Evaluation of Radiation Dose and Image Quality using High-Pitch 70-kV Chest CT in Immunosuppressed Patients

Abstract

Purpose: The aim of the study was to evaluate high-pitch 70-kV CT examinations of the thorax in immunosuppressed patients regarding radiation dose and image quality in comparison with 120-kV acquisition. Materials and Methods?The image data from 40 patients (14 women and 26 men; mean age: 40.9±15.4 years) who received high-pitch 70-kV CT chest examinations were retrospectively included in this study. A control group (n=40), matched by age, gender, BMI, and clinical inclusion criteria, had undergone standard 120-kV chest CT imaging. All CT scans were performed on a third-generation dual-source CT unit. For an evaluation of the radiation dose, the CT dose index (CTDIvol), dose-length product (DLP), effective dose (ED), and size-specific dose estimates (SSDE) were analyzed in each group.The objective image quality was evaluated using signal-to-noise (SNR) and contrast-to-noise ratios (CNR). Three blinded and independent radiologists evaluated subjective image quality and diagnostic confidence using 5-point Likert scales. Results?The mean dose parameters were significantly lower for high-pitch 70-kV CT examinations (CTDIvol, 2.9±0.9 mGy; DLP, 99.9±31.0 mGyxcm; ED, 1.5±0.6 mSv; SSDE, 3.8±1.2mGy) compared to standard 120-kV CT imaging (CTDIvol, 8.8±3.7mGy; DLP, 296.6±119.3 mGyxcm; ED, 4.4±2.1 mSv; SSDE, 11.6±4.4mGy) (P≤0.001). The objective image parameters (SNR: 7.8±2.1 vs. 8.4±1.8; CNR: 7.7±2.4 vs. 8.3±2.8) (P≥0.065) and the cumulative subjective image quality (4.5±0.4 vs. 4.7±0.3) (p=0.052) showed no significant differences between the two protocols. Conclusion?High-pitch 70-kV thoracic CT examinations in immunosuppressed patients resulted in a significantly reduced radiation exposure compared to standard 120-kV CT acquisition without a decrease in image quality. Key Points:? Third-generation dual-source CT units enable high-pitch 70-kV CT examinations of the chest. High-pitch 70-kV CT examinations show a significantly reduced radiation dose compared to standard 120-kV CT examinations. High-pitch 70-kV CT examinations of the chest show comparable objective and subjective image quality. Subjectively deteriorated image noise and sharpness of 70-kV CT did not impact diagnostic confidence. Citation Format Yel I, Martin SS, Wichmann JL etal. Evaluation of Radiation Dose and Image Quality using High-Pitch 70-kV Chest CT in Immunosuppressed Patients. Fortschr Röntgenstr 2019; 191: 122-129.