Showing papers on "Perfusion scanning published in 1995"
TL;DR: Helical CT was only 63% sensitive in a subset of patients and subsegmental emboli are difficult to diagnose, suggesting a limited role in the evaluation of acute pulmonary embolism.
Abstract: This study was designed to prospectively compare helical CT with pulmonary angiography in the detection of pulmonary embolism in patients with an unresolved clinical and scintigraphic diagnosis.Twenty patients with an unresolved suspicion of pulmonary embolism were evaluated with contrast-enhanced helical CT and with selective pulmonary angiography. An average of 11 hr separated the two studies. The CT scans were obtained during one 24-sec or two 12-sec breath-holds. CT scans were interpreted without knowledge of the results of scintigraphy or angiography. Selective pulmonary angiograms were obtained with knowledge of the findings on the ventilation/perfusion scan only. The sensitivity and specificity of CT were compared with those of angiography for central vessels (segmental and larger) only and for all vessels.Eleven of the 20 patients had proved pulmonary embolism (seven in central vessels and four in subsegmental vessels only). When only central vessels were analyzed, CT sensitivity was 86%, specific...
436 citations
TL;DR: Preliminary results suggest that two simple MR perfusion studies before and early in therapy can offer important information on treatment outcome within the first 2 weeks of radiation therapy before response is evident by clinical examination.
Abstract: Purpose: This study investigated sequential changes in tumor blood supply using magnetic resonance (MR) perfusion imaging and assessed their significance in the prediction of outcome of patients with advanced cervical cancer The purpose of this project was to devise a simple, noninvasive method to predict early signs of treatment failure in advanced cervical cancer treated with conventional radiation therapy Methods and Materials: Sixty-eight MR perfusion studies were performed prospectively in 17 patients with squamous carcinomas (14) and adenocarcinomas (3) of the cervix, Stages bulky IB (1), IIB (5), IIIA (1), IIIB (8), and IVA (1), and recurrent (1) Four sequential studies were obtained in each patient: immediately before radiation therapy (pretherapy), after a dose of 20–22 Gy/∼2 weeks (early therapy), after a dose of 40–45 Gy/∼4–5 weeks (midtherapy), and 4–6 weeks after completion of therapy (follow-up) Perfusion imaging of the tumor was obtained at 3-s intervals in the sagittal plane A bolus of 01 mmol/kg of MR contrast material (gadoteridol) was injected intravenously 30 s after beginning image acquisition at a rate of 9 ml/s using a power injector Time/signal-intensity curves to reflect the onset, slope, and relative signal intensity (rSI) of contrast enhancement in the tumor region were generated Median follow-up was 8 months (range 3–18 months) Results: Tumors with a higher tissue perfusion (rSI ≥ 28) in the pretherapy and early therapy (20–22 Gy) studies had a lower incidence of local recurrence than those with a rSI of p = 005) An increase in tumor perfusion early during therapy (20–22 Gy), particularly to an rSI of ≥ 28, was the strongest predictor of local recurrence (0% vs 78%; p = 0002) However, pelvic examination during early therapy (20–22 Gy) commonly showed no appreciable tumor regression The slope of the time/signal-intensity curve obtained before and during radiation therapy also correlated with local recurrence Follow-up perfusion studies did not provide information to predict recurrence Conclusion: These preliminary results suggest that two simple MR perfusion studies before and early in therapy can offer important information on treatment outcome within the first 2 weeks of radiation therapy before response is evident by clinical examination Highg tumor perfusion before therapy and increasing or persistent high perfusion early during the course of therapy appear to be favorable signs High perfusion suggests a high blood and oxygen supply to the tumor The increase in tumor perfusion seen in some patients early during radiation therapy suggests improved oxygenation of previously hypoxic cells following early cell kill Radiation tehrapy is more effective in eradicating these tumors, resulting in improved local control Our technique may be helpful in identifying early —while more aggressive therapy can still be implemented—those patients who respond poorly to conventional radiation therapy
224 citations
01 Feb 1995
TL;DR: Dobutamine stress echocardiography is an accurate, safe, cost-effective, and portable procedure for the noninvasive diagnosis of coronary artery disease and for the preoperative assessment of patients with such disease, especially those who are unable to perform adequate exercise tests.
