technetium-tc-99m-exametazime and Nervous-System-Diseases

Recent and future evolutions in neuroSPECT apply to radiopharmaceuticals techniques and the synergistic use of different imaging modalities in the work-up of neurological disorders. The introduction of Technetium labelled perfusion tracers, which could pass the intact blood-brain barrier, together with the implementation of the tomographic principle, by making the conventional gamma camera rotating, enabled estimation of regional cerebral blood flow and indirectly of local brain metabolism. In addition at present Thallium-201 and Tc-99m sestaMIBI allow functional detection of viable tumor tissue, without interference from previous surgery or radiotherapy as seen using CT-scan or MRI. In neurology this has led to the recognition of SPECT by the American Academy of Neurology (Therapeutics and technology subcommittee) as an established or promising tool in major neurological disorders such as dementia, stroke and epilepsy, while other domains such as brain oncology are considered investigational. With regard to radiopharmaceuticals, recent evolutions mainly include the development of mostly Iodine-123 labelled receptor ligands, some of which are already commercially available. For instrumentation advances consist e.g. of multidetector systems equipped with fanbeam collimators, attenuation and scatter correction or coincidence detection. Given the present role for nuclear neurology it may be expected that these additional radiopharmaceutical and technical innovations will continue to stimulate the development of SPECT of the brain. The synergistic use of several imaging techniques such as CT, (functional) MRI, source imaging, SPECT and PET represents a multimodal holistic approach to probe cerebral functions for research and clinical purposes. Clinical indications, in which this synergistic use is illustrated include e.g. support of the clinical diagnosis of dementia of the Alzheimer type, presurgical ictal detection of seizure focus, detection of acute ischemia and differential diagnosis between radiation necrosis and brain tumor recurrence. The synergistic use of imaging modalities, optimally applied using image fusion, allows to overcome the intrinsic limitations and to enhance the specific advantages of the different approaches as it leads to increased precision and accuracy, as well for spatial anatomofunctional correlation as for quantification.

Topics: Alzheimer Disease; Brain Ischemia; Brain Neoplasms; Epilepsy; Humans; Image Processing, Computer-Assisted; Magnetic Resonance Imaging; Mental Disorders; Nervous System Diseases; Neurology; Nitriles; Technetium Tc 99m Exametazime; Tomography, Emission-Computed; Tomography, Emission-Computed, Single-Photon; Tomography, X-Ray Computed

Previous studies have shown that zolpidem (CAS 82626-48-0) can lead to improved perfusion in damaged brain tissue. Zolpidem belongs to the imidazopyridine chemical class and it illicits its pharmacological action via the gamma-aminobutyric acid (GABA) receptor system through stimulation of particularly the omega 1 receptors and to a lesser extent omega 2 receptors. Previously it was reported that no cerebral blood flow effects were observed in normal baboons after treatment with zolpidem, whereas an asymmetric regional increase in cerebral blood flow was observed in a neurologically abnormal baboon. In this study, the effect of a combination of the benzodiazepine receptor antagonist flumazenil (CAS 78755-81-4) and zolpidem on brain perfusion was examined by the 99mTc-hexamethyl-propylene amine oxime (99mTc-HMPAO) split dose brain single photon emission computed tomography (SPECT). Four normal baboons and the neurologically abnormal baboon from the previous zolpidem study were examined. In the current study the asymmetric changes observed after zolpidem--only treatment in the abnormal baboon was attenuated by flumazenil intervention. A decreased brain blood flow was observed after combination treatment of zolpidem and flumazenil in the normal baboons. The involvement of the omega receptors is suggested by these results. Up- or down-regulation of omega receptors may also contribute to the observed responses in the abnormal baboon and a brain injured patient.

Topics: Algorithms; Animals; Brain; Cerebrovascular Circulation; Flumazenil; GABA Modulators; Hypnotics and Sedatives; Male; Nervous System Diseases; Papio; Pyridines; Radionuclide Imaging; Radiopharmaceuticals; Technetium Tc 99m Exametazime; Zolpidem

Topics: Acetazolamide; Carbonic Anhydrase Inhibitors; Cerebrovascular Circulation; Humans; Infant; Male; Nervous System Diseases; Radiopharmaceuticals; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

The diagnosis of central nervous system (CNS) involvement appears to be a major problem in systemic lupus erythematosus (SLE), especially when the clinical signs are non-specific or neuroimaging is unremarkable. Two SLE patients with mild neuropsychiatric manifestations were studied with magnetic resonance imaging (MRI), single photon emission tomography (SPET) and localized proton magnetic resonance spectroscopy (H-1 MRS). MRI was normal in both patients. SPET revealed areas of hypoperfusion in both patients. H-1 MRS demonstrated metabolic abnormalities in the regions corresponding to the hypoperfused areas. A correlation between H-1 MRS and SPET was noted: patients with mild neuropsychiatric SLE may have disturbances evident on SPET and H-1 MRS in the presence of normal anatomy on MRI, suggesting that CNS involvement in SLE has very strong physiological and neurometabolic components in individual patients.

