High Resolution MRI of Small Joints: Impact of Spatial Resolution on Diagnostic Performance and SNR

doi:10.1016/S0730-725X(97)00244-0

Magnetic Resonance Imaging

Volume 16, Issue 2, February 1998, Pages 147-155

https://doi.org/10.1016/S0730-725X(97)00244-0 Get rights and content

Abstract

This study focuses on the spatial resolution required for cartilage imaging. The purposes of this study were (I) to analyze the diagnostic performance in diagnosing artificially produced cartilage lesions in a small joint model using an optimized fat saturated three-dimensional gradient-echo sequence, (II) to relate the lesion size and depth as diagnosed in the magnetic resonance images with the corresponding pathologic findings and (III) to assess signal-to-noise (SNR) ratios for each of the protocols. Twenty-five artificial cartilage lesions were created in the knee joints of 10 rabbits. These specimens and seven specimens without lesions were imaged at 1.5 T using a three-dimensional gradient-echo sequence with varying slice thickness, field of view and matrix. A total of 404 corresponding images were selected, 50% with and 50% without cartilage lesions. Six radiologists scored all images according to five levels of confidence and receiver operating characteristic (ROC) analysis was performed. Lesion size and depth were compared to the corresponding pathological specimen sections. Additionally SNR ratios were calculated. ROC analysis of pooled data from all readers showed the highest area under the ROC curve for the sequence with the highest spatial resolution, while the diagnostic performance was significantly lower in the other sequences (p <0.01). Assessment of the lesion size and depth was correct in 45% and 40% respectively with the highest resolution and in 29% and 23% with the lowest resolution. SNR ratios decreased with increasing spatial resolution. In conclusion this study shows that increasing spatial resolution improves diagnostic performance in cartilage lesions, though SNR decreases substantially. Assessment of correct lesion size and depth still is limited.

Introduction

The diagnosis of subtle cartilage lesions and the reliable evaluation of changes in cartilage structure are prerequisites to analyze joint trauma as well as inflammatory and non-inflammatory joint disease.1, 2, 3 In addition a precise imaging technique is required to monitor disease progression in patients with joint disease.[4] Magnetic resonance imaging (MRI) is the only imaging modality that can visualize cartilage in three dimensions in arbitrary orientations and non-invasively. Requirements to depict subtle changes in cartilage morphology are substantial and standard imaging sequences are not suited for this application.5, 6, 7, 8 To obtain reliable results high resolution imaging sequences have been used in combination with fat saturation techniques.3, 9, 10

In this study we used optimized fat-saturated high resolution three dimensional gradient-echo (GE) sequences with different spatial resolutions. The diagnostic performance was determined for artificial cartilage lesions created in knee specimens of rabbits and related to the spatial resolution as well as to the lesion size. Additionally signal to noise (SNR) ratios were calculated and image quality assessed in each image.

Section snippets

Animal Model

The experiments were performed with 17 fresh knee joint specimens of adult New Zealand rabbits that were sacrificed in cardiological and ophthalmological studies. All of the knee joints were opened through a medial parapatellar incision. After incision of the joint capsule the patella was dislocated laterally and the joint flexed to obtain an optimal approach to the femoral condyles. In 10 specimens cartilage lesions were created at the medial and lateral femoral condyle while in 7 joints no

ROC Analysis

ROC analysis showed that each of the six radiologists achieved the most accurate results using the sequences with the highest spatial resolution (Table 1). Using pooled data direct comparison showed a decreasing AUC with decreasing matrix size and increasing FOV as well as slice thickness (Fig. 2). These differences were statistically significant (p < 0.01). Both pathologic and non-pathologic images were evaluated with a higher degree of confidence with the highest matrix size, the smallest

Discussion

The development of surgical and pharmacological methods for the treatment and prevention of chondral degeneration and injury has created a need for an accurate imaging technique for the treatment and prevention of chondral degeneration and injury.15, 16, 17, 18 MRI is the evolving technique for the noninvasive assessment of cartilage. As shown in a previous study, however, major limitations were encountered using standard sequences, optimized for cartilage imaging.[5] With current technologies

Conclusion

In conclusion, we have shown that SNR ratios decrease with increasing spatial resolution. Using a setting applicable to in vivo examinations, even with the highest spatial resolutions SNR levels were adequate to improve diagnostic performance. Using high resolution techniques a reliable diagnosis in cartilage lesions may be obtained, although limitations in correctly assessing lesion size and depth are encountered.

Acknowledgements

Acknowledgments—This work was supported by German Research Society Grant LI 710, 1-1. We are grateful to Evelyn Procter and Niles Bruce for meticulously performing the MRI examinations.

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Original ContributionHigh Resolution MRI of Small Joints: Impact of Spatial Resolution on Diagnostic Performance and SNR

Abstract

Introduction

Section snippets

Animal Model

ROC Analysis

Discussion

Conclusion

Acknowledgements

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Emerging applications of magnetic resonance imaging in the evaluation of articular cartilage

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Artificially produced cartilage lesions in small JointsDetection with optimized MRI-sequences

Magn. Reson. Imaging

Knee joint cartilage defectsA comparative study of MR and anatomic sections

J. Comput. Assist. Tomogr.

Width of the articular cartilage of the hipQuantification by using fat suppression spin -echo MR imaging in cadavers

AJR Am. J. Roentgenol.

Abnormalities of articular cartilage in the kneeAnalysis of available MR technique

Radiology

Quantification of articular cartilage in the knee with pulse saturation transfer subtraction and fat-suppressed MR imagingOptimization and validation

Radiology

Accuracy of fat-suppressed three-dimensional spoiled gradien-echo FLASH MR Imaging in the detection of patellofemoral articular cartilage abnormalities

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Original Contribution
High Resolution MRI of Small Joints: Impact of Spatial Resolution on Diagnostic Performance and SNR