Auditory attentional deficits in patients with schizophrenia. A positron emission tomography study.

BACKGROUND: Patients with schizophrenia have frequently been found to perform poorly on tasks requiring selective attention, defined as the ability to focus attention on relevant information while simultaneously ignoring irrelevant stimuli. This study explores the brain mechanisms mediating attentional processing in patients with schizophrenia by measuring their regional cerebral blood flow (rCBF) with positron emission tomography using [15O] water as they performed tasks that differed systematically in attentional demand. METHODS: Ten schizophrenic patients (either neurolepticnaive or withdrawn from medication) (patient group) and 10 normal volunteers (control group) performed auditory target detection tasks. Different types of auditory stimuli (environmental sounds, meaningless speech sounds, and words) were presented either binaurally (ie, same sounds in both ears) or dichotically (simultaneous and different sounds in the 2 ears). In dichotic conditions, subjects were instructed to focus on either their left or right ear. RESULTS: Initial subtraction-based image analyses sought significant rCBF changes anywhere in the brain. Patients consistently had less significant activation than controls in right superotemporal gyrus (STG). Follow-up analyses used regions of interest traced on individual magnetic resonance images to precisely measure rCBF in STG. Unlike controls, patients had higher rCBF in the left STG during all activation conditions. CONCLUSIONS: The abnormal task-related rCBF asymmetry in STG of schizophrenic patients may indicate an isolated temporal lobe deficit, but it may also indicate abnormality in the thalamocortical circuitry mediating selective attention and/or in the brain systems that integrate auditory processing in the 2 hemispheres.

Emotional activation of limbic circuitry in elderly normal subjects in a PET study.

OBJECTIVE: This study was undertaken to identify brain structures associated with emotion in normal elderly subjects. METHOD: Eight normal subjects aged 55-78 years were shown film clips intended to provoke the emotions of happiness, fear, or disgust as well as a neutral state. During emotional activation, regional cerebral blood flow was measured with the use of [15O]H2O positron emission tomography imaging, and subjective emotional responses were recorded. Data were analyzed by subtracting the values during the neutral condition from the values in the various emotional activations. RESULTS: The stimuli produced a general activation in visual pathways that included the primary and secondary visual cortex, involving regions associated with object and spatial recognition. In addition, the specific emotions produced different regional limbic activations, which suggests that different pathways may be used for different types of emotional stimuli. CONCLUSIONS: Emotional activation in normal elderly subjects was associated with increases in blood flow in limbic and paralimbic brain structures. Brain activation may be specific to the emotion being elicited but probably involves complex sensory, association, and memory circuitry. Further studies are needed to identify activations that are specific for emotion.

Radioisotope myelography in detection of spinal fluid leaks due to dorsal column stimulator implantation: Case report.

Radioisotope myelography can be used effectively for the detection of spinal fluid leaks following surgical procedures involving the spine and spinal cord. The advantages of this approach are discussed in relation to currently used techniques and are illustrated by a case report.

Radiometric assay of bacterial growth: analysis of factors determining system performance and optimization of assay technique.

A quantitative technique for the measurement of 14CO2 released from a bacterial culture was evaluated. The technique uses liquid scintillation counting to record 14CO2 accumulation on a fluor-impregnated filter paper within a double-chambered scintillation vial that also houses the bacterial growth medium. We have successfully identified and corrected the major causes for a variably low detection efficiency, and also established the optimum mixture of reagents for the detection system. Incorporation of Triton X-100 into the scintillation fluid used for the detector reduced the variability between identical assays in a single batch from 50% to 5%, and, in conjunction with an increase in the scintillator concentration, raised the counting efficiency from 30% to 70-88%. The response of the improved detector is linear over a wide range of count-rates. Another significant modification was the interchange of growth and detector chambers. Overall, a 40-fold increase in count-rate during the exponential phase of bacterial growth was obtained by improving 14CO2 detection efficiency, increasing the rate of 14CO2 transfer from liquid to gas phases and enlarging the growth supporting capacity of the detector system. The minimum detection time for bacterial growth was shortened and the exponential phase of bacterial proliferation was lengthened by at least 2 hr. High counting efficiency, precision, and linearity make the improved detector a sensitive and reliable tool for radiometry of bacterial growth and metabolism.

