[201Tl myocardial scintigraphy and 13N-NH3 positron computed tomography in evaluating myocardial blood flow]

The early distribution of thallium-201 (Tl-201) is related to blood flow within the limits of the physiological range. We examined the ratio of myocardial uptake of Tl-201 to the total dose administered at rest and during exercise, in order to assess myocardial blood flow. The usual dose of Tl-201 (2-3 mCi) was diluted to 20 ml of normal saline and 15 ml were injected intravenously as a bolus. Subsequently the remaining 5 ml were injected in the same manner. Myocardial Tl-201 uptakes after the first dose were comparable to those of the second dose at rest when myocardial uptake immediately before the second injection was subtracted and multiplied by 3 (r = 0.98). This technique was applied during exercise to evaluate coronary reserve. Symptom-limited exercise was performed using a sitting ergometer and the first dose of Tl-201 was administered. After the routine scintigraphy with multiple views was completed, a second dose was given at rest. Myocardial uptake was greater during exercise than at rest by 32.6 +/- 15.1% (mean +/- SD) in 18 normal subjects. This was significantly greater than that of 20 patients with coronary artery disease (5.8 +/- 15.3%; p less than 0.005). Tl-201 scintigraphy has inherent limitations as to its quantitation, while positron scintigraphy using 13N-NH3 has some advantages for calculations. Percent myocardial uptake of 13N during exercise was practically equal to that at rest in six normal subjects (97.1 +/- 25.0%), but it was slightly reduced in patients with coronary artery disease (90.1 +/- 18.2%).(ABSTRACT TRUNCATED AT 250 WORDS)