Exophthalmos caused by excessive fat: CT volumetric analysis and differential diagnosis

CT has proven to be excellent in identifying orbital pathology responsible for proptosis. Occasionally, no discrete mass or extraocular muscle enlargement to explain the exophthalmos is found, only an appearance suggestive of an abnormal increase in orbital fat volume. Fifteen patients were studied with proptosis apparently resulting from increased orbital fat. Clinical follow-up revealed that four of them had Graves orbitopathy, unilateral in one; two had Cushing disease/syndrome; and nine were obese without endocrinopathy. The orbital volume and percentage orbital fat volume were measured by CT software analysis in these patients and in a control group of 16 patients without proptosis. Measurements of proptosis and thickness of the scalp fat pad at the inion level were also performed. Significantly greater values for orbital fat volume, percentage fat volume, and proptosis were found in the proptosis group compared with the control group. There was excellent correlation between proptosis and percentage fat volume, supporting the contention that increased orbital fat is responsible for the proptosis. The thickness of the scalp fat pad at the inion level was significantly greater in obese and Cushing patients than in control subjects, but the thickness was not significantly greater in Graves patients than in controls. Proptosis and inion fat were well correlated (r = 0.74) in the control and obese patients, which suggests a relation between general body fat and orbital fat volume.     

Estimation of body composition in muscular dystrophy by MRI and stereology

We have applied the Cavalieri method of modern design stereology with magnetic resonance imaging for estimating the volume of whole-body muscle and fat compartments in four patients with muscular dystrophy, a patient with myopathy, five controls, an anorexic subject, and a body builder. Detailed systematic series (ie, 50) of axial MR images (T1-weighted, TR/TE 400/10 msec) were obtained throughout the whole body of each subject. The results showed that 15, 20, and 35 axial sections through the body are sufficient to secure coefficients of error (CEs) on the estimates of total muscle and fat volume of around 10%, 5%, and 3% respectively in muscular dystrophy patients and controls. The mean normalized volumes of muscle in four muscular dystrophy patients were decreased by 27% (t-test: P < 0.05), and those of total fat were increased by 12% (t-test: P > 0.05) relative to controls. The Cavalieri method provides a direct, efficient, and mathematically unbiased approach for studying human body compartments and may have application in assessing treatment efficacy in patients with muscular dystrophy. J. Magn. Reson. Imaging 2000;12:467-475.     

Ophthalmopathy of Graves' disease: computerized volume measurements of the orbital fat and muscle

Pixel-calibrated volume measurements of muscle and fat in the bony orbit were made from CT scans of 72 patients with Graves' disease, with and without ophthalmopathy, to define characteristic changes present in clinical subgroups. Measurement abnormalities were detected in 87% of Graves' patients with clinically detectable ophthalmopathy and in 70% of hyperthyroid patients without clinical eye signs. Abnormal enlargement of the fat compartment in addition to muscle enlargement was found in 46% of patients with clinical ophthalmopathy; 8% of patients had only increased size of the fat compartment with normal muscle volumes. The ratio of muscle to fat and the volumes of orbital muscle and fat all varied widely in each clinical subgroup. Statistically significant (p less than 0.0001) total muscle-volume increase (range = 3.68-17.06 cm3) and borderline significant (p less than 0.06) fat-compartment increase (range = 6.05-22.63 cm3) were documented in all clinical subgroups. The degree of change of muscle and fat volumes was independent of the clinical group. Abnormal changes were found in the contralateral orbit in six of seven patients who appeared to have unilateral ophthalmopathy on clinical examination. A higher frequency of medial and inferior muscle enlargement was documented in all clinical subgroups.     

Evaluation of extraocular muscles using dynamic contrast enhanced MRI in patients with chronic thyroid orbitopathy

OBJECTIVE: The purpose of the current study is to investigate the underlying pathophysiological changes of extraocular muscle (EOM) in Graves orbitopathy using dynamic contrast MR imaging and to correlate these MR functional changes with the anatomic abnormalities. METHODS: EOMs of 16 patients with Graves disease and 12 normal volunteers were examined by dynamic enhanced MRI. We quantified the peak enhancement ratio of EOMs and calculated the ratio versus temporalis muscle and the ratio of maximum upslope versus temporalis muscle. We compared the ratios between normal volunteers and patient groups. RESULTS: Mean of peak enhancement ratio values for the EOMs in patients with Graves disease tends to decrease according to the severity of the anatomic and clinical changes. The mean maximum upslope also decreased according to the severity of the disease for EOMs. CONCLUSION: Hemodynamic information obtained by dynamic contrast enhanced MRI is useful in evaluating the clinical course of thyroid orbitopathy.     

