Ultrasound elastography in children: establishing the normal range of muscle elasticity.

BACKGROUND: Ultrasound elastography allows assessment of tissue elasticity. To the best of our knowledge, the elastography appearance of muscles in normal children has not been described. OBJECTIVE: To determine the US elasticity of muscles in children at rest and following exercise. MATERIALS AND METHODS: Cine elastography of biceps brachii and rectus femoris muscles was obtained at rest and after exercise in 42 healthy children (23 males, 19 females; mean: 11.2 ± 4.4 years, range: 2-18 years). Elastography scores were assigned to each clip based on a five-point color scale. Mean elastography scores and standard deviations were calculated and resting and postexercise elastography scores were compared. RESULTS: Resting muscle elasticity was lower in the biceps brachii than in the rectus femoris (P = 0.008), and higher in the dominant than in the nondominant biceps brachii (P < 0.032). Rectus femoris elasticity was higher in males than females (P = 0.051). Postexercise muscle elasticity significantly increased in both the dominant and nondominant biceps brachii (P < 0.001) and in the rectus femoris (P < 0.001). There was no significant gender-related difference in postexercise muscle elasticity. Biceps brachii elasticity decreased and rectus femoris elasticity increased with increasing body mass index. Younger subjects had a greater change in muscle elasticity with exercise. CONCLUSION: Resting muscle elasticity in children is significantly lower in the biceps brachii than in the rectus femoris and in the nondominant biceps brachii than in the dominant biceps brachii. Elasticity significantly increases immediately postexercise in both muscle groups; resting differences between biceps brachii and rectus femoris elasticity, and dominant and nondominant biceps brachii elasticity, do not persist after exercise. The change in muscle elasticity with exercise is higher in younger children.

Glutamate receptor 1 phosphorylation at serine 831 and 845 modulates seizure susceptibility and hippocampal hyperexcitability after early life seizures.

Neonatal seizures can lead to later life epilepsy and neurobehavioral deficits, and there are no treatments to prevent these sequelae. We showed previously that hypoxia-induced seizures in a neonatal rat model induce rapid phosphorylation of serine-831 (S831) and Serine 845 (S845) sites of the AMPA receptor GluR1 subunit and later neuronal hyperexcitability and epilepsy, suggesting that seizure-induced posttranslational modifications may represent a novel therapeutic target. To unambiguously assess the contribution of these sites, we examined seizure susceptibility in wild-type mice versus transgenic knock-in mice with deficits in GluR1 S831 and S845 phosphorylation [GluR1 double-phosphomutant (GluR1 DPM) mice]. Phosphorylation of the GluR1 S831 and S845 sites was significantly increased in the hippocampus and cortex after a single episode of pentyleneterazol-induced seizures in postnatal day 7 (P7) wild-type mouse pups and that transgenic knock-in mice have a higher threshold and longer latencies to seizures. Like the rat, hypoxic seizures in P9 C57BL/6N wild-type mice resulted in transient increases in GluR1 S831 and GluR1 S845 phosphorylation in cortex and were associated with enhanced seizure susceptibility to later-life kainic-acid-induced seizures. In contrast, later-life seizure susceptibility after hypoxia-induced seizures was attenuated in GluR1 DPM mice, supporting a role for posttranslational modifications in seizure-induced network excitability. Finally, human hippocampal samples from neonatal seizure autopsy cases also showed an increase in GluR1 S831 and S845, supporting the validation of this potential therapeutic target in human tissue.

Preliminary clinical experience at 3 T with a 3D T2-weighted sequence compared with multiplanar 2D for evaluation of the female pelvis.

OBJECTIVE: The purpose of this article is to compare 3D T2-weighted sampling perfection with application-optimized contrast with different flip-angle evolutions (SPACE) with three-plane 2D turbo-spin echo (TSE) sequences for female pelvic imaging at 3 T. MATERIALS AND METHODS: Twenty women were imaged with 2D TSE and 3D SPACE sequences. Three radiologists independently assessed image quality, diagnostic quality, and artifacts; measured normal anatomic structures; evaluated pathologic abnormalities; and recorded interpretation time. Readers subsequently performed a side-by-side comparison, and their preferences were graded according to overall interpretation, sharpness of lesion edges, motion and other artifacts, uterine and cervical zonal anatomy distinction, identification of adnexal pathologic abnormalities, and distinction between fat and fluid. Quantitative comparison of relative signal intensity and relative tissue contrast was performed. RESULTS: The mean acquisition time of 3D SPACE was significantly shorter than that of 2D TSE (6 minutes 35 seconds vs 8 minutes 50 seconds; p < 0.005). Intrareader agreement between interpretations of 2D and 3D sequences was excellent. There were no significant differences among readers in detecting artifacts, normal structures, and pathologic abnormalities or in determining endometrial thickness, image quality, or interpretation time (p > 0.05). Except for distinctions between fat and fluid, the average reader score indicated a slight preference for the 3D sequence. Three-dimensional multiplanar reconstructions were helpful but not considered essential. Relative agreement between readers was moderate (r ≥ 0.4) to strong (r ≥ 0.7). The relative signal intensity was higher for fat and bladder fluid on the 3D sequence than on the 2D sequence (p = 0.014 and p = 0.018, respectively). Relative tissue contrast was higher for the 3D sequence (p < 0.05), with no significant difference in bladder or fat contrast (p = 0.31) but a trend toward more superior contrast on the 2D sequence. CONCLUSION: At 3 T, 3D SPACE has similar image quality and diagnostic quality with shorter scan time when compared with 2D TSE but with reduced contrast between fat and fluid.

