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目的比较不同扩散敏感系数(b值)对直肠癌病变的显示及对背景的抑制能力,探讨直肠癌术前3.0 T MR扩散加权成像(DWI)的合理b值。方法经病理证实直肠癌36例,术前行3.0 T MR DWI,b值取500、800、1000、1200、1500 s/mm2。分析各b值对肿瘤信号强度(ST),肿瘤信噪比(SNR),肿瘤与直肠系膜(CNRT/F)、肿瘤与盆壁肌肉(CNRT/M)等对比噪声比(CNR)的影响,以及各b值对肿瘤病变的显示及对背景的抑制能力。结果 ST、SNR、CNRT/F及CNRT/M分别在b值为1000 s/mm2~1200 s/mm2之间差异无明显统计学意义(P=0.22,P=0.119,P=0.102,P=0.161),而在b值<1000或>1200 s/mm2时差异有明显统计学意义(P<0.05)。在各b值对肿瘤病变的显示及对背景的抑制能力判定中,主观评分在b值为1000 s/mm2~1200 s/mm2之间及1200 s/mm2~1500s/mm2之间差异无明显统计学意义(P=0.067、P=0.110),而在b值<1000 s/mm2时差异有明显统计学意义(P<0.05)。结论当b值取1000或1200 s/mm2时,既能获得良好的DWI图像,又能满足诊断需求,可作为直肠癌术前3.0 T MR扩散加权成像的合理b值。
Objective To compare the sensitivity of different diffusion coefficient (b values) to the pathological changes of rectal cancer and the ability to suppress background, and to investigate the reasonable b value of preoperative 3.0 T MR diffusion weighted imaging (DWI) for rectal cancer. Methods Thirty-six cases of rectal cancer were confirmed by pathology. 3.0 T MR DWI was performed preoperatively. The b values were 500, 800, 1000, 1200 and 1500 s / mm2. The effects of each b value on contrast to noise ratio (CNR) such as tumor signal intensity (ST), tumor signal to noise ratio (SNR), tumor and mesorectal membrane (CNRT / F), tumor and pelvic wall muscle (CNRT / M) As well as the b value of tumor lesions on the display and the ability to inhibit the background. Results There was no significant difference in the values of ST, SNR, CNRT / F and CNRT / M between b values of 1000 s / mm2 and 1200 s / mm2 (P = 0.22, P = 0.109, P = ), While the difference was statistically significant at b values <1000 or> 1200 s / mm2 (P <0.05). In the b value of the tumor lesions on the display and determine the ability to inhibit the background, the subjective score in the b value of 1000 s / mm2 ~ 1200 s / mm2 and between 1200 s / mm2 ~ 1500s / mm2 no significant statistical differences (P = 0.067, P = 0.110). However, the difference was significant at b value <1000 s / mm2 (P <0.05). Conclusions When the value of b is 1000 or 1200 s / mm2, good DWI images can be obtained and the diagnostic requirements can be satisfied. Therefore, it can be used as a reasonable b value for preoperative 3.0 T MR diffusion weighted imaging of rectal cancer.