Myocardial distribution of 18F-FDG and 99mTc-sestamibi on dual-isotope simultaneous acquisition SPET compared with PET

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.

Imaging Techniques in Nuclear Cardiology for the Assessment of Myocardial Viability

“…Direct comparison of the perfusion tracers 99m Tc-sestamibi/FDG DISA SPECT and 13 N-ammonia PET are scarce. Only Matsunari et al published a small study about the concordance and discordance of 99m Tc-sestamibi/ FDG DISA SPECT and 13 N-ammonia/FDG PET in 10 patients with CAD, by using the difference between the perfusion tracer and 18 FDG of both techniques [133]. They found a good overall concordance between the activity distribution of FDG and flow tracers of both techniques.…”

“…As with PET studies, metabolic activity measured by FDG SPECT is generally interpreted in combination with a flow tracer. For this purpose, a dualisotope simultaneous acquisition (DISA) SPECT protocol with FDG and 99m Tc-perfusion tracer is attractive because it enables assessment of myocardial glucose utilization and perfusion in a single study ( Figure 4) [128,129,133]. DISA SPECT shortens the duration of procedure, with the advantage of an identical geometric registration of Figure 4.…”

Optimal imaging of patients with ischaemic heart failure

“…FDG is a tracer for PET imaging, but can also be used in conjunction with conventional gamma cameras using ultra-high energy collimators [11]. A recent study showed an overall good agreement between 99m Tc-sestamibi/FDG DISA SPECT and PET for the assessment of myocardial viability in patients with severe left ventricular dysfunction [12].…”

Influence of Positron Emitters on Standard -Camera Imaging

“…Additionally, cardiac dual-isotope SPECT imaging involving a PET radionuclide has been described in several papers (8)(9)(10)(11)(12). Two of these studies (8,12) included a comparison of 99m Tc-tracer imaging with and without the presence of 511 keV by scanning the same subjects for 99m Tc-sestamibi/tetrofosmin twice, before and after 18 F-FDG injection.…”