Showing papers on "Perfusion scanning published in 1997"
TL;DR: Experimental considerations in the implementation of quantitative perfusion imaging techniques for functional MRI using pulsed arterial spin labeling are described, finding three tagging techniques: EPISTAR, PICORE, and FAIR are found to give very similar perfusion results despite large differences in static tissue contrast.
Abstract: We describe here experimental considerations in the implementation of quantitative perfusion imaging techniques for functional MRI using pulsed arterial spin labeling. Three tagging techniques: EPISTAR, PICORE, and FAIR are found to give very similar perfusion results despite large differences in static tissue contrast. Two major sources of systematic error in the perfusion measurement are identified: the transit delay from the tagging region to the imaging slice; and the inclusion of intravascular tagged signal. A modified technique called QUIPSS II is described that decreases sensitivity to these effects by explicitly controlling the time width of the tag bolus and imaging after the bolus is entirely deposited into the slice. With appropriate saturation pulses the pulse sequence can be arranged so as to allow for simultaneous collection of perfusion and BOLD data that can be cleanly separated. Such perfusion and BOLD signals reveal differences in spatial location and dynamics that may be useful both for functional brain mapping and for study of the BOLD contrast mechanism. The implementation of multislice perfusion imaging introduces additional complications, primarily in the elimination of signal from static tissue. In pulsed ASL, this appears to be related to the slice profile of the inversion tag pulse in the presence of relaxation, rather than magnetization transfer effects as in continuous arterial spin labeling, and can be alleviated with careful adjustment of inversion pulse parameters. © 1997 John Wiley & Sons, Ltd.
596 citations
TL;DR: Tc-99m sestamibi SPECT perfusion imaging shows a significantly better specificity, which is further enhanced by the use of ECG gating, than Tl-201 SPECT studies, which had a similar sensitivity for the detection of CAD in women.
409 citations
TL;DR: Rapid perfusion imaging plays a key role in the risk stratification of low-risk patients, allowing discrimination of unsuspected high risk patients who require prompt admission and possible intervention from those who are truly at low risk.
403 citations
TL;DR: This study shows that MCE, with venous injection of contrast, can define the presence of CAD during rest and pharmacological stress and holds promise for the noninvasive assessment of myocardial perfusion in humans.
Abstract: Background The purpose of this study was to determine whether myocardial contrast echocardiography (MCE) can be used to detect coronary artery disease (CAD) during rest and pharmacological stress in humans through the use of venous injections of contrast. Methods and Results Thirty patients with known or suspected CAD underwent MCE and 99mTc-sestamibi single-photon emission computed tomography (SPECT) at baseline and after dipyridamole (0.56 mg · kg−1) infusion. Ten myocardial segments (5 each in the apical two- and four-chamber views) from the two sets of images using both methods were scored for myocardial perfusion as follows: 1=normal, 0.5=mildly reduced, and 0=severely reduced. The information from baseline and postdipyridamole images was then used to determine whether an abnormal segment was irreversible (similar abnormal perfusion at baseline and after dipyridamole) or reversible (perfusion better at baseline compared with after dipyridamole). Concordance between segmental scores was 92% (κ=.99) fo...
346 citations
TL;DR: Initial results suggest that early perfusion imaging using technetium-99m sestamibi enables reliable risk stratification of emergency department patients with possible cardiac ischemia and nondiagnostic ECGs.
195 citations
TL;DR: It is proved that transient response harmonic imaging could detect normal and abnormal myocardial perfusion in multiple echocardiographic windows with one intravenous injection of microbubbles in humans and can accurately identify regional myocardIAL perfusion abnormalities.
178 citations
TL;DR: In this article, the authors evaluated regional cerebral perfusion with either technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO) or 99m Tc-ethyl cysteinate dimer (99 mTc -ECD) and striatal dopamine transporter density using iodine-123 2 beta-carboxymethoxy-3 beta-[4-iodophenyl]tropane (123I-beta-CIT) SPET.
