Joseph S. Yu

Double echo steady state magnetic resonance imaging of knee articular cartilage at 3 Tesla: a pilot study for the Osteoarthritis Initiative.

Background: Quantitative magnetic resonance imaging (qMRI) may provide valuable measures of cartilage morphology in osteoarthritis (OA) but has been confined to sequences with relatively long acquisition times at 1.5 Tesla (T). Objective: To test the accuracy and precision of knee cartilage qMRI with a fast double echo, steady state (DESS) sequence with water excitation (we) at 3 T. Methods: As a pilot study for the Osteoarthritis Initiative, test-retest MR images were acquired in the knees of 19 participants with no OA to moderate degrees of clinical OA. Two double oblique coronal fast low angle shot (FLASHwe) sequences (1.5 mm slice thickness) were acquired at 3 T, and two sagittal DESSwe sequences (0.7 mm slice thickness). Double oblique coronal multiplanar reformats (MPR) were performed (1.5 mm slice thickness) from the sagittal DESSwe. Knee joint cartilage plates were quantified unpaired in random order with blinding to subject identification. Results: In the femorotibial joint, precision errors (root mean square coefficient of variation in % for unpaired analysis) for cartilage volume and thickness were 3.0–6.4% with coronal FLASHwe, 2.4–6.2% with coronal MPR DESSwe, and 2.3–8.2% with sagittal DESSwe. Correlation coefficients between DESSwe and FLASHwe ranged from r = 0.88 to 1.0. In the femoropatellar joint, precision errors (sagittal DESSwe) were 3.4–8.5%. Conclusions: DESSwe permits accurate and precise analysis of cartilage morphology in the femorotibial joint at 3 T. Further studies are needed to examine the accuracy of DESSwe in the femoropatellar joint and its ability to characterise sensitivity to longitudinal changes in cartilage morphology.

Impact of coil design on the contrast‐to‐noise ratio, precision, and consistency of quantitative cartilage morphometry at 3 Tesla: A pilot study for the osteoarthritis initiative

Phased‐array (PA) coils generally provide higher signal‐to‐noise ratios (SNRs) than quadrature knee coils. In this pilot study for the Osteoarthritis Initiative (OAI) we compared these two types of coils in terms of contrast‐to‐noise ratio (CNR), precision, and consistency of quantitative femorotibial cartilage measurements. Test‐retest measurements were acquired using coronal fast low‐angle shot with water excitation (FLASHwe) and coronal multiplanar reconstruction (MPR) of sagittal double‐echo steady state with water excitation (DESSwe) at 3T. The precision errors for cartilage volume and thickness were ≤2.6% for the quadrature coil and ≤2.3% for the PA coil with FLASHwe, and ≤2.3%/≤2.5% with DESSwe. The precision for aggregate medial and lateral cartilage measures was significantly higher than that for single plates, independently of coil and sequence. The PA coil measurements did not always fully agree with the quadrature coil measurements, and some differences were significant. The higher CNR of the PA coil did not translate directly into improved precision of cartilage measurement; however, summing up cartilage plates within the medial and lateral compartment reduced precision errors. Magn Reson Med 57:448–454, 2007.

MR imaging of urgent inflammatory and infectious conditions affecting the soft tissues of the musculoskeletal system

Soft tissue infections and inflammatory conditions of the musculoskeletal system are a group of disorders commonly seen by emergency room physicians and radiologists. Many of these entities can either be limb- or life-threatening. Magnetic resonance imaging is currently the best imaging modality to evaluate these conditions. In this review, the characteristic imaging findings of cellulitis, abscess formation, necrotizing fasciitis, pyomyositis, diabetic ischemic infarction, acute and exertional compartment syndromes, and rhabdomyolysis will be emphasized as well as imaging factors that can help to differentiate these disorders.

Pathologic and post-operative conditions of the plantar fascia: review of MR imaging appearances

Abstract Magnetic resonance (MR) imaging has emerged as an important noninvasive diagnostic imaging technique for assessment of foot pathology. This modality, owing to its multiplanar imaging capability and inherent superiority in contrast, has been shown to be more accurate and sensitive for detection of plantar fascia pathology than any other imaging method. One of the most important and recognizable causes of heel pain is plantar fasciitis. With the exception of plantar fasciitis, there has been little emphasis on imaging other conditions that affect this important structure. The objective of this review is to demonstrate, from a perspective of MR imaging, the many different pathologic conditions that affect the plantar fascia. Included in this review will be a discussion of normal anatomy as well as entities such as acute plantar fasciitis, chronic plantar fasciitis, traumatic rupture, normal post-surgical changes, pathologic post-fasciotomy conditions, infection, and fibromatosis.

Suspected scaphoid fractures in skeletally immature patients: application of MRI.

PURPOSE The purpose of our study was to evaluate the MR findings in the wrists of pediatric patients who have sustained acute wrist injuries and to determine if this imaging method yields more information than combined serial radiographs and physical examinations. METHOD Eighteen skeletally immature patients (11 boys and 7 girls, age range 8-15 years) who had presented to the emergency room within 2 days following acute wrist trauma underwent serial clinical, radiographic, and MR examinations if there was a suspicion of a scaphoid fracture. RESULTS Ten patients had a scaphoid abnormality on MR images. Six had fractures and four had regional bone marrow edema. Initially, all but two fractures were radiographically occult, although the other fractures eventually became evident on later studies. Those with marrow edema did not progress to fractures. Obliteration of the scaphoid fat stripe occurred in five patients with a scaphoid fracture and in six patients who did not have a fracture. Dorsal soft tissue swelling occurred in eight patients, five of whom had scaphoid fractures. Seven patients had evidence of extensor tenosynovitis on MRI. CONCLUSION A normal initial MR image had a negative predictive value of 100%. Persistent snuffbox pain may represent injury to the scaphoid, extensor tendons, or dorsal soft tissues. An outcome study evaluating the benefits of early application of MR in the pediatric population is warranted.

