Optimization of the Contrast Mixture Ratio for Simultaneous Direct MR and CT Arthrography: an in Vitro Study

OBJECTIVE: This study was designed to determine the optimal mixture ratio of gadolinium and iodinated contrast agent for simultaneous direct MR arthrography and CT arthrography. MATERIALS AND METHODS: An in vitro study was performed utilizing mixtures of gadolinium at six different concentrations (0.625, 1.25, 2.5, 5.0, 10 and 20 mmol/L) and iodinated contrast agent at seven different concentrations (0, 12.5, 25, 37.5, 50, 75 and 92-99.9%). These mixtures were placed in tissue culture plates, and were then imaged with CT and MR (with T1-weighted sequences, proton-density sequences and T2-weighted sequences). CT numbers and signal intensities were measured. Pearson's correlation coefficients were used to assess the correlations between the gadolinium/iodinated contrast agent mixtures and the CT numbers/MR signal intensities. Scatter diagrams were plotted for all gadolinium/iodinated contrast agent combinations and two radiologists in consensus identified the mixtures that yielded the optimal CT numbers and MR signal intensities. RESULTS: The CT numbers showed significant correlation with iodinated contrast concentrations (r = 0.976, p < 0.001), whereas the signal intensities as measured on MR images showed a significant correlation with both gadolinium and iodinated contrast agent concentrations (r = -484 to -0.719, p < 0.001). A review of the CT and MR images, graphs, and scatter diagram of 42 combinations of the contrast agent showed that a concentration of 1.25 mmol/L gadolinium and 25% iodinated contrast agent was the best combination for simultaneous CT and MR imaging. CONCLUSION: A mixture of 1.25 mmol/L gadolinium and 25% iodinated contrast agent was found to be optimal for simultaneous direct MR arthrography and CT arthrography.

Superior Labrum Anterior to Posterior Lesion Type II with Accompanied Findings: Assessment of Shoulder MR Arthrographic Findings

PURPOSE: To describe the pattern of various shoulder abnormalities with an associated superior labrum anterior to posterior (SLAP) lesion type II using magnetic resonance (MR) arthrography, and to assess the clinical significance of the associated abnormalities. MATERIALS AND METHODS: A retrospective review of the MR arthrographic findings of 92 cases of a shoulder with an arthroscopically confirmed SLAP lesion type II was performed. The MR arthrography images were reviewed and analyzed. MR arthrographic analysis noted the presence of a rotator cuff abnormality, acromioclavicular arthritis, adhesive capsulitis, glenohumeral arthritis, a labral abnormality besides the SLAP lesion, and a paralabral cyst. The patients with SLAP lesions were divided into two age groups: those over 40 years of age and those forty years old or younger. Statistical analysis was performed to evaluate the influence of age on the various shoulder abnormalities with associated SLAP lesion. RESULTS: Of the 92 SLAP lesions type II, there were 7 cases (8%) of isolated SLAP lesions without any associated any shoulder abnormality. Eighty-five (92%) SLAP lesions were associated with various shoulder abnormalities including rotator cuff tendinosis (30/92, 33%), partial-thickness tear (36/92, 39%), full-thickness tear (2/92, 2%), acromioclavicular arthritis (46/92, 50%), adhesive capsulitis (7/92, 8%), glenohumeral arthritis (15/92, 16%), labral abnormality (26/92, 28 %) and paralabral cyst (7/92, 8%). The SLAP lesions (60/92, 65%) in patients over forty years of age were accompanied by a significantly high number of rotator cuff abnormalities (p < 0.001), glenohumeral osteoarthritis (p = 0.001), and acromioclavicular osteoarthritis (p < 0.001). In contrast, the SLAP lesions (32/92, 35%) in patients forty years old or younger had a significantly high number of anterior or posterior labral lesions (p < 0.001). CONCLUSION: Isolated SLAP lesions type II without other associated shoulder abnormalities are uncommon, and the age of the patient influences the prevalence of other shoulder abnormalities associated with SLAP lesions. In addition, MR arthrography can help detect shoulder abnormalities accompanying the SLAP lesions.