A scintigraphic sign for detection of right-to-left shunts.

We evaluated the usefulness of a new scintigraphic sign, a quantum mottling pattern, in diagnosing right-to-left shunt using 99mTc-MAA particles. The quantum mottling pattern is characterized by random distribution of discrete clumps of radioactivity that are more intense than the general body background. Forty-nine 99mTc-MAA scintigrams were analyzed retrospectively for presence of a quantum mottling pattern in extrapulmonary soft tissues and brain. This distinctive pattern was observed in every patient (18/18) in whom a right-to-left shunt was confirmed by nonscintigraphic means and was noted only in one patient in whom independent proof of a right-to-left shunt was not available. In contrast, application of conventional criteria yielded a true-positive interpretation for 15/18 patients with right-to-left shunts and a false-positive interpretation for another four patients. Presence of a quantum mottling pattern on 99mTc-MAA images appears to be a reliable aid for detecting a right-to-left shunt. Use of this sign is likely to improve accuracy of the scintigraphic test in patients with small shunts.

Oblique views in lung perfusion scanning: clinical utility and limitations.

Over 300 perfusion lung scans were reviewed to assess the clinical utility of routinely performed anterior and posterior oblique projections. The characteristics of normal anterior and posterior oblique views were analyzed and compared with lateral projections. The four oblique images contributed materially toward characterization of perfusion defects in 63% of all abnormal studies; the contribution of posterior obliques was 48%, anterior obliques, 15%. For scans displaying at least one focal defect, oblique views were of benefit in over 70% of cases, with posterior obliques accounting for 55%. Oblique views contributed little when perfusion abnormalities involved both lung fields diffusely. The posterior oblique projection was of more value than the anterior oblique because of its ability to clarify lower-lobe abnormalities significantly. A scanning artifact in the posterior oblique views, due to attenuation of the near lung activity by scapula and shoulder-girdle musculature, was seen in 90% of normal studies.

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.

Renal arteriovenous transit times of technetium-radiolabeled chelates.

A noninvasive method was developed for quantitating the distribution of renal arteriovenous transit times of technetium-99m (99mTc) radiopharmaceuticals. Using this method, the characteristic transit times and amplitudes of the first two components of [99mTC] DTPA or MDP transit through the renal vasculature were calculated. The first component amplitude (A1) was evaluated for its ability to discriminate between 20 hypertensive patients with renovascular disease and 21 normotensive subjects. A1 was compared with three other quantitative indices: the ascending slope of the initial renal time-activity curve, the kidney-to-aorta slope ratio (K/A), and renal size. A1 nearly perfectly separated the hypertensive patients from the normotensive subjects; the ability of A1 to discriminate between these two groups is clearly superior to renal size, the initial renal slope, and K/A. We conclude that measurements of the intrarenal distribution of blood flow have distinct advantages over indices of renal blood flow that have been derived from scintillation camera measurements of 99mTc radiopharmaceuticals.

Four- to twenty-four-hour uptake ratio: an index of rapid iodine-131 turnover in hyperthyroidism.

