The study compared positron emission tomography/computed tomography (PET/CT) of [(18)F]-2-fluoro-2-deoxy-D-glucose ([(18)F]-FDG) uptake by skeletal muscles and the amount of muscle activity as indicated by surface electromyographic (EMG) recordings when young and old men performed fatiguing isometric contractions that required either force or position control. EMG signals were recorded from thigh muscles of six young men (26 ± 6 yr) and six old men (77 ± 6 yr) during fatiguing contractions with the knee extensors. PET/CT scans were performed immediately after task failure. Glucose uptake in 24 leg muscles, quantified as standardized uptake values, was greater for the old men after the force task and differed across tasks for the young men (force, 0.64 ± 0.3 g/ml; position, 0.73 ± 0.3 g/ml), but not the old men (force, 0.84 ± 0.3 g/ml; position, 0.79 ± 0.26 g/ml) (age × task interaction; P < 0.001). In contrast, the rate of increase in EMG amplitude for the agonist muscles was greater for the young men during the two contractions and there was no difference for either group of subjects in the rate of increase in EMG amplitude across the two tasks. The imaging estimates of glucose uptake indicated age- and task-dependent differences in the spatial distribution of [(18)F]-FDG uptake by skeletal muscles during fatiguing contractions. The findings demonstrate that PET/CT imaging of [(18)F]-FDG uptake, but not surface EMG recordings, detected the modulation of muscle activity across the fatiguing tasks by the young men but not the old men.

Our objective was to compare the accuracy of 3 imaging protocols for the detection of parathyroid adenomas: single-tracer, dual-phase imaging with 99m Tc-sestamibi; dual-tracer, singlephase imaging with simultaneous acquisition of 99m Tc-sestamibi and 123 I images; and dual-tracer, dual-phase imaging with simultaneous acquisition of 99m Tc-sestamibi and 123 I images. Materials: Thirty-seven patients with surgical proof of parathyroid adenomas were evaluated. Three different protocols were derived from a single study in each patient, resulting in an intrapatient intrastudy comparison. The first derived protocol was the conventional dual-phase protocol with 99m Tc-sestamibi consisting of anterior and anterior-oblique pinhole images of the neck at 15 min and 3 h plus parallel-hole images of the neck and upper chest at both imaging times. The second derived protocol was a dual-tracer, single-phase protocol consisting of administration of 123 I followed 2 h later by 99m Tcsestamibi. Fifteen minutes later, anterior and anterior oblique pinhole images of the 99m Tc-sestamibi and 123 I were acquired simultaneously, allowing generation of perfectly coregistered subtraction images. Parallel-hole images of the neck and upper chest were also obtained. The third protocol was the same as the second except that the same imaging protocol was repeated at 3 h. Two experienced nuclear medicine physicians indicated the location of any identified lesion and graded the certainty of diagnosis on a 3-point scale. Results: Thirty-seven patients had 41 parathyroid adenomas. For the 2 observers combined, the localization success rate was 66% for the single-tracer, dual-phase protocol; 94% for the dual-tracer, single-phase protocol; and 90% for the dual-phase, dual-tracer protocol. Both dual-tracer protocols were significantly more accurate than the single-tracer protocol (P , 0.01); there was no significant difference between the 2 dual-tracer protocols. In addition, the degree of certainty of localization was greater with the 2 dual-tracer protocols than the single-tracer protocol (P , 0.001). Conclusion: A dual-tracer, single-phase parathyroid imaging protocol consisting of simultaneous acquisition of 99m Tc-sestamibi and 123 I images with pinhole collimation at 15 min and perfectly coregistered subtraction results in a higher degree of accuracy and a greater degree of diagnostic certainty than the commonly used single-tracer, dual-phase protocol of imaging 99m Tc-sestamibi alone at 15 min and 3 h. The addition of delayed imaging to the dual-tracer protocol did not improve results.

Sixteen patients with biliary atresia and 11 patients with neonatal hepatitis were studied preoperatively with either Tc-99m-diethyl-IDA or TC-99m-diisopropyl-IDA. Two parameters were evaluated: hepatocyte clearance and time to appearance of radioactivity in the intestine. Two observers, using a visual grading system of 1 to 4, gave the 16 patients with biliary atresia a hepatocyte clearance grade of 1.7 +/- 0.6 (mean +/- SD); intestinal radioactivity was not seen through 24 hours. The hepatocyte clearance grade of the 11 patients with neonatal hepatitis was 2.1 +/- 0.9 (mean +/- SD) (p greater than 0.05); intestinal radioactivity was seen in nine of 11 patients (p less than 0.001). Using both parameters, 91% of the patients were classified correctly, 4% were misclassified, and 6% were classified as indeterminate; sensitivity and specificity for biliary atresia were 97% and 82%, respectively. Radionuclide imaging with the newer technetium-99m-labeled hepatobiliary radiopharmaceuticals appears promising for the noninvasive diagnosis of biliary atresia.

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