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Pitfalls in interpreting rat knee joint magnetic resonance images and their histological correlation
Hao-Hao Wang1, Yi-Xiang J Wang, J F Griffith
1Department of Oncological Surgery, First Affiliated Hospital, College of Medicine, Zhejiang University, Zhejiang Province, Hangzhou, China.
Background:
Magnetic resonance (MR) imaging has been increasingly used as an investigational tool for assessing the structure and function of animal joint disease models, while to date MR tomographic knowledge of laboratory animal skeletal microanatomy remains limited.
Purpose:
To describe pitfalls in interpreting rat knee joint MR images and their histological correlation.
Material And Methods:
MR scans of the right knee of five 3-month-old Sprague-Dawley (SD) rats were carried out using a 4.7T magnet, using a fat-suppressed three-dimensional (3D) gradient echo sequence with a spatial resolution of 59 x 117 x 234 microm. Histology assessment with hematoxylin and eosin staining and Safranin O staining was carried out in the five 3-month-old SD rats and two SD rats of 1 month and 6 months old, respectively. MR images were analyzed by a radiologist, and histology data were assessed by a radiologist and a pathologist.
Results:
Though the MR images were acquired in normal rats, many signs unfamiliar to radiologists were noted, including notch-like bright signal areas in the epiphysis, gray signal areas in the epiphysis, and fuzzy joint surface of the epiphysis of the femur and tibia. Detailed inspection of the histology specimen showed more unfamiliar features of rat knee microanatomy, including curvy or dipped surface of the femur/tibia epiphysis, areas composed of a mixture of cartilage and bone components, normal notch structure, cyst-like structure, and cavity between cortical lamellae under the joint cartilage.
Conclusion:
There are a number of normal microstructures of the rat knee joint that can be potentially misinterpreted as arthritic changes on MR images. Recognizing these rat knee microstructures can help correct image reading during biomedical research.
Insights
Normal rat knee microanatomy on MRI can mimic arthritis. Recognizing these features is crucial for accurate interpretation in animal research, improving diagnostic precision.
Area of Science:
- Veterinary Radiology
- Comparative Anatomy
- Biomedical Imaging
Background:
- Magnetic resonance (MR) imaging is vital for studying animal models of joint disease.
- Limited knowledge exists on the detailed skeletal microanatomy of laboratory animals using MR imaging.
Purpose of the Study:
- To identify and describe potential misinterpretations of rat knee joint MR images.
- To correlate MR imaging findings with histological data for accurate anatomical understanding.
Main Methods:
- MR imaging of rat knees using a 4.7T magnet and a 3D gradient echo sequence.
- Histological analysis of rat knee joints using H&E and Safranin O staining.
- Image and histology assessment by radiologists and a pathologist.
Main Results:
- Unfamiliar MR signal characteristics were observed in normal rat knees, including epiphyseal bright and gray signals and fuzzy joint surfaces.
- Histology revealed complex microanatomical features such as curvy epiphyses, cartilage-bone mixtures, normal notches, and subchondral cavities.
- These normal anatomical variations can be mistaken for pathological changes.
Conclusions:
- Normal rat knee microstructures can be misinterpreted as arthritic changes on MR images.
- Accurate identification of these normal anatomical features is essential for correct image interpretation in research settings.
