Showing papers on "Perfusion scanning published in 1989"

Characterization of technetium-99m-L,L-ECD for brain perfusion imaging, Part 1: Pharmacology of technetium-99m ECD in nonhuman primates.

Abstract: Technetium-99m ethyl cysteinate dimer ([99mTc]ECD) is a neutral, lipophilic complex which rapidly crosses the blood-brain barrier. Brain retention and tissue metabolism of [99mTc]ECD is dependent upon the stereochemical configuration of the complex. While both L,L and D,D enantiomers are extracted by the brain, only the L,L but not the D,D form, is metabolized and retained in the monkey brain (4.7% injected dose initially, T 1/2 greater than 24 hr). Dynamic single photon emission computed tomography imaging studies in one monkey indicates 99mTc-L,L-ECD to be distributed in a pattern consistent with regional cerebral blood flow for up to 16 hr postinjection. Dual-labeled 99mTc-L,L-ECD and [14C]iodoantipyrine autoradiography studies performed 1 hr after administration show cortical gray to white matter ratios of both isotopes to be equivalent (approximately 4-5:1). These data suggest that 99mTc-L,L-ECD will be useful for the scintigraphic assessment of cerebral perfusion in humans.

Characterization of technetium-99m-L,L-ECD for brain perfusion imaging, Part 2: Biodistribution and brain imaging in humans.

Abstract: The safety, biodistribution and kinetics of a new perfusion imaging agent [99mTc-L,L]-ethyl cysteinate dimer (ECD) was evaluated in normal volunteers. Technetium-99m-L,L-ECD is a neutral, lipophilic complex, which is radiochemically pure and stable. Twelve healthy adults were injected with 25-30 mCi of 99mTc-L,L-ECD and imaged periodically for up to 24 hr. Planar imaging showed rapid brain uptake with a peak concentration of 4.9% injected dose and very slow brain washout (approximately 6% per hour during the first 6 hr). Repeat or dynamic tomographic imaging of the brain using either a rotating gamma camera or a multidetector system was performed up to 6 hr postinjection. The distribution of 99mTc-L,L-ECD in the brain did not change and was similar to the pattern seen with other perfusion agents. Background facial areas and lungs cleared rapidly. Peak blood activity was below 10% injected dose at all times and 99mTc-L,L-ECD cleared rapidly through the kidneys. Vital signs, blood and urine chemistries were normal in all volunteers and no adverse reactions were noted. These results suggest that 99mTc-L,L-ECD should be useful for routine assessment of cerebral perfusion in humans.

Memory and regional cerebral blood flow in mildly symptomatic Alzheimer's disease

Abstract: We performed SPECT perfusion imaging and memory testing with mildly and moderately demented Alzheimer's disease (AD) patients and with healthy controls. All patients had memory abnormalities, but 5 of the 21 patients had neither temporal nor parietal perfusion abnormalities, indicating that temporoparietal blood flow may be normal at a point when memory is pathologic and the clinical diagnosis of AD is possible.

Frostbite injury: prediction of tissue viability with triple-phase bone scanning.

Abstract: Triple-phase bone scans were obtained in seven patients within 48 hours of admission for frostbite injuries. Three patterns of perfusion imaging and delayed bone imaging were observed: hyperemic blood flow with normal early blood pool and normal delayed bone images; absent blood flow and absent early blood pool depiction, but depiction of bone in delayed images; and absent perfusion and absent blood pool depiction, with no bone uptake in the delayed images. The first pattern indicated mild ischemia that required no surgical treatment, the second indicated ischemia with occasional superficial tissue infarction that required minor debridement, and the third pattern indicated deep-tissue and bone infarction that required amputation. The triple-phase bone scan is a useful indicator of tissue viability as early as 2 days after cold injury and appears to have a clinical role in the evaluation of frostbite injuries. The perfusion and blood pool images demonstrate the ischemic tissue at risk, while the delayed bo...

The evaluation of ventricular function using gated myocardial imaging with Tc-99m MIBI.

