Improvement of spatial resolution in the longitudinal direction for isotropic imaging in helical CT.
Experiments were conducted to confirm the isotropic spatial resolution of multislice CT with a 0.5 mm slice thickness. Isotropic spatial resolution means that the spatial resolution in the transaxial plane (X-Y plane) and that in the longitudinal direction (Z direction) are equivalent. To obtain point spread function (PSF) values in the X-Y-Z directions, three-dimensional voxel data were obtained by helical scanning of a bead phantom. The modulation transfer function (MTF) values were then obtained by three-dimensional Fourier transform of the PSF. Evaluation of the spatial resolution in the X-Y-Z directions by the MTF values showed that the spatial resolution in the Z direction does not depend on the reconstruction kernel used. It was also found that the spatial resolution in the Z direction, as compared with that in the X-Y plane, is superior with the standard kernel for the abdomen and is inferior with the high-definition kernel for the ears/bones. By performing sharpening filter processing in the Z direction with a high-definition kernel, comparable spatial resolution could be obtained in the X-Y-Z directions. It was confirmed that adjusting the spatial resolution in the Z direction with the reconstruction kernel used is an effective method for isotropic imaging.
Tsukagoshi
Shinsuke
S
CT Systems Development Department, Toshiba Medical Systems Corporation, 1385 Shimoishigami Otawara-Shi, Tochigi 324-8550, Japan. shinsuke.tsukagoshi@toshiba.co.jp
Ota
Takamasa
T
Fujii
Misako
M
Kazama
Masahiro
M
Okumura
Miwa
M
Johkoh
Takeshi
T
D055592:Biophysical Phenomena; D001703:Biophysics; D004429:Ear Ossicles / Q000000981:diagnostic imaging; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000706:statistics & numerical data; D019047:Phantoms, Imaging; D036542:Tomography, Spiral Computed / Q000379:methods* / Q000706:statistics & numerical data