Effects of ethanol on axon outgrowth and branching in developing rat cortical neurons.

Humans exposed prenatally to ethanol can exhibit brain abnormalities and cognitive impairment similar to those seen in patients expressing mutant forms of the L1 cell adhesion molecule (L1CAM). The resemblance suggests that L1CAM may be a target for ethanol, and consistent with this idea, ethanol can inhibit L1CAM adhesion in cell lines and L1CAM-mediated outgrowth and signaling in cerebellar granule neurons. However, it is not known whether ethanol inhibits L1CAM function in other neuron types known to require L1CAM for appropriate development. Here we asked whether ethanol alters L1CAM function in neurons of the rat cerebral cortex. We find that ethanol does not alter axonal polarization, L1CAM-dependent axon outgrowth or branching, or L1CAM recycling in axonal growth cones. Thus, ethanol inhibition of L1CAM is highly dependent on neuronal context.

ROC and LROC analyses of the effects of lesion contrast, size, and signal-to-noise ratio on detectability in PET images.

UNLABELLED: Image quality in PET is typically assessed using measures such as contrast recovery, noise variation, and signal-to-noise ratio (SNR). However, these criteria do not directly reflect performance in the clinical use of the images. Lesion detection is a critical task in the clinical interpretation of many PET studies. A receiver operating characteristic (ROC) study is an accepted method for quantitatively evaluating detection performance with respect to factors that influence image quality. ROC and localization ROC (LROC) analyses were conducted to investigate the effects of lesion contrast, SNR, and size on detectability of hot lesions in PET images. METHODS: A thorax phantom was imaged with spheres of 3 sizes simulating lesions (0.45, 1.0, and 1.9 mL). The relative activity in the lesions and the total number of counts acquired were each varied by factors of 2 to ascertain the effects of contrast and SNR, respectively. Measured attenuation correction and a standard reconstruction protocol were used. Three nuclear medicine physicians and 6 medical physicists participated as readers, rating each image and indicating the suspected lesion location. The area under the calculated ROC and LROC curves (Az and Az,LROC) were used as measures of detection performance. RESULTS: Detection performance was shown to increase from virtually random (Az approximately 0.5, Az,LROC approximately 0.2) to superior (Az > 0.9, Az,LROC > 0.9) as lesion contrast was increased by 50% and as lesion SNR was doubled. Detection performance was not seen to vary when comparison was made using image-based measures alone. CONCLUSION: This study quantitatively shows that moderate increases in the image-based measures of lesion contrast and SNR give a relatively large increase in the task-based measure of lesion detection as measured by ROC and LROC analyses. Thus, techniques that give modest increases in lesion contrast or SNR are expected to improve detection. Results will be useful in evaluating improvement in detection for various reconstruction, acquisition, and data analysis methods that enhance contrast or noise performance.

Intraoperative probes and imaging probes.

Intraoperative probes have been employed to assist in the detection and removal of tumors for more than 50 years. For a period of about 40 years, essentially every detector type that could be miniaturized had been tested or at least suggested for use as an intraoperative probe. These detectors included basic Geiger-Müller (GM) tubes, scintillation detectors, and even state-of-the-art solid state detectors. The radiopharmaceuticals have progressed from (32)PO(4)(-) injections for brain tumors to sophisticated monoclonal antibodies labeled with iodine-125 for colorectal cancers. The early work was mostly anecdotal, primarily interdisciplinary collaborations between surgeons and physical scientists. These collaborations produced a few publications, but never seemed to result in an ongoing clinical practice. In the mid 1980s, several companies offered basic gamma-detecting intraoperative probes as products. This led to the rapid development of radioimmunoguided surgery (RIGS) and sentinel node detection as regularly practiced procedures to assist in the diagnosis and treatment of cancer. In recent years intraoperative imaging probes have been developed. These devices add the ability to see the details of the detected activity, giving the potential of using the technique in a low-contrast environment. Intraoperative probes are now established as clinical devices, they have a commercial infrastructure to support their continued use, and there is ongoing research, both commercial and academic, that would seem to ensure continued progress and renewed interest in this slowly developing field.

Calculation of positron range and its effect on the fundamental limit of positron emission tomography system spatial resolution.