Abstract: Left ventricular function is an important prognostic indicator in patients with coronary artery disease. We have assessed a method of providing this information as an adjunct to myocardial perfusion imaging using Tc-99m MIBI (2-methoxy-2-methyl-isopropyl-1-isonitrile). Two separate studies, at rest and during exercise, were performed following an injection of 400-600 M Bq of Tc-99m MIBI in 62 patients. Cardiac gating permitted excellent myocardial edge definition during the cardiac cycle. Radionuclide fractional shortening (RFS) was calculated from the anteroposterior (AP) and the septum to lateral wall (SL) axes in diastole and systole. Results were compared with echocardiographic fractional shortening (EFS) and the ejection fraction (EF) obtained from the gated equilibrium blood pool using Tc-99m-labelled red blood cells. The RFS in the AP axis correlated closely with echocardiographic FS (r = 0.89, P less than 0.001). The RFS in both axes was averaged to provide a global RFS. Global RFS correlated closely with LV radionuclide EF (r = 0.83, P less than 0.001). Inter- and intra-observer reproducibility studies have shown a variability for the procedure of less than 10%. In conclusion, gated perfusion imaging with Tc-99m MIBI, provides useful functional information as an adjunct to perfusion imaging.

Clinical experience with Tc-99m HM-PAO high resolution SPECT of the brain in patients with cerebrovascular accidents.

Abstract: In order to evaluate the diagnostic contribution of brain SPECT imaging with 99mTc-HMPAO in cerebrovascular disease, we examined 92 stroke cases (144 lesions), 2 hematoma cases and 30 cases with transient neurologic symptoms. Abnormal tracer distribution is visible as zones of either hypoactivity or hyperactivity (border zone hyperemia or luxury perfusion). Remote vascularization changes could also be found (crossed cerebellar diaschisis or ipsilateral cortical perfusion reduction in thalamic or capsula interna lesions). Both X-ray CT and blood flow SPECT have comparable sensitivity in the exploration of cerebral infarction, with detection in, respectively, 89.5% and 87.5% of the lesions. False negative scintitomographic images are frequently recorded in small lacunar infarcts within the basal ganglia and white matter (capsula interna). Some early infarcts and asymmetry of brain perfusion in patients with transient neurologic symptoms are frequently not detected by CT. An additional advantage of blood flow SPECT is its ability to visualize remote blood flow changes and the changing pattern of vascularization of ischemic lesions and their surrounding areas including hyperemia.

Model-based quantification of myocardial perfusion images from SPECT

Abstract: A system for quantitative analysis of myocardial perfusion tomograms is proposed. The system starts with an automated delineation of the total left ventricle, including possible perfusion defects, to determine the mass and shape of the myocardium. Next, polar maps or bulls-eyes are computed from the delineation, which can then be compared to reference bulls-eyes to detect perfusion defects. The proposed system differs in three main aspects from currently available bulls-eye algorithms. First, radial slices are used rather than short-axis slices. In this way three-dimensional gradient information is retained, in particular near the base and the apex of the left ventricle. Moreover, the reproducibility of this method is expected to be superior, since the interactive selection of short axis slices through the left ventricle is eliminated. Second, the left ventricle is automatically delineated using a flexible computer model in order to obtain higher reproducibility. The resulting delineation contains both mass and shape information. Third, in addition to the classic count rate bulls-eye, a mass bulls-eye is computed, which contains the myocardial mass corresponding to each bulls-eye pixel. Analysis of the count rate bulls-eye reveals perfusion defects, the quantification of the defects is carried out with the mass bulls-eye.

Peripheral perfusion after cardiac surgery.

Abstract: Postoperative peripheral perfusion was studied in eight male patients undergoing coronary arterial bypass grafting. Transcutaneous PO2 (PtcO2), subcutaneous tissue PO2 (PscO2) and skin red cell flux (RCF) were recorded continuously in the upper extremity. In addition, peripheral and core temperatures, as well as central hemodynamic and some metabolic variables, were determined. The FIO2 was maintained at 0.3. Complete opening of peripheral circulation occurred within a mean of 7 h after transferring the patients to the ICU. As the fingertip temperature rose, the PtcO2 index, PscO2, and RCF underwent simultaneous increases, thereby reflecting reperfusion of the peripheral vascular bed.

Clinical cardiac PET using generator-produced Rb-82: a review.

Abstract: Cardiac positron emission tomography (PET) with generator-produced rubidium-82 (Rb-82) provides information not previously available for optimal diagnosis and management of cardiac disease. This new information includes the accurate, noninvasive diagnosis of coronary artery disease in asymptomatic or symptomatic patients, the noninvasive assessment of coronary stenosis severity, myocardial infarct imaging, myocardial viability, collateral function, and cardiomyopathy. Cardiac positron imaging may be carried out economically at the same or less cost as other high-tech diagnostic imaging but provides perfusion and metabolic information quantitatively for routine clinical studies not available by other diagnostic modalities.

