The effect of a multidisciplinary intervention program on hepatic adiposity in overweight-obese children: protocol of the EFIGRO study.

BACKGROUND: Non-alcoholic fatty liver disease is the most frequent liver abnormality observed in overweight or obese children and is strongly associated with metabolic syndrome and insulin resistance. OBJECTIVES: (i) To evaluate the effect of a 22-week multidisciplinary intervention program on hepatic fat fraction in overweight or obese children and (ii) to examine the effect of the intervention on cardiometabolic risk factors, self-esteem and well-being. METHODS: A total of 160 children, 9-11 years, will be recruited by pediatricians and randomly assigned to control (N = 80) or intervention (N = 80) groups. The control group will receive a family-based lifestyle and psycho-educational program (2 days/month), while the intervention group will attend the same lifestyle education and psycho-educational program plus the exercise program (3 days/week). The duration of training sessions will be 90 min of exercise, including warm-up, moderate to vigorous aerobic activities, and strength exercises. The primary outcome is the change in hepatic fat fraction (magnetic resonance imaging, MRI). Secondary outcomes include cardiometabolic risk factors such as total adiposity (dual Xray absorptiometry), visceral adiposity (MRI), functional peak aerobic capacity (cardiopulmonary exercise testing), blood pressure, muscular fitness, speed­agility, and fasting blood insulin, glucose, C-reactive protein, alanine aminotransferase, aspartate aminotransferase, gamma glutamyltransferase, lipid profile and psychological measurements (questionnaires). All the measurements will be evaluated at baseline prior to randomization and after the intervention. DISCUSSION: This study will provide insight in the efficacy of a multidisciplinary intervention program including healthy lifestyle education, psycho-education and supervised exercise to reduce hepatic fat and cardiometabolic risk in overweight children.

Automated two-point dixon screening for the evaluation of hepatic steatosis and siderosis: comparison with R2-relaxometry and chemical shift-based sequences.

OBJECTIVES: To evaluate the automated two-point Dixon screening sequence for the detection and estimated quantification of hepatic iron and fat compared with standard sequences as a reference. METHODS: One hundred and two patients with suspected diffuse liver disease were included in this prospective study. The following MRI protocol was used: 3D-T1-weighted opposed- and in-phase gradient echo with two-point Dixon reconstruction and dual-ratio signal discrimination algorithm ("screening" sequence); fat-saturated, multi-gradient-echo sequence with 12 echoes; gradient-echo T1 FLASH opposed- and in-phase. Bland-Altman plots were generated and correlation coefficients were calculated to compare the sequences. RESULTS: The screening sequence diagnosed fat in 33, iron in 35 and a combination of both in 4 patients. Correlation between R2* values of the screening sequence and the standard relaxometry was excellent (r = 0.988). A slightly lower correlation (r = 0.978) was found between the fat fraction of the screening sequence and the standard sequence. Bland-Altman revealed systematically lower R2* values obtained from the screening sequence and higher fat fraction values obtained with the standard sequence with a rather high variability in agreement. CONCLUSIONS: The screening sequence is a promising method with fast diagnosis of the predominant liver disease. It is capable of estimating the amount of hepatic fat and iron comparable to standard methods. KEY POINTS: • MRI plays a major role in the clarification of diffuse liver disease. • The screening sequence was introduced for the assessment of diffuse liver disease. • It is a fast and automated algorithm for the evaluation of hepatic iron and fat. • It is capable of estimating the amount of hepatic fat and iron.

Time-interleaved acquisition of modes: an analysis of SAR and image contrast implications.

As the magnetic field strength and therefore the operational frequency in MRI are increased, the radiofrequency wavelength approaches the size of the human head/body, resulting in wave effects which cause signal decreases and dropouts. Especially, whole-body imaging at 7 T and higher is therefore challenging. Recently, an acquisition scheme called time-interleaved acquisition of modes has been proposed to tackle the inhomogeneity problems in high-field MRI. The basic premise is to excite two (or more) different B 1+ modes using static radiofrequency shimming in an interleaved acquisition, where the complementary radiofrequency patterns of the two modes can be exploited to improve overall signal homogeneity. In this work, the impact of time-interleaved acquisition of mode on image contrast as well as on time-averaged specific absorption rate is addressed in detail. Time-interleaved acquisition of mode is superior in B 1+ homogeneity compared with conventional radiofrequency shimming while being highly specific absorption rate efficient. Time-interleaved acquisition of modes can enable almost homogeneous high-field imaging throughout the entire field of view in PD, T(2) , and T(2) *-weighted imaging and, if a specified homogeneity criterion is met, in T(1) -weighted imaging as well.

