Contrast-enhanced ultrasound (CEUS) in characterization of inconclusive cervical lymph nodes: a meta-analysis and systematic review

Lymph node metastases are common in malignant neoplasms of head and neck. Since cervical lymph nodes (cLN) are localized superficially, ultrasound (US) represents the primary imaging modality. The aim of the study is to report the value of US and contrast-enhanced ultrasound (CEUS) and their diagnostic confidence in the characterization of inconclusive cLN. A systematic review was performed using the literature data base PubMed. Results were filtered (published in a peer-reviewed journal, full-text available, published within the last ten years, species human, English or German full-text) and inclusion criteria were clearly defined (cohort with lymphadenopathy or malignancy in head and neck >= 50 patients, histological confirmation of malignant imaging findings, performance of CEUS as outcome variable). The results were quantified in a meta-analysis using a random-effects model. Overall, five studies were included in qualitative and quantitative analysis. The combination of non-enhanced US and CEUS enlarges the diagnostic confidence in the characterization of lymph nodes of unclear dignity. The pooled values for sensitivity and specificity in the characterization of a malignant cervical lymph node using US are 76% (95%-CI 66-83%, I-2 = 63%, p < 0.01) and 80% (95%-CI 45-95%, I-2 = 92%, p < 0.01), compared to 92% (95%-CI 89-95%, I-2 = 0%, p = 0.65) and 91% (95%-CI 87-94%, I-2 = 0%, p = 0.40) for the combination of US and CEUS, respectively. Consistent results of the included studies show improved diagnostic performance by additional CEUS. Nevertheless, more prospective studies are needed to implement CEUS in the diagnostic pathway of cLN

Multiparametric ultrasound findings in acute kidney failure due to rare renal cortical necrosis

Renal cortical necrosis (RCN) is a rare cause of acute kidney failure and is usually diagnosed on the basis of characteristic enhancement patterns on cross-sectional imaging. Contrast-enhanced ultrasound (CEUS) offers benefits in patients with kidney failure in the clinical setting including the use of a nonnephrotoxic intravascular contrast agent and the fact that it can be performed at the bedside in critical cases. Therefore, the aim of this study is to investigate whether CEUS can reliably identify typical imaging features of RCN. We retrospectively analyzed 12 patients with RCN examined in our department and confirmation of the diagnosis by either histopathology, other contrast-enhanced cross-sectional imaging tests, and/or CEUS follow-up. Assessed parameters in conventional US were reduced echogenicity, loss of corticomedullary differentiation, length and width of kidney, hypoechoic rim, resistance index and in CEUS delayed wash-in of contrast agent (>20 s), reverse rim sign, maximum nonenhancing rim and additional renal infarction. Furthermore, imaging features in RCN were compared with the findings in renal vein thrombosis (RVT), among them echogenicity, corticomedullar differentiation, hypoechoic rim, RI value, delayed cortical enhancement, total loss of cortical perfusion and enhancement of renal medulla. All 12 patients showed the reverse rim sign, while a hypoechogenic subcapsular rim was only visible in four patients on B-mode ultrasound. A resistance index (RI) was available in 10 cases and was always less than 1. RI was a strong differentiator in separating RVT from RCN (RI>1 or not measurable due to hypoperfusion as differentiator, p=0.001). CEUS showed total loss of medullary enhancement in all cases of RVT. With its higher temporal resolution, CEUS allows dynamic assessment of renal macro- and microcirculation and identification of the typical imaging findings of RCN with use of a nonnephrotoxic contrast agent

Diffusion of phase and impurity molecules in a smectic system

The diffusion of trichloro-trifluoroethane in the smectic A regime of two p-alkanoyl-benzylidene-p’-aminoazobenzenes (Cn — AAs) has been investigated by an NMR method. Comparison of the activation energies of diffusion along (D┴) and through (D//) the smectic layers with those of the selfdiffusion of the pure Cn — AAs suggests that the smectic layers act for the impurity as a stack of membranes, penetration of which is much more difficult than diffusion along the layers

NUCLEAR MAGNETIC RELAXATION AND DIFFUSION MEASUREMENTS IN p-DODECANOYLBENZYLIDENE-p'-AMINOAZOBENZENE

Les temps de relaxation T1Z et T1D des protons de la molécule p-dodécanoylbenzylidène-p'-aminoazobenzène ont été mesurés dans les différentes mésophases de ce système. Les résultats sont interprétés en termes de mouvements moléculaires et sont reliés à des mesures de diffusion translationnelle du trifluorotrichloroéthane dissout dans le cristal liquide.T1Z and T1D relaxation time measurements are presented for p-dodecanoyl-benzylidene-p'-aminoazobenzene. The results obtained in the different mesomorphic phases are correlated with plausible movements of the molecules and with self diffusion measurements of trifluorotrichloroethane dissolved in the above mentioned liquid crystal

NUCLEAR MAGNETIC RELAXATION AND SELF DIFFUSION IN SOME LIQUID CRYSTALS SHOWING SMECTIC POLYMORPHISM

Les temps de relaxation nucléaire, T1Z et T1D, et les coefficients de diffusion D|| et D⊥ ont été mesurés en fonction de la température dans éthyl p-(p-éthoxybenzylidène)-amino-cinnamate (EBAC) et dans TBBA. Les résultats montrent que la diffusion contribue aux vitesses de relaxation dans les phases smectiques A, C et H de TBBA et les phases A et B de EBAC. La diffusion perpendiculairement au directeur est clairement du type diffusion liquide dans les phases A et C. Dans la phase B de EBAC, d'autre part, la diffusion se fait par sauts comme dans un pseudoréseau.Nuclear magnetic relaxation times T1Z and T1D and the self diffusion coefficients D|| and D⊥ have been measured in dependence of temperature in ethyl p-(p-ethoxybenzylidene)-amino-cinnamate (EBAC) and TBBA. The results show that the diffusion process contributes to the relaxation rates in the smectic A, C and H phases of TBBA and in the smectic A and B phases of EBAC. Evidence is given that the diffusion perpendicular to the molecular director is liquid like in the A and C phases and of a pseudolattice jump type in the B phase of EBAC