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Purpose: To assess the extent to which multiple Alzheimer disease (AD) biomarkers improve the ability to predict future decline in subjects with mild cognitive impairment (MCI) compared with predictions based on clinical parameters alone., Materials and Methods: All protocols were approved by the institutional review board at each site, and written informed consent was obtained from all subjects. The study was HIPAA compliant. Alzheimer's Disease Neuroimaging Initiative (ADNI) baseline magnetic resonance (MR) imaging and fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) studies for 97 subjects with MCI were used. MR imaging-derived gray matter probability maps and FDG PET images were analyzed by using independent component analysis, an unbiased data-driven method to extract independent sources of information from whole-brain data. The loading parameters for all MR imaging and FDG components, along with cerebrospinal fluid (CSF) proteins, were entered into logistic regression models (dependent variable: conversion to AD within 4 years). Eight models were considered, including all combinations of MR imaging, PET, and CSF markers with the covariates (age, education, apolipoprotein E genotype, Alzheimer's Disease Assessment Scale-Cognitive subscale score)., Results: Combining MR imaging, FDG PET, and CSF data with routine clinical tests significantly increased the accuracy of predicting conversion to AD compared with clinical testing alone. The misclassification rate decreased from 41.3% to 28.4% (P < .00001). FDG PET contributed more information to routine tests (P < .00001) than CSF (P = .32) or MR imaging (P = .08)., Conclusion: Imaging and CSF biomarkers can improve prediction of conversion from MCI to AD compared with baseline clinical testing. FDG PET appears to add the greatest prognostic information.

Purpose: To prospectively determine feasibility of evaluating murine left ventricular (LV) function with electrocardiographically (ECG)-gated blood pool single photon emission computed tomography (SPECT)., Materials and Methods: All animal studies had institutional animal care and use committee approval. SPECT was performed with conventional time-binned acquisition (eight frames per ECG cycle) in normal mice (normal group A, n = 6) and mice with myocardial infarction (MI) (n = 8). To determine feasibility of high temporal resolution and rapid data acquisition, another group of normal mice (normal group B, n = 4) underwent imaging with conventional (eight-frame) time-binned and list-mode (LM) acquisitions. LM acquisitions were reconstructed with eight and 16 frames per ECG cycle and 10 minutes of data (short LM). SPECT images were assessed visually, and LV-to-lung background activity ratios were calculated. LV end-systolic and end-diastolic volumes were defined with a phase analysis and threshold method. LV ejection fraction (LVEF) was calculated from LV volumes and count-based methods (n = 18 mice). Fractional shortening (FS) at echocardiography defined MI dysfunction (mild MI: FS > or = 50%; severe MI: FS < 50%). Group means were compared for significant differences with analysis of variance., Results: ECG-gated blood pool SPECT demonstrated normal, concentric LV contraction in all normal mice (n = 10). LV-to-lung background ratio was more than 10:1 (range, 10.3-29.4; n = 18). Focal wall motion abnormalities were detected at SPECT both visually and with phase analysis in all mice with severe MI (n = 5). Mice with severe MI had significantly lower LVEF than normal group A mice (32% +/- 14 [standard deviation] vs 64% +/- 8%; P < .001). All mice with mild MI (n = 3) had normal contraction and LVEF. In paired acquisitions in normal group B mice, all reconstructions (n = 16) showed normal LV contraction. LVEF was not significantly different (P = .88) between time-binned (71% +/- 12), eight-frame LM (71% +/- 12), 16-frame LM (77% +/- 10), and short LM (73% +/- 14) reconstructions., Conclusion: Murine LV functional assessment is feasible with high spatial and temporal resolution ECG-gated blood pool SPECT. LV dysfunction can be quantified and focal wall motion abnormalities detected in the MI model of heart failure.

Purpose: To retrospectively compare the sensitivity of a dedicated fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) protocol versus a standard whole-body PET/CT protocol for detection of head and neck cancer, with biopsy and follow-up as reference standards., Materials and Methods: Institutional review board approval and informed consent were obtained for this HIPAA-compliant study. Dedicated and standard PET/CT protocols were performed in a phantom and in 55 patients suspected of having head and neck cancer (28 men, 27 women; age range, 21-79 years). The neck phantom contained four 4.4-9.8-mm-diameter spheres. Standard protocol consisted of a midcranium to proximal thigh emission scan of 2-4 minutes per bed position. Dedicated protocol was an 8-minute head and neck scan. Reconstructed field of view and pixel size, respectively, were 30 cm and 2.34 mm for the dedicated and 50 cm and 3.91 mm for the standard protocol. FDG uptake was evaluated visually and semiquantitatively by using standardized uptake values (SUVs). Mean SUV was compared between dedicated and standard protocols with a t test modified for clustered sampling. Receiver operating characteristic (ROC) curves were calculated. A two-tailed P value was used., Results: In the phantom study, a larger percentage difference (20%-27%) in sphere-to-background ratios with the dedicated than with the standard protocol was observed for 6.0-9.8-mm spheres. In the clinical study, a total of 149 lymph nodes were identified. Five malignant and six benign lymph nodes (mean diameter, 7.1 mm) were visually identified with the dedicated protocol only. SUVs with the dedicated protocol were significantly higher than those with the standard protocol (P<.001). Area under the ROC curve was 0.94 for the dedicated and 0.92 for the standard protocol (P=.56)., Conclusion: FDG PET with either the standard or dedicated protocol was more sensitive than CT for evaluating head and neck lymph nodes. The dedicated protocol improved the detectability of smaller nodes., ((c) RSNA, 2007.)

