Performance characteristics of gamma cameras.
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Calibration↗
Biomedical subjects
J T Kuikka
Publications and source records attributed to J T Kuikka.
Heterogeneity of cerebral blood flow in symptomatic patients undergoing carotid endarterectomy.
There is still controversy concerning which patients with asymptomatic carotid stenosis or symptomatic moderate stenosis are likely to benefit from carotid endarterectomy. The surgical candidates for carotid endarterectomy should have a high risk for stroke, but a low risk for operative complications. Therefore, new effective patient selection strategies, including haemodynamic testing, schemes of risk stratification and pre-operative cardiac testing, are under investigation. To improve haemodynamic assessment of patients with carotid artery stenosis, we evaluated a novel global cerebral blood flow (CBF) heterogeneity index at rest and after acetazolamide injection in patients undergoing carotid endarterectomy. CBF heterogeneity index was measured in 15 patients by using basal and acetazolamide enhanced 99mTc-HMPAO SPET both before and 1 month after surgery. CBF heterogeneity index was calculated as the coefficient of variation of a total of 44 cerebral regions representing mainly both ipsi- and contralateral grey matter. A high linear correlation was observed between CBF heterogeneity index and ipsilateral carotid stenosis degree (r=0.74, P=0.003). Before surgery, CBF heterogeneity index increased significantly after acetazolamide injection when compared to the basal condition (from 7.0+/-1.5 to 8.3+/-1.7%, P=0.008). This response disappeared after carotid endarterectomy. When compared to pure asymmetry of CBF (ipsi/contralateral CBF ratio), the CBF heterogeneity index seemed to reflect, more sensitively, the haemodynamic effects of carotid endarterectomy. The CBF heterogeneity index after acetazolamide injection is a sensitive marker of the haemodynamic consequences of carotid artery stenosis and its operative treatment.
Acetazolamide↗
Effect of flow and vascular heterogeneity on glucose metabolism in isolated dog hearts.
In non-ischaemic myocardium glucose uptake is assumed to be proportional to blood flow. We investigated the effect of regional vascular heterogeneity on glucose metabolism at various flow rates in the isolated blood-perfused dog hearts. Aortic bolus injections contained an intravascular reference tracer (albumin) and two of three glucoses: L-glucose (an extracellular tracer), D-glucose and 2-deoxy-D-glucose. Flow ranged from 0.5 to 2 4 ml min(-1) g(-1). Vascular heterogeneity was calculated from the albumin outflow dilution curve. A three-region convection-diffusion from the abumin outflow dilution curve. A three-region, convection-diffusion model was fitted to outflow dilution curves to estimate glucose metabolic rate (consumption). The results of 2-deoxy-D-glucose experiments showed that the lumped constant was dependent on flow, glucose metabolic rate was proportional to flow and dependent on the heterogeneity of the myocardial vasculature. The results support the views that without accounting the regional flow heterogeneity, glucose metabolic rate will be underestimated.
Albumins↗
PET imaging using a triple-head gamma camera.
Interest in clinical fluorodeoxyglucose (FDG) imaging with multiple-head gamma cameras is growing. To improve sensitivity, triple-head coincidence imaging has been proposed. We report our initial experiences with a triple-head coincidence gamma camera with 19 mm sodium iodide crystal thickness. Several positron emission tomography-image quality parameters were evaluated using a Carlson and line source phantom. The system sensitivity with two-dimensional axial shields was 830 cps kBq-1 ml-1 and maximum noise equivalent count rate 1900 cps for an 18F-activity of 50 MBq. The imaging resolution was in central axial 7.0 mm and in central transaxial 7.6 mm, respectively. The average scatter fraction in scattered media was 29%. Clinical brain, heart and whole body images studies with [18F]FDG were acquired and they show good correlation with the phantom image quality. As a conclusion, triple-head coincidence gamma camera provides relatively high-count rate imaging with good contrast and resolution.
Adult↗
Myocardial fatty acid utilisation during exercise induced ischemia in patients with coronary artery disease.
AIM: Reversible or irreversible myocardial damage due to ischemia correlates with altered membrane functions of the cells. To compare myocardial free fatty acid (FFA) metabolism and flow during exercise induced ischemia we studied ten patients with coronary artery disease but without previous myocardial infarction. METHODS: A series of post-exercise single-photon emission computed tomography (SPECT) measurements was performed after injection of 123I labelled heptadecanoic acid (HDA). Myocardial perfusion was estimated from the separately performed exercise-redistribution thallium study. Fatty acid metabolic rate, thallium uptake and washout were calculated for anterior, lateral, posterior and septal segments. RESULTS: The more reduced post-exercise FFA metabolic rate (-63 +/- 18%, mean +/- 1 SD) compared to flow (-36 +/- 16%) was related to the severity of myocardial ischemia and wall motion abnormalities. CONCLUSION: In this small group of patients, the reduced post-exercise FFA metabolic rate tentatively suggests a parsimonious workload of the exercising myocardium by reducing oxygen consumption in patients with coronary artery disease.
