Theodore R. Simon

Reverse redistribution of thallium-201 detected by SPECT imaging after dipyridamole in angina pectoris

Reverse redistribution refers to a thallium-201 perfusion defect that develops or becomes more evident on delayed imaging compared with the initial image immediately after stress. To determine the diagnostic importance of reverse redistribution after intravenous dipyridamole, thallium-201 single photon emission computed tomography and quantitative coronary arteriography were performed in 90 men with angina pectoris. Of the 250 myocardial segments analyzed, reverse redistribution was present in 17 (7%). Minimal coronary cross-sectional area in proximal vessel segments was less than or equal to 2.0 mm2 more often in regions with transient perfusion abnormalities than in regions with reverse redistribution (66 vs 29%, p less than 0.05). Compared with regions exhibiting transient perfusion abnormalities, regions with reverse redistribution had larger proximal arterial diameters (1.9 +/- 1.1 vs 1.3 +/- 1.1 mm, p less than 0.001) and cross-sectional areas (3.9 +/- 3.1 vs 2.2 +/- 2.6 mm2, p less than 0.001). Coronary artery dimensions and relative stenosis severity did not differ between those regions with normal perfusion and those with reverse redistribution. Reverse redistribution detected by thallium-201 single photon emission computed tomographic imaging after dipyridamole is uncommon, appears to occur as frequently in normal subjects as in patients undergoing coronary arteriography and does not indicate the presence of severe coronary artery disease.

Comparison of dipyridamole-Doppler echocardiography to thallium-201 imaging and quantitative coronary arteriography in the assessment of coronary artery disease

This study was undertaken to determine whether Doppler measurements of systolic aortic and diastolic mitral blood flow velocities could reliably detect the presence of reversible myocardial perfusion defects during intravenous dipyridamole-thallium-201 imaging. In addition, the ability of dipyridamole-Doppler echocardiography to predict the presence of significant coronary artery disease (CAD) was evaluated. Baseline and post-dipyridamole Doppler studies were performed in 10 normal control subjects and 23 patients with CAD. Aortic peak velocity and acceleration increased from baseline to post-dipyridamole in normal subjects by 0.07 +/- 0.07 m/s (p = 0.016) and 2.1 +/- 2.0 m/s2 (p = 0.009), respectively. The ratio of early to late peak transmitral velocities decreased slightly in normal subjects, by 0.18 +/- 0.72 (difference not significant), whereas the ratio of early to late transmitral velocity-time integrals increased by 0.07 +/- 0.93 (difference not significant). The response of aortic velocity and acceleration to intravenous dipyridamole was not significantly different between normal subjects, patients without reversible thallium-201 perfusion defects and patients with reversible thallium-201 perfusion defects. Furthermore, only 3 of 14 subjects with reversible thallium-201 perfusion defects had abnormal (greater than 2 standard deviations from the mean) responses of aortic velocity or acceleration to intravenous dipyridamole. No patient had an abnormal response of the early to late mitral peak velocity ratio. In addition, the response of Doppler aortic and mitral indexes to intravenous dipyridamole was not able to identify the presence of significant CAD as assessed by quantitative coronary arteriography.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of thallium-201 single-photon emission computed tomography after intravenous dipyridamole using different quantitative measures of coronary stenosis severity and receiver operator characteristic curves

The presence of significant coronary artery disease in individual vessels was assessed using thallium-201 single-photon emission computed tomography (SPECT) after intravenous dipyridamole. Coronary angiograms were analyzed using quantitative computer-assisted techniques in 81 men patients. Eleven men with a less than 3% probability of coronary artery disease were used as a control population. Three definitions of a hemodynamically significant coronary stenosis were studied independently: (1) a greater than 50% luminal diameter narrowing; (2) an absolute cross-sectional area less than or equal to 2.0 mm2; or (3) a greater than or equal to 70% cross-sectional area obstruction. Myocardial perfusion after dipyridamole was analyzed using the quantitative (polar map) method in 213 regions from the group with known coronary anatomy and using 33 regions from the group with a low likelihood of disease. Receiver operating characteristic curves were used to define the best cut-off point for the discrimination between normal and abnormal perfusion. When related to each of the three quantitative angiographic criteria, the optimum balance between sensitivity and specificity occurred at a defect size of greater than or equal to 8% for the left anterior descending artery, greater than or equal to 4% for the circumflex artery, and greater than 0% for the right coronary artery. Using a luminal diameter narrowing of greater than 50% to define the presence of significant coronary artery disease, these corresponded to respective sensitivities and specificities of 0.82 and 0.76 for the left anterior descending artery, 0.71 and 0.71 for the circumflex artery, and 0.76 and 0.82 for the right coronary artery. Thus analysis of receiver operator characteristic curves provides a means to define abnormalities for the SPECT polar map program after dipyridamole stress. Different definitions of coronary stenosis significance as determined by quantitative angiography did not substantially alter the results of the thallium imaging data and thus suggest that these definitions are functionally similar.

Regional cerebral function and blood flow: Complementary single photon emission computed tomography of the brain using xenon-133 and [123I]iodoamphetamine

Regional cerebral function and blood flow can be imaged using isopropyl[123I]iodoamphetamine (IMP), or 133Xe (DSPECT), respectively. Both of these essentially non-invasive, quantitative, methods are suitable for many nuclear medicine laboratories. This study assessed the in vivo information about intracerebral disease provided by IMP and DSPECT techniques to determine the optimal diagnostic use of these modalities. Single photon emission computed tomograms of 53 subjects were acquired using similar displays for IMP and DSPECT data. Lobar tracer distributions were graded by three experienced observers and analyzed using a kappa statistic to eliminate chance agreements. Overall, both IMP and DSPECT had similar patterns. However, while similar, one or the other technique often displayed abnormalities not present on both. Although technical factors may account for some differences between the modalities, a case of arteriovenous malformation proves that discordant findings can result directly from tracer localization properties. Thus at least some discordances provide truly complementary diagnostic information lacking in either single study taken alone.

Nuclear medicine studies of aging--V. Uptake of 67Ga and 111In in the femoral vessels.

Fifty-nine males who had gallium-67-citrate or indium-111-oxine WBC scintigraphy (Ga/In) had the images reviewed to determine if increased activity was present in the femoral vessels and, if so, whether this was age related. The 59 subjects showed an age-associated increasing bilateral uptake (13% of 15 patients younger than 40 years, to 71% of the 7 who were older than 69 years). The combined unilateral and bilateral femoral uptake rose from 27% in those under age 40, to 86% in those over age 69. The group of 59 males included 30 (51%) who had bone scintigraphy with 99mTc-MDP within 3 months of the Ga/In examination. These men showed the expected increase in femoral vessel 99mTc-MDP uptake with age. Femoral vessel activity was more commonly observed with 99mTc-MDP than with Ga/In. Thus both Ga/In and 99mTc-MDP accumulate more frequently in the femoral vessels with advancing age. Ga/In displays this age-related phenomenon to a lesser extent than 99mTc-MDP.

An inexpensive approach to improving data derived from single photon emission computed tomography

Abstract The issue of inadequate solid standards for correcting nonuniformity in single photon emission computed tomography was addressed. Controlled, complex, motion of commercially available cobalt-57 standards was found to enhance the perceived nonuniformity of the standard and to minimize the effects of any local flaws. This maneuver provides a better standard than a refillable liquid phantom without the problems inherent in radioactive liquid standards which include: phantom deformation, poor mixing, absence of retrospective verification, accidental contamination and substantial handling requirements.