Abstract
PURPOSE: This study aimed to evaluate the effect of equalization filters (EFs) on the kerma-area product ( KAPQKM ) and incident air-kerma ( Ka,i,QKM ) using a kerma-area product (KAP) meter. In addition, potential underestimations of the Ka,i,QKM values by EFs were identified. MATERIALS AND METHODS: A portable flat-panel detector (FPD) was placed to measure the X-ray beam area (A) and EFs dimension at patient entrance reference point (PERP). Afterward, a 6-cm(3) external ionization chamber was placed to measure incident air-kerma ( Ka,i,Qext ) at PERP instead of the portable FPD. KAP reading and Ka,i,Qext were simultaneously measured at several X-ray beam qualities with and without EFs. The X-ray beam quality correction factor by KAP meter ( kQ,Q0KM ) was calculated by A, Ka,i,Qext and KAP reading to acquire the KAPQKM and Ka,i,QKM . Upon completion of the measurements, KAPQKM , Ka,i,QKM , and Ka,i,Qext were plotted as functions of tube potential, spectral filter, and EFs dimension. Moreover, Ka,i,QKM/Ka,i,Qext values were calculated to evaluate the Ka,i,QKM underestimation. RESULTS: The kQ,Q0KM values increased with an increase in the X-ray tube potential and spectral filter, and the maximum kQ,Q0KM was 1.18. KAPQKM and Ka,i,QKM decreased as functions of EFs dimension, whereas Ka,i,Qext was almost constant. Ka,i,QKM/Ka,i,Qext decreased with an increase in EFs dimension but increased with an increase in tube potential and spectral filter, and the range was 0.55-1.01. CONCLUSIONS: Ka,i,QKM value was up to approximately two times lower than the Ka,i,Qext values by EFs. When using the Ka,i,QKM value, the potential Ka,i,QKM underestimation with EFs should be considered.