The hollow skull: a sign of brain death in Tc-99m HM-PAO brain scintigraphy.

Abstract: The advantage of Tc-99m HM-PAO, a newly introduced compound for brain perfusion imaging, is illustrated in three patients with suspicion of brain death. With Tc-99m HM-PAO, the carotid flow study is not essential, as it is in the Tc-99m pertechnetate carotid angiogram; planar images are equally useful; and there is no need for SPECT images. For the diagnosis of brain death, Tc-99m HM-PAO can be injected in the intensive care unit and planar images can be obtained at a later time using a mobile camera or whenever the patient can be moved to the nuclear medicine department.

Quantitative iodine-123 IMP imaging of brain perfusion in schizophrenia.

Abstract: Decreased perfusion in the frontal lobes of patients with chronic schizophrenia has been reported by multiple observes using a variety of techniques. Other observers have been unable to confirm this finding using similar techniques. In this study quantitative single photon emission computed tomography brain imaging was performed using p,5n [123I]IMP in five normal subjects and ten chronically medicated patients with schizophrenia. The acquisition data were preprocessed with an image dependent Metz filter and reconstructed using a ramp filtered back projection technique. The uptake in each of 50 regions of interest in each subject was normalized to the uptake in the cerebellum. There were no significant confirmed differences in the comparable ratios of normal subjects and patients with schizophrenia even at the p = 0.15 level. "Hypofrontality" was not observed.

Reversibility of pulmonary telangiectasia in liver cirrhosis evidenced by serial dynamic pulmonary perfusion imaging.

Abstract: Pulmonary perfusion imaging with Tc-99m MAA revealed significant uptake in the lungs, brain, spleen, and both kidneys of a 48-year-old woman with liver cirrhosis and pulmonary telangiectasia associated with marked hypoxemia and cyanosis. Dynamic pulmonary perfusion imaging revealed a gradual reduction after peak uptake in both lungs. Several weeks after albumin replacement, the hypoxia and dyspnea disappeared with no change in hepatocellular function. At that time, dynamic pulmonary perfusion imaging revealed a plateau-like time-activity curve of uptake in the lungs, as compared with the findings obtained during the state of severe hypoxemia. These observations suggest that pulmonary telangiectasia in a patient with liver cirrhosis may be due to functional vasodilatation. Serial dynamic pulmonary perfusion imaging indicates the passage of the MAA particles through the widened lumen of the pulmonary alveolar capillaries.

Brain perfusion defect size in SPECT predicts outcome in cerebral infarction.

Abstract: The results of previous reports on the usefulness of brain perfusion single photon emission computed tomography (SPECT) in predicting the outcome of patients with acute cerebral infarction are conflicting. We therefore studied brain perfusion in 64 patients with a single supratentorial infarction. Contradictory to previous results the perfusion defect volume estimated from transversal and coronal slices correlated significantly with both presenting clinical findings and outcome. Although the clinical status at admission also correlated well with outcome, there was a subgroup of patients in which the favourable outcome was predicted only by SPECT and not by physical or any other examination at admission.

THE USE OF99mTc RADIOAEROSOL VENTILATION AND MACROAGGREGATED ALBUMIN PERFUSION IMAGING FOR THE DETECTION OF PULMONARY EMBOLI IN THE DOG

Abstract: This study was undertaken to design protocol for use of radioaerosol of technetium-99m-labeled diethylenetriaminepentacetic acid (99mTc-DTPA) for ventilation imaging as clinical tool in the dog and to evaluate imaging characteristics in both normal dogs and dogs with simulated pulmonary embolism. Clearance of the 99mTc-DTPA radioaerosol from the lung was also evaluated. Six normal dogs were used in two phases: (1) as their own controls and (2) during pulmonary artery occlusion using Swan-Ganz catheter. Radioaerosol ventilation images were obtained and rate of clearance from normal and occluded lungs determined. Perfusion studies using technetium-99m-macroaggregated albumin (99mTc-MAA) immediately followed. Clearance half-times (T1/2) were found to be significantly increased (p < 0.05) in acutely occluded lungs; however, the small magnitude of this change was visually difficult to detect on the ventilation images. Good quality initial ventilation and perfusion images were obtained and provided ready evaluation of ventilation (V), perfusion (Q), and induced V/Q mismatches. A clinical case of pulmonary thromboembolic disease was also evaluated with diagnostic result, indicating that this method of V/Q scintigraphy can provide useful information in those clinical cases in which pulmonary thromboembolism is suspected.