Quantitative and qualitative fat analysis in human leg muscle of neuromuscular diseases by 1H MR spectroscopy in vivo

1H MR spectra were recorded from human gastrocnemius muscle at 63.86 MHz using the body coil of the Signa scanner as transmitter and a 3-in. surface coil as receiver. The fat content of the muscle was quantified relative to that of water in a selected volume or slice. The fat/water ratio was 0.05-0.07 for normal muscle but increased to 0.5-6.0 in primary and secondary muscular disorders such as Duchenne and myotonic dystrophy, Charcot-Marie-Tooth and polio muscular atrophy, cerebral palsy, and spina bifida. In Werdnig-Hoffmann spinal atrophy the ratio was above 10. Water-suppressed and slice-selective 1H spectroscopy was used for qualitative analysis of fat. The 1H profile of gastrocnemius muscles between healthy individuals and patients with neuromuscular diseases showed two major differences. In the normal muscle spectra, the resonance from the -(CH2)n- protons at 1.6 ppm was the most pronounced, whereas in the diseased muscle spectra resonances also appeared between 1.1 and 1.4 ppm. Some diseased muscle spectra showed multiple resonances from -CH = CH- in polyunsaturated fatty acids between 5.5 and 7.0 ppm. The corresponding resonances from = CH-CH2-, 1.9-2.0 ppm, and = CH-CH2-CH =, 2.7-2.9 ppm, were also seen. These peaks are usually not detected in normal muscle.     

Significance of the "Delayed hyperintense portal vein sign" in the hepatobiliary phase MRI obtained with Gd-EOB-DTPA

Purpose:

To identify MRI biomarkers that could be used to follow disease progression and therapeutic efficacy in one individual muscle in patients with myotonic dystrophy type 1 (DM1).

Materials and Methods:

Lower limb MRI and maximal ankle dorsiflexor strength assessment, using a hand‐held dynamometer, were performed in 19 DM1 patients and 6 control subjects. The volume of residual muscle tissue of Tibialis Anterior (TA) muscle was chosen as an index for muscle atrophy, and the T2‐relaxation‐time of the residual muscle tissue was measured to evaluate edema‐like lesions. The fat‐to‐water ratio was assessed using three‐point Dixon images to quantify fat infiltration in the entire muscle.

Results:

The intra‐observer variability of MRI indices (～5.2% for the residual muscle tissue volume and 2.5% for the fat‐to‐water ratio) was lower than that of the dorsiflexor torque measurement (～11.5%). A high correlation (r = 0.91) was found between maximal ankle dorsiflexor strength and residual TA muscle tissue volume in DM1 patients. Increases in the fat‐to‐water ratio and T2‐relaxation‐time were associated with a decrease in maximal ankle dorsiflexor strength.

Conclusion:

MRI appears as a noninvasive method which can be used to follow disease progression and therapeutic efficacy. J. Magn. Reson. Imaging 2012;35:678‐685. © 2011 Wiley Periodicals, Inc.     

MRI of normal and pathologic skeletal muscle

Lower extremity skeletal muscle of 22 individuals (five normal volunteers and 17 patients with muscular or neuromuscular diseases) was studied with magnetic resonance imaging. Axial images generated with spin-echo pulse sequences using short repetition times (500-900 msec TR) and short echo times (30-60 msec TE) provided excellent contrast between fat (high signal intensity) and muscle (intermediate signal intensity). Seventeen patients with clinically verified muscle disorders were evaluated in a manner similar to the normal volunteers. Conditions studied include Duchenne muscular dystrophy (three patients), limb-girdle muscular dystrophy (five), facioscapulohumeral dystrophy (three), and spinal muscular atrophy, amyotrophic lateral sclerosis, hereditary sensorimotor neuropathy, cerebral palsy, poliomyelitis, and Kearn-Sayre mitochondrial muscle disease (one each). General patterns of muscle abnormality were common among the diseases and included decreased or increased muscle size and a spectrum of muscle replacement by fat. Variable patterns were observed within disease groups and for each patient. Much phosphorus-31 spectroscopy has been performed in a blind fashion with no proton map of normal/abnormal muscle distribution to guide the spectroscopist. This study emphasizes the worth of having a muscle proton map of patients with muscle dysfunction to assure that meaningful phosphorus spectroscopic information is obtained from a volume of tissue limited to an appropriate muscle.     