Topics: Adult; Brain; Female; Humans; Lupus Erythematosus, Systemic; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Mental Disorders; Middle Aged; Nervous System Diseases; Organotechnetium Compounds; Oximes; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

We evaluated regional cerebral blood flow with technetium 99mTc hexamethylpropyleneamineoxime single photon emission computed tomography (SPECT) in 20 children and adolescents with neurologic dysfunction of varied etiology and abnormal electroencephalograms (EEGs). All patients were also examined with computed tomography (CT) and magnetic resonance imaging (MRI). Abnormal perfusion was found in 17 (85%) of 20 SPECT scans. Abnormal CT or MRI scans were noted in nine (45%) and in 10 (50%) of 20 cases, respectively. In eight (73%) of 11 cases with normal CT scans and in seven (70%) of 10 with normal MRI scans, the SPECT scan was abnormal. Abnormal regional cerebral blood flow on SPECT scans correlated better with EEG abnormalities than with neurologic examination or CT or MRI scan findings. We conclude that in children and adolescents with a spectrum of neurologic diseases and abnormal EEGs, abnormalities of brain structure or function are more likely to be documented by SPECT than by CT or MRI scans. SPECT findings correlate well with the location and type of EEG abnormality.

Topics: Adolescent; Adult; Brain Diseases; Cerebrovascular Circulation; Child; Child, Preschool; Electroencephalography; Female; Humans; Infant; Intellectual Disability; Magnetic Resonance Imaging; Male; Nervous System Diseases; Organotechnetium Compounds; Oximes; Sensitivity and Specificity; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon; Tomography, X-Ray Computed

The uptake and retention in a 2 cm thick brain section was recorded serially by SPECT after i.v. injection of [99mTc]-d,l-HM-PAO (HM-PAO). In 16 patients, the fraction of the administered dose retained by the brain was 5.2 +/- 1%, showing a peak after 40-50s, then decreasing by 10% within the first 10 min and then by only 0.4% per hour. The image contrast was measured in each patient as the regional hemispheric asymmetry difference in percent of the highest value of the two regions. It decreased from 31% at 30-40 s to 25% at 10 min. At 24 h, a value of 19% was reached. Using the images obtained at 10 min after injection, a region to region comparison of the original and corrected HM-PAO images to the xenon-133 regional cerebral blood flow (rCBF) images was performed. Forty-four patients with stroke, epilepsy, dementia, basal ganglia disease, and tumors and control subjects were included in this comparison. The algorithm proposed by Lassen et al. was used to correct the original images for back diffusion of tracer (brain to blood); a good correlation very close to the line of identity between the corrected HM-PAO and xenon-133 data was obtained when using a conversion/clearance ratio of 1.5 and when the noninvolved hemisphere was used as a reference region (r = 0.86, p less than 0.0001). Serial arterial and cerebral venous blood sampling was performed over 10 min following i.v. injection of HM-PAO in six patients. An overall brain retention fraction of 0.37 +/- 0.03 (mean +/- SEM) was calculated from the data. An average CBF of 0.62 +/- 0.12 ml/g/min was determined on the basis of the Fick principle; this compared to a value of 0.59 +/- 0.09 ml/g/min (mean +/- SEM) measured by the xenon-133 inhalation method. The two sets of CBF values correlated linearly with a correlation coefficient of 0.97 (p less than 0.01). Inserting the average CBF value for the hemisphere as measured by the Fick principle into the algorithm described by Lassen et al. yields absolute rCBF values (ml/g/min) directly from the corrected HM-PAO images.(ABSTRACT TRUNCATED AT 400 WORDS)

Topics: Adolescent; Adult; Aged; Brain; Cerebrovascular Circulation; Female; Humans; Male; Middle Aged; Nervous System Diseases; Organometallic Compounds; Oximes; Technetium; Technetium Tc 99m Exametazime; Tomography, Emission-Computed; Xenon Radioisotopes