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Biomedical subjects

N A Mullani

Publications and source records attributed to N A Mullani.

At least 19 recordsLinked to original sources
PubMed2001

Pallidotomy: a comparison of responders and nonresponders.

OBJECTIVE: We reviewed a prospective series of 32 unilateral, large-volume, microelectrode-guided posteroventral pallidotomies to determine the differences between responsive and nonresponsive patients. METHODS: Our patients underwent extensive pre- and postoperative evaluations. One year postoperatively, we correlated the outcomes of 25 patients with their histories, physical findings, neuropsychological assessments, and lesion characteristics to further understand the indications, limitations, and pitfalls of unilateral pallidotomy. Our group judged responsiveness by comparing the preoperative total Unified Parkinson's Disease Rating Scale off-state scores with those obtained 1 year postoperatively. A score indicating greater than 20% improvement at 1-year follow-up was rated a good outcome; improvement of greater than 40% was rated an excellent outcome. RESULTS: Although most patients sustained long-term benefits, some demonstrated little or no improvement. Patient and lesion factors influenced outcome. Younger age (<60 yr), tremor, unilateral predominance, L-dopa responsiveness, motor fluctuations with dyskinesia, and good lesion placement predicted a good response to unilateral pallidotomy. Advanced age (>70 yr), absence of tremor, increased duration of disease, reduced responsiveness to L-dopa, frontal behavioral changes, prominent apraxic phenomena, and improper lesion placement predicted a poor response. CONCLUSION: Unilateral, large-volume pallidotomy with precise lesion control provides long-lasting benefits for carefully selected patients.

Aged↗
PubMed2000

Fewer women than men have positive SPECT and PET cardiac findings among patients with no history of heart disease.

UNLABELLED: A lower detection rate of coronary artery disease (CAD) has been reported for SPECT imaging in women, despite the fact that similar numbers of women and men die each year of heart disease. Ruling out instrumentation as a possible source of this low detection rate for CAD in women could be important in determining the root cause of this difference. METHODS: Patients were referred by cardiologists and randomized to PET or SPECT by the imaging center. A total of 210 patients (106 women, 104 men) were enrolled in this study, with 105 imaged by dual-isotope SPECT and 105 imaged by 82Rb PET. Rest/stress scanning was performed using dipyridamole. The effects of sex, prior history of CAD, and instrumentation on the detection of positive scans were determined using multiple logistic regression analysis with positive scans as the endpoint. RESULTS: For the total study population, sex and prior history of CAD are significantly associated with positive scans, whereas imaging modality and age are not. There was no significant interaction between sex and prior history of CAD. Men have 4.1-fold greater odds of having a positive nuclear scan than women, and patients with prior history of CAD have 5.2-fold greater odds of a positive scan after controlling for the confounding effects of age and imaging modality. In the subgroup of patients with no prior history of heart disease, men have 3.9-fold greater odds of a positive scan than women, and the odds ratio of a positive scan is 2.5-fold greater for PET than for SPECT. There was no statistical difference in the number of positive scans by SPECT or PET, or positive scans by sex in patients with documented history of CAD. CONCLUSION: Fewer women than men have positive nuclear cardiology scans by both PET and SPECT, despite similar symptoms. Instrumentation characteristics alone do not account for this sex-based difference and suggest the possibility that early CAD may present differently in women than in men.

Aged↗
PubMed1997

Effects of duration of epilepsy on the uncoupling of metabolism and blood flow in complex partial seizures.

We derived interhemispheric asymmetry indices (AIs) in interictal glucose uptake and blood flow in the temporal lobes of patients with intractable complex partial seizures from 18F and 15O positron emission tomograms. All patients subsequently underwent either left (n = 16) and right (n = 18) temporal lobectomy. We determined the effects on AIs of clinical seizure variables, including duration of seizure disorder, age at seizure onset, frequency of complex partial seizures, history of secondary generalization, history of febrile seizures, and magnetic resonance imaging evidence for mesial temporal sclerosis. Duration of seizure disorder produced the only significant effects. Degree of interhemispheric asymmetry in both glucose uptake and blood flow increased with duration of seizure disorder. However, the rate of increase in asymmetry was significantly greater for glucose uptake than for blood flow. These results indicate that uncoupling of metabolism and blood flow is a progressive process that results from the differential response of glucose metabolism and blood flow to chronic seizure activity. The results also suggest that duration of seizure disorder may be an important variable to consider in the interpretation of PET studies for evaluation of seizure surgery candidates.

Adult↗
PubMed1994

A retrospective study of the diagnostic accuracy of a community hospital-based PET center for the detection of coronary artery disease using rubidium-82.

