A regularized two-tensor model fit to low angular resolution diffusion images using basis directions

PURPOSE: To resolve and regularize orientation estimates for two crossing fibers from images acquired with conventional diffusion tensor imaging (DTI) sampling schemes. MATERIALS AND METHODS: Partial volume causes artifacts in DTI. Given that routine use of high angular resolution diffusion imaging (HARDI) is still tentative, a regularized two-tensor model to resolve fiber crossings from conventional DTI datasets is presented. To overcome the problems of fitting multiple tensors, a model that exploits the planar diffusion profile in regions with fiber crossings is utilized. A regularization scheme is applied to reduce noise artifacts, which can be significant due to the relatively low number of acquired images. A set of basis directions is used to convert the two tensor model to many models of lower dimensionality. Relaxation labeling is utilized to select from amongst these models those that preserve continuity of orientations across neighbors. Revised fractional anisotropy (FA) and mean diffusivity (MD) values are computed. RESULTS: Spatial regularization improves the orientation estimates of the two-tensor model in simulations and in human data and estimates agree well with a priori anatomical knowledge. CONCLUSION: Orientational, anisotropy, and diffusivity information can be resolved in regions of two fiber crossings using full brain coverage scans acquired in less than six minutes.     

Brain tractography using Q-ball imaging and graph theory: Improved connectivities through fibre crossings via a model-based approach

Brain tractography techniques utilize a set of diffusion-weighted magnetic resonance images to reconstruct white matter tracts, non-invasively and in-vivo. Streamline tracking techniques propagate curves from a seed to imply connectivity to distal voxels. Alternative approaches have been developed that attempt to quantify connection strength between all voxels and the seed. Tractography based on graph theory is amongst them. Despite its potential, graph-based tracking through complex fibre configurations has not been extensively studied and existing methods have inherent limitations. Anatomically unlikely connections may be identified in fibre crossing regions, by assigning relatively high connection strengths to all crossing populations. In this study, we discuss these limitations and present a new approach for robustly propagating through fibre crossings, as described by the orientation distribution functions (ODFs) derived from Q-ball imaging. Each image voxel is treated as a graph node and graph arcs connect neighbouring voxels. Weights representative of both structural and diffusivity features are assigned to each arc. To account for the existence of crossing fibre populations within a voxel, complex ODFs are decomposed into components representative of single-fibre populations and an image multigraph is created. The multigraph is searched exhaustively, but efficiently, to find the strongest paths and assign connectivity strengths between a seed and all the other image voxels. A comparison with the existing graph-based tractography as well as Q-ball driven front evolution tractography is performed on simulated data, and on human Q-ball imaging data acquired from five healthy volunteers. The new approach improves the connection strengths through fibre crossing regions, reducing the strengths of paths that are less anatomically plausible.     

PFAPA syndrome in children: A meta-analysis on surgical versus medical treatment

Objective

To compare the range of medical and surgical therapies for children with PFAPA syndrome.

Methods

A literature search was performed using Medline, Embase, Ovid and Cochrane databases for studies between 1987 and 2010 that compared PFAPA treatment in children (surgical versus medical). Random-effect meta-analytical techniques were conducted for the outcome measures.

Results

The use of antibiotics and cimetidine in PFAPA syndrome are ineffective. However, there is evidence that the use of steroids is effective in the resolution of symptoms. Tonsillectomy (+/− adenoidectomy) as a treatment of PFAPA was found to be an effective intervention for resolution of symptoms (P < 0.00001). Meta-analysis of surgery versus cimetidine and surgery versus antibiotics demonstrated that surgery is a significantly more effective treatment for PFAPA syndrome. A comparison of treatment with steroids or surgery did not show any statistically significant difference, confirming the effectiveness of both therapies for the resolution of PFAPA syndrome (P = 0.83).

Conclusions

The most effective non-surgical therapy is corticosteroids. However, they do not prevent future fever cycles. The results of this meta-analysis showed that tonsillectomy (+/− adenoidectomy) is the most effective intervention for long-term resolution of PFAPA syndrome symptoms.     

Incidence and risk factors for central nervous system relapse in patients with primary mediastinal large B-cell lymphoma in the rituximab era

Central nervous system (CNS) involvement is rare in primary mediastinal large B-cell lymphoma (PMLBCL). We aimed to evaluate the incidence of CNS relapse as first treatment failure event and the effect of the induction chemotherapy regimen, central nervous system - international prognostic index (CNS-IPI) and other clinical and laboratory variables on the risk of CNS relapse in 564 PMLBCL patients treated with immunochemotherapy. Only 17 patients (3.0%) received CNS prophylaxis. During a 55-month median follow-up only 8 patients experienced CNS relapse as first event, always isolated. The 2-year cumulative incidence of CNS relapse (CI-CNSR) was 1.47% and remained unchanged thereafter. The CI-CNSR was not affected by the chemotherapy regimen (R-CHOP or R-da-EPOCH). None of the established International Prognostic Index factors for aggressive lymphomas predicted CNS relapse in PMLBCL. The 2-year CI-CNSR in patients with versus without kidney involvement was 13.3% versus 0.96% (p < 0.001); 14.3% versus 1.13% with versus without adrenal involvement (p < 0.001); and 10.2% versus 0.97% with versus without either kidney or adrenal involvement. CNS-IPI was also predictive (2-year CI-CNSR in high-risk vs. intermediate/low-risk: 10.37% vs. 0.84%, p < 0.001). However, this association may be driven mainly by kidney and/or adrenal involvement. In conclusion, in PMLBCL, CNS relapse is rare and appears to be strongly associated with kidney and/or adrenal involvement.     

