
Proceedings Paper
An experimental study on the shift-variant MTF of CT systems using a simple cylindrical phantomFormat | Member Price | Non-Member Price |
---|---|---|
$17.00 | $21.00 |
Paper Abstract
The modulation transfer function (MTF) is a typical parameter to measure the spatial resolution, which is an essential
factor for evaluating the performance of computed tomography (CT) systems. It is known that the CT system does not
follow the shift-invariant manner because of the cone-beam geometry and the transformation from the cylindrical
coordinates to the axial coordinates when the image reconstruction is employed. Several studies reported that if the
position of impulse receded from the center of a region of interest (ROI), the MTF degraded continuously. In this study,
the trend of shift-variant characteristics of CT systems was measured and analyzed using a novel multi-cylindrical
phantom. This study used to determine a point spread function (PSF) and MTF of a CT system using a simple cylindrical
phantom. First of all, the optimal diameter of cylinder phantoms was experimentally determined as 70 mm to obtain
reliable PSFs. Two kinds of field of views (FOVs), 40 cm and 60 cm, were used to vary reconstructed pixel sizes. The
shift-variant MTF curves were acquired at five off-center positions per FOV. For the effective analysis of MTF shiftvariance,
the integrated MTF values were calculated and used. In the result, the MTF slightly decreased as diameter
increased from CT center in the central region within the distance of 10 cm. Moreover, a considerable MTF decrease
suddenly occurred around the distance of 15 cm in the actual FOVs. The decreasing trend of the off-center spatial
resolution of CT cannot be neglected in recent radiologic and radio-therapeutic fields requiring high degree of image
precision, especially in sub-mm images. It is recommended that the ROI is laid on the CT center as close as possible. A
novel cylindrical phantom was finally suggested to effectively measure PSFs with optimal diameters for clinical FOVs in
this study. This phantom is cheap and convenient to use because it was only made of acryl with simple geometry. It is
expected that the spatial resolution of CT can be easily monitored using our methodology in clinical CT sites.
Paper Details
Date Published: 6 March 2013
PDF: 7 pages
Proc. SPIE 8668, Medical Imaging 2013: Physics of Medical Imaging, 86684Q (6 March 2013); doi: 10.1117/12.2007862
Published in SPIE Proceedings Vol. 8668:
Medical Imaging 2013: Physics of Medical Imaging
Robert M. Nishikawa; Bruce R. Whiting; Christoph Hoeschen, Editor(s)
PDF: 7 pages
Proc. SPIE 8668, Medical Imaging 2013: Physics of Medical Imaging, 86684Q (6 March 2013); doi: 10.1117/12.2007862
Show Author Affiliations
Soohwa Kam, Pusan National Univ. (Korea, Republic of)
Hanbean Youn, Pusan National Univ. (Korea, Republic of)
Hanbean Youn, Pusan National Univ. (Korea, Republic of)
Ho Kyung Kim, Pusan National Univ. (Korea, Republic of)
Hosang Jeon, Pusan National Univ. Yangsan Hospital (Korea, Republic of)
Hosang Jeon, Pusan National Univ. Yangsan Hospital (Korea, Republic of)
Published in SPIE Proceedings Vol. 8668:
Medical Imaging 2013: Physics of Medical Imaging
Robert M. Nishikawa; Bruce R. Whiting; Christoph Hoeschen, Editor(s)
© SPIE. Terms of Use