Abstract: Dementia of the Alzheimer-type (DAT) is characterized by progressive cognitive decline, variably combined with frontal lobe release signs, parkinsonian symptoms and myoclonus. The features of diffuse Lewy body disease (DLBD), the second most common cause of degenerative dementia, include progressive cognitive deterioration, often associated with levodopa-responsive parkinsonism, fluctuations of cognitive and motor functions, psychotic symptoms (visual and auditory hallucinations, depression), hypersensitivity to neuroleptics and orthostatic hypotension. A recent report suggests that positron emission tomography studies in patients with degenerative dementia may be useful in the differential diagnosis of DAT and DLBD. However, the diagnostic role of single-photon emission tomography (SPET) studies remains to be established. The aim of this study was therefore to evaluate regional cerebral perfusion [with either technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO) or 99mTc-ethyl cysteinate dimer (99mTc-ECD) SPET] and striatal dopamine transporter density [using iodine-123 2 beta-carboxymethoxy-3 beta-[4-iodophenyl]tropane (123I-beta-CIT) SPET] in patients with DAT and DLBD. Six patients with probable DAT and seven patients with probable DLBD were studied. Blinded qualitative assessment by four independent raters of 99mTc-HMPAO or 99mTc-ECD SPET studies revealed bilateral temporal and/or parietal hypoperfusion in all DAT patients. There was additional frontal hypoperfusion in two patients and occipital hypoperfusion in one patient. In the DLBD group, regional cerebral perfusion had a different pattern. In addition to temporoparietal hypoperfusion there was occipital hypoperfusion resembling a horseshoe defect in six of seven patients. In the DAT group, the mean 3-h striatal/cerebellar ratio of 123I-beta-CIT binding was 2.5 +/- 0.4, with an increase to 5.5 +/- 1.1 18 h after tracer injection. In comparison, in the DLBD patients the mean 3-h striatal/cerebellar ratio of 123I-beta-CIT binding was significantly reduced to 1.7 +/- 0.3, with a modest increase to 2.1 +/- 0.4 18 h after tracer injection (P < 0.05, Scheffe test, ANOVA). These results suggest that 99mTc-HMPAO or 99mTc-ECD and 123I-beta-CIT SPET may contribute to the differential diagnosis between DAT and DLBD, showing different perfusion patterns and more severe impairment of dopamine transporter function in DLBD than in DAT.
174 citations
TL;DR: A computer program called AVERAGE is developed which can be used with various TCD devices and allows for subtle quantitative off-line analysis of Doppler flow signals and supports data transformation, heart beat analysis, noise reduction, trigger signal and marker modification, artifact analysis and artifact rejection, as well as data reduction.
143 citations
TL;DR: Radiation therapy-induced regional lung dysfunction occurs in a dose-dependent manner and develops within 3-6 months following radiation and in contrast to classical "sigmoid" dose-response curves, these data suggest a more gradual relationship between regional dysfunction and RT dose.
Abstract: Purpose: To better understanding the dose and time dependence of radiation therapy (RT)-induced regional lung dysfunction as assessed by changes in regional lung perfusion. Methods and Materials: Patients who were to receive RT for tumors in and around the thorax, wherein portions of healthy lung would be incidentally irradiated, were prospectively studied. Regional function was assessed pre- and post-RT with single photon emission computed tomography (SPECT) lung perfusion scans, obtained following the intravenous administration of ∼4 mCi of technetium-99m macroaggregated albumin. Pre-RT computed tomography (CT) scans were used to calculate the three-dimensional (3D) dose distribution, reflecting tissue density inhomogeneity corrections. Each SPECT scan was correlated with the pre-RT CT scan, and the 3D dose distribution. Changes in regional lung perfusion were correlated with regional Rt dose, at various time intervals following radiation. Results: The data from 20 patients (7 breast cancer, 5 lymphoma, 1 esophagus, 1 sarcoma, and 6 lung cancer) have been analyzed. Patients with gross intrathoracic lung cancers causing obstruction of regional pulmonary arteries were not included. For most patients, there is a statistically significant dose-dependent reduction in regional blood flow at all time points following radiation. While a time dependence is suggested in the high dose range, the limited amount of data prevents meaningful statistical evaluation. Conclusions: Radiation therapy-induced regional lung dysfunction occurs in a dose-dependent manner and develops within 3–6 months following radiation. In contrast to classical "sigmoid" dose-response curves, desribed mainly for changes following whole lung irradiation, these data suggest a more gradual relationship between regional dysfunction and RT dose. Retraction of irradiation lung with secondary movement of unirradiated lung into the "3D-defined irradiated volume" may have introduced inaccuracies into this analysis. Additional studies are currently underway to asses this possibility and better refine this dose-response curve. Studies are underway to determine if changes in assessment of whole lung function, such as pulmonary function tests, can be predicted by summing the regional changes observed.
