Algorithm expression on the optimal reconstruction increment in coronal multi-planar reformation of temporal bone for multislice CT
10.3760/cma.j.issn.1005-1201.2013.006.014
- VernacularTitle:多层螺旋CT颞骨冠状面影像重组最适重建间隔的算法表达
- Author:
Chuanya LIU
;
Xinwu MA
;
Yongxia ZHAO
;
Kai LIU
;
Bin ZHAO
- Publication Type:Journal Article
- Keywords:
Tomography,X-ray computed;
Quality control;
Evaluation studies
- From:
Chinese Journal of Radiology
2013;(6):541-544
- CountryChina
- Language:Chinese
-
Abstract:
Objective To study algorithm expression of the optimal reconstruction increment with which images could be reconstructed without loss of z-direction spatial resolution for multislice spiral CT.Methods Using Gauss function and signal sampling principle,an algorithm expression was deduced to calculate the optimal reconstruction increment with which images could be reconstructed without loss of zdirection spatial resolution.Spiral slice sensitivity profile (SSP) phantom was scanned using Somatom Sensation 64-slice spiral CT and temporal bone protocol as those used for clinic,axial images were reconstructed with slice thickness of 0.600 mm and increment of 0.100,0.300,0.400 and 0.500 mm respectively.Then SSPs and full width at half maximum (FWHM) were measured and modulation transfer functions were obtained by Fourier transfer from SSPs.Axial CT scan of 7 normal temporal bones in 6 patients were obtained by the same CT system and parameters as above.Coronal MPR images of temporal bone out of different reconstruction increment were obtained and the quality of reconstructed images were independently assessed by three senior radiologists using a four-point scale and blinded the information of reconstruction.Experimental data were processed and two-way ANOVA(in which Dunnett t test was selected for multiple comparisons) was performed with statistic software SPSS10.0.P ＜ 0.05 was considered as significant difference.Results (1) The measured FWHM of reconstruction slice thickness of 0.600 mm was 0.665 mm,so the optimal reconstruction increment calculated with the algorithm expression in this article was 0.296 mm(≈0.300 mm).Objective evaluation showed that there was obviously aliasing in high spatial frequency range of MTF curve when reconstruction increment was more than 0.300 mm,i.e.both 0.400 and 0.500 mm.Clinical scores of coronal MPR images of temporal bone reconstructed with different increment had significant difference(F =505.374,P ＜ 0.01).Treating reconstruction increment of 0.100 mm as a control group and comparing another groups against it,there was no significant difference for reconstruction increment of 0.300 mm (t =-0.222,P ＞ 0.05),while there were significant difference for 0.400 and 0.500 mm (t =-1.333、-15.889,P ＜ 0.05,P ＜ 0.01).Conclusion It was proved that the angorithm expression deduced in this article was proper because of the consistence between the calculated value and the results from objective and clinical evaluation.The optimal reconstruction increment without loss of z-direction spatial resolution is 0.445 times as large as FWHM for multislice CT.