Adhesive Capsulitis of the Shoulder: MR Arthrography

PURPOSE: Adhesive capsulitis is a clinical syndrome involving pain and decreased joint motion caused by thickening and contraction of the joint capsule. The purpose of this study is to describe the MR arthrographic findings of this syndrome. MATERIALS AND METHODS: Twenty-nine sets of MR arthrographic images were included in the study. Fourteen patients had adhesive capsulitis diagnosed by physical examination and arthrography, and their MR arthrographic findings were compared with those of 15 subjects in the control group. The images were retrospectively reviewed with specific attention to the thickness of the joint capsule, volume of the axillary pouch (length, width, height(depth)), thickness of the coracohumeral ligament, presence of extra-articular contrast extravasation, and contrast filling of the subcoracoid bursa. RESULTS: Mean capsular thickness measured at the inferior portion of the axillary pouch was 4.1 mm in patients with adhesive capsulitis and 1.5 mm in the control group. The mean width of the axillary pouch was 2.5 mm in patients and 9.5 mm in controls. In patients, the capsule was significantly thicker and the axillary pouch significantly narrower than in controls (p<0.05). Capsule thickness greater than 2.5 mm at the inferior portion of the axillary pouch (sensitivity 93%, specificity 80%) and a pouch narrower than 3.5 mm (sensitivity 93%, specificity 100%) were useful criteria for the diagnosis of adhesive capsulitis. In patients with this condition, extra-articular contrast extravasation was noted in six patients (43%) and contrast filling of the subcoracoid bursa in three (21%). CONCLUSION: The MR arthrographic findings of adhesive capsulitis are capsular thickening, a low-volume axillary pouch, extra-articular contrast extravasation, and contrast filling of the subcoracoid bursa. Capsule thickness greater than 2.5 mm at the inferior portion of the axillary pouch and a pouch width of less than 3.5 mm are useful diagnostic imaging characteristics.

Anterior Labral Tear: Diagnostic Value of MR Arthrography of the Shoulder

PURPOSE: To assess the accuracy of magnetic resonance(MR) arthrography in the diagnosis of anterior labral tear of the shoulder. MATERIALS AND METHODS: Between Semptember 1996 and February 2000, MR arthrography of the shoulder was performed in 281 patients with a history of shoulder pain or instability. Among this total, only 157 shoulders in 154 patients who underwent arthroscopy or open surgery 0 to 230 (average, 20.9) days after MR arthrography were included in this study; the subjects comprised of 150 males and 4 females with an average age of 23.3 years. MR arthrographs of these 154 patients were analyzed for the presence of anterior labral tears, and the findings were correlated with the arthroscopic and surgical findings. Anterior labral tear was classified as A to D according to its location, as determined by arthroscopy and surgery. (A=4 to 6 o 'clock direction, anteroinferior; B=2 to 4 o 'clock direction, central; C=12 to 2 o 'clock direction, anterosuperior; D= SLAP lesions). The retrospective analysis of MR arthrographs showing false-positive and negative findings was also undertaken. RESULTS: In the diagnosis of anterior labral tear, MR arthrography showed a sensitivity of 94%, a specificity of 90% and an accuracy of 91%. Anterior labral tears were confirmed by arthroscopy or surgery in 62 of the 157 shoulders (39%). Among 62 lesions, two (3%) were observed in area A, 32(52%) in area A+B, nine (15%) in area A+B+C, one(2%) in area A+B+D, 13(21%) in area A+B+C+D, two (3%) in area B+C, one(2%) in area B+D, and two(3%) in area C. Among ten false-positive cases, seven were focal lesions (two, three and two lesions in area A, B and C, respectively), and in the remaining three cases, located in area A+B, MR arthrography revealed thickening and deformation. All four false negatives were focal lesions (two in area A and two in area C). CONCLUSION: Other than in focal lesions, in which accuracy was relatively low, MR arthrography showed high sensitivity, specificity and accuracy in the diagnosis of anterior labral tear of the shoulder.

