Dose reduction for fluoroscopically guided injections: phantom simulation and patient procedures.

OBJECTIVE: To demonstrate fluoroscopy dose reduction through both simulated injections on a phantom and patient injections. MATERIALS AND METHODS: Our study was IRB-approved and HIPAA-compliant. Simulation on a phantom was used to estimate effective dose, entrance dose, and organ doses for hip joint injections without and with dose minimization technique (DMT). Additionally, 1,094 joint, bursae, and tendon sheath injections performed by three operators in the same fluoroscopy suite were evaluated both before and after application of DMT. Fluoroscopy time (FT), dose, and dose area product (DAP) of injections were compared using unpaired t-tests with P > 0.05 considered statistically significant. RESULTS: For the phantom simulation comparing injections without DMT and with DMT, the total DAP was 191.7 vs 18.7 µGy·m2, and the entrance dose was 10.2 vs 3.6 mGy, respectively. For both men and women, DMT reduces effective dose and organ doses. For all injections, the FT (0.7 to 0.2 min), dose (5.6 to 1.9 mGy), and DAP (56.9 to 19.1 µGy·m2) for all three operators decreased with DMT and remained statistically significant when stratified by the two most common injections, glenohumeral and hip joint injections (P < 0.05). CONCLUSIONS: FT, effective dose, entrance dose, and DAP can be reduced with the use of simple easy-to-learn techniques, which will benefit both the patient and the radiologist.

Re-examining the association of os acromiale with supraspinatus and infraspinatus tears.

PURPOSE: To re-evaluate the relationship between os acromiale and rotator cuff tears. METHODS: We retrospectively analyzed 84 magnetic resonance imaging studies of the shoulder. Forty-two subjects with os acromiale (n = 42; 32 men and ten women, age 25-81 years, mean 47.6 years) were compared with age- and gender-matched subjects with no evidence of os acromiale (controls). Arthroscopy data were available in 19 os acromiale and 12 control subjects. Statistical analyses were performed to determine differences between groups regarding rotator cuff tears affecting the supraspinatus and infraspinatus tendons detected by magnetic resonance imaging and arthroscopy. Analysis of os acromiale type, ossicle synchondrosis edema, acromioclavicular joint degenerative changes and step-off deformity at the synchondrosis were tabulated. RESULTS: No statistically significant difference between the os acromiale and control groups was noted, either on magnetic resonance imaging or arthroscopy, with regard to tears of the supraspinatus (P = 1.000 and 0.981, respectively) and infraspinatus (P = 1.000 and 0.667, respectively) tendons. There was a statistically significant increased number of supraspinatus (P = 0.007) and infraspinatus (P = 0.03) tears in a comparison of subjects with os acromiale and step-off deformity (10/42) vs os acromiale without step-off deformity (32/42). CONCLUSION: The presence of os acromiale may not significantly predispose to supraspinatus and infraspinatus tendon tears. However, subjects with step-off deformity of an os acromiale are at greater risk of rotator cuff tears than are similar subjects without such deformity.

Magnetic resonance imaging in the quantitative assessment of gouty tophi.

Measurements of tophus size can be important in monitoring the course of gout therapy, as tophus resolution is proposed as one measure of success of treatment. This multicentre study assessed the intra- and interreader reproducibility of quantitative tophus volume measurements from magnetic resonance images (MRI) in subjects with palpable gouty tophi. Subjects first underwent radiographic imaging of a selected tophus followed by MRI before and at

Effect of chondrocalcinosis on the MR imaging of knee menisci.

