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  

Algorithm expression on the optimal reconstruction increment in coronal multi-planar reformation of temporal bone for multislice CT

作　　者：刘传亚[1] 马新武[1] 赵永霞[2] 刘凯[1] 赵斌[1] 

机构地区：[1]山东省医学影像研究所,济南250021 [2]河北大学附属医院放射科

出　　处：《中华放射学杂志》2013年第6期541-544,共4页Chinese Journal of Radiology

摘　　要：目的建立多层螺旋CT在z轴空间分辨率无损条件下影像重组时最适重建间隔的数学模型与算法表达。方法根据高斯理论及信号抽样原理，推导出Z轴空间分辨率无损重建最适重建间隔的算法表达式，该式是有效层厚的函数。应用Siemens64层螺旋CT与内耳扫描模式对多层螺旋CT层敏感度曲线（SSP）测试体模扫描，测试SSP和有效层厚，进行客观评价。分别以0．100、0．300、0．400、0．500rnnl间隔对SSP进行傅立叶变换，获得z轴调制传递函数（MTF）。选择临床患者6例7耳（仅健侧颞骨），分别以0．100、0．300、0．400、0．500mm间隔重建横断面图像，并依此进行冠状面MPR。由3名高年资影像诊断医师对9个高对比度微细解剖结构影像图进行软『列读盲法评分。以重建间隔为处理因素对临床评分数据行双因素方差分析，并对处理组数据行两两比较（Dunnettt检验）。结果（1）标称层厚0．600mm的测试值（有效层厚）是0．665mm，根据本研究中算法计算的最适重建间隔是0．296mm（=0．300nlm）。（2）客观评价显示重建间隔0．100和0．300lnnl的MTF曲线相重合且没有混叠，重建间隔0．400和0．500IIlnl的MTF曲线在中高频区域出现混叠。（3）不同重建间隔的颞骨冠状面MPR的临床评分差异有统计学意义（F=505．374，P〈0．01）。以重建间隔0．100mm为控制组进行处理组间的两两比较，与重建间隔0．30mm相比差异无统计学意义（t=-0．222，P〉0．05），与重建间隔0．400和0．500mm相比差异均有统计学意义（t值分别为-1．333、-15．889，P值分别〈0．05、〈0．01）。结论客观评价和临床评价均与数学模型计算结果相符，数学模型和算法表达式可以作为影像重组时最适重建间隔的设置依据。Objective To study algorithm expression of the optimal reconstruction increment with which images could be reconstructed without loss of z-direction spatial resolution for nmhislice 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 z- direction 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 eorooal MPR images of temporal bone reconstructed with different increment had significant differenee（F = 505. 374,P 〈 0. 01 ）. Treatin

关 键 词：体层摄影术 X线计算机 质量控制 评价研究 

分 类 号：R816[医药卫生—放射医学]