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Biomedical subjects

G D Arora

Publications and source records attributed to G D Arora.

6 recordsLinked to original sources
PubMed1994

Tl-201 liver uptake for assessment of jeopardized myocardium during dipyridamole stress testing.

The current study was conducted to determine the significance of Tl-201 liver activity during 4 minute dipyridamole (DP) stress testing. Two groups of subjects were examined: group I subjects (n = 52) had electrocardiographic evidence of left ventricular hypertrophy (ECG-LVH), and group II subjects (n = 114) had no ECG-LVH. Both groups were further divided into four subgroups on the basis of Tl-201 myocardial perfusion scans: 1) no myocardial perfusion defect; 2) transient myocardial perfusion defect; 3) fixed myocardial perfusion defect; and 4) transient plus fixed myocardial perfusion defects. Tl-201 liver, heart, and lung activities were quantified in the immediate anterior planar images. Left ventricular mass was quantified using tomographic short-axis slices. In the no ECG-LVH group, Tl-201 lung-to-heart ratio was significantly increased in subjects having transient, fixed, and transient plus fixed myocardial perfusion defects when compared to no myocardial perfusion defect. Tl-201 lung-to-heart ratio did not increase in the ECG-LVH group of subjects having transient, fixed, and transient plus fixed myocardial perfusion defects. In contrast, Tl-201 liver-to-heart ratio increased in both the ECG-LVH and no ECG-LVH groups of subjects having myocardial perfusion defects when compared to subjects having negative myocardial perfusion scan. Left ventricular mass was increased in ECG-LVH subjects when compared to no ECG-LVH subjects, which might have resulted in increased Tl-201 myocardial uptake and, hence, reduced Tl-201 lung-to-heart ratio in ECG-LVH subjects having myocardial perfusion defects.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Effect of tobacco abuse on pulmonary thallium uptake during exercise myocardial perfusion scintigraphy.

To determine the influence of tobacco abuse on thallium 201 lung uptake during exercise, we examined 185 consecutive subjects with normal myocardial perfusion scans and without electrocardiographic evidence of left ventricular hypertrophy. The subjects were divided into two groups: group 1 subjects (n = 60) had histories of smoking and group 2 subjects (n = 125) were nonsmokers. Eighty-eight percent of group 1 subjects and 92% of group 2 subjects were examined using single-photon emission computed tomography and the remaining patients underwent planar imaging. 201Tl lung and heart activities were quantified from the immediate anterior planar images that were obtained in all subjects and reported as lung to heart ratio (L/H). 201Tl L/H in smokers (0.39 +/- 0.11) was significantly higher (P < 0.05) than in nonsmokers (0.34 +/- 0.06) when subjects who achieved 85% of the target heart rate were compared. In conclusion, 201Tl L/H was higher in smokers than in nonsmokers when subjects who achieved 85% of the target heart rate and had no myocardial perfusion defects were compared.

Exercise Test↗
PubMed1994

Alteration of coronary perfusion reserve in hypertensive patients with diabetes.

This investigation was performed to determine whether diabetes mellitus has an additive effect on diminishing coronary perfusion reserve index in hypertensive patients. Coronary perfusion reserve index, thallium lung uptake, the electrocardiogram and haemodynamic parameters were evaluated by exercise thallium myocardial perfusion scintigraphy. In 18% of hypertensive and 13% of diabetic-hypertensive patients there was evidence of left ventricular hypertrophy on electrocardiogram. The maximum heart rate achieved in hypertensive, diabetic and diabetic-hypertensive patients was significantly lower (P < 0.05) than in control patients. The maximum SBP achieved in hypertensive (210 +/- 40 mmHg) and diabetic-hypertensive patients (216 +/- 36 mmHg) was higher (P < 0.05) than in control patients (186 +/- 32 mmHg). A significantly higher number of diabetic patients (53%) did not achieve the exercise rate pressure product of > 26,000 when compared with control (27%), hypertensive (24%) and diabetic-hypertensive (30%) patients. Coronary perfusion reserve index in hypertensive patients decreased significantly (P < 0.05) when compared with control (no hypertension, no diabetes) patients (1.67 +/- .14 vs. 1.79 +/- .17). Coronary vasodilatory reserve index was also reduced significantly (P < 0.05) in diabetic patients in comparison with controls (1.66 +/- .17 vs. 1.79 +/- .17), and was further reduced in diabetic-hypertensive patients when compared with control patients (1.63 +/- .13 vs. 1.79 +/- .17). Thallium uptake in the lung quantified as thallium lung to heart ratio were comparable in all four groups. The results suggest that diabetes mellitus diminishes the coronary perfusion reserve index in patients with hypertension and therefore many account for the increased cardiovascular morbidity in these patients.

Adult↗
PubMed1984

Regional cerebral blood flow measurements using stable xenon enhanced computed tomography: a theoretical and experimental evaluation.

Several theoretical and practical aspects of regional cerebral blood flow measurements using stable xenon gas and CT are discussed. It is shown that by comparing the enhancement at any time T1 with that at saturation or any other time T2, the need to use arbitrary means to bring the arterial concentration data and the CT enhancement data to the same system of measurement units can be eliminated. If CT is performed continuously during the washin phase, say at intervals of 1 min, least squares analysis of the enhancement data can be used to obtain the best possible estimates for the flow rate constant kappa and the saturation enhancement. However, if only a limited number of scans can be performed, as may be the case in human studies, it is also possible to get a good estimate of kappa from a knowledge of the ratio of the enhancement at any time T1 with that at any other time T2. Combinations of T1 = 2.0 min and T2 = 4.0 min, T1 = 1.0 min and T2 = 6.0 min, or T1 = 2.0 min and T2 = 5.0 min were found to be the most convenient. It is also shown that the end-tidal xenon concentration in the exhaled air can be accurately assessed indirectly by measuring the oxygen, CO2, and water vapor concentrations, thereby eliminating the need for more expensive methods involving the use of a mass spectrometer or a thermal conductivity gas analyzer.

Animals↗