Yttria-stabilized zirconia ceramics is a high-performance material with excellent biocompatibility and mechanical properties, which suggest its suitability for posterior fixed partial dentures. The hypothesis under examination is that the strength and reliability of Y-TZP zirconia ceramics are affected by the inner surface grinding of crowns, and vary with the grinding parameter. Flexural strength, surface roughness, and fracture toughness were determined on samples machined by face and peripheral grinding with varied feed velocities and cutting depths. Results have been compared with those on lapped samples. Analysis of variance and Weibull parameter were used for statistical analysis. It was found that inner surface grinding significantly reduces the strength and reliability of Y-TZP zirconia compared with the lapped control sample. Co-analysis of flexural strength, Weibull parameter, and fracture toughness showed counteracting effects of surface compressive stress and grinding-introduced surface flaws. In conclusion, grinding of Y-TZP needs to be optimized to achieve the CAD/CAM manufacture of all-ceramic restorations with improved strength and reliability.

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Radiofrequency (RF)-related heating of cardiac pacemaker leads is a serious concern in magnetic resonance imaging (MRI).

It had been previously shown that an idealized version of the two-wave-vector extension of the NMR pulsed-field-gradient spin echo diffusion experiment can be used to determine the apparent radius of geometries with restricted diffusion. In the present work, the feasibility of the experiment was demonstrated in an NMR imaging experiment, in which the apparent radius of axons in white matter tissue was determined. Moreover, numerical simulations have been carried out to determine the reliability of the results. For small diffusion times, the radius is systematically underestimated. Larger gradient area, finite length gradient pulses, and a statistical distribution of radii within a voxel all have a minor influence on the estimated radius. Pulsed-field-gradient spin echo (PGSE) NMR experiments have been used to measure apparent diffusion in liquids and biological tissue (1,2). In the narrow gradient pulse limit (i.e., using infinitely short pulses), the signal obtained with the PGSE experiment corresponds to the Fourier transform of the diffusion propagator (3,4). Using this so-called q-space imaging technique, the evolution of the diffusion propagator can be measured by acquiring images or spectra with increasing delays between the pulsed diffusion gradients (5,6) and has been used to characterize the diffusion propagator in liquids (6), red blood cells (7,8), and nerve cells (5). The shape of the diffusion propagator carries information about the microstructure of the sample (e.g., biological tissue) and allows the study of compartments that are much smaller than typical sizes that can be resolved by morphological MRI methods (6,9,10).A two-wave-vector extension to the standard PGSE experiment using two pairs of pulsed gradients in a double spin echo, a so called two-wave-vector exper- iment, has been used to study flow effects in more detail than possible with a single gradient pair (11). In general, two-wave-vector experiments carry more details than obtainable through a one wave vector experiment. For example, a two-wave-vector experiment can distinguish between diffusion in different compartments and diffraction-like behavior which is caused by restricted diffusion (12).In the case of restricted diffusion, theoretical calculations by Mitra have shown that the two-wave-vector experiment can be used to determine the radius of gyration of pores using several approximations (12). The same is true for any geometry with restricted diffusion. Potential applications of this theoretical work include the measurement of the size of microscopic structures in biological tissue, as for example done in (13)(14)(15).In the present work, the theory (12) has been successfully applied to quantify the apparent cell radius in an NMR imaging experiment of biological tissue. Furthermore, it has been investigated how deviations from the idealized assumptions affect the apparent radius. Among the effects studied are finite widths of gradient pulses and radius distributions. The term apparent refers to the fact that the determination...

