80-kV p hepatic CT to reduce contrast medium dose in azotemic patients: a feasibility study

Abstract

Background

Low peak kilovoltage (kV_p) computed tomography (CT) may be used to reduce contrast medium doses in patients at risk of contrast medium-induced acute kidney injury if image noise can be controlled by increasing X-ray tube loading (mAs).

Purpose

To evaluate objective and subjective image quality in 80-kV_p CT with reduced contrast medium dose and compensated mAs for unchanged image noise in patients with estimated glomerular filtration rate <45 mL/min compared with the standard 120-kV_p protocol.

Material and Methods

80-kV_p CT with 300 mg I/kg in 40 patients (body mass index 18–32 kg/m², glomerular filtration rate <45 mL/min) and 120-kV_p CT with 500 mg I/kg in 40 patients (body mass index = 17–30 kg/m², glomerular filtration rate ≥45 mL/min) was compared on mean hepatic attenuation, image noise, contrast medium enhancement, signal-to-noise ratio, contrast-to-noise ratio, effective radiation dose, and subjective image quality.

Results

There were no significant differences regarding median hepatic post-contrast attenuation, image noise, contrast medium enhancement, signal-to-noise ratio, contrast-to-noise ratio, or effective dose between the 80-kV_p and 120-kV_p cohorts: 114/110 HU; 14/14 HU; 57/53 HU; 8.0/7.4; 3.8/3.5; and 5.3/5.9 mSv, respectively. However, subjective image visual grading showed statistically significantly inferior scores for 80 kV_p for six of eight items. After exclusion of seven inferior examinations not caused by the chosen kV_p technique, only three items showed inferior scores for 80 kV_p. Only 5% of gradings regarding overall image quality were <3 of 5 points.

Conclusion

Despite lower subjective image quality, objective data indicate that 80-kV_p CT with reduced contrast medium doses and compensated mAs may have the potential to provide satisfactory diagnostic quality in patients with body mass index <30 kg/m², which could benefit patients at risk of contrast medium-induced acute kidney injury.

Keywords

Computed tomography contrast media acute kidney injury liver filtered back-projection image noise low tube voltage

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