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Biomedical subjects

F J Bonte

Publications and source records attributed to F J Bonte.

At least 37 records · Page 2Linked to original sources
PubMed1989

Regional cerebral function and blood flow: complementary single photon emission computed tomography of the brain using xenon-133 and [123I]iodoamphetamine.

Regional cerebral function and blood flow can be imaged using isopropyl[123I]iodoamphetamine (IMP), or 133Xe (DSPECT), respectively. Both of these essentially non-invasive, quantitative, methods are suitable for many nuclear medicine laboratories. This study assessed the in vivo information about intracerebral disease provided by IMP and DSPECT techniques to determine the optimal diagnostic use of these modalities. Single photon emission computed tomograms of 53 subjects were acquired using similar displays for IMP and DSPECT data. Lobar tracer distributions were graded by three experienced observers and analyzed using a kappa statistic to eliminate chance agreements. Overall, both IMP and DSPECT had similar patterns. However, while similar, one or the other technique often displayed abnormalities not present on both. Although technical factors may account for some differences between the modalities, a case of arteriovenous malformation proves that discordant findings can result directly from tracer localization properties. Thus at least some discordances provide truly complementary diagnostic information lacking in either single study taken alone.

Adult↗
PubMed1989

The effect of acetazolamide on regional cerebral blood flow in patients with Alzheimer's disease or stroke as measured by single-photon emission computed tomography.

Regional cerebral blood flow (rCBF) was assessed in 35 patients with possible or probable Alzheimer's disease (AD) and in 16 patients known to have had at least one stroke. Patients were evaluated before and after the administration of 1 g acetazolamide (ACZ) by means of a rotating four-detector single-photon emission computed tomograph (SPECT) and inhaled Xe-133. RCBF values in mL/minute/100 g were derived from eight cortical regions of interest (ROI), and from the whole transverse section as a measure of whole brain flow (WBF). ROI/WBF ratios were calculated for each ROI in paired determinations done before and 15 minutes after the administration of ACZ. Results were compared with those previously obtained in a study of 15 normal, healthy volunteer subjects. ROI/WBF ratios greater than 2 standard deviations (SD) below the mean for a given ROI in the normal group were regarded as probably abnormal, whereas ratios greater than 4 SD below the mean were considered definitely abnormal. After ACZ administration, the number of ROI greater than 2 SD below the normal mean decreased significantly in the AD group and was unchanged in the stroke patients. However, the number of ROI/WBF ratios greater than 4 SD below the normal mean fell in the AD group and rose in the stroke group, with the difference in behavior highly statistically significant. Thus, the response of low-flow areas to ACZ differs in AD and in stroke, which could be of ultimate diagnostic significance.

Acetazolamide↗
PubMed1989

Intracranial arteriovenous malformation: relationship between clinical factors and surgical complications.

Serious morbidity and hyperemic states continue to complicate the treatment of certain intracranial arteriovenous malformations (AVMs). Clinical and radiographic characteristics of 62 patients treated over 3 years were analyzed to determine if hyperemic complications (HCs) (defined as unusual perioperative edema or hemorrhage) and outcome could be predicted. Twenty-five (40%) of the patients were less than 30 years old, 28 (45%) were between 30 and 50, and 9 (15%) were more than 50. A history of hemorrhage was found in 48%, and 34% presented with progressive deficits. Thirteen (21%) developed evidence of HCs; 51 (82%) ultimately had a good outcome, 4 (6%) had a poor outcome, and 7 (11%) died. The incidence of HCs was higher in patients whose AVMs recruited perforating vessels (53%) than those without (7%) (P less than 0.001). The presence of preoperative angiographic steal carried a 35% risk of HCs whereas its absence carried a 13% risk (P less than 0.05). The sum of the diameters of the feeding vessels was also predictive (P less than 0.05). Outcome was clearly age-related: good outcome was achieved in 92% of the patients less than 30 years old, 86% of those 30 to 50, and 44% of patients older than 50 (P less than 0.05). Left hemispheric AVMs showed less morbidity than right (P less than 0.05) as did those without perforating vessel recruitment (P less than 0.07). HCs had a dramatic impact on outcome with 92% of patients without HCs having good outcome and 46% of those with HCs recovering well (P less than 0.001).

Adult↗
PubMed1989

Intracranial arteriovenous malformation: relationships between clinical and radiographic factors and cerebral blood flow.