Abstract: Objective To describe the rationale, methods, and clinical applications for dobutamine stress echocardiography. Design We review our experience with the first 1,000 Mayo Clinic patients who underwent this procedure and discuss studies from the literature that have assessed the accuracy of dobutamine stress echocardiography in determining the presence and extent of coronary artery disease. Material and Methods The Mayo protocol for dobutamine stress echocardiography is presented, and the indications for use of this test and comparisons of sensitivity and specificity with other tests are summarized. Results Although exercise stress testing is the usual noninvasive method for the detection and assessment of coronary artery disease, a substantial number of patients are unable to perform adequate exercise because of physical limitations. In these patients, dobutamine stress echocardiography has emerged as a feasible, safe, and accurate method for the evaluation of coronary artery disease. The test has been proved to be valuable in the noninvasive diagnosis of coronary artery disease and to have an accuracy comparable to that of tomographic perfusion imaging. Other indications for dobutamine stress echocardiog raphy include risk stratification before noncardiac surgical procedures, risk stratification after myocardial infarction, and identification of viable myocardium in patients with left ventricular dysfunction. Conclusion Dobutamine stress echocardiography is an accurate, safe, cost-effective, and portable procedure for the noninvasive diagnosis of coronary artery disease and for the preoperative assessment of patients with such disease, especially those who are unable to perform adequate exercise tests.
208 citations
TL;DR: Part 1 Diffusion imaging: principles of diffusion MR imaging and spectroscopy - molecular diffusion and nuclear magnetic resonance, diffusion imaging, diffusion Spectroscopy implementation - hardware considerations for diffusion/perfusion imaging, b factor, artifacts applications - diffusion in biological tissues, diffusion in the CNS, temperature imaging by NMR.
Abstract: Part 1 Diffusion imaging: principles of diffusion MR imaging and spectroscopy - molecular diffusion and nuclear magnetic resonance, diffusion imaging, diffusion spectroscopy implementation - hardware considerations for diffusion/perfusion imaging, b factor, artifacts applications - diffusion in biological tissues, diffusion in the CNS, temperature imaging by NMR. Part 2 Perfusion imaging: the concept of perfusion imaging - blood volumes, haematocrits and transit-times in parenchymal microvascular systems of the rat brain, principles of conventional techniques, brain function mapping perfusion MR imaging (principles and applications) - tracer approaches, perfusion imaging with exogenous contrast agents, magnetic labelling brain activation studies with blood oxygen level dependent (Bold) contrast MRI - intrinsic MRI methods for assessing tissue perfusion - deoxyhaemoglobin contrast in animal models, field strength and sequence issues, dynamic characteristics and data analysis methods, applications.
197 citations
TL;DR: Patients with myalgic encephalomyelitis/chronic fatigue syndrome have a generalized reduction of brain perfusion, with a particular pattern of hypoperfusion of the brainstem, confirmed in all ME/CFS patients.
Abstract: We looked for brain perfusion abnormalities in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). An initial pilot study revealed widespread reduction of regional brain perfusion in 24 ME/CFS patients, compared with 24 normal volunteers. Hypoperfusion of the brainstem (0.72 +/- 0.05 vs. 0.80 +/- 0.04, p < 0.0001) was marked and constant. We then tested whether perfusion to the brainstem in ME/CFS patients differs from that in normals, patients with major depression, and others with epilepsy. Data from a total of 146 subjects were included in the present study: 40 normal volunteers, 67 patients with ME/CFS (24 in the pilot study, 16 with no psychiatric disorders, 13 with ME/CFS and depression, 14 with ME/CFS and other psychiatric disorders), 10 epileptics, 20 young depressed patients and 9 elderly depressed individuals. Brain perfusion ratios were calculated using 99Tcm-hexamethylpropylene amine oxime (99Tcm-HMPAO) and single-photon emission tomography (SPET) with a dedicated three-detector gamma camera computer/system (GE Neurocam). Brain-stem hypoperfusion was confirmed in all ME/CFS patients. Furthermore, the 16 ME/CFS patients with no psychiatric disorders and the initial 24 patients in the pilot study showed significantly lower brainstem perfusion (0.71 +/- 0.03) than did depressed patients (0.77 +/- 0.03; ANOVA, p < 0.0001). Patients with ME/CFS have a generalized reduction of brain perfusion, with a particular pattern of hypoperfusion of the brainstem.
190 citations
TL;DR: It is shown that no signal loss occurs due to MTC effects when the two‐coil system is used for MRI of rat brain perfusion, enabling three‐dimensional perfusion imaging.
Abstract: When a single coil is used to measure perfusion by arterial spin labeling, saturation of macromolecular protons occurs during the labeling period. Induced magnetization transfer contrast (MTC) effects decrease tissue water signal intensity, reducing the sensitivity of the technique. In addition, MTC effects must be properly accounted for in acquiring a control image. This forces the image to a single slice centered between the labeling plane and the control plane. In this work, a two-coil system is presented as a way to avoid saturation of macromolecular spins during arterial spin labeling. The system consists of one small surface coil for labeling the arterial water spins, and a head coil for MRI, actively decoupled from the labeling coil by using PIN diodes. It is shown that no signal loss occurs due to MTC effects when the two-coil system is used for MRI of rat brain perfusion, enabling three-dimensional perfusion imaging. Using the two-coil system, a multi-slice MRI sequence was used to study the regional effects of amphetamine on brain perfusion. Amphetamine causes significant increases in perfusion in many areas of the brain including the cortex, cingulate, and caudate putamen, in agreement with previous results using deoxyglucose uptake to monitor brain activation.
