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Biomedical subjects

I D Greenberg

Publications and source records attributed to I D Greenberg.

7 recordsLinked to original sources
PubMed1992

Quantification of walking exercise required for improvement of dipyridamole thallium-201 image quality.

Dipyridamole 201Tl imaging is an accepted diagnostic procedure for the evaluation of patients unable to perform adequate treadmill exercise, but is limited by high infradiaphragmatic activity. While recent studies have shown that the addition of exercise reduces this activity, the amount of exercise needed to effect such an improvement is uncertain. To prospectively evaluate the amount of walking exercise required to produce improvement in image quality, 120 patients were randomized to either a control group receiving dipyridamole alone, or to dipyridamole supplemented with one of four exercise protocols. Ratios of heart-to-liver and heart-to-adjacent infradiaphragmatic activity were generated from anterior images acquired immediately following the test. Heart-to-total infradiaphragmatic activity was also graded semiquantitatively. Results showed improved target-to-background ratios as well as semiquantitative assessment of image quality for dipyridamole supplemented with exercise as compared to dipyridamole alone. No difference was seen between walking in place and Bruce treadmill exercise at Stage 0 or 0.5. A trend towards higher values was seen with Bruce Stage 1 exercise supplementation, but this did not reach statistical significance. No significant complications occurred during the study. We conclude that 3 min of walking exercise is a safe and effective means of improving the quality of dipyridamole 201Tl images.

Adult↗
PubMed1991

Reference range determination: the problem of small sample sizes.

The process of developing and validating a quantitative test includes determination of a reference range. Traditionally this has been taken as the mean +/- 2 standard deviations for a random sampling from a reference population. However, this method fails to recognize the substantial variability in the sample mean and standard deviation for the small sample sizes frequently encountered in nuclear medicine. A new approach, which involves calculating confidence intervals for the upper and lower bounds of the traditionally defined range, recognizes three ranges of values: normal, indeterminate, and abnormal. The principles of this approach are illustrated using differential renal function in twelve renal transplant donors. The 99mTc-DTPA differential uptake between 1 and 2 min gave a traditionally-defined single-kidney range of 50% +/- 8%, whereas with our method the normal range would be 50% +/- 6% with indeterminate ranges of 37%-44% and 56%-63%. These values are consistent with the wide variation in reference ranges reported in the literature, and suggest that much of this variability may be a statistical artifact resulting from inadequate sample sizes. A nomogram has been derived that permits the power of the reference range determination to be easily calculated from the sample size. Analysis of the effect of sample size on the accuracy of the upper and lower bounds of the reference range is advocated whenever small reference populations are used.

Humans↗
PubMed1991

Effect of exercise supplementation on dipyridamole thallium-201 image quality.

To determine the effect of different types of exercise supplementation on dipyridamole thallium image quality, 78 patients were prospectively randomized to one of three protocols: dipyridamole infusion alone, dipyridamole supplemented with isometric handgrip, and dipyridamole with low-level treadmill exercise. Heart-to-lung, heart-to-liver, and heart-to-adjacent infradiaphragmatic activity ratios were generated from anterior images acquired immediately following the test. Additionally, heart-to-total infradiaphragmatic activity was graded semiquantitatively. Results showed a significantly higher ratio of heart to subdiaphragmatic activity in the treadmill group as compared with dipyridamole alone (p less than 0.001) and dipyridamole supplemented with isometric handgrip exercise (p less than 0.001). No significant difference was observed between patients receiving the dipyridamole infusion, and dipyridamole supplemented with isometric handgrip exercise. We conclude that low-level treadmill exercise supplementation of dipyridamole infusion is an effective means of improving image quality. Supplementation with isometric handgrip does not improve image quality over dipyridamole alone.

Adult↗
PubMed1990

Diagnostic thyroid procedures and corresponding radiation doses in Manitoba: 1981-1985.

Data on nuclear medicine thyroid examinations performed in Manitoba (population 1 million) from 1981-1985 were collected, with more detailed demographic data obtained on 1,100 consecutive patients between June 1987 and January 1988. An average of 2,081 patients were examined per year, 81% female and 19% male, representing 8.4% of all nuclear medicine procedures. Typical administered activity and associated HE per patient were 238.0 MBq and 1.5 mSv for 99mTc, 7.4 MBq and 1.2 mSv for 123I, and 0.33 MBq and 3.9 mSv for 131I. Based on NCRP risk estimates with explicit corrections for age, sex, and radionuclide used, it is estimated that the rate of thyroid cancer induction is unlikely to exceed 0.56 y-1, of which about 10% would be fatal. This estimate is about a factor of 4 less than that generated using more generally applicable radiation protection risk estimates averaged over both sexes and all ages in the general population. The replacement of 131I with the present mix of radiotracers used for thyroid evaluation has resulted in a reduction of the estimated population detriment by a factor of 3.6.

Adolescent↗