Infographics / X-ray Physics

Effect of tube kV (high-kV technique)

A comparison table contrasting low-kVp and high-kVp technique. Low kVp gives a less penetrating beam, photoelectric-dominant attenuation, higher subject contrast (short grey scale), less scatter, but needs higher mAs, longer exposure time, higher tube heat loading and higher patient dose. High kVp gives a more penetrating beam, Compton-dominant attenuation, lower subject contrast (long grey scale) and more scatter, but allows lower mAs (15 percent rule), shorter exposure time, lower tube loading and lower patient dose. A footnote notes the classic use in high-kVp chest radiography.

Low kVp versus high kVp radiographic technique A comparison table contrasting low-kVp and high-kVp technique. Low kVp gives a less penetrating beam, photoelectric-dominant attenuation, higher subject contrast (short grey scale), less scatter, but needs higher mAs, longer exposure time, higher tube heat loading and higher patient dose. High kVp gives a more penetrating beam, Compton-dominant attenuation, lower subject contrast (long grey scale) and more scatter, but allows lower mAs (15 percent rule), shorter exposure time, lower tube loading and lower patient dose. A footnote notes the classic use in high-kVp chest radiography. Low kVp vs high kVp radiographic technique — same image receptor exposure Property Low kVp High kVp Beam penetration less penetrating more penetrating Dominant interaction photoelectric (∝ Z³/E³) Compton scatter Subject contrast higher — short grey scale lower — long grey scale Scatter-to-primary ratio lower higher mAs needed higher lower (15% rule) Exposure time longer shorter — less motion blur Tube heat loading higher lower Patient / skin dose higher lower Classic use — high-kVp chest radiography Penetrates the mediastinum and suppresses high-contrast rib shadows, revealing lung detail; often paired with an air gap to limit scatter reaching the detector.
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