OBJECTIVE-MRI is the most accurate noninvasive method available to diagnose disorders of articular cartilage. Conventional 2D and 3D approaches show changes in cartilage morphology. Faster 3D imaging methods with isotropic resolution can be reformatted into arbitrary planes for improved detection and visualization of pathology. Unique contrast mechanisms allow us to probe cartilage physiology and detect changes in cartilage macromolecules. CONCLUSION-MRI has great promise as a noninvasive comprehensive tool for cartilage evaluation.Keywords balanced steady-state free precession imaging; bSSFP; cartilage; joint imaging; MRI; osteoarthritis; rapid imaging Articular cartilage pathology may be the result of degeneration or acute injury. Osteoarthritis is an important cause of disability in our society [1][2][3][4][5][6] and is marked by degeneration of articular cartilage [7][8][9]. Acute injury to cartilage can be characterized using MRI [10]. Whether the result is from degeneration or injury, MRI offers a noninvasive means of assessing the degree of damage to cartilage and adjacent bone and of measuring the effectiveness of treatment [11].Many imaging methods are available to assess articular cartilage. Conventional radiography can be used to detect gross loss of cartilage, evident as narrowing of the distance between the two adjacent bones of a joint [12], but it does not image cartilage directly. Secondary changes such as osteophyte formation can be seen, but conventional radiography is insensitive to early chondral damage. Arthrography, alone or combined with conventional radiography or CT, is mildly invasive and provides information limited to the contour of the cartilage surface [13]. MRI, with its excellent soft-tissue contrast, is the best imaging technique currently available for the assessment of articular cartilage [14][15][16][17][18][19]. Imaging regions of cartilage damage has the potential to provide morphologic information, such as fissuring and the presence of partial-or full-thickness cartilage defects. Cartilage lesions on MRI are often graded on a modified Outerbridge or Noyes scale, corresponding to arthroscopic grading [20][21][22]. A common grading scale is shown in Table 1. In addition to morphologic assessment, the many tissue © American Roentgen Ray Society Address correspondence to G. E. Gold (gold@stanford.edu).. An ideal MRI study for cartilage should provide accurate assessment of cartilage thickness and volume, show morphologic changes of the cartilage surface, show internal cartilage signal changes, and allow evaluation of the subchondral bone for signal abnormalities. Also, it would be desirable for MRI to provide an evaluation of the underlying cartilage physiology, including providing information about the status of the glycosaminoglycan (GAG) and collagen matrices. Conventional MRI sequences do not provide a comprehensive assessment of cartilage, lacking either in spatial resolution or specific information about cartilage physiology. NIH Public Access Conventional MRI Met...

Purpose-To evaluate two magnetic resonance imaging (MRI) techniques, Slice Encoding for Metal Artifact Correction (SEMAC) and Multi-Acquisition Variable-Resonance Image Combination (MAVRIC), for their ability to correct for artifacts in post-operative knees with metal.Materials and Methods-A total of 25 knees were imaged in this study. Fourteen total knee replacements (TKRs) in volunteers were scanned with SEMAC, MAVRIC, and two-dimensional fast spin-echo (FSE) to measure artifact extent and implant rotation. The ability of the sequences to measure implant rotation and dimensions was compared in a TKR knee model. Eleven patients with a variety of metallic hardware were imaged with SEMAC and FSE to compare artifact extent, and subsequent patient management was recorded.Results-SEMAC and MAVRIC significantly reduced artifact extent compared to FSE (p < 0.0001) and were similar to each other (p = 0.58), allowing accurate measurement of implant dimensions and rotation. The TKRs were properly aligned in the volunteers. Clinical imaging with SEMAC in symptomatic knees significantly reduced artifact (p < 0.05) and showed findings that were on the majority confirmed by subsequent non-invasive or invasive patient studies.Conclusion-SEMAC and MAVRIC correct for metal artifact, non-invasively providing highresolution images with superb bone and soft tissue contrast.

Purpose To compare 6 new three-dimensional (3D) magnetic resonance (MR) methods for evaluating knee cartilage at 3.0T. Materials and 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), Multi-echo 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 5 osteoarthritis (OA) patients. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured from the volunteers. Images of the 5 volunteers and the 5 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 < .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 FSE-Cube and VIPR-bSSFP produce high image quality with accurate volume measurement of knee cartilage.

Institutional review board approval and informed consent were obtained for this HIPAA-compliant study. The purpose was to prospectively compare multiecho iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) gradient-echo (GRE) magnetic resonance (MR) imaging with three-dimensional fat-suppressed (FS) spoiled GRE (SPGR) MR imaging to evaluate the articular cartilage of the knee. Six healthy volunteer and 10 cadaver knees were imaged at 1.5 T. Signal-to-noise ratio (SNR), SNR efficiency, and cartilage volume were measured. SNR and SNR efficiency were significantly higher with multiecho IDEAL GRE than with FS SPGR imaging (P < .031). Both methods produced equivalent cartilage volumes (overall concordance correlation coefficient, 0.998) with high precision and accuracy. The use of a cartilage phantom confirmed high accuracy in volume measurements and high reproducibility for both methods. Multiecho IDEAL GRE provides high signal intensity in cartilage and synovial fluid and is a promising technique for imaging articular cartilage of the knee.

Dedicated performance improvement methods may achieve significant and sustained improvement in mammographic breast positioning, which may better enable facilities to pass the recently instated Enhancing Quality Using the Inspection Program portion of a practice's annual Mammography Quality Standards Act inspections.