Coronary Disease↗
Imaging of the endothelial dysfunction in coronary atherosclerosis.
Coronary endothelial dysfunction is characterised by coronary vasoconstrictive responses to endothelium-dependent vasodilators. It is associated with coronary artery disease (CAD) and is considered an early phase of coronary atherosclerosis. Patients with CAD benefit from vigorous risk factor interventions and medical treatment, with a marked decrease in coronary events and an improvement in survival that are not reported following revascularisation procedures. Therefore, early detection of anatomical and functional changes in the coronary vasculature due to atherosclerosis provides the basis for integrated pharmacological, dietary and lifestyle modifications to prevent cardiovascular events and revascularisation procedures. The question arises as to whether these alterations in regional myocardial tone can be detected by any of the current non-invasive methods. Several methods are reviewed. We consider that intracoronary ultrasonography is the most accurate method, but non-invasive positron emission tomography and magnetic resonance imaging technology is of growing importance for identifying endothelial dysfunction of early coronary atherosclerosis.
Biomarkers↗
Modeling tissues contrast agent concentration: a solution to the tissue homogeneity model using a simulated arterial input function.
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Arteries↗
Measurement of the striatal dopamine transporter density and heterogeneity in type 1 alcoholics using human whole hemisphere autoradiography.
Dopaminergic mechanisms are involved in the positive reinforcing and addicting effects of alcohol. Positron emission tomography (PET) and single photon emission tomography (SPET) studies have indicated alterations in striatal dopamine transporters (DAT) and in presynaptic dopamine (DA) function in alcoholics, although also contradictory results have been reported. Normal variations in blood flow, metabolism, and receptor densities are apparently important to brain function. Such variations are known to decrease during pathophysiological processes, such as epilepsy, whereas normal receptor distributions are broadly heterogenous. We evaluated the densities and heterogeneities of striatal DAT in 8 adult-onset, Cloninger type I alcoholics and 10 controls using [125I]N-(3-iodoprop-2E-enyl)-2beta-carbomethoxy-3beta- (4'-methylphenyl)nortropane ([125I]PE2I) as a ligand for human postmortem whole hemisphere autoradiography, which provided high resolution images of the brain when compared with in vivo PET and SPET. The mean density and heterogeneity of DAT were markedly lower in the alcoholics. A significant linear correlation existed between DAT density and heterogeneity, as well as between DAT densities in the nucleus accumbens and in the dorsal striatum (caudate and putamen) in alcoholics, but not consistently in controls. The observed low DAT density and heterogeneity in the dorsal striatum suggest that type 1 alcoholics may have a dysfunctional DA system. These data indicate that human whole hemisphere autoradiography with the analysis of binding heterogeneity may be a relevant tool to measure pathological processes in the brain.
Alcoholism↗
Reduced serotonin transporter binding in binge eating women.
RATIONALE: There is evidence that abnormalities in brain dopamine, norepinephrine and serotonin metabolism may play an important role in binge eating. Serotonin-active antidepressant drugs have also been found to decrease binge eating. OBJECTIVE: We investigated serotonin transporter binding in obese binge-eating women. Eleven obese binge-eating and seven obese control women participated in the study. The subjects were not taking any medication known to affect serotonin (5-HT) transporters. METHODS: We used single-photon emission tomography (SPECT) with the radioligand 123I-labelled nor-beta-CIT, which specifically labels 5-HT transporters. RESULTS: Obese binge-eating women showed significantly decreased 5-HT transporter binding in the mid-brain compared with obese controls (2.1 +/- 0.5 versus 2.9 +/- 0.5, respectively). CONCLUSIONS: SPECT imaging with a ligand specific for 5-HT transporters can be used to assess altered serotonin transporter binding in the living human brain. The results tentatively suggest that 5-HT transporter binding is decreased in binge-eating women.
Adult↗
Effects of ageing on serotonin transporters in healthy females.
The effect of ageing on brain serotonin transporters was evaluated in 19 healthy female volunteers (age range 22-74 years) using single-photon emission tomography and [123I]nor-beta-CIT. The study subjects were scanned 0.3, 3, 6 and 23 h after injection of 185 MBq of [123I]nor-beta-CIT. The ratio of the distribution volume for tracer in the midbrain to that in the cerebellum minus 1 was used as an index for serotonin transporter binding. An age-related decline of 2% per decade (r=-0.47; P<0.05) was found in the midbrain. The decline in [123I]nor-beta-CIT binding in the serotonin transporter-rich area is much less than that in dopamine transporters in the striatum (6% per decade).
Adult↗
SPECT and neuropsychological performance in severe depression treated with ECT.
