P.M. Parizel

Nonrigid Coregistration of Diffusion Tensor Images Using a Viscous Fluid Model and Mutual Information

In this paper, a nonrigid coregistration algorithm based on a viscous fluid model is proposed that has been optimized for diffusion tensor images (DTI), in which image correspondence is measured by the mutual information criterion. Several coregistration strategies are introduced and evaluated both on simulated data and on brain intersubject DTI data. Two tensor reorientation methods have been incorporated and quantitatively evaluated. Simulation as well as experimental results show that the proposed viscous fluid model can provide a high coregistration accuracy, although the tensor reorientation was observed to be highly sensitive to the local deformation field. Nevertheless, this coregistration method has demonstrated to significantly improve spatial alignment compared to affine image matching.

The correlation of preoperative CT, MR imaging, and clinical staging (FIGO) with histopathology findings in primary cervical carcinoma

The aim of this study was to compare the preoperative findings of abdominal/pelvic CT and MRI with the preoperative clinical International Federation of Obstetrics and Gynecology (FIGO) staging and postoperative pathology report in patients with primary cancer of the cervix. Thirty-six patients with surgical–pathological proven primary cancer of the cervix were retrospectively studied for preoperative staging by clinical examination, CT, and MR imaging. Studied parameters for preoperative staging were the presence of tumor, tumor extension into the parametrial tissue, pelvic wall, adjacent organs, and lymph nodes. The CT was performed in 32 patients and MRI (T1- and T2-weighted images) in 29 patients. The CT and MR staging were based on the FIGO staging system. Results were compared with histological findings. The group is consisted of stage 0 (in situ):1, Ia:1, Ib:8, IIa:2, IIb:12, IIIa:4, IVa:6, and IVb:2 patients. The overall accuracy of staging for clinical examination, CT, and MRI was 47, 53, and 86%, respectively. The MRI incorrectly staged 2 patients and did not visualize only two tumors; one was an in situ (stage-0) and one stage-Ia (microscopic) disease. The MRI is more accurate than CT and they are both superior to clinical examination in evaluating the locoregional extension and preoperative staging of primary cancer of the cervix.

Distribution and incidence of degenerative spine changes in patients with a lumbo-sacral transitional vertebra

The purpose of this prospective study was to determine the overall incidence and distribution of lumbo-sacral degenerative changes (i.e. disc protrusion or extrusion, facet degeneration, disc degeneration, nerve root canal stenosis and spinal stenosis) in patients with and without a lumbo-sacral transitional vertebra (LSTV). The study population consisted of 350 sequential patients with low back pain and/or sciatica, referred for medical imaging. In all cases CT scans of the lumbosacral region were obtained. In 53 subjects (15%) an LSTV was found. There was no difference in overall incidence of degenerative spine changes between the two groups. We did find, however, a different distribution pattern of degenerative changes between patients with and those without an LSTV Disc protrusion and/or extrusion occurred more often at the level suprajacent to the LSTV than at the same level in patients without LSTV (45.3% vs 30.3%). This was also the case for disc degeneration (52.8% vs 28%), facet degeneration (60.4% vs 42.6%) and nerve root canal stenosis (52.8% vs 27.9%). For spinal canal stenosis there was no statistically significant difference between the two categories. In conclusion, our findings indicate that an LSTV does not in itself constitute a risk factor for degenerative spine changes, but when degeneration occurs, it is more likely to be found at the disc level above the LSTV.

The value of MRI in the diagnosis of postoperative spondylodiscitis

Abstract We evaluated the role of MRI in the diagnosis of postoperative spondylodiscitis. Spondylodiscitis is a serious complication of surgery, and the diagnosis frequently depends on a combination of clinical, laboratory and imaging findings. We compared the MRI findings in six patients with biopsy- or surgery-proven spondylodiscitis with those in 38 asymptomatic postoperative patients. Contrast enhancement and signal changes in the intervertebral disc or the vertebral endplates are not specific for spondylodiscitis, being also seen in the asymptomatic patients. However, absence of Modic type 1 changes, of contrast enhancement of the disc or of enhancing paravertebral soft tissues suggests that the patient does not have spondylodiscitis. MRI appears more useful for exclusion than for confirmation of postoperative spondylodiscitis.

