PURPOSE:To report a method for determining absolute percentage change in cerebral blood flow (measurement of cerebrovascular reserve) before and after acetylazolamide (Diamox) administration in children with sickle cell anemia.MATERIALS AND METHODS:Thirty-six symptomatic sickle cell disease patients (48 studies) were evaluated. After the injection of either Tc-99m bicisate ethyl cysteinate dimer (ECD) or hexamethyl propylene amine oxime (HMPAO), both whole body scans (with geometric mean correction) and single photon emission computed tomography (CT) were performed pre- and post-Diamox administration with calculation of percentage brain uptake on the whole body images for both examinations and determination of cerebrovascular reserve (percentage change in brain uptake post-Diamox). Evaluation for regional cerebral perfusion change was also performed.RESULTS:The cerebrovascular reserve measurement was 17.6% +/- 43.5% (mean +/- 1 SD). Thirty-three of 48 studies (69%) showed an abnormal cerebrovascular reserve, while only 6 of 48 studies (12.5%) showed Diamox-induced regional perfusion changes in the brain. No statistically significant relationship was found between the occurrence of a regional perfusion abnormality versus loss of cerebrovascular reserve (P = 0.75, Fisher exact test), suggesting that these are independent variables. The cerebrovascular reserve was reproducible, with an average standard deviation of +/-0.54%.CONCLUSION:A new, simple method for calculation of cerebrovascular reserve is presented; this method is reproducible and appears to be an independent variable in the evaluation of cerebrovascular status in sickle cell anemia patients. It should allow further characterization of this complex patient population, and possibly assist in detection of patients at risk for developing "silent" or overt stroke.

The long term objective of this work is to design and build a compact and mobile PET system for bedside cardiac imaging. For patients under intensive care with severe left heart failure, FDG PET studies are crucial for the decision between emergency bypass surgery versus heart transplantation, but often these patients are too ill to be transported to an outpatient PET center. Our goal is to design a PET system that can be transported within a hospital for imaging in environments such as an intensive care unit (ICU) as well as an operating room or interventional suite. In this paper we investigate by simulation the effect of limited angle acquisition on the quality of reconstructed images for a given compact detector design and imaging geometry. We present results of a simulated phantom study that show the effect of changing the number of detector positions, the distance between the detectors and the angles of acquisition.

Biliary diversion procedures are performed during gastric surgery to decrease bile reflux. A 1-day dual-radionuclide examination was studied to determine its potential in the evaluation of the effectiveness of the Braun enteroenterostomy in reducing bile reflux and its effects on gastric emptying. Orally ingested gallium 67-labeled egg and intravenously administered technetium 99m diisopropyl-imino-diacetic acid were imaged simultaneously. This provided a way to depict both bile reflux and gastric emptying on the same day in patients who underwent gastric surgery. Overall, the Braun enteroenterostomy trades bile reflux, a symptomatic and premalignant disease, for gastroparesis, a less severe and often treatable disease.

STUDY OBJECTIVES:To determine whether 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) single-photon emission CT (SPECT) is useful in characterizing pulmonary masses. DESIGN:Scans were prospectively acquired and interpreted. Interpretations were performed with CT or chest radiograph but interpreters were blinded to eventual diagnosis. SETTING:University hospital practice and affiliated Veterans Administration medical center. PATIENTS OR PARTICIPANTS:Forty patients participated as part of an institutional review board-approved research protocol, and informed consent was obtained in all. Eight additional patient scans were acquired as part of their clinical evaluation for pulmonary mass. MEASUREMENTS AND RESULTS:There were 26 malignant lesions (12 were 1 to 2 cm in size, the rest were larger) and 17 benign lesions (3 were < 1 cm in size, 9 were 1 to 2 cm in size, and 5 were larger). Averaged sensitivity, specificity, positive predictive value, and negative predictive value were, respectively, 50% (12 of 24), 94% (17 of 18), 92% (12 of 13), and 59% (17 of 29) for lesions 1 to 2 cm in size, 100% (28 of 28), 90% (9 of 10), 97% (28 of 29), and 100% (9 of 9) for lesions > 2 cm in size. There was good correlation between readers (p < 0.0001). CONCLUSION:FDG SPECT is useful in characterizing pulmonary masses > 2 cm in size and appears to be equivalent to positron emission tomography for these lesions. Although currently clinically suboptimal for characterizing lesions < or = 2 cm in size, FDG SPECT appears to be better than current anatomic imaging methods. In addition, the positive predictive value of FDG SPECT for small lesions is also high (92%), and this technique appears potentially useful in the subset of patients in whom a positive result would alter clinical diagnostic pathways or care.

