Effect of equalization filters on measurements with kerma-area product meter in a cardiovascular angiography system

This study aimed to evaluate the effect of equalization filters (EFs) on the kerma-area product ( $$ ) and incident air-kerma ( $$ ) using a kerma-area product (KAP) meter. In addition, potential underestimations of the $$ values by EFs were identified.

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-cm³ external ionization chamber was placed to measure incident air-kerma ( $$ ) at PERP instead of the portable FPD. KAP reading and $$ were simultaneously measured at several X-ray beam qualities with and without EFs. The X-ray beam quality correction factor by KAP meter ( $$ ) was calculated by A, $$ and KAP reading to acquire the $$ and $$ . Upon completion of the measurements, $$ , $$ , and $$ were plotted as functions of tube potential, spectral filter, and EFs dimension. Moreover, $$ values were calculated to evaluate the $$ underestimation.

The $$ values increased with an increase in the X-ray tube potential and spectral filter, and the maximum $$ was 1.18. $$ and $$ decreased as functions of EFs dimension, whereas $$ was almost constant. $$ 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.

$$ value was up to approximately two times lower than the $$ values by EFs. When using the $$ value, the potential $$ underestimation with EFs should be considered.