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Dexa chinmay


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Dexa chinmay

  1. 1. Definition of Osteoporosis “Osteoporosis is a systemic skeletal disease, characterized by low bone mass and micro architectural deterioration of bone tissue with a consequent increase in bone fragility and susceptibility to fracture.”
  2. 2. Etiology  Decreased bone mineral density is a result of a combination of genetic and environmental factors that affect both peak bone mass and the rate of bone loss  These factors include medications, diet, race, sex, lifestyle, and physical activity
  3. 3.  HOW IS BONE DENSITY USEFUL?  Bone Density Is Essential for Diagnosis of     osteoporosis Low bone mass defines osteoporosis We have to measure it for a direct diagnosis of osteoporosis Poor architecture would also suffice for diagnosis but we have no diagnostic tool available to accurately assess it in vivo It is important to look for the etiology of the disease
  4. 4. Frequency  Approximately 10 million people have osteoporosis. Another 14-18 million have osteopenia (low bone mass)  Approximately 1.5 million fractures per year attributed to osteoporosis, and more than 37,000 deaths from subsequent fracture-related complications
  5. 5. So Who Do We Test?
  6. 6. •Postmenopausal women older than 65 years •Postmenopausal women younger than 65 years who have 1 or more risk factor •Postmenopausal women who present with fragility fractures •Women who are considering therapy in which BMD will affect that decision
  7. 7. Women who have been on hormone replacement therapy (HRT) for prolonged periods
  8. 8.  Men who experience fractures after minimal trauma  People with evidence of osteopenia on radiographs or a disease known to place them at risk for osteoporosis
  9. 9. Lab Studies  Levels of serum calcium, phosphate, and alkaline phosphatase are usually normal in persons with primary osteoporosis, although alkaline phosphatase levels may be elevated for several months after a fracture  It is important to also check thyroid function, and testosterone levels in men
  10. 10. Imaging Studies  First, obtain plain radiographs if a decrease in bone mineral density is suspected  Osteopenia may be apparent as radiographic lucency but is not always noticeable until 30% of bone mineral is lost  Plain radiography is not as accurate as BMD testing
  11. 11. BMD Imaging  BMD tests are usually done on bones that are likely to break as a result of osteoporosis like the lower spine and hip  Can also be done on the wrist or heel  Devices that measure BMD include:  Quantitative computed tomography  Dual-energy x-ray absorptiometry (DEXA)  Quantitative ultrasonography  Radiogrammetry
  12. 12. Quantitative Computed Tomography  Quantitative computed tomography measures BMD as a true volume density in g/cm3, which is not influenced by bone size.  This technique can be used for both adults and children.  Disadvantages in that (1) it only determines bone density at the spine, (2) osteophytes can interfere with measurement, and (3) it is associated with significant radiation exposure and high cost
  13. 13. Quantitative Ultrasonography  Quantitative ultrasonography of the calcaneus can be used for general screening  However, this is not as accurate as other methods and thus is less useful in following response to treatment  Its advantages include low cost, portability, and lack of ionizing radiation
  14. 14. Radiogrammetry  Radiogrammetry, used to measure cortical dimensions, is usually performed on the hand, specifically the second metacarpal  It is useful in assessing BMD in children and is the simplest and least expensive method  Disadvantages are that it is not as precise as DEXA and, therefore, is less sensitive for detecting changes over time
  15. 15. DEXA  Dual-energy x-ray absorptiometry requires less radiation, is     less expensive, and has better reproducibility than quantitative computed tomography Can also measure bone density at the spine and the hip. It has become the standard method for determining bone density. This method can be used in both adults and children Confounding factors in DEXA results interpretation (falsely high bone density) include spinal fractures, osteophytosis, and extraspinal (eg, vascular) calcification Peripheral DEXA can be used to measure BMD in the wrist
  16. 16. How DXA Works  DXA uses 2 levels of x-ray photon energy to measure the amount of minerals in bone. The difference in attenuation of the x-rays by bone generates 2-D measurements of bone mineral content in grams and areal BMD. DXA x-rays are produced with a fan beam or a pencil beam. Pencil-beam equipment uses small, angled x-ray beams that move across the patient in a linear direction. The fan-beam generators use a wider beam that reduces scan times but increases radiation dose to patients.