Developments in positron emission tomography (PET) technology have resulted in systems with finer detector elements designed to further improve spatial resolution. However, there is a limit to what extent reducing detector element size will improve spatial resolution in PET. The spatial resolution of PET imaging is limited by several other factors, such as annihilation photon non-collinearity, positron range, off-axis detector penetration, detector Compton scatter, undersampling of the signal in the linear or angular directions for the image reconstruction process, and patient motion. The overall spatial resolution of the systems is a convolution of these components. Of these other factors that contribute to resolution broadening, perhaps the most uncertain, poorly understood, and, for certain isotopes, the most dominant effect is from positron range. To study this latter effect we have developed a Monte Carlo simulation code that models positron trajectories and calculates the distribution of the end point coordinates in water for the most common PET isotopes used: 18F, 13N, 11C and 15O. In this work we present some results from these positron trajectory studies and calculate what effect positron range has on the overall PET system spatial resolution, and how this influences the choice of PET system design parameters such as detector element size and system diameter. We found that the fundamental PET system spatial resolution limit set from detector size, photon non-collinearity and positron range alone varied from nearly 1 mm FWHM (2 mm FWTM) for a 10-20 cm diameter system typical for animal studies with 18F to roughly 4 mm FWHM (7 mm FWTM) for an 80 cm diameter system typical for human imaging using 15O.

Microcatheter adhesion of cyanoacrylates: comparison of normal butyl cyanoacrylate to 2-hexyl cyanoacrylate.

PURPOSE: To compare the catheter adhesion properties of 2-hexyl cyanoacrylate (Neuracryl M), a new agent, to those of normal butyl cyanoacrylate (Histoacryl), the most widely used liquid acrylic agent for microcatheter embolization. MATERIALS AND METHODS: 2-hexyl cyanoacrylate (Neuracryl M1) was tested in pure form and mixed with either a proprietary polymerization retardant/contrast agent (Neuracryl M2) or ethiodized oil (Ethiodol). Histoacryl was tested in pure form and mixed with Ethiodol. The cyanoacrylate mixtures were injected through microcatheters into wells partially filled with heparinized whole blood. The cyanoacrylates were allowed to polymerize around the microcatheter tips for 1-3 minutes. The microcatheters were then pulled at a constant rate until they were extracted from the polymerized cyanoacrylates. The peak forces required for extraction were recorded. RESULTS: The peak forces required to extract the microcatheters from either pure Histoacryl or Histoacryl mixed with 33% Ethiodol were significantly higher (P < .01; P < .05) than those for pure Neuracryl M1. When Neuracryl M1 and M2 were mixed together (as intended for clinical use), the force required for microcatheter extraction was significantly lower than that for either pure Histoacryl, Histoacryl mixed with 33% Ethiodol, or Neuracryl M1 alone (P < .01; P < .01; P < .01, respectively). The force required to extract microcatheters from the Neuracryl M1 and M2 mixture was not, however, significantly different from that of Histoacryl mixed with 50% Ethiodol. The force of extraction for the Neuracryl M1 and 50% Ethiodol mixture was below our ability to obtain precise measurements. CONCLUSION: When Neuracryl M1 was mixed with its proprietary polymerization retardant/contrast agent (Neuracryl M2), catheter adhesion was not significantly different from that of Histoacryl mixed with 50% Ethiodol, a mixture common in clinical use. When Neuracryl M1 was tested alone or mixed with Ethiodol (not intended by the manufacturer), catheter adhesion was significantly decreased relative to pure Histoacryl or equivalent mixtures of Histoacryl and Ethiodol.

ROC and localization ROC analyses of lesion detection in whole-body FDG PET: effects of acquisition mode, attenuation correction and reconstruction algorithm.

UNLABELLED: Receiver operating characteristic (ROC) and localization ROC (LROC) studies were performed to compare lesion detection at the borderline of detectability on images reconstructed with two-dimensional filtered backprojection (FBP) without attenuation correction (a common clinical protocol), three-dimensional FBP without attenuation correction, two-dimensional FBP with segmented attenuation correction and a two-dimensional iterative maximum a posteriori (MAP) algorithm using attenuation correction. Lung cancer was the model for the study because of the prominent role of 18F-fluorodeoxyglucose PET in the staging of lung cancer and the importance of lesion detection for staging. METHODS: Simulated lung cancer lesions were added to two-dimensional and three-dimensional PET data from healthy volunteers. Data were reconstructed using the four methods. Four nuclear medicine physicians evaluated the images. Detection performance with each method was compared using ROC and LROC analysis. Jackknife analysis provided estimates of statistical significance for differences across all readers for the ROC results. RESULTS: ROC and LROC results indicated statistically significant degradation in detection performance with three-dimensional acquisition (average area under ROC curves [Az] 0.51; average area under LROC curves [A(z,LROC)] 0.13) and segmented attenuation correction (average Az 0.59; average Az,LROC 0.29) compared with two-dimensional FBP without attenuation correction (average Az 0.79; average A(z,LROC) 0.54). ROC and LROC results indicated an improvement in detection performance with iterative MAP reconstruction (average Az 0.83; average A(z,LROC) 0.64) compared with two-dimensional FBP reconstruction; this improvement was not statistically significant. CONCLUSION: Use of segmented attenuation correction or three-dimensional acquisition with FBP reconstruction is not expected to improve detection of lung lesions on whole-body PET images compared with images with two-dimensional FBP without attenuation correction. The potential improvement in detection obtained with an iterative MAP reconstruction method is small compared with that obtained with two-dimensional FBP without attenuation correction.

