Segmentation and quantification of adipose tissue by magnetic resonance imaging

In this brief review, introductory concepts in animal and human adipose tissue segmentation using proton magnetic resonance imaging (MRI) and computed tomography are summarized in the context of obesity research. Adipose tissue segmentation and quantification using spin relaxation-based (e.g., T1-weighted, T2-weighted), relaxometry-based (e.g., T1-, T2-, T2*-mapping), chemical-shift selective, and chemical-shift encoded water–fat MRI pulse sequences are briefly discussed. The continuing interest to classify subcutaneous and visceral adipose tissue depots into smaller sub-depot compartments is mentioned. The use of a single slice, a stack of slices across a limited anatomical region, or a whole body protocol is considered. Common image post-processing steps and emerging atlas-based automated segmentation techniques are noted. Finally, the article identifies some directions of future research, including a discussion on the growing topic of brown adipose tissue and related segmentation considerations.     

Segmentation and characterization of interscapular brown adipose tissue in rats by multi-parametric magnetic resonance imaging

Objective

The aim was to auto-segment and characterize brown adipose, white adipose and muscle tissues in rats by multi-parametric magnetic resonance imaging with validation by histology and UCP1.

Materials and methods

Male Wistar rats were randomized into two groups for thermoneutral (n = 8) and cold exposure (n = 8) interventions, and quantitative MRI was performed longitudinally at 7 and 11 weeks. Prior to imaging, rats were maintained at either thermoneutral body temperature (36 ± 0.5 °C), or short term cold exposure (26 ± 0.5 °C). Neural network based automatic segmentation was performed on multi-parametric images including fat fraction, T ₂ and T ₂* maps. Isolated tissues were subjected to histology and UCP1 analysis.

Results

Multi-parametric approach showed precise delineation of the interscapular brown adipose tissue (iBAT), white adipose tissue (WAT) and muscle regions. Neural network based segmentation results were compared with manually drawn regions of interest, and showed 96.6 and 97.1 % accuracy for WAT and BAT respectively. Longitudinal assessment of the iBAT volumes showed a reduction at 11 weeks of age compared to 7 weeks. The cold exposed group showed increased iBAT volume compared to thermoneutral group at both 7 and 11 weeks. Histology and UCP1 expression analysis supported our imaging results.

Conclusion

Multi-parametric MR based neural network auto-segmentation provides accurate separation of BAT, WAT and muscle tissues in the interscapular region. The cold exposure improves the classification and quantification of heterogeneous BAT.

     

Validation of an active shape model-based semi-automated segmentation algorithm for the analysis of thigh muscle and adipose tissue cross-sectional areas

Objective

To validate a semi-automated method for thigh muscle and adipose tissue cross-sectional area (CSA) segmentation from MRI.

Materials and methods

An active shape model (ASM) was trained using 113 MRI CSAs from the Osteoarthritis Initiative (OAI) and combined with an active contour model and thresholding-based post-processing steps. This method was applied to 20 other MRIs from the OAI and to baseline and follow-up MRIs from a 12-week lower-limb strengthening or endurance training intervention (n = 35 females). The agreement of semi-automated vs. previous manual segmentation was assessed using the Dice similarity coefficient and Bland-Altman analyses. Longitudinal changes observed in the training intervention were compared between semi-automated and manual segmentations.

Results

High agreement was observed between manual and semi-automated segmentations for subcutaneous fat, quadriceps and hamstring CSAs. With strength training, both the semi-automated and manual segmentation method detected a significant reduction in adipose tissue CSA and a significant gain in quadriceps, hamstring and adductor CSAs. With endurance training, a significant reduction in adipose tissue CSAs was observed with both methods.

Conclusion

The semi-automated approach showed high agreement with manual segmentation of thigh muscle and adipose tissue CSAs and showed longitudinal training effects similar to that observed using manual segmentation.

