Scintigraphic detection of post-pneumonectomy bronchopleural fistulae.

A total of 20 ventilation studies [16 with xenon-133 and four with technetium-99m diethylenetriamine pentaacetic acid (DTPA)] were performed in 11 patients with suspected post-pneumonectomy bronchopleural fistulae. The findings on the ventilation scan were correlated with bronchoscopy, taken as the gold standard for purposes of comparison. The sensitivity and specificity for 133Xe scans were 83% and 100% respectively, while the sensitivity for 99mTc-DTPA aerosol studies was poor at 0%. Special techniques for optimal visualization of the fistulae are enumerated.

Cerebral perfusion and vascular reserve in fibromuscular dysplasia of the internal carotid artery.

We report of a case of abnormal cerebral perfusion but normal vascular reserve by single-photon emission computed tomographic imaging in a 65-year-old woman with fibromuscular dysplasia of the internal carotid artery (ICA). The patient had an aneurysm in her left ICA at the level of second cervical vertebra without evidence of stenosis and was excised with primary anastomosis 3 years ago when she presented with months of dizziness. But follow-up angiography showed high-grade long segmental stenosis in her left ICA, characteristic of fibromuscular dysplasia. Because she was asymptomatic with normal vascular reserve, she was treated medically. This report suggests the usefulness of functional imaging in fibromuscular dysplasia. The potential improvement of cerebral perfusion in this rare disease with acetazolamide or dipyridamole is worthy of further clinical investigation.

Comparison of double-phase 99mTc-sestamibi with 123I-99mTc-sestamibi subtraction SPECT in hyperparathyroidism.

OBJECTIVE: Our purpose was to compare double-phase 99mTc-sestamibi single-photon emission computed tomography (SPECT) and simultaneous 123I-99mTc-sestamibi subtraction SPECT for preoperative localization of hyperfunctioning parathyroid tissue in patients with primary hyperparathyroidism. SUBJECTS AND METHODS: Fifteen patients with primary hyperparathyroidism underwent preoperative double-phase 99mTc-sestamibi SPECT and simultaneous 123I-99mTc-sestamibi subtraction SPECT imaging. At surgery, the location, weight, and histopathologic evaluation of all identified parathyroid glands were recorded. RESULTS: At surgery, 17 parathyroid adenomas and 37 normal parathyroid glands were identified. The sensitivity, specificity, and diagnostic accuracy for the detection of parathyroid adenomas were 88%, 97%, and 94%, respectively, for simultaneous 123I-99mTc-sestamibi subtraction SPECT and 53%, 86%, and 76%, respectively, for double-phase 99mTc-sestamibi SPECT. The differences in sensitivity and diagnostic accuracy were statistically significant (p = .031 and p = .016, respectively). CONCLUSION: Compared with double-phase 99mTc-sestamibi SPECT, simultaneous 123I-99mTc-sestamibi subtraction SPECT is a superior imaging study for the preoperative localization of hyperfunctioning parathyroid tissue.

Incremental value of rubidium-82 positron emission tomography for prognostic assessment of known or suspected coronary artery disease.

Myocardial perfusion imaging using positron emission tomography (PET) may be more accurate for the diagnosis of coronary artery disease (CAD) than conventional imaging. The purpose of this study was to evaluate the prognostic implications of perfusion abnormalities in 685 patients (age 62 +/- 11 years, 199 women) studied by PET, and to assess the incremental value of these data in relation to prognostic implications of clinical and angiographic findings. Rubidium (Rb)-82 PET was performed before and after dipyridamole stress. Transient defects were detected in 227 patients (33%), and were moderate or greater in severity (> 15% of the left ventricle) in 84 (12%). Resting defects were present in 435 (64%) and were moderate or greater in severity in 216 (32%). The total extent of abnormally perfused myocardium was small (< 15% of the left ventricle) in 198 (29%), moderate in 216 (32%), and extensive in 105 (15%). Clinic review or standardized phone interview in 657 patients (96%) identified 151 cardiac events, including 81 cardiac deaths, 16 patients with myocardial infarction, 7 with unstable angina, and 47 with late revascularization (> 3 months after PET). Normal scans had a 90% event-free survival, compared with 87% in patients with small, 75% with moderate, and 76% with extensive defects (log rank chi-square 30, p <0.0001). Functional class, extent of CAD, and the presence and extent of perfusion defects (both at rest and during stress) were independent predictors of cardiac death and total cardiac events. In sequential Cox proportional-hazards models, the results of PET were incremental to those of clinical and angiographic evaluation. Thus, the presence and extent of damaged and jeopardized myocardium are independent and incremental predictors of outcome in patients undergoing Rb-82 PET.