Arteriovenous malformations (AVMs) dramatically alter normal cerebral circulatory dynamics. Clinical and radiographic data from 62 patients were analyzed to determine their impact on total brain blood flow (TBF) measured by single-photon emission computed tomography. 48% of patients presented with hemorrhage and 34% with progressive deficits. 37% had angiographic steal and 21% developed postoperative hyperemic complications. 40% were under 30 years old, 45% were between 30 and 50 years of age, and 15% were over 50. TBF was less than 70 ml/100 gm/min in 32% of patients, between 70 and 84 ml/100 gm/min in 40%, and greater than 84 ml/100 gm/min in 27%. Female patients had higher TBF than males; 42% of females but only 17% of males had values greater than 84 ml/100 gm/min (p less than 0.05). A trend toward decreased TBF with advancing age was noted. Intracranial hemorrhage was associated with lower TBF; 47% of patients with hemorrhage and 19% of those without had TBF of less than 70 ml/100 gm/min (p less than 0.05). 89% of patients with AVMs less than 5 cm in diameter had TBF of less than or equal to 84 ml/100 gm/min, and 65% of those with larger AVMs had similarly low flows (p less than 0.05). A trend toward lower TBF was observed in patients with unfavorable outcomes.

Adult↗
PubMed1989

Intracranial arteriovenous malformation: contralateral steal phenomena.

Sixty-two patients with radiographically proven intracranial arteriovenous malformations underwent preoperative regional cerebral blood flow measurement with 133Xe single-photon emission computed tomography. Contralateral regions of hypoperfusion were detected in all cases. Steal severity was assessed according to the contralateral steal index [ISteal(c)]. ISteal(c) was greater than 0.7 (severe) in 22 (35%), 0.7-0.8 (intermediate) in 18 (29%), and greater than 0.8 (mild) in 22 (35%). ISteal(c) was more frequently severe or mild in females and more often intermediate in males (p less than 0.05). Hyperemic complications were encountered more frequently in patients with intermediate ISteal(c) (p = 0.086). An unfavorable outcome was associated with less severe contralateral steal (p = 0.12). A detailed clinical, radiographic, and hemodynamic profile may help to preoperatively identify patients at high risk for a poor surgical outcome.

Adult↗
PubMed1988

A long-term follow-up case study of crossed aphasia assessed by single-photon emission tomography (SPECT), language, and neuropsychological testing.

A 65-year-old man with well-defined crossed aphasia secondary to right cerebral infarction 10 years previously was studied for current language and cognitive abilities and regional cerebral blood flow (rCBF) during cognitive activation measured by single-photon emission tomography (SPECT). Reversed hemispheric lateralization was demonstrated by qualitative aspects of the patient's constructional deficits, dominant parietal lobe signs, and absence of the neglect syndrome. Language activation procedures during SPECT produced focal increases in rCBF to both frontal lobes with a phoneme detection task and to right temporal and parietal lobes with a math task. The authors stress the complexities of assessing brain/language mechanisms in vivo and demonstrate variabilities in rCBF during language activation dependent on task selection.

Aged↗
PubMed1988

Chernobyl retrospective.

On April 28, 1986 heavy radioactive fallout from an unknown source was reported from Sweden. Later, it was discovered that two days earlier, a nuclear power reactor at Chernobyl, in the Soviet Union, had exploded releasing an enormous cloud of effluent containing 40 million Ci of 131I, 3 million Ci of 137Cs, and 50 million Ci of xenon radioisotopes. This far exceeded the 15 Ci of 131I escape in the notorious Three Mile Island accident. Chernobyl reactor IV, of an antiquated design, was a graphite-moderated reactor which suffered a steam explosion when the operating staff attempted an experiment involving preservation of safety functions during a planned shutdown. Following the explosion, a fire started in the graphite core which required ten days to control. Thirty-one persons died, two in the initial explosion and 29 of various combinations of thermal and radiation burns, and gamma irradiation. Existing emergency plans were invoked involving treatment on the scene and evacuation of seriously injured patients to a special hospital in Moscow, as well as to nearby Kiev. Later, 135,000 residents of the immediate neighborhood were surveyed and evacuated after fallout radiation levels began to rise. Fallout patterns around Europe and the northern hemisphere were closely tracked. Consequences of the accident in human and monetary terms will require years of evaluation. Although the United States has no power reactors of the Chernobyl type, the country does have a radiation disaster management plan, often rehearsed at the state level. As a consequence of Chernobyl certain international agreements dealing with radiation disaster information and management have been forged.

