Enhanced acrylic gauge with five eccentric circles for optimizing CT angiography spatial resolution via Taguchi’s methodology

Abstract

BACKGROUND:

Cerebral examination via CTA is always the first choice for patients with unexpected brain injury or different types of brain lesions to detect ruptured hemangiomas, vascular infarcts, or other brain tissue lesions.

OBJECTIVE:

This study innovated the acrylic gauge with five eccentric circles for computed tomography angiography (CTA) analysis to optimize the spatial resolution via Taguchi’s methodology.

METHODS:

The customized gauge was revised from the V-shaped slit gauge and transferred into five eccentric circles’ slit gauge. The gauge was assembled with another six acrylic layers to simulate the human head. Taguchi’s L18 orthogonal array was adopted to optimize the spatial resolution of CTA imaging quality. In doing so, six essential factors of CTA are kVp, mAs, spiral rotation pitch, FOV, rotation time of the CT and reconstruction filter, and each factor has either two or three levels to organize into eighteen combinations to simulate the full factor combination of 486 (21 $\times$ 35 $=$ 486) times according to Taguchi’s recommendation. Three well-trained radiologists ranked the gauge’s 18 CTA scanned imaging qualities according to contrast, sharpness, and spatial resolution and derived the unique fish-bone-plot of six factors for further analysis. The optimal factor combination of CTA was proven by follow-up verification and ANOVA to obtain this study’s dominant or minor factor.

RESULTS:

The optimal factor combination of CTA was A2 (120 kVp), B3 (200 mAs), C1 (Pitch 0.6), D2 (FOV 220 mm2), E1 (rotation time 0.33 s), and F3 (Brain sharp, UC). Furthermore, deriving a quantified MDD (minimum detectable difference) to imply the spatial resolution of CTA, a semiauto profile analysis program run in MATLAB and OriginPro was recommended to evaluate the MDD and to suppress the manual error in calculation. Eventually, the derived MDDs of the conventional and optimal factor combinations of CTA were 2.35 and 2.26 mm, respectively, in this study.

CONCLUSION:

Taguchi’s methodology was found applicable for quantifying the CTA imaging quality in practical applications.