131 citations
TL;DR: Although TES was the most powerful predictor of HT, SPECT is the best single adjunct to the triage of clinical and CT tests to identify patients at risk for spontaneous HT.
Abstract: Background and Purpose Hemorrhagic transformation (HT) is a common evolution of large-volume ischemic lesions, particularly of cardioembolic origin. We used transcranial Doppler ultrasound (TCD), single-photon emission computed tomography (SPECT) with 99mTc–hexamethylpropyleneamine oxime (HMPAO), and the Toronto Embolic Scale (TES) to decide (1) whether TCD, HMPAO-SPECT, and TES can improve on clinical and CT tests to predict spontaneous HT and (2) whether SPECT can help to predict the outcome of symptomatic HT. Methods Prognostic criteria included Canadian Neurological Scale (CNS) scores ≤50 on admission, early ischemic changes on CT, M1 middle cerebral artery occlusion on TCD, the focal absence of brain perfusion on SPECT, and a high risk of cardiogenic embolism on TES. Results In part 1, 85 consecutive patients admitted within the first 6 hours were studied. No patient received thrombolysis. HT was found in 11 patients (13%) at 3 to 5 days. Admission CNS and CT were not predictive of HT: odds ratios (9...
125 citations
TL;DR: Increased arterial perfusion appears to be an indicator of liver metastases, whereas reduced portal perfusion may indicate progressive disease.
Abstract: PURPOSE: To assess changes in hepatic perfusion in patients with colorectal cancer with computed tomography (CT), diagnostic potential of CT perfusion measurements, and implications for design of contrast enhancement protocols. MATERIALS AND METHODS: In 27 patients with colorectal cancer, arterial and portal perfusion were calculated from temporal changes in attenuation after intravenous administration of contrast material. RESULTS: Arterial perfusion greater than 0.25 mL/min/mL was seen in nine (82%) of the 11 patients with overt metastases versus six (38%) of the 16 patients with no overt metastases (P < .05). Portal perfusion of 0.25 mL/min/mL or less was found in five (46%) of the patients with overt metastases versus three (19%) of the patients with no overt metastases. Follow-up imaging showed progressive metastatic disease in three patients, all of whom had decreased portal perfusion. CONCLUSION: Increased arterial perfusion appears to be an indicator of liver metastases, whereas reduced portal per...
TL;DR: Functional MRI perfusion imaging of intraaxial tumors is analogous to positron emission tomography for delineation of metabolic activity, yet may be even more sensitive to neovascularity and possesses improved image quality.
Abstract: Contrast agents have greatly expanded the role of MR imaging (MRI) to allow assessment of physiologic, or "functional," parameters. Although activation mapping generally does not require contrast agents, other forms of functional MRI, including mapping of cerebral hemodynamics (eg, perfusion imaging), are best done with the use of contrast agents. Serial echo planar images are obtained after bolus injection of lanthanide chelates. Application of susceptibility contrast physics and standard tracer kinetic principles permits generation of relative cerebral blood volume maps. Deconvolution of cerebral blood flow and mean transit time parameters is also possible within technical limitations. By using diffusion and perfusion pulse sequences, an imaging correlate to the ischemic penumbra can be identified. Functional MRI perfusion imaging of intraaxial tumors is analogous to positron emission tomography for delineation of metabolic activity, yet may be even more sensitive to neovascularity and possesses improved image quality. Clinical applications include biopsy site selection and postirradiation follow-up. Further improvements in data analysis and map generation techniques may improve diagnostic accuracy and utility.
TL;DR: It is concluded that preexisting hyperglycemia increases acute postischemic MRI-measurable brain cellular injury in proportion to an associated increased microvascular ischemia.
