SPECT imaging of odor identification in schizophrenia.

Deficits in olfactory identification, despite normal odor perception, are found in some neuropsychiatric disorders, including schizophrenia. We examined if regional cerebral blood flow (rCBF) differed between schizophrenia patients and controls during odor identification, hypothesizing that these brain regions could be relevant to odor identification impairments. Eight schizophrenia and eight comparison subjects provided a baseline (picture identity matching) and activation (odor identification) SPECT scan, obtained using 99mTc-HMPAO in a low dose/high dose design. Six patients and seven controls had analyzable data. MEDX data saved in ANALYZE format for SPM 95 generated paired t-test statistical data for display in Talairach space, with rCBF changes given as Z-scores. There was no schizophrenia vs. control group difference in rCBF for the baseline picture-matching test. For odor identification, schizophrenia patients had a hypometabolic right-sided cortical region that included the frontal lobe Broca's area, superior temporal lobe, and supramarginal and angular gyri. Post hoc within-group contrasts of picture-matching vs. odor identification showed that the controls significantly increased rCBF in the right-sided inferior temporal fusiform gyrus, and bilateral hippocampi and visual association areas for the odor test. The schizophrenia group showed no rCBF differences for picture-matching compared to odor identification. Patients showed significant hypometabolism in right-sided cortical areas for odor identification. They also failed to show increased rCBF in the hippocampus and visual association area, as seen in controls for odor identification compared to picture-matching. These regions may be unique to schizophrenia or have broader implications for olfactory memory retrieval.

Changes in regional cerebral blood flow related to line bisection discrimination and visual attention using HMPAO-SPECT.

Behavioral tasks requiring visual-spatial discrimination such as line bisection are used clinically to assess right hemisphere function, yet the anatomical substrate of line bisection has yet to be elucidated by functional imaging. In the current study, nine right-handed, healthy adult subjects underwent split-dose technetium-99m-hexamethylpropylene amine oxime single photon emission tomography during performance of two visual tasks. Statistical parametric maps that represented significant changes in regional cerebral blood flow (rCBF) for each task were generated. Increases in rCBF were seen in the right dorsolateral prefrontal cortex, the insula, and the superior temporal lobe with a line-bisection discrimination task, whereas increases in the visual association areas, the posterior cingulate gyrus bilaterally, and the anterior cingulate gyrus on the right were seen with a similar control task which required sustained visual attention, but no visual spatial discrimination. We conclude that distinct areas in the nondominant hemisphere can be shown to be active during performance of line-bisection discrimination and sustained visual attention.

Adaptive changes of autoregulation in chronic cerebral hypotension with arteriovenous malformations: an acetazolamide-enhanced single-photon emission CT study.

PURPOSE: To evaluate the relationship among feeding arterial pressure, lesion size, and perfusion in cerebral cortex adjacent to cerebral arteriovenous malformations (AVMs). METHODS: Eleven patients with hemispheric AVMs underwent 99mTc hexamethyl-propyleneamine oxime single-photon emission CT before and after 1 g of acetazolamide was administered intravenously. AVM volume was estimated from MR dimensions and measured according to the method described by Pasqualin. Pressure measurements were obtained in arteries feeding the cortex adjacent to AVMs. Single-photon emission CT regions of interest were defined in cortex adjacent to the AVM and compared with contralateral regions using the Mountz method to estimate a baseline and dynamic (acetazolamide-challenged) perfusion defect volume. RESULTS: Eight of 11 patients had baseline perfusion defects, but these defects were unrelated to feeding artery pressures (y = -.06x + 9.92, r2 = .04) or the dynamic change in defect volume after acetazolamide administration (y = .01x + .02, r2 = .002). However, there was a correlation between AVM volume and the baseline defect volume (y = .75x - 1.9, r2 = .76). Five patients had increased defect volume after acetazolamide administration; 5 patients had either no change in or improvement of perfusion. Dynamic changes in defect volume were related to feeding artery pressures. CONCLUSION: Perilesional baseline perfusion defects appear to be related to lesion size and not to local arterial pressure. Cerebrovascular reserve generally was preserved, and perfusion defects appeared to be more pronounced with lower arterial pressures in feeding vessels. Although vasodilatory testing can unmask hemodynamic failure with severe local hypotension, baseline perfusion defects near the lesion and distant perfusion changes are more likely attributable to other causes such as mass-related or neurogenic changes.

