Bone Tissue in Magnetic Resonance Imaging: Contribution of New Zero Echo Time Sequences.

The introduction of new ultrashort and zero echo time (ZTE) sequences is revolutionizing magnetic resonance imaging (MRI) and optimizing patient management. These sequences acquire signals in tissues with very short T2: mineralized bone, cortical bone, and calcium deposits. They can be added to a classic MRI protocol. ZTE MRI provides computed tomography-like contrast for bone.

Femoral Torsion: Impact of Femur Position on CT and Stereoradiography Measurements.

OBJECTIVE: The purpose of this study is to evaluate stereoradiographic measurements of femoral torsion with different femoral positions, in comparison with CT measurements, with use of the current standard axial-slice technique. We hypothesize that CT measurements vary with femoral spatial positioning because of the resulting projection onto the CT plane, whereas stereoradiographic measurements, which are derived from a 3D reconstruction of the femur, remain constant. MATERIALS AND METHODS: Both in vitro and in vivo studies were conducted. CT and stereoradiographic examinations were performed using 30 dry femurs in the following six femoral positions: neutral position (with the femoral mechanical axis aligned with the longitudinal axis of the CT scanner or stereoradiography system), 10° of abduction, 10° of adduction, 5° of flexion, 10° of flexion, and 5° of extension. The impact of femoral position on torsion measurement was assessed using paired t tests. In addition, 18 patients (mean [± SD] age, 42.3 ± 19.9 years) who underwent both CT and stereoradiography examinations were retrospectively assessed. The correlation between femoral positioning and torsion measurement was determined using the Pearson correlation coefficient. RESULTS: Flexion and extension statistically significantly affected CT measurement of femoral torsion (p < 0.01) but not stereoradiography measurement (p > 0.21). A strong correlation existed between hip flexion and the difference between femoral torsion measured by CT and stereoradiography (r = -0.80). CONCLUSION: The accuracy of femoral torsion determined by axial CT depends on the position of the femur. Hip flexion significantly reduced the femoral torsion angle measured by CT. Conversely, the accuracy of stereoradiography was independent of femur positioning. Thus, stereoradiography is preferable to CT for accurate measurement of femoral torsion, while it also substantially reduces the radiation dose.

Fat Suppression with Dixon Techniques in Musculoskeletal Magnetic Resonance Imaging: A Pictorial Review.

Dixon techniques are part of the methods used to suppress the signal of fat in MRI. They present many advantages compared with other fat suppression techniques including (1) the robustness of fat signal suppression, (2) the possibility to combine these techniques with all types of sequences (gradient echo, spin echo) and different weightings (T1-, T2-, proton density-, intermediate-weighted sequences), and (3) the availability of images both with and without fat suppression from one single acquisition. These advantages have opened many applications in musculoskeletal imaging. We first review the technical aspects of Dixon techniques including their advantages and disadvantages. We then illustrate their applications for the imaging of different body parts, as well as for tumors, neuromuscular disorders, and the imaging of metallic hardware.

[Is medical imaging iatrogenic?]. / L'imagerie médicale diagnostique est-elle latrogène ?

Imaging is an indispensable element of modern medicine but is not without risk. Low-dose irradiation due to spinal, abdominal, pelvic or cardiac radiography, and the increasing use of CT carries an additional, albeit moderate risk of cancer. Iodinated and gadolinium-containing contrast media, besides their direct toxicity, can trigger hypersensitivity and allergic-like reactions. Spinal and articular diagnostic injections can also lead to complications. This article reviews the direct iatrogenicity of diagnostic imaging and current efforts to limit it through the use of new radiological systems, lower-dose CT non ionic contrast media, and alternative imaging techniques. The authors also examine the less known but more frequent problem of indirect iatrogenesis, which is highly dependent on the quality of the imaging personnel and technique. Finally, we propose some legislative solutions to this problem.

Standardized way for imaging of the sagittal spinal balance.

Nowadays, conventional or digitalized teleradiography remains the most commonly used tool for the study of the sagittal balance, sometimes with secondary digitalization. The irradiation given by this technique is important and the photographic results are often poor. Some radiographic tables allow the realization of digitalized spinal radiographs by simultaneous translation of X-ray tube and receptor. EOS system is a new, very low dose system which gives good quality images, permits a simultaneous acquisition of upright frontal and sagittal views, is able to cover in the same time the spine and the lower limbs and study the axial plane on 3D envelope reconstructions. In the future, this low dose system should take a great place in the study of the pelvispinal balance. On the lateral view, several pelvic (incidence, pelvic tilt, sacral slope) and spinal (lumbar lordosis, thoracic kyphosis, Th9 sagittal offset, C7 plumb line) parameters are drawn to define the pelvispinal balance. All are interdependent. Pelvic incidence is an individual anatomic characteristic that corresponds to the "thickness" of the pelvis and governs the spinal balance. Pelvis and spine, in a harmonious whole, can be compared to an accordion, more or less compressed or stretched.

[Recent advances in imaging of hip and knee prostheses]. / L'imagerie actuelle des prothèses de hanche et de genou.

More than 222 000 hip and knee prostheses are implanted each year in France and this number is growing. Simple radiography is generally used to examine these prostheses in situ but this method has several limitations, including superimposition, the inability to visualize some parts of the prosthesis and to study them in the axial plane, and poor visualization of intra- and peri-articular soft tissues. This article describes the advantages offered by computed tomography and ultrasonography in this setting

[Foot imaging]. / Imagerie du pied.

