Does inadequate exercise lower the accuracy of myocardial perfusion scintigraphy?

The predictive accuracy of exercise myocardial perfusion scintigraphy (EMPS) in detecting coronary artery disease (CAD) in patients who fail to achieve an adequate level of exercise is not clear. This investigation was carried out in order to compare the sensitivity, specificity and accuracy of EMPS in adequate exercise patients with those in inadequate exercise patients. We have retrospectively compared the results of EMPS with coronary angiography (CAG). One hundred and forty-eight patients with both tests within 6 weeks were included. Adequate exercise was defined as > or = 85% maximally predicted heart rate for age. The overall sensitivity and specificity of EMPS to detect CAD were 92.5% (74/80) and 75%, (51/68), respectively. The sensitivity and specificity in adequate exercise patients were 94.1% (32/34) and 67.6% (23/34), whereas those in inadequate exercise patients were 91.3% (42/46) and 82.4% (28/34). The accuracy was 80.9% (55/68) and 87.5% (70/80), respectively. Patients with inadequate exercise had lower sensitivity but higher specificity of EMPS for detecting CAD, and achieved a higher accuracy than those with adequate exercise.

99Tcm-dimercaptosuccinic acid renal scintigraphy for detection of renal cortical defects in acute pyelonephritis: posterior 180 degrees SPECT versus planar image and 360 degrees SPECT.

To evaluate the usefulness of the posterior 180 degrees acquisition technique for renal defects in acute pyelonephritis (APN), a prospective study was conducted using planar imaging, 360 degrees and posterior 180 degrees renal single photon emission computed tomography (SPECT) with 99Tcm-dimercaptosuccinic acid. Sixty subjects with the suspicion of APN were included. The kidneys were divided into three zones: each was graded as positive, equivocal or negative for renal defects. To evaluate inter-observer variation, each study was read in a double-blind fashion by two nuclear physicians. Renal defects were found in 24 patients (31 kidneys and 47 zones) with posterior 180 degrees SPECT, 23 patients (29 kidneys and 44 zones) with 360 degrees SPECT (McNemar's test, P = 0.375 for zones) and 15 patients (16 kidneys and 24 zones) with planar image (P = 0.001 for zones, vs 180 degrees and 360 degrees SPECT). The proportion of positive agreement for posterior 180 degrees and 360 degrees SPECT between readers for the presence of renal defects was 0.81 and 0.62, respectively, whereas the proportion of negative agreement was 0.92 and 0.87, respectively. Both posterior 180 degrees and 360 degrees SPECTs significantly detected more renal defects than planar imaging. The detectability of renal defects in APN by posterior 180 degrees renal SPECT was equal to 360 degrees SPECT but inter-observer agreement was better.

Posterior 180 degrees 99mTc-dimercaptosuccinic acid renal SPECT.

UNLABELLED: As a result of a high percentage of hypoactive upper poles of kidneys in traditional 99mTc-dimercaptosuccinic acid (DMSA) SPECT, a prospective study was conducted using 180 degrees acquisition technique compared with 360 degrees to minimize tissue attenuation. METHODS: Anterior 180 degrees, posterior 180 degrees and 360 degrees renal SPECT images were obtained simultaneously using a dual-head camera. Forty-one subjects without renal disease and 16 subjects with 21 cortical defects were included in this study. The total counts of the raw data in the anterior 180 degrees, posterior 180 degrees and full 360 degrees were calculated. Small regions of interest were drawn over the cortex of the kidney on coronal and reoriented sagittal slices. Quantitative evaluation of regional activity was performed on the same frames in all three acquisition methods. RESULTS: Comparison of the total renal counts between the anterior and posterior 180 degrees data showed reduced counts in the anterior 180 degrees data collection (P < 0.01). Visual evaluation of the reconstructed images from anterior 180 degrees, posterior 180 degrees and full 360 degrees data collection showed the best image uniformity in the posterior 180 degrees image. The upper/lower pole ratio in the posterior 180 degrees renal SPECT images increased significantly in comparison to full 360 degrees renal SPECT images (P < 0.01) and anterior 180 degrees SPECT images (P < 0.01). The renal defects were more clearly visualized in the posterior 180 degrees renal SPECT images than the full 360 degrees renal SPECT images. The defect/normal cortex ratios in the posterior 180 degrees renal SPECT images were much lower than those from the full 360 degrees SPECT images (P < 0.01) and those from the anterior 180 degrees SPECT images (P < 0.01). CONCLUSION: The posterior 180 degrees acquisition technique can avoid the problem of hypoactive upper pole and can be less time consuming in 99mTc-DMSA SPECT images. It also provides superior lesion contrast in the clinical evaluation of patients with renal scarring.