Viable neurons with luxury perfusion in hydrocephalus.

A woman with hydrocephalus due to aqueductal stenosis had functional imaging of cerebral perfusion and metabolism to demonstrate the effects of endoscopic third ventriculostomy--a new form of internal surgical shunting. Technetium-99m-ECD SPECT and 18F-FDG PET showed regional luxury perfusion at the left frontal region. Three months after a successful third ventriculostomy, a repeated imaging of cerebral perfusion and metabolism showed resolution of luxury perfusion and global improvement of both perfusion and metabolism. This concurred with postoperative clinical improvement. The paired imaging of cerebral perfusion and metabolism provides more information than just imaging perfusion or metabolism. Thus, the detection of perfusion and metabolism mismatch may open a new window of opportunity for surgical intervention.

Preliminary experience with double-phase SPECT using Tc-99m sestamibi in patients with hyperparathyroidism.

BACKGROUND: There is a continual search for a better imaging modality for parathyroid pathology. In recent years, Tc-99m sestamibi has been proposed as an alternative to T1-201 for parathyroid scintigraphy. The purpose of this study is to assess the usefulness of a double-phase Tc-99m sestamibi SPECT technique for parathyroid imaging. METHODS: Sixty-one consecutive patients with hyperparathyroidism were studied. Sixteen had previously undergone unsuccessful surgery for hyperparathyroidism. SPECT imaging of the neck and chest was performed at 15 minutes and again at 2 hours after 20-25 mCi of Tc-99m sestamibi was given intravenously. A positive scan was defined as a region of increased focal uptake that persisted on the delayed images. RESULTS: When compared with surgical findings, double-phase sestamibi SPECT correctly identified 55% (26/ 47) of the parathyroid adenomas in the previously unoperated group, and 91% (10/11) of the parathyroid adenomas in the reoperative group. Double-phase sestamibi SPECT was negative in 92% (109/118) of the normal parathyroid glands in the previously unoperated group, and in 88% (15/17) in the reoperative group. CONCLUSIONS: These preliminary data suggest that double-phase Tc-99m sestamibi SPECT is a promising procedure for the preoperative detection and localization of hyperfunctioning parathyroid tissue, especially in patients with recurrent or persistent postoperative hyperparathyroidism.

Myocardial viability studies using fluorine-18-FDG SPECT: a comparison with fluorine-18-FDG PET.

UNLABELLED: Multidetector SPECT systems equipped with a high-energy, or 511-keV collimator, have been proposed to offer a less expensive alternative to PET in myocardial viability studies with [18F]FDG. The objectives of this investigation included: (a) measuring the physical imaging characteristics of SPECT systems equipped with either a high-energy general-purpose collimator (HE), or the dedicated 511-keV collimator (UH), when imaging 511-keV photons, and comparing them with conventional FDG PET; and (b) directly and quantitatively comparing the diagnostic accuracy of SPECT, with either an UH or HE collimator, to that of PET in myocardial viability studies using 18F-FDG. METHODS: Physical imaging characteristics of SPECT and PET were measured and compared. Both SPECT and PET studies were performed in two groups of 18 patients each, with Group I using HE SPECT and Group II using UH SPECT. Myocardial perfusion studies were also performed using 82Rb PET at rest and during dipyridamole stress to identify areas of persistent hypoperfusion. For each myocardial region with a persistent perfusion defect, a perfusion-metabolism match or mismatch pattern was established independently, based on the results of 18F-FDG SPECT as well as PET. RESULTS: PET is superior to SPECT in all physical imaging characteristics, particularly in sensitivity and contrast resolution. PET had a sensitivity 40-80 times higher than that of SPECT, and its contrast resolution was 40-100% better than SPECT. Between FDG-SPECT using an HE collimator and that using a 511-keV collimator, the latter showed marked reduction in septal penetration (from 56% to 38%), improvement in spatial resolution (from 17 mm to 11 mm FWHM) as well as contrast resolution (from 34% to 45%), while suffering reduced system sensitivity (from 75 to 34 cpm/microCi). Patient studies demonstrated that although FDG-SPECT, using a HE or UH collimator, provided concordant viability information as FDG PET in a large majority of myocardial segments with persistent perfusion defects (88% and 90%, respectively), there is an excellent statistical agreement (kappa = 0.736) between SPECT with UH collimator and PET, while the agreement between SPECT using HE collimator and PET are moderate (kappa = 0.413). CONCLUSION: Despite its markedly inferior physical imaging characteristics compared with PET, SPECT with the dedicated 511-keV collimator offers a low-cost, practical alternative to PET in studying myocardial viability using [18F]FDG. SPECT systems with a high-energy, general-purpose collimator, on the other hand, are inadequate in such studies.