  17. 17. PATIENT PREPARATION  On the day of the exam eat normally. Should not take calcium supplements for     at least 24 hours before your exam. Should wear loose, comfortable clothing, avoiding garments that have zippers, belts or buttons made of metal. Objects such as keys or wallets that would be in the area being scanned should be removed. Should remove some or all of your clothes and to wear a gown during the exam. Remove jewelry, removable dental appliances, eye glasses and any metal objects or clothing that might interfere with the x-ray images. Inform physician if recently had a barium examination or have been injected with a contrast material for a computed tomography (CT) scan or radioisotope scan. If so, may have to wait 10 to 14 days before undergoing a DXA test. Women should always inform their physician and x-ray technologist if there is any possibility that they are pregnant. Many imaging tests are not performed during pregnancy so as not to expose the fetus to radiation. If an x-ray is necessary, precautions will be taken to minimize radiation exposure to the baby.
  18. 18. How does the procedure work?  The DXA machine sends a thin, invisible beam of low- dose x-rays with two distinct energy peaks through the bones being examined. One peak is absorbed mainly by soft tissue and the other by bone. The soft tissue amount can be subtracted from the total and what remains is a patient's bone mineral density.  DXA machines feature special software that compute and display the bone density measurements on a computer monitor
  19. 19. How is the procedure performed?  This examination is usually done on an outpatient basis.  In the Central DXA examination, which measures bone density in the hip and spine, the patient lies on a padded table. An x-ray generator is located below the patient and an imaging device, or detector, is positioned above.  To assess the spine, the patient's legs are supported on a padded box to flatten the pelvis and lower (lumbar) spine. To assess the hip, the patient's foot is placed in a brace that rotates the hip inward. In both cases, the detector is slowly passed over the area, generating images on a computer monitor.  You must hold very still and may be asked to keep from breathing for a few seconds while the x-ray picture is taken to reduce the possibility of a blurred image. The technologist will walk behind a wall or into the next room to activate the x-ray machine.  The peripheral tests are simpler. The finger, hand, forearm or foot is placed in a small device that obtains a bone density reading within a few minutes.  An additional procedure called Lateral Vertebral Assessment (LVA) is now being done at many centers. LVA is a low-dose x-ray examination of the spine to screen for vertebral fractures that is performed on the DXA machine.
  20. 20. SITES
  21. 21. •Clinically most valuable sampling sites –PA Lumbar spine (compression fracture) –Proximal femur (hip fracture) •Use total regions of spine and hip •Use lowest T-score of these two sites •In elderly patient, due to deformity and degenerative changes, difficult to interpret spine scan; then consider hip or forearm
  22. 22. What Are The Results?  Results are reported as two values, T and Z scores  T scores are the number of standard deviations above or below what is normally expected in a healthy young adult of the same sex  Z score is the number of standard deviations above or below what is normally expected for someone of the same age, sex, weight, and ethinic origin
  23. 23. Z Score  The Z score is helpful because it may suggest that the patient may have a secondary form of osteoporosis unrelated to normal aging which is causing decreased BMD  A score less than -1.5 should make you investigate the cause of decreased BMD
  24. 24. Another Report Card  For example, if the T-score is -2.0, the BMD is lower than average by two standard deviations. If the Z-score is -0.5, your bone density is less than the norm for people your age by one-half of a standard deviation
  25. 25. Relation of BMD to Fracture Risk How important is change in BMD with treatment? •In untreated patients, Low BMD=high fracture risk •Treatments for osteoporosis increase BMD & reduce risk •Is the reduction in fracture risk with treatment due to the increase in BMD?
  26. 26. BENEFITS  DXA bone densitometry is a simple, quick and noninvasive procedure.  No anesthesia is required.  The amount of radiation used is extremely small—less than one-tenth     the dose of a standard chest x-ray, and less than a day's exposure to natural radiation. (0.3micro sv) DXA bone density testing is the most accurate method available for the diagnosis of osteoporosis and is also considered an accurate estimator of fracture risk. DXA equipment is widely available making DXA bone densitometry testing convenient for patients and physicians alike. No radiation remains in a patient's body after an x-ray examination. X-rays usually have no side effects in the typical diagnostic range for this exam.
  27. 27. Risks  There is always a slight chance of cancer from excessive exposure to radiation. However, the benefit of an accurate diagnosis far outweighs the risk.  Women should always inform their physician or x-ray technologist if there is any possibility that they are pregnant.  The effective radiation dose for this procedure varies.  No complications are expected with the DXA procedure.
  28. 28. Bone Scans for Osteoporosis: How Often? Bone scan every two years in women with osteoporosis or who are at high risk. Because the response to treatment occurs slowly, this is usually an acceptable time interval. In cases with high bone turnover rates, like women taking high-dose steroids," checking bone density as often as every six months may be necessary,
  29. 29. OTHER USES OF DEXA SCAN A. Total Body BMC versus Age and Total Body BMD     versus Age reference databases. Metabolic bone diseases and conditions. Glucocorticoid-treated patients with congenital adrenal hyperplasia ,total Body BMD Is significantly decreased Postmenopausal women with type 1 diabetes. Total Body BMC and Total Body BMD measurements and z-scores are useful in the management of OI in adults.