Purpose: To determine the feasibility of in vivo localization and quantification of indium 111 (111In)-oxine-labeled bone marrow (BM) with high-resolution whole-body helical single photon emission computed tomography (SPECT) in an established murine model of atherosclerosis and vascular repair., Materials and Methods: The institutional animal care and use committee approved this study. BM from young B6 Rosa 26 Lac Z+/+ mice was radiolabeled with 111In-oxine. On days 1, 4, and 7 after administration of radiolabeled cells, five C57/BL6 apolipoprotein E-deficient mice and five wild-type (WT) control mice were imaged with whole-body high-resolution helical SPECT. Quantification with SPECT was compared with ex vivo analysis by means of gamma counting. Autoradiography and beta-galactosidase staining were used to verify donor cell biodistribution. Linear regression was used to assess the correlation between continuous variables. Two-tailed Student t test was used to compare values between groups, and paired two-tailed t test was used to assess changes within subjects at different time points., Results: SPECT image contrast was high, with clear visualization of BM, liver, and spleen 7 days after administration of radiolabeled cells. SPECT revealed that 42% and 58% more activity was localized to the aorta and BM (P<.05 for both), respectively, in apolipoprotein E-deficient mice versus WT mice. Furthermore, 28% and 27% less activity was localized to the liver and spleen (P<.05 for both), respectively, in apolipoprotein E-deficient mice versus WT mice. SPECT and organ gamma counts showed good quantitative correlation (r=0.9). beta-Galactosidase staining and microautoradiography of recipient aortas showed donor cell localization to the intima of visible atherosclerotic plaque but not to unaffected regions of the vessel wall., Conclusion: High-resolution in vivo helical pinhole SPECT can be used to monitor and quantify early biodistribution of 111In-oxine-labeled BM in a murine model of progenitor cell therapy for atherosclerosis., (Copyright (c) RSNA, 2007.)

Purpose: To prospectively assess a dedicated, large field of view positron emission tomography (PET) mammographic device for imaging primary breast carcinoma., Materials and Methods: Institutional review board approval was obtained for this study, and all patients provided written informed consent prior to participation. Subjects were recruited from a cohort of patients in whom diagnostic mammography and/or ultrasonography demonstrated lesions that were highly suggestive of malignancy. Twenty-three patients who met the inclusion criteria were subsequently imaged by using a dedicated PET mammography unit that was developed in conjunction with the Thomas Jefferson National Accelerator Facility (Newport News, Va). One hour after administration of 2.0-2.5 mCi (74.0-93.5 MBq) of fluorodeoxyglucose, 5-minute PET mammography of the affected breast was performed. Images were processed and reconstructed in the transverse craniocaudal and coronal planes. For each lesion, image-guided core-needle biopsy was performed immediately after PET mammography. Conventional mammography results and histologic findings were correlated with PET mammography images. The sensitivity, specificity, negative predictive value, and positive predictive value of PET mammography for demonstrating malignant lesions were calculated., Results: PET mammography demonstrated 20 focal abnormalities, of which 18 were malignant and two were benign. Both benign lesions represented areas of fat necrosis. Three of 20 malignant lesions demonstrated at conventional mammography were not demonstrated at PET mammography. The overall sensitivity of PET mammography for malignancy was 86% (95% confidence interval: 65%, 95%), with a positive predictive value of 90% (95% confidence interval: 70%, 97%). The calculated specificity was 33% (95% confidence interval: 2%, 79%), and the negative predictive value was 25% (95% confidence interval: 1%, 70%)., Conclusion: These pilot data suggest that PET mammography can demonstrate small primary breast malignancies., ((c) RSNA, 2005.)

