EFFECTS OF X-RAY TUBE-VOLTAGE RIPPLE AND CURRENT-MODE ON PATIENT DOSE

This paper proposes a radiographic sensitivity attenuation curve for s creen-films systems. This curve expresses the relative inverse value o f mAs value needed to give the same photographic density. This curve d ecreases more slowly with increasing object thickness than the exposur e attenuation curve generally used hitherto. By using the radiographic sensitivity attenuation curve and the exposure attenuation curve, the voltage-ripple dependence of mAs values and patient dose for the same photographic density was obtained. As predicted theoretically in a pr evious paper [Med. Phys. 18, 921 (1991)], it was verified quantitative ly the reverse order that larger ripple values resulted in lower patie nt dose and lower mAs value for the unsaturating current mode at large ripple. This reverse order clearly appeared in two-pulse units. These phenomena were experimentally verified. As a result it was found that in radiographing with a two-pulse unit, larger mA value results in lo wer patient dose.