Abnormal geometry of the distal radioulnar joint: MR findings.

Previously developed criteria of normal distal radioulnar joint (DRUJ) axial geometry were applied to routine magnetic resonance (MR) images of 50 wrists. All wrists lacked clinically evident DRUJ instability. An attempt to apply the three geometric criteria to seven of the cases was not possible, since the prescribed landmarks were not visible. The remaining 43 cases were retrospectively divided into a symptomatic group (25 wrists), with clinical abnormalities referable to the ulnar side of the wrist, and an asymptomatic group (18 wrists), with no such abnormalities. Abnormal DRUJ geometry was found in 12 symptomatic and 2 asymptomatic wrists. This difference between the groups is significant (p = 0.02), suggesting that many symptomatic wrists exhibit different DRUJ geometry than is found in most asymptomatic wrists.

3D reconstruction for a multi-ring PET scanner by single-slice rebinning and axial deconvolution.

A three-dimensional (3D) image reconstruction method, which was originally developed for a positron emission tomography (PET) system consisting of two rotating scintillation cameras, has now been implemented for a multi-ring PET scanner with retractable septa. The method is called 'single-slice rebinning with axial deconvolution' (SSAD), and can be described as follows. The projection data are sorted into transaxial 2D sinograms. Correction for the axial blurring is made by deconvolution in the sinograms. To obtain the axial spread functions, which depend on the activity distribution, 2D reconstruction is first made using a limited axial acceptance angle. The final 3D image is obtained by 2D reconstruction of transaxial planes. The method is simple but not approximate, has a modest memory requirement, and can be combined with different 2D techniques. Evaluations by Monte Carlo simulations and phantom studies have been made.

Fractal analysis of pulmonary arteries: the fractal dimension is lower in pulmonary hypertension.

We analyzed the spatial structure of contact radiographs of barium-filled pulmonary arteries of rats raised in room air and in two environments that induce pulmonary arterial hypertension (PAH)--hypoxia and hyperoxia. We found that the spatial structure of the pulmonary arteries was fractal in both the control and the hypertensive lungs. The fractal dimension of the pulmonary arteries of the control lungs was 1.62 +/- 0.01 (mean +/- SEM), which is greater than that of both the hypoxic lungs 1.50 +/- 0.03 (p < 0.01) and the hyperoxic lungs 1.44 +/- 0.01 (p < 0.01). There was no significant difference between the hypoxic and hyperoxic lungs. The fractal dimension may be a useful clinical index to quantify pathologic changes in the pulmonary arterial tree.

Radioimmunoimaging of human breast carcinoma xenografts in nude mouse model with 111In-labeled new monoclonal antibody EBA-1 and F(ab')2 fragments.

Radioimmunoimaging characteristics of a new monoclonal antibody EBA-1 and its F(ab')2 fragments utilizing nu/nu mice bearing human breast carcinoma xenografts are described. 111In-DTPA conjugates of EBA-1 localized with tumor/blood ratios of 0.99 +/- 0.10 (P < 0.3) and 4.65 +/- 1.60 (P < 0.05), and localization indices of 1.25 and 2.61 at 24 and 72 h, respectively. A tumor/blood ratio as high as 28.86 +/- 6.90 (P < 0.025) was obtained with EBA-1 F(ab')2 radioconjugates at 48 h. These results suggest that EBA-1 and its F(ab')2 might be useful reagents in radioimmunoimaging and radioimmunotherapy.

Left ventricular perfusion and performance from a single radiopharmaceutical and one camera.