A rapid chromatographic method for quality control of technetium-99m-bicisate.

UNLABELLED: The purpose of this work was to develop a simple and rapid method to determine the radiochemical purity of 99mTc-bicisate. METHODS: A rapid paper chromatographic (PC) method was developed to determine the radiochemical purity of 99mTc-bicisate and compare the results with those of the manufacturer's recommended method. The present PC method included Whatman 3MM paper as the solid phase and ethyl acetate as the solvent. RESULTS: The time for chromatography by this technique was 4-5 min compared to about 23 min by the manufacturer's method. The Rf value of 99mTc-bicisate (Rf = 0.9-1.0) was widely different from those of 99mTcO4- and reduced 99mTc (Rf = 0.0 for both) so the chromatographic strip after development could be readily cut into two segments, in order to determine the labeling yield. CONCLUSION: No significant difference in labeling yields was found between the present method and the manufacturer's method. The PC method using Whatman 3MM paper and ethyl acetate is a simple and fast technique to determine the radiochemical purity of 99mTc-bicisate and may be substituted for the manufacturer's recommended method to save time.

Regional body FDG-PET in postoperative recurrent hyperparathyroidism.

PURPOSE: The use of preoperative imaging studies in patients with persistent or recurrent hyperparathyroidism after initial operation is generally accepted to improve the success rate and minimize the morbidity from reoperative surgery. The purpose of this study was to define the performance of FDG-PET for the localization of hyperfunctioning parathyroid tissue prior to reoperation. METHOD: Twenty patients with biochemical evidence of recurrent or persistent hyperparathyroidism following previous neck surgery were investigated. Regional body PET imaging of the neck and upper chest (axial field of view 27.5 cm) was acquired 45 min after 5-10 mCi FDG was given intravenously. RESULTS: Subsequent surgery revealed solitary parathyroid adenomas in 14 patients, seven hyperplastic glands in 2 patients, and parathyroid carcinoma in 1 patients. FDG-PET correctly identified 79% (11/14) of the parathyroid adenomas, 29% (2/7) of the hyperplastic glands, and the parathyroid carcinoma. FDG-PET was negative in 79% (30/38) of the surgically identified normal parathyroid glands. Eight false-positive findings led to a positive predictive value of 64%. CONCLUSION: These preliminary data suggest that regional body FDG-PET is a promising procedure in the evaluation of patients with persistent or recurrent postoperative hyperparathyroidism.

Comparison of FDG-PET and sestamibi-SPECT in primary hyperparathyroidism.

UNLABELLED: Preoperative localization of hyperfunctioning parathyroid tissue in patients with primary hyperparathyroidism has been a longstanding diagnostic challenge. This study directly compared FDG-PET and sestamibi-SPECT for preoperative detection of abnormal parathyroid tissue. METHODS: Twenty-one consecutive patients with primary hyperparathyroidism were studied prospectively before surgical neck exploration. SPECT of the neck and chest was performed at 15 min and 2 hr after intravenous 99mTc-sestamibi. Regional body PET was performed 45 min after intravenous FDG. RESULTS: Surgery revealed 19 solitary parathyroid adenomas, 2 parathyroid adenomas in one patient; and 3 hyperplastic parathyroid glands in one patient, and 51 normal parathyroid glands. The diagnostic sensitivities for detection of parathyroid adenomas of 43% (9 of 21) for dual-phase sestamibi-SPECT and 86% (18 of 21) for FDG-PET were significantly different (p < 0.001). The difference in diagnostic specificities of 78% (40 of 51) for FDG-PET and 90% (46 of 51) for dual-phase sestamibi-SPECT approached statistical significance (p = 0.063). CONCLUSION: This study demonstrates that FDG-PET is more sensitive than sestamibi-SPECT in the preoperative localization of parathyroid adenomas in patients with primary hyperparathyroidism.

Is image subtraction necessary in the clinical interpretation of single-day split-dose stress cerebral perfusion single-photon emission tomography using technetium-99m compounds?