Foot and ankle problems are frequent, daily pathologies. Nowadays, imaging is able to put in evidence the most part of these affections, in a simple, non traumatic way. A good clinical examination is of highest importance to guide the imaging technique. Well done simple X-rays in a standing position is the first mandatory step. Ultrasonography has revolutionized the study of the smooth parts of the foot: tendons, sprains, pathologies of plantar aponeurosis, hind-foot problems....It is therefore the first exam to ask for. Ultrasonography is enough to resolve a very important part of the superficial soft tissues pathologies. When this technique fails, whatever the reason, RMI is the best way to study soft tissues and bone marrow (stress fractures, small intraosseous lesions, osteonecrosis...). CTscan remains the best tool to study the hard part of the skeleton. Neither CTscan nor RMI can directly put in evidence the joint's cartilage with a high degree of precision. So, an arthrography remains mandatory to have a good study of the cartilage of the ankle.

[Evolution of musculoskeletal ultrasonography]. / L'évolution de l'échographie de l'appareil moteur.

Sonography is a safe, inexpensive and readily accessible technique which has acquired a major place in musculoskeletal imaging over the past two decades. Thanks to recent technical innovations such as high-definition multifrequency probes, compound effect, use of harmonic frequencies, power Doppler, and extended field of view, today's sonographic images are extremely precise. At the same time, based on magnetic resonance imaging (MRI) and computed tomography (CT) acquisitions, the sonographic anatomy has become broader and more detailed, and the sonographic semiology is more precise and reliable. In this article the authors evaluate current uses of diagnostic and interventional sonography in musculoskeletal disorders.

Description of the potential of an arthrometer for standard and reduced radiographs suitable to measurement of angles and segments of hip, knee, foot and joint space widths.

BACKGROUND: Primary osteoarthritis is usually selected in either epidemiological or therapeutic studies. This implies exclusions. Among cases of secondary osteoarthritis considered for either stratification or exclusion--or for prognosis and treatment in daily practice--are those due to architectural defects. Parameters of the latter should be measured to ascertain diagnosis. At present, measurements have to be performed either on digitized reduced films or standard radiographs. OBJECTIVE: To finalize an instrument capable of measuring the main angles and segments characteristic of the main dysmorphisms of the hip, knee and foot on different sizes of films. METHODS: An arthrometer drawn on transparent material to be placed on radiographs was designed, involving several appropriate protractors and millimetric scales; it was tested on 60 hip, 35 knee and 17 foot radiographs with various architectural defects. Angles and segments most often used according to literature were measured. Reduction rates of films were various, reflecting the range of radiograph sizes currently used in everyday practice. RESULTS: Measurements were easily performed on radiographs from standard (100%) up to 50% of reduction rate. So the arthrometer allows the recognition, especially in moderate, not obvious forms, of the following developmental or acquired dysmorphisms: hip congenital dysplasia and subluxation, including coxa valga and neck excess of anteversion; acetabular protrusion and coxa vara; tilt deformity; knee: patellar height abnormalities, patellar maltracking, trochlear depth insufficiency; foot: pes cavus, flatfoot. Angle and segment ratios do not change in reduced film, whereas segments (absolute lengths) obviously should be converted according to the reduction rate for retrieving the classical values established for decades. CONCLUSION: The arthrometer allows us to measure the relevant parameters of various dysmorphisms without drawing lines over the films themselves. It is suitable to reduced as well to standard radiographs. However, only the instrument and its ability to be used in various films sizes are here presented. Study of reproducibility of measurements--especially concerning the joint space width--remain to be performed.

Pain immediately upon sitting down and relieved by standing up is often associated with radiologic lumbar instability or marked anterior loss of disc space.

STUDY DESIGN: Comparison of functional radiographs in consecutive patients with low back pain with or without pain on sitting down and relieved by standing up. OBJECTIVES: To detect radiologic signs possibly associated with a clinical symptom. SUMMARY OF BACKGROUND DATA: No link has been established between increased vertebral mobility and a specific pain pattern or a clinical symptom. METHODS: Forty-two patients seen consecutively with low back pain occurring immediately on sitting down and relieved on standing up were compared with 32 controls whose low back pain did not show this pattern. Dynamic radiographs were taken in extension, erect, flexion, and sitting in the painful position. The segments thought to be responsible for the pain were identified by comparing clinical, radiographic, and magnetic resonance data. Endplate angles, rotation, and translation were measured. The radiographs were read twice each by two independent observers. RESULTS: Eighty-six percent (95% confidence interval, 72-99%) of the patients with the symptom were female. The segments identified as the source of pain were as follows: L4-L5 in 20 cases and L1-L2 to L3-L4 in 22 cases. Mean rotation of these segments was 13.9 +/- 4.5 degrees in the patient group versus 7.5 +/- 4.3 degrees in the control group (P < 0.001). In 14% of the patients (vs. 3% of controls), it exceeded 20 degrees (P = 0.13). Anterior or posterior translation >10% was seen in 31% of the patients (vs. 0% of controls; P < 0.001). In flexion, the endplate angle was -5.2 +/- 3.6 degrees (patients) versus 1.2 +/- 5.7 degrees (controls) (P < 0.01) and <-5 degrees in 55% of patients versus 12.5% of controls (P < 0.001). This value of <-5 degrees was associated with marked anterior loss of disc space. CONCLUSION: Low back pain occurring immediately on sitting down and relieved on standing up was statistically associated with instability (specificity 100%, sensitivity 31%) or marked anterior loss of disc space in flexion (specificity 87%, sensitivity 55%).