OBJECTIVE: Our goal was to determine the influence of chondrocalcinosis on MR imaging in the detection of meniscal tears. MATERIALS AND METHODS: A retrospective review was performed of knee MR imaging and arthroscopy records from two university hospitals between 1996 and 1998. Seventy individuals had radiographic evidence of chondrocalcinosis and underwent knee MR imaging. Thirty-seven of these individuals had undergone arthroscopy for further evaluation of their symptoms. MR imaging sensitivity and specificity in the detection of medial and lateral meniscal tears were calculated in these 37 patients who had radiographic evidence of chondrocalcinosis and in a control group of 34 patients who underwent MR imaging and arthroscopy but did not have knee chondrocalcinosis. RESULTS: In the chondrocalcinosis group, MR imaging sensitivity, specificity, and accuracy for meniscal tear were 78%, 71%, and 78%, respectively, for the lateral meniscus, and 89%, 72%, and 81% for the medial meniscus. The control group showed sensitivity, specificity, and accuracy of 93%, 100%, and 97%, respectively, for the lateral meniscus and 100% in all cases for the medial meniscus. The MR imaging detection of meniscal tears in both the lateral and medial compartments combined is significantly poorer in the presence of chondrocalcinosis (p < 0.005). CONCLUSION: MR imaging sensitivity and specificity for detection of meniscal tear is decreased in the presence of meniscal chondrocalcinosis. Chondrocalcinosis appeared as a high-signal-intensity region on T1-weighted, intermediate-weighted, and inversion recovery sequences. The high signal of chondrocalcinosis on inversion recovery sequence is an interesting observation that to our knowledge has not been previously reported. Radiographic correlation with the MR imaging examination can help prevent overdiagnosing meniscal tears.

MR imaging of myotendinous strain.

Myotendinous strain predominantly exhibits pathognomonic MR features. Whenever a patient's musculoskeletal symptoms lack temporal correlation with exercise, MR imaging may be valuable in distinguishing strain injury from other disorders of the myotendinous unit. Compared with myotendinous strain, myositis ossificans has variable and nonspecific MR appearances that may simulate neoplasm and require biopsy for diagnosis.

Magnetic resonance imaging features of allografts.

OBJECTIVE: To investigate the magnetic resonance imaging (MRI) features of allografts at various time intervals after surgery in patients with osteoarticular allografts. DESIGN AND PATIENTS: Sixteen patients who were treated with osteoarticular allografts and who were followed over time with MRI studies as part of their long-term follow-up were retrospectively selected for this study. T1-weighted images were obtained both before and after gadolinium administration along with T2-weighted images. All images were reviewed by an experienced musculoskeletal radiologist, with two other experienced radiologists used for consultation. Imaging studies were organized into three groups for ease of discussion: early postoperative period (2 days to 2 months), intermediate postoperative period (3 months to 2 years), and late postoperative period (greater than 2 years). RESULTS: In the early postoperative period, no gadolinium enhancement of the allograft was visible in any of the MR images. A linear, thin layer of periosteal and endosteal tissue enhancement along the margin of the allograft was visible in images obtained at 3-4 months. This enhancement appeared gradually to increase in images from later periods, and appears to have stabilized in the images obtained approximately 2-3 years after allograft placement. The endosteal enhancement diminished after several years, with examinations conducted between 6 and 8 years following surgery showing minimal endosteal enhancement. However, focal enhancement was noted adjacent to areas of pressure erosion or degenerative cysts. All the cases showed inhomogeneity in the marrow signal (scattered low signal foci on T1 with corresponding bright signal on T2), and a diffuse, inhomogeneous marrow enhancement later on. CONCLUSION: We have characterized the basic MRI features of osteoarticular allografts in 16 patients who underwent imaging studies at various time points as part of routine follow-up. We believe that the endosteal and periosteal enhancement observed on MRI during the first few months to 2 years following surgery represents vascular ingrowth and early skeletal repair. The zone of periosteal enhancement could also include the new bone laid on the surface of the allograft through which the soft tissues bind to the cortex. The exact reason for the inhomogeneity in the marrow signal, and the diffuse, inhomogeneous marrow enhancement is not clear. This may represent saponified and/or necrotic marrow fat interspersed with the fibrovascular tissue. The features noted here should provide radiologists with useful information regarding imaging characteristics they can expect to see in other allograft replacement patients.

A general computing method for spatial cartilage thickness from co-planar MRI.

Techniques for assessing cartilage thickness from planar magnetic resonance (MR) images have traditionally accounted for surface curvature only in the image plane. Many joints, such as the knee and hip, have significant curvature normal (transverse) to the image plane which results in overestimation of in-plane cartilage thickness measurements. We developed a generalized computing method for calculating spatial thickness distribution of joint cartilage from co-planar MR images which accounts for transverse surface curvature. We applied the technique using fat-suppressed SPGR (spoiled gradient recalled in the steady-state) MR images of two human acetabulae and compared the results with a previously validated spherical model of the acetabulum which also accounts for transverse curvature of the cartilage surface. The agreement between the generalized model and validated spherical model was very good for both acetabular specimens (correlation: r = 0.998, p < 0.001; differences: p > 0.63). We conclude that the generalized method is acceptable for computing spatial cartilage thickness distribution of joints with complex geometries, such as the knee.

