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Biomedical subjects

P A Carvalho

Publications and source records attributed to P A Carvalho.

At least 19 recordsLinked to original sources
PubMed1998

Dual-isotope single-photon emission computerized tomography scanning in patients with glioblastoma multiforme: association with patient survival and histopathological characteristics of tumor after high-dose radiotherapy.

OBJECT: The study was conducted to determine the association between dual-isotope single-photon emission computerized tomography (SPECT) scanning and histopathological findings of tumor recurrence and survival in patients treated with high-dose radiotherapy for glioblastoma multiforme. METHODS: Studies in which SPECT with 201Tl and 99mTc-hexamethypropyleneamine oxime (HMPAO) were used were performed 1 day before reoperation in 47 patients with glioblastoma multiforme who had previously been treated by surgery and high-dose radiotherapy. Maximum uptake of 201Tl in the lesion was expressed as a ratio to that in the contralateral scalp, and uptake of 99mTc-HMPAO was expressed as a ratio to that in the cerebellar cortex. Patients were stratified into groups based on the maximum radioisotope uptake values in their tumor beds. The significance of differences in patient gender, histological characteristics of tissue at reoperation, and SPECT uptake group with respect to 1-year survival was elucidated by using the chi-square statistic. Comparisons of patient ages and time to tumor recurrence as functions of 1-year survival were made using the t-test. Survival data at 1 year were presented according to the Kaplan-Meier method, and the significance of potential differences was evaluated using the log-rank method. The effects of different variables (tumor type, time to recurrence, and SPECT grouping) on long-term survival were evaluated using Cox proportional models that controlled for age and gender. All patients in Group I (201Tl ratio < 2 and 99mTc-HMPAO ratio < 0.5) showed radiation changes in their biopsy specimens: they had an 83.3% 1-year survival rate. Group II patients (201Tl ratio < 2 and 99mTc-HMPAO ratio of > or = 0.5 or 201Tl ratio between 2 and 3.5 regardless of 99mTc-HMPAO ratio) had predominantly infiltrating tumor (66.6%); they had a 29.2% 1-year survival rate. Almost all of the patients in Group III (201Tl ratio > 3.5 and 99mTc-HMPAO ratio > or = 0.5) had solid tumor (88.2%) and they had a 6.7% 1-year survival rate. Histological data were associated with 1-year survival (p < 0.01): however, SPECT grouping was more closely associated with 1-year survival (p < 0.001) and was the only variable significantly associated with long-term survival (p < 0.005). CONCLUSIONS: Dual-isotope SPECT data correlate with histopathological findings made at reoperation and with survival in patients with malignant gliomas after surgical and high-dose radiation therapy.

Adolescent↗
PubMed1996

Intratumoral administration of 5-[123I]iodo-2'-deoxyuridine in a patient with a brain tumor.

UNLABELLED: We have initiated a study in which patients suspected of having primary gliomas are given a single intracerebral injection of the thymidine analog 5-[123I]iodo-2'-deoxyuridine ([123I]IUdR). The purpose of the study is to determine the biodistribution of the radiopharmaceutical and to calculate dose estimates to the tumor and normal tissues. METHODS: A patient with a cystic glioma was injected with [123I]IUdR. Whole-body scans and brain scans were obtained at various times after injection, and blood, urine and stools were collected and assayed for radioactivity to assess its biodistribution and clearance. RESULTS: Scintigraphic imaging demonstrated that the distribution of radiolabeled IUdR was mainly confined to the tumor (injection site), stomach and bladder. Disappearance from the tumor site and blood clearance were delayed probably due to collection in the cystic lesion. Eighty percent of the injected dose was recovered in the urine. CONCLUSION: The pharmacokinetics of [123I]IUdR locoregionally administered to a human glioma in situ resembled those observed in a rat glioma model where administration of the radiopharmaceutical radiolabeled with the Auger electron emitter 125I was therapeutically effective.

Adult↗
PubMed1993

Thallium-201 technetium-99m HMPAO single-photon emission computed tomography (SPECT) imaging for guiding stereotactic craniotomies in heavily irradiated malignant glioma patients.

