Spica magnetic resonance imaging for determination of abduction angle: initial results and reproducibility assessment.

PURPOSE: Spica magnectic resonance imaging (MRI) is an established technique for postoperative determination of hip reduction in patients treated for developmental dysplasia of the hip (DDH). A hip abduction angle >55° is considered excessive and has been associated with epiphyseal osteonecrosis. Our purpose was to establish objective criteria for measuring hip abduction angles on MRI after hip reduction and spica casting in patients with DDH, and evaluate reproducibility and reliability of angle measurement using these criteria. METHODS: Forty patients with DDH at our institution who underwent spica MRI after hip reduction between 3 April 2008 and 3 March 2015 were identified. Hip abduction angles were measured on proton density axial images as follows. A transverse line was drawn connecting the posterior ischial tuberosities. A second line was drawn medially along the distal femoral diaphysis, and the angle between these two lines was measured; this value was subtracted from 90°, yielding the degree of abduction from midline. Measurements were independently performed by three faculty radiologists, one orthopedist, and one radiology resident. Inter-reader and intra-reader reliability was assessed using intraclass correlation (ICC), with 0 representing no agreement and 1 representing perfect agreement. RESULTS: For inter-reader reliability, the ICC of the five physicians was 0.89 (95 % CI 0.84-0.92). For intra-reader reliability, the ICC of the five physicians ranged from 0.90-0.97 (95 % CI 0.85-0.98). The mean standard deviation of hip abduction angle measurement among readers was 3.6°. CONCLUSION: The proposed hip abduction angle measurement criteria for spica MRI are both reproducible and easy to perform. The high ICC and low standard deviation of independently evaluated hip abduction angles indicates high reproducibility of measurement. This applies to both inter- and intra-reader reliability.

MRI features of three paediatric intra-articular synovial lesions: a comparative study.

AIM: To determine reliable magnetic resonance imaging (MRI) features differentiating three paediatric intra-articular congenital or neoplastic synovial lesions that contain blood products, from post-traumatic or haemorrhagic inflammatory processes. MATERIALS AND METHODS: This was a retrospective review of MRI findings of 22 paediatric intra-articular congenital or neoplastic synovial lesions, including venous malformation (VM) (n=12), pigmented villonodular synovitis (PVNS; n=8), and synovial sarcoma (SS; n=2). These MRI features were compared with 22 paediatric post-traumatic or inflammatory intra-articular processes containing blood products and producing mass effect. The following imaging features were assessed: presence of a discrete mass, extension, extra-articular oedema, susceptibility, joint effusion, and size. Fisher's exact test was used and results were considered statistically significant when p<0.05. RESULTS: The three intra-articular synovial lesions, compared with controls, were more likely to directly invade osseous structures when a discrete mass was present (13/16, 81.3% versus 1/9, 11.1%; p<0.002) and extend into extra-articular soft tissues (13/21, 61.9% versus 2/17, 11.8%; p<0.003), but were less likely to show extra-articular oedema (3/22, 13.6% versus 13/22, 59.1%; p<0.004), a joint effusion (10/22,45.5% versus 19/22, 86.4%, p<0.01), susceptibility within a joint effusion (0/22, 0% versus 11/22, 40.9%; p=0.00), osseous oedema (3/16, 18.8% versus 7/9, 77.8%; p<0.009), and synovial enhancement (8/21, 38.1% versus 14/16, 87.5%; p<0.003). VMs had characteristic tubular vessels with internal fluid-fluid levels (11/12) that extended into bone (10/12) and extracapsular soft tissues (11/12). CONCLUSION: Our study indicates that, despite the overlapping presence of haemorrhagic products, intra-articular VM, PVNS, and SS show MRI features that permit distinction from acquired post-traumatic and haemorrhagic inflammatory lesions.

Conventional and hydrocolonic US of the appendix with CT correlation performed by on-call radiology residents.