Influence of cellulose triacetate hemodialyzers on vancomycin pharmacokinetics.

This study was designed to evaluate the pharmacokinetics of vancomycin during hemodialysis with cellulose triacetate (CT) high-flux dialyzers and to assess the influence of membrane surface area on intradialytic clearance. In a randomized crossover fashion, the pharmacokinetics of vancomycin were evaluated during dialysis with the CT 110 and CT 190 membranes. Six hemodialysis patients received 1 g of vancomycin immediately after the completion of a dialysis session, and subsequently, blood samples were obtained over a 5-day study period. On Day 3 subjects were dialyzed with CT 110 or CT 190 membranes. The mean intradialytic clearance of vancomycin was 56.7 +/- 7.5 and 100.70 +/- 10.7 mL/min with the CT 110 and CT 190 membranes, respectively (P < 0.05). Significant rebound in vancomycin serum concentrations occurred after dialysis; this rebound appeared to be complete 3 h postdialysis. On the basis of postrebound concentrations, the apparent percent removal of vancomycin was 23.6 +/- 1.2 and 25.2 +/- 8.6% for CT 110 and CT 190 membranes, respectively (not significant). Vancomycin is significantly cleared during dialysis with cellulose triacetate membranes, and its clearance is dependent on membrane surface area. Although a small supplemental dose of vancomycin could be administered after dialysis to replace drug lost during dialysis, it may be more efficient to give a larger dose of vancomycin after several dialysis periods. The determination of vancomycin removal can be used to estimate vancomycin serum concentrations as well as dosage requirements. This in conjunction with serum concentration monitoring can be used to optimize vancomycin dosing.

Simultaneous dual-isotope technetium-99m/thallium-201 cardiac SPET imaging using a projection-dependent spilldown correction factor.

A spilldown correction method is proposed for the thallium-201 window image in simultaneous dual-isotope technetium-99m/thallium-201 single-photon emission tomographic (SPET) imaging based on a single acquisition into three energy windows. In this method, images are simultaneously acquired in two standard energy windows over the 99mTc and 201Tl photopeak regions and a third spilldown window adjacent to the 201Tl window. Using a Monte Carlo simulation of SPET, the fractional amount of 99mTc and 201Tl spilldown in the 201Tl window with respect to the total counts from the spilldown window, k12, was calculated for simulated images of point sources at varying depths within a water-filled elliptical tub phantom. When applied to experimental acquisitions, k12, multiplied by the total counts from the spilldown window, is then subtracted from the 201Tl window image to produce the corrected image. However, for successful applications in SPET, k12 must be determined on a projection-by-projection basis since k12 is depth dependent. Thus, a regression relation was obtained between k12 and the total count ratio of the spilldown to 99mTc windows, k23. The spilldown correction method was applied to 201Tl photopeak images of an extended source distribution in uniform and nonuniform attenuating media with dual-isotope 99mTc/201Tl and single-isotope 201Tl. A marked improvement in image contrast was observed between the corrected and uncorrected 201Tl window images. The average count ratio of uncorrected dual-isotope 201Tl/single-isotope 201Tl was 3.08 for uniform and 2.99 for non-uniform attenuating media.(ABSTRACT TRUNCATED AT 250 WORDS)

Benefits and work-schedule options in hospital pharmacy practice.

