Brenda A. McSherry

Ultrasound attenuation of the Os calcis in women with osteoporosis and hip fractures

SummaryBone ultrasound attenuation of the calcaneus, and vertebral and femoral bone density measured by dual photon absorption were determined in 22 women with osteoporosis, 10 women with hip fractures, and 29 normal, age-matched controls to determine the utility of the ultrasound technique as an indicator of axial osteopenia. Vertebral and femoral neck density and bone ultrasound attenuation were significantly decreased (P<0.01) in the women with osteoporosis and those with hip fractures. The sensitivity and specificity of bone ultrasound attenuation was 80% at a value of 50 dB/MHz. At 90% specificity the sensitivity of bone ultrasound attenuation was 65%. The results of this pilot study suggest that ultrasound attenuation, a safe, simple, and radiation-free procedure, may be utilized as an indicator of decreased axial bone mass.

Diagnostic value of a new myocardial perfusion agent, teboroxime (SQ 30,217), utilizing a rapid planar imaging protocol: Preliminary results

Technetium-99m-labeled agents have advantages over thallium-201 in terms of photon statistics, cost and clinical availability. They have been suggested as an alternative to thallium for myocardial perfusion imaging. Teboroxime is a new boronic acid adduct of technetium dioxime (BATO) compound that demonstrates favorable characteristics in preliminary studies. With use of a novel (seated) patient positioning technique and a rapid dynamic acquisition protocol, 30 patients underwent planar imaging with teboroxoime while at rest and after maximal treadmill exercise. Postexercise scans were completed in an average time (mean +/- SD) of 4.4 +/- 1.6 min, with 4.8 +/- 1.5 min for the views at rest. These results were compared with coronary arteriography or thallium scintigraphy after treadmill exercise, or both. Diagnostic agreement (abnormal versus normal) was present in 28 of the 30 patients (p less than 0.001). Regarding physiologic assessment as compared with thallium scintigraphy, the finding of infarction and ischemia was concordant in 89% and 86% of patients, respectively. This report describes the initial use of teboroxime with a rapid dynamic planar imaging technique, resulting in a high correlation with exercise thallium scintigraphy. Delayed postexercise images obtained 5 to 10 min after exercise demonstrated rapid disappearance of exercise-induced defects noted on the initial (0 to 5 min) postexercise views. The rapid differential washout with teboroxime has not been previously described and the possible clinical significance is discussed.

A method of simultaneous dual-radionuclide cardiac imaging with technetium 99m and thallium 201. I: Analysis of interradionuclide crossover and validation in phantoms.

BackgroundSimultaneous dual-radionuclide technetium 99m/thallium 201 scintigraphy can potentially produce perfectly aligned stress and rest images in less time than conventional protocols. However, interradionuclide crossover limits diagnostic accuracy. Accordingly, we evaluated99mTc and201Tl crossover in line and heart phantoms.Methods and Results99mTc crossover in the201Tl imaging window constituted as much as one half of the counts in the99mTc window, varied significantly with attenuation, and was spatially incoherent.201Tl crossover was relatively small, less variable, and spatially similar to the primary image. Based on these findings, the following simultaneous dual-radionuclide99mTc/201Tl method was developed, and validated in line and heart phantoms. The99mTc source is imaged first into dual201Tl/99mTc windows, followed by201Tl administration and dual-radionuclide imaging. The single-radionuclide99mTc image in the201Tl window is count-normalized for acquisition time and then subtracted from the dual-radionuclide201Tl image to specifically correct for99mTc crossover. Image quality of the corrected dual-radionuclide201Tl images approached their single-radionuclide counterparts. Correction for201Tl crossover was relatively unimportant.ConclusionSimultaneous dual-radionuclide99mTc/201Tl myocardial scintigraphy is feasible with99mTc crossover correction specific to each acquisition. The proposed dual-radionuclide99mTc/201Tl method and the principles on which it is based can be applied to a broad range of dual-radionuclide pairs.

Comparison of 3- versus 6-minute infusions of adenosine in thallium-201 myocardial perfusion imaging

Adenosine thallium stress testing has a demonstrated utility in the detection of coronary artery disease. The optimal dose for diagnostic efficacy with minimal side effects has not been critically evaluated. A randomized 3- and 6-minute infusion of adenosine (140 micrograms/kg/min) was performed in 11 subjects. Subjects reported more side effects during the 6-minute infusion protocol (p < 0.05). Hemodynamic changes were not different during either infusion duration. All dysrhythmias began within 2 minutes and therefore the duration of the infusion did not influence their occurrence. Segmental comparison of the stress images demonstrated an 89% agreement. Delayed scans demonstrated a 79% agreement. There was a higher incidence of redistribution following the 6-minute infusion (p = 0.014). We conclude that when side effects necessitate the discontinuation of a 6-minute adenosine infusion, a diagnostic test can still be achieved if 2 to 3 minutes of adenosine have been administered before the thallium injection; however, the amount of viable myocardium may be underestimated.