RATIONALE AND OBJECTIVES: The purpose of this study was to assess the feasibility and accuracy of emergent hydrocolonic ultrasonography (US) performed by on-call residents in patients suspected of having appendicitis. MATERIALS AND METHODS: Thirty-one patients with a clinically equivocal diagnosis of appendicitis were prospectively evaluated with conventional US, hydrocolonic US, and appendiceal computed tomography (CT). Midlevel radiology residents performed the US examinations while they were on call. Sensitivity, specificity, and accuracy for diagnosing appendicitis were calculated for conventional and hydrocolonic US by using clinical outcome as the standard. Results of US and CT of the appendix were also correlated. Residents recorded their diagnostic confidence for conventional and hydrocolonic US. All patients were able to hold the rectally administered contrast material until completion of both hydrocolonic US and appendiceal CT. RESULTS: The sensitivity for detecting appendicitis with conventional US, hydrocolonic US, and appendiceal CT was 50%, 75%, and 100%, respectively. Specificity was 96%, 93%, and 93%, respectively. Identification of the normal and abnormal appendix improved from 13% (four of 31 patients) with conventional US to 35% (11 of 31 patients) with hydrocolonic US. The radiology residents' diagnostic confidence increased from 0.74 with conventional US to 0.83 with hydrocolonic US. CONCLUSION: Hydrocolonic US is a feasible addition to conventional US examination for patients suspected of having appendicitis. It improves sensitivity, increases radiology residents' confidence, and is well tolerated by patients.

The dynamical structure of the RNA in alfalfa mosaic virus studied by 31P-nuclear magnetic resonance.

The structure of the viral RNA in alfalfa mosaic virus (AlMV) was investigated by means of 31P-nuclear magnetic resonance (NMR). It was found that the 31P-NMR line width of AlMV Top a particles is significantly smaller than that of the larger Bottom particles. At low temperatures, the totational correlation time of the 31P nuclei essentially equals the tumbling rate of the virus particle, indicating that the RNA is contained rigidly inside the virion. At more elevated temperatures, the NMR line width sharpens more than expected on the basis of viscosity changes and the RNA exhibits internal mobility. The occurrence of internal mobility is paralleled by an increased internal mobility of the N-terminal part of the coat protein, as could be observed by 1H-NMR spectroscopy. The influence of EDTA on the 31P-NMR line width appeared to be negligible, which is in agreement with the idea that AlMV does not 'swell' like several other RNA-containing plant viruses.

Fluorescence studies on the coat protein of alfalfa mosaic virus.

The intrinsic luminescence of different forms of the alfalfa mosaic virus (AMV) strain 425 coat protein has been studied, both statically and time resolved. It was found that the emission of the protein (Mr 24,250), which contains two tryptophans at positions 54 and 190 and four tyrosines, is completely dominated by tryptophan fluorescence. The high fluorescence quantum yield indicates that both tryptophans are emitting. Surprisingly, the fluorescence decay is found to be strictly exponential, with a lifetime of 5.1 nsec. Similar results were obtained for various other forms of the protein, i.e. the 30-S polymer, the mildly trypsinized forms of the protein lacking the N-terminal part and the protein assembled into viral particles. Virus particles and proteins of stains S and VRU gave similar results, as well as the VRU protein polymerised into tubular structures. The fluorescence decay is also monoexponential in the presence of various concentrations of the quenching molecules acrylamide and potassium iodide. Stern-Volmer plots were linear and yield for the coat protein dimer with acrylamide a quenching constant of 4.5* 10(8) M-1 sec-1. This indicates that the tryptophans are moderately accessible for acrylamide. For the 30-S polymer a somewhat smaller value was found, whereas in the viral Top a particles the accessibility of the tryptophans is still further reduced. From the decay of the polarisation anisotropy of the fluorescence of the coat protein dimer the rotational correlation time was obtained as 35 nsec. Since this roughly equals the expected rotational correlation time of the dimer as a whole, it suggests that the tryptophans are contained rigidly in the dimer. The results show that in the excited state of the protein the two tryptophans are strongly coupled and suggest that the trp-trp distance is smaller than 10 A. Because the coat protein occurs as a dimer, the coupling can be inter- or intramolecular. The implications for the viral structure are discussed.

epsilon-Crystallin, a novel avian and reptilian eye lens protein.

Gel filtration of Peking duck eye lens proteins reveals a component eluting just behind delta-crystallin and comprising approximately 10% of the total soluble protein. The native Mr of this additional component is estimated to be 120000; it appears to be composed of three identical chains of Mr 38000 and pI 7.5. Circular dichroic spectroscopy showed a relatively high alpha-helical content. No immunological cross-reactivity is found with alpha-, beta-, gamma- or delta-crystallins, and partial amino acid sequence determinations likewise failed to reveal any similarity with other known crystallins. We conclude that this protein represents another and novel family of eye lens proteins, for which we propose the designation epsilon-crystallin. epsilon-Crystallin is translated from a 1450-base mRNA, which has been partially purified. epsilon-Crystallin is found scattered among avian and reptilian taxa, but not in other vertebrates. Its rate of evolutionary change seems to be as slow as that of alpha- and beta-crystallins.