Purpose: To determine if there was any difference in the ability of physicians to predict prognosis with technetium 99m ((99m)Tc) sestamibi or (99m)Tc tetrofosmin in a large consecutive series of patients at high risk for coronary artery disease who underwent coronary angiography., Materials and Methods: This study included 1,818 consecutive patients who underwent a rest and stress single photon emission computed tomographic (SPECT) examination with either (99m)Tc sestamibi (n = 915) or (99m)Tc tetrofosmin (n = 903) and cardiac catheterization. A clinical index was generated and consisted of clinical and demographic variables. Information concerning death, cardiovascular death, and nonfatal myocardial infarction was 93% complete during the 1.5-year study period. Cox proportional hazards models were generated to help determine the incremental contribution of SPECT sum stress score (SSS) and the imaging agent variable to the clinical index., Results: Exercise was used for stress testing in 473 (52%) patients who received (99m)Tc tetrofosmin and 519 (57%) patients who received (99m)Tc sestamibi (P =.06). Cardiovascular death or myocardial infarction occurred in 130 patients. Resulting P values for chi(2) differences between models for the end points of (a) death from any cause, (b) cardiovascular death, and (c) cardiovascular death or myocardial infarction showed that SSS combined with clinical index was a significantly better model than adjusting for only baseline characteristics (P =.001, P <.001, P =.004, respectively). Incremental addition of either (99m)Tc tetrofosmin or (99m)Tc sestamibi to those models containing SSS and the clinical index did not show further significant improvement (P =.87, P =.88, and P =.26 for death from any cause, cardiovascular death, and cardiovascular death or myocardial infarction, respectively)., Conclusion: This study shows that the type of clinically available (99m)Tc-labeled myocardial perfusion agents should not affect interpretation of results for risk stratification and prognostic assessment., (Copyright RSNA, 2004)

Positron emission tomography (PET) provides metabolic information that has been documented to be useful in patient care. The properties of positron decay permit accurate imaging of the distribution of positron-emitting radiopharmaceuticals. The wide array of positron-emitting radiopharmaceuticals has been used to characterize multiple physiologic and pathologic states. PET is used for characterizing brain disorders such as Alzheimer disease and epilepsy and cardiac disorders such as coronary artery disease and myocardial viability. The neurologic and cardiac applications of PET are not covered in this review. The major utilization of PET clinically is in oncology and consists of imaging the distribution of fluorine 18 fluorodeoxyglucose (FDG). FDG, an analogue of glucose, accumulates in most tumors in a greater amount than it does in normal tissue. FDG PET is being used in diagnosis and follow-up of several malignancies, and the list of articles supporting its use continues to grow. In this review, the physics and instrumentation aspects of PET are described. Many of the clinical applications in oncology are mature and readily covered by third-party payers. Other applications are being used clinically but have not been as carefully evaluated in the literature, and these applications may not be covered by third-party payers. The developing applications of PET are included in this review.

Alzheimer disease (AD), a progressive neurodegenerative disorder, is the most common cause of dementia in the elderly. Current consensus statements have emphasized the need for early recognition and the fact that a diagnosis of AD can be made with high accuracy by using clinical, neuropsychologic, and imaging assessments. Magnetic resonance (MR) or computed tomographic (CT) imaging is recommended for the routine evaluation of AD. Coronal MR images can be useful to document or quantify atrophy of the hippocampus and entorhinal cortex, both of which occur early in the disease process. Both volumetric and subtraction MR techniques can be used to quantify and monitor dementia progression and rates of regional atrophy. MR measures are also increasingly being used to monitor treatment effects in clinical trials of cognitive enhancers and antidementia agents. Positron emission tomography (PET) and single photon emission CT offer value in the differential diagnosis of AD from other cortical and subcortical dementias and may also offer prognostic value. In addition, PET studies have demonstrated that subtle abnormalities may be apparent in the prodromal stages of AD and in subjects who carry susceptibility genes. PET ligands are in late-stage development for demonstration of amyloid plaques, and human studies have already begun. Functional MR-based memory challenge tests are in development as well.

Purpose: To compare fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) with the current standard, magnetic resonance (MR) imaging, to determine the sensitivity and specificity of FDG PET for detection of cerebral metastases and to determine the factors that may affect lesion conspicuity., Materials and Methods: Forty patients underwent brain PET and contrast material-enhanced brain MR imaging, with a maximum of 30 days between examinations. PET and MR images were each retrospectively reviewed by two independent readers who were blinded to the clinical history and results of the other technique. Presence of metastatic disease was recorded for each modality. Sensitivity and specificity of FDG PET were determined with MR imaging as the standard. Statistical analysis was performed with the Fisher exact test and the logistic regression model., Results: Sixteen patients had cerebral metastases at MR imaging, and in 12 of these, PET scans were interpreted as showing metastatic disease (in four, scans were false-negative). Twenty-four patients had no cerebral metastases at MR imaging, and 20 of these had PET scans interpreted as normal (in four, scans were false-positive). For identification of patients with cerebral metastases, FDG PET had a sensitivity of 75% (12 of 16) and a specificity of 83% (20 of 24). Thirty-eight metastatic lesions were seen at MR imaging; 23 (61%) of these were identified at PET. Size was a statistically significant factor that influenced lesion detection at PET (P <.001)., Conclusion: Only 61% of metastatic lesions in the brain were identified at PET. In particular, detection of small lesions was difficult., (Copyright RSNA, 2002)