Thallium-201 chloride (201Tl) single-photon emission computed tomography (SPECT) detects a high percentage of histologically and anatomically diverse pediatric brain tumors. Thallium-201 chloride SPECT and F-18 fluoro-deoxy-glucose (18F-FDG) positron emission tomography (PET) are the most commonly used radionuclide techniques in neuro-oncology. Having developed a methodology to image 18F-FDG with SPECT, the authors performed SPECT scans coupled with magnetic resonance imaging to assess the comparative sensitivity of 201Tl and 18F-FDG in 19 children with brain tumors. Tumors were detected using 201Tl SPECT in 14 of 19 patients. Five of five postoperative residual tumors were detected by 201Tl SPECT, and six of seven after irradiation recurrences were detected. F-18 fluoro-deoxy-glucose SPECT detected tumors in only three of 19 patients, all of whom had abnormal 201Tl studies (all three after therapy recurrences). Thallium-201 chloride SPECT could be interpreted in 18 of 19 patients without magnetic resonance imaging confirmation, but none of the 19 18F-FDG SPECT studies could be interpreted without magnetic resonance imaging. Thallium-201 chloride SPECT is more sensitive than 18F-FDG SPECT in the detection of primary or recurrent childhood brain tumors. The failure of 18F-FDG SPECT in follow-up after therapy is primarily a problem of limited fluoro-deoxy-glucose uptake, not spatial resolution. Thallium-201 chloride SPECT is a promising imaging modality in neuro-oncology.

Several radionuclide imaging agents have been used for assessing the presence of myocardial viability. These include Tl-201 chloride, Tc-99m sestamibi, and Tc-99m teboroxime. Currently, the most reliable indicator is F-18 FDG, which accumulates in severely hypoperfused myocardium, indicating preserved metabolic activity. The presence of chronically ischemic myocardium that has preserved metabolic activity is referred to as "hibernating" myocardium. In this series, the ability of Tl-201, sestamibi, and teboroxime to establish the existence of viable myocardium was compared with that of F-18 FDG. Seventy-seven patients with ischemic cardiomyopathy were referred for determination of myocardial viability. FDG images were compared with representative resting blood-flow images obtained from either: 1) 24 hour Tl-201 reinjection-redistribution images, 2) resting sestamibi blood-flow images, or 3) early images from resting teboroxime washout analysis. Tl-201 was found to underestimate myocardial viability in 41% of patients, Tc-99m sestamibi underestimated viability in 38% of patients, and Tc-99m teboroxime underestimated viability in 26% of patients. There was no significant difference in the prediction of viable myocardium among the three radiopharmaceuticals, as all three underestimated myocardial viability.

Abnormal cerebral venous drainage is associated with hypoxia and glucose deprivation, which can account for progressive neurologic deterioration in Sturge-Weber syndrome. Although developmental delay is common in Sturge-Weber syndrome, bihemispheric calcification is uncommon. Computed tomography (CT) and magnetic resonance imaging (MRI) were used to study the neuroanatomy, while single photon emission computed tomography (SPECT) was used concurrently to evaluate perfusion and glucose metabolism using 99mTc hexamethylpropyleneamine oxime (HMPAO) and [18F] fluorodeoxyglucose (FDG), respectively. Ten patients (10 to 22 years of age) with previously diagnosed Sturge-Weber syndrome, port-wine nevi, and clinical evidence of seizures or stroke-like episodes were studied. Five children with onset of seizures in the first year of life had overall clinical severity comparable to that of children with later-onset seizures. Calcification was present in both hemispheres in one patient; six additional patients had other radiologic evidence of bihemispheric disease; SPECT studies detected bihemispheric disease in four cases. Our study is the first to concurrently evaluate structure, perfusion, and glucose metabolism in Sturge-Weber syndrome and to show a mismatch between functional and structural brain imaging in both cerebral hemispheres. Widespread abnormalities of cerebral perfusion and glucose metabolism might explain the high prevalence of developmental delay associated with Sturge-Weber syndrome. Longitudinal studies are needed to define better the natural history of neurologic deterioration and radiologic progression that relates to central nervous system circulatory dysfunction in Sturge-Weber syndrome. ( J Child Neurol 1998;13:595-605).

