Faculty Bibliography

PURPOSE/OBJECTIVE:To compare six new three-dimensional (3D) magnetic resonance (MR) methods for evaluating knee cartilage at 3.0T. MATERIALS AND METHODS/METHODS:We compared: fast-spin-echo cube (FSE-Cube), vastly undersampled isotropic projection reconstruction balanced steady-state free precession (VIPR-bSSFP), iterative decomposition of water and fat with echo asymmetry and least-squares estimation combined with spoiled gradient echo (IDEAL-SPGR) and gradient echo (IDEAL-GRASS), multiecho in steady-state acquisition (MENSA), and coherent oscillatory state acquisition for manipulation of image contrast (COSMIC). Five-minute sequences were performed twice on 10 healthy volunteers and once on five osteoarthritis (OA) patients. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured from the volunteers. Images of the five volunteers and the five OA patients were ranked on tissue contrast, articular surface clarity, reformat quality, and lesion conspicuity. FSE-Cube and VIPR-bSSFP were compared to IDEAL-SPGR for cartilage volume measurements. RESULTS:FSE-Cube had top rankings for lesion conspicuity, overall SNR, and CNR (P < 0.02). VIPR-bSSFP had top rankings in tissue contrast and articular surface clarity. VIPR and FSE-Cube tied for best in reformatting ability. FSE-Cube and VIPR-bSSFP compared favorably to IDEAL-SPGR in accuracy and precision of cartilage volume measurements. CONCLUSION/CONCLUSIONS:FSE-Cube and VIPR-bSSFP produce high image quality with accurate volume measurement of knee cartilage.

PURPOSE/OBJECTIVE:To compare the diagnostic performance of iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) gradient-recalled acquisition in steady-state (GRASS) imaging with a routine magnetic resonance (MR) imaging protocol for evaluating knee cartilage at 3.0 T in patients by using arthroscopy as the reference standard. MATERIALS AND METHODS/METHODS:This prospective Health Insurance Portability and Accountability Act-compliant study was performed with a waiver of informed consent from the institutional review board. IDEAL GRASS was added to routine 3.0-T knee MR protocol performed in 95 symptomatic patients (48 males, mean age, 34.5 years; 47 females, mean age, 35.5 years) who underwent subsequent arthroscopic surgery. Radiologists used the routine MR protocol during the first review and IDEAL GRASS during the second to grade each articular surface and to determine the presence of meniscal tears. By using arthroscopy as the reference standard, the sensitivity, specificity, and accuracy of both imaging methods for detecting cartilage lesions and meniscal tears were determined. RESULTS:By using the z test to compare parameters between methods, the respective sensitivity, specificity, and accuracy for detecting all 192 cartilage lesions were 68.5%, 92.6%, and 84.5% for IDEAL GRASS and 66.1%, 92.9%, and 83.9% for the routine MR protocol. There was no significant difference (P = .34-.83) in parameters between methods for detecting cartilage lesions. The respective parameters for detecting 50 medial meniscal tears were 85.0%, 91.1%, and 87.9% for IDEAL GRASS and 94.0%, 90.0%, and 92.1% for the routine MR protocol. The parameters for detecting 31 lateral meniscal tears were 58.0%, 90.6%, and 80.0% for IDEAL GRASS and 80.1%, 91.4%, and 87.9% for the routine MR protocol. The routine MR protocol had a significantly higher sensitivity for detecting medial meniscal tears (P = .04) and lateral meniscal tears (P = .01) and significantly higher accuracy for detecting lateral meniscal tears (P = .03) than IDEAL GRASS. CONCLUSION/CONCLUSIONS:IDEAL GRASS has similar diagnostic performance as routine MR protocol for evaluating the articular cartilage of the knee in clinical patients at 3.0 T but has significantly lower sensitivity and accuracy for detecting meniscal tears.

