Individually adapted kilovoltage for oncologic chest CT: Levels of radiation dose in clinical practice

Abstract

Purpose: The main purpose of this study was to verify the adequacy of dose levels of irradiation in oncologic chest CT obtained in our daily practice with the recommendations of the existing referral guidelines. The secondary objective was to evaluate the effect on radiation dose of individual adjustment of kilovoltage in thoracic multidetector row computed tomography (MDCT) images acquired with single and dual-source technology. The impact of lowering the kilovoltage in the diagnostic quality of these studies was also evaluated.

Methods: Ninety-seven patients were included in the study. CT examinations were performed using two different equipments: a conventional CT scanner (SOMATOM Emotion 6), and a dual-source computed tomography (DSCT) system (SOMATOM Force), (Siemens Medical System, Forchheim, Germany), with the following parameters. Emotion 6: collimation 6 × 1.0, slice thickness 1.25 mm, 110/130 kV, 48-107 mAs. FORCE: collimation 64 × 0.6, slice thickness 1 mm, 100-150 kV, 65-300 mAs. Dose levels of the CT scans were recorded digitally. The levels of DLP (Dose Length Product) obtained, as well as the existing noise in the acquired images, was evaluated.

Results: The average DLP of the protocols was as follows. Emotion 6, 130 kV: 336.3 mGy (5.72 mSv). Emotion 6, 110 kV: 209 mGy (3.55 mSv). FORCE, 150 kV: 183.3 mGy (3.11 mSv). FORCE, 100 kV: 49.4 mGy (0.84 mSv). The values of effective dose were obtained using the conversion factor described by the European Guidelines for Computed Tomography for chest CT (0.017 mSv/mGy/cm). The levels of noise did not rise significantly in the lower kV group.

Conclusions: The average values of DLP obtained in our daily practice meet the recommendations of the existing referral guidelines. Lower values can be achieved through individual adjustment of kilovoltage and using CT scanners with dual-source technology, maintaining the diagnostic quality of these studies.