Jean-François Budzik

Diffusion tensor imaging and fibre tracking in cervical spondylotic myelopathy

ObjectivesTo (1) obtain microstructural parameters (Fractional Anisotropy: FA, Mean Diffusivity: MD) of the cervical spinal cord in patients suffering from cervical spondylotic myelopathy (CSM) using tractography, (2) to compare DTI parameters with the clinical assessment of these patients (3) and with information issued from conventional sequences.MethodsDTI was performed on 20 symptomatic patients with cervical spondylotic myelopathy, matched with 15 volunteers. FA and MD were calculated from tractography images at the C2-C3 level and compressed level in patients and at the C2-C3 and C4-C7 in controls. Patients were clinically evaluated using a self-administered questionnaire.ResultsThe FA values of patients were significantly lower at the compressed level than the FA of volunteers at the C4-C7 level. A significant positive correlation between FA at the compressed level and clinical assessment was demonstrated. Increased signal intensity on T2-weighted images did not correlate either with FA or MD values, or with any of the clinical scores.ConclusionFA values were significantly correlated with some of the patients’ clinical scores. High signal intensity of the spinal cord on T2 was not correlated either with the DTI parameters or with the clinical assessment, suggesting that FA is more sensitive than T2 imaging.

Tractography of lumbar nerve roots: initial results

ObjectivesThe aims of this preliminary study were to demonstrate the feasibility of in vivo diffusion tensor imaging (DTI) and fibre tracking (FT) of the lumbar nerve roots, and to assess potential differences in the DTI parameters of the lumbar nerves between healthy volunteers and patients suffering from disc herniation.MethodsNineteen patients with unilateral sciatica related to posterolateral or foraminal disc herniation and 19 healthy volunteers were enrolled in this study. DTI with tractography of the L5 or S1 nerves was performed. Mean fractional anisotropy (FA) and mean diffusivity (MD) values were calculated from tractography images.ResultsFA and MD values could be obtained from DTI-FT images in all controls and patients. The mean FA value of the compressed lumbar nerve roots was significantly lower than the FA of the contralateral nerve roots (p = 0.0001) and of the nerve roots of volunteers (p = 0.0001). MD was significantly higher in compressed nerve roots than in the contralateral nerve root (p = 0.0002) and in the nerve roots of volunteers (p = 0.04).ConclusionDTI with tractography of the lumbar nerves is possible. Significant changes in diffusion parameters were found in the compressed lumbar nerves.

Tractography of peripheral nerves and skeletal muscles

The assessment of human peripheral nerves and skeletal muscles by means of diffusion tensor imaging and tractograpy has been a recent area of research. These techniques have been successfully applied in both volunteers and patients, providing non-invasively, quantitative microstructural parameters (mainly mean fractional anisotropy and apparent diffusion coefficient) and offering a three-dimensional visualization tool of nerves and muscles fibers. DTI and tractography may reveal abnormalities that are beyond the resolution of conventional MR techniques and hence open the way to potential clinical applications. In this article, we will first summarize the current state of DTI and tractography in the evaluation of peripheral nerves and skeletal muscles as well as their potential future clinical applications. Then, we will address important technical considerations, which understanding is necessary to appropriately apply DTI and tractograhy, and in order to understand the current limitations of these innovative and promising techniques.

In Vivo Diffusion Tensor Imaging and Tractography of Human Thigh Muscles in Healthy Subjects