Artifact reduction in moving-table acquisitions using parallel imaging and multiple averages.

Two-dimensional (2D) axial continuously-moving-table imaging has to deal with artifacts due to gradient nonlinearity and breathing motion, and has to provide the highest scan efficiency. Parallel imaging techniques (e.g., generalized autocalibrating partially parallel acquisition GRAPPA)) are used to reduce such artifacts and avoid ghosting artifacts. The latter occur in T(2)-weighted multi-spin-echo (SE) acquisitions that omit an additional excitation prior to imaging scans for presaturation purposes. Multiple images are reconstructed from subdivisions of a fully sampled k-space data set, each of which is acquired in a single SE train. These images are then averaged. GRAPPA coil weights are estimated without additional measurements. Compared to conventional image reconstruction, inconsistencies between different subsets of k-space induce less artifacts when each k-space part is reconstructed separately and the multiple images are averaged afterwards. These inconsistencies may lead to inaccurate GRAPPA coil weights using the proposed intrinsic GRAPPA calibration. It is shown that aliasing artifacts in single images are canceled out after averaging. Phantom and in vivo studies demonstrate the benefit of the proposed reconstruction scheme for free-breathing axial continuously-moving-table imaging using fast multi-SE sequences.

Sliding multislice (SMS): a new technique for minimum FOV usage in axial continuously moving-table acquisitions.

A novel technique for axial continuously moving-table scans is described that minimizes the required extension of the scanner's field of view (FOV) along the direction of table motion (z) by applying a segmented multislice acquisition technique. Any anatomical slice is acquired by applying the same phase-encoding steps at the same spatial positions along the scanner FOV. The full k-space data set of any anatomical slice is collected while the slice moves through the scanner from one scan position to the next. Simultaneous acquisition of multiple slices is realized by shifting the acquisition trajectories of different slices in time. It is demonstrated how the image artifact behavior that relates to varying imaging properties along the distance the table traverses during the acquisition of any given anatomical slice can be optimized simultaneously for all images. Discontinuities between the images along the slice axis are avoided because all z-dependent scan properties are encoded identically for all slices. Flexible spatial acquisition patterns are proposed to enable data oversampling and overlapping slice acquisitions at reduced table speeds. A framework of equations is presented by which matched parameter combinations for sliding multislice acquisitions can be applied to both single- and multiecho sequences. The new technique is validated on phantom and in vivo measurements using a T1-weighted fast low-angle shot (FLASH) sequence as well as a T2-weighted multi-spin-echo sequence of variable echo train lengths.

Comparison of profiles of key periodontal pathogens in periodontium and endodontium.

Despite the established anatomical relationship between the periodontal and pulpal tissues, bacterial migration between endodontium and periodontium is still under discussion. The objective of this study was an investigation of profiles of periodontal pathogens in pulpal and periodontal diseases affecting the same tooth by means of 16S rRNA gene directed polymerase chain reaction (PCR). 31 intact teeth with both pulp and marginal infections were investigated. The diagnosis was based on clinical and radiological examination. Samples were taken from the gingival sulcus or periodontal pocket, respectively, with sterile paper points before trepanation of the teeth. After trepanation sterile paper points and Hedstroem files were used for taking samples from the root canal. Specific PCR methods were used to detect the presence of the following pathogens: Actinobacillus actinomycetemcomitans, Bacteroides forsythus, Eikenella corrodens, Fusobacterium nucleatum, Porphyromonas gingivalis, Prevotella intermedia and Treponema denticola. In addition, quantitative competitive PCR was used to determine the total bacterial count of the samples. The investigated pathogens were proven to be present in the endondontium in all disease categories. Particularly in endodontic samples of "chronic apical periodontitis" and "chronic adult periodontitis" profiles of the periodontal pathogens were found. The results confirmed that periodontal pathogens often accompany endodontic infections and supported the idea that the periodontic-endodontic interrelationships should be considered as critical pathways which might contribute to refractory courses of endodontic or periodontal diseases.

Geometric distortion correction in gradient-echo imaging by use of dynamic time warping.

Distortion caused by local static field variations in magnetic resonance imaging can be corrected by using a method developed by Chang and Fitzpatrick (CF) that requires two acquisitions identical except for the polarity of the read gradient. This approach has previously been applied to spin-echo imaging. In this report, its role in correcting geometric distortion in gradient-echo imaging is investigated using a dynamic programming algorithm. This approach appears to successfully handle many of the edge artifacts otherwise inherent in the CF method. Once the correction has been made, it is then possible to extract the local magnetic field itself. Magn Reson Med 42:585-590, 1999.