[Discoscanner: indications, technique, tips and tricks, interpretation]. / Discoscanner: indications, technique, trucs et astuces, interprétation.

Discography test associated with the scanner (discoscanner) is an exam that has been a renewed interest in recent few years. Thanks to the emergence of new interventions such as disc prosthesis, the procedures require confirmation of the disc level to deal with and the origin of discogenic symptoms. The aim of this paper is to describe the techniques, challenges and tips as well as the interpretation of functional and morphological examination.

Renal blood flow quantification in pigs using contrast-enhanced ultrasound: an ex vivo study.

PURPOSE: The aim of the study was to evaluate a new method for the quantification of renal blood flow using contrast-enhanced ultrasound (CEUS) in an ex vivo pig kidney model. MATERIAL AND METHODS: After approval by the animal ethics committee, 4 pig kidneys were explanted and perfused with Celsior liquid (Imtix Sangstat, Lyon, France) at different flow rates (30, 50, 70 and 90 ml/min) in an ex vivo phantom. A 50 % diluted solution of SonoVue (Bracco, Milano, Italy) was infused in the artery at 0.5 ml/min. CEUS was performed with an Aplio system (Toshiba, Nasu, Japan) using a broadband linear transducer and pulse subtraction imaging. A total of 152 destruction-reperfusion sequences were acquired and cine loops were digitally stored for further quantification. Three different ROIs were placed upon the anterior, posterior cortex and segmental artery. Signal intensity measurements were performed in linear units and perfusion parameters were automatically extracted using dedicated software. Curve fitting was performed using a monoexponential model in which a time delay parameter was introduced. This fit allowed the assessment of the local blood flow into the region of interest (called "contrast-enhanced blood flow" (CEBF)). The artery mean signal intensity was averaged from the ten frames prior to the destruction phase. The normalized CEBF (nCEBF) was calculated as the ratio between CEBF and the mean arterial signal intensity. The CEBF and nCEBF were compared to the true blood flow indicated by the pump flow rate. RESULTS: The CEBF was correlated to the true blood flow only for the posterior cortical ROI (R(2) = 0.45, p = 0.05). The normalization using arterial signals improved CEBF correlation to true blood flow: nCEBF became correlated to the true blood flow when considering all ROIs (R(2)= 0.94, p < 0.0001) and correlation was improved for both anterior and posterior cortical ROIs (R(2)= 0, 93, p = 0.0004; R(2)= 0, 90, p = 0.0005, respectively). However, a significant kidney-dependent effect was observed for the anterior cortical ROI (p = 0.017) but not for the posterior cortical ROI (p = 0.89). CONCLUSION: Normalization using arterial signals significantly improved the estimation of blood flow calculated with CEUS.

MR elastography.

Magnetic resonance (MR) elastography is an emerging method for measuring the viscoelastic properties of tissues. Hepatic fibrosis, which increases the elasticity or stiffness of the liver, can be detected and staged by MR elastography. The technique has several advantages compared with transient ultrasound elastography (FibroScan): it can evaluate much larger liver volumes; it can be performed in obese patients and in those with ascites; and it can assess the full three-dimensional displacement vector, allowing a more precise analysis of viscoelastic parameters. These technical advantages mean that MR elastography is more accurate forstaging liver fibrosis than is transient ultrasound elastography. Moreover, it has been shown in animal studies using MR elastography that parameters other than fibrosis can also increase liver elasticity, including inflammation and myofibroblast activation before extracellular matrix deposition. Because of its greater accuracy-but also its higher cost-MR elastography will probably have a complementary role alongside ultrasound elastography. Nevertheless, this role should be further studied, especially in terms of response to treatment and the early detection of chronic liver diseases such as steatohepatitis.

Head and neck paragangliomas: value of contrast-enhanced 3D MR angiography.