OBJECTIVE The aims of this study were to assess whether similar measurements of mean apparent diffusion coefficient and fractional anisotropy in muscles can be obtained with regions of interest drawn on cross-sectional diffusion tensor images and tractography and to assess whether water diffusivity in human thigh muscles is influenced by muscular compartment, age, and sex. SUBJECTS AND METHODS Sixteen healthy volunteers (eight women, eight men) participated in this study. The right thigh of each subject was imaged with diffusion tensor imaging, and the mean apparent diffusion coefficient and fractional anisotropy values were calculated for each muscle of the quadriceps femoris and hamstrings. Fiber tracking was performed with a line propagation technique from the regions of interest drawn on cross-sectional diffusion tensor images. RESULTS The water diffusivity parameters obtained with tractography did not differ significantly from those obtained with diffusion tensor imaging in the three regions of interest evaluated in each muscle. The mean apparent diffusion coefficient of women (1.80 × 10⁻³ mm²/s) was similar to that of men (1.79 × 10⁻³ mm²/s). Women and men had identical fractional anisotropy values (0.26). The fractional anisotropy value in young volunteers (0.27) was similar to that in older subjects (0.26). The hamstrings had a lower mean apparent diffusion coefficient (1.64 × 10⁻³ mm²/s) than the quadriceps femoris (1.91 × 10⁻³ mm²/s), but the quadriceps femoris had a significantly lower fractional anisotropy value (0.25) than the hamstrings (0.28). CONCLUSION Our study showed that the water diffusivity values (mean apparent diffusion coefficient and fractional anisotropy) of the thigh muscles did not differ significantly with respect to sex or age of the subject. The quadriceps femoris and the hamstrings did have different mean apparent diffusion coefficient and fractional anisotropy values, which may reflect differences in hydration and muscular architecture.

Diffusion Tensor Imaging in Musculoskeletal Disorders

Diffusion tensor (DT) imaging is an emerging magnetic resonance (MR) imaging technique for evaluating the microstructure of well-organized biologic tissues such as muscles and nerves. DT imaging provides information about tissue microstructure by producing three-dimensional maps of water molecule movements. The two main parameters of measurement at DT imaging, fractional anisotropy and the apparent diffusion coefficient, allow quantitation of architectural changes occurring in tissue. These parameters are modified in the presence of cervical spondylotic myelopathy, cervical spine trauma, carpal tunnel syndrome, lumbar nerve compression, peripheral nerve tumors, and muscle ischemia. Their alteration may be observed at DT imaging even when no abnormality is seen at conventional MR imaging, a fact that suggests that DT imaging allows the detection of abnormalities at an earlier stage of injury. Experimental studies in animals have shown that DT imaging consistently allows identification of pathophysiologic alterations in tissue that correlate with histologic findings. Tractographic images accurately depict both normal and abnormal diffusion in anatomic structures such as the thigh and pelvic muscles, cervical spine, and lumbar nerves. Patients with chronic diseases also may benefit from follow-up evaluation with DT imaging, although DT imaging sequences must be further adapted to improve the evaluation of specific anatomic regions by reducing artifacts, optimizing spatial resolution, and minimizing acquisition time. Given its proven potential for use in identifying abnormalities that are otherwise identifiable only with electrophysiologic and histopathologic studies, and with future technical improvements, DT imaging could soon become a standard method for early diagnosis, management, and follow-up of disease in the spine, muscles, and peripheral nerves.

Skeletal involvement in Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) represents a disorder characterised by an abnormal accumulation of histiocytes in miscellaneous tissues. The bone is commonly affected, especially the flat bones, the spine and the long bones. Some lesions in children such as a “vertebra plana” or a solitary lytic lesion of the skull may be suggestive for LCH, whereas others can be confused with a malignant tumour or osteomyelitis. This pictorial essay presents the main usual and unusual skeletal manifestations observed in LCH.Teaching points• Osseous involvement in children with LCH is very similar to that seen in multiple myeloma.• A solitary lytic lesion of the cranial vault is a typical radiographic finding of LCH.• A vertebra plana appearance in the spine is another typical radiographic finding.• Extensive signal intensity changes within bone marrow on MRI are a helpful sign for the diagnosis.• In long bones, endosteal scalloping may be responsible for a “budding appearance”.