BACKGROUND: In severe depression, studies of regional cerebral blood flow (rCBF) by SPECT have not produced uniform results. The association between changes in SPECT and electroconvulsive therapy (ECT) has shown somewhat conflicting data. No data are available on benzodiazepine receptor function SPECT studies in ECT. METHODS: Twenty drug-resistant adult inpatients fulfilling the DSM-IIIR criteria for major depression were studied by SPECT (rCBF by relative ECD uptake in all, and benzodiazepine receptor function by iomazenil uptake in five subjects) before and 1 week after clinically successful bitemporal ECT. Clinical and neuropsychological test scores were used as references for the possible changes in SPECT. RESULTS: An increased perfusion after ECT was observed in right temporal and bilateral parietal cortices, whereas no reductions in relative ECD uptake were seen after ECT. Iomazenil-SPECT revealed a highly significant increase in the benzodiazepine receptor uptake in all studied cortical regions except temporal cortices. CONCLUSIONS: Clinically successful ECT was associated with changes in vascular perfusion and GABAergic neurotransmission, providing new evidence for the mechanism of action of ECT and for the neurobiology of severe drug-resistant depression.
Adult↗
Quality of dynamic radionuclide renal imaging: multicentre evaluation using a functional renal phantom.
The aim of this study was to evaluate the quality of dynamic radionuclide renal imaging in Finland. Nineteen nuclear medicine departments participated. A functional renal phantom was imaged and interpreted as a patient-like study. Reconstruction and printouts were performed according to the clinical routine of each laboratory. Three nuclear medicine specialists anonymously evaluated the quality of the image sets. The visual scores of the experts were ranked from one to five. In addition, several numerical time-activity parameters were calculated and compared between the laboratories. The average visual scores of the experts for the image sets were 3.2+/-0.5 (range 2.4-4.2). Only two laboratories received a score value of 4 or higher. The average error for the time to reach maximum activity (T(max)) ranged from -29 to +18% and for the washout time to reach half activity from maximum activity (T(1/2)) ranged from -43 to +66%. These results suggest that the difference in calculated parameters between laboratories is most probably due to variations in study protocols and analysis programmes. The need for external quality assurance and quality improvement in nuclear renal imaging is evident and is recommended for regular use.
Humans↗
Quantitation of neuroreceptors: a need for better SPECT imaging.
AIM: Existing methods to determine the binding potential in brain receptor and transporter studies with single-photon emission computed tomography (SPECT) show a marked dependence on the physical performance of the scanner and on the regions of interest (ROIs) drawn. We examined the influence of the physical performance on the binding potential. METHOD: The authors tested three gamma cameras (single-, dual- and triple-head) and two reconstruction techniques (conventional filtered back-projection and iterative reconstruction method) to determine the binding potential in brain receptor studies. Both human and organ-like phantom studies were performed. RESULTS: The binding potential was completely dependent on the imaging resolution, on the reconstruction technique used and on the ROIs drawn. The results of the phantom study revealed that the striatum-to-cerebellum ratio was only 37% of the actual one for the single-head, 63% for the dual-head and 72% for the triple-head gamma camera. CONCLUSION: The multiple head gamma camera with fan-beam collimators and iterative reconstruction with the attenuation based scatter correction is an imaging system of choice which introduces clinically more relevant images and is able to distinguish smaller differences in radioactivity at early stage of disease. However, for quantitative purposes the improvement without the use of the recovery coefficient is not great enough to restore the binding potentials to those of the true ones.
Brain↗
Specific binding and laterality of human extrastriatal dopamine D2/D3 receptors in late onset type 1 alcoholic patients.
Late onset type 1 alcoholism has been suggested to be associated with decreased dopaminergic transmission. Our hypothesis was that late onset type 1 alcoholics have also abnormal extrastriatal dopamine D(2)/D(3) receptor distribution. We performed binding, heterogeneity and laterality analysis of extrastriatal and striatal dopamine D(2)/D(3) receptors in nine late onset male alcoholics and in 12 age-matched healthy males. A radioligand, [(123)I]epidepride was used in high resolution single-photon emission tomography (SPET). Specific binding of epidepride in the left temporal pole was significantly (P<0.05) lower in type 1 alcoholics (0.74+/-0.14 ml/ml) than in controls (0.89+/-0.14 ml/ml). In alcoholics, there was no normal left-to-right asymmetry of the temporal cortical heterogeneity of epidepride distribution observed in control males (0.89+/-0.19 vs. 1.10+/-0.19; P<0.05). The results suggest that the specific binding of dopamine D(2)/D(3) receptors in late type 1 alcoholics is decreased and its laterality in the temporal brain is altered from normal.
Adult↗
Regional cerebral blood flow during exposure to food in obese binge eating women.