To test the hypothesis that a small field of view portable multicrystal scintillation camera can perform stress/rest combined LV function by first-pass and perfusion studies using 99mTc-teboroxime, 26 patients with positive stress thallium studies within 2 wk and 8 healthy volunteers were studied. A 241Am point source marker over the sternum was used for motion correction. Dynamic dual-isotope (99mTc/241Am) acquisition was performed following injection of 15.6 +/- 2.3 mCi of 99mTc-teboroxime at peak treadmill exercise. Two minutes later (blood-pool clearance), while still standing on the flat treadmill, 3-4 40-sec planar images were acquired. One hour later patients were reinjected with 22.7 +/- 3.4 mCi of 99mTc-teboroxime while standing in front of the camera and the same dynamic/static acquisition protocol repeated. The planar images were interpolated from a 20 x 20 matrix to a 160 x 160 matrix, a sharpening filter and an interpolative background subtraction algorithm applied. The scans were divided into segments, each scored as normal, reversible and fixed. The agreement with thallium imaging for identifying an abnormal scan was 24/26 (92%) and for identifying abnormal vascular territories was 43/52, (83%). Fourteen patients had exercise LVEF less than 50% and all had either prior myocardial infarction, myocardial infarction plus ischemia or LAD ischemia. Diagnostic planar perfusion images and exercise LVEF can be acquired in less than 4 min using 99mTc-teboroxime and a portable multicrystal scintillation camera.

Evaluation of teleradiology for interpretation of intravenous urograms.

The diagnostic yield of a commercial teleradiology/picture archiving and communication system (ATT-Philips Comm View T/PACS) was evaluated for 100 urograms. A single image from each examination was digitized (2048 x 1684 x 12-bit pixels) and transmitted from a satellite hospital over a T-1 line using the T/PACS system. The video display of each digitized image was reviewed independently by four radiologists. The same four radiologists reviewed the original film images at a different time without knowledge of their T/PACS interpretation. There was no statistically significant difference in the sensitivity for clinical findings between T/PACS (86%) and film (89%). The false positive rate, however, was significantly higher with T/PACS than with film (44 versus 32 false positive findings per 100 films). We conclude that T/PACS of the type studied here demonstrates sufficient sensitivity for the detection of clinically important urographic findings in the emergency setting. A final reading of the original films is still necessary, however, to assure appropriate specificity.

An improved phantom for quality control of laser scanner digitizers in picture archival and communications systems.

Various quality control (QC) procedures may be used to evaluate image quality for picture archival and communications (PACS) systems. A standard PACS QC protocol applied on a regular basis is desirable to ensure optimal diagnostic performance. We describe a QC phantom designed especially to test PACS systems that acquire images by digitizing x-ray films. The phantom is a sheet of x-ray film upon which a digital test pattern is printed. Multiple parameters of image quality are tested, including resolution, contrast, gray scale, geometric distortion, and noise. Individual test patterns are incorporated to detect specific artifacts of laser scanner digitizers. As part of a regular QC protocol, the phantom provides an objective measurement of change in digital image quality over time, as well as an objective means for comparison with other systems.

Quality assurance of picture archiving communication systems with laser film digitizers.

A comprehensive quality assurance (QA) program should be implemented for all teleradiology and picture archival and communications (PACS) systems. In this report, we summarize our QA experience with a teleradiology system that includes a laser digitizer for x-ray film. A key component required for the evaluation of laser film scanners is an appropriate test pattern; digitizers should be evaluated with enhanced test patterns specifically designed for this purpose. The phantom pattern should measure high-contrast resolution, low-contrast discrimination, gray scale linearity, geometric distortion, and noise. In addition, a uniformly exposed sheet of film (approximately 0.3 optical density) serves as a good phantom for testing screen nonuniformities of viewing station monitors. It is also suggested that clinical images should be included in a QA program. Finally, it is recommended that any discrepancies in the interpretation of teleradiology images should be monitored and investigated.

A quality-control phantom for digitization of radiographs.

Quality control is fundamental to the clinical application of digital radiography. A 14 x 17-in phantom radiograph was designed to test digital image quality by measurement of five parameters: high-contrast spatial resolution, low-contrast discrimination, linearity of gray-scale response, high-frequency noise, and geometric distortion. The phantom was used to evaluate the AT&T-Philips CommView picture archival and communications system (AT&T Bell Laboratories, West Long Branch, NJ; Philips Medical Systems, Shelton, CT). High-contrast resolution was found to be greater along the diagonal axis of the system than along either the horizontal or vertical axis. Problems with low-contrast discrimination and linearity of gray-scale response were identified. This phantom provides a simple tool for daily quality assurance testing and an objective standard for comparison of image quality between different digital radiography systems.