Purpose: To investigate the relationship between the development of ischemia during stress testing and the changes in left ventricular ejection fraction (LVEF) measurements obtained after stress and at rest with a same-day perfusion-function imaging protocol., Materials and Methods: One hundred twenty-six patients underwent a same-day rest-stress (61%) or stress-rest (39%) protocol and gated single photon emission computed tomography (SPECT). Perfusion analysis was performed with a 12-segment model. Defects were scored (0 = no defect, 1 = mild defect, 2 = moderate defect, and 3 = severe defect); differences between the summed stress and resting scores of greater than three indicated substantial ischemia., Results: Resting and poststress LVEFs correlated significantly (r = 0.97, P <.001); however, patients with and patients without ischemia had significant differences in poststress versus resting LVEFs (-4.0 vs 1.0, respectively; P <.01). In patients with ischemia versus patients without ischemia, subgroup analysis stress-rest (-2.5 vs 1.0, P =.047) and rest-stress (-4.0 vs 1.0, P =.006) protocols yielded similar results., Conclusion: In patients with clinically important stress-induced perfusion abnormalities, the LVEF after stress was significantly lower than the LVEF at rest with same-day rest-stress and stress-rest imaging protocols. In the clinical setting, poststress LVEFs may be lower than true resting measurements, particularly in patients with moderate to severe stress-induced ischemia.

Purpose: To assess the appropriateness of ventilation-perfusion (V-P) scintigraphic abnormalities as a guide to pulmonary angiography for the diagnosis of pulmonary embolism (PE)., Materials and Methods: V-P scintigrams and pulmonary angiograms of 104 patients with angiographically proved PE were reviewed by two nuclear medicine physicians and two interventional radiologists. For V-P scintigrams, the lung with the larger amount of perfusion abnormality was determined followed by identification of specific lobes. Pulmonary angiograms were similarly evaluated for lateralization and lobar distribution of PE. Conclusions were initially reached independently and subsequently by consensus., Results: Interobserver agreement for lateralization was 88% (kappa = 0.75) for V-P scintigraphy and 98% (kappa = 0.96) for pulmonary angiography. In 72 patients, V-P scintigrams predicted unilateral embolus; 64 patients underwent pulmonary angiography of the suspected side. Eight patients underwent contralateral angiography only. Of the 64 patients, 61 (95%) had PE on the predicted side at angiography. V-P scintigrams predicted lobar distribution in 55 patients. Of these, PE was found in the predicted lobe in 42 (76%)., Conclusion: Localization of perfusion abnormalities at V-P scintigraphy provides useful information for the interventional radiologist and serves as an accurate guide for determining the initial approach for pulmonary angiography.

Purpose: To compare the accuracies of whole-body 2-[fluorine 18]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) and conventional imaging (thoracic computed tomography [CT], bone scintigraphy, and brain CT or magnetic resonance [MR] imaging) in staging bronchogenic carcinoma., Materials and Methods: Within 20 months, 100 patients with newly diagnosed bronchogenic carcinoma underwent whole-body FDG PET and chest CT. Ninety of these patients underwent radionuclide bone scintigraphy, and 70 patients underwent brain CT or MR imaging. For each patient, all examinations were completed within 1 month. A radiologic stage was assigned by using PET and conventional imaging independently and was compared with the pathologic stage. The accuracy, sensitivity, specificity, and negative and positive predictive values were calculated., Results: PET staging was accurate in 83 (83%) patients; conventional imaging staging was accurate in 65 (65%) patients (P < .005). Staging with mediastinal lymph nodes was correct by using PET in 67 (85%) patients and by using CT in 46 (58%) patients (P < .001). Nine (9%) patients had metastases demonstrated by using PET that were not found with conventional imaging, whereas 10 (10%) patients suspected of having metastases because of conventional imaging findings were correctly shown with PET to not have metastases., Conclusion: Whole-body PET was more accurate than thoracic CT, bone scintigraphy, and brain CT or MR imaging in staging bronchogenic carcinoma.

Purpose: To evaluate 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) imaging of simulated lung nodules in a realistic chest phantom by using attenuation-corrected and non-attenuation-corrected 511-keV single photon emission computed tomography (SPECT), camera-based positron emission tomography (PET), and dedicated PET imaging., Materials and Methods: Spheres with diameters of 6, 10, 13, and 22 mm were placed in the lungs of an anthropomorphic chest phantom to simulate nodules. The lungs, nodules, chest wall, and mediastinum were filled with fluorine-18 activities based on the average radionuclide concentrations in those structures from analysis of attenuation-corrected dedicated FDG PET scans. The image sets were evaluated visually and quantitatively by using contrast and signal-to-noise ratios., Results: Attenuation correction reduced the artificially high apparent uptake in the lungs, restored the spherical shape to the nodules, and provided an accurate outer body contour with appropriate intensity. Dedicated PET depicted all four nodules, camera-based PET depicted the three largest nodules, and SPECT depicted the two largest nodules. Lesion contrast was better on the attenuation-corrected images than on the non-attenuation-corrected images. The signal-to-noise ratio generally was improved with attenuation correction., Conclusion: Attenuation correction results in many changes in the images and improves lesion detection.