The aim of this study was to validate a simplified semiquantitative method of evaluating a single-day stress cerebral perfusion test to obtain cerebrovascular reserve capacity (CVRC) for routine clinical uses. A split-dose protocol was tested in 36 pairs of technetium-99m hexamethylpropylene amino oxime baseline (low dose) and acetazolamide (high dose) stress brain single-photon emission tomographic (SPET) studies from 16 patients with cerebrovascular disease. The images were displayed on a semiquantitative color scale with (corrected) and without (uncorrected) image subtraction, dose adjustment, and decay correction. The representative CVRC was determined by placing 3x3 pixel regions of interest on midthalamic and midcerebellar slices. The corrected and uncorrected relative changes in CVRC were correlated using linear regression. The relative changes of corrected (x) and uncorrected (y) CVRC by quantitative analysis were highly correlated in a linear fashion (y=0.67x+0.002, r=0.998, P<0.0005). As predicted by theory, the slope was related to the ratio of split dose and independent of ROI sampling. Single-day split-dose stress brain SPET can be accurately performed without image subtraction and complicated dose adjustment or decay correction for clinical studies.

Present assessment of myocardial viability by nuclear imaging.

Prospective delineation of viable from nonviable myocardium in patients with coronary artery disease in an important factor in deciding whether a patient should be revascularized or treated medically. Two common techniques--single-photon emission computed tomography (SPECT) and positron-emission computed tomography (PET)--are used in nuclear medicine using various radiopharmaceuticals for the detection of myocardial viability in patients. Thallium-201 (201Tl) and technetium-99m (99mTc)-sestamibi are the common radiopharmaceuticals used in different protocols using SPECT, whereas fluoride-18 (18F)-fluorodeoxyglucose (FDG) and rubidium-82 (82Rb) are most widely used in PET. The SPECT protocols involve stress/redistribution, stress/redistribution/reinjection, and rest/redistribution imaging techniques. Many studies have compared the results of 201Tl and (99mTc)-sestamibi SPECT with those of FDG PET; in some studies, concordant results have been found between delayed thallium and FDG results, indicating that 201Tl, although considered a perfusion agent, shows myocardial viability. Discordant results in a number of studies have been found between sestamibi and FDG, suggesting that the efficacy of sestamibi as a viability marker has yet to be established. Radiolabeled fatty acids such as iodine-123 (123I)-para-iodophenylpentadecanoic acid and carbon-11 (11C)-palmitic acid have been used for the assessment of myocardial viability with limited success. 11C-labeled acetate is a good marker of oxidative metabolism in the heart and has been used to predict the reversibility of wall motion abnormalities. (18F)-FDG is considered the marker of choice for myocardial viability, although variable results are obtained under different physiological conditions. Detection of myocardial viability can be greatly improved by developing new equipment and radiopharmaceuticals of better quality.

Measurement of cardiac output with first-pass determination during rubidium-82 PET myocardial perfusion imaging.

In addition to providing useful clinical information, cardiac output determined during rubidium-82 positron emission tomographic (PET) myocardial perfusion studies can be used in the measurement of absolute regional myocardial blood flow using Sapirstein's method. This investigation was conducted to compare cardiac output values obtained by post-processing data acquired in a list mode PET myocardial perfusion study with those obtained using a technetium-99m-labeled red blood cell method on the same patients. Results from 14 patients showed that cardiac output can be accurately measured simultaneously in a 82Rb PET myocardial study, allowing determination of multiple perfusion and functional parameters of the heart, thus improving the cost-effectiveness of the 82Rb PET study.

Outcome of temporal lobe epilepsy surgery predicted by statistical parametric PET imaging.

UNLABELLED: PET is useful in the presurgical evaluation of temporal lobe epilepsy. The purpose of this retrospective study is to assess the clinical use of statistical parametric imaging in predicting surgical outcome. METHODS: Interictal 18FDG-PET scans in 17 patients with surgically-treated temporal lobe epilepsy (Group A-13 seizure-free, group B = 4 not seizure-free at 6 mo) were transformed into statistical parametric imaging, with each pixel representing a z-score value by using the mean and s.d. of count distribution in each individual patient, for both visual and quantitative analysis. RESULTS: Mean z-scores were significantly more negative in anterolateral (AL) and mesial (M) regions on the operated side than the nonoperated side in group A (AL: p < 0.00005, M: p = 0.0097), but not in group B (AL: p = 0.46, M: p = 0.08). Statistical parametric imaging correctly lateralized 16 out of 17 patients. Only the AL region, however, was significant in predicting surgical outcome (F = 29.03, p < 0.00005). Using a cut-off z-score value of -1.5, statistical parametric imaging correctly classified 92% of temporal lobes from group A and 88% of those from Group B. CONCLUSION: The preliminary results indicate that statistical parametric imaging provides both clinically useful information for lateralization in temporal lobe epilepsy and a reliable predictive indicator of clinical outcome following surgical treatment.