The peanut orbit: a modified elliptical orbit for single-photon emission computed tomography imaging.

The front collimator surface of a conventional single-photon emission computed tomography (SPECT) detector system transcribing an elliptical orbit to approximate body contour could, under certain circumstances, penetrate the ellipse and make patient contact. The problem is associated both with the large front surface dimensions of tomographic cameras and the need to maintain the camera perpendicular to a radius through the axis of rotation. To aid in the development of an improved body contour orbit, software has been developed to simulate SPECT imaging systems. A major feature of the algorithms is a spatially calibrated graphic representation of the pallet, patient and orbit of the camera head. Based on computer simulations performed with this software, a modified elliptical orbit has been proposed for patient contour SPECT scanning on two different types of tomographic acquisition systems: a dual camera, rotating ring system and a single camera, multimotion stand system. This peanut orbit has the advantage of minimizing collimator patient distance, as does the elliptical orbit, but also compensates for camera motion that could potentially produce patient contact. Versions of the peanut orbit algorithms have been installed and are operational on clinical systems similar to those that were simulated. The ring-based gantry system (with cameras mounted on cantilevered arms) requires additional software to correct for translational shift in the field of view as a function of radial distance from the center of the system. This is done during uniformity correction. Standard unmodified backprojection software is used for reconstruction. The peanut orbit may represent an improved approach to body contour imaging in rotational SPECT.

Effect of isolated proximal coronary stenotic lesions on distal myocardial perfusion during exercise.

This study tested the hypothesis that the absolute dimension of a coronary stenotic lesion is a more important determinant of its hemodynamic effect on regional myocardial perfusion during exercise than is relative percent stenosis. In 31 patients with an isolated lesion of the left anterior descending coronary artery, regional myocardial perfusion was determined from thallium-201 scans recorded in the left anterior oblique projection after symptom-limited treadmill exercise. Thallium-201 uptake in the distribution of the left anterior descending coronary artery was expressed as a ratio of thallium-201 uptake in the left circumflex artery distribution. Percent area stenosis, minimal cross-sectional area and mean diameter of each stenotic lesion were measured by computer-assisted cinevideodensitometric analysis of projected coronary arteriograms digitized in a 512 X 512 pixel matrix with 256 gray levels. Thallium-201 uptake in the left anterior descending coronary artery distribution, expressed as a ratio, correlated poorly (r = 0.65) with relative percent stenosis, but correlated significantly (r = 0.83; p less than 0.05) with absolute lesion area. For all 16 patients with reduced regional perfusion in the left anterior descending coronary artery distribution during exercise, lesion cross-sectional area was less than 1.8 mm2 (mean 0.9 +/- 0.6); for 13 of the 15 patients with normal distal perfusion, the area of the stenotic lesion was greater than 1.8 mm2 (mean 2.7 +/- 0.7; p less than 0.001). Percent coronary stenosis failed to predict flow-limiting lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Considerations in the purchase of a nuclear medicine computer system.

Selection of a nuclear medicine computer system is a process that should be approached with care and forethought. The general scheme should be to define your needs and constraints, determine what is available, investigate the leading candidates, make a site visit, and, finally, submit an order. Through a series of discussions between members of the Computer Council of the Society of Nuclear Medicine and representatives from the manufacturers of computer systems, a set of important considerations emerged, which are reported in this paper. This paper is not intended to be a step-by-step guideline to the purchase of a computer system. Rather, it is a set of concepts and considerations with which the prospective purchaser should be familiar before undertaking such a purchase.

Comparison of bone density measurements from different skeletal sites.