     

Segmentation of joint and musculoskeletal tissue in the study of arthritis

As the most frequent cause of physical disability, musculoskeletal diseases such as arthritis and osteoporosis have a great social and economical impact. Quantitative magnetic resonance imaging (MRI) biomarkers are important tools that allow clinicians to better characterize, monitor, and even predict musculoskeletal disease progression. Post-processing pipelines often include image segmentation. Manually identifying the border of the region of interest (ROI) is a difficult and time-consuming task. Manual segmentation is also affected by inter- and intrauser variability, thus limiting standardization. Fully automatic or semi-automatic methods that minimize the user interaction are highly desirable. Unfortunately, an ultimate, highly reliable and extensively evaluated solution for joint and musculoskeletal tissue segmentation has not yet been proposed, and many clinical studies still adopt fully manual procedures. Moreover, the clinical translation of several promising quantitative MRI techniques is highly affected by the lack of an established, fast, and accurate segmentation method. The goal of this review is to present some of the techniques proposed in recent literature that have been adopted in clinical studies for joint and musculoskeletal tissue analyses in arthritis patients. The most widely used MRI sequences and image processing algorithms employed to accomplish segmentation challenges will be discussed in this paper.     

A method for the automatic segmentation of brown adipose tissue

Objective

Brown adipose tissue (BAT) plays a key role for thermogenesis in mammals and infants. Recent confirmation of BAT presence in adult humans has aroused great interest for its potential to initiate weight-loss and normalize metabolic disorders in diabetes and obesity. Reliable detection and differentiation of BAT from the surrounding white adipose tissue (WAT) and muscle is critical for assessment/quantification of BAT volume. This study evaluates magnetic resonance (MR) acquisition for BAT and the efficacy of different automated methods for MR features-based BAT segmentation to identify the best suitable method.

Materials and methods

Multi-point Dixon and multi-echo T₂ spin-echo images were acquired from 12 mice using an Agilent 9.4T scanner. Four segmentation methods: multidimensional thresholding (MTh); region-growing (RG); fuzzy c-means (FCM) and neural-network (NNet) were evaluated for the interscapular region and validated against manually defined BAT, WAT and muscle.

Results

Statistical analysis of BAT segmentation yielded a median Dice-Statistical-Index, and sensitivity of 89. 92 % for NNet, 82. 86 % for FCM, 72. 74 % for RG, and 72. 70 %, for MTh, respectively.

Conclusion

This study demonstrates that NNet improves the specificity to BAT from surrounding tissue based on 3-point Dixon and T₂ MRI. This method facilitates quantification and longitudinal measurement of BAT in preclinical-models and human subjects.

     

The reliability of a segmentation methodology for assessing intramuscular adipose tissue and other soft-tissue compartments of lower leg MRI images

Objective

Determine the reliability of a magnetic resonance (MR) image segmentation protocol for quantifying intramuscular adipose tissue (IntraMAT), subcutaneous adipose tissue, total muscle and intermuscular adipose tissue (InterMAT) of the lower leg.

Materials and methods

Ten axial lower leg MRI slices were obtained from 21 postmenopausal women using a 1 Tesla peripheral MRI system. Images were analyzed using sliceOmatic? software. The average cross-sectional areas of the tissues were computed for the ten slices. Intra-rater and inter-rater reliability were determined and expressed as the standard error of measurement (SEM) (absolute reliability) and intraclass coefficient (ICC) (relative reliability).

Results

Intra-rater and inter-rater reliability for IntraMAT were 0.991 (95 % confidence interval [CI] 0.978–0.996, p < 0.05) and 0.983 (95 % CI 0.958–9.993, p < 0.05), respectively. For the other soft tissue compartments, the ICCs were all >0.90 (p < 0.05). The absolute intra-rater and inter-rater reliability (expressed as SEM) for segmenting IntraMAT were 22.19 mm² (95 % CI 16.97–32.04) and 78.89 mm² (95 % CI 60.36–113.92), respectively.

Conclusion

This is a reliable segmentation protocol for quantifying IntraMAT and other soft-tissue compartments of the lower leg. A standard operating procedure manual is provided to assist users, and SEM values can be used to estimate sample size and determine confidence in repeated measurements in future research.