Hospital pharmacy directors were surveyed to determine whether their departments offered specific family-related benefits and work-schedule options and how their attitudes about these options compared with those of female hospital pharmacists. Questionnaires were mailed to 300 randomly selected hospital pharmacy directors to collect the following information: vacancy rates and male:female ratios in hospital pharmacy positions, which of 13 selected benefits and work-schedule options were offered, barriers that prevented the other options from being offered, and attitudes about the listed options. The options included in the survey were selected because they represent ways of balancing home and work (e.g., maternity leave, job sharing, day care). The pharmacy directors' responses were compared with those from a similar survey of female hospital pharmacists. The usable response rate was 50.3%. Position vacancy rates ranged from 5.5% for directors to 35.8% for clinical supervisors. All full-time positions had an even distribution of men and women except for director and assistant or associate director positions. Of 13 options, only maternity leave, part-time schedules, and flexible schedules were offered by more than half of the hospitals. These three were also the only listed options that the respondents considered important in recruiting and retaining pharmacists. Barriers to offering other options included the perception that current benefits and work-schedule options were adequate, lack of staff coverage, lack of funds, and the perception that some positions are not compatible with alternative schedules. Respondents' ratings of the importance of the listed benefits and work-schedule options were significantly lower than ratings given by female hospital pharmacists in a separate survey.(ABSTRACT TRUNCATED AT 250 WORDS)

Benefits and work-schedule options for female hospital pharmacists.

Female hospital pharmacists were surveyed to determine what benefits and work-schedule options they want and how they feel about those currently offered. Questionnaires were mailed to 750 randomly selected female ASHP members to (1) collect employment and personal data, (2) determine which of 13 family-related benefits and work-schedule options were offered at their institutions, (3) assess use of and attitudes about these options, and (4) determine whether use and attitudes differ by position or parental status. The options included in the survey were selected because they represent ways of balancing home and work (e.g., job sharing, day care, parental leave). The usable response rate was 65.3%. About 59% were married and 40% had children. Most (83.3%) held full-time positions, and 36.5% held staff nonclinical positions. More than 70% of the respondents indicated that a flexible schedule, flextime, and maternity leave were important in combining personal and professional roles. Respondents indicated that many of the benefits and work-schedule options that were not routinely offered would be used to a great extent if offered. Forty percent reported satisfaction with current benefits and work-schedule options. Many surveyed female ASHP members considered their current benefits and work-schedule options less than optimal and would be interested in more flexible schedules and benefits.

Use of digital front-end electronics for optimization of a modular PET detector.

The sensitivity and resolution of a new 3D modular BGO detector system for positron emission tomography (PET) was examined in terms of its effect on the signal to noise ratio in the final image. The detector system uses custom hardware and firmware to adjust sensitivity and resolution to achieve optimum performance. This system utilizes lookup up tables (LUT) containing individually tailored positioning and energy windows to assure that events are correctly distributed among the detector elements. Without customizing the LUT, and for a common energy window, sensitivity was found to vary as much as a factor of 3.5 and resolution as much as 50% from center to edge within a single detector module. Eight different LUT configurations were tested, varying both energy window and positioning criteria. Typical intrinsic resolutions and sensitivities of the detector elements were determined in all configurations. The effect of nonuniformity of sensitivity of the detector system on image noise was evaluated by imaging uniform cylinders over a wide range of accumulated events. The effect of counting statistics in the measurement of detector sensitivities for the normalization of sinogram data was determined independently. The best of the LUT configurations provided an 16% improvement in effective sensitivity, while also providing a 10% improvement in the average intrinsic spatial resolution relative to the default configuration of the PET system.

Intraoperative beta probe: a device for detecting tissue labeled with positron or electron emitting isotopes during surgery.

An intraoperative beta probe was designed, built, and tested for detection of radio-labeled malignant tissues that has the advantage of being selectively sensitive to beta while insensitive to gamma radiation. Since beta radiation (electrons or positrons) has a short range in tissue, this probe is ideal for detecting tracers in tumors at the surface of the surgical field. This probe contains a plastic scintillation detector sensitive to beta rays and to a lesser degree some background gamma rays. A second detector counts spurious gamma rays and allows for their subtraction from the activity measured by the first detector. Sensitivity of the dual probe for I-131 and F-18 was measured to be 108 counts/s/kBq (4000 counts/s/microCi). The dual-detector probe faithfully measured the 10:1 "tumor" to background ratio of radioactivity concentrations in a simulated environment of a tumor in the presence of intense background 511 keV photons. In another phantom experiment, simulating abdominal tumor deposits with various realistic I-131 radioactive concentrations, the probe was able to accurately identify tumors of approximately 50 mg with a tumor/normal radioactivity concentration of 3/1 in 10 s.