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Objective-Nuclear imaging of active plaques still remains challenging. Advanced atherosclerotic plaques have a strong expression of P-selectin by the endothelium overlying active atherosclerotic plaques, but not on the endothelium overlying inactive fibrous plaques. We proposed a new approach for noninvasive in vivo characterization of P-selectin on active plaques based on 68 Ga-Fucoidan, which is a polysaccharidic ligand of P-selectin with a nanomolar affinity. Approach and Results-68 Ga-Fucoidan was tested for its potential to discriminate vulnerable plaques on apolipoprotein E-deficient mice receiving a high cholesterol diet by positron emission tomography and in correlation with 17.6T MRI. Furthermore, 68 Ga-Fucoidan was evaluated on endothelial cells in vitro and ex vivo on active plaques using autoradiography. The cellular uptake rate was increased ≈2-fold by lipopolysaccharide induction. Interestingly, on autoradiography, more intensive tracer accumulation at active plaques with thin fibrous caps and high-density foam cells were observed in comparison with a weaker focal uptake in inactive fibrous plaque segments (R=1.7±0.3; P<0.05) and fatty streaks (R=2.4±0.4; P<0.01). Strong uptake of radiotracer colocalized with increased P-selectin expression and high-density macrophage. Focal vascular uptake (mean of target to background ratio=5.1±0.8) of 68 Ga-Fucoidan was detected in all apolipoprotein E-deficient mice. Anatomic structures of plaque were confirmed by 17.6T MRI. The autoradiography showed a good agreement of 68 Ga-Fucoidan uptake with positron emission tomography. Conclusions-Our data suggest that 68 Ga-Fucoidan represents a versatile imaging biomarker for P-selectin with the potential to specifically detect P-selectin expression using positron emission tomography and to discriminate vulnerable plaques in vivo. pivotal role in recruiting leukocytes to the sites of injury. 14-16This interaction is mediated by P-selectin glycoprotein ligand 1, expressed by monocytes, neutrophils, and platelets. 17,18 Most active atherosclerotic lesions remain undetected until plaque rupture and thrombosis occur. A previous study found that inflamed atherosclerotic plaques have a strong expression of P-selectin on the overlying endothelium, but much less in normal arterial endothelium or in endothelium overlying inactive fibrous plaques.19 Consequently, P-selectin is thought to be an effective biomarker for assessing the bioactivity of active plaques.Fucoidan is a synthetic sialyl-lewis X mimic, which is the natural ligand of P-selectin and is found on leukocytes. 20,21 It is mainly derived from brown seaweed with an efficient binding of P-selectin as well. 22 In previous studies, a high specific affinity of fucoidan for P-selectin was confirmed. 22We developed a novel PET tracer by an efficient introduction of the positron emitter 68 Ga into the Fucoidan moiety. The 68 Ga-Fucoidan obtained this way was used to validate the P-selectin expression in vivo on an established apolipoprotein E-deficient (apoE −/− ) m...

) mice, which spontaneously develop atherosclerotic lesions of morphology similar to those observed in humans. 11,12 Local PWV and vessel wall thickness were evaluated by timeresolved flow and morphology measurement using ultrahighfield MR microscopy at 17.6 T. In addition, we performed histological examinations to investigate structural changes of the vessel wall at the time of imaging.Background-Atherosclerosis is known to impair vascular function and cause vascular stiffening. The aim of this study was to evaluate the potential predictive role of vascular stiffening in the early detection of atherosclerosis. Therefore, we investigated the time course of early functional and morphological alterations of the vessel wall in a murine atherosclerosis model. Because initial lesions are distributed inhomogeneously in early-stage atherosclerosis, MR microscopy was performed to measure vascular elasticity locally, specifically the local pulse wave velocity and the arterial wall thickness. Methods and Results-Local pulse wave velocity and the mean arterial wall thickness were determined in the ascending and the abdominal aortae of ApoE −/− and wild-type mice. In vivo MRI revealed that baseline pulse wave velocity and morphology were similar in 6-week-old ApoE −/− and WT mice, whereas at the age of 18 weeks, local pulse wave velocity was significantly elevated in ApoE −/− mice. Significantly increased vessel wall thickness was not found in ApoE −/− mice until the age of 30 weeks. Histological analysis of the aortae of ApoE −/− and WT mice showed that increased pulse wave velocity coincided with the fragmentation of the elastic laminae in the arterial wall, which is hypothesized to induce early vascular stiffening and may be promoted by macrophage-mediated matrix degradation. Conclusions-We

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