The incidence of scintigraphically viable and nonviable tissue by rubidium-82 and fluorine-18-fluorodeoxyglucose positron emission tomographic imaging in patients with prior infarction and left ventricular dysfunction.

BACKGROUND: Although reversible perfusion defects, perfusion-metabolism mismatch and match patterns are important for differentiating viable from nonviable myocardium, the frequency of these scintigraphic patterns has not been reported. The study objective was to establish the incidence of these scintigraphic patterns to estimate the clinical need for metabolic positron emission tomography for evaluating tissue viability in patients with prior myocardial infarction (MI). METHODS AND RESULTS: 82Rb perfusion images were interpreted to identify reversible or irreversible defects, followed by determination of their 18F-fluorodeoxyglucose (18F-FDG) uptake pattern. In 155 patients with prior MI, analysis of 613 abnormal segments showed reversible perfusion defects in 13%. The 87% irreversible defects, 18% showed perfusion-metabolism mismatch, whereas 69% showed the match pattern. Reversible perfusion defects and perfusion-metabolism mismatches were noted in 20% (31/155) and 29% (45/155) of patients, respectively, whereas the match pattern was noted in 51% (79/155) of patients. CONCLUSION: Irreversible perfusion defects were common in our patients with prior MI, and distinction between viable and nonviable tissue was not possible by perfusion imaging alone. The identification of hibernating myocardium was possible only with the additional 18F-FDG imaging in about one third of patients. This indicates a significant clinical demand for 18F-FDG imaging that identifies patients who will benefit from revascularization.

Malignant pheochromocytoma of the anterior mediastinum: PET findings with [18F]FDG and 82Rb.

A case of a malignant pheochromocytoma arising from the anterior mediastinum is presented. We report the use of positron emission tomography with 82Rb and [18F]fluorodeoxyglucose to successfully image this neoplasm.

Use of positron emission tomography for prediction of perioperative and late cardiac events before vascular surgery.

The efficacy of myocardial perfusion imaging for cardiac-risk stratification of patients undergoing vascular surgery has been disputed recently. In comparison with conventional techniques, positron emission tomography (PET) has the benefit of permitting a true resting scan, allows accurate measurement of the extent of ischemia, and is highly specific for the diagnosis of coronary disease. We therefore investigated the use of PET for risk stratification at the time of vascular surgery and subsequent follow-up in 78 patients (aged 67 +/- 11 years, 52 men), selected for testing before the performance of extensive surgery or because of one or more clinical risk factors. Perfusion images were obtained by using a standard rubidium 82 protocol before and after dipyridamole-handgrip stress. With use of a quantitative color scale in a 24-segment model of the left ventricle, scans were reported as showing normal perfusion, resting defects, or stress-induced defects (deterioration > 15% with stress). After exclusion of 6 patients referred for myocardial revascularization, 72 patients were followed up in the perioperative period and for 18 +/- 12 months for late cardiac death, myocardial infarction, or unstable angina. Perioperative events occurred in 14 patients (5 with myocardial infarction and 9 with unstable angina), 10 of whom had ischemia at PET (sensitivity, 71%; predictive value of a positive test, 45%). Isolated resting perfusion defects were not associated with events. The presence of extensive ischemia (more than five segments) had a positive predictive value of 64%, and its absence gave a negative predictive value of 89%.(ABSTRACT TRUNCATED AT 250 WORDS)

Hibernating myocardium versus scar: severity of irreversible decreased myocardial perfusion in prediction of tissue viability.

PURPOSE: To determine whether quantitation of the relative severity of decreased perfusion in irreversible defects on myocardial perfusion images enables differentiation of viable hibernating myocardium from scar. MATERIALS AND METHODS: In 145 patients with previous myocardial infarction, 1,252 regions with irreversible defects proved by means of rubidium-82 rest-stress imaging were analyzed for relative severity (percentage decrease in perfusion). Myocardial tissue viability was determined by means of positron emission tomography with fluorine-18 fluorodeoxyglucose (FDG). RESULTS: The relative decreases in Rb-82 uptake in the 1,252 regions were categorized into nine levels of severity (30% to > or = 70%) in 381 regions of hibernating myocardium and 871 regions of scar. The values of relative decreased perfusion in the irreversible defects alone did not enable differentiation of hibernating myocardium and scar (P = .61). CONCLUSION: The results show no relationship between the relative severity of irreversible perfusion defects and the ability to distinguish between hibernating myocardium and scar.