162 citations
TL;DR: The authors tested a noninvasive technique for magnetic resonance imaging of perfusion in human kidneys by magnetic labeling (spin tagging) of aortic arterial water to generate an endogenous tracer.
Abstract: The authors tested a noninvasive technique for magnetic resonance imaging of perfusion in human kidneys. Magnetic labeling (spin tagging) of aortic arterial water was performed to generate an endogenous tracer. Breath-hold renal perfusion images obtained in seven volunteers yielded average perfusion rates in cortex and medulla of 278 mL.100 g-1.min-1 +/- 55 (standard error) and 55 mL.100 g-1.min-1 +/- 25, respectively.
145 citations
01 Jan 1995
TL;DR: Applications of perfusion and diffusion imaging are reviewed in relation to the pathophysiology, the pathobiochemistry, and the therapy of evolving brain infarct after focal ischemia and the manifestation and reversal of ischemic injury during and after global ischemIA.
Abstract: Over the last few years, diffusion and perfusion magnetic resonance (MR) imaging methods have found increasing user for monitoring the effects of cerebral ischemia under clinical and experimental conditions Blood perfusion can be visualized by studying the patency of the cerebrovascular bed (MR angiography), by recording exchange of diffusible tracers between blood and brain ([2H]water or [19F]trifluoromethane clearance), or by measuring the volume and transit time of the circulating blood (bolus track or spin-tagging imaging) In addition, changes in blood oxygenation level can be visualized by taking advantage of the susceptibility changes of the magnetic field homogeneity (functional or blood-oxygenation-level-dependent imaging) Diffusion imaging is based on the modulation of signal intensity by brain water diffusion Recording a series of diffusion-weighted images allows calculation of the apparent diffusion coefficient (ADC) and the reconstruction of quantitative ADC images Brain ADC changes are a function of intra-extracellular water homeostasis and therefore are a sensitive marker of ionic equilibrium Since disturbances of ion and water homeostasis are among the first pathological alterations induced by brain ischemia, diffusion imaging is able to detect the incipient injury within minutes Conversely, the reversal of these alterations is able to detect the incipient injury within minutes Conversely, the reversal of these alterations is an early and reliable predictor of postischemic recovery Applications of perfusion and diffusion imaging are reviewed in relation to the pathophysiology, the pathobiochemistry, and the therapy of evolving brain infarct after focal ischemia and the manifestation and reversal of ischemic injury during and after global ischemia
140 citations
TL;DR: The detection of myocardial ischemia may be significantly enhanced by utilizing the biphasic response during serial stress dobutamine echocardiography in patients with a wall motion abnormality.
122 citations
TL;DR: Although maximal exercise with adenosine infusion produced optimal results, the improvement over the submaximal exercise protocol was minor, and this has the advantage of being simple and achievable within the normal 6-min duration of the adenosin infusion.
120 citations
TL;DR: Diffusion-weighted MRI and perfusion imaging, as well as advances in magnetic resonance spectroscopy, will enhance the ability to evaluate ischemic stroke shortly after onset and rapidly provide important information to clinicians about ischemia, guiding diagnosis and helping in the development of acute stroke interventions to improve outcome.
Abstract: Neuroimaging was revolutionized by the development of computed tomography (CT) and standard T 1 - and T 2 -weighted magnetic resonance imaging (MRI). Magnetic resonance imaging and CT can adequately distinguish hemorrhage from infarction and depict ischemic stroke 12 to 24 hours after onset. However, during the critical initial hours after the onset of ischemic stroke, these imaging technologies do not adequately demonstrate the location and extent of infarction. Diffusion-weighted MRI and perfusion imaging, as well as advances in magnetic resonance spectroscopy, will enhance our ability to evaluate ischemic stroke shortly after onset. Some of the uses of MRI techniques are as follows: (1) Diffusion-weighted imaging can depict the location and extent of the ischemic lesion as soon as a stroke patient is available for examination. (2) Perfusion imaging evaluates blood flow within the brain's microvasculature and can reveal regions of perfusion deficits corresponding to major vascular territories. (3) Magnetic resonance spectroscopy evaluates metabolic abnormalties associated with focal brain ischemia by specific biochemical measurements. These MRI techniques will rapidly provide important information to clinicians about ischemia, guiding diagnosis and helping in the development of acute stroke interventions to improve outcome. ( JAMA . 1995;274:908-911)
TL;DR: This finding suggests that adjusting for differences in perfusion scan abnormalities by the use of nuclear testing eliminated the apparent gender-related referral bias and points to the need to better identify women at high cardiac risk.