Randomised double blind trial of the safety and efficacy of two gadolinium complexes (Gd-DTPA and Gd-DOTA)

The main difference between macrocyclic Gd-DOTA and linear Gd-DTPA complexes is the greater stability of the former which theoretically might reduce biological interactions in man. To evaluate the clinical relevance of this property, 300 unselected neurological patients were included in a randomised double-blind comparison involving five European centres, focused mainly on the tolerance of these two contrast media. Clinical tolerance was assessed immediatley after the procedure and 24 h later. Adverse events were found with a similar frequency in the two groups (17.3% for Gd-DOTA and 19.3% for Gd-DTPA). Minor neurological symptoms were the most frequent (48.6%) headache being the most common (29.2% of adverse events). No difference in efficacy was found.

Functional MRI of the cervical spinal cord on 1.5 T with fingertapping: to what extent is it feasible?

IntroductionUntil recently, functional magnetic resonance imaging (fMRI) with blood oxygen level-dependent (BOLD) contrast, was mainly used to study brain physiology. The activation signal measured with fMRI is based upon the changes in the concentration of deoxyhaemoglobin that arise from an increase in blood flow in the vicinity of neuronal firing. Technical limitations have impeded such research in the human cervical spinal cord. The purpose of this investigation was to determine whether a reliable fMRI signal can be elicited from the cervical spinal cord during fingertapping, a complex motor activity. Furthermore, we wanted to determine whether the fMRI signal could be spatially localized to the particular neuroanatomical location specific for this task.MethodsA group of 12 right-handed healthy volunteers performed the complex motor task of fingertapping with their right hand. T2*-weighted gradient-echo echo-planar imaging on a 1.5-T clinical unit was used to image the cervical spinal cord. Motion correction was applied. Cord activation was measured in the transverse imaging plane, between the spinal cord levels C5 and T1.ResultsIn all subjects spinal cord responses were found, and in most of them on the left and the right side. The distribution of the activation response showed important variations between the subjects. While regions of activation were distributed throughout the spinal cord, concentrated activity was found at the anatomical location of expected motor innervation, namely nerve root C8, in 6 of the 12 subjects.ConclusionfMRI of the human cervical spinal cord on an 1.5-T unit detects neuronal activity related to a complex motor task. The location of the neuronal activation (spinal cord segment C5 through T1 with a peak on C8) corresponds to the craniocaudal anatomical location of the neurons that activate the muscles in use.

CT diagnosis and differential diagnosis of otodystrophic lesions of the temporal bone

The purpose of this study was to assess the diagnostic and differential value of high-resolution computed tomography in the evaluation of temporal-bone dystrophies. The study group included 55 patients with osseous abnormalities of the temporal bone in general, and the labyrinthine capsule in particular. In 27 patients the CT scan revealed evidence of otodystrophic lesions. The CT findings in patients with otosclerosis (21 patients), osteogenesis imperfecta (two patients), fibrous dysplasia (one patient), Pagets disease (one patient) and osteopetrosis (two patients) are described. The CT scans of 17 patients revealed secondary osseous lesions due to metastasis (five patients), post-inflammatory changes (10 patients) or labyrinthitis ossificans (two patients). Normal variants and congenital mineralization defects were diagnosed in nine patients, Downs syndrome in two. Our results indicate the importance of high-resolution computed tomography as the primary imaging modality in evaluating osseous lesions of the temporal bone and labyrinth.