Purpose: To evaluate the cost-effectiveness of artificial neural networks for diagnosis in patients suspected of having acute pulmonary embolism who are typically referred for pulmonary angiography., Materials and Methods: Four diagnostic strategies were explored to help define the diagnostic role of neural networks in patients suspected of having pulmonary embolism in whom nondiagnostic ventilation-perfusion lung scans were obtained. First, a network was used to determine which patients could be directly referred for treatment without angiography. Second, the network was applied to determine in which patients treatment could be withheld. Third, the network was used to distinguish patients in whom the network gave indeterminate responses and who should proceed to angiography. Each strategy was compared with use of angiography in terms of morbidity, mortality, and cost per life saved., Results: The use of the neural network reduced the average cost per patient by more than one-half relative to the cost of angiography. Morbidity and mortality rates were also comparable to or lower than those associated with angiography. The results were consistent regardless of the prevalence of disease., Conclusion: The use of neural networks in the diagnosis of pulmonary embolism is a promising way to improve cost-effectiveness in the care of patients with nondiagnostic lung scans.

The D-glucose analogue 2-(fluorine-18) fluoro-2-deoxy-D-glucose (FDG) is the most commonly used radionuclide in positron emission tomography (PET) of the thorax. Increased glucose metabolism by malignant cells allows physiologic differentiation between benign and malignant abnormalities. FDG PET is consequently useful in characterizing indeterminate pulmonary nodules and in staging and assessing the response to treatment of lung cancer. FDG PET is accurate in classification of indeterminate pulmonary nodules as benign. Nodules with low FDG uptake are followed up radiographically; nodules with increased FDG uptake should be evaluated with biopsy or resected. In the staging of lung cancer, FDG PET is useful in evaluating local disease and pleural and chest wall involvement. The accuracy of FDG PET in demonstrating intrathoracic metastatic nodal disease is greater than that of computed tomography or magnetic resonance imaging. Whole-body PET is useful in detection of extrathoracic metastases. Conventional imaging often does not allow differentiation of tumor from posttreatment scarring. Increased FDG uptake at the sites of residual radiographic abnormalities is indicative of persistent or recurrent tumor.

Purpose: To assess the clinical and imaging findings in primary muscle lymphoma., Materials and Methods: Seven patients with biopsy-proved primary muscle lymphoma without evidence of systemic disease underwent imaging with plain radiography or computed tomography (CT) and magnetic resonance (MR) imaging. Four underwent bone scintigraphy, and two underwent gallium scintigraphy and fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) before and after therapy., Results: Plain radiographs at initial examination (n = 5) showed no bone abnormalities. Soft-tissue masses and bone marrow involvement showed isoattenuation at CT (n = 3), but at MR imaging (n = 7), all masses demonstrated increased signal intensity on T2-weighted images that involved multiple muscle compartments and typically spanned a long segment of the extremity. Adjacent bone disease was less extensive than muscle disease, and, in most cases, subcutaneous stranding or extension was observed adjacent to the masses. Good size correlation was observed between findings at MR imaging, gallium scintigraphy, and FDG PET. Two patients developed recurrent multifocal muscle lymphoma several years after initial examination., Conclusion: The presence of an extensive soft-tissue mass with infiltration of adjacent subcutaneous fat and minimal or no extension into the bone marrow cavity at MR imaging and normal plain radiographic findings may suggest primary muscle lymphoma.

Purpose: To assess methods of standard uptake ratio (SUR) calculation with 2-deoxy-2-[fluorine-18]fluoro-D-glucose (FDG) positron emission tomography (PET) in indeterminate focal pulmonary abnormalities., Materials and Methods: One hundred ninety-seven adult patients with indeterminate pulmonary abnormalities had complete FDG PET data, consistent methods of data acquisition, and definitive diagnosis with tissue biopsy or negative 2-year follow-up findings. PET studies were evaluated by using SURs calculated with the average or maximum region-of-interest pixel value in the numerator and with weight, lean body mass, or body surface area in the denominator., Results: One hundred twenty malignant lesions and 77 benign processes were identified. Receiver operating characteristic (ROC) curve areas were statistically significantly larger with the average rather than the maximum pixel value in the calculation of the SUR for any of the three denominators (P < or = .05). SURs calculated with weight versus lean body mass versus body surface area in the denominator showed no statistically significant difference in ROC curve areas., Conclusion: SURs determined by using average pixel values provide statistically significant improvement in ROC curve areas over those determined by using maximum pixel values. Weight, lean body mass, and body surface area in the denominator of the SUR calculation provide equivalent ROC curve areas and are therefore equivalent in accuracy in this population.

Purpose: To evaluate the accuracy of technetium-99m sestamibi as a single agent in the detection and localization of hyperfunctioning parathyroid tissue in patients who underwent prior neck exploration or who otherwise are high surgical risks., Materials and Methods: Thirty-nine patients with hyperparathyroidism underwent 40 double-phase Tc-99m sestamibi studies. Histopathologic correlation was obtained for all studies., Results: Thirty patients had solitary adenomas, and nine had hyperplastic glands. One developed recurrent hypercalcemia after five-gland resection and underwent repeat imaging and operation. Double-phase sestamibi imaging prospectively enabled localization of 46 (77%) of 60 abnormal glands. Twenty-eight (93%) of 30 adenomas were correctly localized, whereas 18 (60%) of 30 hyperplastic glands were localized. The overall specificity of the study was 98% with one false-positive study. Gland weight and vascularity were statistically significant predictors of uptake of sestamibi., Conclusion: Double-phase Tc-99m sestamibi imaging is a promising technique for localization of parathyroid adenomas in high-risk surgical patients. Localization of multiple hyperplastic glands remains a challenge.