TL;DR: The areas found to be hypoperfused in this study are consistent with known functions of fronto-striatal circuits and no characteristic patterns for behavioural subgroups has been documented with this technique.
Abstract: BACKGROUND Functional brain imaging with technetium-99m d,l-hexamethyl propyleneamine oxime (HMPAO) Single Photon Emission Tomography (SPET) allows us to explore the cerebral pathophysiology of Gilles de la Tourette's Syndrome (GTS).
METHOD Fifty patients and 20 controls were examined. Patients were rated for tic severity and mood. Scans were analysed quantitatively using internal ratios to the occipital cortex.
RESULTS Patients different from controls on measures of relative blood flow to the left caudate, anterior cingulate cortex and the left dorsolateral prefrontal cortex. Severity of tics was related to hypoperfusion of the left caudate and cingulate and a left medial temporal region. Hypoperfusion in the left dorsolateral prefrontal region was related to mood.
CONCLUSIONS The areas found to be hypoperfused in this study are consistent with known functions of fronto-striatal circuits. A wide range of perfusion patterns is seen, however, and no characteristic patterns for behavioural subgroups has been documented with this technique.
01 Apr 1995
TL;DR: Adenosine causes slightly greater systemic vasodilation than does dipyridamole but, in comparison with adenosine, are more difficult to manage and necessitate more monitoring time as well as fairly frequent intravenous use of aminophylline for reversal.
Abstract: Objective To compare the hemodynamic responses and the adverse effects associated with two coronary vasodilators used for pharmacologic stress testing. Design We retrospectively studied the results of adenosine and dipyridamole perfusion imaging in a large group of patients who underwent pharmacologic stress radionuclide perfusion imaging. Material and Methods One thousand patients given dipyridamole between April 1989 and April 1991 (before adenosine became available) were compared with 1,000 patients given adenosine between April 1991 and October 1992. A standard protocol was used to infuse the drugs before myocardial perfusion imaging with 201 TI or 99m Tc sestamibi. Results Peak heart rate was higher (85 versus 83 beats/min; P = 0.02) and systolic blood pressure was lower (129 versus 133 mm Hg; P P = 0.002). Horizontal or downsloping ST -segment depression of 1 mm or more occurred in 9 % of patients who received adenosine and in 8 % of those who received dipyridamole. Adverse effects occurred in 78% of the adenosine study group and in 50% of the dipyridamole group ( P Conclusion Adenosine causes slightly greater systemic vasodilation than does dipyridamole. Adverse effects occur less often with dipyridamole but, in comparison with adenosine, are more difficult to manage and necessitate more monitoring time as well as fairly frequent intravenous use of aminophylline for reversal.
TL;DR: It is concluded that dobutamine-stress echocardiography is a specific and accurate test for the noninvasive identification of CAD, even in the left anterior descending artery territory of patients with LBBB.
Abstract: This study compared the efficacy of dobutamine stress testing using 2-dimensional echocardiography and perfusion tomography for the noninvasive identification of coronary artery disease (CAD) in patients with left bundle branch block (LBBB). Twenty-four patients with permanent, complete LBBB (11 with previous myocardial infarction) were studied prospectively with dobutamine echocardiography and perfusion tomography. The presence of > 50% luminal diameter coronary stenosis was compared with the presence of dobutamine-induced fixed or reversible perfusion defects, and with resting or dobutamine-induced abnormalities of wall thickening. For each test, the left anterior coronary artery territory was compared with the circumflex and/or right coronary artery. Significant CAD was found in the left anterior descending coronary artery in 12 patients; all (100%) were identified by perfusion imaging, and 10 (83%, p = NS) by 2-dimensional stress echocardiography. In the 12 patients without left anterior descending CAD, scintigraphy was also positive in all (specificity: 0%), and echocardiography in only 1 (specificity: 92%, p < 0.01). The diagnostic accuracy was 50% and 87% (p < 0.05), respectively. This low specificity of perfusion tomography was improved by requiring an associated apical defect to indicate left anterior descending CAD and was corrected by restricting the diagnosis of coronary disease to those patients with partially reversible defects. In the circumflex and/or right coronary artery territory, sensitivity and specificity were similar using both techniques. We conclude that dobutamine-stress echocardiography is a specific and accurate test for the noninvasive identification of CAD, even in the left anterior descending artery territory of patients with LBBB.
