Background: Magnetic resonance imaging (MRI) allows direct visualization of all tissues of the knee joint, including the articular cartilage with direct evaluation of chondral lesions. Beyond the morphological evaluation, MRI allows to characterize the structural organization (collagen network) and the matrix content of the cartilage. Such a quantitative approach may be performed in clinical practice by T2 mapping technique which can be used as early biomarker for knee osteoarthritis. T2 relaxation time measurements reflect these pathophysiological changes. T2 mapping technique had recently shown its potentiality to evaluate the quality of the cartilage composition since the transversal relaxation time (T2) reflects the ability of proton molecule to move and to exchange energy inside the cartilaginous matrix. Each variation of matrix content (water, proteoglycan and collagen) or each modification of the organization of the collagen network can induce T2 variations.
Objective: The primary purpose of this study was determine whether the addition of a T2 mapping sequence to a routine MR imaging protocol could or could not improve diagnostic performance in the detection of the articular cartilage lesions and early identification of the cartilage degeneration within the knee joint.
Methods: The current study is a cross sectional study that was conducted at private radiology centres in cairo.in the period between September 2019 and December 2020. The study included 20 patients. 13 Males and7 Females with age range from 25 to 65 years (mean age 41.53 years). Complaining from knee pain after direct trauma or twisting. Routine knee MR images from all patients were assessed for gross articular lesion. Then mean T2 values are obtained and the T2 maps are generated and reviewed. Comparative data of the overall Diagnostic indices of conventional MRI and T2 mapping are taken.
Results: The age of the study group ranged from 25 to 65 years (mean age 41.53 years). The male patients represented the majority of our cases. We noted that there was more affection of the left knee compared to the right one with regional differences in the T2 values were observed as higher T2 values in the medial compartments cartilage (weight-bearing) compared to lateral ones cartilage (non-weight-bearing). Cases can be categorized according to the site of pain which was correlated later to the T2 values as: 15% anterior 35% medial, 15% lateral and 35% global. Out of the 20 cases, 12/20 (60 %) cases presented by knee pain following direct trauma, and 8/20 (40 %) cases presented by knee pain following knee twisting. All cases underwent conventional MRI with complementary T2 mapping sequence. In this study, the sensitivity, specificity, and accuracy of the conventional MRI results are 82.3%, 100 %, and 85 %, respectively. While the sensitivity, specificity, and accuracy of the T2 mapping finding results are 100 %, 100 %, and 100 %, respectively.
Conclusion: In this study The addition of a T2 mapping of the knee cartilage sequence to a routine MR knee protocol at 1.5 T improved sensitivity in the detection of cartilage lesions within the knee joint from 82.3 % to 100 %, with improvement of accuracy from 85 % to 100%. The improvement in sensitivity with use of the T2 maps was in the identification of early cartilage degeneration.
Key words: Knee pain, Magnetic resonance imaging, T2 mapping, Cartilage degeneration.