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Describe 3 factors that can be altered during fluoroscopy image acquisition that can improve the CNR.
Increasing CNR can be done by:
- Just increasing mAs with the same kVp – increases the number of photons in total which will reduce quantum mottle and hence noise as both mA and s (time) are linearly related to the number of photons. (if we increase the dose by N times, then the noise decreases by square root N times)
- Pixel binning dels together during x-ray to have more photons per del and hence reduce noise. Combing 2×2 pixels to one will increase photon number by 4x to the del and hence will improve CNR by 2x (however resolution will reduce).
- LOWERING the kVp (tube potential) whilst also increasing mAs to compensate- to have the same number of incident photons total will increase contrast as there is more photoelectric effect and less Compton scatter