SPECT scanning with Tl-201 and Tc-99m offers a unique, inexpensive functional imaging modality to combine with CT stereotactic craniotomy for guiding resection of necrosis and/or tumour in patients treated with escalated doses of radiation (> 6000 cGy) by either brachytherapy or radiosurgery. Thirty-two cases were analyzed, with a detailed description of the imaging and operative techniques.

Astrocytoma↗
PubMed1993

Tc-99m HMPAO brain perfusion SPECT in acute aphasia. Correlation with clinical and structural findings.

Tc-99m hexamethylpropylene amineoxime (HMPAO) brain perfusion SPECT was correlated with CT, MRI, and clinical findings in 17 patients with acute and subacute aphasia to determine its diagnostic potential in the early phases of stroke-associated language dysfunction. SPECT was performed using a dedicated brain imaging system after intravenous injection of 20 mCi (740 MBq) of Tc-99m HMPAO. Transaxial and three-dimensional surface rendered images were evaluated visually, and perfusion defects were correlated with CT, MRI, and a standard battery of clinical tests for aphasia. Clinical examination was insufficient for anatomic localization of aphasia in more than 40% of patients. CT exams were normal in 5 patients, although SPECT demonstrated perfusion defects in all 17. Nonfluent aphasia was present in only 6 of 10 patients with perfusion defects in Broca's area and fluent aphasia was present in only 5 of 10 patients with lesions in Wernicke's area. Auditory comprehension defect was associated with perfusion defects in the inferior parietal region in 9 of 12 patients (P = 0.05); reading and writing abnormalities were associated with perfusion defects in the posterior frontal, superior and inferior parietal cortex, and superior temporal gyri, and repetition deficit was associated with defects involving the inferior parietal cortex, the supramarginal and angular gyri, and the ipsilateral thalamus in 8 of 11 patients (P < 0.05). Brain perfusion SPECT should be included in the initial evaluation of aphasic patients, because clinical tests of aphasia and morphological imaging have limited value for accurately determining the extent and location of functional deficits.

Acute Disease↗
PubMed1992

Detection of recurrent gliomas with quantitative thallium-201/technetium-99m HMPAO single-photon emission computerized tomography.

Deteriorating clinical status after high-dose radiation therapy for high-grade gliomas may be due to radiation changes or may signal recurrent or residual tumor mass. The two conditions cannot be distinguished reliably by computerized tomography (CT) or magnetic resonance (MR) imaging. The authors assessed the ability of sequential thallium-201 chloride (201Tl) and technetium-99m hexamethylpropylene amine oxime (99mTc HMPAO) single-photon emission CT (SPECT) to distinguish tumor recurrence from radiation changes after high-dose (greater than or equal to 600 cGy) radiation therapy for malignant gliomas. Preoperative tumor/nontumor uptake ratios were analyzed in 32 patients and correlated with the presence of gross tumor at the time of reoperation. In 12 of 13 patients with 201Tl tumor/scalp ratios of 3.5 or greater, recurrent tumor was present. The authors found 99mTc HMPAO SPECT to be useful for identifying the absence of solid tumor recurrence in patients with low to moderate 201Tl uptake (ratio 1.1 to 3.4) and low perfusion to that site. In 11 of 12 patients with 99mTc HMPAO tumor/cerebellum ratios of 0.50 or less, no recurrent tumor mass was present. Three of seven patients with 201Tl ratios of 3.4 or less and 99mTc HMPAO ratios of 0.51 or more had recurrent tumor found at surgery; thus the test was not predictive in this group. It is concluded that the use of sequential 201Tl and 99mTc HMPAO SPECT accurately identifies the presence of tumor recurrence versus radiation changes in most patients with high-grade astrocytomas who have undergone tumor resection and high-dose radiation therapy.

Adult↗
PubMed1992

Subcellular distribution and analysis of technetium-99m-MIBI in isolated perfused rat hearts.