Geometrical analysis results of 42 resurfacing shoulder prostheses: A CT scan study

BACKGROUND Shoulder resurfacing arthroplasty was introduced in Scandinavia in the early 1980s then developed by SA Copeland. HYPOTHESIS Resurfacing prostheses restore the normal anatomy of the proximal humerus. Here, our objective was to evaluate humeral resurfacing prosthesis position on radiographs and computed tomography (CT) images. MATERIALS AND METHODS We retrospectively reviewed 42 consecutive cases seen at a single centre between 2004 and 2009. Mean patient age was 65 years. CT was performed routinely before prosthesis implantation and at re-evaluation. The Copeland Mark III(®) (Biomet France SARL, 26903 Valence, France) implant was used in 32 cases and the Aequalis Resurfacing Head(®) (Tornier France, 38334 Saint-Ismier, France) in 10 cases. The post-implantation CT images were used to measure the angle of inclination, medial humeral offset, lateral glenohumeral offset, and version of the implant. RESULTS Mean follow-up was 18 months. Compared to baseline, no significant changes were found at re-evaluation for the angle of inclination or lateral glenohumeral offset. In contrast, medial humeral offset increased by 3.47mm, and excessive anteversion of 4.23° compared to the bicondylar line was noted. DISCUSSION Humeral head resurfacing prostheses restore the overall anatomy of the proximal humeral head. Our CT scan evaluation protocol seems reproducible and enables an evaluation of implant geometry. In our experience, resurfacing arthroplasty restored the native humeral offset. Inadequate retroversion was noted and was probably related to insufficient exposure during surgery. LEVEL OF EVIDENCE Level IV, retrospective study.

Region specific Raman spectroscopy analysis of the femoral head reveals that trabecular bone is unlikely to contribute to non-traumatic osteonecrosis

Non-traumatic osteonecrosis (ON) of the femoral head is a common disease affecting a young population as the peak age of diagnosis is in the 40 s. The natural history of non-traumatic ON leads to a collapse of the femoral head requiring prosthetic replacement in a 60% of cases. Although trabecular bone involvement in the collapse is suspected, the underlying modifications induced at a molecular level have not been explored in humans. Here, we examine changes in the molecular composition and structure of bone as evaluated by Raman spectroscopy in human end-stage ON. Comparing samples from femoral heads harvested from 11 patients and 11 cadaveric controls, we show that the mineral and organic chemical composition of trabecular bone in ON is not modified apart from age-related differences. We also show that the molecular composition in the necrotic part of the femoral head is not different from the composition of the remaining ‘healthy’ trabecular bone of the femoral head. These findings support that quality of trabecular bone is not modified during ON despite extensive bone marrow necrosis and osteocyte death observed even in the ‘healthy’ zones on histological examination.

Tractography: Possible Applications in Musculoskeletal Radiology.

Tractography (or fiber tracking) consists of three-dimensional modeling of the preferential movement of water molecules in the form of fiber tracks from the tensor field information. This technique allows a new approach for the microarchitectural analysis of anisotropic structures such as nerves, white matter, and muscles. Many disorders have been studied including cervical myelopathy, carpal tunnel syndrome, nerve root compression, and nerve tumors. Muscles have been less evaluated. Tractography is still a research technique, and its validation and widespread routine clinical use will require a good deal of work toward a harmonization of the MRI protocols and data postprocessing methods.

Congenital Malformations of the Hand and Forearm in Children: What Radiologists Should Know

Congenital upper limb malformations represent complex pathologies because of their varied clinical presentations, imaging features, and etiologies. They can be divided into (1) failure of formation with transverse, intercalary, and longitudinal (preaxial, postaxial, and mesoaxial) deficiencies, (2) failure of differentiation with synostoses, carpal coalitions, syndactylies, and symphalangism, (3) duplication with ulnar dimelia and polydactylies, and (4) brachydactylies. Congenital Madelungs deformity, clinodactyly, camptodactyly, and Kirners deformity are usually included in these malformations. Despite advances in molecular diagnosis, a good knowledge of clinical and imaging features as well as special consideration of other skeletal or nonskeletal abnormalities are essential to eventually diagnose an embryo fetopathy (maternal valproate treatment, constriction band syndrome), a genetic disorder (trisomy 21 or Down syndrome, Turners syndrome, Holt-Oram syndrome), or a nongenetic syndrome (vertebral, anal, cardiac, tracheal, esophageal, renal, limb association, Polands syndrome). Genetic counseling for a child presenting with a congenital upper limb malformation is of great value, both for the treating team and the parents, and imaging is often required. The latter is still largely supported by conventional radiography, both for diagnosis and functional prognosis, but ultrasound and magnetic resonance imaging will be great tools in the near future to better evaluate these conditions.