Sturge-Weber syndrome is characterized by the presence of a port-wine nevus, epilepsy, stroke-like episodes, headache, and developmental delay. We studied 20 cases to test the hypothesis that decreased cerebral blood flow alters neurologic function by affecting cellular glucose metabolism. Group A consisted of 10 patients with a mean age of 1.75 years and early seizure onset (6.8 months), whereas group B was composed of older patients (mean age, 15.3 years) with later onset of seizures (3.7 years). Neurologic disease was more severe in group A, but group B had more widespread structural brain defects — shown on computed tomographic scans and magnetic resonance imaging — and metabolic brain defects — shown on hexamethylpropyleneamine oxime and [18F] fluorodeoxyglucose single photon emission computed tomographic scans. Six group A cases had hypoperfusion at baseline and five of nine had worsening of perfusion and glucose metabolism 1 year later. A total of 119 stroke-like episodes occurred in six group A cases and eight group B cases; there were 65% fewer strokes in children treated with aspirin. The data suggest that progressive hypoperfusion and glucose hypometabolism are associated with neurologic deterioration in Sturge-Weber syndrome. Longitudinal studies are needed to better define the natural history of disease and to evaluate the safety and efficacy of aspirin therapy. ( J Child Neurol 1998;13:606-618).

Nuclear medicine continues to evolve from a generic imaging approach to a collection of imaging techniques that are disease-specific. In-111 octreotide SPECT scan has quickly become the method of choice to image gastrinoma. A number of other agents have a role in other tumor models. FDG imaging of the liver is in its infancy, but has potential to outperform anatomic methods (CT scan, MR imaging), particularly in the detection of colorectal cancer metastases. The imaging of FDG in nuclear medicine involves rapidly evolving technology and has the potential to diffuse to the community level practice. To further face the controversial areas head on, another problem for nuclear medicine's role in hepatic imaging remains its somewhat separate existence from radiology. Frequently, the abdominal imager or the general radiologist is in the best position to recommend a scintigraphic liver study. A broad knowledge of these techniques by all radiologists is essential for their ultimate success.

nerve, an ipsilateral leptomeningeal angioma, and an angioma of the choroid membrane of the eye producing glaucoma, buphthalmos, and vision loss.2 The neurologic features in affected patients include progresssive mental retardation, intractable seizures localized contralateral to the nevus flammeus, and an associated hemiparesis or hemiplegia.3>4 Radiologic advances have greatly improved the ability to characterize involvement of the central nervous system in Sturge-Weber syndrome although the pathophysiology is still poorly understood.5 The angioma produces obstruction, stasis, and decreased venous return. This in turn may cause ischemic lesions to the underlying cortical and subcortical areas leading to progressive calcium deposition.6,7 Computed tomography (CT) may demonstrate an enlarged choroid plexus from abnormal venous drainage, cortical atrophy, and calcifications of the angioma and underlying cerebral cortex Magnetic resonance imaging (MRI) demonstrates cortical atrophy, choroid plexus enlargement, prominence of the deep venous system, and the angiomas of the meninges and eye.9>&dquo; We report two cases in which cerebral perfusion abnormalities as detected by technetium99m (~9mTc) hexamethylpropyleneamine oxime (HMPAO) single photon emission computed tomography (SPECT) were evident prior to structural abnormalities seen on CT or MRI. In both patients, glucose metabolism in the brain, as measured by [ 18F] fluorodeoxyglucose SPECT was significantly reduced despite a previously normal MRI. In Sturge-Weber syndrome, defects in glucose metabolism or cerebral perfusion may precede the appearance of defects on CT or MRI. In both patients, glucose metabolism in the brain, as measured by [18F] fluorodeoxyglucose SPECT was significantly reduced despite a previously normal MRI.

PURPOSETo evaluate 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) single photon emission computed tomography (SPECT) in the detection of clinically occult primary tumors of the upper aerodigestive tract.MATERIALS AND METHODSEighteen patients with histologically proved cervical nodal metastasis from squamous cell carcinoma (SCC) underwent FDG SPECT; 17 also underwent computed tomography (CT) and one underwent magnetic resonance (MR) imaging. All 18 patients underwent direct panendoscopy and biopsy. Biopsy and imaging results were correlated.RESULTSAmong 11 histologically proved primary tumors, FDG SPECT depicted nine tumors; CT depicted four lesions. Five patients had abnormal FDG uptake with negative biopsy results. Among five patients with normal SPECT findings, biopsy results were positive in two and negative in three. FDG SPECT at the initial reading had sensitivity of 81%, specificity of 38%, positive predictive value of 64%, and negative predictive value of 60% for detection of occult primary tumors.CONCLUSIONFDG SPECT guidance of endoscopic biopsies in patients with occult primary SCCs of the head and neck has the potential to yield a higher rate of positive biopsy results than that traditionally expected from "blind" endoscopic procedures with "random" or "speculative" biopsy. FDG SPECT and CT are likely to remain complementary studies for the detection of occult primary tumors of the head and neck.