To address the apparent discrepancy between cultured cells and whole heart preparations, Langendorff-perfused rat hearts loaded with hexakis (2-methoxyisobutyl isonitrile) technetium (I) (99mTc-MIBI) were fractionated by a standard differential centrifugation method and fractional contents of 99mTc-MIBI were correlated with the mitochondrial marker, malate dehydrogenase (MDH), and mitochondrial substrates. The "cytosolic" fraction nominally contained 89% +/- 3% of total 99mTc-MIBI, but also contained 91% +/- 1% of total MDH activity by this method. Chromatographic analysis of activity in the "cytosolic" fraction demonstrated greater than 95% of the agent was present as the original free cationic complex; binding to a small molecular weight cytosolic protein was not involved in localization. Addition of the mitochondrial uncoupler CCCP (5 microM) to both "mitochondrial" and "cell fragment" pellets released up to 84% +/- 8% of 99mTc-MIBI content and addition of the mitochondrial substrate succinate (10 microM) in the presence of rotenone (1 microM) enhanced 99mTc-MIBI content by up to 139% +/- 52% over the control. These correlative data from rat hearts indicate that approximately 90% of 99mTc-MIBI activity in vivo is associated with mitochondria in an energy-dependent manner as a free cationic complex, but migrates during fractionation/centrifugation.

Animals↗
PubMed1992

The scintigraphic appearance of Alzheimer's disease: a prospective study using technetium-99m-HMPAO SPECT.

Alzheimer's disease produces regional abnormalities in brain blood flow and metabolism that may result in recognizable scintigraphic patterns. We determined the predictive value of 99mTc-HMPAO SPECT for the presence of Alzheimer's disease based on a prospective study of 132 consecutive patients coming to our nuclear medicine clinical unit for evaluation of their memory loss or cognitive abnormalities. During clinical follow-up averaging 10.1 mo, a final diagnosis was established in 113 patients, 52 of which had Alzheimer's disease. The probability of Alzheimer's disease was determined for seven scintigraphic patterns. The probability was 19% that patients with memory loss and normal perfusion had Alzheimer's disease. For abnormal perfusion patterns, the probability of Alzheimer's disease was 82% with bilateral temporoparietal defects, 77% with bilateral temporoparietal defects with additional defects, 57% with unilateral temporoparietal defects, 43% with frontal defects only, 18% with other large defects and 0% with multiple small cortical defects. We conclude that for 99mTc-HMPAO SPECT the predictive value of bilateral temporoparietal defects for Alzheimer's disease is high, while the perfusion patterns of unilateral temporoparietal perfusion defects and frontal defects only, which occur in 20% of patients with Alzheimer's disease, are not predictive of that disease.

AIDS Dementia Complex↗
PubMed1991

Frontal lobe dysfunction following infarction of the left-sided medial thalamus.

We treated a 62-year-old woman who developed a dramatic change in personality and behavior following a discrete left-sided medial thalamic infarction involving the dorsomedial nucleus. Neuropsychological testing demonstrated severe impairment of complex executive behaviors that are usually associated with frontal lobe function. Electroencephalography and single-photon emission computed tomography strongly implicated dysfunction of the ipsilateral frontal lobe. This case further supports a functional and physiologic thalamofrontal linkage as part of a broader cerebral network modulating complex human behavior.

Brain Diseases↗
PubMed1991

Tc-99m MIBI SPECT in the assessment of myocardial reperfusion after percutaneous transluminal coronary angioplasty.

Tc-99m MIBI SPECT was used to assess the early benefits of successful percutaneous transluminal coronary angioplasty (PTCA) in nine consecutive patients. SPECT stress studies were done by artificial cardiac pacing just prior to PTCA and 16-20 hours later, with perfusion images obtained 2-3 hours after pacing stress and Tc-99m MIBI injection. Angiographic restenosis was demonstrated in three patients at a later date, and all of these showed no significant improvement on the perfusion study after PTCA. All four patients asymptomatic at 7 months following PTCA had an average 15% improvement in segmental perfusion after the procedure. In two patients symptomatic after PTCA, one showed angiographic patency and had greater than 15% improvement in perfusion, while the second showed no scintigraphic improvement (no angiographic data obtained). This preliminary study suggests that Tc-99m MIBI is an important adjunct to angiography in estimating the amount of myocardium "at risk" before and after PTCA.

