Automatic algorithm for correcting motion artifacts in time-resolved two-dimensional magnetic resonance angiography using convex projections.

Time-resolved contrast enhanced magnetic resonance angiography (MRA) may suffer from involuntary patient motion. It is noted that while MR signal change associated with motion is large in magnitude and has smooth phase variation in k-phase, signal change associated with vascular enhancement is small in magnitude and has rapid phase variation in k-space. Based upon this observation, a novel projection onto convex sets (POCS) algorithm is developed as an automatic iterative method to remove motion artifacts. The presented POCS algorithm consists of high-pass phase filtering and convex projections in both k-space and image space. Without input of detailed motion knowledge, motion effects are filtered out, while vasculature information is preserved. The proposed method can be effective for a large class of nonrigid motions, including through-plane motion. The algorithm is stable and converges quickly, usually within five iterations. A double-blind evaluation on a set of clinical MRA cases shows that a completely unsupervised version of the algorithm produces significantly better rank scores (P=0.038) when compared to angiograms produced manually by an experienced radiologist.     

Influence of surface modification techniques on shear bond strength between different zirconia cores and veneering ceramics

PURPOSE

Veneering porcelain might be delaminated from underlying zirconia-based ceramics. The aim of this study was the evaluation of the effect of different surface treatments and type of zirconia (white or colored) on shear bond strength (SBS) of zirconia core and its veneering porcelain.

MATERIALS AND METHODS

Eighty zirconia disks (40 white and 40 colored; 10 mm in diameter and 4 mm thick) were treated with three different mechanical surface conditioning methods (Sandblasting with 110 µm Al₂O₃ particle, grinding, sandblasting and liner application). One group had received no treatment. These disks were veneered with 3 mm thick and 5 mm diameter Cercon Ceram Kiss porcelain and SBS test was conducted (cross-head speed = 1 mm/min). Two and one way ANOVA, Tukey''s HSD Past hoc, and T-test were selected to analyzed the data (α=0.05).

RESULTS

In this study, the factor of different types of zirconia ceramics (P=.462) had no significant effect on SBS, but the factors of different surface modification techniques (P=.005) and interaction effect (P=.018) had a significant effect on SBS. Within colored zirconia group, there were no significant differences in mean SBS among the four surface treatment subgroups (P=0.183). Within white zirconia group, "Ground group" exhibited a significantly lower SBS value than "as milled" or control (P=0.001) and liner (P=.05) groups.

CONCLUSION

Type of zirconia did not have any effect on bond strength between zirconia core and veneer ceramic. Surface treatment had different effects on the SBS of the different zirconia types and grinding dramatically decreased the SBS of white zirconia-porcelain.     

Solute-free water excretion and electrolyte-free water excretion are better terms than solute-free water clearance and electrolyte-free water clearance

International Urology and Nephrology -     

Serotonin transporter binding as a possible predictor of one-year remission in major depressive disorder

Objective

Lower serotonin transporter (5-HTT) binding (BP_P = f_PB_avail/K_D) is reported during a major depressive episode (MDE) compared to healthy controls. Higher 5-HTT binding in the diencephalon has previously been associated with acute response to antidepressant treatment. We assessed baseline 5-HTT binding as a predictor of one-year remission from a MDE, examining binding in brain regions implicated in the pathophysiology of major depressive disorder (MDD).

Methods

5-HTT binding was quantified using positron emission tomography (PET) with [¹¹C]McN5652 in 19 currently depressed subjects with MDD and 41 healthy controls. Depressed subjects received open, naturalistic antidepressant treatment. Remission status was determined one year after PET scan and treatment initiation.

Results

Significant differences in 5-HTT binding among the three groups (healthy controls, remitters, and non-remitters) were observed in a linear mixed-effects model. Post hoc, non-remitters had lower 5-HTT binding than controls in midbrain, amygdala, and anterior cingulate. Remitters did not differ significantly from controls or non-remitters in 5-HTT binding. Remitters did not differ from non-remitters in clinical characteristics apart from greater family history of depression among non-remitters. A logistic regression model fit to determine the capacity of baseline 5-HTT binding to predict remission status at one year yielded a coefficient that was suggestive but not significant (p = 0.057).

Limitations

The small sample size and heterogeneous treatments received reduced statistical power to detect differences in binding based on clinical outcome.

Conclusions

Lower pretreatment 5-HTT binding may be predictive of non-remission from major depression following one year of naturalistic antidepressant treatment. Future studies using standardized treatment are warranted.     

Is dopamine agonist therapy associated with developing pathological gambling in Parkinson's disease patients?

In recent years, improving the quality of life and the level of functioning in Parkinson's disease patients has become the main challenge of all therapeutic protocols for this chronic disease. Hence, identifying comorbid psychiatric conditions is the ambition of many studies in the field. To date, a few research studies have investigated the development of problem gambling as a potential side effect of dopamine agonist medications. However, there are still controversies among experts in the field. Thus far, published reports have been able to neither demonstrate the extent of risk for gambling-related problems nor study the correlation of dosage with this potential adverse effect among Parkinson's disease patients treated with dopaminergic medications. In fact, prospective epidemiologic studies are needed to technically estimate the incidence rate and the relative risk of pathological gambling among patients with Parkinson's disease and to determine the correlation between dosage of these medications and the development of pathological gambling.     

Diffusion Entropy: A Potential Neuroimaging Biomarker of Bipolar Disorder in the Temporal Pole

Despite much research, bipolar depression remains poorly understood, with no clinically useful biomarkers for its diagnosis. The paralimbic system has become a target for biomarker research, with paralimbic structural connectivity commonly reported to distinguish bipolar patients from controls in tractography‐based diffusion MRI studies, despite inconsistent findings in voxel‐based studies. The purpose of this analysis was to validate existing findings with traditional diffusion MRI metrics and investigate the utility of a novel diffusion MRI metric, entropy of diffusion, in the search for bipolar depression biomarkers. We performed group‐level analysis on 9 un‐medicated (6 medication‐naïve; 3 medication‐free for at least 33 days) bipolar patients in a major depressive episode and 9 matched healthy controls to compare: (1) average mean diffusivity (MD) and fractional anisotropy (FA) and; (2) MD and FA histogram entropy—a statistical measure of distribution homogeneity—in the amygdala, hippocampus, orbitofrontal cortex and temporal pole. We also conducted classification analyses with leave‐one‐out and separate testing dataset (N = 11) approaches. We did not observe statistically significant differences in average MD or FA between the groups in any region. However, in the temporal pole, we observed significantly lower MD entropy in bipolar patients; this finding suggests a regional difference in MD distributions in the absence of an average difference. This metric allowed us to accurately characterize bipolar patients from controls in leave‐one‐out (accuracy = 83%) and prediction (accuracy = 73%) analyses. This novel application of diffusion MRI yielded not only an interesting separation between bipolar patients and healthy controls, but also accurately classified bipolar patients from controls.