TL;DR: In this paper, the authors assess the frequency of a normal perfusion lung scan in a consecutive series of patients with clinically suspected pulmonary embolism, to determine the complication risk of heparin therapy in those patients treated while awaiting lung scanning, and to evaluate the clinical validity of withholding anticoagulant therapy in patients with a normal lung scan result.
TL;DR: First clinical results indicate that there is an overall agreement between angiographic and functional disease severity, but there is a relatively large scatter of coronary reserve flow in patients with 50-90% coronary artery stenosis, which emphasizes the complimentary role of perfusion imaging in the prediction of functional severity.
Abstract: With the recent advances in interventional cardiology there is increasing need for characterization of the functional effects of coronary artery stenosis. Stress echocardiography and SPECT perfusion imaging are standard techniques for the qualitative assessment of regional function and perfusion in patients with proven or suspected coronary artery disease. However, Positron emission tomography (PET) provides quantitative measurements of regional myocardial perfusion. In combination with pharmacological stress testing, relative and absolute coronary reserve measurements can be used to define functional significance of regional coronary artery disease. First clinical results indicate that there is an overall agreement between angiographic and functional disease severity. However, there is a relatively large scatter of coronary reserve flow in patients with 50-90% coronary artery stenosis, which emphasizes the complimentary role of perfusion imaging in the prediction of functional severity. In addition, first studies in asymptomatic patients with a high risk for coronary artery disease suggest that PET coronary reserve flow measurement may be more sensitive than angiographic criteria for detection of early alterations in coronary vascular reactivity. Absolute quantification of blood flow may be useful in disease processes which affect the entire left ventricle such as vasculopathy in cardiac transplants, as well as endothelial dysfunction in patients with hypertension and cardiomyopathy. Future studies have to demonstrate the prognostic value of the quantitative estimate of coronary reserve as regards clinical outcome in patients with various coronary abnormalities. Quantitative flow measurements will be useful for monitoring progression and regression of coronary artery disease as well as assessment of acute and chronic therapy.
TL;DR: Hyperintensity in diffusion-weighted images was demonstrated after 30 minutes of middle cerebral artery occlusion and was mainly expressed in the lateral caudoputamen and parts of the lower frontoparietal cortex, while regions of different perfusion changes in the ischemic hemisphere were demonstrated.
Abstract: Background and Purpose Diffusion-weighted imaging and dynamic first-pass bolus tracking of susceptibility contrast agents (perfusion imaging) are two new magnetic resonance imaging techniques that offer the possibility of early diagnosis of stroke. The present study was performed to evaluate the diagnostic information derived from these two methods in a rat model of temporary focal ischemia.
Methods Fifteen male Wistar rats were assigned to 45 (n=7) or 120 minutes (n=8) of middle cerebral artery occlusion followed by reperfusion using the intraluminal filament technique. The diffusion-weighted images were collected, and areas of hyperintensity were compared with histologically assessed areas of ischemic injury. The magnetic resonance perfusion image series were postprocessed to produce topographic maps reflecting the maximum reduction in the signal obtained during the first passage of the contrast agent and the time delay between the arrival of the bolus and the point of maximum contrast-agent effect.
Results Hyperintensity in diffusion-weighted images was demonstrated after 30 minutes of middle cerebral artery occlusion and was mainly expressed in the lateral caudoputamen and parts of the lower frontoparietal cortex. Reperfusion after 45 minutes of occlusion reduced the area of hyperintensity from 24.2% to 9.9% of hemispheric area. In the group with 120 minutes of occlusion, the hyperintense area increased from 24.4% to 29.1%. Relative to the nonischemic hemisphere, the changes in the topographic maps of maximum signal reduction occurred in the lateral caudoputamen and adjacent lower neocortical areas. Increased time delay to maximum effect, however, was seen also in the upper frontoparietal cortex.
Conclusions Hyperintensity in diffusion-weighted images was reversible after 45 minutes but not after 120 minutes of middle cerebral artery occlusion. Analysis of the signal-reduction and time-delay parametric maps demonstrated regions of different perfusion changes in the ischemic hemisphere.
Journal Article•
TL;DR: The data suggest that the nitrate-induced changes in 99mTc-sestamibi perfusion imaging are useful to detect hibernating myocardium which recovers its function after revascularization.