     

Age and gender related effects on adipose tissue compartments of subjects with increased risk for type 2 diabetes: a whole body MRI / MRS study

Quantitative measurement of adipose tissue (AT) compartments in the entire body and of lipids in muscle and liver cells by means of MRI and MRS. Assessment of ageand gender related differences in AT compartments and determination of cross-correlations between AT compartments in a heterogeneous cohort at increased risk for metabolic diseases. One hundred and fifty healthy volunteers with increased risk to type 2 diabetes were examined. T1-weighted MRI was applied for whole-body adipose tissue quantification. Adipose tissue compartments were subdivided in lower extremities, trunk (abdominal subcutaneous (SCAT) and visceral (VAT) adipose tissue), and upper extremities. Intrahepatocellular lipids (IHCL) and intramyocellular lipids (IMCL) in tibialis anterior and soleus muscle were determined by volume selective MRS. Females are characterized by lower %VAT (2.8±1.3% vs. 4.6±1.4% ,p<0.001) and higher %SCAT (14.7±3.9% vs. 9.3±2.9% ,p<0.001). There is a strong correlation between %VAT and age (r=0.64/0.60 for females/males), whereas %SCAT remained virtually unchanged in males (r=-0.09) and was only slightly increaseding in females (r =0.30,p<0.01). For IHCL, age related differences were observed in females with significantly increased IHCL in the older women, but not in males. IMCL contents in both muscles were found almost independent of age in both, males and females. Furthermore, VAT and IHCL show significant correlations in both groups. Assessed age and gender related differences, especially the age related significant increase of VAT and IHCL, as well as cross-correlations between different lipid compartments might contribute to a better understanding of the lipid metabolism under normal and pathologic metabolic conditions in humans.Supported through a grant from the Deutsche Forschungsgemeinschaft (DFG, KFO 114/1)     

Ab initio calculations of the BaTiO3 (100) and (110) surfaces

We present and discuss the results of calculations of BaTiO₃ (100) surface relaxation and surface rumpling with two different terminations (BaO and TiO₂) and BaTiO₃ (110) surface relaxation with three different terminations (Ba, TiO and O). These are based on a hybrid B3PW exchange-correlation technique. The O-terminated A-type BaTiO₃ (110) surface has a surface energy close to that for the (100), which indicates that both (110) and (100) BaTiO₃ surfaces can exist simultaneously in perovskite ceramics.     

Comparison of Ampere's circuital law (ACL) and the law ofBiot-Savart (LBS)

Ampere's circuital law (ACL) and the law of Biot-Savart (LBS) are applied to the computation of the magnetic flux density at the center of the square loop. The results are compared and some common misunderstandings of students are clarified. It is seen that LBS is general and applies to closed or open circuits. In the case of open circuits, care must be exercised in applying the ACL. Here, two choices present themselves; one is to use a modified form of ACL appropriate to the problem at hand and the second is to use ACL in its generalized form, which takes into account the inevitable charge accumulations     

Geothermal heat supply for the towns of Erding (Germany) and Creteil (France)

The existing geothermal heat supply systems used in the town of Erding (Germany) and Creteil (France) are described. It is pointed out that the existing 30-MW geothermal heat supply system of Erding has prospects for extending it to a capacity of 63 MW.     

合金Pr_(0.15)Tb_(0.30)Dy_(0.55)Fe_(1.85)C_x的结构和磁致伸缩

用电弧炉熔炼法制备了Pr0.15Tb0.30Dy0.55Fe1.85Cx(x=0.0~0.1)合金。分别采用X射线衍射(XRD)、振动样品磁强计(VSM)和应变仪分析了合金的结构、居里温度和磁致伸缩。研究发现,所有样品均呈现单一MgCu2型Laves相结构;随C含量的增加,晶格常数增大、居里温度增高;C元素的引入,对合金的磁致伸缩和磁晶各向异性能产生了一定的影响。     

