Magnetic resonance knee arthrography

Knee MR-arthrography in assessment of meniscal and chondral lesions

INTRODUCTION

No study, so far in France, has investigated the diagnosis value of knee MR-arthrography since the recent approval of intra-articular gadolinium use, by this country's healthcare authorities. This study objective is to verify the MR-arthrography superiority on conventional knee MRI, in meniscus and cartilage knee lesions diagnosing accuracy both in regard to sensitivity and specificity.

HYPOTHESIS

MR-arthrography, represents in some pathologic situations, a more accurate source of information than conventional MRI.

MATERIALS AND METHODS

Over a 27 months period, 25 patients, scheduled to undergo a knee arthroscopy volunteered, after having been fully informed of the possible interest and risk of the MR-arthrography examination, to participate in this study. Twenty-one of them were finally included since in four cases the surgical indication was not confirmed. The group consisted of 15 males and six females with an average age of 35.7 years. All of them consecutively underwent conventional MRI, MR-arthrography finally followed by arthroscopy. The MRI and MR-arthrograms results were compared to the arthroscopy findings using the nonparametric Kappa test.

RESULTS

To diagnose meniscal tears, statistical agreement measure for MRI with arthroscopy was good (K=0.69) but not as good as the MR-arthrography/arthroscopy agreement which, by itself was excellent (K=0.84). As a diagnosis tool, the sensitivity and specificity of MR-arthrography (respectively 100 and 89.6%) were much higher than the corresponding values observed in conventional MRI (92.3 and 82.8%, respectively) which nonetheless remain satisfactory. The meniscal tears characterization seemed to be better interpreted using MR-arthrography. As far as the chondral lesions in this series, they were predominantly located on the patellar surface and in the medial femorotibial compartment. For diagnosing the latter, the MRI/arthroscopy agreement was good (K=0.70) but not as good as the MR-arthrography/arthroscopy agreement (K=0.805) which can be rated excellent. The detection sensitivity thus increased by 10% with gadolinium intra-articular injection. However, assessment accuracy of the lesions depth was mediocre, with frequent errors for the intermediary stages.

DISCUSSION

Intra-articular gadolinium injection improved MRI performances for numerous reasons: filling the joint, reinforcing the synovial fluid signal, and enhancing anatomic structures contrast on the T1-weighted sequences images. In this study, MR-arthrography appeared to be superior to conventional MRI in meniscal and cartilaginous lesions diagnosis, confirming the results previously obtained in other countries. In light of these results and other data from the literature, MR-arthrography can be indicated as an alternative to CT-arthrography in various clinical situations: detection of recurrent tears on operated menisci, search for cartilaginous lesions or foreign bodies in the joint space, and preoperative assessment before chondral repair procedures. However, conventional MRI remains the reference examination for studying cartilage, because the low resolution of MR-arthrography limits its performances in quantitative assessment of lesions depth.

MR arthrography of the shoulder, hip, and wrist: evaluation of contrast dynamics and image quality with increasing injection-to-imaging time

OBJECTIVE

The purpose of our study was to investigate the contrast dynamics and the relationship between visualization of intraarticular structures and time elapsed between intraarticular injection of contrast agent and MRI in symptomatic patients referred for MR arthrography of the shoulder, hip, and wrist.

SUBJECTS AND METHODS

Our local ethics committees and the national drug administration approved this multicentric study. We prospectively studied 11 shoulders, 11 hips, and 10 wrists. After the intraarticular gadolinium injection, patients underwent a baseline MR arthrography protocol (time point [TP] 1) and subsequent MRI at another four time points (TP 2-TP 5) up to 240 minutes. The course of contrast-to-noise ratio (CNR) over time was calculated. Three observers assessed the degree of visualization of different intraarticular structures and the overall image quality at each time point using a 3-point scale and a 5-point scale, respectively.

RESULTS

For all joints, CNR measurements showed peak CNR at TP 1 (21 minutes) and TP 2 (45 minutes) with a subsequent, near-logarithmic decline of CNR values over time. Visualization of different anatomic structures decreased over time. Overall image quality was insufficient for diagnostic purposes at TP 3 (96 minutes) in three (27%) of 11 shoulders and in three (27%) of 11 hips. In two (20%) of 10 wrists, image quality was insufficient at TP 2 (45 minutes).