Assessment of myocardial viability with SPECT and PET imaging.

Abstract: The use of thrombolytic therapy for the treatment of acute myocardial infarction has increased the number of patients presenting for assessment of myocardial viability. Stress SPECT 201Tl perfusion imaging performed in the conventional manner with delayed imaging at 4 hr can identify a large percentage of patients with ischemic but viable areas of myocardium. In some patients, delayed imaging up to as long as 24-48 hr after exercise may be required to show 201Tl redistribution indicative of viability. Thus, in most patients, stress 201Tl scintigraphy will correctly identify the presence of viable myocardium. PET imaging, with its ability to assess blood flow and metabolism separately, offers the ability to identify myocardial areas with diminished blood flow but preserved metabolism. Areas with such a blood flow-metabolism mismatch may benefit from revascularization, even in the absence of 201Tl redistribution. The exact role PET will play in the initial evaluation of patients presenting for assessment of myocardial viability remains to be established as more clinical data are accumulated.

Detection of pulmonary telangiectasia using dynamic pulmonary perfusion imaging in patients with liver cirrhosis.

Abstract: Two cases of liver cirrhosis associated with marked hypoxemia are presented. Chest radiographs and cardiopulmonary function showed no abnormalities, except for the low diffusion capacity of carbon monoxide and slight elevation of the shunt ratio (20 and 6.2%, respectively), as estimated under conditions of 100% oxygen inhalation. Pulmonary perfusion imaging with Tc-99m macroaggregated albumin (MAA) revealed a significant radioisotope uptake in the lungs, brain, spleen, and both kidneys. Shunt ratios, estimated by the quantitative radionuclide method, were 60 and 68%, respectively. Dynamic pulmonary perfusion imaging revealed a gradual reduction in uptake in all areas of both lungs. The discrepancy of the shunt ratio between the two methods results from an abnormal dilatation of alveolar capillaries. The gradual reduction of radioactivity in areas of the lungs is caused by the passage of MAA particles through widened pulmonary capillaries.

Regional Pulmonary Perfusion Following Human Heart-Lung Transplantation

Abstract: Ventilation and perfusion scans were obtained in six subjects who had undergone heart-lung transplantation with consequent denervation of the cardiopulmonary axis. Two of the subjects had developed obliterative bronchiolitis, which is believed to be a form of chronic rejection. Their pulmonary function tests demonstrated airflow obstruction and their scintigraphic studies were abnormal. In the remaining four subjects without obstructive airways disease, ventilation and planar perfusion scans were normal. Single photon emission computed tomography imaging of pulmonary perfusion in these patients revealed a layered distribution of blood flow indistinguishable from that of normal individuals. It is concluded that neurogenic mechanisms have little influence on the pattern of local pulmonary blood flow at rest.

Assessment of Myocardial Perfusion Using Contrast Echocardiography

Abstract: Until recently, the clinical use of contrast echocardiography has been limited to the detection of intracardiac shunts,' identification and evaluation of regurgitant valvular disorders,2 and assessment of chamber dimension^.^ With the development of newer contrast agents, it has also become possible to use contrast echocardiographic techniques to evaluate myocardial perfu~ion.~ This application is particularly important since the coronary arteriogram, often considered to be the clinical standard for evaluating myocardial disease, does not adequately describe or predict the physiological state of perfusion. White and co-workers5 were among the first to question the usefulness of the angiogram for evaluating the physiological status of myocardial perfusion. In their clinical study, they did not find a significant correlation between the degree of coronary arterial stenosis present in a single coronary artery and the degree of vascular reserve measured by epicardial Doppler techniques. These observations are of critical importance because of the increasing use of interventional cardiac therapy. Without a known, quantifiable method for assessing regional perfusion and the extent of risk, the indications for instituting interventional therapy and the evaluation of its effectiveness remain unclear. Therefore, a technique that would differentiate between viable and nonviable tissue is necessary.6 Clinical studies have shown that contrast echocardiography can be used to directly and

Diagnostic value of atrial pacing and thallium-201 scintigraphy for the assessment of patients with chest pain.