Cerebral responses elicited by the sight of food were evaluated in eight obese binge eating, 11 obese and 12 normal-weight non-binge eating women. Regional cerebral blood flow (rCBF) was mapped while the subjects were looking at a picture of a landscape (control) or at a portion of food (food exposure), and was measured by [99mTc]ethyl-cysteine-dimer and single photon emission computed tomography. Exposure to food was associated with different changes in the cerebral blood flow (normalized to mean cerebellar counts) of the right and left hemispheres in the obese binge eating than in the obese or normal-weight non-binge eating women. As compared with the non-binge eating groups, the obese binge eating women had, due to food exposure, a greater increase in the cerebral blood flow in the left than right hemisphere, especially in the frontal and pre-frontal regions. In addition, strong linear correlations were observed in this group between the rCBF of the left frontal and pre-frontal regions and the increase in the feeling of hunger during the exposure to food. Left hemisphere and its frontal and pre-frontal regions could thus play a role in binge eating behavior in humans.
Adult↗
Long-term effect of acetyl-L-carnitine on myocardial 123I-MIBG uptake in patients with diabetes.
Carnitine derivatives may have beneficial effects on cardiac and nerve function in patients with diabetes. The aim of this study was to investigate the effect of acetyl-L-carnitine (ALC) on myocardial sympathetic nervous function as measured with 123I-meta-iodobenzyl guanidine (MIBG) and single-photon emission tomography (SPET) in 19 patients with diabetes (placebo group, n = 6; ALC group, n = 13) at the beginning and at the end of a 1-year randomized, placebo-controlled, double-blind trial. The coefficient of variation for the MIBG analysis was 4%. In patients who were given a placebo, global myocardial MIBG uptake deteriorated during the study (MIBG uptake 1-year follow-up/baseline, 0.86 +/- 0.05, mean +/- standard error of mean), whereas in patients treated with ALC, MIBG uptake did not change significantly (1-year follow-up/baseline, 1.07 +/- 0.08; p = 0.03 between the groups). On the basis of these preliminary data, we conclude that long-term treatment with ALC may be of potential value in preventing the progressive loss of myocardial sympathetic nervous function in patients with diabetes. MIBG-SPET is a sensitive and thus valuable method in assessing the development of myocardial sympathetic nervous dysfunction.
3-Iodobenzylguanidine↗
Improvement of brain perfusion SPET using iterative reconstruction with scatter and non-uniform attenuation correction.
Filtered back-projection (FBP) is generally used as the reconstruction method for single-photon emission tomography although it produces noisy images with apparent streak artefacts. It is possible to improve the image quality by using an algorithm with iterative correction steps. The iterative reconstruction technique also has an additional benefit in that computation of attenuation correction can be included in the process. A commonly used iterative method, maximum-likelihood expectation maximisation (ML-EM), can be accelerated using ordered subsets (OS-EM). We have applied to the OS-EM algorithm a Bayesian one-step late correction method utilising median root prior (MRP). Methodological comparison was performed by means of measurements obtained with a brain perfusion phantom and using patient data. The aim of this work was to quantitate the accuracy of iterative reconstruction with scatter and non-uniform attenuation corrections and post-filtering in SPET brain perfusion imaging. SPET imaging was performed using a triple-head gamma camera with fan-beam collimators. Transmission and emission scans were acquired simultaneously. The brain phantom used was a high-resolution three-dimensional anthropomorphic JB003 phantom. Patient studies were performed in ten chronic pain syndrome patients. The images were reconstructed using conventional FBP and iterative OS-EM and MRP techniques including scatter and nonuniform attenuation corrections. Iterative reconstructions were individually post-filtered. The quantitative results obtained with the brain perfusion phantom were compared with the known actual contrast ratios. The calculated difference from the true values was largest with the FBP method; iteratively reconstructed images proved closer to the reality. Similar findings were obtained in the patient studies. The plain OS-EM method improved the contrast whereas in the case of the MRP technique the improvement in contrast was not so evident with post-filtering.
Brain↗
Metabolism of [123I]epidepride may affect brain dopamine D2 receptor imaging with single-photon emission tomography.
Iodine-123 labelled epidepride is a novel radiopharmaceutical for the study of cerebral dopamine D2 receptors using single-photon emission tomography (SPET). A lipophilic labelled metabolite of [123I]epidepride which may enter the brain and hamper the quantitation of receptors has been observed in human plasma. In the present study, gradient high-performance liquid chromatography (HPLC) was used to investigate the plasma concentration of the lipophilic labelled metabolite and its correlation to SPET imaging of striatal dopamine D2 receptors. A linear regression fit showed a negative correlation between the amount of the lipophilic labelled metabolite and the striatum to cerebellum ratio (n=16, R=-0.58, P<0.02), suggesting that plasma metabolite analysis is essential when imaging dopamine D2 receptors with SPET using [123I]epidepride.
Adult↗