Abstract: We tested the relationship of nitrate-induced changes in 99m Tc-sestamibi perfusion tomography and first-pass radionuclide angiocardiography (FPRNA) with postrevascularization functional recovery of asynergic territories. Methods : Twenty-eight patients, all with prior infarction and left ventricular dysfunction, underwent two 99m Tc-sestamibi rest studies : one under baseline conditions and the other with nitrate infusion. The baseline study was repeated after revascularization. Changes in global and regional perfusion and ventricular function were evaluated by perfusion tomography and FPRNA. Hibernating myocardium was identified by functional recovery in postrevascularization FPRNA. Results : Eleven patients and 31 segments in 19 coronary territories had functional recovery. Nitrate-induced FPRNA changes showed poor agreement with postrevascularization modifications : kappa = 0.24, ns, for the global and kappa = 0.32, p < 0.01 for regional function. The agreement between nitrate-induced and postrevascularization perfusion changes was good both considering the patients (k = 0.57, p < 0.01) and the abnormal coronary territories (k = 0.63, p < 0.0005). The agreement of nitrate-induced perfusion changes with postrevascularization functional outcome was excellent on a patient (k = 1, p < 0.0005), and coronary territory basis (k = 0.82, p < 0.0005). Conversely, the agreement between nitrate and postrevascularization FPRNA was poor : k = 0.18, ns. Conclusion : These data suggest that the nitrate-induced changes in 99m Tc-sestamibi perfusion imaging are useful to detect hibernating myocardium which recovers its function after revascularization.
TL;DR: The combination of functional information and good spatial detail afforded by computed tomography perfusion imaging means the technique is well suited for the evaluation of the human pancreas.
Abstract: Absolute quantification of pancreatic perfusion in man has been extremely difficult to date. This paper describes a relatively simple application of dynamic computed tomography to provide perfusion imaging of the human pancreas. Values for perfusion in eight normal pancreases ranged between 1.25 and 1.66 ml min" 1 ml" 1 (mean: 1.52 ml min" 1 ml" 1 ). Increased perfusion values were present in a patient with an islet cell tumour (overall perfusion 2.11 ml min" 1 ml" 1 ) and a patient with Wilson's disease (3.43 ml min" 1 ml" 1 ). Pancreatic perfusion was reduced in a patient with diabetes (0.60 ml min" 1 ml" 1 ) and in a failing pancreatic transplant (0.97 ml min" 1 ml" 1 ). The combination of functional information and good spatial detail afforded by computed tomography (CT) perfusion imaging means the technique is well suited for the evaluation of the human pancreas. It is currently the only technique which allows non-invasive absolute quantification of pancreatic perfusion.
TL;DR: In this article, a retrospective review of inpatients having a ventilation perfusion scan for suspected pulmonary embolism was performed at the New York Hospital-Cornell Medical Center.
Journal Article•
TL;DR: Perfusion imaging with TcN-NOET and 201Tl gives comparable diagnostic information in patients undergoing exercise testing for assessment of CAD because of the normalization of myocardial activity 4 hr after injection in some patients is concluded.
Abstract: UNLABELLED We compared TcN-NOET [bis(N-ethoxy, N-ethyl dithiocarbamato)nitrido 99mTc] and 201Tl images to estimate the utility of this compound in the detection of coronary artery disease (CAD). METHODS Twenty-five patients undergoing cardiac catheterization had stress-redistribution-reinjection 201Tl SPECT imaging, stress-delayed (2, 4 and 6 hr postinjection) and rest-delayed (4 hr postinjection) TcN-NOET SPECT imaging. RESULTS Nineteen patients had coronary stenosis > or = 50% and six were normal. Stress TcN-NOET and 201Tl imaging were concordant for the presence of CAD in 22/25 patients (88%, kappa = 0.76 +/- 0.20). The overall sensitivity of TcN-NOET SPECT imaging was 74% (14/19 patients) and 68% (13/19 patients) for 201Tl SPECT imaging. The specificity was 100% (6/6 patients) for both techniques. The overall agreement of TcN-NOET and 201Tl for the presence of disease in individual coronary arteries was 96% (72/75 arteries, kappa = 0.92 +/- 0.16). Segmental analysis of stress images showed a concordance in 211/225 segments (94%, kappa = 0.82 +/- 0.09). Comparison of the 4-hr images showed a concordance between 201Tl and TcN-NOET in 21/23 patients. Following TcN-NOET injection at rest, seven patients had a defect on the initial images, which had normalized 4 hr postinjection in four patients (57%). CONCLUSION Perfusion imaging with TcN-NOET and 201Tl gives comparable diagnostic information in patients undergoing exercise testing for assessment of CAD. Because of the normalization of myocardial activity 4 hr after injection in some patients, we conclude that TcN-NOET is a potential technetium compound equivalent to 201Tl.
TL;DR: The critical role of noninvasive testing in women is to diagnose CAD accurately in a population with a lower prevalence of disease prior to the development of more severe clinical manifestations when therapeutic interventions have a high risk and a poor outcome.
