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Biomedical subjects

D C Costa

Publications and source records attributed to D C Costa.

At least 127 records · Page 7Linked to original sources
PubMed1991

Diagnosis of brain death with technetium 99m hexamethylpropylene amine oxime.

We report on the utility of technetium 99m hexamethylpropylene amine oxime (99mTc-HMPAO) to diagnose brain death following cardiac surgery on a 49-year-old man with triple-vessel coronary artery disease. The imaging parameters and criteria to diagnose irreversible brain damage (brain death) with 99mTc-HMPAO are outlined. Brain imaging with this tracer seems to be more reliable than classic radionuclide angiography and has a potential value to confirm the diagnosis of brain death at an early stage. In addition, it may be used to evaluate the perfusion pattern to other vital organs with potential for transplantation.

Brain Death↗
PubMed1991

The use of cerebral activation procedures with single photon emission tomography.

Single photon emission tomography allows the imaging of dynamic brain functioning. The use of cerebral activating procedures within the scan protocol enables investigation of the mechanisms involved in specific brain functions in health and disease. Activation studies involve the comparison of at least two data sets describing brain activity generated in conditions that differ for the specific function in question. When designing an activation study, decisions regarding methodology include: the nature of the activation regime, the tracer-ligand utilized, the SPET instrument and the manner of subsequent data analysis. These issues are discussed in this review, both theoretically and with reference to published studies. Means of activating particular cerebral structures and functions are reviewed, as are the limitations of the techniques with respect to temporal and spatial resolution and the potentially confounding nature of preconceived ideas regarding the mechanisms of brain function.

Brain↗
PubMed1991

Endocardial monophasic action potential recordings for the detection of myocardial ischemia in man: a study using atrial pacing stress and myocardial perfusion scintigraphy.

In a study designed to appraise the use of monophasic action potentials (MAPs) to detect myocardial ischemia in endocardial recordings, changes in steady-state MAP duration were compared in recordings between normal and ischemic areas of myocardium identified by the use of a radionuclide tracer simultaneously with the MAP recording procedure. Single-site recordings were made from the left or right ventricular endocardium or both in 26 patients (32 recording sites) during atrial pacing up to angina threshold. Pacing was maintained for 2 minutes at each increment in heart rate and MAPs were recorded at the end of each 2-minute period. Perfusion defects produced by atrial pacing stress were detected using technetium-99m hexakis-2-methoxy-2-methylpropyl-isonitrile injected at peak pacing stress. In 18 recordings from normally perfused areas of endocardium, MAP duration at 70% and 90% repolarization shortened by a mean (+/- SD) of 20.9 (3.7) msec and 22.0 (4.8 msec, respectively, for every 100 msec change in cycle length. This is in keeping with the effect of cycle length changes on the action potential duration. The extent of shortening was significantly greater (p less than 0.01) for 14 recordings from ischemic areas, being 32.0 (8.6) and 33.8 (9.7) msec, respectively, indicating the additional effect of localized myocardial ischemia. These results validate the applicability of the endocardially recorded MAPs for the detection of ischemia. Such methodology may provide a means of assessing therapeutic interventions aimed at the early phase of ischemia.

Action Potentials↗
PubMed1991

99TCm-HMPAO SPECT studies in traumatic intracerebral haematoma.

Traumatic intracerebral haematomas are a common neurosurgical emergency. Their management, particularly the role of surgical removal, is controversial. Deterioration often occurs late, and is unpredictable. Eight patients with traumatic intracerebral haematomas were admitted to the neurosurgical unit to monitor their clinical state. All were studied within 48 hours of admission with single photon emission computerised tomography (SPECT), using the recently introduced radionuclide 99Technetiumm-Hexamethyl propylene amine oxime (99Tcm-HMPAO). At the time of the SPECT study, all the patients had been clinically stable. Three patients remained so; in the other five, the conscious level deteriorated, necessitating craniotomy and evacuation of the haematoma. In all the patients, the SPECT studies demonstrated perfusion defects that corresponded to the location of the haematoma, as demonstrated by computerised tomography (CT). However, in the five patients who subsequently deteriorated, the perfusion defects seen on the SPECT scan appeared larger than the haematoma, as seen on the CT scan. In addition, there was widespread poor retention of 99Tcm-HMPAO in the ipsilateral hemisphere. These differences were quantifiable. Interestingly, these differences were present at a time when the patients were clinically stable, before their deterioration. It is concluded that SPECT studies with 99Tcm-HMPAO are of possible use as predictors of late deterioration in the management of traumatic intracerebral haematomas.

Adolescent↗
PubMed1990

In vivo characterisation of 3-iodo-6-methoxybenzamide 123I in humans.

3-Iodo-6-methoxybenzamide (123I-IBZM), a new Dopamine D2 receptor ligand, was used in conjunction with SME 810 brain tomography to study six subjects (one normal volunteer, four schizophrenics and one DAT patient). Initial Dynamic SPET was followed by multislice SPET. High-resolution images of the D2 receptor distribution in the basal ganglia were obtained. The specific binding in D2 receptors of the basal ganglia is highest from 2-4 h p.i. Patients on anti-psychotic drugs showed significantly lower specific binding. Dopamine D2 brain receptor availability in man may now be studied with SPET. Continuous data acquisition with single slice tomography is particularly important in the study of this type of radiotracers.

