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

Nao Ichikawa; Atsushi Fukuda; Takuma Hayashi; Kosuke Matsubara

doi:10.1002/acm2.13444

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

J Appl Clin Med Phys. 2021 Dec;22(12):177-185. doi: 10.1002/acm2.13444. Epub 2021 Oct 5.

Authors

Nao Ichikawa¹, Atsushi Fukuda², Takuma Hayashi³, Kosuke Matsubara⁴

Affiliations

¹ Faculty of Health Science, Department of Radiological Technology, Kobe Tokiwa University, Hyogo, Japan.
² Department of Radiological Sciences, School of Health Sciences, Fukushima Medical University, Fukushima, Japan.
³ Department of Radiation Oncology, Shiga General Hospital, Shiga, Japan.
⁴ Faculty of Health Sciences, Department of Quantum Medical Technology, Kanazawa University, Ishikawa, Japan.

Abstract

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 $K_{a, i, Q}^{K M}$ 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-cm³ 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 $K_{a, i, Q}^{e x t}$ were simultaneously measured at several X-ray beam qualities with and without EFs. The X-ray beam quality correction factor by KAP meter ( $k_{Q, Q_{0}}^{K M}$ ) was calculated by A, $K_{a, i, Q}^{e x t}$ and KAP reading to acquire the $K A P_{Q}^{K M}$ and $K_{a, i, Q}^{K M}$ . Upon completion of the measurements, $K A P_{Q}^{K M}$ , $K_{a, i, Q}^{K M}$ , and $K_{a, i, Q}^{e x t}$ were plotted as functions of tube potential, spectral filter, and EFs dimension. Moreover, $K_{a, i, Q}^{K M} / K_{a, i, Q}^{e x t}$ values were calculated to evaluate the $K_{a, i, Q}^{K M}$ underestimation.

Results: The $k_{Q, Q_{0}}^{K M}$ values increased with an increase in the X-ray tube potential and spectral filter, and the maximum $k_{Q, Q_{0}}^{K M}$ was 1.18. $K A P_{Q}^{K M}$ and $K_{a, i, Q}^{K M}$ decreased as functions of EFs dimension, whereas $K_{a, i, Q}^{e x t}$ was almost constant. $K_{a, i, Q}^{K M} / K_{a, i, Q}^{e x t}$ 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: $K_{a, i, Q}^{K M}$ value was up to approximately two times lower than the $K_{a, i, Q}^{e x t}$ values by EFs. When using the $K_{a, i, Q}^{K M}$ value, the potential $K_{a, i, Q}^{K M}$ underestimation with EFs should be considered.

Keywords: equalization filter; kerma-area product meter; measurement accuracy; percutaneous coronary intervention.

MeSH terms

Angiography*
Calibration
Fluoroscopy
Humans
Radiation Dosage
Radiography