BACKGROUND AND PURPOSE: A rapid and accurate MR imaging technique would be beneficial to assess paragangliomas in the head and neck and to distinguish them from other lesions. The purpose of this study was to determine whether the combination of elliptic centric contrast-enhanced MR angiography (CE-MRA) and unenhanced and enhanced spin-echo imaging (conventional MR imaging) is more accurate than conventional MR imaging alone to assess paragangliomas in the head and neck. MATERIALS AND METHODS: Three radiologists retrospectively and independently reviewed CE-MRA and conventional MR imaging in 27 patients with suspected paragangliomas. The overall image quality and the probability of paraganglioma were recorded. The results of each technique and their combination were analyzed for sensitivity and specificity. Receiver operating characteristic (ROC) analyses were performed by using histologic analysis, imaging, and/or clinical findings as the reference standard. RESULTS: Forty-six lesions were found in 27 patients. In the assessment of paragangliomas, the combination of conventional MR imaging and CE-MRA was significantly superior to conventional MR imaging alone. Sensitivity and specificity respectively were the following: for CE-MRA, 100% and 94%; and for conventional MR imaging, 94% and 41%. The specificity of CE-MRA was significantly higher than that of conventional MR imaging (P = .004). There was good-to-excellent interobserver agreement for the paraganglioma probability with CE-MRA (nonweighted kappa, 0.67-0.77), whereas there was fair-to-good interobserver agreement with conventional MR imaging (nonweighted kappa, 0.50-0.65). CONCLUSION: In combination with conventional MR imaging, CE-MRA yields an excellent diagnostic value for the assessment of head and neck paragangliomas; hence, the 2 techniques should be regarded as complementary.

[Magnetic resonance imaging of angiogenesis in tumors]. / Imagerie par résonance magnétique de l'angiogenèse tumorale.

Tumor angiogenesis induces the proliferation of immature blood vessels that are both heterogeneous and leaky. These characteristics can be demonstrated by measuring the perfusion parameters with MRI. Perfusion MRI is usually performed with in T1-weighted dynamic imaging after bolus injection of an exogenous contrast agent such as gadolinium chelate. The perfusion parameters are obtained by semi-quantitative or quantitative analysis of the enhancement curves in the tumor and the arterial input. Perfusion can also be assessed without injecting a contrast agent using arterial spin labeling techniques, diffusion MRI, or BOLD (blood oxygen level dependent) MRI. However, these latter methods are limited by a low signal-to-noise ratio and problems with quantification. The main indication for perfusion MRI is the assessment of antiangiogenic and antivascular treatments. New possibilities for demonstrating angiogenic blood vessels are being opened by molecular imaging.

[What is the thickness of the normal appendix on MDCT?]. / Quelle est l'épaisseur de l'appendice normal au scanner multibarrette?

OBJECTIVE: To determine the wall thickness and external diameter values of the normal appendix on multidetector computed tomography (MDCT). Materials and methods. A senior radiologist with no knowledge of the patient's surgical history prospectively examined the abdominal-pelvic CT scans of 57 consecutive adult patients with no suspicion for appendicitis. Most of the patients (50/57) received an intravenous iodinated contrast material injection, but none had gastrointestinal studies. All slices (1 and 5 mm) and multiplanar reconstructions were analyzed on a treatment console. The external diameter of the appendix, the thickness of the two appendicular walls, and the presence or absence of intraluminal gas were noted. RESULTS: The appendix was visualized in 82% of the cases (47/57). The mean external diameter was 6.7 mm+/-1.2 (range, 5.0-11.0 mm). The mean thickness of the two walls was 4.8 mm+/-1.0 (range, 2.6-6.4 mm). Intraluminal air was visualized in 87% of cases (41/47). CONCLUSION: Contrary to external diameter, the normal thickness of the appendix's two walls does not go beyond the threshold of 6 mm and therefore seems to be a reliable measurement for identifying a normal appendix using MDCT.

[Is appendicolith a reliable sign for acute appendicitis at MDCT?]. / Le stercolithe est-il un signe fiable d'appendicite?

PURPOSE: To determine the frequency of detection of appendicoliths on normal appendix at multidetector row computed tomography (MDCT) with multiplanar reconstructions (MPR). MATERIALS AND METHODS: A senior radiologist, blinded to patient's surgical history, prospectively and independently reviewed abdominopelvic MDCT scans in 57 consecutive adult patients without symptoms suggesting appendicitis. Most patients had IV iodine injection, but no oral contrast. Thick (5 mm) and thin (1 mm) slices were analyzed on a workstation. MPR were available. Localization of the appendix, overall diameter, intraluminal gas and appendicolith were recorded. RESULTS: The appendix was visualized in 47/57 (82%). An appendicolith was found in 13%. Intraluminal gas was identified in 87%. The localization was retrocaecal (47%), mediocaecal (21%) or pelvic (32%). The mean overall diameter of the normal appendix was 6.7 mm +/- 1.2 (SD). CONCLUSION: Appendicolith was found in a significant number of normal patients at MDCT and don't represent a specific sign for appendicitis.