Accidents↗
PubMed1988

The effect of acetazolamide on regional cerebral blood flow in normal human subjects as measured by single-photon emission computed tomography.

Regional cerebral blood flow (rCBF) was evaluated in 15 normal, healthy volunteer control subjects before and after the administration of 1 g acetazolamide (ACZ) using a rotating four-detector single-photon emission computed tomograph (SPECT). ACZ, a carbonic anhydrase inhibitor, is a cerebral vasodilator. RCBF values in mL/minute/100 g were derived within eight cortical regions of interest (ROI), and from the whole slice as an expression of whole brain blood flow (WBF). ROI/WBF ratios were established for each ROI in each of the 15 subjects for both pre-ACZ and post-ACZ studies. ACZ produced a 30% +/- 17% increase in WBF. Studies were done in random order, with nine subjects undergoing the post-ACZ study first, and six the pre-ACZ, or baseline, study first. Statistical analysis showed no significant difference in any ROI that might be caused by sequence of test procedures. Ratios were then examined to determine whether rCBF elevation was proportionate in all ROI in all subjects. No significant difference was found in any ROI except for the left parietal, for which marginally significant change was identified. Subjects also were examined for possible age and sex differences in ACZ response, and no differences were found.

Acetazolamide↗
PubMed1988

Cerebral blood flow changes during sodium-lactate-induced panic attacks.

Dynamic single-photon emission computed axial tomography (CAT) with inhaled xenon-133 was used to measure regional cerebral blood flow in 10 drug-free patients with DSM-III-diagnosed panic disorder and in five normal control subjects. All subjects underwent regional cerebral blood flow studies while at rest or during normal saline infusion and during sodium lactate infusion. Six of the 10 patients and none of the control subjects experienced lactate-induced panic attacks. Lactate infusion markedly raised hemispheric blood flow levels in both control subjects and patients who did not panic. Patients who did panic experienced either a minimal increase or a decrease in hemispheric blood flow.

Adult↗
PubMed1988

Intracranial arteriovenous malformation: relationships between clinical and radiographic factors and ipsilateral steal severity.

Intracranial arteriovenous malformations (AVMs) are high flow shunts that may jeopardize the perfusion of adjacent tissue. Clinical and radiographic data from 62 patients were analyzed to determine their relationship to the severity of steal measured by single photon emission computed tomography (SPECT). The ipsilateral steal index [ISteal(i)] was determined by dividing regional cerebral blood flow (rCBF) values within hand-drawn regions of hypoperfusion in the ipsilateral hemisphere by total brain flow, which was calculated as the average rCBF of each hemisphere. Of the patients, 40% were less than 30 years of age, 45% were 30 to 50 years old, and 15% were over 50. Forty-eight per cent presented with hemorrhage and 34% presented with progressive deficits. There was angiographic steal in 37%, and postoperative hyperemic complications developed in 21%. All patients had ipsilateral regions of hypoperfusion. The ISteal(i) was less than 0.7 in 23 (37%), 0.7 to 0.8 in 20 (32%), and greater than 0.8 in 19 (31%). The ISteal(i) was significantly less severe in the patients over 50; 78% of these patients had an ISteal(i) of greater than 0.8 (P less than 0.01). A history of hemorrhage was associated with less severe steal than that in patients who had not bled (P = 0.088). Patients presenting with a history of progressive deficits had increased severity of steal compared with those without progressive deficits (P less than 0.05). A trend toward decreased severity of steal was noted in patients with unfavorable outcomes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Improvement in regional cerebral blood flow and cerebral vasoreactivity after extracranial-intracranial arterial bypass.

Regional cerebral blood flow was measured with xenon-133 inhalation single photon emission computed tomography in a patient who developed a neurological deficit after carotid ligation. Hemispheric hypoperfusion was noted in resting studies and impaired vasoreactivity was suggested by lack of symmetrical flow augmentation after acetazolamide administration. Because of progressive neurological deterioration, an extracranial-intracranial bypass was performed. After prompt neurological improvement, repeat cerebral blood flow measurements at 1 and 9 weeks postoperatively confirmed improvement in resting flow and vasoreactivity. It is possible that decreased cerebrovascular reserve implied by measurements of vasoreactivity can identify patients who will benefit from surgical revascularization.

