Computer aided analysis of breast MRI enhancement kinetics using mean shift c lustering and multifeature iterative region of interest selection

Purpose:

To evaluate automatic characterization of a breast MR lesion by its spatially coherent region of interest (ROI).

Materials and Methods:

The method delineated 247 enhancing lesions using Otsu thresholding after manually placing a sphere. Mean Shift Clustering subdivided each volume, based on features including pharmacokinetic parameters. An iteratively trained classifier to predict the most suspicious ROI (IsR) was used, to predict the malignancy likelihood of each lesion. Performance was evaluated using receiver operator characteristic (ROC) analysis, and compared with a previous prototype. IsR was compared with noniterative training. The effect of adding BI‐RADS? morphology (from a radiologist) to the classifier was investigated.

Results:

The area under the ROC curve (AUC) was 0.83 (95% confidence interval [CI] of 0.77–0.88), and was 0.75 (95%CI = 0.68–0.81; P = 0.029) without pharmacokinetic features. IsR performed better than conventional selection, based on one feature (AUC 0.75, 95%CI = 0.68–0.81; P = 0.035). With morphology, the AUC was 0.84 (95%CI = 0.78–0.88) versus 0.82 without (P = 0.40).

Conclusion:

Breast lesions can be characterized by their most suspicious, contiguous ROI using multi‐feature clustering and iterative training. Characterization was improved by including pharmacokinetic modeling, while in our experiments, including morphology did not improve characterization. J. Magn. Reson. Imaging 2012;36:1104–1112. © 2012 Wiley Periodicals, Inc.

     

Routine coagulation assays underestimate levels of antithrombin‐dependent drugs but not of direct anticoagulant drugs in plasma from patients with cirrhosis

There is increasing recognition that thrombotic complications may occur in patients with cirrhosis, and literature on antithrombotic treatment in these patients is rapidly emerging. Due to extensive haemostatic changes in patients with cirrhosis, careful monitoring of anticoagulant therapy may be required. Recent data suggest that plasma levels of low molecular weight heparin (LMWH) are substantially underestimated by the anti‐activated factor X (anti‐Xa) assay in patients with cirrhosis. We studied the in vitro recovery of antithrombin (AT)‐dependent and –independent anticoagulant drugs in plasma from 26 patients with cirrhosis and 30 healthy controls and found substantially reduced anti‐Xa levels when AT‐dependent anticoagulant drugs were added to the plasma of patients with cirrhosis. LMWH (0·2 U/ml) had the poorest recovery in plasma from patients with cirrhosis (0·13 ± 0·06 U/ml, compared to 0·23 ± 0·03 U/ml in controls, P < 0·0001), followed by unfractionated heparin and fondaparinux. In contrast, the recovery of rivaroxaban and dabigatran was identical between patients and controls. These data suggest that the anti‐Xa assay cannot be used to monitor AT‐dependent anticoagulant drugs in patients with cirrhosis, as it substantially underestimates drug levels. The direct factor Xa and IIa inhibitors, however, may be monitored through the respective anti‐Xa and anti‐IIa assays in patients with cirrhosis.     

The Irrelevant Speech Effect and the Level of Interference in Aging

In general, no disproportionate detrimental effects of irrelevant background speech on cognition are found in aging individuals, although this is predicted by the inhibitory view of aging. This may be due to the nature of the primary task (most studies involve a verbal learning task) or the cognitive level at which irrelevant speech interferes with this task. In this study, the irrelevant speech effect on a numeric working memory task was investigated among 20 young (M = 21.8 years) and 20 older (M = 68.1 years) native Dutch individuals. Level of interference (LOI) was manipulated by presenting white noise (no interference), Russian words (low interference), Dutch words (phonological interference), and Dutch numbers (semantic interference) in the background. Results showed that reaction time increases as a function of LOI relative to silence, whereas accuracy remains unaffected. However, no interaction between LOI and age group was found, which suggests that the elderly were not disproportionately affected by an increased level of interference. These results are discussed in the light of the inhibitory view of aging.     

Subjective sleep problems in later life as predictors of cognitive decline. Report from the Maastricht Ageing Study (MAAS).

