BACKGROUND:Assessment of viability of myocardium after an ischemic insult is an important clinical question that affects decisions pertaining to potential revascularization. The results of contrast left ventriculograms and coronary angiography were compared to positron emission tomography (PET) in 64 patients with coronary artery disease and reduced left ventricular function.HYPOTHESIS:The study was undertaken to determine the relative utility of the invasive studies in the assessment of viability.METHODS:Right anterior oblique ventriculograms were assessed for hypokinesis, akinesis, or dyskinesis in six segments. The PET scans were assessed for viability by visual estimation of flourodeoxyglucose (FDG) uptake in six segments that corresponded to the segments analyzed on the ventriculograms.RESULTS:Of a total of 373 segments successfully analyzed by PET, 272 were judged to be viable (normal or hypokinetic) by contrast ventriculography. Of these, 253 (93%) were considered viable by PET. Of 177 segments deemed either normal or mild-to-moderately hypokinetic by ventriculography, 170 (94%) were viable by PET. Of 95 severely hypokinetic segments, 83 (84%) were viable by PET. Of 79 akinetic segments, 44 (56%) were considered viable by PET. For segments that were dyskinetic and thought to be nonviable by ventriculography, 19 of 22 (86%) were also considered nonviable by PET. For 294 segments for which a determination on viability was made based on the presence of wall motion on the ventriculogram (normal, hypokinetic, ordyskinetic; not akinetic), there was excellent agreement with PET (93%; p < 0.001). In 49 patients there was akinesis in no more than one segment in either the anterior or inferior territories, indicating the potential for assessment of viability by ventriculography in at least two of three segments in each territory. Coronary anatomy was analyzed to assess whether coronary patency could help in assessing viability. Segments supplied by patent arteries were more likely to be viable by PET than segments supplied by occluded arteries (p < 0.001). Akinetic segments were more likely to be supplied by occluded arteries (56 vs. 23, 72%). Dyskinetic segments were predominantly nonviable by PET (86%) and were usually supplied by occluded arteries (77%).CONCLUSION:In patients in whom the assessment of viability is clinically relevant, the presence of systolic inward motion on the contrast left ventriculogram correlates well with segment viability by PET, while outward or dyskinetic movement correlates well with nonviability. Thus, the use of PET to assess viability in many patients may be unnecessary.

UNLABELLED:The cell-membrane folate receptor is a potential molecular target for tumor-selective drug delivery, including radiolabeled folate-chelate conjugates for diagnostic imaging. We report here the initial clinical study of such an agent, (111)In-diethylenetriaminepentaacetic acid (DTPA)-folate, evaluated for diagnosis of ovarian malignancy.METHODS:Thirty-five women were enrolled in a phase I/II clinical study, with 33 completing the surgical follow-up required by the study protocol for definition of disease status. Patients either had a pathologically proven malignancy or were scheduled for surgery for suspected new ovarian cancer (n = 26), recurrent ovarian cancer (n = 5), or endometrial cancer (n = 2). (111)In-DTPA-folate was administered as an intravenous bolus, and whole-body images were obtained at 30 min, 4 h, and (for the first 19 patients) 24 h after injection; SPECT also was done at the delayed imaging times. For 19 of the patients, unlabeled free folic acid was injected before administration of (111)In-DTPA-folate to also assess the impact of folate loading on tracer biodistribution. Masked and unmasked readings of the images by 2 nuclear medicine physicians were compared with the pathologic findings after surgery.RESULTS:Among 33 patients who had surgical intervention, 14 had new or recurrent malignant tumors. All of 7 newly diagnosed ovarian carcinomas were identified by both masked readers (sensitivity, 100%). The sensitivity for detection of 7 recurrent malignancies was 38% for masked readings and 85% for unmasked readings, indicating that correlation with anatomic imaging studies (CT) was highly important in diagnosis of these lesions. Eighteen of the studied patients were found to have benign masses; for this limited population, the specificity of (111)In-DTPA-folate scintigraphy was 76% and 82% for the masked and unmasked analyses, respectively.CONCLUSION:(111)In-DTPA-folate is safe, and possibly effective, for scintigraphy differentiating between malignant and benign ovarian masses.

