Study Subjects
This prospective study was approved by the Medical Ethics Committee at Shenzhen Hospital (Futian) of Guangzhou University of Chinese Medicine (No.GZYLL(KY)-2022-039). Written informed consent was obtained from all study participants prior to their inclusion. The study population consisted of individuals who underwent knee MRI scans at Shenzhen Hospital (Futian) of Guangzhou University of Chinese Medicine between February 2023 and February 2024. Previous research [7] has demonstrated gender variations in the elastic modulus of the meniscus. As a result, the research subjects were categorized into male and female groups based on the following inclusion criteria:
1. Chinese citizens aged between 40 and 69 years old.
2. Individuals who have not previously taken part in other clinical trial studies.
3. All participants must be willing to adhere to the experimental protocol and sign an informed consent form.
Exclusion criteria were as follows:
1. Patients with a history of knee joint surgery;
2. Pregnant or lactating women;
3. Individuals with heart disease, respiratory system diseases, or other serious illnesses that prevent them from undergoing ultrasound evaluation;
4. Individuals with skin damage or infection that makes them unsuitable for ultrasound examination;
5. Poor quality of SWE.
Instruments and Methods
The MRI examinations were conducted using the Philips Healthcare Ingenia 1.5T MRI scanner equipped with an 8-channel phased-array knee coil as the receiving coil. In the context of our investigation, the following MRI protocols were utilized for scanning:
The T1WI_TSE_SAG sequence was configured with a TR of 492 ms, a TE of 8 ms, a FOV measuring 160mm by 160mm by 79mm, and a voxel size of 0.5mm by 0.59mm by 3.0mm, with the entire scanning process taking 1 minute and 52 seconds.
For the T2WI_SPAIR_COR sequence, the parameters included a TR of 2865 ms, a TE of 70 ms, a FOV of 160mm by 160mm by 80mm, with voxel dimensions of 0.58mm by 0.69mm by 3.5mm, and the scan duration was 2 minutes and 52 seconds.
The T2WI_SPAIR_TRA sequence was set with a TR of 3000 ms, a TE of 60 ms, covering a FOV of 160mm by 160mm by 92mm, with voxel dimensions of 0.55mm by 0.65mm by 3.5mm, and the scanning time was 2 minutes and 36 seconds.
Lastly, the PDW_SPAIR_SAG sequence employed a TR of 2776 ms, a TE of 30 ms, a FOV of 160mm by 160mm by 79mm, and a voxel size of 0.62mm by 0.62mm by 3.0mm, with the scan time being 2 minutes and 52 seconds.
Patients were situated in a supine position, ensuring both knees were securely immobilized and aligned with an external rotation of 15 degrees to optimize stability. The imaging procedure was conducted in a craniocaudal approach, commencing at the level of the feet and progressing towards the head.
All SWE assessments were performed utilizing the Mindray Company's Resona 7T ultrasound diagnostic system. This system is furnished with an L14-5 high-frequency linear array transducer, which boasts a frequency spectrum spanning from 5 to 14 MHz, and is seamlessly integrated with SWE capabilities.
Initially, a senior radiologist and co-author of this study, JDG, conducted an analysis of the MRI of the anterior horns of the menisci, employing the classification system suggested by Lotysch et al. [8]. This system categorizes the meniscal status as follows: Grade 0 denotes a meniscus without any abnormalities. Grade 1 is indicative of small foci or punctate areas of elevated signal intensity within the substance of the meniscus, which are not in continuity with the joint surface. Grade 2 refers to the presence of linear or horizontal regions of increased signal intensity within the meniscus that do not reach or contact the joint surface. Grade 3 describes a meniscus with regions of increased signal intensity that extend to and involve at least one of the articular surfaces.
All sonographic assessments were performed by XL, a co-author and a seasoned ultrasonographer with a wealth of experience spanning over 18 years in the field of ultrasound diagnostics, encompassing a significant period of more than five years dedicated to musculoskeletal ultrasound examinations. The outcomes of the MRI were disclosed to the investigative team and the study participants solely post the conclusion of the SWE evaluations on the subjects. Prior to this disclosure, the radiologist JDG maintained the confidentiality of the MRI results for all parties involved.
Before the commencement of the SWE procedure, participants were instructed to avoid any form of strenuous exercise affecting the lower limbs, including but not limited to extended periods of running, cycling, and squat exercises, for a two-hour period preceding the examination. They were also asked to rest in a horizontal position for a duration of five minutes before the examination. The individuals were positioned in a supine manner on the diagnostic table, with a circular pillow placed behind the knee area to maintain a slight bend in the knees, typically between 15 to 25 degrees. The examiner initiated a preliminary two-dimensional grayscale scan in muscle and bone mode to capture an optimal coronal view of the anterior horns of both the medial and lateral menisci. Subsequently, the examination protocol transitioned to the "STE elasticity" mode, which was configured to measure within a range of 0-200 kPa, without the application of additional pressure. The visual representation of tissue elasticity was depicted through a color spectrum, with deep blue indicative of the least rigid tissues and deep red signifying the most rigid. A Motion Stability Index (M-STB) rating of 5 stars suggested that the participant's respiratory and positional movements exerted minimal influence on the elasticity measurements, thereby denoting superior motion stability. Moreover, a green quality control chart and a Reliability Index (RLB index) exceeding 98% confirmed the acquisition of high-fidelity shear wave elastography images, which were then suitable for capture and subsequent detailed analysis.
Data collection
We positioned a circular sampling frame with a 2mm diameter at the center of the meniscus as the region of interest (ROI). The numerical values for the following parameters were obtained: the average value (EMean), maximum value (EMax), minimum value (EMin), and standard deviation (ESD) of Young's modulus. In order to minimize measurement errors, we conducted three repeated scans and measurements on each section, recorded the EMean values for the three measurements, and then calculated the average as the final measurement result.
In addition, we also recorded some basic information of each research subject, including gender, age, height, weight, and body mass index (BMI).
Statistical Methods
Statistical analysis was conducted using IBM SPSS 25.0 software. The continuous variables (age, height, weight, BMI, and elasticity values) were reported as mean ± SD. Comparisons between the elastic values of menisci in the same site but with different MRI grades were assessed using one-way analysis of variance (ANOVA) with the least significant difference (LSD) method for post-hoc pairwise comparisons. Independent samples t-tests were used to compare elastic values between different sites with the same MRI grade. Correlation analyses between different parameters were performed using either Pearson's or Spearman's correlation analysis, depending on the nature of the data. The optimal cut-off value for diagnosing meniscal tear was determined by selecting the highest Youden's index, using MRI Grade 3 as the gold standard. Sensitivity, specificity, area under the curve (AUC), and 95% confidence interval (CI) were then calculated. Finally, the intraclass correlation coefficient (ICC) was utilized to assess the reliability of repeated measurements conducted by the same observer. A p-value of less than 0.050 was considered statistically significant.