Fat/water separation methods such as fluctuating equilibrium magnetic resonance and linear combination steady-state free precession have not yet been successfully implemented at 3.0 T due to extreme limitations on the time available for spatial encoding with the increase in magnetic field strength. We present a method to utilize a three-dimensional radial sequence combined with linear combination steady-state free precession at 3.0 T to take advantage of the increased signal levels over 1.5 T and demonstrate high spatial resolution compared to Cartesian techniques. We exploit information from the two half-echoes within each pulse repetition time to correct the accumulated phase on a point-by-point basis, thereby fully aligning the phase of both half-echoes. The correction provides reduced sensitivity to static field (B(0)) inhomogeneity and robust fat/water separation. Resultant images in the knee joint demonstrate the necessity of such a correction, as well as the increased isotropic spatial resolution attainable at 3.0 T. Results of a clinical study comparing this sequence to conventional joint imaging sequences are included.

PURPOSE/OBJECTIVE:To determine whether a three-dimensional isotropic resolution fast spin-echo sequence (FSE-Cube) has similar diagnostic performance as a routine magnetic resonance (MR) imaging protocol for evaluating the cartilage, ligaments, menisci, and osseous structures of the knee joint in symptomatic patients at 3.0 T. MATERIALS AND METHODS/METHODS:This prospective, HIPAA-compliant, institutional review board-approved study was performed with a waiver of informed consent. FSE-Cube was added to the routine 3.0-T MR imaging protocol performed in 100 symptomatic patients (54 male patients with a median age of 32 years and 46 female patients with a median age of 33 years) who subsequently underwent arthroscopic knee surgery. All MR imaging studies were independently reviewed twice by two musculoskeletal radiologists. During the first review, the routine MR imaging protocol was used to detect cartilage lesions, ligament tears, meniscal tears, and bone marrow edema lesions. During the second review, FSE-Cube with multiplanar reformations was used to detect these joint abnormalities. With arthroscopic results as the reference standard, the sensitivity and specificity of FSE-Cube and the routine MR imaging protocol in the detection of cartilage lesions, anterior cruciate ligament tears, and meniscal tears were calculated. Permutation tests were used to compare sensitivity and specificity values. RESULTS:FSE-Cube had significantly higher sensitivity (P = .039) but significantly lower specificity (P = .003) than the routine MR imaging protocol for detecting cartilage lesions. There were no significant differences (P = .183-.999) in sensitivity and specificity between FSE-Cube and the routine MR imaging protocol in the detection of anterior cruciate ligament tears, medial meniscal tears, or lateral meniscal tears. FSE-Cube depicted 96.2% of medial collateral ligament tears, 100% of lateral collateral ligament tears, and 85.3% of bone marrow edema lesions identified on images obtained with the routine MR imaging protocol. CONCLUSION/CONCLUSIONS:FSE-Cube has similar diagnostic performance as a routine MR imaging protocol for detecting cartilage lesions, cruciate ligament tears, collateral ligament tears, meniscal tears, and bone marrow edema lesions within the knee joint at 3.0 T.

PURPOSE/OBJECTIVE:To compare a vastly undersampled isotropic projection steady-state free precession (VIPR-SSFP) sequence and routine magnetic resonance (MR) imaging for evaluating the cartilage, ligaments, menisci, and osseous structures of the knee in symptomatic patients. MATERIALS AND METHODS/METHODS:All subjects signed written informed consent prior to participation in this prospective, HIPAA-compliant, institutional review board-approved study. VIPR-SSFP was added to the routine 1.5-T MR imaging performed on 95 symptomatic patients (52 men, 43 women; average age, 41.6 years) who subsequently underwent arthroscopic knee surgery. All MR examinations were independently reviewed twice by two musculoskeletal radiologists to detect cartilage lesions, anterior and posterior cruciate ligament tears, meniscal tears, and bone marrow edema lesions, first by using routine MR and second by using VIPR-SSFP. By using arthroscopy as the reference standard, the sensitivity and specificity of both MR protocols were calculated. The z test was used to compare sensitivity and specificity values. RESULTS:VIPR-SSFP had significantly higher specificity (P < .01) for helping detect cartilage lesions (92.2% for VIPR-SSFP and 88.4% for routine MR), while routine MR had significantly higher sensitivity (P = .02) and accuracy (P = .05) for helping detect lateral meniscal tears (73.2% sensitivity and 88.4% accuracy for VIPR-SSFP and 87.5% specificity and 93.2% accuracy for routine MR). There was no significant difference (P = .14 to >.99) between VIPR-SSFP and routine MR in the remaining sensitivity and specificity values. VIPR-SSFP helped detect 69.3% of bone marrow edema lesions identified at routine MR. CONCLUSION/CONCLUSIONS:VIPR-SSFP can provide important clinical information regarding the cartilage, ligaments, menisci, and osseous structures of the knee, but is less sensitive than conventional MR imaging at helping detect lateral meniscal tears and bone marrow edema lesions.