Knee arthrography. Evolution and current status.

This article explores arthrography of the knee beginning with a brief historical perspective of conventional knee arthrography and culminating in direct and indirect MR arthrography of the knee. This article discusses the advantages of MR arthrography in the radiologic assessment of the postoperative meniscus, abnormalities of articular cartilage, and synovial-based processes.

Cartilage and subchondral bone thickness distribution with MR imaging.

RATIONALE AND OBJECTIVES: The authors mapped articular cartilage (AC) and subchondral bone (SB) thicknesses in human acetabula in vitro by using magnetic resonance (MR) imaging and validated AC measurements by using light microscopy. MATERIALS AND METHODS: Left and right acetabula from a deceased patient who had undergone left hemiarthroplasty were imaged with fat-suppressed spoiled gradient-recalled acquisition in the steady state (repetition time = 55 msec, echo time = 15 msec, flip angle = 50 degrees, matrix = 256 x 256, field of view = 8 cm). AC and SB thickness maps were generated from image data by using analytic geometry, which enabled correction for thickness overestimation due to oblique sectioning. Cartilage bone plugs were extracted from the acetabula, and light microscopy was used to validate the thickness measurements obtained with MR imaging. RESULTS: Standard errors between thickness measurements obtained with MR imaging and light microscopy were 0.37 and 0.33 mm for the left and right AC, respectively, which is consistent with the voxel resolution of the MR imaging sequence (0.31 x 0.31 x 0.8 mm). SB thickness of the cartilage plugs could not be reliably measured with light microscopy and, therefore, could not be validated. Contour maps showed that SB thickness gradients were rapid and focal compared with the rather smooth gradients in AC thickness; however, thicker AC was accompanied by thicker SB for left (r2 = .261, P = .0001) and right (r2 = .308, P = .0001) acetabula. Average thickness differences between left and right acetabular AC and SB were 0.13 mm (P = .015) and 0.11 mm (P = .026), respectively. Although it was the operated hip that had thicker articular tissues, the differences were within the pixel resolution (< 0.31 mm). CONCLUSION: AC and SB thickness distribution can be accurately determined by combining noninvasive MR imaging and analytic geometry, which may also provide a means for quantitative, longitudinal assessment of focal AC defects.

Computer-based speech recognition as a replacement for medical transcription.

OBJECTIVE: We have implemented computerized speech recognition in a high-volume clinical setting using a newly developed commercial software system. This paper compares the performance of the computerized system with conventional transcription during a trial week followed by 3 months of routine clinical use. CONCLUSION: The speech recognition system was used for 97% of the cases during the trial week and 87% of cases during the months of continuous use. For a similar mixture of cases, no change occurred in the length of reports after introduction of the computerized system. Speech recognition decreased the time until the report became available by 99% and resulted in a substantial savings in transcription costs. We conclude that speech recognition by computer is practical in a high-volume clinical implementation.

MR arthrography of the shoulder.

Although conventional MR imaging allows direct visualization of major anatomic structures, smaller intraarticular structures, including the glenoid labrum, glenohumeral ligaments, and articular surface of the rotator cuff tendon can be difficult to evaluate in the absence of a joint effusion. The authors review the techniques employed in performing MR arthrography, imaging characteristics of MR arthrography, and diagnostic utilization of the technique. Suggested indications are provided.

MR arthrography of the rotator cuff and labral-ligamentous complex.

In MR imaging of the shoulder, diagnostic success requires the delineation of complex anatomic structures and the demonstration of subtle abnormalities. Magnetic resonance (MR) arthrography extends the capabilities of conventional MR imaging because contrast solution separates intra-articular structures and outlines abnormalities. There are several major contributions of MR arthrography. In assessment of the rotator cuff, arthrographic MR images enable the accurate differentiation of full-thickness tears from other cuff abnormalities, as well as the determination of tendon quality. In shoulders with suspected glenohumeral instability, arthrographic MR images show the locations of labral tears relative to the origins of glenohumeral ligaments. This article illustrates normal arthrographic MR features of the shoulder as well as common pathological disorders of the rotator cuff and labral-ligamentous complex.