UNLABELLED: Rapid thyroidal iodine turnover may contribute to 131I therapy failure in patients with hyperthyroidism. The utility of a 4- to 24-hr 131I uptake ratio was evaluated as an index of thyroidal iodide retention in hyperthyroid patients. METHODS: In 433 hyperthyroid patients, the success of 131I therapy was correlated with the following factors: gender, pretreatment with antithyroid drugs, clinical diagnosis, magnitude of early and late thyroidal 131I uptake values, and the 4- to 24-hr 131I uptake ratio. RESULTS: Of the 433 patients, 362 patients (84%) had a successful outcome after a single therapeutic dose of 131I while 71 (16%) did not. Multiple linear regression analysis revealed that the highest statistically significant predictor of outcome was the 4- to 24-hr 131I uptake ratio (p-value < 0.001); all other factors showed a weaker association. An 131I uptake ratio of > 1 was found in 67 (15%) patients. Thirty-two of these 67 patients (48%) failed 131I therapy, whereas those patients with uptake ratios of < 1.0, only 39/366 (11%) failed 131I therapy. CONCLUSION: The 4- to 24-hr 131I thyroidal uptake ratio is a practical substitute for exact determination of the effective half-life. It identifies patients who are likely to have a rapid 131I turnover without the need for extended thyroid uptake measurements. An 131I uptake ratio of > or = 1 was found in 15% of hyperthyroid patients and was associated with a near 50% 131I therapy failure rate.

Comparison of 99mTc-methoxyisobutyl isonitrile and 201Tl scintigraphy for detection of residual thyroid cancer after 131I ablative therapy.

UNLABELLED: In this study, we compared 99mTc-methoxyisobutyl isonitrile (MIBI) with 201Tl scintigraphy for the detection of residual thyroid cancer not found by 131I scans in patients with increased risk of recurrence after 131I therapy. METHODS: 201Tl and MIBI scans were obtained in 54 patients with negative 131I scans 3-25 y (median 7.9 y) after the first postsurgical 131I therapy. Serum thyroglobulin (Tg) levels were measured while patients were receiving thyroid hormone and again 6 wk after withdrawal of hormone therapy. RESULTS: The overall results were the same for both 201Tl and MIBI imaging, with a sensitivity of 19 of 36 (53%), specificity of 17 of 17 (100%) and accuracy of 36 of 54 (69%). Planar images missed residual cancer in high cervical lymph nodes adjacent to salivary gland activity, in small nodes (<1 cm) deep in the neck or chest and with diffuse pulmonary micrometastases. Serum Tg was elevated in 24 of 36 (67%) patients with residual cancer; 201Tl detected tumor sites in 13 of 24 (54%) of these patients, and MIBI detected tumor sites in 14 of 24 (58%) of these patients. Of the 12 patients who had residual cancer and false-negative serum Tg levels, 6 had true-positive 201Tl and 5 had true-positive MIBI scans. CONCLUSION: 201Tl and MIBI planar imaging yield the same high specificity and positive predictive value for residual thyroid cancer in patients with high-risk profiles and negative radioiodide scans. Both imaging agents detected residual cancer in more than half of the patients in whom conventional staging techniques did not reliably detect either the presence or the extent of residual thyroid cancer and changed the management in patients with surgically resectable cancer.

Phantom kidney in technetium-99m DTPA studies of renal blood flow: case report.

Renal perfusion, filtration rate, and excretion can be evaluated with technetium-99m diethylenetriamine pentaactate (Tc-DTPA) using immediate and delayed imaging. Two cases are presented in which the immediate images reveal a bilateral distribution of radiotracer characteristic of bilateral renal perfusion, but the delayed images showed no evidence of filtration or excretion on one side. There was congenital absence of the kidney on that side in one case and surgical absence in the other. The apparent renal perfusion on the side of the absent kidney was probably attributable to perfusion of small bowel occupying the renal fossa.

An improved method for the quantification of left-to-right cardiac shunts.

We have investigated a technique for quantifying QP/QS in left-to-right cardiac shunts. In this method, the gamma variate, which is fitted to the first-pass portion of the lung curve, is used to generate a curve, which simulates the response of a normal lung curve with systemic recirculation. The difference between this curve and the observed lung curve is then used to calculate QP/QS. This method was evaluated on a set of simulated lung time-activity curves with precisely known QP/QS values on a group of 11 patients with no clinical suspicion of cardiac shunt and on a group of 30 patients referred for cardiac shunt studies. The QP/QS in each of these studies was determined by three individuals using both the Maltz-Treves method and the new method. This method yielded QP/QS values that were more accurate on the simulated lung data and had less interobserver variation on all the studies than those obtained from the Maltz-Treves method.

