DEXA Flashcards
what is the main use of DEXA
to measure bone mineral density (BMD)
what does DEXA detect
osteoporosis from the lumbar spine, femoral neck and distal forearm.
what can DEXA measure in areas that do not contain bone
lipid and lean muscle mass
what does DEXA produce
planar image of relevant bones
what does the gantry configuration consist of?
a pencil beam system
pinhole source collimator
single detector
what is used nowadays instead of the pencil beam
a fan beam
what are the two techniques used to produce the dual beam energies
voltage switching
k-edge filter system
what is the k-edge filter system
the x-ray tube is operated at a steady voltage and a K absorption edge filter splits a single x-ray spectrum into low and high energy components
what is voltage switching
x-ray tube switches between 70 and 140 kVp during alternate half cycles of the power supply
what filters are used in DEXA
copper and brass filters are used to remove low energy x-rays
what must be done to DEXA machine before use
the DEXA machine must be callibrated using a phantom suitable for a particular examination for example, spine.
what is the T score
the T score compares a person’s bone density with that of a healthy 30-year-old of the same sex
what is the z-score
the z-score is a comparison of a person’s bone density with that of an average person of the same age and sex
what is used as the primary diagnostic value for osteoporosis
the T score
the T-score is ____ _____ to fracture risk
the T-score is inversely proportional to fracture risk