Knee and shoulder fractures: association of fracture detection and marrow edema on MR images with mechanism of injury.

PURPOSE: To assess the value of magnetic resonance (MR) imaging for enabling the classification of fracture mechanisms and to compare marrow edema caused by compressive forces with that caused by tensile forces. MATERIALS AND METHODS: In 62 knees or shoulders, 78 fractures were identified prospectively on MR images or plain radiographs; compressive or tensile forces were determined retrospectively to have caused impaction or distraction fractures, respectively. Edema was measured on T1-weighted images. Frequencies of fracture detection on MR images or plain radiographs were compared. RESULTS: Forty-nine (63%) and 29 (37%) fractures were attributed to compressive and tensile forces, respectively. Edema measured 31 mm +/- 10 in impaction fractures and 2.5 mm +/- 2.4 in distraction fractures (P < .001). MR images and plain radiographs of 63 fractures were compared. On MR images, distraction fractures, including four of seven Segond fractures, were missed more often than impaction fractures (P < .008). Fractures overlooked on MR images were associated with less edema (P < .003). CONCLUSION: On MR images, impaction fractures demonstrate prominent marrow edema, and distraction fractures demonstrate minimal edema. Impaction fractures are more often missed on plain radiographs, and distraction fractures are more often missed on MR images. Segond fractures should be suspected if MR images show lateral capsular ligamentous injury in the knee; in these cases, evaluation with plain radiography is warranted.

CT and MR imaging in the local staging of primary malignant musculoskeletal neoplasms: Report of the Radiology Diagnostic Oncology Group.

PURPOSE: To assess the relative accuracies of computed tomography (CT) and magnetic resonance (MR) imaging in the local staging of primary malignant bone and soft-tissue tumors. MATERIALS AND METHODS: At four institutions, 367 eligible patients (aged 6-89 years) with malignant bone or soft-tissue neoplasms in selected anatomic sites were enrolled. Patients underwent both CT and MR imaging within 4 weeks before surgery. In each patient, CT scans were interpreted independently by two radiologists and MR images by two other radiologists at the enrolling institution. The CT and MR images were then interpreted together by two of those radiologists and subsequently reread at the other institutions. Imaging and histopathologic findings were compared and were supplemented when needed with surgical findings. Receiver operating characteristic curve analysis and descriptive statistical analysis were performed. RESULTS: Cases were analyzable in 316 patients: 183 had primary bone tumors; 133 had primary soft-tissue tumors. There was no statistically significant difference between CT and MR imaging in determining tumor involvement of muscle, bone, joints, or neurovascular structures. The combined interpretation of CT and MR images did not statistically significantly improve accuracy. Interreader variability was similar for both modalities. CONCLUSION: CT and MR imaging are equally accurate in the local staging of malignant bone and soft-tissue neoplasms in the specific anatomic sites studied.

Vertebral fluid collection associated with vertebral collapse.

OBJECTIVE: Three elderly women with osteoporotic compression fractures of a vertebral body underwent MR imaging because of neurologic signs and symptoms. Atypical fluid collections were shown by MR imaging in all three patients. For histologic characterization of these vertebral fluid collections, CT-guided biopsies and aspirations were done for all three patients. CONCLUSION: After studying the clinical, histologic, and imaging features of these fluid collections associated with vertebral fracture, we suggest that they are most likely associated with underlying avascular necrosis.

Vertebral morphometry derived from digital images.

