FEASIBILITY OF SIMULTANEOUS DUAL-ISOTOPE MYOCARDIAL PERFUSION ACQUISITION USING A LOWER DOSE OF SESTAMIBI

The feasibility of simultaneous dual-isotope ii myocardial perfusion i maging was assessed using a ca. 12 mCi dose of technetium-99m sestamib i (MIBI) and ca. 3 mCi thallium-201. Planar and single-photon emission tomographic (SPET) data from 40 patients (41 studies) imaged with bot h a single- and a dual-isotope protocol were analysed. Rest injected T l-201 (pure-Tl) images were acquired using 20% windows at 70 and 166 k eV about 15 min after the Tl-201 injection. Patients were then stresse d, and at peak stress Tc-99m-sestamibi was injected, About 30 min late r Tc-99m data were recorded with a 20% window center at 140 keV, and s imultaneous Tl-201 (dual-Tl) data were recorded with a single 20% wind ow centred at 80 keV. Total myocardial counts based on SPET data in th e dual-Tl images were increased by 18.61%+/-2.91% (SEM) (range: -12.8% to 84.1%) compared to pure-Tl images. Region of interest analysis rev ealed the greater increase in counts in the apical region and the leas t in the lateral wall. Pure Tl and dual-Tl images were visually evalua ted for image quality (IQ) on a five point scale (O=unacceptable to 4= excellent). Dual Tl IQ was lower than that of pure-Tl in 61% of cases, and similar in 37% (12% of the pure-Tl and 41% of the dual-Tl images fell into the 0 and 1 categories). Thallium perfusion abnormalities we re of similar extent in 70% of segments, less severe in 18%, and more severe in 12%. There was an inverse correlation with patient weight, s uch that patients weighing more than 180 Ibs had substantially worse i mages than those below this cutoff value. While dual-tracer images are of lower quality, they are interpretable if the patient is not severe ly overweight.