  30. 30. Total Body %Fat vs. Age reference databases  Traditional anthropomorphic measures of obesity like BMI and waist circumference quantify excess weight or size, not excess fat, and misclassify patients by failing to assess pathogenic visceral fat depots.  DXA visceral fat measurements may be superior to traditional measures for evaluating obesity-related disease risk.  The available literature supports visceral fat thresholds of 100 cm2 for increased risk and 160cm2 for high risk and suggests this classification scheme may identify patients most likely to benefit from preventive interventions.
  31. 31. What is visceral fat?  Visceral fat occurs within the envelope formed by the abdominal muscles, principally within the greater and lesser omentum that connects the abdominal organs, and in mesenteric fat. A small amount is also found retroperitoneally.  Visceral fat is more dangerous than subcutaneous fat because visceral fat cells release proteins that contribute to inflammation, atherosclerosis, dyslipidemia, and hypertension.  Visceral fat is associated with metabolic risk factors and all-cause mortality in men, and is therefore considered a pathogenic fat depot
  32. 32. Y is visceral fat estimation important  It is important to recognize that even subjects who are normal weight and have a Body Mass Index (BMI) < 25 can have a significant accumulation of visceral fat, increasing their risk for cardiovascular disease, diabetes, and other obesity-related health risks.  Likewise, some overweight or obese patients may have relatively low levels of visceral fat, normal metabolic profiles, and few or no additional risk factors.  A DXA visceral fat measurement may distinguish apparently normal weight subjects with high visceral fat levels and high disease risk from metabolically normal subjects with BMIs in the overweight or obese category.
  33. 33. Computed tomography image of the abdomen at the level of the fourth lumbar vertebrae with visceral cavity outlined in white (right) and visceral fat filled In black on left.
  34. 34. Pediatric DEXA  Discussions regarding bone density typically focus on postmenopausal women, osteoporosis, and fracture risk. Although these are the most common reasons patients have skeletal strength assessments, the use of bone densitometry and bone mineral density measurement in pediatric patients is becoming increasingly valuable to assess children with diseases that cause inadequate bone growth.  Pediatric patients’ bone density most often is measured using DXA and expressed by Z-score, which measures standard deviations from norms for peer based populations.
  35. 35. Abnormal Skeletal Development  Treatmenting adolescents at risk of decreased BMD presents many difficulties for clinicians. Current research indicates that many factors eg, chronic illness, poor diet, illnesses or injuries that cause immobilization, and certain genetic or hormonal disorders, place adolescents at risk for skeletal weakness.
  36. 36. Interpretation of Pediatric Skeletal Measurement  DXA scans are recommended for measurement of BMD in pediatric patients who have a condition that increases risk of skeletal weakness, along with a secondary condition such as recurrent fractures, lowimpact trauma fractures, back pain, spinal deformity, height loss, change in ability to ambulate, or diagnosed malnutrition.
  37. 37. DIAGNOSIS  When a pediatric patient’s measurements are less than 2 standard deviations from the standard mean, the report should indicate that the patient’s skeletal strength is “low for age.” Terminology such as osteopenia and osteoporosis that is used for adult DXA interpretation should not be used in pediatric DXA reports unless certain criteria is met. The ISCD guidelines state that a diagnosis of osteoporosis be made when the a pediatric patient has a DXA diagnosis of “low for age "in addition to a significant fracture history.
  38. 38. Benefits of Pediatric DXA  If the ordering clinician, technologist, and interpreting radiologist ensure that the pediatric DXA examination is performed correctly and provides accurate results, the examination can provide great benefit to the patient. In cases of “low for age” BMD and childhood predictors of adult osteoporosis, there are many interventions available that can improve the patient’s skeletal health and return bone mass to normal levels.  Current recommendations for pediatric patients include appropriate nutrition such as calcium and vitamin D, encouragement of weight-bearing activity, and physical exercise.
  39. 39. Other uses of DEXA!!  %Fat Trunk/%Fat Legs vs. Age and Trunk/Limb Fat Mass Ratio vs. Age reference databases.  Many antiretroviral agents cause a redistribution of fat mass termed lipodystrophy. Lipodystrophy assessment is often made by physical assessment and is passively reported in trials of antiretroviral agents.
  40. 40. CONCLUSION  Although DXA has some limitations, it is currently the recommended method of measurement of BMD and, in conjunction with a detailed clinical assessment, can be used for diagnosis of osteoporosis, in adults as well as in children  It also has a wide avenue to be exploited in other diseases like obesity, lipodystrophy and others.