CONCLUSION

For MR arthrography, the degree of visualization of intraarticular structures depends on the time elapsed between contrast injection and MRI. MR arthrography of the shoulder and hip should be performed within 90 minutes, and MR arthrography of the wrist should be performed within 45 minutes, after intraarticular injection.

Effects of iodinated contrast and field strength on gadolinium enhancement: implications for direct MR arthrography

PURPOSE

To optimize direct magnetic resonance (MR) arthrography by determining the effect of dilution of gadolinium in iodinated contrast, saline, or albumin on T1-weighted, T2-weighted, and gradient-recalled echo (GRE) images, and the effect of scanner field strength.

MATERIALS AND METHODS

Gadopentetate dimeglumine was diluted into normal saline, albumin, or iodinated contrast (0.625 mmol/liter to 40 mmol/liter). Samples were scanned at 1.5T and 0.2T. Signal intensity was measured using T1-weighted spin-echo (SE), T2-weighted SE, and two- and three-dimensional GRE (20 degrees-75 degrees flip angle) sequences. Graphical analysis of signal intensity vs. gadolinium concentration was performed.

RESULTS

Albumin had no effect on gadolinium contrast. Dilution of gadolinium in iodinated contrast decreased signal intensity on all sequences compared to samples of identical concentration diluted in saline at both 1.5T and 0.2T: with a 2 mmol/liter gadolinium solution at 1.5T, signal was decreased by 26.1% on T1-weighted images, 31.7% on GRE20 images, and 28.9% on GRE45 images, and the T2 value decreased by 71.1%; at 0.2T, signal was decreased by 23.5% on T1-weighted images. On all sequences, the peak signal shifted to the left (lower gadolinium concentration) when diluted in iodinated contrast. Peak signal was also seen at different gadolinium concentrations on different sequences and field strength: at 1.5T, peak in saline/iodine was 2.5/0.625 mmol/liter on T1-weighted images, and 2.5/1.25 mmol/liter on GRE20 and GRE45 sequences. At 0.2T, peak in saline/iodine was 0.625-2.5/1.25 mmol/liter on T1-weighted images, 0.625-2.5/1.25 on GRE45 images, 2.5-10.0/1.25-5.0 mmol/liter on GRE65 images, and 1.25-5.0/0.625-1.25 mmol/liter on GRE75 images.

CONCLUSION

Dilution of gadolinium in iodinated contrast results in decreased signal on T1-weighted, T2-weighted, and GRE images compared to dilution in saline or albuminfor both 1.5-T and 0.2-T scanners; if gadolinium is diluted in iodinated contrast for MR arthrography, a lower concentration should be used because the peak is shifted to the left. The use of iodinated contrast should be minimized, as it may diminish enhancement and lower the sensitivity and specificity of MR arthrography. Optimal gadolinium concentration for MR arthrography is dependent on scanner field strength and a broader range of gadolinium concentration can be used to provide maximal signal at low field strength.

Gadolinium inhibits thymidine incorporation and induces apoptosis in chondrocytes

Magnetic resonance arthrography. a procedure where contrast agents containing gadolinium are administered intra-articularly, has become a useful tool in musculoskeletal diagnosis. Although considered safe for systemic use, toxicities in some tissues have been identified for both free gadolinium ion and the gadolinium chelates used as contrast. In this study, the effects of short-term exposure of articular chondrocytes to gadolinium contrast were examined by assaying for proteoglycan synthesis, cell proliferation, and apoptosis. Bovine chondrocytes were grown in monolayer culture and exposed to gadodiamide for 16 h. Proteoglycan synthesis was measured through incorporation of radiolabeled sulfate. Uptake of radiolabeled thymidine assessed cell proliferation. Apoptosis was detected using the TUNEL assay, where DNA strand breaks characteristic of apoptosis are labeled with fluorescent nucleotide. Proteoglycan synthesis was stimulated by lower dose exposure to gadodiamide. At higher doses, proteoglycan synthesis returned to baseline. Cell proliferation decreased following exposure to gadodiamide in a dose-dependent manner. Chondrocyte apoptosis was induced in a dose-dependent manner. Further work is needed to determine if these in vitro effects are present in the intact joint.

