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Unlabelled: This was a study to evaluate the posterior cingulate sign in differential diagnosis between Alzheimer's and frontotemporal disease. The impending availability of effective treatment for Alzheimer's disease makes this differential diagnosis important., Methods: Images of 20 patients with clinically confirmed or autopsy-proven (10 patients) Alzheimer's disease and 20 patients with clinically confirmed or autopsy-proven (7 patients) frontotemporal disease were compared with the consolidated images of 20 elderly healthy control subjects. The (99m)Tc-hexamethylpropyleneamine oxime SPECT data on brain blood flow from each patient were compared with the consolidated control image using statistical parametric mapping., Results: Sixteen of 20 patients with Alzheimer's disease showed the posterior cingulate sign in the form of significant blood flow reductions; 1 of 20 patients with frontotemporal disease showed the posterior cingulate sign. That patient's illness has evolved into Alzheimer's disease. The remaining 19 patients were negative for the posterior cingulate sign., Conclusion: When present, the posterior cingulate sign indicates the presence of Alzheimer's disease; it is apparently absent in frontotemporal disease, thus serving as a differential diagnostic sign. It was absent in 3 patients with proven tangle-predominant Alzheimer's disease.

Unlabelled: Occipital lobe perfusion defects have been identified on regional cerebral blood flow (rCBF) SPECT scans of adolescent children and young adults with major depressive disorder (MDD). We reinvestigated a series of rCBF SPECT scans obtained several years ago on drug-naive children with a clinical diagnosis of MDD and on healthy children., Methods: To test whether visually apparent abnormalities in rCBF constitute statistically significant differences between patients, given the relatively small sample sizes, we applied the technique of statistical parametric mapping (SPM)., Results: Two groups of patients were identified: 8 with significant posterior flow deficits in the occipital cortex (Brodmann's areas 18 and 19), usually symmetric, and best visualized on paramedian sagittal sections, and 13 without obvious occipital perfusion deficits but with anterior rCBF deficits in a pattern often described in the literature, attaining statistical significance in the right frontal region. Other localizations in the left frontal and bilateral prefrontal regions did not attain significance, but each localization contained statistically significant maxima (z scores). The scan findings of all 18 healthy children were normal., Conclusion: With the aid of SPM, 2 groups of children with significantly different rCBF behavior were identified. The reason for this difference is not known but should be investigated to determine its possible significance to patients with MDD.

It is important to determine preoperatively which patients can tolerate permanent occlusion of a cervical internal carotid or cerebral artery when such a procedure may be necessary to treat cerebrovascular or neoplastic lesions. Here we report our experience in combining temporary intra-arterial balloon occlusion with concomitant cerebral blood flow imaging in preoperative evaluation of such patients. Forty-two patients with a variety of cerebrovascular and neoplastic lesions underwent trial balloon occlusion of an internal carotid or intracerebral artery. Eight patients developed both neurologic symptoms as well as brain perfusion defects during trial occlusion. Nine others developed only perfusion defects. The remainder were asymptomatic and had negative scans. Brain blood flow imaging during intra-arterial balloon occlusion identified 17 patients potentially at risk for developing postsurgical ischemic deficits. Treatment alternatives to acute arterial sacrifice were developed for these patients.

Myocardial scinitgrams, using 99mTc-stannous pyrophosphate, showed an acute posterior infarction and an abnormally placed left kidney in a 24-year-old hypertensive man; Further study revealed that the kidney was displaced by a mass later proven to be a pheochromocytoma. The latter was the cause of his hypertension and probably instigated the acute myocardial infarction.

Attenuation of photons in single-photon emission tomography (SPECT) makes three-dimensional reconstruction of unknown radioactivity distributions a mathematically intractable problem. Approaches to approximate SPECT reconstruction range from ignoring the effect of photon attenuation to incorporating assumed attenuation coefficients into an iterative reconstruction procedure. We have developed a computer-based simulation method to assess the relative effectiveness of attenuation compensation procedures. The method was used to study four procedures for myocardial SPECT using an infarct-avid radiopharmaceutical, Tc-99m stannous pyrophosphate. Reconstructions were evaluated by two criteria: overall (sum-of-squares) accuracy, and accuracy of lesion sizing. For moderate- to high-contrast studies there were no significant differences among the reconstructions by either evaluation criterion; for low contrast ratios the iterative method produced lower sum-of-squares criterion; for low contrast ratios the iterative method produced lower sum-of-squares error. We conclude that the additional expense of the iterative method is not justified under the conditions of this study. The approach used here is a convenient tool for evaluating specific SPECT reconstruction alternatives.