Abstract: Early reports of the prevalence, diagnosis, and outcomes of coronary artery disease (CAD) in women have led to the acceptance of several myths concerning noninvasive diagnostic studies in women. Many of the myths can be explained by age-related differences in prevalence, methodological errors that exclude women from enrollment, worse clinical baseline risk profiles, comorbid diseases at the time of interventions, and smaller coronary vessels. Awareness of these age-related prevalence factors in women and the potential for delaying the onset of CAD by estrogen treatment in postmenopausal women must be considered in assessing the accuracy of diagnostic studies. The critical role of noninvasive testing in women is to diagnose CAD accurately in a population with a lower prevalence of disease prior to the development of more severe clinical manifestations when therapeutic interventions have a higher risk and a poor outcome. Exercise radionuclide ventriculography has lower specificity in women, which may be due to gender differences in the response to excercise. Radionuclide perfusion imaging for the detection of CAD is accurate, there is extensive published literature, and it is used widely. High-dose dipyridamole in combination with echocardiography is not widespread in the United States; most pharmacologic echocardiographic studies are performed using dobutamine, and there are no reports on gender differences using dobutamine echocardiography. At this time, however, there is a paucity of published data on accuracy and no information on the prognostic value of this method. Both perfusion imaging and echocardiography have a better diagnostic accuracy than electrocardiographic stress testing. Myocardial perfusion imaging with thallium-201 or Tc-99m sestamibi identifies not just the presence or absence of CAD, it also prognostically identifies those patients with more severe disease who may benefit from invasive diagnostic testing and possible therapeutic interventions. Technetium-99m perfusion agents offer several advantages over thallium-201 : less attenuation, the ability to measure first-pass ejection fraction, and gated image acquisition. All 3 of these characteristics are expected to improve both sensitivity and specificity in women.
TL;DR: It is shown that deep hypothermic circulatory arrest with antegrade brain perfusion provides the best brain protection of the options investigated.
TL;DR: The DW imaging during early reperfusion showed a protective effect of postocclusion treatment with the free radical scavenger U74389G, and the improvement of time delay to maximum effect of the contrast agent observed in the perfusion imaging of the treatment group may reflect an improvement in the collateral flow to the ischemic tissue.
Abstract: Background and Purpose The present study was performed to examine the potential of diffusion-weighted (DW) imaging and dynamic first-passage bolus tracking of susceptibility contrast agents (perfusion imaging) for early in vivo evaluation of the effects of treatment with the free radical scavenger U74389G in a rat model of temporary focal ischemia.
Methods After 45 minutes of middle cerebral artery occlusion, the treatment group (n=9) received an infusion of U74389G, and the control group (n=9) received the identical volume of the vehicle. Reperfusion was instituted in both groups after 120 minutes of middle cerebral artery occlusion. The DW images were collected during middle cerebral artery occlusion and reperfusion and were compared with histologically assessed areas of tissue injury after 2 hours of reperfusion. The dynamic perfusion series were processed on a pixel-to-pixel basis to produce parametric maps reflecting the maximum reduction in the signal obtained during the first passage of the contrast agent and the time delay between the arrival of the bolus and the point of maximum contrast-agent effect.
Results The area of ischemic injury, as assessed from the DW imaging at 60 minutes of reperfusion, was significantly smaller in the treatment group: 9±8% of ipsilateral hemisphere compared with 19±8% in the control group. The histological examination after 2 hours of reperfusion demonstrated an area of ischemic injury of 10±8% for the treatment group compared to 25±10% in the control group. In the treatment group, the perfusion imaging showed a reduction in time delay to maximum effect of the contrast agent in the ischemic hemisphere compared with the control group.
Conclusions The DW imaging during early reperfusion showed a protective effect of postocclusion treatment with the free radical scavenger U74389G. The improvement of time delay to maximum effect of the contrast agent observed in the perfusion imaging of the treatment group may reflect an improvement in the collateral flow to the ischemic tissue.
TL;DR: Quantitative exercise thallium-201 tomography is highly reproducible and can be used to accurately interpret temporal changes in myocardial perfusion in individual patients and has the 95% confidence interval for exceeding the variability of the tomographic technique.
Abstract: The purpose of this study was to define the reproducibility of sequential quantitative exercise thallium-201 tomography. This was an ancillary study of a randomized, double-blind, placebo-controlled trial evaluating the shortterm efficacy of transdermal nitroglycerin patches in stable patients with angiographic coronary artery disease and no prior myocardial infarction. All 18 patients had a baseline tomographic perfusion defect involving ≥ 5% of the left ventricle after treadmill exercise. At a minimum of 3 days (mean 6.1 ± 1.8) after double-blind randomization to placebo, exercise thallium-201 tomography was repeated (study 2) using the same exercise protocol as in the baseline study (study 1). No significant differences in exercise parameters were observed from studies 1 to 2. Seventeen of 18 patients (94%) had an abnormal repeat exercise perfusion scan and 96% of initially abnormal vascular territories remained abnormal. The mean tomographic perfusion defect size was not significantly different from studies 1 (17.4 ± 13.3%) to 2 (16.6 ± 15.3%), nor were the components defined as scar and ischemia. A ≥ 10% change in total perfusion defect size in an individual patient defined the 95% confidence interval for exceeding the variability of the tomographic technique. Quantitative exercise thallium-201 tomography is highly reproducible and can be used to accurately interpret temporal changes in myocardial perfusion in individual patients.
