Performance measurement of the microPET focus 120 scanner.

The microPET Focus 120 scanner is a third-generation animal PET scanner dedicated to rodent imaging. Here, we report the results of scanner performance testing. METHODS: A (68)Ge point source was used to measure energy resolution, which was determined for each crystal and averaged. Spatial resolution was measured using a (22)Na point source with a nominal size of 0.25 mm at the system center and various off-center positions. Absolute sensitivity without attenuation was determined by extrapolating the data measured using an (18)F line source and multiple layers of absorbers. Scatter fraction and counting rate performance were measured using 2 different cylindric phantoms simulating rat and mouse bodies. Sensitivity, scatter fraction, and noise equivalent counting rate (NECR) experiments were repeated under 4 different conditions (energy window, 250 approximately 750 keV or 350 approximately 650 keV; coincidence window, 6 or 10 ns). A performance phantom with hot-rod inserts of various sizes was scanned, and several animal studies were also performed. RESULTS: Energy resolution at a 511-keV photopeak was 18.3% on average. Radial, tangential, and axial resolution of images reconstructed with the Fourier rebinning (FORE) and filtered backprojection (FBP) algorithms were 1.18 (radial), 1.13 (tangential), and 1.45 mm full width at half maximum (FWHM) (axial) at center and 2.35 (radial), 1.66 (tangential), and 2.00 mm FWHM (axial) at a radial offset of 2 cm. Absolute sensitivities at transaxial and axial centers were 7.0% (250 approximately 750 keV, 10 ns), 6.7% (250 approximately 750 keV, 6 ns), 4.0% (350 approximately 650 keV, 10 ns), and 3.8% (350 approximately 650 keV, 6 ns). Scatter fractions were 15.9% (mouse phantom) and 35.0% (rat phantom) for 250 approximately 750 keV and 6 ns. Peak NECR was 869 kcps at 3,242 kBq/mL (mouse phantom) and 228 kcps at 290 kBq/mL (rat phantom) at 250 approximately 750 keV and 6 ns. Hot-rod inserts of 1.6-mm diameter were clearly identified, and animal studies illustrated the feasibility of this system for studies of whole rodents and mid-sized animal brains. CONCLUSION: The results of this independent field test showed the improved physical characteristics of the F120 scanner over the previous microPET series systems. This system will be useful for imaging studies on small rodents and brains of larger animals.     

Saccular Aneurysm of the Azygos Anterior Cerebral Artery: Three Case Reports

The azygos anterior cerebral artery, a rare anomaly in the circle of Willis in which only a single vessel supplies the medial aspects of both anterior cerebral hemispheres, is closely associated with saccular aneurysms. We present three cases of azygos anterior cerebral artery aneurysms among the 781 cerebral aneurysms surgically treated at our institution in an 11-year period. These three cases all involved elderly women who presented with subarachnoid hemorrhage. Conventional cerebral angiography and CT angiography revealed small saccular aneurysms at the distal ends of the azygos anterior cerebral arteries. These aneurysms were clipped successfully using a bifrontal interhemispheric approach. Hence, the pathogenesis of these particular aneurysms relating to hemodynamic change, associated anomalies, and surgical pitfalls is discussed with review of literature.     

Causes of financial difficulty in Catholic hospitals

A study was conducted to see which attributes contribute most to financial distress in Catholic hospitals. The 1982 total population of U.S. Catholic hospitals was examined. The reason for financial distress was found to be more related to management attributes than to financial variables.     

Dynamic MRI with projection reconstruction and KWIC processing for simultaneous high spatial and temporal resolution.

A method for dynamic imaging in MRI is presented that enables the acquisition of a series of images with both high temporal and high spatial resolution. The technique, which is based on the projection reconstruction (PR) imaging scheme, utilizes distinct data acquisition and reconstruction strategies to achieve this simultaneous capability. First, during acquisition, data are collected in multiple undersampled passes, with the view angles interleaved in such a way that those of subsequent passes bisect the views of earlier ones. During reconstruction, these views are weighted according to a previously described k-space weighted image contrast (KWIC) technique that enables the manipulation of image contrast by selective filtering. Unlike conventional undersampled PR methods, the proposed dynamic KWIC technique does not suffer from low image SNR or image degradation due to streaking artifacts. The effectiveness of dynamic KWIC is demonstrated in both simulations and in vivo, high-resolution, contrast-enhanced imaging of breast lesions.     

