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.

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.

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.

A new coregistration software package, Neuro900 Image Coregistration software (Strichman Medical Equipment), has been developed specifically for nuclear medicine. With this algorithm, the correlation coefficient is maximized between volumes generated from sets of transaxial slices. No localization markers or segmented surfaces are needed. The coregistration program was evaluated for translational and rotational registration accuracy. A Tc-99m HM-PAO split-dose study (0.53 mCi low dose, L, and 1.01 mCi high dose, Il) was simulated with a Hoffman Brain Phantom with five fiducial markers. Translation error was determined by a shift in image centroid, and rotation error was determined by a simplified two-axis approach. Changes in registration accuracy were measured with respect to: 1) slice spacing, using the four different combinations LL, LH, HL, HH, 2) translational and rotational misalignment before coregistration, 3) changes in the step size of the iterative parameters. In all the cases the algorithm converged with only small difference in translation offset, theta and phi. At 6 mm dice spacing, translational errors ranged from 0.9 to 2.8 mm (system resolution at 100 mm, 6.8 mm). The converged parameters showed little sensitivity to count density. In addition the correlation coefficient increased with decreasing iterative step size, as expected. From these experiments, we found that this algorithm based on the maximization of the; correlation coefficient between studies was an accurate way to coregister SPECT brain images.

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.

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.

Crosstalk components (XC) present in one or both energy windows (EWs) in dual radionuclide images can influence the detectability of cold defects and overestimate areas of hyperperfusion. Changes in lesion contrast due to the presence of crosstalk photons and correction methods were evaluated for combinations of radionuclides. Monte Carlo simulations of SPECT and planar imaging of a brain phantom containing 10 lesions ranging in size from 1 to 12 cm{sup 2} were run for Tc-99m, Xe-133, Tl-201 and I-123. Simulations of the gray and white matter compartments and lesions were run individually to allow greater flexibility in evaluating different radionuclide uptake distributions. Simulations of image acquisition at 15 EWs, corresponding to the baseline settings and EWs commonly used for imaging all four radionuclides, were recorded for each radionuclide. The system energy resolution (ER) was set at 1% intervals between 6 and 14%. XCs were calculated for: (1) Tc and I with 4:1 activity ratio (AR) of Tc/I; (2) Tc and Tl with a 5:1 AR and (3) Tc and Xe with a 2:1 and 4:1 AR. Cold defects of 10 to 60% with Xe, Tl and I were seen as 3 to 45% defects due to XC from Tc whenmore » similar distribution and defect size were assumed for both radionuclides. Large changes in lesion contrast were observed when multiple lesions with increased (hyperperfused regions) and decreased activity were used in the same study especially if cold lesions on Xe, Tl and I images, appear as regions with increased activity uptake on the Tc study. Image contrast improved when images recorded in the 100-110 keV EW were used to estimate and correct for Tc XC in the Xe- and Tl-studies; 10-60% defects were seen as defect of 6-55%. The study shows that large changes in lesion contrast and detectability due to XC can be corrected using a third EW in dual radionuclide imaging of Tc-Xe and Tc-Tl.« less

A Monte Carlo simulation study was conducted to evaluate the feasibility and validity of simultaneous dual-radionuclide imaging of tracers (Tc-99m, Tl-201 and Xe-133) using multi-window acquisition. Dual radionuclide imaging would allow simultaneous emission and transmission imaging, viewing of paired tracers during the same clinical and physiologic state, and eliminate problems in image registration incurred in comparing images from sequential imaging studies. Energy spectra, planar and SPECT images were obtained for a point source placed at various depths in a water filled cylinder and a brain phantom with and without lesions. The system energy resolution was set at 1% intervals between 6 and 14%. Simulations of image acquisition at 16 energy windows (EW) were recorded for each radionuclide. The study shows that large changes in lesion contrast and detectability due to cross-talk can be corrected using a third EW in dual radionuclide imaging of Tc-Xe and Tc-Tl

A three-dimensional image reconstruction method, originally developed for a rotating PET scanner, has been implemented for a multi-ring PET scanner with retractable septa. The method is based on single slice rebinning and axial deconvolution of an activity distribution dependent spread function. The final 3D image is obtained by 2D reconstruction of transaxial planes. The axial deconvolution is made using an iterative Landweber-type algorithm. In this work the authors have investigated two alternative approaches for the deconvolution step; (1) using all the data in the calculation; and (2) deconvolving only the cross-plane events. The resolution and noise-level has been studied for different number of iterations using the two approaches. The authors conclude that the second approach results in a noise-level that is more stable with increasing number of iterations. However, one single iteration seems to be sufficient to obtain an axial resolution comparable to the one in 2D acquisition mode

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.

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.