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K Rezai

Publications and source records attributed to K Rezai.

16 recordsLinked to original sources
PubMed1992

Hypofrontality in neuroleptic-naive patients and in patients with chronic schizophrenia. Assessment with xenon 133 single-photon emission computed tomography and the Tower of London.

The "hypofrontality hypothesis" has been supported by many neuroimaging studies, but not all, perhaps because of heterogeneity of samples. The present study examined three different samples that permitted assessment of a variety of confounders, such as effects of long-term treatment, chronicity of illness, and presenting phenomenology: (1) 13 neuroleptic-naive schizophrenic patients, (2) 23 nonnaive schizophrenic patients who had been relatively chronically ill but were medication free for at least 3 weeks, and (3) 15 healthy normal volunteers. Regional cerebral blood flow was measured using single-photon emission computed tomography with xenon 133 as the tracer. The control condition consisted of looking at undulating colored shapes on a video monitor, while the experimental task was the Tower of London. We observed the Tower of London to be a relatively specific stimulant of the left mesial frontal cortex (probably including parts of the cingulate gyrus) in healthy normal volunteers. Both the neuroleptic-naive and the nonnaive patients lacked this area of activation, as well as a related one in the right parietal cortex (representing the circuitry specifically activated by the Tower of London). Decreased activation occurred only in the patients with high scores for negative symptoms. These results suggest that hypofrontality is related to negative symptoms and is not a long-term effect of neuroleptic treatment or of chronicity of illness.

Adult↗
PubMed1992

Abnormal captopril renogram in a patient without renovascular hypertension.

Captopril renal scintigraphy is a well-known noninvasive tool in the diagnosis of renovascular hypertension. The authors present a case of a patient with malignant hypertension whose captopril renal scintigraphy suggested bilateral and equal renovascular hypertension. His renal angiogram, however, demonstrated no renal artery stenosis or abdominal aortic atherosclerotic disease. False-positive captopril renal scintigraphy has been reported but can usually be attributed to the patient's hypotensive episode after captopril administration, volume or salt depletion, or chronic glomerulonephropathy. This patient demonstrated mild blood pressure changes after captopril administration and was not volume or salt depleted. His creatinine was 1.6 mg/dl on admission but demonstrated appropriate renal function on subsequent noncaptopril renal scintigraphy.

Captopril↗
PubMed1992

Coronary artery disease and cardiac events with asymptomatic and symptomatic cerebrovascular disease.

BACKGROUND AND PURPOSE: The purpose of this study was to evaluate the prevalence of coronary artery disease and coronary events during follow-up in patients with asymptomatic carotid stenosis, transient ischemic attacks, or small strokes. METHODS: We prospectively studied 60 consecutive patients with thallium-201 scintigraphy followed by coronary arteriography according to an established protocol. RESULTS: The 201Tl testing was abnormal in seven of 15 patients (47%) with asymptomatic carotid stenosis and in 19 of 44 patients (43%) with transient ischemic attacks or small strokes (p greater than 0.05). In 33 patients with no history of coronary artery disease, 11 (33%) had reversible 201Tl defects. In 26 patients with a history of coronary artery disease, 15 (58%) had reversible and/or fixed defects (p = 0.054 compared with patients with no history). A history of peripheral vascular disease was the only risk factor significantly associated with an abnormal 201Tl test (p = 0.032). Coronary artery stenosis of greater than 50% was identified in one or more vessels in 14 of 15 patients undergoing coronary arteriography. Over a mean follow-up period of 311 days, four patients (7%) developed new onset of angina. There were four coronary events among 14 patients (29%) with both a reversible area on the 201Tl and abnormal coronary arteriography. In comparison, there were only four coronary events among 46 patients (9%) without reversible defects on the 201Tl studies (p = 0.055). CONCLUSIONS: Our study demonstrates that one third of patients with no history of coronary artery disease had an abnormal 201Tl test and that nearly one half of patients with either symptomatic or asymptomatic cerebrovascular disease had abnormal 201Tl tests. Patients with a reversible 201Tl defect and significant stenosis by coronary arteriography were at higher risk for subsequent cardiac events. These findings demonstrate the utility of screening patients with asymptomatic and symptomatic cerebrovascular disease for cardiac disease.

