Clinical application of radiation dose reduction for head and neck CT.

CT has advantages over MRI including rapid acquisition, and high spatial resolution for detailed anatomical information on the head and neck region. Therefore, CT is the first choice of imaging modality for the larynx, hypopharynx, sinonasal region, and temporal bone. Introduction of multi-detector CT (MDCT) scanning has allowed reduction in scan time, availability of isovoxel image, and relevant 3D image reconstruction; however, it leads to over-ranging due to helical scanning, and increased radiation dose due to 3D-volume imaging, and small detector size. In head and neck CT, reduction and optimization of radiation dose is very important, especially for prevention of the occurrence of cataract development due to radiation to lens, and prevention of the development of malignant tumour development from radiosensitive organs such as the salivary gland, thyroid gland, and retina, especially in children. The goal of dose reduction is "as low as reasonably achievable" (ALARA) level with preservation of appropriate image quality in clinical practice. Reduction of radiation dose per examination is essential; however, indication of repeat examination such as perfusion CT, dynamic contrast-enhanced CT, and follow-up study of malignant tumours should be optimized.