title: [CT scanners with automatic focus alteration capability].
abstract: Heat accumulation in X-ray tubes results in disarrangement of focus owing to heat expansion of the anode. CT scanners with automatic focus alteration capability have been developed to counteract this problem. We compared CT scanners with and without focus alteration capabilities and discuss the effect of focus disarrangement on the CT images. Images were obtained when heat accumulation was high and low. Subtraction images were made to define the disarrangement of focus. A comparison was made between CT scanners with and without automatic focus alteration capability. ROI was selected and changes in CT values, SD, and slice thickness were observed under changing anode heat accumulation. Results indicated that images from both scanners showed disarrangement of the focus and elevation of CT values as anode heat accumulated. However, the scanner with automatic focus alteration produced images with less focus disarrangement from the center of the slice and less elevation of CT values. Scanners with automatic focus alteration are less prone to the focus disarrangement and elevation of CT values caused by anode heat accumulation and enable reproducible images to be obtained.
authors.affiliation: Department of Radiology, Showa University Hospital, Japan.
authors.forename: Emi
authors.initials: E
authors.lastname: Watanabe
authors.forename: Tomonari
authors.initials: T
authors.lastname: Funata
authors.forename: Hajime
authors.initials: H
authors.lastname: Saitou
authors.forename: Kyouichi
authors.initials: K
authors.lastname: Katou
authors.forename: Masaru
authors.initials: M
authors.lastname: Nitta
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Nakazawa
mesh_terms: D004566:Electrodes; D006358:Hot Temperature / Q000009:adverse effects*; D019047:Phantoms, Imaging; D015898:Tomography Scanners, X-Ray Computed; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*