Abstract: Magnetic resonance imaging (MRI) techniques were used to determine the effect of preexisting hyperglycemia on the extent of cerebral ischemia/reperfusion injury and the level of cerebral perfusion. Middle cerebral artery occlusion (MCAO) was induced by a suture insertion technique. Forty one rats were divided into hyperglycemic and normoglycemic groups with either 4 hours of continuous MCAO or 2 hours of MCAO followed by 2 hours of reperfusion. Diffusion-weighted imaging (DWI) was performed at 4 hours after MCAO to quantify the degree of injury in 6 brain regions. Relative cerebral blood flow (CBF) and cerebral blood volume (CBV) were estimated using gradient echo (GE) bolus tracking and steady-state spin echo (SE) imaging techniques, respectively. Brain injury correlated with the perfusion level measured in both SE CBV and dynamic GE CBF images. In the temporary MCAO model, mean lesion size in DWI was 118% larger and hemispheric CBV was reduced by 37% in hyperglycemic compared with normoglycemic rats. Hyperglycemia did not significantly exacerbate brain injury or CBV deficit in permanent MCAO models. We conclude that preexisting hyperglycemia increases acute postischemic MRI-measurable brain cellular injury in proportion to an associated increased microvascular ischemia.
TL;DR: The noninvasive EPISTAR technique can assess perfusion abnormalities similarly to the T2 *-WGE perfusion technique and may provide a valuable alternative in the diagnosis of acute stroke patients.
Abstract: Article abstract-Purpose: To compare echo-planar imaging with signal targeting and alternating radiofrequency (EPISTAR), an arterial spin-labeling technique, to a T 2 *-weighted gadolinium-enhanced (T 2 *-WGE) MR perfusion technique for the evaluation of acute cerebrovascular disease. Method: Twenty-one EPISTAR and T sub 2 *-WGE perfusion studies were performed on 18 patients with the clinical diagnosis of acute stroke (12 men, 6 women, age range 34 to 89 years, mean age 68 years). For qualitative analysis, perfusion studies of both techniques were grouped into categories (hyperperfusion, normal perfusion, delayed perfusion, or absent perfusion) and compared with a Wilcoxon signed rank test. Quantitative analysis was performed using signal intensity measurements in a region of interest that was defined by diffusion-weighted imaging abnormalities. These signal intensity measurements were compared with a mirror region in the contralateral unaffected hemisphere. Signal intensity ratios (infarcted region versus the unaffected contralateral region) were calculated and compared using a paired t test. Results: Qualitative analysis demonstrated agreement between the two techniques in 17 of 21 studies (hyperfusion, n = 3 patients; normal perfusion, n = 3; delayed perfusion, n = 4; and absent perfusion, n = 7). In four studies, the two techniques disagreed when EPISTAR demonstrated absent and T 2 *-WGE perfusion demonstrated delayed perfusion (p > 0.05). Quantitative analysis revealed a mean signal intensity ratio of 0.73 +/- 0.79 for the T 2 *-WGE perfusion technique and 0.69 +/- 0.68 for the EPISTAR technique (p > 0.05). Conclusion: The noninvasive EPISTAR technique can assess perfusion abnormalities similarly to the T 2 *-WGE perfusion technique and may provide a valuable alternative in the diagnosis of acute stroke patients. Differences between the two techniques can be explained by the applied inflow times in the EPISTAR technique. NEUROLOGY 1997;48: 673-679
TL;DR: T2*-weighted perfusion imaging exploits the susceptibility-mediated signal intensity loss of a first-pass bolus of gadopentetate dimeglumine within the capillary bed, which is promising in the differentiation of benign from malignant, rapidly enhancing lesions.
Abstract: PURPOSE: To evaluate the differentiation of benign from malignant breast tumors with T2*-weighted perfusion magnetic resonance (MR) imaging (blood volume imaging) versus that with dynamic T1-weighted contrast agent-enhanced MR imaging. MATERIALS AND METHODS: Ten healthy adult volunteers and 18 adult patients with benign or malignant lesions underwent both conventional T1-weighted dynamic contrast-enhanced breast MR imaging and repetitive first-pass, single-section, dynamic T2*-weighted perfusion MR imaging. Images were obtained before, during, and after injection of 20 mL of gadopentetate dimeglumine; peak gadopentetate dimeglumine concentrations were calculated from the maximal signal intensity loss on T2*-weighted images. RESULTS: No perfusion effect was detectable in healthy breast parenchyma. A strong susceptibility-mediated signal intensity loss occurred in malignant breast tumors. No or only minor perfusion effects were seen in fibroadenomas, in spite of their rapid enhancement at T1-weighted dynami...