Graves ophthalmopathy: role of MR imaging in radiation therapy

Twenty-three patients with Graves ophthalmopathy who underwent radiation therapy were monitored by means of magnetic resonance (MR) imaging. T2 relaxation times of extraocular muscles and orbital fat, areas of extraocular muscles, and degree of exophthalmos were measured by means of MR imaging at the beginning, at the end, and 3 months after completion of radiation therapy. As a result, patients with primarily elevated T2 times of extraocular muscles showed a better therapy response regarding muscle thickening than patients with primarily normal T2 times. Elevated T2 times, which probably represent acute inflammatory changes, were markedly decreased at the end of therapy. Therefore, quantitative MR imaging favors the choice of anti-inflammatory therapy regimens in patients with elevated T2 times of extraocular muscles. However, the clinical response (activity scores) to the low-dose treatment protocol that was used did not correlate well with primarily elevated T2 times. Furthermore, T2 times increased again after cessation of therapy. Whether a higher radiation dose or a different fractionation scheme leads to better results must be clarified by means of further study.     

Fat quantification using three-point dixon technique: in vitro validation

RATIONALE AND OBJECTIVES: To test the repeatability, reproducibility and accuracy of the three-point Dixon (3PD) sequence for estimating true fat volume ratios using a fat/water phantom. MATERIALS AND METHODS: A phantom, constructed from test tubes of varying fat content, was imaged using the 3PD sequence on a 1.5T MRI scanner by two operators four times each. Fat volume ratios were calculated from these images and compared with true fat volumes. RESULTS: Measures of fat volume ratios calculated from the 3PD MR images correlated strongly with values for true fat volumes (r = 0.96). CONCLUSION: The 3PD technique was found to be highly reproducible and accurate, and may be useful for in vivo quantification of fat in lean tissues, such as the liver, pancreas or skeletal muscle.     

Impact of partial volume effects on visceral adipose tissue quantification using MRI

Purpose:

To quantitatively estimate the impact of partial volume effects on visceral adipose tissue (VAT) quantification using typical resolution magnetic resonance imaging (MRI).

Materials and Methods:

Nine normal or overweight subjects were scanned at central abdomen levels with a water‐saturated, balanced steady‐state free precession (b‐SSFP) sequence. The water‐saturation effectiveness was evaluated with region‐of‐interest analysis on fat, muscle, bowel, and noise areas. The number of full‐volume (FV) and partial‐volume (PV) fat pixels was estimated based on a gray‐level histogram model of water‐saturated images. Both FV and PV fat amounts were quantified.

Results:

High‐quality, fat‐only images were generated with the b‐SSFP imaging method. Fat SNR was 77.7 ± 25.6 and water‐saturation was effective, with the average fat‐to‐water signal intensity ratio = 20.7 ± 3.8. The average ratio of partial‐ to full‐volume fat amounts was 104.0%. The ratio was higher with lower body mass index (BMI) and PV fat amount only increased slightly when BMI increased.

Conclusion:

PV fat contributes a significant amount of fat to fat measurements on typical spatial resolution MRI on normal and overweight subjects. The relative PV fat contribution is markedly higher in slimmer patients. Inclusion of this portion of the adipose tissue will increase overall accuracy and decrease variability of VAT quantification using MRI. J. Magn. Reson. Imaging 2011;. © 2011 Wiley Periodicals, Inc.     

Long-term fat diet adaptation effects on performance,training capacity,and fat utilization

It is well known that adaptation to a fat-rich carbohydrate-poor diet results in lower resting muscle glycogen content and a higher rate of fat oxidation during exercise when compared with a carbohydrate-rich diet. The net effect of such an adaptation could potentially be a sparing of muscle glycogen, and because muscle glycogen storage is coupled to endurance performance, it is possible that adaptation to a high-fat diet potentially could enhance endurance performance. Therefore, the first issue in this review is to critically evaluate the available evidence for a potential endurance performance enhancement after long-term fat-rich diet adaptation. Attainment of optimal performance is among other factors dependent also on the quality and quantity of the training performed. When exercise intensity is increased, there is an increased need for carbohydrates. On the other hand, consumption of a fat-rich diet decreases the storage of glycogen in both muscle and liver. Therefore, training intensity may be compromised in individuals while consuming a fat-rich diet. During submaximal exercise, fat for oxidation in muscle is recruited from plasma fatty acids, plasma triacylglycerol, and muscle triacylglycerol: the final question addressed in this review is which of these source(s) of fat contributes to the increased oxidation of fat during submaximal exercise after long-term fat diet adaptation.     