Adult↗
PubMed1989

Intracellular localization of 99Tcm-d,l-HMPAO and 201Tl-DDC in rat brain.

The intracellular localization and relative distribution of 99Tcm-hexamethylpropyleneamine-oxime (99Tcm-d, l-HMPAO) and 201Tl-diethyldithiocarbamate (201Tl-DDC), which have been used to assess regional cerebral blood flow (rCBF) in man, were investigated in rat brain. 99Tcm-d, l-HMPAO was found attached mainly to cell organelles whilst 201Tl-DDC was localized mainly in free state in the cytosolic fraction. Isolation of neuronal and glial nuclei showed that there is higher uptake of 99Tcm-d, l-HMPAO in neuronal nuclei than in glial nuclei for all the different regions of the rat brain investigated. These data demonstrate a different subcellular localization of the two lipophilic agents studied. In view of their proposed clinical utility, this difference merits further investigation.

Animals↗
PubMed1989

99Tcm-HMPAO SPET and cerebral blood flow: a study of CO2 reactivity.

Single photon emission tomography (SPET) studies using 99Tcm-HMPAO are in widespread use in the functional imaging of cerebral blood flow (CBF). While qualitatively the images correlate well with other imaging modalities, there are doubts as to the quantitative accuracy of this method. In particular, the uptake and subsequent retention of 99Tcm-HMPAO in conditions of high flow is known to be nonlinear. In this study, we compared the quantitative retention of 99Tcm-HMPAO in eight subjects under conditions of normo- and hypercapnia. There was no significant increase, despite a mean rise of the end tidal pCO2 from 5.06 to 7.06 kPa, a stimulus that is known to provoke an 80-100% rise in CBF. We conclude that SPET studies with 99Tcm-HMPAO provide excellent qualitative images of the distribution of CBF, but that quantitative data in ml hg-1 min-1 must be interpreted with caution.

Adult↗
PubMed1989

The investigation of Alzheimer's disease with single photon emission tomography.

Twenty patients satisfying standard clinical criteria for Alzheimer's disease (AD) and six age-matched normal controls were studied using 99mTc hexamethyl-propyleneamine oxime and single photon emission tomography. The AD patients had lower regional cerebral blood flow (rCBF) in the temporal and posterior parietal lobes compared to controls. AD patients with apraxia and aphasia had lower rCBF in the lateral temporal and posterior parietal lobes than AD patients without these features. Within the AD group, correlations were found between neuropsychological tests and rCBF: praxis correlated with posterior parietal activity, memory with left temporal lobe activity and language with activity throughout the left hemisphere.

Aged↗
PubMed1988

CBF tomograms with [99mTc-HM-PAO in patients with dementia (Alzheimer type and HIV) and Parkinson's disease--initial results.

We present preliminary data on the utility of functional brain imaging with [99mTc]-d,l-HM-PAO and single photon emission computed tomography (SPECT) in the study of patients with dementia of the Alzheimer type (DAT), HIV-related dementia syndrome, and the "on-off" syndrome of Parkinson's disease. In comparison with a group of age-matched controls, the DAT patients revealed distinctive bilateral temporal and posterior parietal deficits, which correlate with detailed psychometric evaluation. Patients with amnesia as the main symptom (group A) showed bilateral mesial temporal lobe perfusion deficits (p less than 0.02). More severely affected patients (group B) with significant apraxia, aphasia, or agnosia exhibited patterns compatible with bilateral reduced perfusion in the posterior parietal cortex, as well as reduced perfusion to both temporal lobes, different from the patients of the control group (p less than 0.05). SPECT studies of HIV patients with no evidence of intracraneal space occupying pathology showed marked perfusion deficits. Patients with Parkinson's disease and the "on-off" syndrome studied during an "on" phase (under levodopa therapy) and on another occasion after withdrawal of levodopa ("off") demonstrated a significant change in the uptake of [99mTc]-d,l-HM-PAO in the caudate nucleus (lower on "off") and thalamus (higher on "off"). These findings justify the present interest in the functional evaluation of the brain of patients with dementia. [99mTc]-d,l-HM-PAO and regional cerebral blood flow (rCBF)/SPECT appear useful and highlight individual disorders of flow in a variety of neuropsychiatric conditions.

Acquired Immunodeficiency Syndrome↗
PubMed1988

White cells radiolabelled with 111In and 99Tcm--a study of relative sensitivity and in vivo viability.

In this study a comparison between the classical (111In oxine) and the newer (99Tcm HMPAO) technique of labelling leucocytes is reported. The behaviour in vivo and the relative sensitivity in the detection of infection (chest and bone) and inflammatory bowel disease (IBD) is presented. Simultaneous dual-radionuclide gamma camera acquisition methodology was applied to study 99 patients, 18 with chest infection, 26 with bone infection, 41 with IBD and 14 with other pathological conditions. The mean (1 SD) 50% washout time from the lungs was 483.03 (79.10) s for 99Tcm HMPAO-labelled white blood cells and 475.85 (83.79) s for 111In oxine-labelled white cells (r = 0.81). Concordance between the two techniques was 94% in the chest-infection group of patients, 88% in the bone-infection group and 71% in the localization of IBD.

Adolescent↗