Sequential teboroxime imaging during and after balloon occlusion of a coronary artery

OBJECTIVES We sought to assess whether sequential teboroxime imaging can rapidly evaluate vessel patency and identify the coronary artery occluded in patients undergoing balloon occlusion of a coronary artery. BACKGROUND Intravenous thrombolytic therapy results in successful reperfusion of the infarct-related artery in only 50% to 80% of cases. A noninvasive technique to serially evaluate coronary perfusion would identify patients who might benefit from other interventions such as emergency percutaneous transluminal coronary angioplasty, coronary artery bypass grafting or increased intensity of thrombolytic therapy. METHODS Teboroxime scans were performed during balloon occlusion in 15 nonconsecutive patients undergoing angioplasty of a major coronary artery. Equivalent views were repeated after successful angioplasty. RESULTS The mean time between balloon occlusion and reperfusion imaging was 1.6 +/- 0.6 h. The mean number of defects decreased significantly from 4.13 +/- 1.01 during balloon occlusion to 0.27 +/- 0.44 after reperfusion (p = 0.0006). There was a 30% decrease in the defect/normal zone count/pixel ratios during balloon occlusion and normalization of these ratios after reperfusion (p = 0.0006). The scans correctly identified all nine left anterior descending coronary artery occlusions and both right coronary artery occlusions. One of the four left circumflex coronary artery occlusions was incorrectly identified as a right coronary artery occlusion by scan criteria. Overall, the scans correctly identified the occluded artery 93% of the time (kappa = 0.88). The scan was 100% accurate for distinguishing occlusion of the left anterior descending coronary artery (n = 9) from occlusions of the left circumflex or right coronary artery (n = 6). CONCLUSIONS We believe that this is the first clinical study to demonstrate that sequential planar imaging with teboroxime can 1) rapidly detect acute coronary artery occlusion and reperfusion, and 2) identify the occluded coronary artery. A trial comparing rapid sequential teboroxime imaging with coronary angiography in patients receiving thrombolytic therapy for acute myocardial infarction is warranted.

Rapid redistribution of teboroxime

Teboroxime, a new technetium-99m-labeled myocardial perfusion tracer, possesses rapid myocardial kinetics. Whereas this agent is routinely imaged after separate stress and rest injections, experimental data suggest that teboroxime may rapidly redistribute in the myocardium. Accordingly, we assessed 68 exercise teboroxime scintigrams in which immediate poststress, early delay (5 minutes) and rest images were acquired. Studies were categorized visually as ischemia, infarct or normal based on conventional stress-rest comparison. They were then evaluated for rapid teboroxime redistribution by comparing the stress and early delay images. Quantitative analysis was then performed on 537 myocardial segments. Segments were grouped as ischemia, infarct or normal based on stress-rest comparison, and the degree of normalization of stress-induced defects in the early delay images was determined for each group. Rapid teboroxime redistribution was observed in 20 of 46 scintigrams (48%) considered ischemic, and in 2 of 7 and 2 of 15 scintigrams deemed infarct and normal, respectively. The mean segmental intensity ratio (defined relative to the opposite segment) improved from 0.79 at stress to 0.88 at early delay (p < 0.005) in the group with ischemia and from 0.83 to 0.87 in the group with infarction. The most likely explanation for rapid redistribution of teboroxime is differential washout from the myocardium between areas of disparate flow. It is concluded that rapid redistribution of teboroxime occurs within 5 minutes of a stress injection, giving rise to potentially useful clinical information. Thus, teboroxime imaging should be completed expeditiously to detect areas of relative hypoperfusion.

Use of sequential teboroxime imaging for the detection of coronary artery occlusion and reperfusion in ischemic and infarcted myocardium

Nine Yorkshire pigs underwent coronary artery occlusion followed by 2 hours of reperfusion. In five pigs (group A) the occlusion time was 15 minutes and in four pigs (group B) the occlusion time was 1 hour. Teboroxime was administered and images were acquired at baseline, and following occlusion and reperfusion. Infarct size was determined by triphenyl tetrazolium staining. Normalized regional myocardial blood flow, as determined by radio-labeled microspheres, was 0.26 +/- 0.09 following occlusion and 0.83 +/- 0.07 following reperfusion (p < 0.01). Significant differences were found between the defect/normal scan ratios on the baseline and occlusion scans (1.0 +/- 0.03 vs 0.54 +/- 0.10; p < 0.01) and between the occlusion and reperfusion scans (0.54 +/- 0.10 vs 0.97 +/- 0.17; p < 0.01). This is the first study to demonstrate that rapid sequential teboroxime imaging can detect acute coronary occlusion and reperfusion to both ischemic and infarcted myocardium. Teboroxime may be an excellent tracer for the early evaluation of infarct artery patency in patients receiving thrombolytic therapy.