Adult↗
PubMed1992

Image processing for the study of brain structure and function: problems and programs.

Fundamental problems in the analysis of functional and structural imaging data include data transport, boundary identification (including manual tracing, edge detection, and tissue segmentation), volume estimation, three-dimensional reconstruction and display, surface and volume rendering, shape analysis, and image overlay. These problems require that research investigators have access to suitable methods of image analysis, implemented on a set of software programs, in order to conduct neuroimaging research. The authors describe a group of software programs designed to provide a comprehensive solution for these problems.

Brain↗
PubMed1992

MR imaging and HMPAO scintigraphy in conjunction with balloon test occlusion: value in predicting sequelae after permanent carotid occlusion.

OBJECTIVE: Permanent occlusion of the internal carotid artery may be required for en bloc resection of a neck tumor or to treat certain aneurysms. The risk of ischemic infarct is usually assessed with carotid balloon test occlusion and concurrent distal arterial pressure measurement. However, up to 20% of patients who tolerate the test occlusion have delayed neurologic sequelae. We propose enhanced MR imaging and hexamethylpropyleneamine oxime (HMPAO) scintigraphy to detect subclinical signs of ischemia and hypoperfusion as adjuncts to the balloon test occlusion to identify patients at risk for delayed sequelae. SUBJECTS AND METHODS: We prospectively examined 12 patients referred for balloon test occlusion of the carotid artery. Serial measurements of distal occluded internal carotid pressure were recorded. 99mTc-HMPAO was injected IV after 2 min of asymptomatic test occlusion, and single-photon emission computed tomographic (SPECT) data acquisition was done 1-6 hr later. Contrast-enhanced MR imaging was performed 1-8 hr after completion of the 30-min test occlusion. Signs of decreased perfusion or ischemia on these tests were compared with the mean distal arterial pressure and neurologic status of the patient during test occlusion. RESULTS: Seven (58%) of 12 patients had abnormal findings on HMPAO scintigraphy or contrast-enhanced MR imaging. Only one patient had neurologic deficits that corresponded to abnormal MR enhancement. The other 11 patients (92%) remained asymptomatic during the 30-min test occlusion. Of these 11 asymptomatic patients, five (45%) had areas of decreased perfusion on scintigraphy and three (27%) had abnormal MR contrast enhancement suggesting residual focal ischemia as a result of the test occlusion. Mean arterial pressures in the distal occluded artery did not correlate well with the imaging results. CONCLUSION: HMPAO scintigraphy can show clinically silent areas of decreased perfusion, while enhanced MR shows signs of acute ischemia (i.e., significant hypoperfusion) associated with asymptomatic balloon test occlusion. Theoretically, such patients would be at increased risk for permanent sequelae after permanent carotid occlusion.

Adult↗
PubMed1991

[Prenatal chromosome findings in sonographically conspicuous fetuses].

A retrospective evaluation of 463 prenatal chromosome analyses in a total of 375 patients with suspicious ultrasound findings, revealed a high rate of severe chromosomal abnormalities (16%). The highest risk for an abnormal karyotype was found after sonographic detection of hygroma colli. Abnormal chromosome counts were also frequently found in fetuses with omphaloceles, duodenal atresia and hydrops fetalis, as well as in presence of intrauterine growth retardation and/or anomalies of the amniotic fluid volume. The anomalies mentioned above are, therefore, an urgent indication for a prenatal chromosome analysis. The technical improvements of ultrasound machines and growing experience of operators will lead to an increasing importance of sonography as a method for the identification of pregnancies, that are at high risk for chromosomal abnormalities.

Adolescent↗
PubMed1991

Relative accuracy of three scintigraphic methods for determination of right ventricular ejection fraction: a correlative study with ultrafast computed tomography.

The accuracy of three scintigraphic methods for determination of right ventricular ejection fraction (RVEF) was tested in 29 patients using ultrafast computed tomography (UFCT) as the gold standard. RVEF measurements by the ECG-gated first-pass approach showed excellent correlation with the UFCT results (r = 0.96, y = 0.06 + 0.91x), while both the standard gated acquisition blood-pool imaging (r = 0.71, y = 0.14 + 0.59x) and the nongated first-pass curve approach (r = 0.63, y = 0.18 + 0.37x) significantly underestimated RVEF. The error can be ascribed to partial inclusion of the atrial activity in the region assigned to the right ventricle. The tricuspid valve plane was found to move by a distance equal to 9%-33% (mean = 20%) of the right ventricular long-axis between systole and diastole. This translational motion was more pronounced with higher EFs.