Aged↗
PubMed1991

Extracranial metastatic glioblastoma: appearance on thallium-201-chloride/technetium-99m-HMPAO SPECT images.

Sequential thallium-201-chloride and technetium-99m-hexamethylpropyleneamine oxime single-photon emission computed tomography (SPECT) images were obtained in a patient with extracranial metastatic glioblastoma multiforme. Thallium-201 uptake was high (three times the scalp background) in all pathologically confirmed extracranial metastases and moderate (1.6 times scalp background) intracranially, where most biopsy specimens showed gliosis with scattered atypical astrocytes. Technetium-99m-HMPAO uptake was decreased intracranially in the right frontal and parietal lobes which had been irradiated. It was also decreased in one well-encapsulated scalp lesion and high in another scalp mass with less defined borders. Possible mechanisms of tumor uptake of these agents are reviewed.

Adult↗
PubMed1991

Computer-assisted superimposition of magnetic resonance and high-resolution technetium-99m-HMPAO and thallium-201 SPECT images of the brain.

A method for registering three-dimensional CT, MR, and PET data sets that require no special patient immobilization or other precise positioning measures was adapted to high-resolution SPECT and MRI and was applied in 14 subjects (five normal volunteers, four patients with dementia (Alzheimer's disease), two patients with recurrent glioblastoma, and three patients with focal lesions (stroke, arachnoid cyst and head trauma]. T2-weighted axial magnetic resonance images and transaxial 99mTc-HMPAO and 201Tl images acquired with an annular gamma camera were merged using an objective registration (translation, rotation and rescaling) program. In the normal subjects and patients with dementia and focal lesions, focal areas of high uptake corresponded to gray matter structures. Focal lesions observed on MRI corresponded to perfusion defects on SPECT. In the patients who had undergone surgical resection of glioblastoma followed by interstitial brachytherapy, increased 201Tl corresponding to recurrent tumor could be localized from the superimposed images. The method was evaluated by measuring the residuals in all subjects and translational errors due to superimposition of deep structures in the 12 subjects with normal thalamic anatomy and 99mTc-HMPAO uptake. This method for superimposing magnetic resonance and high-resolution SPECT images of the brain is a useful technique for correlating regional function with brain anatomy.

Alzheimer Disease↗
PubMed1991

Brain perfusion is abnormal in cocaine-dependent polydrug users: a study using technetium-99m-HMPAO and ASPECT.

Cocaine abuse is widespread and has been associated with serious neurovascular complications. We studied a group of cocaine-dependent polydrug users with 99mTc-HMPAO and high-resolution SPECT and compared their perfusion pattern to cerebral perfusion in a group of older control subjects. Sixteen of 18 cocaine-dependent polydrug users had abnormal perfusion characterized primarily as small focal defects involving inferoparietal, temporal, and anterofrontal cortex and basal ganglia. Psychometric testing was abnormal in all 18 cocaine-dependent subjects. No relation was found between the severity of SPECT abnormalities and mode of administration or frequency or length of cocaine use. All 15 older normal subjects had normal cerebral perfusion. While the focal perfusion abnormalities to the cortex and basal ganglia could be explained by the profound vasoconstrictor effects of cocaine, the combinational use of multiple substances including cannabis and alcohol may play a contributory role. This study documents the high incidence of functional brain abnormalities in cocaine-dependent chronic polydrug users without corresponding abnormalities on imaging studies of cerebral anatomy and morphology.

Adult↗
PubMed1990

Myocardial clearance of Tc-99m hexakis-2-methoxy-2-methylpropyl isonitrile (MIBI) in patients with coronary artery disease.

