Osteoporosis is a prevalent condition, particularly among postmenopausal women, but it often goes unnoticed until a fracture occurs. Timely detection of osteoporosis is crucial for preventing osteoporotic fractures. In the United States, the incidence of fractures related to osteoporosis is more than four times higher than that of stroke, heart attack, and breast cancer combined[1]. According to the World Health Organization's meeting report, osteoporotic fractures result in more hospital bed-days than these diseases in several high-income countries[2]. Hip fractures, which are among the most common osteoporotic fractures, can cause difficulties with walking, chronic pain, disability, loss of independence, and reduced quality of life. Shockingly, 21–30% of patients who suffer from hip fractures pass away within one year[3]. Based on 2009 data from Taiwan, approximately 16,000 individuals experience hip fractures annually, with women being twice as likely as men to be affected. Furthermore, the incidence of hip fractures increases significantly with age, with Taiwanese women between the ages of 70 and 80 having a 10% chance of experiencing a hip fracture[4].
Currently, the most reliable method of diagnosing osteoporosis is to measure BMD in the hip and lumbar spine using DXA[5]. According to the guidelines established by the World Health Organization (WHO), a BMD measurement that falls at or below 2.5 standard deviations from the young adult mean (T score ≤ − 2.5) indicates osteoporosis, while a T score ranging between − 1.0 and − 2.5 at any location indicates low bone mass or osteopenia. In addition, the US Preventive Services Task Force recommends BMD testing for women aged 65 and above as a preventive measure against osteoporotic fractures[3]. Despite its effectiveness, DXA has some disadvantages, such as the high cost of equipment and the risk of radiation exposure[6, 7]. Raising awareness about osteoporosis may be the most effective approach to prevent osteoporotic fractures[8]. Unfortunately, elderly individuals have a low level of awareness regarding this disease[9].
A promising strategy for identifying individuals at risk of osteoporosis and fragility fractures is opportunistic screening through imaging methods other than DXA. This approach involves using radiographs that have already been taken for other clinical purposes, with no additional cost, time, or radiation exposure to the patient. For instance, several studies have utilized computed tomography (CT)-based metrics to estimate BMD[10], classify osteoporosis[11], simulate DXA T scores[12], and predict fracture risk[13]. Compared to other imaging modalities, X-ray radiography is more widely available, has broader applications, incurs lower radiation exposure and is generally more cost-effective. Furthermore, radiographs provide excellent spatial resolution, allowing for the visualization of fine bone texture that is closely associated with bone density[14]. This makes it possible to differentiate individuals with osteoporotic fractures from those without. Deep learning algorithms have surpassed traditional methods in terms of visual recognition accuracy[15], which is essential for clinical applications such as fracture detection[16, 17], retinopathy grading[18], and lung nodule identification[19]. Recent advancements in orthopedic research have paved the way for the application of DLMs in osteoporosis screening[20]. Previous studies have shown the feasibility of diagnosing osteoporosis based on radiographs of the lumbar spine and hip joint[21, 22], as well as measuring the BMD (g/cm2) of these sites from radiographs[5, 23]. Furthermore, two studies have utilized chest X-rays for diagnosing osteoporosis[24, 25].
Our hypothesis is that a DLM could accurately predict BMD by analyzing chest radiography. With this in mind, we aimed to develop a DLM that could predict BMD (in g/cm2) and diagnosis based on T scores (normal, osteopenia, and osteoporosis) using chest X-rays, age, and sex. To achieve this, we trained our model using a large dataset gathered from a medical center. Our ultimate goal is to create a model with excellent predictive performance that would allow chest X-rays to be used as a screening tool for osteoporosis.