Extraocular muscle quantification using mathematical morphology: a semi-automatic method for analyzing muscle enlargement in orbital diseases.

Mathematical morphology was used to quantify the dimensions of the human extraocular muscles in computed tomography orbital scans. Coronal images of 28 patients with Graves orbitopathy and 5 controls (218 orbital scans) were analyzed with an algorithm for extraocular muscle segmentation. The results showed that measurements of extraocular muscle area obtained with semi-automatic segmentation are highly correlated with manual tracing and provides a simple method to quantify orbital structures including the extraocular muscles.     

Effects of two electrical stimulation frequencies in thigh muscle after knee surgery

The purpose of this study was to compare the effects of two protocols of electrical stimulation combined with voluntary contractions on the recovery of thigh muscles after anterior cruciate ligament (ACL) surgery. Ten sportsmen with a mean age of 26 yrs were randomly assigned into two groups: a 80 Hz stimulated group (5 patients) and a 20 Hz stimulated group (5 patients). All patients received electrical stimulation of the quadriceps femoris, five days a week, for 12 weeks, and had a standard program of voluntary contractions. Muscle and fat volumes of the thigh were assessed using MRI before surgery and after 12 weeks of rehabilitation. Quadriceps and hamstring muscle strength were evaluated by isokinetic measurements. Twelve weeks after surgery, the quadriceps peak torque deficit in the operated limb with respect to the non operated limb at 180 degrees /s and 240 degrees /s was significantly (p < 0.05) less in the 20 Hz group than in the 80 Hz group. This difference was not confirmed when comparing the pre-surgery quadriceps peak torque of the operated limb with the post-surgery one. Subcutaneous fat volume was increased for the two groups at the post-surgery test. This increase was significantly (p < 0.05) greater for the 80 Hz group. Thigh muscle volume deficit was not significantly different between the two groups.     

有氧运动对C57BL/6小鼠骨骼肌PPARα及CPT-1的影响

目的:研究8周有氧运动对高脂饮食小鼠血脂及骨骼肌中脂质代谢相关因子的影响,探讨过氧化物酶体增殖物激活受体α(PPARα)与运动改善脂质代谢的关系。方法:雄性C57BL/6小鼠60只,随机分为正常饮食安静(NC)及运动组(NE)、高脂饮食安静(HC)及运动组(HE)。其中,HC与HE组均喂以高脂饲料;NE和HE组进行为期8周的无负重游泳训练。实验结束后,采用酶法和比色法分别检测血脂和游离脂肪酸(FFA)水平,并采用NorthernBlot、WesternBlot检测各组小鼠骨骼肌中PPARα、肉毒碱棕榈酰转移酶1(CPT-1)基因及蛋白表达。结果:高脂饮食条件下,运动组血清TG、TC、LDL及FFA比安静组显著降低,HDL显著升高;并且运动组骨骼肌PPARα及CPT-1的mRNA和蛋白表达均较安静组有所提高,尤其HE组表达量较HC组显著提高。结论:运动可有效促进脂肪酸的利用而改善血清脂质水平,并且可使骨骼肌PPARα、CPT-1表达量在转录和翻译水平上均有所提高,提示PPARα作为一个重要的脂质调节因子,在运动改善血脂中发挥着积极的作用。     

彩色多普勒甲状腺火海征诊断甲状腺机能亢进特异性的探讨

目的 探讨彩色多普勒甲状腺火海征在诊断甲状腺机能亢进病中的特异性价值。方法 回顾分析71例彩色多普勒甲状腺火海征血流图像，观察甲状腺火海征在甲状腺机能亢进病组和非甲状腺机能亢进病组中显示情况，并结合患者性别和年龄进行分析。结果 在71例甲状腺火海征中，发生在甲状腺机能亢进病组中41例（57．41％），发生在非甲状腺机能亢进病组30例（42．2％）；甲状腺火海征的发生与患者的年龄、性别无关。结论 甲状腺火海征在诊断甲状腺机能亢进病中有重要价值，但不是其特异性表现。凡能引起甲状腺血管增生、扩张和血流加快的甲状腺慢性疾病都有可能出现甲状腺火海征。     