UNLABELLED: A retrospective analysis has been carried out to determine the diagnostic accuracy of PET of the heart with 82Rb at a community hospital based center. METHODS: Utilization statistics were derived from a total of 1460 patients scanned for the first 36 mo of the center's operation. Diagnostic accuracy for detection of coronary artery disease (CAD) was assessed using three readers blinded to the clinical information. A total of 287 rest and dipyridamole-stress scans of patients who had coronary angiograms within 6 mo of the PET scan were selected by the computer for this study. Each rest/stress scan was read by at least two of the three readers. RESULTS: The average sensitivity for all three readers was 87% for greater than 67% diameter stenosis and the average specificity was 88% for myocardial regions perfused by normal coronary arteries. The average accuracy was 88% for patients with greater than 67% diameter stenosis. Sensitivity and accuracy improved to 92% and 91% respectively for stenosis greater than 90% in diameter. CONCLUSION: These results compare well with published results from major hospital-based centers and the recently published results from a private PET center in Georgia.

Coronary Angiography↗
PubMed1991

A segmented attenuation correction for PET.

A segmented attenuation correction technique has been developed for positron emission tomography which computes attenuation correction factors automatically from transmission images for use in the final image reconstruction. The technique segments the transmission image into anatomic regions by thresholding the histogram of the attenuation values corresponding to different regions such as soft tissue and lungs. Average values of attenuation are derived from these regions and new attenuation correction factors are computed by forward projection of these regions into sinograms for correction of emission images. The technique has been tested with phantom studies and with clinical cardiac studies in patients for 30- and 10-min attenuation scan times. This method for attenuation correction was linearly correlated (slope = 0.937 and r2 = 0.935) with the standard directly measured method, reducing noise in the final image, and reducing the attenuation scan time.

Heart↗
PubMed1990

Feasibility of measuring first pass extraction and flow with rubidium-82 in the kidneys.

A feasibility study has been carried out to evaluate rubidium-82, a potassium analog and generator-produced positron emitter, for measuring renal blood flow using a first pass model. Seven acute dogs were studied with beta probes and positron emission tomography to understand the dynamics of rubidium-82 in the kidneys. Preliminary results show that first pass extraction fraction for rubidium-82 ranged from 80-95% with an average of 89%. During the 150 sec of data collection, approximately 44.5% of the injected dose is excreted in the venous side and 9.75% in the ureter. Flow measurements with rubidium-82 and microspheres correlated well with the average control flow of 5.0 ml/min/gm measured by microspheres and 4.5 ml/min/gm of flow measured by rubidium-82 using the first pass model.

Animals↗
PubMed1990

Design and performance of POSICAM 6.5 BGO positron camera.

A high-resolution, whole-body positron camera, POSICAM 6.5 BGO, has been designed, built, and tested; results from it are presented. The camera utilizes 1,320 BGO crystals and 720 PMTS in a staggered geometry to produce high resolution of 5.8 mm FWHM and 21 image planes simultaneously. The axial resolution of the camera is measured at 11.9 mm at the center. High axial sampling is achieved with 5.125 mm separation of the image planes such that three-dimensional imaging of an object can be carried out in a single scan. Recovery of volumetric distribution of radioactivity and object dimensions in axial and sagittal views is demonstrated by imaging spherical objects 13 mm to 39 mm in diameter.

Equipment Design↗
PubMed1989

Assessment of coronary artery disease severity by positron emission tomography. Comparison with quantitative arteriography in 193 patients.

To assess the accuracy of positron emission tomography (PET) for evaluation of coronary artery disease (CAD), cardiac PET perfusion images were obtained at rest and with dipyridamole-handgrip stress in 193 patients undergoing coronary arteriography. PET images were reviewed by two independent readers blinded to clinical data. Subjective defect severity scores were assigned to each myocardial region on a 0 (normal) to 5 (severe) scale. Results were compared with arteriographic stenosis severity expressed as stenosis flow reserve (SFR), with continuous values ranging from 0 (total occlusion) to 5 (normal), calculated from quantitative arteriographic dimensions using automated detection of the vessel borders. There were 115 patients with significant CAD (SFR less than 3), 37 patients with mild CAD (3 less than or equal to SFR less than 4), and 41 patients with essentially normal coronaries (SFR greater than or equal to 4). With increasingly severe impairment of stenosis flow reserve, subjective PET defect severity increased. Despite wide scatter, a PET score of 2 or more was highly predictive of significant flow reserve impairment (SFR less than 3). For each patient, the score of the most severe PET defect correlated with the SFR of that patient's most severe stenosis (rs = 0.77 +/- 0.06). For each of 243 stenoses, PET defect score correlated with the SFR of the corresponding artery (rs = 0.63 +/- 0.08). PET defect location closely matched the region supplied by the diseased artery, and readers agreed whether the most severe PET defect was less than or more than 2 for 89% of patients.

