Dual ENergy CT Flashcards
what is CT number dependent on
it is dependent on xray attenuation. Physical density and atomic number
what is slow kv switching
it is consecultive slow KV scans. It is interscan delay= scan time+table move time. The strenth is no special hardware, but the weakeness is problem with motion misregistration
what is fast KVp switching
tube potential switched between successive views. the strenth is near simulatenous data scquisition full field of view. Weakness spectral overlap and no automatic exposure control
what is a dual layer sanwich detectors
it has two scintillators and it has one that has low energy data and read out high energy data. The strengths are simultaneous data acquisition and full field of view and automatic exposure control. Weakness is spectral overlap
what is dual source
two tubes/two generators and 90 degrees apart and rotate together, allow simulatenous collection data at two kVps. strength is each tube can have optimal mA and filtration, AEC, realtively small spectral overlap, and multiple kV selections. Weakness is that msaller field of view for DDE post processing. Cross scatter
what is using twin beam and special filters
au is kedge and low energy beam. It Sn high energy beam. Strength is relatively low requirement hardware, full field of view and AEC. Weakness is spectral overlap and limited to 120 kv
what are photon counting detectors
it is two or more energy levels, and signals are binned according to energy level, but it is not actually used on commercial basis
what are dual energy CT images
it can be low and high energy images, blended image (combine low and high energy images together), material selective image, energy selective image (monochromatic image)
what is material differentiation
it is two types of differnet materials, can look at renal stones, differentiate uric acid stone adn non unic acid stone. It is patient treatment overall is the idea. It can also be used for gout or bone after material changes
what is used for material decomposition on dual CT
it is projection based algorithm. and can tell if it is mixed or not
what is the image based algorithm
it is any materials mass attentuation coefficient can be expressed as a linear combination of the coefficients of two so caled basis materials. MEasure the image onject at two differnt x-ray spectra. REconstruct images at each energy, and solv the equations for the density of each material
DE algorithms if they are project based what does that mean
no beam hardening effect in theory, and requires data consistency between low/high energy projections
what are the DE algorithms for image based what does that mean
easy to implement, no data consistency problem as in projection based algoirthm. beam hardening effect cant be totally removed in theory but in practice it is reasonable well corrected for
energy seletice images
multiplying the concentration of each base material and iodine and water have attenutations at differnt KV
what does monoenergetic help with
it is metal artifact reduction