Ce0.8Y0.2O1.9电解质的制备及性能

以金属硝酸盐为原料,碳酸钠为共沉淀剂制备了电解质材料Ce0.8Y0.2O1.9(20 YDC),并对其性能进行了研究。XRD测试表明碳酸盐前躯体经600℃煅烧处理即可得到萤石结构氧化物,TEM观察煅烧后的粉体为分散性较好的球形纳米颗粒。对700℃煅烧的粉体冷压成型后进行烧结性能的研究,SEM分析和致密度的测量表明经1 400℃烧结4 h致密度能达到95%以上。利用两端子交流阻抗谱法在400～700℃空气气氛中测量了电解质的电性能,1 400℃烧结的20YDC电解质在700℃和600℃的电导率分别为0.04、0.015 S/cm,电导活化能为0.85 eV,表明其有望应用于中低温固体氧化物燃料电池。     

Comparison of T1-weighted 2D TSE, 3D SPGR,and two-point 3D Dixon MRI for automated segmentation of visceral adipose tissue at 3 Tesla

Objectives

To evaluate and compare conventional T1-weighted 2D turbo spin echo (TSE), T1-weighted 3D volumetric interpolated breath-hold examination (VIBE), and two-point 3D Dixon-VIBE sequences for automatic segmentation of visceral adipose tissue (VAT) volume at 3 Tesla by measuring and compensating for errors arising from intensity nonuniformity (INU) and partial volume effects (PVE).

Materials and methods

The body trunks of 28 volunteers with body mass index values ranging from 18 to 41.2 kg/m² (30.02 ± 6.63 kg/m²) were scanned at 3 Tesla using three imaging techniques. Automatic methods were applied to reduce INU and PVE and to segment VAT. The automatically segmented VAT volumes obtained from all acquisitions were then statistically and objectively evaluated against the manually segmented (reference) VAT volumes.

Results

Comparing the reference volumes with the VAT volumes automatically segmented over the uncorrected images showed that INU led to an average relative volume difference of ?59.22 ± 11.59, 2.21 ± 47.04, and ?43.05 ± 5.01 % for the TSE, VIBE, and Dixon images, respectively, while PVE led to average differences of ?34.85 ± 19.85, ?15.13 ± 11.04, and ?33.79 ± 20.38 %. After signal correction, differences of ?2.72 ± 6.60, 34.02 ± 36.99, and ?2.23 ± 7.58 % were obtained between the reference and the automatically segmented volumes. A paired-sample two-tailed t test revealed no significant difference between the reference and automatically segmented VAT volumes of the corrected TSE (p = 0.614) and Dixon (p = 0.969) images, but showed a significant VAT overestimation using the corrected VIBE images.

Conclusion

Under similar imaging conditions and spatial resolution, automatically segmented VAT volumes obtained from the corrected TSE and Dixon images agreed with each other and with the reference volumes. These results demonstrate the efficacy of the signal correction methods and the similar accuracy of TSE and Dixon imaging for automatic volumetry of VAT at 3 Tesla.

     

电流退火对Co68Fe4.5Si13.5B14微丝巨磁阻抗效应的影响

以去掉玻璃包覆层的Co<,68>Fe<,4.5>Si<,13.5>B<,14>非晶微丝为研究对象,观察电流退火对微丝巨磁阻抗效应的影响.当退火电流为30mA,较长的退火时间有利于材料性能的改善,退火时间延长,非晶芯丝的最大磁阻抗比和磁场灵敏度都会增高.当退火时间为90s,磁场强度H=79.6A/m、频率f=3MHz时,...     

Fe_(60.5-x)Pt_(39.5)Dy_x(x=0.5,1.0)磁性合金的相转变和磁性能研究

用X射线衍射仪(XRD)、振动样品磁强计(VSM)、金相及电子显微镜(SEM)研究了添加微量稀土元素Dy对Fe60.5_xPt39.5Dyx(x=0.5,1.0)合金的组织结构与性能的影响。结果表明:添加了稀土Dy的FePt合金有序无序两相共存的温度范围确保在600~800℃之间,且稀土Dy含量的增加提高了该合金从FCT向FCC的转变温度;低温退火态比高温快淬态得到更高的磁性能,原因是发生交换耦合所致,并对磁转变温度宽化作出了合理的解释。认为稀土Dy的加入可使合金的综合性能获得改善和提高。     