Purpose: To compare the diagnostic performance of an artificial neural network (ANN) with that of physicians in patients with suspected pulmonary embolism (PE)., Materials and Methods: An ANN was developed to predict PE by using findings from ventilation-perfusion lung scans and chest radiographs. First, the network was evaluated on 1,064 cases from the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study that had a definitive angiographic outcome. An upper and lower bound of its diagnostic performance was provided depending on case difficulty. Then, the network was tested on 104 patients with suspected PE in whom pulmonary angiography was essential for diagnosis. The diagnostic performance of the ANN was compared with that of (a) two nuclear medicine physicians who read the scans for the needs of this study and (b) the nuclear medicine physicians who originally read the scans. The effects of case and observer selection on performance were addressed., Results: The ANN outperformed the physicians when they used the PIOPED criteria for categoric assessment, and it performed as well as the two study physicians on the basis of their probability assessments., Conclusion: The ANN can detect or exclude PE in a highly selected group of difficult cases with a consistency equivalent to that of very experienced physicians.

Purpose: To evaluate the accuracy of the revised PIOPED (Prospective Investigation of Pulmonary Embolism Diagnosis) criteria for categorization of ventilation-perfusion lung scans and to compare the diagnostic accuracy of the revised criteria with that of the original PIOPED criteria and subjective probability estimates., Materials and Methods: The ventilation-perfusion scans of 104 consecutive patients with suspected pulmonary embolism were reviewed. All patients had also undergone pulmonary angiography. The scans were categorized according to the original and revised PIOPED criteria, and a "gestalt" percent probability estimate was made. In addition, the official clinical interpretation (made with the original PIOPED criteria) was recorded., Results: The gestalt percent probability estimate was the most accurate for assessing the likelihood of pulmonary embolism (area under the receiver operating characteristic [ROC] curve = 0.836). The revised PIOPED criteria (area under the ROC curve = 0.753) were more accurate than the original PIOPED criteria., Conclusion: The revised PIOPED criteria are more accurate than the original PIOPED criteria. Experienced readers of lung scans can achieve higher accuracy after applying formal criteria by using their experience and subjective judgment.

Purpose: To investigate use of an artificial neural network (ANN) as a computer-aided diagnostic (CAD) tool for predicting pulmonary embolism (PE) from ventilation-perfusion lung scans and chest radiographs., Materials and Methods: The data base consisted of cases extracted from the collaborative study of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED). Initially, scan findings from 1,064 patients (383 with PE, 681 without PE) were used to train and test the network by using the "jackknife" method. Then, a receiver-operating-characteristic analysis was applied to compare the performance of the network with that of the physicians involved in the PIOPED study., Results: The ANN significantly outperformed the physicians involved in the PIOPED study (two-tailed P value = .01)., Conclusion: The findings suggest that an ANN can form the basis of a CAD system to assist physicians with the diagnosis of PE.

The authors assessed the role of positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose (FDG) in differentiation of benign from malignant focal pulmonary abnormalities seen on chest radiographs. Fifty-one patients underwent FDG PET scanning. Focal abnormalities at radiography included solitary pulmonary nodules (n = 38), pulmonary masses (n = 5), and poorly marginated infiltrates or opacities (n = 8). Proof of diagnosis was obtained by means of transbronchial biopsy (n = 21), open lung biopsy (n = 14), percutaneous needle biopsy (n = 14), or cytologic evaluation of sputum (n = 1). A nodule in one patient had been radiographically stable for at least 8 years. Quantitative analysis was performed by calculation of a standardized uptake ratio (SUR). Thirty-three malignant lesions had a mean SUR (+/- 1 standard deviation) of 6.5 +/- 2.9. Eighteen benign lesions had a mean SUR of 1.7 +/- 1.2. For a benign lesion with SUR of 2.5 or less, specificity of FDG PET was 100%, while sensitivity was 89%. These results suggest that FDG PET is accurate in differentiation of benign from malignant focal pulmonary abnormalities.

The medical records of 66 patients who underwent evaluation for possible deep venous thrombosis (DVT) by means of gradient-echo (GRE) magnetic resonance (MR) imaging were reviewed. Confirmatory venograms were obtained in 26 patients; in the other 40, the accuracy of GRE MR imaging was assessed by means of clinical follow-up, which ranged from 1 to 23 months (mean, 7.7 months). Findings in GRE MR images were negative in 42 patients (64%) and positive in 24 patients (36%). In patients who underwent confirmatory venography, the sensitivity of GRE MR imaging was 100% and the specificity was 92.9%. No patient with a negative GRE MR study developed DVT or pulmonary emboli during the follow-up period. Although seven patients in this group died, the single autopsy showed no evidence of pulmonary embolism, and no clinical evidence existed to suggest that pulmonary embolism was the cause of death in any of the other six patients. It is concluded that GRE MR imaging is an accurate, noninvasive means of detecting DVT.