TL;DR: The SCAN model strategy for initial management of emergency department patients with typical ongoing angina and a normal or nondiagnostic ECG using initial myocardial perfusion imaging with technetium-99m sestamibi appears to be safe, accurate, and potentially cost effective.
Abstract: Previous investigations have confirmed the diagnostic and predictive usefulness of initial single-photon emission computed tomography (SPECT) myocardial perfusion imaging using technetium-99m sestamibi in the evaluation of emergency department patients with chest pain. Patients with a normal SPECT perfusion scan performed during chest pain have an excellent short-term prognosis, and may be candidates for expeditious cardiac evaluation or outpatient management. However, there are limited data regarding the cost effectiveness of this technique. This analysis models the potential cost effectiveness of this procedure. In the current investigation we compared 2 model strategies for management of emergency department patients with typical chest pain and a normal or nondiagnostic electrocardiogram (ECG). In 1 model strategy, (the technetium-99m sestamibi SPECT myocardial perfusion imaging [SCAN] strategy), the decision whether to admit or discharge a patient from the emergency department is based on results of initial technetium-99m sestamibi SPECT myocardial imaging. Patients with normal scans are discharged; others are admitted. In the second model strategy, (the NO SCAN strategy), the decision whether or not to admit a patient is based on a combination of clinical and electrocardiographic variables. Patients with ≥3 cardiac risk factors or an abnormal ECG are admitted; others are discharged. Adverse cardiac events were prospectively defined as cardiac death, nonfatal myocardial infarction, or the need for acute coronary intervention. Costs were assigned using data derived from 102 patients who underwent SPECT myocardial perfusion imaging and an additional 107 emergency department patients with ongoing chest pain who either underwent or were eligible for initial SPECT myocardial perfusion imaging. Mean (± SE) costs were highest among hospital admitted patients who experienced an adverse cardiac event ($21,375 ± $2,733) and lowest in patients discharged from the emergency department ($715 ± 71). Mean costs per patient of the SCAN strategy and NO SCAN strategy were $5,019 versus $6,051, respectively. These results were stable in a sensitivity analysis across a range of costs and predictive values. Thus, the SCAN model strategy for initial management of emergency department patients with typical ongoing angina and a normal or nondiagnostic ECG using initial myocardial perfusion imaging with technetium-99m sestamibi appears to be safe, accurate, and potentially cost effective. Validation of these preliminary retrospective observations will require further prospective investigation. Technetium 99-m sestamibi single-photon emission computed tomography (SPECT) myocardial perfusion imaging is a more sensitive and specific predictor of acute cardiac events than routine clinical assessment among selected emergency department patients with chest pain. This study suggests that a management strategy using initial technetium 99-m sestamibi SPECT results to triage emergency department patients with typical angina and a normal or nondiagnostic electrocardiogram for admission or discharge could potentially reduce health care costs.
TL;DR: MR perfusion imaging was feasible for detection of perfusion defects distal to a pulmonary embolism and showed a reduced peak signal intensity during first passage of the contrast agent.
Abstract: PURPOSE: To evaluate the feasibility of magnetic resonance (MR) perfusion imaging in the human lung to help detect perfusion defects distal to suspected pulmonary embolism. MATERIALS AND METHODS: Seven patients suspected of having pulmonary embolism first underwent ventilation-perfusion lung scintigraphy followed by MR perfusion imaging with rapid acquisition of two sets of dynamic images in the coronal and transaxial planes. A bolus of 0.05 mmol per kilogram of body weight gadopentetate dimeglumine or gadodiamide was administered. Single images obtained in each section that showed peak signal intensity from the first passage of contrast material were evaluated visually. An analysis of change in signal intensity over time was performed both on a pixel-by-pixel basis and in selected regions of interest. RESULTS: In the seven patients, a total of 18 regions of lung tissue with perfusion defects were shown on the ventilation-perfusion scans. In 16 of these regions, MR perfusion images showed a reduced peak signal intensity during first passage of the contrast agent. Perfusion defects could be detected in both the coronal and the transaxial planes on MR perfusion images. CONCLUSION: MR perfusion imaging was feasible for detection of perfusion defects distal to a pulmonary embolism.
TL;DR: In multiple brain regions, including the temporal lobes, AD patients showed robust and significant increases in perfusion in response to carbon dioxide that did not differ from the response seen in the controls.