Angiography↗
PubMed1989

Economic analysis of clinical positron emission tomography of the heart with rubidium-82.

This report describes a cost analysis for clinical positron emission tomography (PET) of the heart using generator produced rubidium-82 (82Rb). Considered sequentially are the clinical problem, current noninvasive radionuclide methods, positron emission tomograph, and the cost of PET per study. Also analyzed are the costs of PET versus thallium imaging in the management of chest pain, for screening asymptomatic men at high risk for coronary artery disease and for evaluating myocardial viability after myocardial infarction or thrombolytic therapy. Noninvasive assessment of coronary artery stenosis and myocardial ischemia/viability in symptomatic or asymptomatic subjects remains a major medical problem because the sensitivity and specificity of thallium imaging are only 70-85% and 50-70%, respectively, in recent studies. Cardiac positron imaging has an accuracy for noninvasive diagnosis of coronary artery disease in symptomatic or asymptomatic patients with a sensitivity and specificity of 95-98%. It can also be used for assessing physiologic stenosis severity, for imaging myocardial infarction and viability, for assessing effects of interventions such as thrombolysis, percutaneous transluminal coronary angioplasty (PTCA) or bypass surgery on myocardial perfusion, metabolism or coronary flow reserve, for assessing collateral function noninvasively in man, and for diagnosing cardiomyopathy not due to coronary artery disease. Although the cost for cardiac PET with 82Rb may be modestly higher than for 201Tl, the greater diagnostic yield of PET results in comparable or lower overall medical management costs than no diagnostic tests/interventions and lower overall costs compared to thallium imaging for evaluating patients with chest pain, asymptomatic high risk males, and patients after acute myocardial infarction/thrombolysis for myocardial viability.

Adult↗
PubMed1988

Positron emission tomography instrumentation: an overview.

Positron emission tomography (PET) makes possible the quantitation of the regional distribution of positron-emitting radioisotopes in a selected organ (Ter Pogossian et al.: Radiology 114:89-98, 1975). Since a large variety of physiologic compounds can be labeled with positron emitters (Wolf: Seminars in Nuclear Medicine 11:2-12, 1981; Fowler and Wolf: Nuclear Science Series, 1982), the technique can be used to monitor various biochemical and physiological processes of living tissues (Phelps et al.: Annals of Internal Medicine 98:339-359, 1983; Brodie et al.: Handbook of Neurochemistry, 1983). Indeed, research in the clinical application of PET has expanded considerably over the past 5 years and PET has been used in a variety of clinical problems in psychiatric, neurologic, and oncologic disorders (Phelps and Mazziotta: Science 228:799-809, 1985; Patronas et al.: Journal of Neurosurgery 62:816-822, 1985; Volkow and Tancredi: International Journal of Technology Assessment in Health Care 2:577-594, 1986). Interpretation of the findings by the clinician has sometimes been confounded by the complexity of the technique and the many parameters which can influence the data. A simple knowledge of the methodological background of PET is needed in order to appreciate the potential applications and the limitations of this technique. There are three basic components in PET: instrumentation, radiopharmaceuticals, and mathematical modeling. A number of reviews address varied aspects of the last two components (Fowler and Wolf: Positron Emission Tomography and Autoradiography: Principals and Application of the Brain and Heart, 1986; Karlstrom and Christman: Brookhaven National Laboratory Associated Universities, Inc., 1983; Huang and Phelps: Positron Emission Tomography and Autoradiography: Principles and Applications for the Brain and Heart, 1986), and in this paper we will focus on PET instrumentation as it pertains to its clinical application. The aim of this article is to give an outline of the basic principles behind PET instrumentation, such as positron detection, resolution, quantitation, sensitivity, and image reconstruction as it affects the data presented to the clinician.

Brain↗
PubMed1987

Relation between geometric dimensions of coronary artery stenoses and myocardial perfusion reserve in man.

To determine the relation between stenosis anatomy and perfusion in man, 31 patients had quantitative coronary arteriography and positron imaging (PET) with Rb-82 or N-13 ammonia at rest and after dipyridamole-handgrip stress. 10 patients were also studied after angioplasty (total stenoses = 41). Percent narrowing and absolute cross-sectional luminal area were related through a quadratic function to myocardial perfusion reserve determined with PET. Arteriographically determined coronary flow reserve was linearly related to relative myocardial perfusion reserve as expected, based on the derivation of equations for stenosis flow reserve. All of the correlations had considerable scatter, indicating that no single measurement derived by coronary arteriography was a good indicator of perfusion reserve by PET in individual patients. This study provides the relation between all anatomic dimensions of coronary artery stenoses and myocardial perfusion reserve in man, and suggests that PET indicates the functional significance of coronary artery stenoses for clinical purposes.