Radionuclide renograms obtained with Tc-99m-DTPA were used to calculate relative renal blood flow in 16 dogs. In 13 of these dogs, relative blood flow ratios (R:L) calculated from the renograms were correlated with ratios measured with an electromagnetic flowmeter or with radiolabeled microspheres. The results indicate that Tc-99m-DTPA renograms can be used to make an accurate prediction of relative renal blood flow.

Images were obtained with Ga-67 and bronchopulmonary lavage performed in 21 patients with sarcoidosis (31 studies). The Ga-67 index, a semiquantitative criterion, was compared to a quantitative computer index based on lung:liver activity ratios; accuracy in predicting active alveolitis (defined by lavage lymphocyte counts) was assessed and differences between 24- and 48-hour studies examined. Computer activity ratios correlated well with the Ga-67 index, which had a sensitivity of 64%, specificity of 71%, and accuracy of 68% compared to 71%, 82%, and 77%, respectively, for the computer scores. Scores at 24 and 48 hours were similar. These results suggest that (a) Ga-67 scanning is useful in staging activity in pulmonary sarcoidosis, (b) quantitative computer scores are accurate in predicting disease activity, and (c) scanning can be performed 24 or 48 hours after injection.

A linear attenuation coefficient for water (mu = .15 cm-1) at 140 keV has been used in the determination of left ventricular volumes (LVV) by attenuation-corrected equilibrium methods. This theoretical value ignores the effect of Compton scatter and thus may be too high for human LVV determinations. The effective attenuation coefficient, mu', of the human chest was determined in ten normal volunteers using a Tc-99m esophageal source imaged with a gamma camera. Values for mu' at 30 degrees LAO in end-expiration, quiet breathing, and end-inspiration were .125 +/- .006 cm-1, .125 +/- .005 cm-1, and .113 +/- .007 cm-1, respectively (95% confidence interval). Values of mu' at 45 degrees LAO were .122 +/- .006 cm-1, .119 +/- .007 cm-1, and .099 +/- .009 cm-1, respectively, for the same conditions. The measured value of mu' for the source in a water phantom was .127 +/- .001 cm-1. This suggests that a value of mu' of .125 cm-1 may be appropriate for use in determining LVV in patients.

Single photon emission computed tomography (SPECT) allows separation of radionuclide activity in front of and behind the area of interest and results in more contrast than can be achieved using conventional gamma camera imaging. To determine if this improved contrast is of value in the detection of perfusion abnormalities in the lung, the lower lobe segmental pulmonary arteries of six dogs were embolized and pulmonary perfusion was evaluated using SPECT, conventional gamma camera imaging, and angiography. Although selective segmental angiography was the most sensitive method of detecting emboli, SPECT was much more sensitive than the gamma camera examination in evaluating the effects of the emboli at two hours and one, two, and eight weeks after embolization.

To determine the value of the initial phase of the Tc-99m DTPA renogram in the direct estimation of relative renal blood flow in dogs, the ratios of the slopes of renal time-activity curves were compared with the ratios of measured blood flow. Radionuclide results were dependent on region-of-interest (ROI) and background ROI assignment, and correlated well with measured relative flow only with a maximum renal outline region. Curve slope ratios correlated well with measured flow ratios with and without background correction, while 1- to 2-minute uptake ratios correlated well only when corrected for background.

One can calculate the tissue-blood ratio of enhancement by analyzing the quantitative aspects of the CT scans of the cranium and blood samples both before and after the injection of contrast medium. This ratio is equivalent to that between the iodine content of a given volume of tissue and an equal volume of blood. Analysis of 47 normal patients, including 27 with pathological brain lesions, indicated that there is significant extravasation of contrast medium in patients with such lesions.

Leukocytes labeled with 111In chelated with 8-hydroxyquinoline were evaluated as an abscess imaging agent in dogs. The labeling technique is simple and offers 75-95% efficiency. The half-clearance time of the labeled leukocytes is 6-10 hours, and the target-to-blood activity ratios are higher than those of other compounds now in use. The authors suggest that 111In-labeled leukocytes replace 67Ga citrate as a routine abscess imaging agent.

Twenty patients with 21 total joint replacements including 17 hips and 4 knees were studied by plain film radiography, radionuclide imaging, and subtraction arthrography to evaluate these procedures for assessing prosthetic complications. Surgery was performed in 14 patients and confirmed loosening of 8 femoral and 7 acetabular hip prosthesis components and 1 femoral and 4 tibial knee prosthesis components. Plain films suggested loosening of only 9 hip components and no knee components. In contrast, radionuclide imaging and subtraction arthrography were considerably more effective in demonstrating loosening as well as other causes of the painful total joint prosthesis.