Abstract: Studies of Alzheimer's disease using single-photon emission computed tomography (SPECT) and positron emission tomography (PET) have found reductions in blood flow and glucose metabolism in temporal and parietal cortex. In 50 AD patients who underwent neuropsychological testing and SPECT perfusion imaging, we found significant correlations between perfusion and performance on the Mini-Mental Status Examination in the frontal and parietal lobes. In addition. specific correlations between perfusion in the frontal lobes and performance on tests of frontal lobe ability were noted. These findings, while suggesting the importance of perfusion measures in determining clinical features of the disease, do not clearly define perfusion changes as primary, since similar findings have been seen when metabolism is studied. In a separate group of 5 AD patients and 16 controls, we used PET with the perfusion tracer HIPDM and examined cerebrovascular reactivity to carbon dioxide inhalation. We found that in multiple brain regions, including the temporal lobes, AD patients showed robust and significant increases in perfusion in response to carbon dioxide that did not differ from the response seen in the controls. Taken together, these results show that while perfusion changes are important in AD, they are not clearly either primary or limiting.
TL;DR: Transient or fixed LV dilation are commonly seen during dipyridamole Tc-99m sestamibi SPECT imaging and are useful predictors of cardiac events.
Abstract: Left ventricular (LV) cavity dilation during stress myocardial perfusion imaging has been associated with multivessel disease, and may be an independent prognostic marker in addition to perfusion defects. The present study examines the predictive value for future cardiac events of transient or fixed LV dilation during dipyridamole technetium-99m (Tc-99m) sestamibi single-photon emission computed tomography (SPECT) imaging. The study included 512 consecutive patients who underwent SPECT imaging with Tc-99m sestamibi after dipyridamole infusion. Transient LV dilation was seen in 70 patients (14%) and 74 had fixed cavity dilation (14%); cavity size was normal in 368 patients (72%). Each perfusion scan was classified as normal or abnormal, and if abnormal, defects were categorized as transient or fixed, and as small, medium, or large (depending upon the number of abnormal vascular territories). Events during a mean follow-up of 12.8 +/- 6.8 months were tabulated by direct review of hospital charts and death certificates. The cardiac event rate (cardiac death or nonfatal infarction) was 1.9% in patients with normal cavity size, 11.4% with transient LV dilation, and 13.5% with fixed LV dilation (p < 0.01). Compared with patients with normal cavity size, those with transient LV dilation were more likely to sustain a myocardial infarction (p < 0.01) and those with fixed dilation more frequently suffered cardiac death (p < 0.01) and hospitalization for heart failure (p < 0.01). The group with the highest risk had both a large perfusion defect and cavity dilation. By Cox proportional hazard regression analysis, both transient and fixed LV dilation were strong independent predictors of cardiac events. Transient or fixed LV dilation are commonly seen during dipyridamole Tc-99m sestamibi SPECT imaging (14% incidence for each) and are useful predictors of cardiac events.
TL;DR: The important effect of lithium withdrawal on brain perfusion implies that after withdrawal of lithium, the brain develops an abnormal state of activity in limbic cortex.
Abstract: BACKGROUND Early manic relapse following lithium discontinuation offers an important opportunity to investigate the relationship between symptoms, effects of treatment and regional brain activation in bipolar affective disorder.
METHOD Fourteen stable bipolar patients on lithium were examined with neuropsychological measures, clinical ratings and single photon emission computed tomography (SPECT) before and after acute double-blind withdrawal of lithium. Brain perfusion maps were spatially transformed into standard stereotactic space and compared pixel-by-pixel. A parametric analysis was used to examine the change in brain perfusion on lithium withdrawal, and the relationship between symptom severity and brain perfusion separately both between and within subjects.
RESULTS Lithium withdrawal was associated with an important redistribution of brain perfusion, with increases in inferior posterior regions and decreases in limbic areas, particularly anterior cingulate cortex. Seven of the 14 patients developed manic symptoms during the placebo phase, correlating with relative increases in perfusion of superior anterior cingulate and possibly left orbito-frontal cortex.
CONCLUSIONS The important effect of lithium withdrawal on brain perfusion implies that after withdrawal of lithium, the brain develops an abnormal state of activity in limbic cortex. The structures involved did not co-localise with those apparently modulated by manic symptoms.