OBJECTIVE: We describe a method for capturing measurement data directly from digitized images using specialized software and high-resolution workstations. We have evaluated the reliability, accuracy, and reproducibility of this method in an international clinical trial involving vertebral morphometry. MATERIALS AND METHODS: Accuracy was determined using clinical radiographs measured with vernier calipers and a film phantom. Intra- and interobserver variabilities were assessed, and longitudinal reproducibility was evaluated. As part of the trial, spinal radiographs were collected from more than 200 international health care facilities and digitized at four screening centers. Digitized images were stored and sent to our central facility for morphometry and archiving. Timeliness and variability of the process were tracked. RESULTS: Relative accuracy was nearly 100%. Correlation with clinical measurements was high (r = .96; p < .05). The mean coefficient of variation for interobserver variability was 2%. Intraobserver variation was 3-5%. The coefficient of variation for longitudinal reproducibility ranged from 4% to 6%. After 9 months of operation, our trial included 9494 patients. Of approximately 36,000 radiographs, 98% passed quality review. Only 1% of vertebral levels were not measurable. Hardware and software problems were minimal. CONCLUSION: The use of digitized images for morphometry is accurate, reproducible, and convenient. When applied to a large-scale clinical trial, it offers unique advantages that may justify the cost and complexity that exceed those of conventional radiographs.

Quantification of articular cartilage in the knee with three-dimensional MR imaging.

RATIONALE AND OBJECTIVES: To determine the volume of articular cartilage in cadavers, patients, and healthy volunteers by using a volumetric, fat-suppressed spoiled gradient-recalled signal acquisition in the steady state (SPGR) magnetic resonance (MR) sequence. METHODS: Sagittal MR images were obtained with a fat-suppressed SPGR sequence (repetition time, 52 msec; echo time, 10 msec; 60 degrees flip angle; 3.0-3.5-mm partitions, 256 x 192 matrix, two signals acquired). The cartilaginous surfaces of the tibia, femur, and patella were planimetrically defined with a three-dimensional workstation. A three-dimensional model volume was created by threshold segmenting the cartilage from the adjacent tissues. The volume as calculated by using MR imaging was compared with the actual volume of the cartilage specimens. RESULTS: Observed measurements correlated with actual weight and volume displacement measurements with an accuracy of 82%-99% and linear correlation coefficients of 0.99 (P = 2.5e-15) and 0.99 (P = 4.4e-15). Precision of segmentation in healthy volunteers yielded a coefficient of variation of 0.4% for interobserver variability and 0.3% for intraobserver variability. CONCLUSION: This pilot study suggests that accurate volumetric calculations of knee articular cartilage are possible with currently available MR imaging pulse sequences and a commercially available work station.

The Buford complex--a variation of normal shoulder anatomy: MR arthrographic imaging features.

OBJECTIVE: The purpose of this study was to show the MR arthrographic imaging features of a normal anatomic variation of the shoulder: the absence of the anterior superior labrum and the presence of a "cordlike" middle glenohumeral ligament,which together are known as the Buford complex. MATERIALS AND METHODS: We retrospectively analyzed the MR arthrographic examinations of 10 patients with arthroscopically proven Buford complexes. RESULTS: MR arthrographic examinations showed an absent anterior superior labrum and an associated cordlike middle glenohumeral ligament in all patients. No contiguous tear of the superior labrum or anterior inferior labrum was evident. Originally, this variation was mistakenly diagnosed as a labral avulsion in two of the 10 patients. Also, a differential diagnosis of a superior labral tear was mistakenly offered for four patients. CONCLUSION: An absent anterior superior labrum and an associated cordlike middle glenohumeral ligament represent the normal variation that is known as the Buford complex rather than an avulsed labrum. This normal variation may be mistaken for a detached labrum.

Magnetic resonance imaging of rheumatoid arthritis.

MR imaging is able to demonstrate both the structural changes that occur in rheumatoid arthritis and the inflammatory changes, including synovial proliferation and joint effusion. MR imaging can demonstrate erosion before it is visible on radiographs. Although MR imaging appears to be very helpful in assessing the severity of rheumatoid arthritis and its response to therapy, the optimal technique for this assessment and the ultimate clinical value of MR imaging have yet to be determined.

MR arthrography: is it worthwhile?

Magnetic resonance (MR) arthrography is possible in any joint in which standard arthrography is performed. The diagnostic potential of this technique is optimized in the assessment of complex anatomical structures and intra-articular abnormalities that are difficult to visualize on conventional MR images. This paper presents the most common applications of MR arthrography in the shoulder, hip, knee, ankle, elbow and wrist, and explores the clinical indications in which MR arthrography adds the greatest benefit compared to standard arthrography and conventional MR imaging. Arthrographic MR images are most valuable in the evaluation of glenoid and acetabular labra, tendons of the rotator cuff, post-operative menisci, osteochondral fractures and loose bodies.