BACKGROUND: Although biological sleep criteria seem to be associated with cognitive changes in older people, it is not clear if subjective sleep parameters are related to cognitive decline in later life. OBJECTIVES: The aim of this study was to determine whether subjective sleep complaints in a population-based sample of 838 middle aged and older adults (>or= 50 years) predicted cognitive decline over a period of 3 years. METHODS: Sleep complaints at baseline, assessed with the subscale Sleep Problems of the Symptoms Checklist-90, were used as a predictor variable. Cognitive performance at follow-up, measured with the Mini Mental Status Examination, was employed as a dependent variable. RESULTS: Controlling for the effects of age, gender, length of follow-up interval, systemic diseases, and cognitive function at baseline, subjective sleep complaints were negatively associated with cognitive performance at follow-up. CONCLUSION: Subjective sleep complaints predict cognitive decline in middle aged and older adults. Mechanisms behind the effect of subjective sleep complaints on cognitive performance are discussed.     

The effect of acute tryptophan depletion on the BOLD response during performance monitoring and response inhibition in healthy male volunteers

Rationale Serotonin (5-HT) was implicated in both clinical and experimental studies in flexible, goal-directed behavior. However, the way in which 5-HT manipulations affect brain activation patterns underlying different subprocesses of cognitive flexibility remains largely unknown.Objectives The aim of this study was to investigate the effect of a transient lowering of 5-HT on brain activation during performance monitoring and response inhibition.Materials and methods We used acute tryptophan depletion (ATD), a well-known method to reduce central 5-HT, to investigate the effect of a transient lowering of 5-HT on the blood-oxygen-level dependent (BOLD) response in an event-related functional MRI study. Thirteen healthy male volunteers performed a modified Go/NoGo task in a counterbalanced, placebo-controlled, within-subject design.Results ATD significantly lowered plasma tryptophan but did not affect mood and cognitive performance. ATD decreased the BOLD response in the dorsomedial prefrontal cortex (BA 8) during performance monitoring. ATD did not affect the BOLD response during response inhibition.Conclusions This study provides more evidence for the suggested role of 5-HT in performance monitoring. Because ATD studies have revealed inconsistent effects of ATD on performance and on brain activation, it was suggested that gender and personality traits are important variables to take into account for future research.     

Neurocognitive fitness in the sub-acute stage after mild TBI: the effect of age

Objective: Age is assumed to be a negative prognostic factor in recovery from moderate-to-severe traumatic brain injury (TBI). Little is known on cognitive performance after mild TBI in relation to age in the sub-acute stage after injury.

Method: Ninety-nine mild TBI subjects (age 15-75) were compared with 91 healthy control subjects (age 14-74) in a case-control design. Patients were matched on age, sex and level of education, with control subjects. Mean interval between injury and cognitive assessment was 13 days. Neurocognitive test battery contained tests of verbal memory, selective attention, general speed of information processing and verbal fluency.

Results: An overall effect was found of a single mild TBI on neurocognitive performance in the sub-acute stage after injury. Age did not add significantly to the effect of mild TBI on cognitive functioning.

Conclusion: Patients suffering from mild TBI are characterized by subtle neurocognitive deficits in the weeks directly following the trauma. The notion that elderly subjects have a worse outcome in the sub-acute period after mild TBI is at least not in line with the results of this study.     

Computerized three-dimensional localization of prostate cancer using contrast-enhanced power Doppler and clustering analysis

OBJECTIVE: To evaluate the potential benefit of semiautomated localization of prostate cancer using clustering analysis on three-dimensional (3-D) contrast-enhanced power Doppler images. METHODS: Thirty patients with biopsy-proven prostate cancer and scheduled for radical prostatectomy underwent a 3-D contrast-enhanced power Doppler scan prior to surgery. A 3-D ellipsoid model was manually fitted around the prostate. The model automatically divided the prostate into 12 zones. After calculation of a so-called clustering map, the clustering values of each zone were calculated. They were compared with whole-mount section histopathology. Region-of-interest (ROI) analysis was performed with bootstrapping to evaluate overall performance. RESULTS: The ROI analysis yielded area under the curve (AUC) values of 0.65 with a corresponding standard error of 0.03. CONCLUSION: Semiautomatic localization based on clustering analysis of blood flow aids in localization of prostate tumors. A clustering map is an easy-to-interpret extension to standard power Doppler images.