Myocardial clearance of the new cationic, lypophilic myocardial perfusion agent, Tc-99m-hexakis-2-methoxy-2-methylpropyl isonitrile (MIBI) was studied in nine patients with coronary artery disease. Regional time-activity curves were determined from serial postexercise myocardial SPECT images after a single dose of Tc-99m MIBI. There were significant differences between the clearance rates from normal and ischemic myocardium. Tc-99m MIBI washout from normal myocardium was 27 +/- 8% by 6 hours after injection. Clearance from mild myocardial defects (initial activity greater than 60% of the activity in normal myocardium) was 16% by 6 hours in six patients. No washout was detected by 6 hours in the three patients with severe myocardial defects. The ratio between the activity in ischemic and normal myocardium increased from 0.70 +/- 0.08 to 0.80 +/- 0.13 and 0.84 +/- 0.13 at 4 and 6 hours after injection in the patients with mild defects. In the patients with large defects, the ratio increased from 0.42 +/- 0.09 to 0.54 +/- 0.07 at 6 hours. It is concluded that, while redistribution is substantially slower than with Tl-201, image interpretation and data evaluation should be approached cautiously when imaging is delayed 4 hours or more after injection of Tc-99m MIBI. Quantitative techniques aimed at evaluating the extent and intensity of myocardial ischemia will be particularly affected.

Aged↗
PubMed1990

Evaluation of in vitro released Wuchereria bancrofti third stage larval antigens for detection of Bancroftian filariasis.

Three types of in vitro released excretory, secretory and metabolic antigens of Wuchereria bancrofti third larval stage (L3ESM) are evaluated in ELISA test to detect infected individuals in the endemic area. A total of 104 reference sera are used to predict the sensitivity of these antigens. None of L3 ESM antigens, although homologous in nature, did not identify correctly the categorised reference sera. This study clearly indicated a need for defined antigens to detect W. bancrofti infection early in the endemic residents.

Animals↗
PubMed1990

Differential recognition of Brugia malayi antigens by bancroftian filariasis sera.

Individuals residing in an area endemic to Wuchereria bancrofti infection were broadly categorised as endemic normals (EN), microfilaraemics (mf + ve) and elephantoids i.e., chronic lymphatic filariasis (EL). The immune status of these three groups was examined in terms of (i) specific antibody levels; (ii) ability to induce antibody dependent cellular cytotoxicity (ADCC) to microfilariae; and (iii) ability to recognise different microfilarial antigens by immunoblotting. All three groups of endemic residents were indistinguishable in their antibody levels as measured by ELISA with B. malayi microfilarial antigen. Many endemic normal sera and most elephantoid sera exerted strong cytotoxicity against W. bancrofti microfilariae whereas none of the mf + ve sera had any such activity. Immunoblotting studies revealed that a protein with mol. wt of 79 KDa was the only one among the proteins of B. malayi microfilarial extracts that was consistently recognised by sera from all endemic residents. Endemic normal sera and elephantoid sera, which exerted maximum cytotoxicity, together specifically recognised three proteins with molecular weights 25, 58 and 68 KDa and these three proteins could be among the candidate antigens that induce resistance to filarial infection.

Animals↗
PubMed1990

Brain perfusion SPECT using an annular single crystal camera: initial clinical experience.

The annular single-crystal brain camera (ASPECT) is a digital SPECT system with a single-crystal sodium iodide thallium Nal(Tl) ring detector and collimator system designed to view the patient's head from three angles simultaneously. The ring is rotated concentrically to the detector for three-dimensional reconstruction over a 21.4 cm (diameter) by 10.7 cm (length) field of view. We evaluated the system clinically by imaging a Hoffman brain phantom and seven subjects, of whom two were normal controls, three had previous cerebral infarction and two had dementia. The ASPECT system produced tomographic images of high spatial resolution. In normal subjects, the separation of striata from thalami by the posterior limbs of the internal capsules was much clearer on ASPECT images than on rotating gamma camera images. The high spatial resolution obtained with the ASPECT system translates into superior anatomical representation of the brain compared to the standard rotating gamma camera.

Adult↗
PubMedDate not supplied

Brain perfusion SPECT in a cerebellar infarction.

Brain perfusion single photon emission CT (SPECT) has been used effectively in the evaluation of neurological diseases including stroke. Recently the introduction of annular special purpose systems has resulted in substantially improved spatial resolution. High resolution SPECT allows us to look accurately at the functional abnormalities resulting from small structural defects. We present a case of infarction in the territory of the posterior inferior cerebellar artery which illustrates the utility of this method.

Adult↗