interpretation of perfusion imaging is based on the assessment of relative perfusion distribution. The limitations of that approach have been recognized in patients with multivessel disease and endothelial dysfunction. To date, however, no large clinical studies have investigated the value of measuring quantitative blood flow and compared that with relative uptake.
One hundred four patients with moderate (30%-70%) pretest likelihood of coronary artery disease (CAD) underwent PET imaging during adenosine stress using (15)O-water and dynamic imaging. Absolute myocardial blood flow was calculated from which both standard relative myocardial perfusion images and images scaled to a known absolute scale were produced. The patients and the regions then were classified as normal or abnormal and compared against the reference of conventional angiography with fractional flow reserve. In patient-based analysis, the positive predictive value, negative predictive value, and accuracy of absolute perfusion in the detection of any obstructive CAD were 86%, 97%, and 92%, respectively, with absolute quantification. The corresponding values with relative analysis were 61%, 83%, and 73%, respectively. In region-based analysis, the receiver operating characteristic curves confirmed that the absolute quantification was superior to relative assessment. In particular, the specificity and positive predictive value were low using just relative differences in flow. Only 9 of 24 patients with 3-vessel disease were correctly assessed using relative analysis.
The measurement of myocardial blood flow in absolute terms has a significant impact on the interpretation of myocardial perfusion. As expected, multivessel disease is more accurately detected.
Circulation Cardiovascular Imaging 09/2011; 4(6):678-84. · 5.94 Impact Factor
ABSTRACT: Accelerated flow at the site of flow-limiting stenosis can be detected by transthoracic Doppler echocardiography (TTDE). We studied feasibility and accuracy of sequential coronary computed tomography angiography (CTA) and TTDE in detection of haemodynamically significant coronary artery disease (CAD).
We prospectively enrolled 107 patients with intermediate (30-70%) pre-test likelihood of CAD. All patients underwent CTA using a 64-slice scanner. Using TTDE, the ratio of maximal diastolic flow velocity to pre-stenotic flow velocity (M/P ratio) was measured in the coronary segments with stenosis in CTA. In all patients, the results were compared with invasive coronary angiography, including measurement of fractional flow reserve when appropriate. All analyses were done blinded. TTDE was feasible in 276 of 285 evaluated coronary segments. Significant coronary stenoses were associated with a higher M/P ratio than non-significant stenoses (3.59 ± 1.82 vs. 1.28 ± 0.60, P < 0.001). The optimal M/P ratio for detection of significant stenosis was 2.2 (area under receiver operating characteristic curve 0.92, P < 0.001). Compared with the strategy of CTA alone, sequential CTA and focused TTDE had a better positive predictive value (PPV; 61 vs. 78%) and diagnostic accuracy (93 vs. 96%, P = 0.006) without impairment of the negative predictive value (97 vs. 97%).
Sequential use of CTA and TTDE is feasible for combined anatomic and functional evaluation of coronary stenoses. Compared with coronary CTA alone, addition of TTDE improved PPV for detection of significant CAD.
European heart journal cardiovascular Imaging. 08/2011; 13(1):79-85.
ABSTRACT: To measure intrapericardial fat (IPF), extrapericardial fat (EPF), and myocardial perfusion (MBF) in patients with and without coronary artery disease (CAD), hypothesizing that perfusion is more strongly associated with IPF because it is in direct anatomic contiguity with the myocardium or coronary arteries.
Fat surrounding the heart may increase the risk of CAD and calcification, but little is known about the role of MBF in this relationship. The study included 107 patients with an intermediate likelihood of CAD. Positron emission tomography/computed tomography was used to measure IPF and EPF volumes and coronary artery calcium level, together with MBF at rest and during adenosine-induced hyperemia. Subsequently, all subjects underwent coronary angiography and were grouped for presence/absence of CAD and severity of myocardial hypoperfusion. IPF and EPF levels were higher in men and in patients with CAD (n=85) than in those without CAD (n=22) (P<0.001). EPF was increased regardless of the degree of stenoses (n=45), whereas IPF was selectively increased in subjects with obstructive stenoses (n=40). IPF and EPF levels were both associated with coronary artery calcium scores (R=0.25 and R=0.26, respectively; P<0.02), coronary flow reserve (R=-0.37 and R=-0.38, respectively; P<0.001), and hyperemic MBF (R=-0.36 and R=-0.44, respectively; P<0.0005). Male sex was a strong negative predictor of MBF. After discounting for confounders, myocardial hyperemic perfusion was predicted independently by sex, coronary artery calcium score, and IPF, but not EPF.
CAD is accompanied by augmented fat depots surrounding the heart, which are negatively related to coronary flow hyperemia. Among fat depots, IPF was the only independent predictor of hyperemic MBF, supporting the hypothesis of a direct paracrine/vasocrine effect.
Arteriosclerosis Thrombosis and Vascular Biology 10/2010; 31(1):211-8. · 6.37 Impact Factor
European Journal of Nuclear Medicine 01/2010; · 4.53 Impact Factor