Image quality and radiation dose of dual-energy CT of the head and neck compared with a standard 120-kVp acquisition

Abstract

Background and purpose: DECT offers additional image datasets with potential benefits, but its use for H&N imaging is not justified unless image quality is preserved without increased radiation dose. The aim of this work was to compare image quality and radiation dose between a DE-derived WA image dataset and a standard SECT acquisition of the H&N.

Materials and methods: Thirty-two patients underwent DECT of the H&N (tube voltages 80 and Sn140 kVp) and were compared with the last 32 patients who underwent standard SECT (120 kVp) on the same dual-source scanner. WA images from the 2 DE tubes were compared with images obtained with an SE mode. Radiation doses and attenuation measurements of the internal jugular vein, submandibular gland, and sternomastoid and tongue muscles were compared. Objective image noise was compared at 5 anatomic levels. Two blinded readers compared subjective image quality by using 5-point grading scales.

Results: CTDI(vol) was 12% lower with DE than with SECT, a difference of 1.5 mGy, (P < .0001). Objective noise was not significantly different between DE and SECT at any of the anatomic levels (P > .05). No significant differences in attenuation measurements were observed between DE and SECT (P > .05). No significant differences in subjective image quality scores were observed between DE and SECT at any of the 5 anatomic levels (P > .05).

Conclusions: DE-derived WA images of the H&N are equivalent to standard SE acquisitions and thus can be used for routine diagnostic purposes. Multiple additional image datasets can be obtained with no radiation dose penalty.

Fig 1.

Axial contrast-enhanced CT images obtained through the level of the floor of the mouth in 2 different patients. DE-derived WA image (A) and standard SE (120 kVp) image (B). Mean attenuation values (in Hounsfield units) of the sternomastoid muscle, tongue muscle, and internal jugular vein were obtained at this level by using circular regions of interest, as shown. Objective noise was obtained as the SD of the circular regions of interest drawn in air outside the patient. Noise was obtained in all anatomic levels in a similar way.

Fig 2.

Box-and-whisker plot of attenuation measurements with DE and SECT. Boxes represent the middle 50% of cases, horizontal lines within mark median values, and whiskers represent minimal and maximal extremes. Differences between attenuation values with DECT and SECT are nonsignificant (P > .05).

Fig 3.

Axial contrast-enhanced CT images through the nasopharynx (A and B), arytenoids (C and D), lower thyroid (E and F), and arch-of-the-aorta (G and H) levels in different patients. On the left panel are DE-derived WA images (A, C, E, G) and on the right panel are images acquired in single energy mode (B, D, F, H). There is no perceivable difference in image noise, sharpness, or overall image quality. All images are of excellent diagnostic quality.