TL;DR: Improvement of wall motion at low and high doses of dobutamine was highly correlated with myocardial viability on PET and was more common in myocardium with normal perfusion than in those with mildly reduced tracer uptake.
TL;DR: Routine use of relative CBV maps that can be implemented on any high-field MR unit and added to the regular MR evaluation provides useful functional information in patients with brain tumors and is more sensitive than the other modalities for early prediction of tumor growth.
Abstract: ✓ It was recently demonstrated that imaging of brain tumors by relative cerebral blood volume (CBV) maps reconstructed from dynamic magnetic resonance (MR) data provide similar diagnostic information compared to positron emission tomography (PET) or 201Tl single-photon emission computerized tomography (201Tl-SPECT) scans. The authors used relative CBV mapping for routine follow-up evaluation of patients with brain tumors and compared its sensitivity to diagnostic MR imaging, 201Tl-SPECT and clinical assessment. Fifty-nine patients were prospectively followed using 191 concomitant studies of dual section relative CBV maps, MR imaging, 201Tl-SPECT, and neurological evaluations. Studies were repeated every 2 to 3 months (median three evaluations/patient). The relative CBV maps were graded as relative CBV 0 to 4, where Grades 3 and 4 are indicative of proliferating tumors (four = rapid leak). There were 44 high-grade and 15 low-grade tumors followed during treatment. During the follow-up period a change in re...
TL;DR: Changes in the slice profile of the adiabatic inversion induced by relaxation effects are shown to cause signal variations in pulsed arterial tagging schemes on the order of magnitude of perfusion changes, and result in gross errors in perfusion quantitation.
Abstract: Imperfections in the slice profile of the adiabatic inversion induced by relaxation effects are shown to cause signal variations in pulsed arterial tagging schemes on the order of magnitude of perfusion changes, and result in gross errors in perfusion quantitation. Significant improvement can be made with minor modifications to the inversion pulse which facilitate the acquisition of quantitative, multislice perfusion images, as demonstrated in both a phantom and a normal human volunteer.
TL;DR: MR perfusion imaging of renal allografts can be used to noninvasively differentiate ATN from AAR during the post-transplant period, and may also be helpful in cases were covert AAR is superimposing ATN during a phase of anuria.
TL;DR: In patients with microvascular dysfunction the MR studies show for the first time that the myocardial perfusion reserve correlates with Doppler flow measurements, and the proposed modeling approach are sufficiently robust for fitting of tissue residue curves corresponding to a wide, physiologically realistic range of myocardIAL blood flows.
Abstract: Recent advances with fast switching gradient coils, and the optimization of magnetic resonance techniques for multi-slice imaging have made it possible to apply models of contrast agent transit for the quantification of myocardial perfusion, and determination of the transmural distribution of blood flow. This article summarizes some of these recent developments and presents examples of quantitative, multi-slice myocardial perfusion imaging studies in patients and animal models. Multi-slice, true first pass imaging, with high temporal resolution, and T1-weighted, arrhythmia insensitive contrast enhancement is used for the quantification of perfusion changes accompanying mild to severe ischemia. The first pass imaging technique and the modeling approach are sufficiently robust for fitting of tissue residue curves corresponding to a wide, physiologically realistic range of myocardial blood flows. In animals this was validated by comparison to blood flow measurements with radiolabeled microspheres as gold standard. It is demonstrated that with the proposed modeling approach one can determine the myocardial perfusion reserve from two consecutive MR first pass measurements under resting and hyperemic conditions. In patients with microvascular dysfunction the MR studies show for the first time that the myocardial perfusion reserve correlates with Doppler flow measurements (linear regression with slope of 1.02±0.09; r=0.80). Since perfusion limitations usually begin in the subendocardium as coronary flow is gradually reduced, first pass imaging with the prerequisitie spatial and temporal resolution allows early detection of a mild coronary stenosis.
TL;DR: World depression severity and an independent ‘vital’ depression factor were associated in subjects with increased perfusion in cingulate and other paralimbic areas and there was a probable association between an increase in an anxious-depression factor and reduced frontal neocortical perfusion.
Abstract: BACKGROUND The spontaneous diurnal variation of mood and other symptoms provides a substrate for the examination of the relationship between symptoms and regional brain activation in depression.