Mo对储氢合金RE0.78Mg0.22(Ni0.84-xCo0.15Al0.01MOx)3.5的结构及电化学性能的影响

采用XRD分析了La0.50Pr0.22Nd0.06Mg0.22(Ni0.84-xCo0.15Al0.01Mox)3.5(x=0.00,0.01,0.02,0.03和0.04)合金的晶体结构,并且系统地研究了合金的气固相储氢特性和电化学性能。结果表明,合金由Ce2Ni7型结构的A2B7主相和少量的具有CaCu5结构的AB5相构成,晶轴比c/a随着Mo含量的增大而增大。合金在吸放氢过程中的熵变DS和焓变DH与AB5型合金的数值相当。合金的电化学容量随Mo含量的增加而减小,由x=0.00时的381.2 mAh/g下降到x=0.01时的379.5 mAh/g,再至x=0.04时合金的容量最大为362.0 mAh/g;合金容量的衰减速率因Mo的掺入而变大,由x=0.00时的-0.23 mAh/(g.次)降为x=0.04时的-0.97 mAh/(g.次);合金的倍率性能在x=0.01时得以改善,改善幅度为4%。研究表明当x≤0.01时不仅保持了合金的高容量,而且改善了合金的高倍率性能。     

Segmentation and texture analysis of structural biomarkers using neighborhood-clustering-based level set in MRI of the schizophrenic brain

Objective

Schizophrenia (SZ) is a psychiatric disorder that especially affects individuals during their adolescence. There is a need to study the subanatomical regions of SZ brain on magnetic resonance images (MRI) based on morphometry. In this work, an attempt was made to analyze alterations in structure and texture patterns in images of the SZ brain using the level-set method and Laws texture features.

Materials and methods

T1-weighted MRI of the brain from Center of Biomedical Research Excellence (COBRE) database were considered for analysis. Segmentation was carried out using the level-set method. Geometrical and Laws texture features were extracted from the segmented brain stem, corpus callosum, cerebellum, and ventricle regions to analyze pattern changes in SZ.

Results

The level-set method segmented multiple brain regions, with higher similarity and correlation values compared with an optimized method. The geometric features obtained from regions of the corpus callosum and ventricle showed significant variation (p < 0.00001) between normal and SZ brain. Laws texture feature identified a heterogeneous appearance in the brain stem, corpus callosum and ventricular regions, and features from the brain stem were correlated with Positive and Negative Syndrome Scale (PANSS) score (p < 0.005).

Conclusion

A framework of geometric and Laws texture features obtained from brain subregions can be used as a supplement for diagnosis of psychiatric disorders.

     

锌单晶体(002)和(100)晶面的电化学行为

用塔菲尔曲线外推法、循环伏安法以及充放电法分别研究了锌多晶体电极、锌单晶体(002)晶面电极和(100)晶面电极在6.0 mol/L的KOH溶液中的电化学行为.结果表明:在6.0 mol/L的KOH溶液中,锌多晶体电极、锌单晶体(002)晶面电极和(100)晶面电极的腐蚀速度依次减小;锌单晶体电极可逆性更优;充放电循环过程中,在锌多晶体电极表面比锌单晶体电极表面更易生长枝晶.     

Sr1-xLaxFe12-xCoxO19铁氧体纳米颗粒的结构与磁性

利用溶胶-凝胶法制备出性能优良的Sr1-xLaxFe12-xCoxO19(x=0～0.5)铁氧体,研究了La、Co掺杂量对铁氧体结构和磁学性能的影响.XRD 结果显示,对x≤0.3样品均得到单一的M相,而x=0.4样品出现了CoFe2O4相,x=0.5样品出现了CoFe2O4相和LaFeO3相.VSM结果显示,在适当的代换量(x=0～0.2)范围,剩余磁感应强度增加,同时矫顽力也增加.x=0.2样品的Br、H-c和?s最大值分别为449mT、562.5 kA/m和68 Am2/kg,与未掺杂样品相比,La3+、Co2+的加入能明显提高样品的综合磁性能.