Head and neck effective dose and quantitative assessment of image quality: a study to compare cone beam CT and multislice spiral CT.

OBJECTIVES

To evaluate the effective dose and image quality of horizontal CBCT in comparison with multislice spiral CT (MSCT) in scans of the head, cervical spine, ear and dental arches.

METHODS

A head and neck Alderson-Rando phantom (The Phantom Laboratory, Salem, NY) equipped with 74 thermoluminescence dosemeters was exposed according to 5 different scans in CBCT and 4 different scans in MSCT. Spatial and contrast resolutions, in terms of modulation transfer function and contrast-to-noise ratio (CNR), were measured to obtain a quantitative assessment of image quality.

RESULTS

The CBCT effective dose was 248, 249, 361, 565 and 688 µSv in the cervical spine, head, ear, dental arches with small field of view and dental arches with medium field of view, respectively. The MSCT effective dose was 3409, 1892, 660 and 812 µSv in the cervical spine, head, ear and dental arches, respectively. The modulation transfer function was 0.895 vs 0.347, 0.895 vs 0.275, 0.875 vs 0.342 and 0.961 vs 0.352 for CBCT vs MSCT in the cervical spine, head, ear and dental arches, respectively. Head and cervical spine MSCT showed greater CNR than CBCT, whereas CNR of the ear and dental arches showed comparable values.

CONCLUSIONS

CBCT was preferable to MSCT for the ear and dental arches volumetric imaging due to its lower radiation dose and significantly higher spatial resolution. In the case of cervical spine and head imaging, MSCT should be generally recommended if a high contrast resolution is required, despite the greater radiation exposure.