Temporal behavior of intraarticular gadolinium

PURPOSE

As imaging delays during MR arthrography can result in suboptimal studies and potential pitfalls in diagnosis, we sought to evaluate the temporal behavior of intraarticular Gd-DTPA.

METHOD

We prospectively studied four shoulders, four knees, and four hips. Two of each group received either an intraarticular injection of 3 mmol/L Gd-DTPA and iodinated contrast medium or 2 mmol/L Gd-DTPA and 0.9% saline. We measured contrast-to-noise ratio (CNR) and joint distention on serial T1-weighted sequences. Retrospectively, we measured CNR and imaging delays in 31 MR arthrography patients (20 shoulders, 7 knees, and 4 hips).

RESULTS

In the shoulder, maximal CNR and joint distention occurred at 15 min. CNR decreased 53% by 1 h. In the knee, maximal distention occurred at 1 h, whereas CNR peaked at 2.75 h and then declined 20 and 86% by 3.5 and 6.25 h, respectively. In the hip, peak CNR and distention occurred at 0.5 h. CNR declined 53% by 2 h. Both contrast mixtures yielded similar results.

CONCLUSION

MR arthrography may tolerate imaging delays of 1 h for the shoulder, 2 h for the hip, and 3.5 h for the knee.

Is a mixture of gadolinium and iodinated contrast material safe during MR arthrography?

OBJECTIVE

This study was designed to determine whether a mixture of iodinated contrast material and gadopentetate dimeglumine used during MR arthrography yields free gadolinium ion, a systemically toxic metal.

MATERIALS AND METHODS

Mixtures of commercially available nonionic and ionic iodinated contrast agent, gadopentetate dimeglumine, lidocaine, and epinephrine were analyzed using a spectrophotometric titration with a gadolinium ion titrant and methyl thymol blue indicator.

RESULTS

We found no significant dissociation of gadolinium ion when gadopentetate dimeglumine was mixed with iodinated contrast agents, lidocaine, or epinephrine in any of the dilutions tested.

CONCLUSION

Gadopentetate dimeglumine and iodinated contrast material can be mixed before MR imaging without any release of free gadolinium and are therefore safe for confirming the intraarticular placement of contrast material before MR arthrography.

Visualization of pressure distribution within loaded joint cartilage by application of angle-sensitive NMR microscopy

High-resolution MRI measurements on knee joints show a multilaminar appearance of the cartilage. This intracartilaginar structure, visualized as hypointense zones in T(2)-weighted MR images is based on the dipolar interaction of water molecules within regions of anisotropic arrangement of collagen network. Using the different angle dependence of the MR signal, zones of radially and tangentially oriented network structures can be distinguished. Information equivalent to that from polarization light microscopy can be derived noninvasively. This is demonstrated by polarization light microscopic reference investigations. It is shown that this multilaminar MRI appearance is sensitively influenced by mechanical stress. A model explaining the contrary behavior of loaded tangential and radial network structures is given. Based on this pressure dependence, a noninvasive determination of mechanical properties is possible. Using the variation of size and intensity of the hypointense zones under pressure, dynamic high resolution MRI yields noninvasive information about the intracartilaginar pressure distribution similar to photoelastic measurements. Magn Reson Med 43:884-891, 2000.

Magnetic resonance arthrography: current status

Magnetic resonance imaging (MRI) is frequently considered the best method of diagnosis in musculoskeletal disorders. Intraarticular fluid improves joint assessment by helping to delineate intraarticular structures, separating otherwise closely-apposed structures, and filling potential spaces which lie within or communicate with the joint. Initially, it was anticipated that plain MRI would replace arthrography. The message from our surgical colleagues is that this ideal has not yet been achieved. Greater precision should reduce the need for more invasive techniques, such as diagnostic arthroscopy which is why direct and indirect MR arthrography are being employed. This article reviews the current status of MR arthrography as an evolving technique in the imaging of joint disorders.

Iliotibial band friction syndrome: MR imaging findings in 16 patients and MR arthrographic study of six cadaveric knees

PURPOSE

To define magnetic resonance (MR) imaging findings in patients with the iliotibial band friction syndrome (ITBFS) and to correlate these findings with anatomic features defined at magnetic resonance (MR) arthrography in cadavers.