Flumazenil: a benzodiazepine antagonist.

The mechanism of action, pharmacokinetics, and use of flumazenil in benzodiazepine overdose, as well as in the management of other disease states, are reviewed. Flumazenil interacts at the central benzodiazepine receptor to antagonize or reverse the behavioral, neurologic, and electrophysiologic effects of benzodiazepine agonists and inverse agonists. Flumazenil has been studied for a variety of indications, including as an antidote to benzodiazepine overdose and for awakening of comatose patients, reversal of sedation after surgery and in critically ill patients, and management of hepatic encephalopathy. It improves the level of consciousness in patients with benzodiazepine overdose; however, resedation may occur within one to two hours after administration, so repeated doses or a continuous infusion may be required to maintain therapeutic efficacy. It appears to be effective in reversing sedation induced by midazolam or diazepam, and case reports suggest that it is useful in awakening comatose patients, although its clinical utility is questionable. Flumazenil has proved useful in reversing conscious sedation in critically ill patients, although response may be dose dependent. Animal models indicate that flumazenil is of some benefit in hepatic encephalopathy, but until well-designed clinical trials are conducted, hepatic encephalopathy must be considered an investigational indication for flumazenil. Adverse reactions include CNS manifestations, resedation, cardiovascular effects, seizures, and alterations in intracranial pressure and cerebral perfusion pressure. Hepatic dysfunction results in a substantial change in the pharmacokinetic profile of flumazenil; therefore, dosage adjustment may be necessary in patients with hepatic dysfunction or in those receiving medications that alter flumazenil metabolism. Flumazenil has been shown to reverse sedation caused by intoxication with benzodiazepines alone or benzodiazepines in combination with other agents, but it should not be used when cyclic antidepressant intoxication is suspected. It may be beneficial after surgery when benzodiazepines have been used as part of anesthesia and after a diagnostic or surgical procedure when assessment of CNS function is necessary.

Cancer detection with whole-body PET using 2-[18F]fluoro-2-deoxy-D-glucose.

OBJECTIVE: This study was done to determine the feasibility and potential utility of whole-body PET using the glucose analogue 2-[18F]fluoro-2-deoxy-D-glucose (FDG) for the detection of primary malignancies and metastatic lesions. MATERIALS AND METHODS: This was a prospective, nonrandomized study of whole-body FDG-PET imaging carried out at a large university teaching hospital in Los Angeles, CA, U.S.A. The study group consisted of all patients referred for PET imaging (87) with a suspected diagnosis of primary or recurrent malignancy and who had eventual histological confirmation of their lesions. RESULTS: In the 87 patients, whole-body PET studies were positive (presence of focal FDG uptake relative to surrounding tissues uptake) in 61 of 70 patients (87%) with subsequent biopsy-confirmed primary or recurrent malignant lesions, including carcinomas of breast, lung, ovary, prostate, colon, urinary bladder, and gallbladder origin, as well as malignant melanoma, carcinoid, osteosarcoma, lymphoma, and spinal cord astrocytoma. The PET images revealed no focal hypermetabolism at the known site of tumor in patients with primary prostate carcinoma (two), microscopic ovarian carcinoma (two), breast carcinoma (one), low-grade carcinoid tumors (two), and one patient with recurrent microscopic osteogenic sarcoma. The PET studies detected the primary lesion in 15 of 17 patients with breast carcinoma and in 6 of 6 patients with primary lung carcinoma. Of the 17 patients with benign biopsies, 13 patients had FDG-PET studies without focal areas of uptake. CONCLUSION: Because of the high glycolytic rate of malignant tissue, the whole-body FDG-PET technique has promise in the detection of a wide variety of both primary and metastatic malignancies. The presence of FDG uptake in benign inflammatory conditions may limit the specificity of the technique. The sensitivity for the detection of malignant lesions was 87% and the positive predictive value was 94%. The whole-body FDG-PET method is promising both in determining the nature of a localized lesion and in defining the systemic extent of malignant disease.

Improved detection of focal cerebral blood flow changes using three-dimensional positron emission tomography.