Abstract: Atrial pacing was performed either alone (n = 23) or in combination with thallium-201 scintigraphy (n = 113) in 136 patients referred for evaluation of chest pain. The presence of coronary artery disease (CAD) was excluded by cardiac catheterization in 12 patients and confirmed in 124. Both pacing-induced ST depression and angina had sensitivities of 48% for CAD; specificities were 75% and 83%, respectively. An abnormal thallium-201 scan (one or more reversible and/or fixed perfusion defects) was seen in 72% of patients with CAD (specificity 83%). Reversible perfusion defects were present in 47% of patients with CAD (specificity 83%), and fixed defects in 36% (specificity 100%). Pacing was associated with either ST depression or an abnormal perfusion scan in 81% of patients (specificity 67%). There were no significant differences in the results of atria pacing or thallium-201 scintigraphy in patients with or without a history of myocardial infarction, or in those with or without previous coronary artery bypass surgery. Pacing-induced ST depression, or both ST depression and a reversible perfusion defect occurred significantly less frequently in patients with peripheral vascular disease than in those without this diagnosis (p less than .05). With only one exception, there were no significant differences in the sensitivities of any indicators of ischemia (ST depression, angina, or perfusion scans), either individually or in combination, as the peak pacing rate or double product achieved increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Dipyridamole thallium-201 perfusion imaging for the study of ischemic heart disease in hemodialysis patients.

Abstract: To assess the usefulness of dipyridamole thallium perfusion imaging in the evaluation of myocardial perfusion in hemodialysis (HD), we studied 29 HD patients divided into three groups: A) 13 patients with clinical angina, B) 8 patients without angina but similar in age, sex, time on HD and hematocrit and C) 8 young asymptomatic patients (mean age 33 +/- 9.7 years). Dipyridamole thallium-201 (Tl-201) perfusion imaging revealed myocardial perfusion defects in 8 patients (61%) from group A, 4 (50%) from group B and 1 (12.5%) from group C. These defects were localized in the inferior, posterior and septal segments of the left ventricle. Abnormal myocardial perfusion was associated with age over 50 years and aortic calcifications (p less than 0.05). Eight patients died within the following four years. All had aortic calcifications (p less than 0.001). Our results show that myocardial perfusion defects are frequent even in non-symptomatic HD patients. This suggests that ischemic heart disease could be more frequent than estimated by clinical symptoms alone. Tl-201 scintigraphy may be a useful non-invasive procedure in cardiological evaluation of HD patients.

Pulmonary nuclear medicine evaluation of thromboembolic disease.

Abstract: PE is a complication of underlying venous thrombosis and most often arises from the deep veins of the lower extremities. The thromboembolic event is difficult to diagnose clinically and carries significant morbidity and mortality. Treatment with anticoagulation also has risks. Thus accurate diagnosis is important. A normal perfusion lung scan excludes major pulmonary emboli. Lung perfusion scintigraphy provides high sensitivity for interrupted blood flow but lacks specificity for embolic vascular occlusion. Ventilation scintigraphy is sensitive for obstructive pulmonary disease and improves specificity for PE when combined with the perfusion scan. Several retrospective studies have established probability levels for PE on the basis of certain ventilation, perfusion, and chest x-ray patterns. These results have high positive and negative predictive value and directly affect patient management. The first large prospective study on PE has just been completed. The results of this study should more clearly define the role for ventilation-perfusion scintigraphy in PE.

Spontaneous abrupt changes in the distribution of ventilation: a cause for apparent mismatching on ventilation/perfusion scintigraphy.

Abstract: A defect seen in the perfusion scan in a region of lung that is normally ventilated is usually interpreted as indicating pulmonary vascular disease. Since the distribution of 99Tcm macro-aggregated albumin (MAA) represents the distribution of perfusion (Q) only at the time of MAA injection, the assumption is required that the distribution of ventilation (V) remains unchanged between MAA injection and the commencement of imaging. We report the V/Q scintigraphic findings in six patients (including four children), in whom this assumption could not be sustained. Thus ventilation imaged with 81Krm was seen to change during image acquisition in lobes that showed perfusion abnormalities. In some, but not all, views the appearances were typical for pulmonary vascular disease, which might easily have been misdiagnosed if the changes in the distribution of ventilation had not announced themselves by occurring during image acquisition. A ventilation image obtained immediately before injection of 99Tcm-MAA m...

Right-to-left shunting via persistent left superior vena cava identified by perfusion lung scintigraphy.

Abstract: A right-to-left shunt was demonstrated following a left antecubital injection of [99mTc]MAA but was not seen after a right antecubital injection. This was because of the presence of a persistent left superior vena cava draining into the left atrium. Recognition of the presence of this anatomic variant is of importance in perfusion imaging, in patients with otherwise unexplained systemic embolization.