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

Purpose This study aimed to evaluate the effect of equalization filters (EFs) on the kerma‐area product ( K A P Q K M) and incident air‐kerma ( K a , i , Q K M ) using a kerma‐area product (KAP) meter. In addition, potential underestimations of the K a , i , Q K Mvalues 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 ( K a , i , Q e x t ) at PERP instead of the portable FPD. KAP reading and K a , i , Q e x twere simultaneously measured at several X‐ray beam qualities with and without EFs. The X‐ray beam quality correction factor by KAP meter ( k Q , Q 0K M ) was calculated by A , K a , i , Q e x tand KAP reading to acquire the K A P Q K Mand K a , i , Q K M . Upon completion of the measurements, K A P Q K M, K a , i , Q K M , and K a , i , Q e x twere plotted as functions of tube potential, spectral filter, and EFs dimension. Moreover,K a , i , Q K M / K a , i , Q e x tvalues were calculated to evaluate the K a , i , Q K Munderestimation. Results The k Q , Q 0K Mvalues increased with an increase in the X‐ray tube potential and spectral filter, and the maximum k Q , Q 0K Mwas 1.18. K A P Q K Mand K a , i , Q K Mdecreased as functions of EFs dimension, whereas K a , i , Q e x twas almost constant.K a , i , Q K M / K a , i , Q e x tdecreased 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. ConclusionsK a , i , Q K Mvalue was up to approximately two times lower than the K a , i , Q e x tvalues by EFs. When using the K a , i , Q K Mvalue, the potential K a , i , Q K Munderestimation with EFs should be considered.