Adult↗
PubMed1991

Physiological assessment of sensitivity of noninvasive testing for coronary artery disease.

The sensitivity of three noninvasive tests for coronary artery disease was assessed by means of quantitative indexes of disease severity in three different groups of patients. The overall population consisted of 110 subjects with limited coronary artery disease and no myocardial infarction. Planar dipyridamole-201Tl scintigraphy was evaluated in 31 patients, computer-assisted exercise treadmill in 28, and high-dose dipyridamole echocardiography testing in 51. Sensitivity was assessed by rigorous gold standards to define disease severity, such as measurement of minimum cross-sectional area and percent area of stenosis, by quantitative computerized coronary angiography (Brown/Dodge method). On the basis of the results of previous studies, the presence of physiologically significant coronary artery disease was indicated by a stenotic minimum cross-sectional area (MCSA) of less than 2.0 mm2 or a greater than 75% area of stenosis. With MCSA as the gold standard, dipyridamole-201Tl scintigraphy, computerized exercise treadmill, and dipyridamole echocardiography testing showed sensitivities of 52%, 54%, and 61%, respectively, in the three different patient cohorts enrolled. With percent area of stenosis as the gold standard, the sensitivity figures obtained for dipyridamole-201Tl, computerized exercise treadmill, and dipyridamole echocardiography testing were 64%, 54%, and 69%, respectively. For each of the three tests, sensitivity increased with increasing lesion severity. Sensitivity was also better in patients with left anterior descending coronary (LAD) disease when compared with patients with left circumflex or right coronary artery disease. Results of these studies, which were obtained with more strict patient selection criteria and by more rigorous gold standards than previous studies, demonstrate that in patients with limited coronary artery disease none of the tests evaluated is definitely superior in sensitivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Disease↗
PubMed1990

Progressive aphasia in a patient with Pick's disease: a neuropsychological, radiologic, and anatomic study.

Although Pick's disease is generally considered as a dementia characterized by signs of frontal lobe dysfunction, it can present with selective language defects rather than with cognitive decline. In this study, we report prospective and serial clinical, neuropsychological, and neuroradiologic observations in a 59-year-old man whose prominent disturbance was in the retrieval and learning of names denoting concrete entities and actions. Postmortem study confirmed the diagnosis of Pick's disease and revealed that neuronal loss and gliosis were most prominent in left anterior temporal cortices. The findings are in keeping with evidence that the left anterior temporal cortices and interconnected hippocampal system are critically involved in the learning and retrieval of verbal lexical items. The evidence from this patient, along with similar evidence from the literature we reviewed, suggests that when patients present with a progressive aphasia characterized by anomia, Pick's disease should be considered as the probable diagnosis.

Aphasia↗
PubMed1990

The incidence of serious hemodynamic changes in physically-limited patients following oral dipyridamole challenge before thallium-201 scintigraphy.

Dipyridamole has liberalized referrals for stress TI-201 chloride (thallium) studies at the Iowa City Veterans Administration Medical Center. Seventy-five percent of referrals now receive dipyridamole and, unlike patients who tolerate conventional exercise testing, these patients are often quite debilitated. Therefore, the hemodynamic consequences of dipyridamole were reviewed in 120 consecutive, physically-limited patients referred for thallium scintigraphy following an average oral dose of 5.4 mg/kg. Each patient's blood pressure was measured every 5 minutes for 1 hour after dipyridamole and compared with several clinical factors to determine if blood pressure change was predictable. In all patients, blood pressure changed from 136 +/- 21/83 +/- 15 (mean +/- 1 SD) to 117 +/- 25/72 +/- 15 following dipyridamole administration. One hundred nine of the 120 patients had a blood pressure decline from 137 +/- 21/82 +/- 12 to 113 +/- 21/70 +/- 13. Of the 109, 43% (N = 47) had a systolic blood pressure decline greater than 20 mmHg, 16% (n = 18) greater than 40 mmHg, and 13% (n = 14) greater than 50 mmHg. Thirteen percent (n = 14) required emergent reversal of the dipyridamole with aminophylline. Significant hypotension is relatively common but generally unpredictable after oral dipyridamole. Therefore, patient eligibility criteria should be carefully considered; strict hemodynamic monitoring must be routine in the usual patient undergoing thallium scintigraphy after oral dipyridamole challenge.

