Michel Osteaux

Prevalence of thyroid hemiagenesis: Ultrasound screening in normal children

Abstract While performing a systematic ultrasound study of the thyroid gland volume for the evaluation of iodine deficiency in 2845 normal Belgian school children, we found an absence of the left lobe in 6 children (4 girls and 2 boys). There was no association with other thyroid malformations or dysfunction. Conclusion This first systematic ultrasound evaluation of thyroid hemiagenesis in normal children established a prevalence of thyroid hemiagenesis of 0.2% and confirmed the female predominance and higher incidence of agenesis of the left lobe.

Diffusion and perfusion MRI: basic physics.

Diffusion and perfusion MR imaging are now being used increasingly in neuro-vascular clinical applications. While diffusion weighted magnetic resonance imaging exploits the translational mobility of water molecules to obtain information on the microscopic behaviour of the tissues (presence of macromolecules, presence and permeability of membranes, equilibrium intracellular-extracellular water, ellipsis), perfusion weighted imaging makes use of endogenous and exogenous tracers for monitoring their hemodynamic status. The combination of both techniques is extremely promising for the early detection and assessment of stroke, for tumor characterisation and for the evaluation of neurodegenerative diseases. This article provides a brief review of the basic physics principles underlying the methodologies followed.

Posterolateral supporting structures of the knee: findings on anatomic dissection, anatomic slices and MR images

Abstract. In this article we study the ligaments and tendons of the posterolateral corner of the knee by anatomic dissection, MR-anatomic correlation, and MR imaging. The posterolateral aspect of two fresh cadaveric knee specimens was dissected. The MR-anatomic correlation was performed in three other specimens. The MR images of 122 patients were reviewed and assessed for the visualization of different posterolateral structures. Anatomic dissection and MR-anatomic correlation demonstrated the lateral collateral, fabellofibular, and arcuate ligaments, as well as the biceps and popliteus tendons. On MR images of patients the lateral collateral ligament was depicted in all cases. The fabellofibular, arcuate, and popliteofibular ligaments were visualized in 33, 25, and 38% of patients, respectively. Magnetic resonance imaging allows a detailed appreciation of the posterolateral corner of the knee.

Calcific tendinitis of the longus colli muscle: Case report

To the best of our knowledge, only one patient with calcium hydroxyapatite deposition disease (CHADD) of the longus colli muscle has been reported in the otolaryngology literature.

Prediction of splenic volume by a simple CT measurement: a statistical study.

The width, thickness, and areas of the spleen were obtained by abdominal computed tomography on 50 patients. Several simple linear equations were used to predict the splenic volume and were correlated with a previously published method for volume estimation based on summing areas of multiple contiguous scans. This was used as a standard and demonstrated an excellent linear correlation (r = 0.95) with an estimate based on a product of length and maximal width. Correlation was even better (r = 0.991) with an estimate based on length, maximal width, and thickness.

Study of pediatric brain development using magnetic resonance imaging of anisotropic diffusion

The properties of water diffusion in human brain tissue can be characterized by diffusion tensors computed from diffusion weighted magnetic resonance images. Since these properties are strongly determined by the structural and geometrical characteristics of the tissue, the maturation process of white matter and gray matter tissue can be expected to be reflected in these images and derived tensor quantities. The purpose of this work was therefore to study the development of pediatric brain in terms of changes occurring in the observed diffusion behavior. Echo planar diffusion tensor imaging was performed on 22 (10 females and 12 males) full term newborn and infant patients, diagnosed in retrospect as neurologically healthy. The subjects were subdivided in three age categories. A number of quantities based on the diffusion images were calculated for each tissue type and age category, and the ability of these quantities to provide sensitive and consistent information about the tissue differences and evolution was evaluated. The results clearly illustrate that the rotationally invariant quantities (e.g., the highest diffusivity, anisotropy ratio and volume ratio) are superior to the rotationally variant ones (e.g., ADCs measured along the three axes of the magnet) often used in the clinic. On the basis of the anisotropy ratio and the volume ratio indices, a correlation between the white matter maturation and the evolution of the diffusion anisotropy could be established. The same quantities did not exhibit any age dependence for the gray matter tissues.

Pituitary microadenomas: diagnosis with dynamic serial CT, conventional CT and T1-weighted MR imaging before and after injection of gadolinium.