The value of magnetic resonance imaging in the differentiation between malignant peripheral nerve-sheath tumors and non-neurogenic malignant soft-tissue tumors

ObjectiveTo assess the sensitivity and specificity of MRI criteria in the differentiation between malignant peripheral nerve sheath tumors (MPNST) and non-neurogenic malignant soft-tissue tumors (MSTT).Design and patientsMRI examinations of 105 patients with pathologically proven malignant soft-tissue lesions (35 MPNST and 70 MSTT) were retrospectively reviewed, the reviewers being unaware of the pathological diagnosis. Using a standardized protocol, the tumors were evaluated for multiple parameters regarding morphology and appearance on different sequences before and after gadolinium contrast administration (location, distribution, delineation, homogeneity, size, shape, relationship to bone and neurovascular bundle, intralesional hemorrhage, necrosis, perilesional edema, lymphangitis and signal intensities). Results were compared using a chi-square or Fisher’s exact test.ResultsMRI findings suggestive of MPNST (p<0,05) were intermuscular distribution, location on the course of a large nerve, nodular morphology, and overall non-homogeneity on T1-weighted images, T2-weighted images and T1-weighted images after gadolinium contrast injection. MRI findings in favor of MSTT were intramuscular distribution, ill-delineated appearance of more than 20% of the lesion’s circumference, and presence of intralesional blood vessels, perilesional edema and lymphangitis. There is no significant difference for degree and pattern of enhancement after gadolinium contrast injection, nor for presence of bone involvement or cystic or necrotic areas.ConclusionMRI provides several features that contribute to the differentiation between MPNST and non-neurogenic malignant soft-tissue tumors. MRI findings suggestive of MPNST should be helpful to pathologists in the strategy for further examination.

Hereditary neuromuscular diseases

This article presents the actual classification of neuromuscular diseases based on present expansion of our knowledge and understanding due to genetic developments. It summarizes the genetic and clinical presentations of each disorder together with CT findings, which we studied in a large group of patients with neuromuscular diseases. The muscular dystrophies as the largest and most common group of hereditary muscle diseases will be highlighted by giving detailed information about the role of CT and MRI in the differential diagnosis. The radiological features of neuromuscular diseases are atrophy, hypertrophy, pseudohypertrophy and fatty infiltration of muscles on a selective basis. Although the patterns and distribution of involvement are characteristic in some of the diseases, the definition of the type of disease based on CT scan only is not always possible.

Additional value of magnetic resonance with spin echo T1-weighted imaging with fat suppression in characterization of soft tissue tumors.

Objective: The aim of the study was to describe the signal intensity (SI) behavior of soft tissue tumors (STT) on spin echo (SE) T1 weighted images (WI) with fat suppression (FS) and to assess its additional value in tissue characterization. Methods: MRI signal characteristics of 53 histological proven STT were discussed. Signal intensity behavior of STT could be classified in 4 types, representing specific tissues or tissue components. Type 1 was defined as low SI on both SE T1‐WI and SE T1‐WI with FS. Type 2 was defined as high SI on both sequences. Type 3 consisted of high SI on T1‐WI and low SI on T1‐WI with FS. Type 4 was defined as SI comparable with SI of normal muscle on T1‐WI and SI higher than normal muscle on T1‐WI with FS. The additional information concerning contrast enhancement is described. Results: Type 1 SI behavior was noted in fibrous lesions, in hemosiderotic components, cysts, and myxoma. Type 2 was noted in lesions containing methemoglobin or melanin. Type 3 was specific for fatty tissue. Type 4 was noted in highly cellular parts and in lesions of vascular origin. The use of SE T1‐WI with FS improved lesion conspicuity on T1‐WI. Conclusion: SE T1‐WI with FS has additional value in the characterization of fibrous and hemosiderotic parts from cellular parts of lesions. It gives more confidence in characterization of neurogenic tumors and hemangiomas. Presence of methemoglobin and melanin are clearly discriminated from fatty tissue. Tumor conspicuity and inhomogeneity evaluation is improved. The use of SE T1‐WI FS not only improves tumor conspicuity, but as tumor homogeneity and SI are important parameters in staging and characterization of STT, the use of SE T1‐WI with FS will certainly be helpful. This may obviate the need for gadolinium administration. Index Terms: soft tissues, MR; soft tissues, neoplasms; sarcoma; magnetice resonance (MR) tissue characterization; magnetic resonance (MR) fat suppression.