Administration, Oral↗
PubMed1989

Patterns of regional diastolic function in the normal human left ventricle: an ultrafast computed tomographic study.

The detailed evaluation of regional diastolic filling at multiple ventricular levels in the normal human left ventricle has not previously been reported. Ultrafast computed tomography was used to characterize global and regional early diastolic filling in the left ventricle of 11 normal male volunteers. Regional early diastolic filling data from six distinct ventricular levels (apex to base) were fit to a third-order polynomial curve, and the peak rate of diastolic filling and time of peak filling were determined. Peak filling rate was 259 +/- 17 ml/s (+/- SEM) as a global average, where peak filling rate referenced to end-diastolic volume and stroke volume across the levels examined was 3.78 +/- 0.17 s-1 and 4.83 +/- 0.20 s-1, respectively. Average filling fraction was 39 +/- 1%, and time to peak filling from end-systole was 145 +/- 5 ms. Regional (tomographic) peak filling rates, except for the most apical level examined, were not statistically different across the ventricle. Filling fraction and time to peak filling were remarkably constant from one level to another. However, reference of regional peak filling rate to regional end-diastolic volume demonstrated significant nonuniformity from apex (120% of average for all levels) to base (87% of average for all levels). Peak filling rate referenced to tomographic stroke volume was less variable and not statistically different across the ventricle as a whole.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Osteomyelitis of the foot in diabetic patients: evaluation with plain film, 99mTc-MDP bone scintigraphy, and MR imaging.

Diagnosis of osteomyelitis of the foot in diabetic patients may be difficult because of the coexistence of chronic cellulitis, vascular insufficiency, and peripheral neuropathy. This study compared the diagnostic accuracies of plain films, bone scans, and MR imaging studies in diabetic patients with suspicion of osteomyelitis of the foot. Twenty-nine plain radiographs, 20 bone scans, and 30 MR studies were obtained in 24 patients. Twenty-nine bones from 14 patients were pathologically proved either positive (25 bones) or negative (four bones) for osteomyelitis. Another 15 bones (10 patients) studied with MR had no pathologic proof, but the bones healed with only local wound care and/or a short course of oral antibiotics. These patients had trauma, cellulitis, or unhealed ulcers. The sensitivity and specificity of plain films were both 75%. Bone scans had a very low specificity (100% false-positive rate). A negative bone scan should strongly exclude the probability of osteomyelitis. Unlike the findings in previous reports, MR had much higher sensitivity and specificity than bone scans in detecting osteomyelitis in diabetic patients. When the 10 patients without pathologic proof (those who presumably had neuroarthropathy, vascular insufficiency, and/or cellulitis) were included, the sensitivity and specificity of all three techniques decreased. Our experience with this small group of patients suggests that MR is a useful imaging technique for diagnosing osteomyelitis of the foot in diabetic patients.

Adult↗
PubMed1988

Validation studies for brain blood flow assessment by radioxenon tomography.

A tomographic technique has been used recently for cerebral blood flow measurements with inhaled radioxenon. Based on experiments in a specially developed dynamic phantom and on studies in primates in vivo, we have analyzed the validity of this method for measurements of both regional and total blood flow in the brain. We have also examined the errors introduced into flow computations as a function of changes in such parameters as: rate of xenon input, size of region of interest, magnitude of regional flow rates, and inter-regional flow differences. Our findings indicate a reasonable degree of accuracy for flow measurements in gray matter regions that are 3 cm in diameter or larger, while white matter blood flow is generally overestimated. The accuracy for regional flow assessments degrades as a function of: diminishing region size, increasing inter-regional flow differences, and flow rates in excess of 100 ml/100 g/min. Measurements for brain regions 2 cm or smaller in diameter can be in error by 25-50% as a result of partial volume averaging. Although the technique is not ideal for accurate flow measurements in small regions of the brain, it nevertheless provides a convenient means of assessing perfusion in major vascular territories of the brain in routine clinical applications.

Animals↗