PURPOSE/OBJECTIVE:To retrospectively compare the diagnostic performance of 1.5- and 3.0-T magnetic resonance (MR) imaging protocols for evaluating the articular cartilage of the knee joint in symptomatic patients. MATERIALS AND METHODS/METHODS:This HIPAA-compliant study was performed with a waiver of informed consent from the institutional review board. The study group consisted of 200 symptomatic patients undergoing MR examination of the knee at 1.5 T (61 men, 39 women; mean age, 38.9 years) or 3.0 T (52 men, 48 women; mean age, 39.1 years), who also underwent subsequent arthroscopic knee surgery. All MR examinations consisted of multiplanar fast spin-echo sequences with similar tissue contrast at 1.5 and 3.0 T. All articular surfaces were graded at arthroscopy by using the Noyes classification system. Three musculoskeletal radiologists retrospectively and independently graded all articular surfaces seen at MR imaging by using a similar classification system. The sensitivity, specificity, and accuracy of the 1.5- and 3.0-T MR protocols for detecting cartilage lesions were determined by using arthroscopy as the reference standard. The z test was used to compare sensitivity, specificity, and accuracy values at 1.5 and 3.0 T. RESULTS:For all readers combined, the respective sensitivity, specificity, and accuracy of MR imaging for detecting cartilage lesions were 69.3%, 78.0%, and 74.5% at 1.5 T (n = 241) and 70.5%, 85.9%, and 80.1% at 3.0 T (n = 226). The MR imaging protocol had significantly higher specificity and accuracy (P < .05) but not higher sensitivity (P = .73) for detecting cartilage lesions at 3.0 T than at 1.5 T. CONCLUSION/CONCLUSIONS:A 3.0-T MR protocol has improved diagnostic performance for evaluating the articular cartilage of the knee joint in symptomatic patients when compared with a 1.5-T protocol.

PURPOSE/OBJECTIVE:To evaluate and quantify improvements in the quality of fat suppression for fast spin-echo imaging of the knee using multipeak fat spectral modeling and IDEAL fat-water separation. MATERIALS AND METHODS/METHODS:T(1)-weighted and T(2)-weighted fast spin-echo sequences with IDEAL fat-water separation and two frequency-selective fat-saturation methods (fat-selective saturation and fat-selective partial inversion) were performed on 10 knees of five asymptomatic volunteers. The IDEAL images were reconstructed using a conventional single-peak method and precalibrated and self-calibrated multipeak methods that more accurately model the NMR spectrum of fat. The signal-to-noise ratio (SNR) was measured in various tissues for all sequences. Student t-tests were used to compare SNR values. RESULTS:Precalibrated and self-calibrated multipeak IDEAL had significantly greater suppression of signal (P < 0.05) within subcutaneous fat and bone marrow than fat-selective saturation, fat-selective partial inversion, and single-peak IDEAL for both T(1)-weighted and T(2)-weighted fast spin-echo sequences. For T(1)-weighted fast spin-echo sequences, the improvement in the suppression of signal within subcutaneous fat and bone marrow for multipeak IDEAL ranged between 65% when compared to fat-selective partial inversion to 86% when compared to fat-selectivesaturation. For T2-weighted fast spin-echo sequences, the improvement for multipeak IDEAL ranged between 21% when compared to fat-selective partial inversion to 81% when compared to fat-selective saturation. CONCLUSION/CONCLUSIONS:Multipeak IDEAL fat-water separation provides improved fat suppression for T(1)-weighted and T(2)-weighted fast spin-echo imaging of the knee when compared to single-peak IDEAL and two widely used frequency-selected fat-saturation methods.