Eighty-two patients with pathologically proved carcinoid tumors were examined with iodine-131 metaio-dobenzylguanidine (MIBG) scintigraphy. Localization scores of I-131 MIBG accumulation in the primary tumor or metastatic site ranged from 0 to 3+ on the basis of comparison with normal liver. I-131 MIBG uptake varied greatly in different patients with carcinoid tumors. The localization scores in known tumor sites were related to the location of the primary tumor in the stomach (1-3+ in two of five patients), pancreas (1-3+ in four of five patients), cecum (3+ in two of two patients), appendix (0 in one of one patient), jejunum (0 in one of one patient), Meckel diverticulum (3+ in one of one patient), terminal ileum (2-3+ in 19 of 28 patients), bronchus (3+ in one of nine patients), thymus (1+ in one of two patients), and unknown (2-3+ in 18 of 28 patients). Tumors of midgut origin concentrated I-131 MIBG more frequently than those of foregut origin. Uptake of I-131 MIBG was more likely if neurohumor levels, particularly serum serotonin, were elevated. There was no relationship of I-131 MIBG uptake to carcinoid syndrome. I-131 MIBG is useful in the determination of the location and extent of some carcinoid tumors, particularly those of midgut origin.

Many nuclear medicine physicians use criteria put forth by McNeil or Biello et al. to interpret lung scintigrams, while others use an integration of these and other reported or personal criteria. Interobserver variation within these schemes has not been assessed, nor have the schemes been compared with each other using the same set of scans. Two experienced nuclear medicine physicians independently read 98 scans that were collected over a two year period and that had angiographic correlation. Perfusion, ventilation, and radiographic abnormalities were described objectively, and each case was assigned to a McNeil category, a Biello category, and an estimate of probability was made based on the reader's own synthesis of criteria (modified criteria). The two readers differed widely in describing the number, size, and location of abnormalities. Despite the large interobserver variation in objective descriptions, there were no statistically significant differences between the receiver operating characteristic (ROC) curves for each reader. When the ROC curves for each set of criteria were compared, the results did not confirm that one set of criteria was clearly superior to another. The Biello and modified criteria did classify fewer cases as indeterminate or intermediate probability without a drop in overall accuracy. When data were subdivided by year, analysis still showed no statistically significant differences between criteria or readers. There was, however, a significant difference (P less than .001) in overall accuracy when ROC curves for the two years were compared. This has implications for data obtained in retrospective studies of lung scintigraphy.

Inverse Monte Carlo (IMOC) is a unified reconstruction algorithm for single photon emission computed tomography (SPECT) that provides simultaneous compensation for attenuation and collimator divergence. IMOC was applied to the reconstruction of SPECT images of a brain phantom with iodine-123 and high-resolution collimation. Projection sets containing 80,000, 540,000, and 5.2 million counts were reconstructed. Comparison with filtered back-projection reconstructions showed that the IMOC reconstructions provided superior noise and resolution characteristics at all three photon densities. Results of this study indicate that IMOC may allow the use of high-resolution, low-sensitivity collimation for SPECT studies, which have traditionally provided photon yields too low for useful imaging.

The appearances of the lungs on radiographs and computed tomographic (CT) scans were correlated with degree of uptake on gallium scans and results of pulmonary function tests (PFTs) in 27 patients with sarcoidosis. CT scans were evaluated both qualitatively and quantitatively. Patients were divided into five categories on the basis of the pattern of abnormality at CT: 1 = normal (n = 4); 2 = segmental air-space disease (n = 4); 3 = spherical (alveolar) masslike opacities (n = 4); 4 = multiple, discrete, small nodules (n = 6); and 5 = distortion of parenchymal structures (fibrotic end-stage sarcoidosis) (n = 9). The percentage of the volume judged to be abnormal (CT grade) was correlated with PFT results for each CT and radiographic category. CT grades were also correlated with gallium scanning results and percentage of lymphocytes recovered from bronchoalveolar lavage (BAL). Patients in CT categories 1 and 2 had normal lung function, those in category 3 had mild functional impairment, and those in categories 4 and 5 showed moderate to severe dysfunction. The overall CT grade correlated well with PFT results expressed as a percentage of the predicted value. In five patients, CT scans showed extensive parenchymal disease not seen on radiographs. CT grades did not correlate with the results of gallium scanning or BAL lymphocytes. The authors conclude that patterns of parenchymal sarcoidosis seen at CT correlate with the PFT results and can be used to indicate respiratory impairment.

The authors provide evidence of significant extravasation of contrast media responsible for the contrast enhancement of pathological tissue on computed tomography. The tissue-blood ratio of enhancement was calculated by the EMI scanner in 2 patients after injection of contrast material and prior to surgery; tumor-blood ratios for red blood cell and plasma tracers were calculated after surgery. The ratios of enhancement demonstrated the analogy between contrast enhancement and the leaking of radionuclide across the blood-brain barrier. This phenomenon may cause error if this technique is used for the measurement of cerebral blood volume. The area for complementary roles of CT and radionuclide brain imaging seems to be narrower than expected.