Nuclear Cardiology: Nuclear Cardiology:

136 Nuclear Cardiology, The BasicsFig. 12-1. Computer screen display of simultaneous movie display of planarERNA images in left anterior oblique (LAO), anterior (ANT), and left lateral(LAT) views. In addition ECG-gated first pass angiocardiography for assessmentof the right ventricle is displayed on the top left. The gains of the gammacamera were appropriately tuned so that the heart occupies about one-third ofthe field of view.Interpretation of ERNA images is, with the exception of ejectionfraction, largely based on visual analysis (Figs. 12-2 and 12-3). Overallquality of the study is determined by adequate labeling of red blood cells,the patient’s weight, and counts emanating from the cardiac chambers.Although high labeling efficiency is important, free Tc-99m-pertechnetateusually is trapped in the thyroid gland and stomach mucosa anddoes not interfere with image interpretation. The most important problemis in obese patients in whom scattered photons significantly degradeimage quality.Statistical Accuracy of Ejection FractionThe accuracy of calculated right ventricular (RV) and left ventricular(LV) ejection fraction (EF) is dependent on count statistics. However,the lower the EF, the greater the counts required for optimal calculation.