A four-pinhole longitudinal tomographic system, with collimator and software, was developed for a standard-field portable scintillation camera. This system was used with technetium--99m pyrophosphate (Tc-PPi) to quantify the volume of infarcted myocardium in 27 dogs with experimental myocardial infarcts. These were induced by ligation of the left anterior descending (LAD) or the circumflex coronary artery. Tomographic estimations of scintigraphic infarct size agreed well with postmortem findings when the circumflex group (r = 0.87) and LAD group (r = 0.83) were considered separately, but the correlation fell when the groups were pooled (r = 0.73). Whereas multipinhole tomography extends Tc-PPi infarct sizing capability in animals to include posterior and subendocardial infarcts as well as anterior lesions, the tomographic sections contain enough blur artifacts to lower the sizing accuracy of the method. The main advantage of the technique may well be its ability to aid in detection and location of small myocardial infarcts.

The topographic relationship between the uptake of technetium-99m pyrophosphate (PPi) and myocardial infarction delineated by 2,3,5-triphenyl tetrazolium chloride (TTC) was studied in a canine model of permanent coronary occlusion (24-48 hr). Photographs of TTC staining and scintigraphic images of PPi uptake were planimetered for infarct area. In addition, narrow tissue samples (3 X 10 mm) were taken on both sides of the TTC border and counted for PPi uptake. A significant correlation (p less than 0.001) was found between area of PPi uptake and area of myocardium unstained by TTC (r = 0.84 in epicardium and r = 0.91 in endocardium). The slope relating PPi to TTC for all infarcts was 1.01 +/- 0.11, indicating that variations in infarct size were followed equally by the two techniques. Tissue counting showed the ratio of PPi activity just inside the infarct to activity just outside the infarct to be 9.2 +/- 0.6 (mean +/- s.e.m.). Thus, PPi is distributed topographically in a manner identical to the distribution of irreversibly injured myocardium as delineated by TTC.

We have developed a method by which any two sets of R-wave-synchronized radionuclide images may be registered, color-coded, and displayed in cinematic fashion so that the image sets are superimposed and shown simultaneously in contrasting colors. The technique has been applied to technetium-99m stannous pyrophosphate (Tc-99m PPi) and equilibrium blood-pool images. Gated Tc-99m PPi and gated blood-pool image sets (16 frames per cardiac cycle) were acquired in identical projections. Image sets were then registered, if necessary, and color-coded by a computer algorithm. Our initial experience suggests that this overlay technique may be of value to: (a) detect right ventricular infarction with greater precision; (b) provide a better estimate of anatomic location and circumferential extent of Tc-99m PPi myocardial uptake relative to the ventricular blood pool; and (c) distinguish between segmental contraction abnormalities caused by recent infarction (identified by abnormal Tc-99m PPi uptake) and segmental contraction abnormalities caused by ischemia or previous myocardial infarction.

Myocardial infarct size was estimated by three methods in a canine model, using Tc-99m pyrophosphate at 24 and 48 hr after coronary ligation. A gamma camera provided anterior, LAO, and lateral views, and was then fitted with multipinhole (MPH) and rotating-slanthole (RSH) collimators for tomographic studies, processed by computer to display frontal sections of the chest. Infarct weight was measured postmortem for comparison. All transmural infarcts were detected by all three imaging techniques. RSH tomography was superior to both MPH tomography and planar imaging for the detection of nontransmural infarction. Infarcts as small as 1.0 g were detected. Estimates of infarct volume measured from RSH slices showed an excellent correlation with infarct weight (r = 0.89) and were reproducible within acceptable limits. Estimates on infarct volume measured from MPH slices demonstrated a significantly poorer correlation with infarct weight (r = 0.48, p less than 0.01). Both tomographic techniques may improve infarct visualization by suppressing overlying activity and increasing contrast between infarct and background, but both produce significant blur artifacts that hamper their utilization by inexperienced observers.