OBJECTIVE:The purpose of our study was to determine whether tears of the posterior root of the lateral meniscus can be diagnosed using standard MR criteria of a meniscal tear in the presence or absence of an anterior cruciate ligament (ACL) tear. MATERIALS AND METHODS/METHODS:From a series of 559 knee MR examinations with arthroscopic correlation, we selected all 16 proven tears isolated to the posterior root of the lateral meniscus for retrospective blinded review, along with 45 cases of arthroscopically intact lateral meniscal posterior roots. The reviewers categorized whether there was a torn, possibly torn, or intact root based on three specific coronal and three specific sagittal image locations. RESULTS:When all possibly torn roots were considered as torn, the sensitivity and specificity for diagnosis of a root tear were 93% and 89%, respectively. The observers' overall diagnosis of a tear based on all images gave a higher combined sensitivity and specificity than if the diagnosis of a tear had been based on one or any combination of the three coronal and three sagittal locations. Root tears were significantly more common in the presence of an ACL tear (p < 0.0001), but the presence or absence of an ACL tear did not change MR diagnostic accuracy. CONCLUSION/CONCLUSIONS:The standard MR criteria of meniscal distortion and signal to the surface can be used to diagnose lateral meniscal root tears. The presence or absence of an ACL tear did not change diagnostic accuracy.

Recent advances have reduced scan time in three-dimensional fast spin echo (3D-FSE) imaging, including very long echo trains through refocusing flip angle (FA) modulation and 2D-accelerated parallel imaging. This work describes a method to modulate refocusing FAs that produces sharp point spread functions (PSFs) from very long echo trains while exercising direct control over minimum, center-k-space, and maximum FAs in order to accommodate the presence of flow and motion, SNR requirements, and RF power limits. Additionally, a new method for ordering views to map signal modulation from the echo train into k(y)-k(z) space that enables nonrectangular k-space grids and autocalibrating 2D-accelerated parallel imaging is presented. With long echo trains and fewer echoes required to encode large matrices, large volumes with high in- and through-plane resolution matrices may be acquired with scan times of 3-6 min, as demonstrated for volumetric brain, knee, and kidney imaging.

OBJECTIVE:The objective was to evaluate magnetic resonance imaging (MRI) findings in patients with fibular stress injuries. MATERIALS AND METHODS/METHODS:The study group consisted of 20 patients with clinically diagnosed fibular stress injuries who were evaluated with MRI. Radiographs were performed in 14 of the 20 patients. The MRI examinations and radiographs were retrospectively reviewed in consensus by two musculoskeletal radiologists. RESULTS:All 20 patients with clinically diagnosed fibular stress injuries had periosteal edema and bone marrow edema within the fibula on MRI. The periosteal reaction and bone marrow edema were present within the distal fibula in 14 patients, the middle fibula in 1 patient, and the proximal fibula in 5 patients. The periosteal reaction was located on the anterior cortex in 1 patient, the posterior cortex in 4 patients, the lateral cortex in 11 patients, and circumferentially distributed throughout the cortex in 4 patients. Nine patients had abnormal T1 and T2 signal intensity within the fibular cortex. Initial and follow-up radiographs showed periosteal reaction in 15% and 50% of patients with fibular stress injuries respectively. CONCLUSIONS:The majority of fibular stress injuries involve the lateral cortex of the distal fibula.