Absorptiometric measurements from multiple sites in 212 consecutive patients were examined to determine the interrelationships among bone mineral content values obtained from the lumbar spine, hip, and forearm. Dual photon absorptiometry was used to examine the spine, femoral neck, Ward's triangle, and greater trochanter while the radius and ulna were studied with single photon absorptiometry. All studies were performed on the same day. Concurrent measurements were available for the spine and hip in 197 patients, for the spine and forearm in 151 patients, and at all three sites for 146 patients. Variable degrees of correlation were found among the mineral content values from the six sites, with r values ranging from 0.40 to 0.93. The femoral neck and Ward's triangle showed the highest degree of correlation (r = 0.93); the ulna and lumbar spine demonstrated the poorest correlation (r = 0.40). Relationships between distant anatomic sites exhibited a large amount of variability (large standard error of the estimate) even when highly correlated. Useful predictions of bone mineral content could be obtained only for sites in close proximity. These results suggest that bone mineral content determinations in the upper extremities by single photon absorptiometry may not be useful for predicting mineralization in clinically more significant areas such as the lumbar spine and hip.

Evaluation of metastatic melanoma with planar and SPECT scintigraphy using ZME 018 and 96.5 radiolabeled monoclonal antibodies.

To determine the feasibility of using serial injections of monoclonal antibodies (MoAbs; 96.5 and ZME 018) to evaluate metastases of malignant melanoma, 11 patients were studied. Each patient received two injections of antibody 7 days apart and were imaged 7 days after injection. Serum for human antimouse antibody (HAMA) was obtained immediately prior to injection of MoAb and 7-10 days after the second injection. Six patients were evaluated with both planar and single photon emission computed tomography (SPECT) images. Planar imaging alone was compared with SPECT alone and with planar and SPECT imaging in combination. In seven patients with 19 lesions, 96.5 and ZME 018 each identified eight lesions. In no case did one antibody identify a lesion missed by the other. In the six patients on whom SPECT imaging was performed, 14 confirmed and six suspected lesions were identified. Using planar imaging alone, only 12 confirmed and one suspected lesion were identified. HAMA titers rose significantly (0.32 optical density (O.D.) units prior to injection to 1.28 O.D. units on day 14, P less than 0.001). Allergic reactions occurred during the second injection in two patients. One of these demonstrated elevated HAMA titers and one did not. The preliminary data suggest that monoclonal antibody imaging may be aided by SPECT and that a normal HAMA titer does not preclude an allergic reaction.

Evaluation of a cinevideodensitometric method for measuring vessel dimensions from digitized angiograms.

A cinevideodensitometric method for measuring the dimensions of small vessels by computer analysis of digitized cineangiograms was developed and validated in radiographic phantom models. With this method, which is based on full-width-at-half-maximum analysis of videodensitometric profile curves, the diameters of contrast-filled plexiglass cylinders ranging from 1.78 mm to 4.14 mm in diameter were measured to within 2% mean error. The theoretical basis for this method of cinevideodensitometric analysis is provided.

Quantitative analysis of coronary arteriograms by microprocessor cinevideodensitometry.

A rapid microprocessor technique for measuring the cross-sectional area, diameter, and relative percentage stenosis of coronary atherosclerotic lesions by cinevideodensitometric analysis was developed and validated. Video images of projected 35-mm coronary arteriographic cine frames were analyzed from cinevideodensitometric profile curves recorded for the catheter shaft, normal artery, and stenotic segment. In radiographic phantom studies of calibrated, contrast-filled, plexiglass cylinders, cinevideodensitometric measurements correlated linearly with percentage relative stenosis (r = 0.98; SEE = 4.1%), diameter (r = 0.99; SEE = 0.12 mm), and cross-sectional area (r = 0.99; SEE = 0.32 mm2). In postmortem studies of two patients dying after coronary arteriography, cross-sectional areas of arterial segments measured by cinevideodensitometry correlated well (r = 0.99; SEE = 0.71 mm) with areas of acrylic resin casts of the coronary arteries. Intraobserver variability (r = 0.99; SEE = 2.6%) and interobserver variability (r = 0.96; SEE = 5.3%) of cinevideodensitometric measurements of coronary arteriograms were low. Additionally, percentage relative stenosis measured in the right anterior oblique projection correlated well with measurements in the left anterior oblique projection (r = 0.98; SEE = 0.11 mm2) of patients with eccentric stenotic lesions. Lastly, cinevideodensitometric measurements were significantly (p less than 0.05) more reproducible than caliper measurements. This inexpensive dedicated microprocessor system provides rapid cinevideodensitometric measurements of coronary arterial dimensions, without requiring manual tracing of arterial segments or the major expense of a main-frame computer system.