Arterial Occlusive Diseases↗
PubMed1987

Changes in myocardial perfusion reserve after PTCA: noninvasive assessment with positron tomography.

The effect of percutaneous transluminal coronary angioplasty (PTCA) on myocardial perfusion reserve has not been previously determined. Accordingly, 11 patients underwent positron imaging with [13N]ammonia or 82Rb at rest and following dipyridamole + handgrip stress before and after PTCA. The ratio of stress to rest activity (S:R) was determined for each region of interest. Relative myocardial perfusion reserve by positron tomography (RMPR) was calculated by dividing S:R of the stenotic area by a corresponding value from a normal reference area of the same patient. Automated quantitative coronary arteriography was used to objectively measure the percent diameter (%D) and the percent area narrowing (%A) of the stenoses. In nine patients with successful PTCA, %D and %A improved (68 +/- 10 to 49 +/- 15% and 92 +/- 3 to 72 +/- 5%) and RMPR increased from 0.79 +/- 0.07 to 0.96 +/- 0.05. In the two patients in whom PTCA was unsuccessful, RMPR was unchanged. Changes in RMPR correlated inversely with changes in %D (r = -0.68) and %A (r = -0.92) and directly with improved coronary flow reserve derived from all stenosis measurements (r = 0.73, p less than 0.001 for each). This study suggests that dipyridamole + handgrip stress imaging with PET can be used to assess changes in myocardial perfusion reserve before and after PTCA with the potential for determining restenosis noninvasively.

Adult↗
PubMed1986

Noninvasive assessment of coronary stenoses by myocardial perfusion imaging during pharmacologic coronary vasodilation. VIII. Clinical feasibility of positron cardiac imaging without a cyclotron using generator-produced rubidium-82.

The purpose of this study was to determine the clinical feasibility of diagnosing significant coronary artery disease by positron imaging of myocardial perfusion without a cyclotron, using generator-produced rubidium-82 (82Rb). Fifty patients underwent positron emission tomography of the entire heart using a multislice positron camera and intravenous 82Rb or nitrogen-13 ammonia (13NH3) before and after intravenous dipyridamole combined with handgrip stress. Images were read by two observers blinded as to clinical or arteriographic data. Automated quantitative coronary arteriography was obtained for the arteriographic determination of coronary flow reserve, previously demonstrated to be a single integrated measure of stenosis severity accounting for all its geometric dimensions of length, absolute diameter, percent narrowing and asymmetry by quantitative analysis of cine films. Significant coronary artery disease was defined as an arteriographically determined coronary flow reserve of less than 3.0 based on all stenosis dimensions. Any single geometric measure of stenosis severity alone was an inadequate reference standard for comparison with perfusion images. Sensitivity of identifying patients with coronary artery disease having an arteriographically determined coronary flow reserve of less than 3.0 was 95% by positron imaging with a specificity of 100%. The single case that was missed, studied with 13NH3, had a 43% diameter narrowing of a small ramus intermedius off the left coronary artery with no significant narrowing of the major coronary arteries. Positron emission tomography of myocardial perfusion before and after intravenous dipyridamole combined with handgrip stress utilizing generator-produced 82Rb provides sensitive and specific diagnosis of reduced coronary flow reserve due to coronary artery disease in humans.

Coronary Angiography↗
PubMed1986

Positron imaging of myocardial infarction with rubidium-82.

Positron imaging provides tomographic images of regional myocardial perfusion but has required an on-site cyclotron. Rubidium-82 (82Rb) is a short-lived (T1/2 = 75 sec) positron emitter available from a generator. In order to determine the feasibility for its use to image acute myocardial infarction, 18 patients with transmural infarctions who had coronary arteriography were given 30-40 mCi of 82Rb intravenously and positron tomographic imaging was carried out within 96 hr after onset of symptoms. Nine simultaneous transaxial slices were obtained for each patient with a positron camera. Images were also reconstructed in a long-axis, short-axis, and three-dimensional display. One study could not be interpreted because of excessive lung activity. Fourteen normals were also studied. The infarct related artery determined by angiography was correctly diagnosed by positron imaging in all 17 patients as were all three prior infarcts by readers blinded to the clinical data. No defects were observed in normals or in noninfarcted myocardial regions. This study indicates that 82Rb should be useful for perfusion imaging in patients with acute myocardial infarction. The short half-life of 82Rb should make it ideal for providing serial assessment of perfusion in patients undergoing thrombolytic therapy.

Acute Disease↗