No abstract

A dual-isotope simultaneous acquisition (DISA) single-photon emission tomography (SPET) protocol with fluorine-18 fluorodeoxyglucose ((18)F-FDG) and a technetium-99m labelled flow tracer is attractive because it permits assessment of both myocardial glucose utilisation and flow within a single study. Differences in physical and physiological characteristics between (18)F-FDG and the (99m)Tc-labelled flow tracer, however, may cause differences in myocardial activity distribution between the agents. The aim of this study was to investigate the relation between the myocardial distribution of (18)F-FDG and a (99m)Tc-labelled flow tracer on DISA SPET in comparison with nitrogen-13 ammonia/(18)F-FDG positron emission tomography (PET). Nine normal volunteers without cardiac disease and ten patients with known coronary artery disease (CAD) underwent (13)N-ammonia/(18)F-FDG PET and (99m)Tc-sestamibi/(18)F-FDG DISA SPET. Using a semiquantitative polar map approach, the left ventricular myocardium was divided into nine segments, and relative regional activity was calculated for each segment. A segment was considered to have concordant uptake between (18)F-FDG and flow tracer if the difference in measured regional activity between the tracers was < or =10% of peak activity, and the percentage of concordant segments was calculated for each subject. There was a good overall concordance of myocardial activity between the agents on DISA SPET (84.0%+/-14.8%) in normals, which was comparable to that seen on PET (86.4%+/-14.5%, NS vs DISA SPET). However, the myocardial activity distributions of (18)F-FDG and flow tracer were not identical in that reduced flow tracer activity was seen in the basal segments on DISA SPET in both normals and CAD patients. It is concluded that there is good overall concordance of activity between (18)F-FDG and flow tracer in normal myocardium on DISA SPET, which is comparable to that on PET, supporting the use of combined (99m)Tc-flow tracer/(18)F-FDG imaging for the detection of viable myocardium. However, there is a difference in the myocardial activity distribution between the agents in both normals and CAD patients, the difference being particularly evident in the basal segments. Therefore, careful image interpretation that takes into consideration the different normal activity distribution between the tracers and/or a tracer-specific normal database is necessary for comparison with patient studies.

In conclusion, ECG-gated DISA SPECT provides information on myocardial viability, as well as global and regional LV function, similar to that obtained by PET and MRI.

Gated N-13 NH(3) PET combined with QGS provides information on both global and regional left ventricular function comparable to that obtained by gated Tc-99m perfusion myocardial SPECT in CAD patients.

he assessment of left ventricular (LV) function and volumes, together with myocardial perfusion, is important for prognostic stratification of patients with coronary artery disease (CAD). [1][2][3][4][5] The electrocardiographic (ECG) -gated acquisition technique with perfusion tracers for single-photon emission computed tomography (SPECT) has been established to assess global and regional LV function, and several automated quantitative algorithms, such as the Cedars-Sinai quantitative gated SPECT (QGS), have been developed for this purpose. 6-11 Several recent studies have applied these algorithms to positron emission tomography (PET), 12-16 which has several advantages over SPECT in that it produces high-quality imaging and has the capability of quantitative analysis of perfusion or metabolism. Nitrogen-13-ammonia ( 13 N-NH3) has been widely used for quantification of myocardial blood flow Circulation Journal Vol.69, February 2005 (MBF) in PET studies. [17][18][19][20] Although MBF and LV function should usually be closely related, they may disagree in some circumstances, such as myocardial stunning. Therefore, the integration of MBF and LV function is important for understanding of the pathophysiology of various disease conditions. In this regard, ECG-gated 13 N-NH3 PET is attractive because it enables simultaneous assessment of MBF and LV function, but this promising technique has not been systematically validated in a large patient cohort. Furthermore, the feasibility of assessing regional function has not been previously addressed. The aim of this study was to evaluate the feasibility of ECG-gated 13 N-NH3 PET to assess global and regional LV function in a relatively large cohort of patients with CAD in comparison with conventional left ventriculography (LVG) as the reference technique. Methods Study PopulationThe study group consisted of 54 consecutive patients (51 men, 3 women; age range: 30-85 years, mean age: 62.6± 12.4 years) with CAD documented by coronary angiography. Of these 54 patients, 34 had a previous myocardial infarction. All patients underwent both LVG and gated 13 N-NH3 PET at rest within 2 weeks of each other (mean duration 7.2 days). All patients had normal sinus rhythm, and Methods and ResultsFifty-four patients with CAD underwent gated 13 N-ammonia PET and LVG. The LV end-diastolic and end-systolic volumes (LVEDV, LVESV) and ejection fraction (LVEF) by gated 13 N-ammonia PET were calculated using Cedars-Sinai automated quantitative gated single photon emission computed tomography (QGS) and compared with those obtained by LVG. The regional wall motion (RWM) was visually scored, and compared with that on LVG. There were good correlations between the 2 methods for LVEF, LVEDV and LVESV (R=0.828, R=0.821 and R=0.874 respectively). The RWM assessed by gated 13 N-ammonia PET also agreed well with that by LVG (complete agreement was 70.4%, =0.58). Conclusions Gated 13 N-ammonia PET combined with QGS works reasonably well for the assessment of both global and regional LV function in CAD p...