Mri of Elastofibroma Dorsi

Objective To determine if the MR features of elastofibroma are sufficient for diagnosis of this neoplasm. Materials and Methods The MR studies of two patients with pathologically proven bilateral elastofibromas were reviewed retrospectively. Results In each patient, bilateral semilunar soft-tissue masses demonstrating signal intensities isointense to that of muscle were identified in the periscapular regions deep to the posterolateral musculature of the chest. Focal linear areas of fat were present. The biopsy specimens of both patients demonstrated a positive reaction to the elastin stains. Conclusion A periscapular soft-tissue neoplasm demonstrating a pattern of linear alternating regions of high and intermediate signal intensity on T1− and T2-weighted spin-echo MRI should be sufficient to allow the diagnosis of elastofibroma.

Ossification of the Achilles tendon: imaging abnormalities in 12 patients

Ossification of the Achilles tendon is a rare clinical entity that is characterized by the presence of an ossific mass contained within the fibrocartilaginous substance of the tendon. Because the radiographic features of this condition have not been documented entirely and the magnetic resonance (MR) imaging findings have not been determined, a review of 16 affected tendons in 12 patients was performed in an attempt to characterize the imaging abnormalities associated with this process. MR imaging was performed in three Achilles tendons which demonstrated thickening of the tendons at the level of the ossifications and a lack of intratendinous signal abnormalities compatible with acute tendinitis. Signal intensity similar to that of bone marrow was present in the ossifications.

Gorham syndrome of the thorax and cervical spine: CT and MRI findings

Abstract Gorham syndrome is a rare disorder that is characterized by local osseous invasion and surrounding soft tissues by an angiomatous mass, eventually causing lysis of the affected bone. To date, only four cases have reported the MR imaging appearance of this disease and the findings have been variable. We present a case involving the cervical and thoracic spine and part of the osseous hemithorax with attention to the MR findings.

Can anatomic alignment measured from a knee radiograph substitute for mechanical alignment from full limb films

OBJECTIVES To examine whether categories of anatomic alignment (varus, neutral, valgus) measured from knee X-rays agree with similar categories of mechanical alignment from the full limb film and whether varus anatomic malalignment predicts medial joint space loss on knee X-rays as well as varus mechanical alignment. METHODS We used data from the Osteoarthritis Initiative (OAI) (full limb and flexed knee X-rays) to examine agreement of anatomic and mechanical alignment and data from Boston Osteoarthritis of the Knee Study (BOKS) to evaluate the association of full limb mechanical alignment vs knee X-ray anatomic alignment with joint space loss. A 4 degree offset was used to correct for the more valgus angulation of the anatomic alignment. RESULTS Of 143 subjects whose knee X-rays and full limb films were publicly released from the OAI, the agreement of varus, neutral and valgus alignment was only moderate (kappa=0.43, P<0.001). In BOKS, varus mechanical and anatomic alignments measured from full limb and knee X-rays respectively both predicted a high risk of medial joint space loss vs neutral alignment--for mechanical alignment, odds ratio (OR)=4.82 [95% confidence interval (CI) 1.93, 12.00] and for anatomic alignment OR=4.25 (95% CI 2.08, 8.72). CONCLUSIONS While agreement of alignment from knee X-ray to full limb film was only moderate, varus malalignment measured from a flexed knee predicted the likelihood of progression well. Flexed knee alignment may be more relevant to knee osteoarthritis (OA) risk than that of a fully extended knee, but a measurement of alignment from a short limb is an imperfect surrogate for full limb alignment.

Madelung Deformity in Skeletally Immature Patients: Morphologic Assessment Using Radiography, Ct, and Mri

PURPOSE The purpose of this study was to define the pathoanatomy of the distal radius and surrounding soft tissues, identify the factors that may contribute to diminished forearm rotation, and relate these findings to alterations in wrist motion in skeletally immature patients with the Madelung deformity. METHOD Four skeletally immature female patients with bilateral Madelung deformities (eight wrists) underwent evaluation of each wrist with radiography, CT, and MRI to assess the morphology of the deformity. Two patients (four wrists) had isolated idiopathic Madelung deformities, and two patients (four wrists) had Madelung deformities secondary to dyschondrosteosis. RESULTS Radiographically, all wrists demonstrated dorsal bowing of the radius, marked ulnar tilting of the radius and radial tilting of the ulna, volar tilting of the distal articular surface of the radius, and triangulation of the epiphysis. On CT, patients with the idiopathic deformity demonstrated dorsal ulnar subluxation and relative supination of the carpus with respect to the distal radius. Patients with dyschondrosteosis demonstrated no ulnar subluxation and relative pronation of the carpus. All wrists demonstrated a fixed pronated deformity of the distal radius. On MRI, a physeal bar that bridged the distal metaphysis of the radius to the epiphysis was identified in all eight wrists, located on the volar aspect of the radius at the lunate facet. An anomalous volar ligament, a volar radiotriquetral ligament, and the short radiolunate ligament were hypertrophied in seven wrists. CONCLUSION Based on its location, it is likely that a physeal bar impedes the normal development of the distal radius ulnarly. Hypertrophy of the short radiolunate ligament may be an important contributing factor to carpal pyramidalization owing to tethering on the volar pole of the lunate. Diminished forearm rotation is likely related to carpal malalignment, a fixed pronated deformity of the distal radius, and dorsal bowing of the radius.