Diagnostic performance of fusion of myocardial perfusion imaging (MPI) and computed tomography coronary angiography

Background  We evaluated the incremental diagnostic value of fusion images of coronary computed tomography angiography (CTA) and myocardial perfusion imaging (MPI) over MPI alone or MPI and CTA side-by-side to identify obstructive coronary artery disease (CAD > 50% stenosis) using invasive coronary angiography (ICA) as the gold standard. Methods  50 subjects (36 men; 56 ± 11 years old) underwent rest-stress MPI and CTA within 12-26 days of each other. CTAs were performed with multi-detector CT-scanners (31 on 64-slice; and 19 on 16-slice). 37 patients underwent ICA while 13 subjects did not because of low (<5%) pre-test likelihood (LLK) of disease. Three blinded readers scored the images in sequential sessions using (1) MPI alone (2) MPI and CTA side-by-side, (3) fused CTA/MPI images. Results  One or more critical stenoses during ICA were found in 28 patients and non-critical stenoses were found in 9 patients. MPI, side-by-side MPI-CTA, and fused CTA/MPI showed the same normalcy rate (NR:13/13) in LLK subjects. The fusion technique performed better than MPI and MPI and CTA side-by-side for the presence of CAD in any vessel (overall area under the curve (AUC) for fused images: 0.89; P = .005 vs MPI, P = .04 vs side-by-side MPI-CTA) and for localization of CAD to the left anterior descending coronary artery (AUC: 0.82, P < .001 vs MPI; P = .007 vs side-by-side MPI-CTA). There was a non-significant trend for better detection of multi-vessel disease with fusion. Conclusions  Using ICA as the gold standard, fusion imaging provided incremental diagnostic information compared to MPI alone or side-by-side MPI-CTA for the diagnosis of obstructive CAD and for localization of CAD to the left anterior descending coronary artery.     

Transthoracic Dobutamine Stress Echocardiography in Patients Undergoing Bariatric Surgery

BACKGROUND: The feasibility and value of transthoracic dobutamine stress echocardiography (DSE) in patients scheduled for bariatric surgery has not been investigated. METHODS: We evaluated 611 patients (86.6% female, 42 +/- 10 years, 136 +/- 18 kg, BMI 48.0 +/- 6.1 kg/m2) referred for DSE prior to surgery between February 2000 and July 2005. Mortality and major cardiovascular events (cardiac death, acute coronary syndrome, and urgent revascularization) were recorded 30-days postoperatively and at 6 months. RESULTS: Adequate baseline imaging quality was achieved in 590 patients (96.6%), with use of echocardiographic contrast agents in 426 patients (72.2%); the remaining 21 patients (3.4%) were referred for alternative preoperative testing. There were no serious adverse events during DSE, which was negative in 545 patients (92.4%). The test was inconclusive in 38 patients (6.4%), requiring alternative investigations, and positive in 7 patients (1.2%). Eventually, 595 patients proceeded to surgery: 539 with DSE-based risk stratification and 56 with risk stratification based on alternative testing. Laparoscopic procedures were employed in 77.0% of patients. There were 3 perioperative deaths, all attributed to sepsis (perioperative mortality 0.50%), but no major cardiovascular events at 30-days. One patient (evaluated prior to surgery with alternative testing) experienced an acute coronary syndrome during the following 6 months (event rate 0.17%). CONCLUSION: Transthoracic DSE is feasible and safe in morbidly obese patients undergoing bariatric surgery; implementation of echocardiographic contrast agents allows for adequate imaging quality in the majority of these patients. However, the very low risk of contemporary bariatric procedures questions the need for routine preoperative stress testing in asymptomatic patients.     

Clinical massage and modified Proprioceptive Neuromuscular Facilitation stretching in males with latent myofascial trigger points

ObjectivesTo determine the immediate effects of modified Proprioceptive Neuromuscular Facilitation (PNF) stretching (group I) versus Myofascial Trigger Point (MTrP) therapy plus modified PNF stretching (group II) in comparison to a control group receiving no treatment.DesignRandomized, assessor-blind, (3 × 4) mixed-model repeated measures.SettingUniversity laboratory.ParticipantsThirty physically active males with tight hamstrings and at least one latent MTrP on muscles innervated by the lumbosacral, sciatic, tibial and common peroneal nerves.Main outcome measuresKnee range of motion (ROM), stretch perception, pressure pain threshold (PPT) and subjective pain intensity. Outcomes were evaluated at baseline, immediately after treatment, at 10 and 30 min.ResultsSignificant changes over time occurred for group II in all outcomes (p ≤ 0.001). Group II also showed lower pain intensity scores than group I immediately post-treatment (p = 0.045) and a strong clinical effect over group I in ROM at all follow-ups (effect sizes = 0.9–1.0, p ≤ 0.05). Other differences were found between both stretching groups as compared to the control group (p ≤ 0.05).ConclusionThe results indicate immediate pre- to post-treatment benefits from MTrP therapy combined with modified PNF stretching in young and physically active males with latent MTrPs.