Dexa and its aplication

How we can do dexa scan , its application and interpretation

1. DEXA SCAN and Its Application S a r b a r i S a h a A s s t Professor R a d i o l o gy

2. What is DEXA scan? DUAL ENERGY X-RAY ABSORPTION (DEXA) is a most effective technique used to measure Bone Mineral Density (BMD). It measures the density or thickness of bones and amount of calcium in specific area of bone. Average bone mineral density =BMC/W. Where, BMC = bone mineral content=g/cm. W = width at the scanned line. The more the mineral is bone measured , the less greater is the bone density or bone mass.

3. Various ways to measure BMD DUAL ENERGY X-RAY ABSORPTION (DEXA). PERIPHERAL DUAL ENERGY X-RAY ABSORPTION (P-DEXA). DUAL PHOTON DEXA. QUANTATIVE COMPUTER TOMOGRAPHY(QCT) QUANTATIVE ULTRASOUND.

4. Who should under go Menopausal women, all women above 65 age or older and males over 70 age. Long term steroids , hormonal theraphy , Vit D, Calcium, Low estrogen level. Lumphangiomatosis and low body weight. Kyphosis. Previous history of fracture. Nutritional deficiency- rickets, lupus, Turner syndrome, rheumatoid arthritis.

5. Working Principal Photons are produced from low energy source. 2 X-ray beams with different energy peaks pass through the body. One peak absorbs by the soft tissue and other by the bone. Creates a 2D image. Soft tissue is subtracted from the total area, giving the bone mineral density. These measurements are then measured with the normal ranges matched for chronological age with the help of T-score and Z- Score.

6. C o n t r a i n d i c a t i o n B i l a t e r a l h i p replacement . M e t a l i m p l a n t s in the a r e a . P r e g n a n c y . W e i g h t a b o u t ( 1 2 - 1 3 ) k g . R e c e n t c o n t r a s t studies .

7. R e p o r t F o r m a t

8. T-score T- Score s hows the amount of bone that is compared with a young adult of the same gender with peak bone mass. The T-score is mainly to determine the risk of developing fracture. As per WHO diagnostic classification of osteoporosis 1 A score above -1 is Normal 2 A score between -1 to -2.5 is Osteopenia (low bone mass). 3 A score between -2.5 is defined as Osteoporosis. 4 A score below -2.5 is sever Osteoporosis with history of fragile fracture.

9. Z-score Z - Score shows the amount of bone ,compared with other people in same age group of the same size, height and gender. Z score mainly to determine risk of having a fracture. A low Z-score below – 2 . is a warning sign of low bone mass than expected people of same age of 30-year-old man/woman. Z score = T-score – Reference T- Score.

10. P r o c e d u r e f o r S p i n e

11. P r o c e d u r e f o r H i p

12. Benefits Quick and non invasive procedure. No anaesthesia required. Accurately measures the fracture risk. Less radiation exposure almost 0.001mSv.

13. Prevention To prevent low bone density it is adviced to intake sufficient calcium and vitamin. Regular excersise .

14. D E X A M a c h i n e