MATERIALS AND METHODS

The anatomic relationship of the iliotibial tract (ITT) to the lateral recesses of the knee joint and the lateral femoral epicondyle was investigated with MR arthrography at full extension and at 30 degrees and 60 degrees of knee flexion in six cadaveric knees. Seventeen MR imaging studies in 16 patients with ITBFS were evaluated.

RESULTS

In the cadaveric study, no interference of the lateral synovial recess with the lateral femoral epicondyle at full extension and at 30 degrees and 60 degrees of knee flexion was observed. In all specimens, correlation of MR images with macroscopic and microscopic sections revealed no primary bursa between the lateral femoral epicondyle and the ITT. In clinical studies, MR imaging findings of poorly defined signal intensity abnormalities or circumscribed fluid collections were located in a compartmentlike space confined laterally by the ITT and medially by the meniscocapsular junction, the lateral collateral ligament, and the lateral femoral epicondyle.

CONCLUSION

MR imaging accurately depicts the compartmentlike distribution of signal intensity abnormalities in patients with ITBFS.

The carpal ligaments in MR arthrography of the wrist: correlation with standard MRI and wrist arthroscopy

We assessed the value of three-compartment magnetic resonance (MR) wrist arthrography in comparison with non-enhanced magnetic resonance imaging (MRI) for the evaluation of 13 individual wrist ligaments in 35 patients with refractory wrist pain. In 20 of these patients MR findings were correlated with the findings from multiportal wrist arthroscopy. For MR imaging (1.5-T magnet) a three-dimensional volume acquisition with a gradient-recalled echo sequence and 0.6-1.0 mm effective slice thickness was used. The delineation of individual wrist ligaments was rated as "good" in 10% of non-enhanced MR and 90% of MR arthrography images. Ligament evaluation was possible with high diagnostic confidence in 11% by non-enhanced MR imaging and 90% by MR arthrography. With wrist arthroscopy as the standard of reference, average sensitivities/specificities/accuracies for the diagnosis of full-thickness ligamentous defects were 0.81/0.75/0.77 for non-enhanced MR imaging and 0.97/0.96/0.96 for MR arthrography. Our findings suggest that MR arthrography is more accurate than standard MRI in delineating and evaluating the ligaments of the wrist.

MR arthrography of the ankle

Injuries to the lateral ankle ligaments are extremely common. Many patients with acute injuries to the lateral ligament complex develop chronic ankle instability that requires surgical intervention. MR arthrography of the ankle plays a valuable role in identifying those patients who are most at risk for the development of chronic instability. MR arthrography of the ankle also aids in preoperative planning and in differentiating among other entities that can present as ankle instability.

MR-microscopic visualization of anisotropic internal cartilage structures using the magic angle technique

NMR microscopic studies of articular cartilage at 7.1 T are presented. Using a special experimental design, T2-weighted spin-echo images of cartilage-bone plugs were taken under variable angles with respect to the static magnetic field B0 to visualize the angular-dependent representation of internal matrix structures mediated by the collagen network arrangement. To quantify the observed orientational effect in the MR images, exact measurements of the transverse relaxation time T2 were taken using the CPMG sequence. The NMR experiments show the strong influence of the cartilage orientation with respect to the static magnetic field on the inhomogeneous appearance of the articular cartilage in the MR image. Additionally performed polarization light microscopic investigations demonstrate the direct relation between the oriented collagenous structures and the anisotropic regions observed in the MR images. A simple cartilage matrix model derived from the experimental findings is proposed, and consequences for the clinical assessment of the articular joint are discussed.

The diagnosis of meniscal tears in athletes. A comparison of clinical and magnetic resonance imaging investigations

This study evaluated the predictability of clinical examination alone in comparison with magnetic resonance imaging in the diagnosis of meniscal tears in competitive athletes. Ninety-three competitive athletes were prospectively investigated between 1992 and 1995. A total of 57 athletes were operated on based on clinical examination alone, and the 36 remaining athletes had magnetic resonance imaging before surgery. The correct diagnosis of a meniscal lesion was made on clinical examination alone in 83 athletes (89%) and on magnetic resonance imaging the correct diagnosis was also made in 89% of 36 athletes. The overall values for the clinical investigation of the medial and lateral menisci combined were 94.5%, 91.5%, 99%, 96.5%, 87% for accuracy, positive predictive value, negative predictive value, sensitivity, and specificity, respectively. The overall values for magnetic resonance imaging of the medial and lateral menisci combined were 95.5%, 96.5%, 91.5%, 98%, 85.5% for accuracy, positive predictive value, negative predictive value, sensitivity, and specificity, respectively.