PURPOSE The few studies comparing CT and MR in the diagnosis of pituitary microadenomas give discordant results. This prospective study compares the value of dynamic serial CT (DSCT), conventional CT (CCT), pre-Gd T1-weighted spin echo (T1SE-Gd) and post-Gd T1-weighted SE (T1SE+Gd) in the detection of pituitary microadenomas. METHODS The value of CT and MR was assessed in 17 cases, with the surgical confirmation as reference. The CTs and MRs were independently and blindly evaluated by two neuroradiologists. Because the finding at MR and/or CT influenced the selection of patients for surgery, the positive predictive value was calculated. The sensitivity calculation applies only for a specific group of postsurgical patients with positive CT and/or MR (marked with an asterisk for these reasons). RESULTS In this study, the highest sensitivity* (88% and 82%, respectively, for observers I and II) was achieved by DSCT. The T1SE-Gd and T1SE+Gd (evaluated separately) were slightly inferior (sensitivity* of 76% for observer I). The combination of T1SE-Gd with T1SE+Gd improved the sensitivity* to 94% and 82% respectively, for observers I and II. There was also moderate improvement of sensitivity* by combination of DSCT with conventional CT (94% for observer I). CONCLUSION These results suggest that rapid injection of a large amount of contrast conjointly with a fast scanning through the pituitary is crucial for the confident detection of microprolactinomas. Taking into account the similar results of the combination DSCT + CT and T1SE-Gd + T1SE+Gd in the detection of microprolactinomas, high field MRI is the first step modality in the evaluation of presumed hypophyseal hyperprolactinemia.

Size of cortical bone and relationship to bone mineral density assessed by quantitative computed tomography image segmentation

&NA; Louis O, van den Winkel P, Covens P, Schoutens A, Osteaux M. Size of cortical bone and relationship to bone density assessed by quantitative computed tomography image segmentation. Invest Radiol 1993;28:802‐805. rationale and objectives. The accuracy of the measurement of the size of cortical bone on computed tomography (CT) images of human vertebrae was evaluated using an automated contour detection and segmentation procedure. methods. Forty human lumbar vertebrae were scanned using 8‐mm slices and an automated detection for definition of trabecular and cortical region of interest. The vertebrae were embedded in a polyester resin and 8‐mm‐thick midvertebral specimens were excised using a diamond circular saw. Contact radiographs of these specimens were performed and, after photograph magnification, the cortical area was measured using computerized planimetry. results. Cortical area measured on CT images was highly correlated with the area measured by planimetry on the specimens (r = .91; P < .001) with, however, a systematic overestimation. A significant relationship was found between density and width of the cortex (r = .56; P < .001). conclusions. Computed tomography is able to assess the size of cortical bone in human vertebrae, but a threshold detection algorithm, as used in the current study, is not adequate to obtain the precise anatomic dimensions.

Echo planar magnetic resonance imaging of anisotropic diffusion in asparagus stems

MR diffusion-weighted imaging (DWI) uses the signal loss associated with the random thermal motion of water molecules in the presence of magnetic field gradients to derive a number of parameters that reflect the translational mobility of the water molecules in tissues. In highly organized but asymmetric structures, this mobility may be affected by the obstacles present and this in a direction-dependent way. Important examples of this are white brain matter and the stem of certain plants, both containing fibrous components where diffusion of water molecules across fibers is much more restricted than along the fibers. Diffusion that exhibits such directional dependence is said to be anisotropic, and diffusion tensor magnetic resonance imaging allows localized characterization of this behavior. Interpretation of the information obtained in terms of the underlying tissue structure is often hampered by the complexity of factors that can produce the observed behavior. A phantom that exhibits well-defined anisotropic diffusion and yields sufficient signal can help the experimental testing of the relevant methods and models. In this paper, we have used a phantom consisting of asparagus stems as a test object for assessing the value of the acquisition and postprocessing techniques commonly used in the clinic for this kind of investigation. Because of its strongly fibrous and cylindrically symmetric morphology, exhibiting a well-defined sub-classification of cells on the basis of size and shape, asparagus allows a relatively simple interpretation of the results obtained in the diffusion experiments. Our experiments show that the known structural information about the main cell types encountered correlates well with the behavior patterns of the diffusion parameters.

Peroneal nerve injury in three patients with knee trauma: MR imaging and correlation with anatomic findings in volunteers and anatomic specimens

Abstract.The aim of this article is to report on three patients with injuries of the peroneal nerve along the posterolateral aspect of the knee. Injuries in this area are less common than the injuries occurring at the level of the fibular head. In this article we report on three patients with posterolateral knee trauma who had peroneal nerve dysfunction. To better understand the precise location of the nerve on MR images, we performed MR imaging in five volunteers, and studied the position of the nerve on anatomic dissection (n=1) and anatomic slices (n=1). The common peroneal nerve is easily depicted on MR images and has a typical location along the posterior margin of the biceps tendon. Non-visualisation of the peroneal nerve at the posterolateral aspect of the knee, as seen on MR images, is consistent with nerve injury. Scar tissue at the posterolateral aspect of the knee indicates injury of this specific area, and involvement of the peroneal nerve is likely.