New methods of examining gamma camera collimators.

New methods are proposed and described to examine the quality of gamma camera collimators in two special performance categories, namely, uniformity in regional efficiency and regional variations in channel tilt. These two performances are critical areas for SPECT imaging. Results obtained from experimental and commercial collimators illustrate the variability seen for these performance characteristics in currently available collimators.

Biological distribution and excretion of DTPA labeled with Tc-99m and In-111.

For the purpose of radiation dose estimates, organ assays and excretion measurements of the Tc-99m and In-111 complexes with DTPA were conducted in dogs at various time intervals up to 24 hr, and the results compared with available human data. The peak concentration of the Tc-99m complex, at 3 min after injection, was 5% of the administered dose for one kidney, 3.5% for the liver, and 3.5% for the small bowel. No organ system except the urinary tract reached a concentration higher than that in blood for several hours after the injection. The biliary excretion of these agents was extremely low, and their elimination in the feces was negligible. In man, it appears that the residual 4-5% of an administered dose not eliminated in the urine by 24 hr is widely distributed in various tissues. The distribution of the In-111 complex is similar but not identical to that of the Tc-99m complex.

Influence of baseline ejection fraction and success of thrombolysis on mortality and ventricular function after acute myocardial infarction.

The efficacy of streptokinase (STK) thrombolytic therapy was prospectively evaluated in 77 consecutive patients presenting within 9 hours of onset of acute myocardial infarction. Serial left ventricular (LV) ejection fraction (EF) was assessed by radionuclide ventriculography, initially (acute) and at 1 month (late). The role of initial LVEF was examined by comparing patients with an acute LVEF greater than or equal to 50% (type I) with those with LVEF less than 50% (type II). Sixty-five patients (84%) had total coronary occlusion and received STK. Initial successful reperfusion was achieved in 34 patients (52%), but repeat angiograms at 10 to 14 days revealed persistent patency in only 27 patients. Within the type I and type II classification, 2 patient subgroups were compared: Group A had successful and persistent thrombolysis and group B had initial failure of thrombolysis or in-hospital reocclusion. There was no significant change in global LVEF in any group from acute to 1 month follow-up: group IA--acute EF = 56 +/- 2% (mean +/- standard error of the mean), late EF = 55 +/- 2% (p = not significant [NS]); group IB--acute EF = 58 +/- 1%, late EF = 55 +/- 2% (NS); group IIA--acute EF = 35 +/- 2%, late EF = 4 +/- 4%, (NS); group II B--acute EF = 36 +/- 2%, late EF = 41 +/- 3% (NS). No patient with an acute EF greater than or equal to 50% died, i.e., group IA patients (n = 7) or group IB patients (n = 13).(ABSTRACT TRUNCATED AT 250 WORDS)

Renal transplant evaluation.

Radionuclide scintigraphy of the renal transplant has assumed an important role in disclosing the complications that beset this life-prolonging procedure. Renal ischemia, whether caused by mechanical obstruction of the blood vessels or ureter or immunological rejection, can be detected by qualitative and quantitative perfusion studies using 99mTc-complexes such as pertechnetate, glucoheptonate and DTPA. Similarly, parenchymal agents such as radiohippurate and 99mTc-DTPA can be quantitated for uptake and their drainage patterns monitored to reveal possible underlying obstructive uropathy and urine extravasation. The literature is replete with mathematical strategems for quantitating perfusion and parenchymal transit of the tracers, but none are truly specific enough to be diagnostic of a given cause of renal ischemia. Serial quantitative radionuclide studies should be obtained during the first 2-3 wk after transplantation with the view of noting an improvement or deterioration of the quantitation parameters as a guage of progress. A deterioration may anticipate biochemical manifestations by 24-48 hr, but it is not specific and must be interpreted in light of the clinical circumstances or necessitate invasive procedures for a definitive diagnosis.

