水模体摆放方式对CT性能测试结果的影响研究

Study of the effect of water phantom setting patterns on CT

目的比较悬挂放置和床上放置两种模体摆放方式对CT值(水)、噪声、均匀性测试结果的影响,明确哪一种摆放方式更为合理。方法按照GB 17589-2011中的方法进行实验。实验中分别采用两种模体摆放方式,一种是利用CATPHAN500模体箱将CTWV17型悬挂式水模体放置于碳纤维板床外;一种是直接将CTWV17型悬挂式水模体放置于碳纤维板床上。采用同一扫描条件,分别扫描5次并获取CT影像5幅,在影像上测量CT值(水)、噪声、均匀性。结果 CT值(水)测试中,采用水模体悬挂放置的测试方法,结果为(0. 39±1. 49) HU;采用水模体放置床上的测试方法,结果为(1. 00±1. 83) HU;采用配对的t检验进行均数的比较,t=-2. 55,P=0. 022。噪声测试中,采用水模体悬挂放置的测试方法,结果为0. 23±0. 06;采用水模体放置床上的测试方法,结果为0. 25±0. 08;采用配对的t检验进行均数的比较,t=-3. 38,P=0. 004。均匀性测试中,采用水模体悬挂放置的测试方法,结果为(0. 47±0. 66) HU;采用水模体放置床上的测试方法,结果为(-0. 06±1. 82) HU;采用配对的t检验进行均数的比较,t=4. 25,P=0. 001。两种放置方法 CT值(水)、噪声和均匀性的实验结果均存在差异。结论碳纤维床板对CT值(水)、噪声、均匀性有潜在影响,在测试CT值(水)、噪声和均匀性时,应当采用模体悬挂放置的方式。

Objective To compare the effects of two types of phantom setting methods( suspension and place-on-couch) on the CT value( water),noise and uniformity of performance test results,and to find out which mehtod is more reasonable.Methods According to the method in GB 17589-2011,two kinds of phantom place patterns were tested: suspend the CTWV17 phantom on-the phantom box or directly place the CT-WV17 on couch. With the same scanning parameters,the phantom was scanned for 5 times at each setting patterns,and the CT value( water),noise and uniformity on the images were measured. Results For the CT value( water),the results were averaged to be( 0. 39 ± 1. 49) HU and( 1. 00 ± 1. 83) HU for different phantom setting patterns,respectively,and the difference was significant( t =-2. 55,P = 0. 022). In noise test,the results were averaged to be( 0. 23 ± 0. 06) and( 0. 25 ± 0. 08) for the two methods,respectively,and the difference was also significant( t =-3. 38,P = 0. 004). In the unifomity test,the averaged results were( 0. 47 ± 0. 66) HU and(-0. 06 ± 1. 82) HU for the two setting patterns,respectively,the significant difference( t = 4. 25,P = 0. 001) was also observed. Conclusion Carbon fiber couch has a potential impact on CT value( water),noise and uniformity. When testing CT value( water),noise and uniformity,the phantom-suspension should be used.