Wryneck position CT scanning

For the purpose of further improvement in the CT diagnosis of skull-base and posterior fossa lesions, wryneck position CT scanning was investigated. By the lateral tilting of the patient's head, phantom and clinical study revealed that high- or low-density artifacts between petrous bones were markedly reduced using various types of CT scanners. The most appropriate angle of the lateral head tilting was assumed to be 50 - 100, and better scans were given when the scan was done parallel to Reid's baseline. A satisfactory efficacy of this method was noted in such clinical cases as trigeminal neurinoma, c-p angle meningioma, and pontine glioma. Interpetrous artifacts are caused by the beam hardening and scattering of X-rays, afterglow and crosstalk of the detectors, mastoid air cells, movements of the patients, computer overswing, and the partial-volume phenomenon. The wryneck position can reduce these artifacts by eliminating one petrous bone from the scan area. In addition, the orbit, calvarium, and tip of the middle fossa can be visualized more clearly by this method. This method is very simple and useful for use with head scanners and non-gantlytiltig body scanners which can not easily be used for coronal scans. The better visualization of the anatomical structures in the skull base and posterior fossa by wryneck-position CT scanning gives greater diagnostic ability in these areas. (author)