Acetazolamide (ACZ)-enhanced Single Photon Emission Computer Tomography (SPECT) scans can assess both cerebral perfusion and vascular reactivity. Patients with poor reactivity lack perfusion reserve, and are at risk for stroke should perfusion diminish further. This study compared the preoperative ACZ-enhanced SPECT scans of 60 symptomatic to 40 asymptomatic patients with internal carotid artery stenosis (ICAS) in an effort to better define the cause of their symptoms and effects of carotid endarterectomy (CEA) on cerebral perfusion and reactivity in these two groups of patients. Symptomatic patients had at least a 60% (x=84%) ICAS. Asymptomatic patients had at least an 80% (x=90%) ICAS. Preoperative ACZ SPECT scans were obtained usually one week before CEA. All patients underwent CEA. Postoperative ACZ SPECT scans were obtained in 78 of the patients, usually at the first postoperative (-30 days) visit. [Table: see text] Asymptomatic patients demonstrated poorer perfusion than symptomatic patients, which tends to support the premise that most strokes and carotid symptoms are secondary to emboli rather than hypoperfusion. Interestingly, cerebral reactivity was poor in both symptomatic and asymptomatic patients before CEA, suggesting inadequate collaterals and dependency on the ipsilateral carotid. Carotid endarterectomy improved vasoreactivity in 84% of the patients. ACZ SPECT scans provided evidence of the return of cerebral perfusion and reactivity following endarterectomy.

Purpose: Acetazolamide (ACZ)-enhanced single photon emission computed tomography (SPECT) scans can assess both cerebral perfusion and vascular reactivity. Patients with asymptomatic critical carotid artery stenosis were evaluated for cerebral vascular reactivity to determine the effect of extracranial occlusive disease and the effect of carotid endarterectomy (CEA) on intracerebral reactivity.Methods: In 44 patients with asymptomatic critical carotid artery stenosis, cerebral per fusion and vascular reactivity were assessed before CEA with resting and ACZ-enhanced SPECT scans. All patients had a 70% or greater ipsilateral internal carotid artery stenosis. Preoperative ACZ-enhanced SPECT scans were obtained, usually 5 days before CEA. Postoperative ACZ-enhanced SPECT scans were obtained in 30 patients.Results: Preoperative SPECT scans were asymmetric, revealing focal (n = 19) or global (n = 15) decreased reactivity in 34 patients (77%). Ten patients had symmetric or normal reactivity. After CEA, 23 patients demonstrated an improvement in reactivity ipsilateral to the side of surgery. The remaining seven patients failed to improve after surgery.Conclusion: Although all patients had a high-grade internal carotid stenosis, nearly a quarter of the patients had excellent intracerebral collateral flow. Only 71% of patients demonstrated improved intracerebral vasoreactivity after CEA. The lack of improvement in the other patients may have resulted from intracerebral pathology or lack of improvement in the extracranial carotid hemodynamics.

UNLABELLED:Twenty consecutive patients were evaluated for presumptive myocardial viability using rest TI-SPECT, FDG-PET and FDG-SPECT. The FDG studies were performed after rest TI-SPECT to guide intervention or medical management.METHODS:Twenty patients with proven coronary artery disease, either known or suspected to have previous myocardial infarction and persistent perfusion defects shown by rest reinjection TI-SPECT, underwent FDG-PET and subsequent FDG-SPECT with a three-detector SPECT camera. FDG-PET and SPECT images were compared by five observers to determine if any fixed thallium segments were visualized by either FDG imaging method.RESULTS:Thirteen of 60 fixed segments were shown probably viable by FDG-SPECT (8 of 20 patients) and 14 of 60 by FDG PET (7 of 20 patients). Two patients had fixed thallium segments found probably viable with FDG by SPECT alone and one by PET alone.CONCLUSION:FDG is shown to provide additional information about myocardial viability. Both SPECT, using a three-detector camera, and PET with a specialized instrument are equally effective for imaging FDG in this application.

This is the third article in a series of four on interventional nuclear medicine. Upon completion, the technologist will be able to (1) discuss the purpose of using acetazolamide with technetium-99m HMPAO brain imaging, (2) describe the imaging parameters, and (3) list the interpretation criteria.

Sixty-five patients referred for Tc-99m HMPAO SPECT brain perfusion studies had measurements of global Tc-99m HMPAO retention after injection at rest and after acetazolamide pretreatment. Acetazolamide produced relative changes in Tc-99m HMPAO retention similar to those previously reported with Xe-133 regional cerebral blood flow (rCBF) measurements. This addition to imaging protocols allows another objective evaluation of the cerebral vascular reserve.

Estimates have been made for the amount of digital storage capacity necessary and the data creation rates for the nuclear medicine portion of an all digital radiology department. After installation, the number of computer studies performed, image files created and bytes archived for each month increased with time. There was a high correspondence between the number of computer studies performed and (1) the number of new image files created (r=0.95) and (2) the total number of pytes archived (r=0.82). The average number of bytes created per work-day was 5.6 x 106 Experience with our nuclear medicine system seems to indicate that when planning a picture archiving and communications system (PACS) installation (1) the amount of necessary online storage may increase and continue to increase after installation and (2) our estimate of nuclear medicine digital images creation rates agree with previous estimates l.

