RÉSUMÉ
Objective To establish the mathematical model and perform experimental mensuration on effective slice width for 4-slice spiral CT. Methods First, assuming the spiral slice sensitivity profile (SSP) was Gauss distribution, a formula about effective slice width, defined as the full width at half maximum (FWHM) of SSP, was get. Then, using Philips Mx8000 4-slice spiral CT system and the same CT technique as those used for clinical CT, CTP 528 of Phantom Catphan 500 was scanned with parameters as follows: 120 kV, 150 mAs, 180 mm FOV, 512×512 Matrix, 180° linear interpolation, different pitch and 0.5 mm detector width. Finally, FWHM was got from the coronal multiplanar reconstruction image passing by the center of tungsten ball in CTP528 for each sequence. Results With pitch of 0.500, 0.625, 0.875, 1.000, 1.250, 1.500 and 1.750, the measured FWHM was 0.7, 0.7, 0.7, 0.8, 0.7, 0.7 and 0.7 mm, respectively. With detector width of 0.5, 1.0 and 5.0 mm, the measured FWHM was 0.7, 1.2, and 6.7 mm, respectively. All the measured effective slices were higher than those of theoretical values. Conclusion The relativity between effective slice width and detector width is direct proportion, while that between effective slice width and pitch is non-linear.
RÉSUMÉ
QA(Quality Assurance)of CT offers dependable guarantee for the daily work of hospital.Slice width is an important characteristic of the all parameters.In this study,we gained a new method to detect slice thickness work by computer from the analysis of the CT image of the phantom named Catphan412 in a programmed way.