Imaging in clinical trials

Imaging is likely to play an increasingly important role in clinical trials of antirheumatic drugs. The need to evaluate efficacy of a drug quickly often precludes the use of radiological evaluation as an outcome measure, particularly in chronic arthritides. New imaging techniques with the refinement to detect differential early change, often between drugs of comparable potency, would be advantageous. However, the trend to set up large scale multicentre trials that have adequate statistical power for the detection of change mitigates against the use of expensive imaging techniques of restricted access. The majority of drug trials, therefore, still resort to conventional radiology. With the new generation of drugs that have specific actions, sensitivity in comparing changes in synovium, cartilage, bone and adjacent soft tissues would be of value.

Magnetic resonance chondro-crassometry (MR CCM): a method for accurate determination of articular cartilage thickness?

A method for the assessment of articular cartilage thickness based on MRI is presented and its accuracy and reproducibility tested. Six specimens of human patellae were imaged, using a fat-suppressed FLASH 3D sequence, and sectioned with a high-precision band saw. The regional distribution of articular cartilage thickness was determined from the MR images and from the anatomical sections (intervals of 0.5 mm). With image analysis 50-90% of the image points were found to lie within exactly the same thickness interval in corresponding patterns, and less than 17% deviated more than 0.5 mm. More than 85% of all pixels were reproducible with MRI after new positioning of the joint. No influence of the read-out direction and no important differences between areas of thin and thick cartilage could be detected. The authors conclude that MR chondro-crassometry can provide accurate and reproducible information on cartilage thickness.

Quantitation of articular cartilage using magnetic resonance imaging and three-dimensional reconstruction

A quadrature knee coil was used in conjunction with a magnetic resonance imaging scanner for quantitation of test phantom volumes, ex vivo bovine cartilage thickness, and in vivo human articular cartilage volumes. Optimal magnetic resonance parameters were obtained by testing a series of spin-echo and gradient-echo pulse sequences to determine the sequence that provided the highest resolution of articular cartilage and best defined the cartilage interfaces with synovial fluid and subchondral bone. Extensive testing revealed that two sequences were required to define articular cartilage accurately: a spoiled gradient-echo sequence and a steady state free-precession sequence. Three-dimensional reconstruction and statistical analyses of test phantoms and of bovine and human cartilage images were performed. Differences between actual phantom volumes and three-dimensional measurements demonstrated that, as magnetic resonance slice thickness was increased, the measurement variability also increased (coefficient of variation ranging from 1.7 +/- 1.3% for 1.0 mm slice thickness to 22.7 +/- 1.9% for 3.0 mm slice thickness). When the phantom volume was greater than 1,800 mm3, the intraobserver, interobserver and interscan accuracies were greater than 97, 98, and 96%, respectively. This high degree of reproducibility pertained for the data on in vivo human cartilage data also. For experienced observers, the intraobserver and interobserver reproducibility were greater than 98 and 97%, respectively. The interscan reproducibility was greater than 98%. These data demonstrate that improved magnetic resonance pulse sequencing, in conjunction with three-dimensional reconstruction and measurement techniques, can accurately and reproducibly measure the volume of articular cartilage. Clinical application of this approach offers the potential for early diagnosis of osteoarthritis and for serial, noninvasive assessment of changes in articular cartilage volume in response to therapeutic modalities.

MRI of the patellofemoral joint

In routine MRI of the knee, less attention frequently is paid to the patellofemoral joint and its surrounding structures than to the menisci and ligaments. This article reviews MRI of common abnormalities of the anterior aspect of the knee. Chondromalacia patellae, pathological softening of the patellar cartilage, can be diagnosed with reasonable accuracy with MRI using standard sequences. Abnormalities of alignment can be assessed grossly on static images, but more sophisticated evaluation of patellofemoral tracking requires the kinematic technique. Other traumatic or overuse injuries involving the extensor mechanism of the knee, such as the quadriceps and patellar tendons, are also reviewed briefly.