METHOD Twenty unipolar depressed patients with diurnal variation of mood were examined at 8 a.m. and 8 p.m. with neuropsychological measures, clinical ratings and single photon emission tomography (SPET). Brain perfusion maps were spatially transformed into standard stereotactic space and compared pixel-by-pixel. A parametric (correlational) analysis was used to examine the relationship between symptom severity and brain perfusion, both between and within subjects.
RESULTS Global depression severity and an independent 'vital' depression factor were associated in subjects with increased perfusion in cingulate and other paralimbic areas. In addition there was a probable association between an increase in an anxious-depression factor and reduced frontal neocortical perfusion.
CONCLUSIONS Depressive symptom changes are associated with metabolic changes in the cingulate gyrus and associated paralimbic structures.
TL;DR: This technique has the potential to reduce health-care costs by reducing the number of unnecessary coronary angiographies that are now performed on patients with equivocal results of perfusion or incomplete risk stratification from standard myocardial perfusion SPECT.
TL;DR: The novel method not only provides similar perfusion information to that obtained by EPISTAR, as demonstrated in the functional brain imaging study, but also eliminates magnetic susceptibility artifacts and image distortion commonly observed in EPI images.
Abstract: A novel magnetic resonance imaging technique (STAR-HASTE) based on pulsed arterial spin labeling using a single shot acquisition method is described for perfusion imaging. The method is similar to EPISTAR in using STAR (Signal Targeting with Alternating Radiofrequency) technique for pulsed radiofrequency labeling of inflowing blood, but uses a half-Fourier single shot turbo spin-echo (HASTE) sequence for data acquisition instead of echo-planar imaging (EPI). Our preliminary studies show that STAR-HASTE permits perfusion imaging to be performed without many of the artifacts encountered with other imaging methods based on EPI acquisition. The novel method not only provides similar perfusion information to that obtained by EPISTAR, as demonstrated in the functional brain imaging study, but also eliminates magnetic susceptibility artifacts and image distortion commonly observed in EPI images. Furthermore, this technique can be readily implemented in MR systems without EPI capability.
Book•
01 Sep 1997
TL;DR: Introduction to functional CT computer handling of CT data for functional studies evaluation of CT systems for functional imaging contrast medium as a "tracer" physiological models.
Abstract: Introduction to functional CT computer handling of CT data for functional studies evaluation of CT systems for functional imaging contrast medium as a "tracer" physiological models perfusion CT - technique perfusion CT - normal organs perfusion CT - clinical applications renal function cardiac function blood-brain imaging.
TL;DR: The safety of intravenous thrombolysis with the recombinant tissue plasminogen activator (rTPA) and potential solutions offered by single-photon emission CT (SPECT) as a noninvasive brain perfusion imaging modality are addressed.
Abstract: Background To reliably identify patients at risk for symptomatic hemorrhagic transformation (SHT), future trials of thrombolysis for acute ischemic stroke might use a vascular imaging protocol applicable to a multicenter setting. The goal of this commentary is to address the safety of intravenous thrombolysis with the recombinant tissue plasminogen activator (rTPA) and potential solutions offered by single-photon emission CT (SPECT) as a noninvasive brain perfusion imaging modality.
Summary of Review Even if patients with severe stroke, extensive ischemic changes on CT scan, advanced age, and high blood pressure are excluded from thrombolytic therapy, this cannot completely guarantee the safety of using rTPA. Brain SPECT scanning with hexamethylpropyleneamine oxime (HMPAO) may help to screen out patients at risk if performed in addition to clinical and CT tests. The knowledge of pretreatment severity, extent, and location of ischemia might identify good versus poor responders to rTPA therapy. HMPAO-SPECT is widely available and feasible to perform without delaying rTPA therapy. Rigorous quality control and use of reproducible visual and semiquantitative methods of interpreting SPECT are necessary for implementation of SPECT technology in multicenter clinical trials.
Conclusions The major obstacle to general acceptance of thrombolytic therapies and rTPA in particular is the fear of symptomatic hemorrhagic transformation, and because HMPAO-SPECT might reliably identify patients at high risk of symptomatic hemorrhagic transformation, the clinical value of HMPAO-SPECT in patient selection for thrombolysis during the first hours of acute ischemic stroke should be determined through a prospective clinical trial.