Positron emission tomography for the evaluation of pancreatic disease.

Efficient techniques for native-labeling of amino acids have been combined successfully with emission tomography to yield significant improvements in pancreatic imaging. Carbon-11-labeled tryptophan appears to be the best agent available currently for imaging the pancreas. Optimum scanning times begin 30 min after tracer administration. Positron emission tomography with 11C-tryptophan is capable of defining both morphological and functional alterations in the pancreas. Tumors as small as 2 cm in diameter can be detected, but reliable differentiation of pancreatic cancer from pancreatis may not be possible even with this improved imaging technique. Longitudinal multiplane emission tomography in single-photon mode with the Pho/Con provides an efficient and satisfactory approach to pancreatic imaging with the positron-emitting radiopharmaceuticals.

Transient unilateral hypoperfusion of the lung following mediastinoscopy.

Two cases of pulmonary hypoperfusion occurring after mediastinoscopic examination were demonstrated on lung scans. In one case, this finding on the ninth day required a pulmonary angiographic study that yielded normal findings. Repeat lung scans were normal. We propose that localized mediastinal edema or bleeding after mediastinoscopic examination can produce defects of hypoperfusion, and we urge caution in the interpretation of lung scans up to nine days after mediastinoscopic examination.

Guided biopsies of abnormalities on nuclear bone scans. Technique and indications.

A guided biopsy technique has been developed for evaluation of solitary bone abnormalities, identified by gallium 67 or technetium 99 bone scans, in patients with normal or ambiguous x-ray findings. Continuous gamma camera monitoring is used to guide staining of the bone abnormality and overlying tissues with methylene blue. This staining is followed by open biopsy of the marked bone. This technique was utilized in 15 patients, 12 of whom had bronchogenic carcinoma. The most commonly involved bones (13/15) were ribs. None of the patients had an identifiable, gross abnormality at operation, and the marked area was indistinguishable from neighboring tissues. Diagnostic tissue was obtained by each biopsy and there were no complications associated with this technique. The primary applicability of this technique is for both pretreatment and re-treatment staging of bronchogenic carcinoma in patients who have ambiguous nuclear bone scan abnormalities.

Bronchogenic carcinoma located in the aortic window. The importance of the primary lesion as a determinant of survival.

Thirty-four patients with an aortic window lesion were carefully staged with gallium scans and mediastinoscopy according to the TNM classification system for carcinoma of the lung. All were in Stage III. Twenty-five patients had non-oat cell carcinomas (15 squamous cell, eight adeno-, two large cell) and nine had oat cell carcinomas. Quantitative ventilation-perfusion lung scans were particularly helpful in verifying the subaortic location of the tumor by showing a less than 20% interference with pulmonary blood flow or ventilation secondary to left mainstem bronchus or pulmonary artery invasion. Decision for resectability in 13 Stage III M0 patients was based on the length of the uninvolved proximal left main pulmonary artery seen on pulmonary arteriogram. Eight patients (seven non-oat cell and one oat cell) had resection after radiation and prior to chemotherapy (after two cycles of chemotherapy and prior to radiation therapy for the oat cell) with a resultant survival rate better than those of M0 and M1 non-oat cell or oat cell patients without resection. The survival rates of nine non-oat cell M0 patients, nine non-oat cell M1 patients, and eight oat cell patients, all without resection, were not statistically different. This similarity in survival rates is explained by the observation that 38% of the non-oat cell M1, 71% of the non-oat cell M0, and 63% of the oat cell patients died from complications of their primary tumor. Patients with aortic window lesions, irrespective of their histology, have an extremely poor prognosis due to the high incidence of lethal complications of their primary tumor. Complete resection when feasible, as judged by pulmonary arteriography, provides the best control of the primary tumor and, as a consequence, gives longer survival.