Twenty-six patients suspected of having acute myocardial infarction (AMI) underwent myocardial scintigraphy sequentially with 201Tl and 99mTc-stannous pyrophosphate (99mTc-PPi). Of the 26 patients, 24 had AMI documented by enzyme and electrocardiographic changes. Nineteen had transmural and five had subendocardial myocardial infarctions. The remaining two patients had "unstable angina pectoris." The mean time from onset to imaging was 4 days. Of the 24 patients with AMI, 22 had positive 99mTc-PPi scintigrams. In 20 the area of acute myocardial damage appeared to be the same by 99mTc-PPi scintigram as by ECG; in two, the location could not be precisely determined. The two patients with negative 99mTc-PPi scintigrams at the time of combined myocardial imaging had had positive 99mTc-PPi images previously. In all 24 patients, the 201Tl images were abnormal in at least the location suggested by the electrocardiogram. In seven patients, the area of decreased 201Tl activity was grossly equal to the positive area on the 99mTc-PPi images; in 15, the 201Tl defect was definitely larger; and in two, the 201Tl defect appeared slightly smaller. Although the 99mTc-PPi and 201Tl myocardial images provide different information, both are valuable in determining the overall integrity of the myocardium in patients with ischemic heart disease.

The effect of blood flow and site of injection on Tc-99m PPi uptake in acute myocardial infarction was studied in a group of 24 dogs. Temporary (3 hr) and permanent LAO occlusion models were used. Animals with the temporary occlusions showed scintigraphic visualization of the infarcts and reversal of the normal epito-endocardial Tc-99m PPi ratio in contrast to those with permanent coronary occlusions. The data demonstrate that early (within 3 hr) experimental canine myocardial infarcts can be detected with Tc-99m PPi if reflow to the area of infarction is provided. Delayed development of abnormal Tc-99m PPi scintigrams with acute infarction is related primarily to the initial lack of adequate blood flow to the damaged tissue, with subsequent development of adequate collateral flow allowing delivery and uptake of sufficient amount of the radiopharmaceutical for in vivo scintigraphic detection of the damaged area(s).

This study evaluated the accuracy of several noninvasive infarct-sizing techniques in 12 awake, unsedated dogs with multivessel coronary obstructions and acute anterior myocardial infarcts. Estimations of infarct size by scintigraphy with technetium-99m Sn pyrophosphate (Tc-PP), serum creatine phosphokinase (CPK) release, peak serum myoglobin levels by radioimmunoassay, and precordial ECG mapping were compared and correlated with histologic measurements of infarct size. The comparisons indicate that precordial ST segments mapping, serum CPK release measurements and peak serum CPK, peak serum myoglobin, and Tc-PPi myocardial scintigraphy all provide approximate estimates of infarct size in this model. Each technique also has certain important limitations, however, including: (A) precordial mapping is relatively insensitive in the identification of small anterior infarcts, (B) serial serum CPK release measurements when obtained for only 24 hr after infarction tend to underestimate large anterior infarct size, and (C) Tc-PPi myocardial scintigrams may fail to recognize anterior infarcts less than 3 gm in size and may overestimate the size of small predominantly subendocardial infarcts. The findings also show that the closest estimate of histologic infarct size in this model was provided by combining two of the noninvasive techniques (precordial mapping to identify sites with 2 or more millimeters of ST segments elevation and Tc-PPi myocardial scintigrams) rather than by relying exclusively on any one technique alone.

Myocardial cell death due to infarction is accompanied by an influx of calcium ion. The calcium ion seems to localize in crystalline structures that form within mitochondria and resemble hydroxyapatite. Based on this phenomenon 99mTc-stannous pyrophosphate has been successfully used to image myocardial infarcts within 24 hr of infarction and 1 hr following tracer administration both in dogs and patient volunteers. In this report, canine distribution studies of 99m-Tc-pyrophosphate are compared with similar studies with 99mTc-stannous polyphosphate, 99mTc-stannous 1, hydroxy-ethylidene-1, 1-disodium phosphonate diphosphonate), and 18F as sodium fluoride. Pyrophosphate polyphosphate, and diphosphonate are each potentially useful in myocardial infarct imaging but bone uptake of 18F occurs sufficiently early to prevent the use of this radionuclide in infarct scintigraphy.