Removal of the interplane septa and configuration of a typical multislice PET scanner to accept all possible coincidence lines of response leads to a fivefold increase in sensitivity. This can be of value in regional CBF studies using bolus 15O-labeled water injections, allowing the injected dose to be reduced by a factor of 4, while maintaining the same number of noise equivalent counts. Thus, for a given cumulative dose limit, four times as many studies can be performed in a single subject. Data from the three-dimensional Hoffman brain phantom, closely matched to count rates seen in human studies, show that for an identical cumulative dose, the noise in subtraction (stimulus minus baseline) images can be reduced by a factor of 2 using three-dimensional data acquisition, with appropriate fractionation of the dose. This improvement is dependent on axial position due to the sensitivity characteristics of three-dimensional scans; however, there is a significant gain in the signal-to-noise ratio (S/N) in all image planes. Studies performed in a human subject demonstrate how the factor of 2 gain in S/N leads to improved detectability of activation sites in PET subtraction images.

Results of a clinical receiver operating characteristic study comparing filtered backprojection and maximum likelihood estimator images in FDG PET studies.

The results of a receiver operator characteristic (ROC) study comparing maximum likelihood estimator (MLE) reconstructions of human FDG PET brain scan data to filtered backprojection reconstructions of the same data are reported. The purpose of the study was to determine whether MLE reconstructions would result in higher detectability of small focal lesions introduced artificially into otherwise normal scan data. One physician assisted in defining the location and intensity of the lesions and five physicians read the final images. Data from 90 datasets were used for the study. Of those, 42 were left in their original "normal" condition and 48 were modified by added lesions. All datasets were reconstructed by the two methods and submitted to the five physicians for evaluation. The results show an increase in the area under the ROC curve from approximately 0.65 for filtered backprojection to approximately 0.71 for the maximum likelihood reconstructions for four of the five observers with good statistical significance.

Correction and characterization of scattered events in three-dimensional PET using scanners with retractable septa.

Large sensitivity increases are realized in positron emission tomography when the interplane septa are removed and all lines of response acquired. Unfortunately, three-dimensional acquisition results in a large increase in scatter fraction which prevents accurate quantitation. By acquiring short two-dimensional scans prior to three-dimensional ones, scatter distributions can be estimated from differences between lines of response common to both datasets. This initial scatter distribution can be further modified to approximate scatter in the entire three-dimensional dataset. The method was validated with phantom measurements in which absolute activity concentrations were known in all compartments. Following scatter correction, a four-compartment phantom that was nonuniform in activity and density, both axially and transaxially, gave activity concentrations of 0.45 +/- 0.02, 0.31 +/- 0.02, 0.01 +/- 0.01 and 0.01 +/- 0.01 microCi/cc for compartments containing 0.43, 0.29, 0.0 (air) and 0.0 (water) microCi/cc, respectively. Thus, scatter distributions for complex sources can be estimated from image data without lengthy Monte-Carlo simulations. When activity distributions vary slowly with time, this method can be used to correct for scatter in three-dimensional patient studies.

Statistical analysis of maximum likelihood estimator images of human brain FDG PET studies.

The work presented evaluates the statistical characteristics of regional bias and expected error in reconstructions of real positron emission tomography (PET) data of human brain fluoro-deoxiglucose (FDG) studies carried out by the maximum likelihood estimator (MLE) method with a robust stopping rule, and compares them with the results of filtered backprojection (FBP) reconstructions and with the method of sieves. The task of evaluating radioisotope uptake in regions-of-interest (ROIs) is investigated. An assessment of bias and variance in uptake measurements is carried out with simulated data. Then, by using three different transition matrices with different degrees of accuracy and a components of variance model for statistical analysis, it is shown that the characteristics obtained from real human FDG brain data are consistent with the results of the simulation studies.

Whole-body positron emission tomography: Part I. Methods and performance characteristics.

Methods for whole-body PET imaging have been developed to provide a clinical tool for the detection and evaluation of primary and metastatic cancers. The axial FOV of the PET system is extended by imaging at multiple bed positions to cover the whole body. In typical rectilinear PET scans, only a small fraction of the data is collected to form two-dimensional projection images. In this work, 100% of the projection data was collected to form the two-dimensional projection images. These projection images were generated for continuous angles over 180 degrees by resorting sinogram data. In addition, tomographic images were formed by using filtered backprojection reconstruction without attenuation correction. Coronal and sagittal cuts were then extracted from the three-dimensional data set. The tomographic images were reconstructed to a resolution of 10.8 mm in all dimensions because of statistical limitations of the data. Both methods of image formation resulted in images of high quality with the tomographic reconstruction providing the highest contrast and resolution. An acquisition time of 1-2 min/bed position after a 10-mCi injection of [18F]fluoride ion or [18F]FDG was found to give a sufficient number of counts for producing images of good resolution and contrast, from a total scanning time of 32-64 min.