Aged↗
PubMed1987

Antihypertensive therapy in the elderly. Effects on blood pressure and cerebral blood flow.

Antihypertensive therapy significantly reduces cardiovascular morbidity and mortality in the rapidly growing population of elderly patients. However, the desire to treat more of these patients is dampened by the concern that a reduction in blood pressure may compromise cerebral blood flow, causing untoward consequences. This study evaluated the therapeutic effect of titrated doses of prazosin, an alpha-adrenergic blocking agent, on systemic blood pressure and cerebral blood flow in elderly patients with chronic stable hypertension. Prazosin alone or co-administered with hydrochlorothiazide significantly lowered mean systolic and diastolic blood pressures in 31 elderly hypertensive patients. At the same time, however, there was no significant change in cerebral blood flow, which was measured in eight patients. Neither harmful biochemical changes nor treatment-related adverse effects were observed in any patients. Prazosin therapy alone or in combination with low-dose diuretic therapy was effective in the treatment of hypertension in this elderly population. Furthermore, blood pressure reduction with prazosin therapy was accomplished without compromising cerebral blood flow and without unfavorably altering lipid profiles.

Aged↗
PubMed1986

Quantification of intracerebral steal in patients with arteriovenous malformation.

Eleven patients with angiographically and/or pathologically proved arteriovenous malformations (AVMs) were studied using dynamic, single-photon-emission computed tomography (DSPECT). Quantification of regional cerebral blood flow in structurally normal areas remote from the AVM disclosed areas of decreased flow compared with normal controls in eight of 11 patients examined. Areas of hypoperfusion correlated with altered function as manifested by epileptogenic foci and impaired cognitive function. Dynamic, single-photon-emission computed tomography provides a noninvasive technique to monitor quantitatively hemodynamic changes associated with AVMs. Our findings suggest that such changes are present in the majority of patients with AVMs and that they may be clinically significant. The potential application of regional cerebral blood flow imaging by DSPECT in the management of patients with AVMs is discussed.

Adult↗
PubMed1986

Normal distribution of regional cerebral blood flow measured by dynamic single-photon emission tomography.

Regional CBF (rCBF) was measured quantitatively using the inert-gas washout technique with xenon-133 and single-photon emission computed tomography. Tomographic data were reconstructed by filtered back projection, and flow was calculated according to the double-integral method. Ninety-seven subjects ranging in age from 20 to 59 years received a single examination; eight of these received a second examination within 1 h of the first; seven others received a second examination separated from the first by 1-10 days. Transverse-section images were obtained at 2, 6, and 10 cm above and parallel to the canthomeatal line (CML). Cortical gray matter flows were obtained from 12 brain regions in the slice 6 cm above the CML, and cerebellar and inferior cerebral gray matter flows were obtained from 4 regions in the slice 2 cm above the CML. Mean gray matter flow was 72 +/- 12 ml/min/100 g, with highest flows in the parietal lobes and visual cortex. No significant differences in rCBF occurred when a second study followed the first by 30 min to 10 days. Right-sided rCBF was slightly higher than left in all regions except frontal and parietal lobes where there was no difference. Flow was higher in women than in men and declined mildly with age for both sexes (slope = -0.33 ml/min/100 g/year; p less than 0.05).

Adult↗
PubMed1984

Error analysis of the double-integral method for calculating brain blood perfusion from inert gas clearance data.

A single-photon dynamic computer-assisted tomograph (DSPECT) has been built and is currently being used to evaluate regional cerebral blood perfusion in patients and volunteers. A computer simulation of the system was created to analyze the effects of data collection, Poisson noise, attenuation compensation, and the reconstruction technique now employed in the DSPECT. Several methods of attenuation compensation were used to generate perfusion images from both ideal and noisy data. The results indicate that the mean perfusion is calculated to within 10.4% accuracy for all perfusion rates in a region of interest if attenuation correction is used. Without attenuation correction, perfusions are underestimated by as much as 27%. The three correctors tested have different effects on the calculated perfusion value, depending on the location of the region of interest in the picture. The algorithm introduces random noise that is proportional to both the random error in the input data and the perfusion rate. Air-curve delay errors result in inaccuracies in the final perfusion picture that are proportional to perfusion rate. Physiological values (0.8-1.5) of the partition coefficient cause overestimation of both gray (0-34%) and white (7-67%) matter perfusion values. Compton scatter and collimator effects were not addressed in this study.

Brain↗