Advances in magnetic resonance imaging of articular cartilage.

The pathology, assessment, and management of articular cartilage lesions of the hip and knee have been the subject of considerable attention in the recent orthopaedic literature. MRI has long been an important tool in the diagnosis and management of articular cartilage pathology, but detecting and interpreting early cartilaginous degeneration with this technology has been difficult. Biochemical-based MRI has been advocated to detect early cartilaginous degenerative changes and assess cartilage repair. Techniques such as T2 mapping, T1rho (ie, T1 in the rotating frame), sodium MRI, and delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) take advantage of changes in the complex biochemical composition of articular cartilage and may help detect morphologic cartilaginous changes earlier than does conventional MRI. Although the newer modalities have been used primarily in the research setting, their ability to assess the microstructure of articular cartilage may eventually enhance the diagnosis and management of osteoarthritis.

Utility of the apparent diffusion coefficient for distinguishing clear cell renal cell carcinoma of low and high nuclear grade.

OBJECTIVE: The purpose of our study was to assess the utility of the apparent diffusion coefficient (ADC) in distinguishing low-grade and high-grade clear cell renal cell carcinoma (ccRCC). MATERIALS AND METHODS: The cases of 57 patients with pathologically proven ccRCC who underwent preoperative MRI, including diffusion-weighted imaging, were retrospectively assessed. ADC values were obtained from ADC maps calculated using b-value combinations of 0 and 400 s/mm² and of 0 and 800 s/mm² (hereafter referred to as ADC-400 and ADC-800). Lesions were also evaluated for an array of conventional MRI features. A single expert uropathologist reviewed all slides to determine nuclear grade. The utility of ADC for detecting high-grade ccRCC, alone and in combination with conventional MRI features, was assessed using receiver operating characteristic (ROC) analysis and binary logistic regression. RESULTS: ADC-400 and ADC-800 were significantly lower among high-grade than among low-grade ccRCC (2.24 ± 0.50 mm²/s vs 1.59 ± 0.57 mm²/s for ADC-400, p < 0.001; 1.85 ± 0.40 mm²/s vs 1.28 ± 0.48 mm²/s for ADC-800; p < 0.001). The area under the ROC curve for identifying high-grade ccRCC using ADC-400 and ADC-800 was 0.801 and 0.824 respectively (p = 0.606), with optimal thresholds, sensitivity, and specificity as follows: ADC-400: 2.17 mm²/s, 88.5%, 64.5% and ADC-800: 1.20 mm²/s, 65.4%, 96.0%. Using multivariate logistic regression, only necrosis (p = 0.0229) and perinephric fat invasion (p = 0.0160) were retained among conventional imaging features as independent risk factors for high-grade ccRCC. The accuracy of the logistic regression model for predicting high-grade ccRCC was significantly improved by inclusion of either ADC-400 (p = 0.0143) or ADC-800 (p = 0.015). CONCLUSION: ADC is significantly lower in high-grade ccRCC compared with low-grade ccRCC and increases the accuracy for detecting high-grade ccRCC compared with conventional MRI features alone.

MRI features of renal oncocytoma and chromophobe renal cell carcinoma.

OBJECTIVE: The purpose of this study was to retrospectively describe the MRI features of the pathologically related entities renal oncocytoma and chromophobe renal cell carcinoma (RCC). MATERIALS AND METHODS: Twenty-eight cases of histologically proven renal oncocytoma and 15 of chromophobe RCC evaluated with preoperative MRI from January 2003 through June 2009 at our institution were independently reviewed for an array of MRI features by two radiologists blinded to the final histopathologic diagnosis. These features were tabulated and compared between chromophobe RCC and renal oncocytoma by use of the Mann-Whitney test and binary logistic regression. RESULTS: Renal oncocytoma and chromophobe RCC showed no significant difference in size or any of 16 qualitative imaging features (p = 0.0842-1.0, reader 1; p = 0.0611-1.0, reader 2). Microscopic fat, hemorrhage, cysts, infiltrative margins, perinephric fat invasion, renal vein invasion, enhancement homogeneity, and hypervascularity were each observed in less than 20% of cases by both readers. A central scar and segmental enhancement inversion (a recently described finding in which early contrast-enhanced images show relatively more enhanced and less enhanced intralesional components with inversion of their relative enhancement on later images) were observed by both readers in at least 10% of cases of both renal oncocytoma and of chromophobe RCC with no significant difference between the two entities (p = 0.2092-0.2960). CONCLUSION: We have presented the largest series to date of the MRI features of both renal oncocytoma and chromophobe RCC. These related entities exhibited similar findings, and no MRI features were reliable in distinguishing between them.