TL;DR: 99mTc HM-PAO SPECT was carried out and interpreted in a consecutive series of 40 comatose patients with brain damage, without discontinuing therapy, and brain death was diagnosed in 7 patients, by recognising absence of brain perfusion, as shown by no intracranial radionuclide uptake.
Abstract: Diagnosis of brain death must be certain to allow discontinuation of artificial ventilation and organ transplantation. Brain death is present when all functions of the brain stem have irreversibly ceased. Clinical and electrophysiological criteria may be misinterpreted due to drug intoxication, hypothermia or technical artefacts. Thus, if clinical assessment is suboptimal, reliable early confirmatory tests may be required for demonstrating absence of intracranial blood flow. We have easily carried out and interpreted 99mTc HM-PAO SPECT in a consecutive series of 40 comatose patients with brain damage, without discontinuing therapy. Brain death was diagnosed in 7 patients, by recognising absence of brain perfusion, as shown by no intracranial radionuclide uptake. In patients in whom perfusion was seen on brain scans, HM-PAO SPECT improved assessment of the extent of injury, which in general was larger than suggested by CT.
Journal Article•
TL;DR: LHR, measured by 99mTc-sestamibi imaging, gives clinically useful information, both resting and postexercise values are correlated with ejection fraction and should predict left ventricular dysfunction.
Abstract: UNLABELLED Lung uptake of 201Tl is a reliable marker of left ventricular dysfunction. The goal of our study was to establish whether the evaluation of lung-to-heart uptake ratios (LHR) with 99mTc-sestamibi imaging may provide valuable information. METHODS We studied 72 male subjects with recent anterior myocardial infarction undergoing 99mTc-sestamibi first-pass ventriculography and SPECT perfusion imaging. A group of 46 gender-matched subjects with low pre-test likelihood of CAD and normal exercise and rest 99mTc-sestamibi perfusion images was used as a control. The lung-to-heart count ratios (LHR) were calculated on planar projections from the sets of SPECT images. RESULTS Both groups were studied at rest and after a symptom-limited exercise tolerance test. In the control group a significant decrease in LHR was observed during stress (p < 0.001). The infarcted group showed significantly higher LHR values both at rest and at stress. Exercise and rest LHR values did not differ significantly. A positive correlation was observed between LHR values and left ventricular ejection fraction at rest and stress. CONCLUSION LHR, measured by 99mTc-sestamibi imaging, gives clinically useful information. Both resting and postexercise values are correlated with ejection fraction and should predict left ventricular dysfunction.
TL;DR: It is suggested that perfusion imaging may be a valuable technique for investigating the mechanisms and extent of reperfusion injury.
TL;DR: Perfusion studies exhibited a trend toward lower cerebral blood volumes in patients with high grade extracranial carotid stenosis and lactate‐containing lesions, suggesting neuronal/axonal loss underlies the majority of T2‐weighted asymptomatic lesions in the older population.
Abstract: In the elderly, asymptomatic white matter hyperintensities are common on T2-weighted magnetic resonance imaging (MRI). In symptomatic patients, such MRI appearances correlate with varied postmortem findings including demyelination or stroke. What structural correlates underlie the T2 hyperintensities in patients whose lesions are asymptomatic is controversial. Therefore, in order to investigate the underlying metabolism and perfusion in white matter lesions (exhibiting T2 hyperintensity), 13 patients underwent proton magnetic resonance spectroscopy and dynamic gadolinium-DTPA perfusion-weighted MR imaging. N-acetyl aspartate (NA) levels were reduced in the lesions compared with age-matched controls (P = 0.031), implying neuronal/axonal loss. Creatine levels were also reduced (P = 0.001). Choline levels were unchanged in the lesions. Lactate was identified in the lesions of 5 of the 13 patients. Although not statistically significant, perfusion studies exhibited a trend toward lower cerebral blood volumes in patients with high grade extracranial carotid stenosis and lactate-containing lesions. These findings suggest that neuronal/axonal loss underlies the majority of T2-weighted asymptomatic lesions in the older population, and in many cases these changes may be due to chronic ischemia.