Role of Lumbar Spine Signal Intensity Measurement by MRI in the Diagnosis of Osteoporosis in Postmenopausal Women

Background: Osteoporosis is a common metabolic bone disease characterized by reduced bone mineral density (BMD) and deterioration of bone microarchitecture, leading to an increased risk of fractures, particularly in postmenopausal women. Dual-energy X-ray absorptiometry (DEXA) is considered the gold standard for diagnosing osteoporosis; however, Magnetic Resonance Imaging (MRI) has shown potential for opportunistic screening by evaluating bone marrow signal intensity changes associated with bone loss. This study aimed to assess the role of lumbar spine signal intensity measurement by MRI in the diagnosis of osteoporosis in postmenopausal women. Methods: A cross-sectional study was conducted at North West Hospital, Peshawar over a period of six months (from May 2025 to October, 2025). A total of 97 postmenopausal women aged 50 years and above were included using a convenience sampling technique. All participants underwent DEXA scanning to determine bone mineral density and lumbar spine MRI using a 1.5 Tesla scanner. Signal intensity of vertebral bodies (L1–L4) was measured and signal-to-noise ratio (SNR) and MRI-based diagnostic score (M-score) were calculated. MRI findings were compared with DEXA results. Data were analyzed using SPSS version 26. Diagnostic performance of MRI was evaluated using sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and ROC curve analysis. Results: According to DEXA results, 25.8% of participants had normal bone density, 41.2% had osteopenia, 25.8% had osteoporosis, and 7.2% had severe osteoporosis. MRI evaluation showed that 41.2% had a normal marrow pattern, while 46.4% demonstrated increased fat signal intensity. The mean BMD was 0.95 ± 0.12 g/cm² and the mean T-score was −1.2 ± 1.1. MRI-based classification showed 30.9% normal cases, 41.2% suggestive of osteopenia, and 27.8% suggestive of osteoporosis. Logistic regression analysis revealed that physical activity was significantly associated with reduced odds of osteoporosis (OR = 0.38, p = 0.008), while history of fracture significantly increased the odds (OR = 2.45, p = 0.006). Other factors such as age, BMI, hormone replacement therapy use, smoking, alcohol consumption, diabetes, and thyroid disorders were not significantly associated. Conclusion: Lumbar spine MRI signal intensity measurements show potential as a supportive diagnostic tool for identifying osteoporosis in postmenopausal women. MRI may serve as a useful opportunistic screening method during routine spinal imaging, particularly in settings where DEXA is not readily available.