Quantitative MR relaxometry study of muscle composition and function in duchenne muscular dystrophy

Magnetic resonance imaging and maps of T1 and T2 values were used to study muscle composition in Duchenne muscular dystrophy (DMD). The mean T2 of anterior tibial muscle was 27 msec in healthy control subjects and 43 msec with increased fatty infiltration in DMD patients. In stronger DMD patients, the distribution of muscle T2 values was narrow, centered at 27 msec as in the controls, with a nonoverlapping fat peak centered at 49 msec. In weaker DMD patients, the width of the muscle T2 peak increased and the peak shifted toward the fat peak. Mean muscle T1 decreased from 1.7 to 0.6 second with increasing fatty infiltration. These results show that quantitative T1 and T2 maps may be used to assess muscle status and monitor DMD progression.     

Muscle structure with low- and high-fat diets in well-trained male runners

Endurance capacity, maximal oxygen uptake capacity (VO2max) and quantitative muscle ultrastructural composition was analyzed in 7 well-trained male runners (mean age 37.1 years, mean VO2max 60 ml/min/kg) after a one month period of a low-fat diet (dietary fat intake 18.4% and a similar period of a high-fat diet (dietary fat intake 40.6%). Between these two interventional periods a washout period of one month was interspersed in which the nutritional fat content was approx. 32%; close to the average American Diet. During all three periods protein content of the nutrition was kept nearly constant at 15%. After the high-fat diet time to exhaustion in the endurance test increased significantly by 21% while VO2max remained unchanged. Muscle mitochondrial volume density remained unchanged while the intramyocellular fat content increased by 60%. Due to large interindividual differences in this variable this difference did not become statistically significant. While some 20% of the mitochondria are located in a subsarcolemmal location, only 10% of the lipid stores are associated with these mitochondria. Less than 2% of the mitochondrial outer surface are in contact with lipid droplets whereas 25-35% of the lipid surface is in contact with mitochondria. None of these variables is significantly altered after a high-fat diet. It is concluded that the change in endurance capacity of the subjects cannot be explained based on the structural changes observed in skeletal muscle tissue. This may be related to methodological problems associated with the determination of intramyocellular fat content.     

131I治疗Graves病后暂发性甲低的临床分析

目的：探讨^131I治疗后暂发性甲低的临床特点和转归。方法：对32例^131I治疗后出现暂发性甲低的患者进行临床分析和随访。结果：暂发性甲低出现在^131I治疗后2～6个月，有甲低症状者19例(59．38％)。甲低缓解后甲状腺功能正常者20例(62．5％)，又甲亢者12例(37．5％)。甲低时，T3和T4明显降低，TSH变化不一。结论：暂发性甲低多发生在低剂量^131I治疗的患者，甲低缓解后部分患者可再次出现甲亢。     

多发性肌炎的CT应用价值

目的研究多发性肌炎(PM)的肌肉CT表现特点及应用价值。方法经肌肉活检证实的多发性肌炎20例。所有病例均完成腰背肌、臀肌、大腿肌以及小腿肌的CT轴位扫描,其中大腿肌和小腿肌分肌群组观察。观察内容包括:肌肉的密度;肌肉的体积;肌筋膜的改变;肌肉组织的清晰度;皮下脂肪层厚度。结果CT发现肌肉体积缩小15个部位;肌肉密度减低,脂肪样变53个部位;筋膜增厚18个部位;皮下脂肪层增厚23个部位;肌肉组织模糊3个部位。结论CT能够清楚显示PM肌肉病损程度、判断肌肉萎缩和病变分布情况,为肌肉活检明确定位。     

Caloric and exercise requirements of space flight: biostereometric results from skylab.

The biostereometric study of the Skylab astronauts used stereophotogrammetry to make accurate three-dimensional measurement of body form, from which regional and total body volumes were derived. Volume changes in the thighs and calves, over the course of the flight, showed a high correlation with inflight exercise on the bicycle ergometer, and suggested that an exercise level of 80-100 W-min/d/kg lean body mass would be necessary to prevent inflight muscle atrophy. The bicycle ergometer is thus a relatively inefficient means of preventing leg muscle atrophy. Inflight caloric intake showed a high correlation with the change in volume of the buttocks, the abdomen, and the body as a whole, and suggested that a caloric intake of 47-51 kcal/d/kg lean body mass would be necessary to prevent a change in body fat. Only one of the astronauts exceeded this range and gained body fat; the group as a whole showed a mean fat loss of 1.2 kg.