Douraied Ben Salem

Quantification of Liver Fat Content: Comparison of Triple-Echo Chemical Shift Gradient-Echo Imaging and in Vivo Proton MR Spectroscopy

PURPOSE To validate a triple-echo gradient-echo sequence for measuring the fat content of the liver, by using hydrogen 1((1)H) magnetic resonance (MR) spectroscopy as the reference standard. MATERIALS AND METHODS This prospective study was approved by the appropriate ethics committee, and written informed consent was obtained from all patients. In 37 patients with type 2 diabetes (31 men, six women; mean age, 56 years), 3.0-T single-voxel point-resolved (1)H MR spectroscopy of the liver (Couinaud segment VII) was performed to calculate the liver fat fraction from the water (4.7 ppm) and methylene (1.3 ppm) peaks, corrected for T1 and T2 decay. Liver fat fraction was also computed from triple-echo (consecutive in-phase, opposed-phase, and in-phase echo times) breath-hold spoiled gradient-echo sequence (flip angle, 20 degrees), by estimating T2* and relative signal intensity loss between in- and opposed-phase values, corrected for T2* decay. Pearson correlation coefficient, Bland-Altman 95% limit of agreement, and Lin concordance coefficient were calculated. RESULTS Mean fat fractions calculated from the triple-echo sequence and (1)H MR spectroscopy were 10% (range, 0.7%-35.6%) and 9.7% (range, 0.2%-34.1%), respectively. Mean T2* time was 14.7 msec (range, 5.4-25.4 msec). Pearson correlation coefficient was 0.989 (P < .0001) and Lin concordance coefficient was 0.988 (P < .0001). With the Bland-Altman method, all data points were within the limits of agreement. CONCLUSION A breath-hold triple-echo gradient-echo sequence with a low flip angle and correction for T2* decay is accurate for quantifying fat in segment VII of the liver. Given its excellent correlation and concordance with (1)H MR spectroscopy, this triple-echo sequence could replace (1)H MR spectroscopy in longitudinal studies.

Imaging of nasopharyngeal cysts and bursae

Cysts and bursae of the nasopharynx are uncommon and seldom symptomatic when compared with malignant tumors of this region. However, it is noteworthy that in the presence of symptoms, a good knowledge of their radiological appearance is useful to establish the correct diagnosis. Cysts of Rathke’s pouch, pharyngeal bursa of Luschka, Tornwaldt’s cysts, retentional cysts of the seromucinous glands, oncocytic cysts, intra-adenoid cysts, branchial cysts, prevertebral or retropharyngeal abscess and pseudocysts of the nasopharynx will be discussed in this paper.

Multiple cysts of the corpus callosum and psychomotor delay in a patient with a 3.1 Mb 15q24.1q24.2 interstitial deletion identified by array-CGH.

We describe a 46‐month‐old child presenting with developmental delay, mild facial dysmorphism, micropenis, strabismus and striking multiple cysts of the corpus callosum who was found to have a de novo interstitial 3.1 Mb 15q24.1q24.2 microdeletion using a 244 K microarray‐based comparative genomic hybridization (array‐CGH). The cystic lesions were located in the anterior half of the corpus callosum and did not take up gadolinium contrast. There was no other brain abnormality, and the gyral pattern and myelination were normal. There was no history of infectious disease or vascular injury and a metabolic disease was ruled out. Such cystic lesions of the corpus callosum are exceptional in the pediatric literature. Although these brain abnormalities have not been described in other reports with 15q24 microdeletion, we believe that they might be related to the cytogenetic abnormality since the work‐up for other causes was negative. We suggest that a chromosomal rearrangement should be ruled out when such corpus callosum lesions are identified.