Efficacy of MR Arthrography in the Diagnosis of the Acetabular Labral Tear

PURPOSE: To determine the accuracy of magnetic resonance (MR) arthrography in the detection and staging of lesions of the acetabular labrum. MATERIALS AND METHODS: Fifteen hips of 14 patients with chronic hip pain and clinical suspicion of labral lesions were examined with direct or indirect MR arthrography and underwent subsequent arthroscopic evaluation. The study population consisted of six women and eight men aged between 40 and 59 years. Nine arthrograms were obtained intra-articular administration of gadolinium solution, and six involved articular motion exercise after intravenous administration of gadolinium solution. In 14 cases a phased-array pelvic coil was used, and a shoulder coil in one. Fat-suppressed T1-weighted images were obtained in the coronal, oblique coronal and oblique axial planes, and T1-and T2-weighted images were obtained in the axial plane. Labral lesions were graded according to the Czerny classification and evaluated on the basis of presence or absence of a tear and location (anteroinferior, anterosuperior, superior, posterosuperior, posteroinferior). The findings were then correlated with the arthroscopic findings. RESULTS: After direct and indirect MR arthography, the findings-based on the Czerny classification -were as follows : stage IA:3; IB:1; IIA:8; IIB:1; IIIA:4; IIIB:0. MR arthrography also showed that seven cases were located in the anterosuperior portion of the labrum, seven in the superior portion, and three in the posteroinferior portion. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of MR arthrography for diagnosis of the labral tear was 92%, 75%, 92%, 75 %, and 88 %, respectively. CONCLUSION: In this preliminary study, MR arthrography appears to be a promising imaging modality for accurate diagnosis and useful for screening patients with chronic hip pain.

Subchondral Cysts of the Humeral Head: MR Imaging Findings

PURPOSE: To evaluate the findings of subchondral cyst of the humeral head, as seen on shoulder MRarthrography MATERIALS AND METHODS: Sixty-three patients( M:F=62:1 ; mean age 23 years) who underwent shoulder MRarthrography between September 1996 and May 1998 were retrospectively reviewed. No patient had a history of eithershoulder dislocation or certain diseases known to be commonl accompanied by subchondral cysts. All MR images wereobtained using a 1.5 Tesla unit after intraarticular injection of 20ml of diluted contrast material. T1 andT2-weighted axial, oblique coronal, and oblique sagittal images were analysed for the presence, location, number,shape, size, and connection to the joint cavity of subchondral cysts. RESULTS: We identified 58 subchondral cystsin 43(71.7%) of 63 cases. All were located in the posterolateral portion of the humeral head, and on the physealline. Twenty-eight patients(65.1%) had one cyst, and 15(34.9%) had two. Thirty-four cysts(58.6%) were round orovoid in shape and, 2-8mm in diameter(average, 3.9mm) ; 24(41.4%) were lobulated and 3-10mm in diameter(average5.3mm). Fifty-three cysts(91.4%) were connected to the joint cavity. CONCLUSIONS: In symptomatic patients, the incidence of subchondral cyst of the humeral head was 71.7%. All were located in the posterolateral portion, andon the physeal line. Most subchondral cysts were connected with the joint cavity.

A Study to Assess by Means of MR Arthrography the Causal Relationship between Anterior Capsular Attachment Typeand Anterior Instability of the Glenohumeral Joint

PURPOSE: To evaluate by means of MR arthrography the causal relationship between anterior capsularattach-ment type and anterior instability of the glenohumeral joint. MATERIALS AND METHODS: Sixty-five patients (M:F=64:1; mean age, 23 years), who had undergone shoulder MR arthrography were retrospectively reviewed. There wasno history of traumatic dislocation, and medical records relating to anterior instability were available. Physicalexamination revealed anterior instability in 25 patients(Group A), while in 40 (Group B), this was eithersuspicious or absent. With the aid of general anesthe-sia, 32 patients who had undergone surgery were physicallyexamined. Anterior instability was evident in 16 patients(Group C), and suspicious or absent in the remaining 16(Group D). All images were obtained after in-traarticular injection of Gd-DTPA. Fat-suppressed T1 axial imagingwas used to evaluate anterior capsular at-tachment type at mid and distal three-fourths levels of the glenoidfossa. The causal relationship between ante-rior capsular attachment types and anterior instability was analyzedusing the x2 test RESULTS: In group A, type I was most common at distal three-fourths level, and types I and IIwere equal and more common than type III at mid level. In group B, type I anterior capsular attachment type wasmost com-mon at both mid and distal three-fourths level. In these groups, no statistical significance was notedbetween anterior capsular attachment type and anterior instability (p value 0.611: 0.567). In group C, types I andII were equal and more common than type III at both mid and distal three-fourths level, while in group D, type IIwas most common at mid level, and type I was most common at distal three-fourths level. In these groups, nostatistical significance was noted between anterior capsular attachment type and anterior instability (p val-ue,0.772). CONCLUSION: There was no statistically significant difference between anterior capsular attachment typeand anterior instability of the shoulder joint.