Correlation of Cross-Sectional Diameter With Image Quality and Radiation Exposure in MDCT Examinations of the Neck

OBJECTIVE. The purpose of this study was to identify an optimal cross-sectional neck diameter that correlates with image quality and radiation exposure in MDCT examinations of the neck performed with automatic tube current modulation. MATERIALS AND METHODS. Ninety-six adults underwent 64-MDCT of the neck with automatic tube current modulation at the same noise setting. On frontal and lateral scout images, maximal body diameters were measured in the transverse and anteroposterior planes at two levels: just below the mandible (upper neck) and at the lung apex (lower neck). Neck diameters were correlated with image quality on a subjective 4-point scale and with radiation exposure (volume CT dose index). RESULTS. As continuous variables, both anteroposterior and transverse diameters in the lower neck were associated with image quality (p ≤ 0.0012). Diameters in the upper neck were not associated with image quality. When diameters in the lower neck were categorized into small, medium, and large, image quality ...