TUMOR VOLUME AND METABOLISM OF PROSTATE CANCER DETERMINED BY PROTON MAGNETIC RESONANCE SPECTROSCOPIC IMAGING AT 3T WITHOUT ENDORECTAL COIL REVEAL POTENTIAL CLINICAL IMPLICATIONS IN THE CONTEXT OF RADIATION ONCOLOGY

PURPOSE To determine whether a relationship exists between the tumor volume (TV) or relative choline content determined using magnetic resonance spectroscopy imaging (MRSI) at 3T and the clinical prognostic parameters for patients with localized prostate cancer (PCa). METHODS AND MATERIALS A total of 72 men (mean age, 67.8 ± 6.2 years) were stratified as having low-risk (n = 26), intermediate-risk (n = 24), or high-risk (n = 22) PCa. MRSI was performed at 3T using a phased-array coil. Spectra are expressed as the total choline/citrate, total choline plus creatine/citrate, and total choline plus polyamines plus creatine/citrate ratios. The mean ratio of the most pathologic voxels and the MRSI-based TV were also determined. RESULTS The mean values of the total choline/citrate, total choline plus creatine/citrate, and total choline plus polyamine plus creatine/citrate ratios were greater for Stage T2b or greater tumors vs. Stage T2a or less tumors: 7.53 ± 13.60 vs. 2.31 ± 5.65 (p = .018), 8.98 ± 14.58 vs. 2.56 ± 5.70 (p = .016), and 10.32 ± 15.47 vs. 3.55 ± 6.16 (p = .014), respectively. The mean MRSI-based TV for Stage T2b or greater and Stage T2a or less tumors was significantly different (2.23 ± 2.62 cm(3) vs. 1.26 ± 2.06 cm(3), respectively; p = .030). This TV correlated with increased prostate-specific antigen levels (odds ratio, 1.293; p = .012). Patients with high-risk PCa had a larger TV than did the patients with intermediate-risk PCa. A similar result was found for the intermediate-risk group compared with the low-risk group (odds ratio, 1.225; p = .041). CONCLUSION Biomarkers expressing the relative choline content and TV were significant parameters for the localization of PCa and could be helpful for determining the prognosis more accurately.

N -Acetylaspartate/Creatine and Choline/Creatine Ratios in the Thalami, Insular Cortex and White Matter as Markers of Hypertension and Cognitive Impairment in the Elderly

Our objective was to investigate the influence of hypertension on N-acetylaspartate (NAA) and choline (Cho) ratios in brain tissues in a community-dwelling elderly population. Brain flexibility was also evaluated with regard to the same metabolite ratios. Proton magnetic resonance spectroscopy (MRS) and the Trail Making Test (TMT) were performed in 80 subjects (75.7±4 years old) from the Three-City Study. Fifty-eight participants had hypertension. The NAA/creatine (Cr) and Cho/Cr ratios were obtained in the insular cortex, the thalami and the deep periventricular white matter. In addition, the B-A score of the TMT was evaluated. Uniand multi-variate analyses were performed in order to examine the relationships among these data. In the insula and the thalami of the hypertensive group, NAA/Cr ratios were significantly lower (1.39±0.23 and 1.52±0.23, respectively; p=0.01) than those in the normotensive control goup (1.52±0.25 and 1.70±0.19, respectively; p<0.0001), whereas no such reduction was observed in the periventricular white matter of older hypertensive brains. Moreover, the NAA or Cho ratios were significantly correlated with the TMT B-A scores at the level of the thalami, insula and periventricular white matter. These statistical results were confirmed by the multivariate analysis. In an elderly population, hypertension leads to a reduction in NAA/Cr ratios in the insula and the thalami, possibly due to a decrease in blood flow through small perforating and cortical arteries. The TMT B-A test appears to be relevant not only for the frontal areas but also for more remote areas such as the thalami, the insula and the deep periventricular white matter.

Liver methylene fraction by dual‐ and triple‐echo gradient‐echo imaging at 3.0T: Correlation with proton MR spectroscopy and estimation of robustness after SPIO administration

To assess the systematic errors in liver methylene fraction (LMF) resulting from fat–fat interference effects with dual‐ and triple‐echo gradient‐recalled‐echo Dual/Triple GRE) sequences and to test the robustness of these sequences after iron overloading.