We have reported previously that technetium-99m heparin (TcH) accumulates in, and allows scintigraphic identification of, damaged canine myocardium occurring with temporary occlusion and reperfusion of the left anterior descending (LAD) coronary artery. A recent modification consists of using heparin from sheep lung, with stannous phosphate as the reducing agent. In 12 dogs with permanent LAD occlusion, six were injected intravenously with TcH (3--6 mCi) at 24 hr after occlusion, and six at 48 hr. Each experimental animal demonstrated relatively high TcH uptake in the left-ventircular infarct region as compared with normal myocardium. The in vivo scintigrams in all animals with gross myocardial infarcts were positive. The results suggest that this modified TcH has value for identifying experimental myocardial infarcts and that the reduced bone uptake, compared with that occurring with Tc-99m phosphates, may be an advantage for scintigraphic infarct detection.

Heparin has been labeled with [99mTc] pertechnetate and its ability to image damaged coronary vessels and myocardium during and following myocardial ischemia has been studied in experimental animals. The data obtained indicate that Tc-99m heparin localizes in damaged myocardium and coronary vessels in canine models of temporary myocardial ischemia and reperfusion and in damaged myocardium during fixed coronary occlusion. Scintigraphic detection of damaged myocardium was possible in both models, but the highest levels of Tc-99m heparin in damaged myocardial tissue were found in those dogs with temporary coronary occlusion and reflow. The data suggest that Tc-99m heparin may be of value as a positive imaging agent when coronary arteries or myocardium are injured and either reperfusion is allowed and/or significant blood flow persists in the damaged area.

Myocardial scintigrams using 99mTc-stannous pyrophosphate (99mTc-PYP) can be used to measure myocardial infarcts produced in dogs by proximal ligation of the left anterior descending coronary artery. Seven dogs had 99mTc-PYP myocardial scintigraphy performed 24--32 hr after ligation of the proximal left anterior artery. In each dog the scintigrams showed increased 99mTc-PYP uptake in the distribution of the artery. The scintigraphically visible areas of infarction, measured using interactive computer-aided techniques, were compared subsequently with independent histologic measurements of myocardial infarct size. Several methods for using the area measurements to estimate infarct size were tested. The most successful method (r = 0.92, p less than 0.01) assumed a linear relationship between the largest scintigraphic infarct area and the histologically determined infarct weight. The results suggest that 99mTc-PYP myocardial scintigrams provide a useful noninvasive method for measuring infarct size in dogs with proximal ligation of the left anterior descending coronary artery.

Twenty-eight dogs with acute anterior myocardial infarcts due to proximal occlusion of the left anterior descending coronary artery (LAD) were studied at various periods following the occlusion to determine: (a) the time course and location of abnormal lipid accumulation after infarction, (b) the degree of muscle-cell injury associated with increased lipid deposition, and (c) whether uptake of fatty acid from the circulating fat pool contributes to lipid accumulation in certain myocardial regions. The findings show that myocardial lipid accumulation begins as early as 6 hr after proximal LAD occulsion. The increased lipid deposition occurs as nonmembrane-bound lipid droplets in muscle cells with and without ultrastructural evidence of irreversible injury. Analysis of tissue uptake of intravenoulsy injected [14C] oleic acid conjugated with albumin revealed relatively selective concentration of label in the peripheral and border regions of the infarct, but occasionally even the central subendocardial portion of the infarct concentrated the fatty acid. Thin-layer chromotography showed that most of the label was associated with the triglyceride fraction when the radiolabeled fatty acid was injected 6 or 24 hr after LAD occlusion. These myocardial cellular and topographical alterations will have to be considered when labeled fatty acids are used for imaging acute myocardial infarcts and/or if attempts are made to identify myocardial fat-laden cells scintigraphically.