Dr Gita Devi & Dr Ankit Prabhakar
A DEXA scanner is an X-ray source machine with lower radiation exposure (0.001 to 0.005 mSv) comparable to the amount of natural background radiation a person is exposed to in everyday life. It is a gold standard tool for bone mineral density (BMD) calculation for the diagnosis of osteoporosis and fracture risk assessment. It is a cost-effective and relatively easily available imaging investigation.BMD is calculated as score. Classification of BMD according to T-scorevalue: Normal: greater than -1.0, Osteopenia: -1.0 to -2.5, Osteoporosis: less than -2.5, Severe or established osteoporosis: less than -2.5 plus history of fragility fractures.
WHO SHOULD UNDERGO A DEXA SCAN, AND WHEN?
To diagnose osteoporosisin:
Females 65 years or older and males 70 years or older-for asymptomatic osteoporosis
For females younger than 65 years if they are at risk for osteoporosis,e.g patients on oestrogen therapy, or with history of maternal hip fracture beyond 60 years, or those with low body mass (BMI <18.5 kg/m2) or with history of amenorrhea for 1 year or more before 42 years of age. Male or female younger than 65 years/70 years, respectively, with the risk factors like current cigarette smoker or loss of height or thoracic kyphosis Other group of the population for screening for osteoporosis at any age with osteopenia or fragility fracture on imaging studies, 50 years or older individuals developing fracture (of hip, spine, wrist or proximal humerus) with trivial trauma/no trauma, individuals expected to receive or are receiving glucocorticoid therapy equivalent to 5mg or more of prednisolone daily for 3 or more consecutive months, candidates planning to begin medication for osteoporosis, adult males (18 years or above) with hypogonadism or those who have been castrated due to surgery or chemotherapy, candidates receiving radiation or chemotherapy for malignancies, patients with bone dysplasias such as osteogenesis imperfecta, osteopetrosis. Systemic conditions like chronic renal failure, arthritis, eating disorders, organ transplantation, prolonged immobilization, gastric bypass surgery for obesity, malnutrition, inflammatory bowel disease, malnutrition, chronic alcoholism, osteopenia, Vit D deficiency, multiple myeloma, cirrhosis, and chronic illnesses.Patients on some drugse.g., anticonvulsants, chronic heparin.Patients with some diseases -e.g., Hypo and hyperparathyroidism, Cushing syndrome To monitor changes in bone mineral density after treatment or exercise. To estimate fracture risk-e.gIn postmenopausal women or chronic conditions like arthritis or post treatment assessment, hypogonadism, menopause before 45 years, significant weight loss or low BMI. FRAXis a fracture risk assessment tool that guidesto start the treatment if the 10-year fracture risk is > 20% for major osteoporotic fractures and > 3% for hip fractures, based on the FRAX calculation.
Monitoring bone health over time. e.g., in patients already diagnosed with osteoporosis or osteopenia-Usually repeated every 1-2 years.People on osteoporosis treatment or discontinued treatment.
SITUATIONS WHERE A DEXA SCAN SHOULD BE AVOIDED
Recently administered oral contrast agents for imaging or radionuclides (DEXA should be done after 2 weeks of intake of oral contrast agents), pregnancy, scoliosis, severe degenerative disease, implants, hardware, devices, and foreign materials in the areas of scan, extremes of high or low body mass index(BMI).
DO’s IN DEXA SCANNING
Patient history & examination is important prior to DEXA scan. E.g., history of previous surgery, implants, systemic diseases, etc.Patient has to remove all metal items, such as jewellery, watches, and belts, as these can interfere with the scan. The patient should wear loose-fitting clothing without metal zippers or buttons, or they may be asked to change into a hospital gown.For whole body DEXA/Body composition studies patient is scanned in the morning after a 12-hour overnight fasting.
DON’TS IN DEXA SCANNING
Do not take calcium tablets within 24 hours before examinations.Do not move during the DEXA scan
Don’t undergo a DEXA scan soon after a barium study, nuclear medicine scan, or contrast CT within the past 1-2 weeks, as contrast can interfere with the BMD measurements.Avoid DEXA scan during pregnancy.
POSITIONING FOR DEXA EXAMINATION
Image showing positioning in distal forearm, whole body, lumbar spine, and hip for DEXA scan
VERTEBRAL FRACTURE ASSESSMENT (VFA)-VFA is a special feature available in some DEXA machines. It helps detect morphological changes in vertebral bodies that indicate compression fractures, which are often asymptomatic but clinically significant. Even a single vertebral fracture significantly increases the risk of future fractures, including hip fractures. Early identification can lead to earlier treatment and fracture prevention.
WHEN SHOULD ONE UNDERGO A DEXA SCAN FOR VERTIBRAL FRACTURE ASSESSMENT
If BMD shows osteopenia or low bone mass (T-score ? -1.5, some literature shows ? – 1 ), and the patient has: age ? 70 (women), ? 80 (men), height loss > 4 cm (1.5 inches), recent or past fractures, long-term steroid use, history of falls, back pain suggestive of vertebral compression. Postmenopausal women ? 65 years, even without symptoms, they are at higher risk of silent vertebral fractures.Men ? 70 years, especially if they have osteoporosis risk factors or past fractures.Fragility fracture at Other Sites. A history of hip, wrist, or other low-trauma fractures raises suspicion for silent spine fractures.Glucocorticoid therapy.
WHOLE BODY DEXA: It is performed for -Post-weight loss monitoring (To check how much fat and muscle a person has after they’ve lost 10% or more of their body weight through a diet, medication, or weight loss surgery), sarcopenia risk assessment (to measure appendicular lean mass in patients showing signs of reduced muscle strength or poor physical performance, or those at risk for sarcopenia), fat distribution in HIV patients (to assess body fat changes in HIV-infected individuals on antiretroviral therapy, especially those receiving zidovudine or stavudine, due to the risk of lipodystrophy), nutritional and athletic evaluation, tracking changes resulting from weight loss interventions like diet, exercise, or pharmacological treatments.
DEXA scan is now available at AIIMS Jammu and AIIMS Jammu has been performing DEXA scans since its inception, offering state-of-the-art bone densitometry services to patients across the region. This non-invasive and painless procedure helps in the early diagnosis of osteoporosis. With highly trained radiology staff and advanced equipment, the institute ensures accurate and timely reports to support clinical decisions. The availability of DEXA scanning at AIIMS Jammu reflects its commitment to providing comprehensive diagnostic care to the community.
(The writers are Assistant Professors in the Department of Radiodiagnosis, AIIMS Jammu)