Multiple cerebral and spinal cord cavernomas in Klippel-Trenaunay-Weber syndrome.

Klippel-Trenaunay-Weber syndrome (KTWS) is a rare syndrome in which patients harbor cutaneous hemangiomas, venous varicosities, and osseous-soft tissue hypertrophy of the affected limb. The clinical presentation of this syndrome is variable and the etiopathogenesis is presumably genetic in view of recent discoveries of RASA1 gene mutations in KTWS patients. Similarly, the KRIT1 gene is involved in pathogenesis of cavernous angiomas. Both RASA1 and KRIT1 genes interact with Rap1a protein, a member of the Ras family of guanosine triphosphatases (GTPases) signalling cellular adhesion. We report a 55-year-old male with KTWS harboring multiple cavernous angiomas in the thoracic spinal cord and the brainstem, as revealed by MRI. Angiography ruled out arteriovenous malformation. The patient was managed conservatively. The rarity of cavernous angiomas in KTWS and the possibilities of shared genetic pathways between KTWS and cavernous angiomas are discussed.

Involuntary masturbation and hemiballismus after bilateral anterior cerebral artery infarction

Ischemia of the areas supplied by the anterior cerebral artery is relatively uncommon. In addition, combined hemiballismus and masturbation have rarely been reported in patients with cerebrovascular disease. We describe herein a 62-year-old right-handed man simultaneously exhibiting right side hemiballismus and involuntary masturbation with the left hand after bilateral infarction of the anterior cerebral artery territory. Right side hemiballismus was related to the disruption of afferent fibers from the left frontal lobe to the left subthalamic nucleus. Involuntary masturbation using the left hand was exclusively linked to a callosal type of alien hand syndrome secondary to infarction of the right side of the anterior corpus callosum. After 2 weeks, these abnormal behaviours were completely extinguished. This report stresses the wide diversity of clinical manifestations observed after infarction of the anterior cerebral artery territory.

Value of spontaneous hyperdensity of cerebral venous thrombosis on helical CT.

Background Excluding a cerebral venous thrombosis (CVT) through imaging is a frequent request in the emergency setting. This assessment often starts by an unenhanced brain computed tomography (CT). Purpose Re-evaluate the value of spontaneous hyperdensity of CVT on helical unenhanced brain CT. Methods Multicentric retrospective study on CVT probability based on visual assessment of spontaneous hyperdensity of cerebral venous system, performed by four blinded radiologists, individually then collectively, on a population including 14 helical unenhanced brain CTs with CVT and 102 unenhanced brain CTs without CVT (all confirmed by CT or magnetic resonance [MR] venography). Exclusion criteria: no DICOM image, symptoms >15 days, CVT indirect signs on unenhanced CT. A fifth radiologist set 768 regions of interest to measure and to compare the density within the normal venous sinuses and the CVTs. Results After consensus reading, sensitivity of this sign for CVT diagnosis was 100%, specificity 95.1%, and negative predictive value (NPV) 100%, with high individual NPV (99–100%). Area under the receiver-operating characteristic curve was 0.992 after consensus (0.976–0.986 individually). The spontaneous density was significantly different (P <0.05) between normal sinuses and CVTs, with a density >70 HU reported only within the CVTs, except for the horizontal part of the superior sagittal sinus (hSSS). Conclusion The dense triangle sign on helical unenhanced brain CT has an excellent NPV to exclude a sinus thrombosis during the first 2 weeks. However, we believe that visual assessment of spontaneous hyperdensity is not sufficient for the diagnosis of CVT, with possible false-positive of the hSSS on unenhanced CT.

Hippocampus: a "forgotten" border zone of brain ischemia.

Hippocampus is selectively susceptible to ischemic damage and it could be, in some conditions, considered as a border zone of brain ischemia.