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 (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.

Automated summary

This study evaluated the effect of equalization filters (EFs) on kerma-area product (KAPQKM) and incident air-kerma (Ka,i,QKM) using a KAP meter. The results showed that there was a potential underestimation of Ka,i,QKM values by EFs, with kQ,Q0KM values increasing with tube potential and spectral filter. Additionally, Ka,i,QKM was found to be up to approximately two times lower than Ka,i,Qext values by EFs.