1. Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology Comparison of coronary flow reserve estimated by dynamic radionuclide SPECT and multi-detector x-ray CT Cecilia Marini PhD, Sara Seitun MD, Camilla Zawaideh MD, Matteo Bauckneht MD, Margherita Castiglione Morelli MD, Pietro Ameri PhD, Giulia Ferrarazzo MD, Irilda Budaj MD, Manrico Balbi MD, Francesco Fiz MD, Sara Boccalini MD, Athena Galletto Pregliasco MD, Ambra Buschiazzo MD, Alice Saracco PhD, Maria Claudia Bagnara PhD, Paolo Bruzzi MD, Claudio Brunelli MD, Carlo Ferro MD, Gian Paolo Bezante MD, Gianmario Sambuceti MD Copyright American Society of Nuclear Cardiology

2. BACKGROUND Recent technical advances in Computed Tomography (CT) and specifically the development of multi-detector (MD) CT scanners have made it feasible to assess, in addition to coronary artery anatomy, regional myocardial perfusion. Furthermore, dynamic CT imaging methods have been developed to estimate coronary flow reserve (CFR) In the present study we aimed to compare estimates of CFR by dynamic SPECT and by dynamic MDCT and relate CFR values to coronary artery anatomy. Copyright American Society of Nuclear Cardiology Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology

3. METHODS A.Study type: Observational Study subjects: Thirty-five patients (29 males, mean age 69 years) with greater than average Framingham risk of CAD, underwent dipyridamole vasodilator stress imaging by means of SPECT and dynamic MDCT. Study endpoints: CFR estimation using dynamic SPECT and dynamic MDCT imaging. Myocardial perfusion findings were correlated with obstructive CAD (>50% luminal narrowing) on CT coronary angiography (CA). Copyright American Society of Nuclear Cardiology Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology

4. RESULTS Copyright American Society of Nuclear Cardiology Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology Correlation of CFR by MDCT and SPECT. The upper panel shows the linear regression of the two techniques in measuring CFR, r2=0.39. The lower panel shows the Bland-Altman plot of the same CFR data. At higher CFR values there is an increasing difference between the two techniques. There is a proportional bias with a relative underestimation of CFR by MDCT in comparison to that by SPECT. CFR= coronary flow reserve.

5. RESULTS Copyright American Society of Nuclear Cardiology Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology Relationship between CFR and coronary artery stenosis severity. Both dynamic SPECT (black) and dynamic MDCT (dashed) shows a progressive decrease of mean estimated CFR from normal vessels to non-obstructive and obstructive coronary stenosis. Only SPECT-derived CFR shows also a significant difference between arteries with non obstructive and obstructive coronary plaques.

6. CONCLUSIONS 1- Mean CFR estimated by SPECT and MDCT in 595 myocardial segments was not different (1.51±0.46 vs. 1.50±0.37, p=NS). 2- Correlation of segmental CFR by SPECT and MDCT was fair (r2=0.39, p<0.001). 3 - Bland-Altman analysis revealed that MDCT in comparison to SPECT systematically underestimated CFR in higher CFR ranges. By CTCA 12 patients had normal CA, 11 had non-obstructive and 12 had obstructive CAD. 4 - CFR by both techniques was significantly higher in territories of normal CA than in territories subtended by non-obstructive or obstructive CAD. SPECT CFR was also significantly different in territories subtended by non-obstructive and obstructive CAD, whereas MDCT CFR was not. 5 - Despite relative underestimation of high CFR values, MDCT CFR shows promise for assessing the pathophysiological significance of anatomic CAD. Copyright American Society of Nuclear Cardiology Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology