PET/CT: Challenge for Nuclear Cardiology

Increased sensitivity of LSO-based PET systems is demonstrated in these dynamic series after injection of 555 MBq of ¹³N ammonia. The 3 top rows show long- and short-axis images of tracer uptake using conventional PET scanner (ECAT EXACT; Siemens). The 3 bottom rows show similar protocol with LSO-based system (Biograph 16; Siemens). Note increased signal-to-noise ratio and improved delineation of cardiac structures during 10-s frames in PET/CT data.

Influence of respiratory gating on cardiac motion is demonstrated in this ¹³N-ammonia study. With acquisition time of 10 min after tracer injection, list-mode data from 2 to 10 min were charted by histogram into 6 respiratory and 2 cardiac cycles. Images show end-diastolic frames in end inspiration and end expiration. Approximated, most apical position in both respiratory states is marked with yellow line. Maximal spatial difference is 8 mm. LA = left atrium; LV = left ventricle; RA = right atrium; RV = right ventricle.

Example of PET images attenuation corrected by misaligned CT image with artifacts in anterolateral wall of left ventricle. Artifacts resulted from motion associated with deep breathing of patient during CT scan. Resulting AC map is misaligned with PET emission data. Incorrect AC results in artifactual defects most commonly in anterolateral wall. LA = left atrium; LV = left ventricle; RA = right atrium; RV = right ventricle.

Application of emission-driven AC. Initial data showed significant mismatch between PET and CT data used for AC in patient without regional perfusion defects. Apparent reduced tracer uptake in anterolateral segments is clearly visible in fused image display and in polar map (top). On basis of assumption that tracer uptake (even if reduced) can be emitted only from cardiac tissue, attenuation map was modified and image reconstruction repeated, resulting in substantial recovery of tracer uptake. Ant = anterior; Inf = inferior; Lat = lateral; Sep = septal.