Six patients with symptomatic cerebral vascular disease were studied with 133Xe regional cerebral blood flow measurements and HIPDM cerebral imaging after the administration of acetazolamide. The results obtained from this small group suggest this technique may have high sensitivity for detection of cerebral vascular disease.

To determine the role of hypoxemia in the pathogenesis of impaired sodium and water excretion in advanced chronic obstructive lung disease, 11 clinically stable, hypercapneic patients requiring long-term supplemental oxygen were studied. The renal, hormonal, and cardiovascular responses to sodium and water loading were determined during five-and-a-half-hour studies on a control day (arterial oxygen tension = 80 +/- 6 mm Hg) and on an experimental day under hypoxic conditions (arterial oxygen tension = 39 +/- 2 mm Hg). Hypoxemia produced a significant decrease in urinary sodium excretion but did not affect urinary water excretion. Hypoxemia also resulted in concomitant declines in mean blood pressure, glomerular filtration rate, and filtered sodium load. Renal plasma flow and filtration fraction were unchanged whereas cardiac index rose. On the control day, plasma renin activity and norepinephrine levels were elevated whereas aldosterone and arginine vasopressin levels were normal; none of these four hormones was affected by hypoxemia. Renal tubular function did not appear to be altered by hypoxemia as there was no significant change in fractional reabsorption of sodium. The concurrent decreases in glomerular filtration rate, filtered sodium load, and mean blood pressure at constant renal plasma flow suggest that the reduction in urinary sodium excretion was due to an effect of hypoxemia on glomerular function, possibly related to impaired renovascular autoregulation.

Gallium-67 and 3-phase bone scan (3P) studies, though very sensitive, are not very specific in evaluating suspected osteomyelitis (OM) which is superimposed upon other diseases that cause increased bone turnover (IBT). The authors compared In-111 acetylacetone labeled granulocytes (In-111) GRAN) with 3P in 57 such patients; 29 of these patients had Ga-67 studies as well. In-111 GRAN had a sensitivity of 100% in acute OM, 62% in chronic OM, and a specificity of 96%. Gallium-67 ruled out OM when the study was normal; it diagnosed OM when the relative uptake of Ga-67 exceeded the uptake of Tc-99m MDP, or when the skeletal distribution of Ga-67 was different from that of the TC-99m MDP. Unfortunately, these criteria were met in only 28% of the subjects. The simple approach of increased Ga-67 activity meant OM gave a sensitivity of 100%, but an unacceptable specificity of 38%. Chronic cellulitis or long-standing decubiti were seldom detected by IN-111 GRAN. Clinically obvious soft tissue infections or cellulitis were seen with In-111 GRAN 27% of the time, and 17% of the time with Ga-67. The authors conclude that when added to 3P, In-111 GRAN provided more useful information than did Ga-67. A combination of all 3more » studies did not significantly increase the diagnostic yield. Performing In-111 GRAN without 3P in patients with IBT is not recommended since the 3P provides anatomic information that aids in the differentiation of OM from soft tissue infections.« less

Exercise and 3 hour delayed redistribution thallium-201 myocardial perfusion imaging was performed in 107 patients including 87 patients with documented coronary artery disease and 20 patients with normal coronary arteriograms. A computer algorithm for statistical analysis and redisplay of the analog scintillation data was developed to augment the visual analysis of the standard analog image. The basic algorithm identified the myocardial area (pixel) with the most absolute counts and developed an appropriate standard deviation range from a table. All pixels in the area of the myocardium containing absolute counts below three standard deviation ranges (or approximately 6 standard deviations) were deleted from the final image. The remaining pixels were redisplayed in a digitized bimodal format and the image photographed. Two experienced observers compared visual analysis of the analog image alone and the analog image in conjunction with the computer-analyzed image for sensitivity, specificity and predictive accuracy in the detection of perfusion defects in patients with coronary artery disease and in normal subjects. Sensitivity in patients with coronary artery disease for the analog scintillation image alone was 79 percent (69 of 87) and with computer analysis 95 percent (83 of 87). Specificity in the patients with no coronary disease was 100 percent (20 of 20) for both techniques. The predictive accuracy of the test was 83 percent (89 of 107) for the analog image alone and 96 percent (103 of 107) for the two images combined. It is concluded that use of a computer statistical analysis algorithm of thallium-201 analog myocardial perfusion images improves the accuracy of detection of perfusion defects in patients with coronary artery disease.