Flavonoids from the leaves ofRhododendron brachycarpum

The flavonoids isolated from the leaves ofRhododendron brachycarpum, were identified as quercetin, avicularin, quercitrin and hyperin.     

β-Adrenergic agonists suppress chronic/relapsing experimental allergic encephalomyelitis (CREAE) in Lewis rats

Chronic/relapsing experimental allergic encephalomyelitis (CREAE) serves as an animal model for relapsing/remitting multiple sclerosis. Treatment with the β-adrenergic agonist isoproterenol or the β₂-adrenergic agonist terbutaline significantly suppressed both the first acute attack and the number of relapses in CREAE Lewis rats. The number of relapses was decreased even when treatment with β-adrenergic agonist was started after the onset of the first acute attack of CREAE. β-adrenergic receptor number was increased significantly on splenocytes from CREAE rats as compared to healthy controls or CFA-injected rats. Terbutaline treatment of CREAE rats lowered the splenocyte receptor number to normal values.     

Comparison of the biomechanical effect of posterior condylar offset and kinematics between posterior cruciate-retaining and posterior-stabilized total knee arthroplasty

Background

The effect of the changes in the femoral posterior condylar offset (PCO) on anterior–posterior (AP) translation and internal–external (IE) rotation in cruciate-retaining (CR) and posterior-stabilized (PS) total knee arthroplasty (TKA) remains unknown. The purpose of this study was to compare the kinematics in CR and PS TKA with respect to the difference in prosthetic design and PCO change through a computational simulation.

Effects of x-ray and CT image enhancements on the robustness and accuracy of a rigid 3D/2D image registration

A rigid body three-dimensional/two-dimensional (3D/2D) registration method has been implemented using mutual information, gradient ascent, and 3D texturemap-based digitally reconstructed radiographs. Nine combinations of commonly used x-ray and computed tomography (CT) image enhancement methods, including window leveling, histogram equalization, and adaptive histogram equalization, were examined to assess their effects on accuracy and robustness of the registration method. From a set of experiments using an anthropomorphic chest phantom, we were able to draw several conclusions. First, the CT and x-ray preprocessing combination with the widest attraction range was the one that linearly stretched the histograms onto the entire display range on both CT and x-ray images. The average attraction ranges of this combination were 71.3 mm and 61.3 deg in the translation and rotation dimensions, respectively, and the average errors were 0.12 deg and 0.47 mm. Second, the combination of the CT image with tissue and bone information and the x-ray images with adaptive histogram equalization also showed subvoxel accuracy, especially the best in the translation dimensions. However, its attraction ranges were the smallest among the examined combinations (on average 36 mm and 19 deg). Last the bone-only information on the CT image did not show convergency property to the correct registration.     

Malignant rhabdoid tumor of the kidney--a case report.

Malignant rhabdoid tumor is a distinct renal tumor in children. It had been regarded as a rhabdomyosarcomatoid variant of Wilms' tumor, but it is now thought as a separate entity. We report a case of malignant rhabdoid tumor of the kidney in a 26-month-old girl who presented with a left abdominal mass. Grossly, a large mass in the lower pole of the left kidney was well encapsulated and measured 4 x 4 x 3.5cm. On cross section, it was soft and yellowish white and showed multifocal necroses. The mass was mainly located in the medial medullary portion and compressed the renal pelvis laterally. Microscopically, the tumor masses were hypercellular and anaplastic without definite blastematous elements. In larger portion, the tumor cells had abundant eosinophilic cytoplasm and hyaline globules. In addition to the classic "rhabdoid" feature, alveolar, sclerosing, and lymphomatous patterns were seen. Ultrastructurally, tumor cells with abundant cytoplasm contained tangles of intermediate filament corresponding to vimentin in immunostaining.