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目的筛选胃癌 MR 扩散加权成像(DWI)的较佳扩散敏感因子(b)值,探讨 DWI 在胃癌诊断中的应用价值。方法搜集经病理证实的胃癌患者31例,均行常规 MRT_1WI、T_2WI 和 DWI检查。b 值分别取300 s/mm~2(低 b 值)、600 s/mm~2(中 b 值)和1000 s/mm~2(高 b 值)。自由水分级评价不同 b 值对胃腔内自由水的抑制效果。测量并比较不同 b 值时癌肿及胃腔内自由水的表观扩散系数(ADC)值,比较高 b 值 DWI 与常规 MR T_1WI 及 T_2WI 的胃癌癌肿信噪比(SNR_(Ca))、癌肿-胃壁对比噪声比(CNR_(Ca-GW))、癌肿-胃壁信号强度比(SIR_(Ca-GW))及水-背景信号强度比(SIR_(Water-BN))。结果随 b 值增大,胃腔内自由水信号减低,b 值为300、600和1000 s/mm~2时的 SIR_(Water-BN)分别为8.11±0.77、2.70±0.35和1.13±0.22,差异有统计学意义(F=55.368,P<0.05)。b 值增大,SNR_(Ca)减低,b 值为300、600和1000 s/mm~2时的 SNR_(Ca)分别为55.97±24.56、39.99±16.08和27.23±11.42(F=17.227,P<0.05);CNR_(Ca-Gw)减低,b 值为300、600和1000 s/mm~2时的 CNR_(Ca-GW)中位数分别为24.31、20.97和12.73(χ~2=16.692,P<0.01);SIR_(Ca-Gw)增高,b 值为300、600和1000 s/mm~2时的 SIR_(Ca-Gw)中位数分别为1.90、2.29和2.45(χ~2=9.923,P<0.01)。b 值增大,胃癌癌肿 ADC 值降低,b 值为300、600和1000 s/mm~2时的胃癌癌肿 ADC 值分别为(1.96±0.91)×10~(-3)、(1.43±0.41)×10~(-3)和(1.18±0.25)×10~(-3)mm~2/s(F=12.066,P<0.05)。高 b 值 DWI CNR_(Ca-GW)(中位数为12.46)及SIR_(Ca-GW)(中位数为2.45)均高于常规 T_1WI(中位数分别为2.35和1.04;Z 值分别为-3.746和-4.432,P 值均<0.01)及 T_2WI 序列(中位数分别为3.92和1.20;Z 值分别为-3.518和-4.407,P 值均<0.01)。结论高 b 值 DWI 得到胃癌的 ADC 值更加接近组织真实值,并可有效抑制胃腔内容物信号,突出癌肿信号差异;DWI 辅助常规 MR 检查,可更好地显示和判断胃癌病变。
Objective To screen the better diffusion-sensitive factor (b) values of MR diffusion-weighted imaging (DWI) in gastric cancer and to explore the value of DWI in the diagnosis of gastric cancer. Methods Totally 31 patients with gastric cancer confirmed by pathology were examined by conventional MRT_1WI, T_2WI and DWI. The values of b are 300 s / mm ~ 2 (low b value), 600 s / mm ~ 2 (medium b value) and 1000 s / mm ~ 2 (high b value), respectively. Free Water Grading Evaluation of Inhibitory Effects of Different b Values on Free Water in Gastric Cavity. The apparent diffusion coefficient (ADC) value of the free water in the tumor and gastric cavity at different b values was measured and compared. The signal to noise ratio (SNR_ (Ca)) of gastric cancer was compared between high b value DWI and conventional MR T_1WI and T_2WI. (CNR Ca-GW), SIR Ca-GW and SIR Water-BN. Results As the b value increased, the signal of free water in the gastric cavity decreased. The SIR (Water-BN) values at the b values of 300, 600 and 1000 s / mm ~ 2 were 8.11 ± 0.77, 2.70 ± 0.35 and 1.13 ± 0.22, The difference was statistically significant (F = 55.368, P <0.05). The value of b increased and the value of SNR_ (Ca) decreased. The SNR_ (Ca) of b values were 55.97 ± 24.56,39.99 ± 16.08 and 27.23 ± 11.42 (F = 17.227, P < CNR_ (Ca-Gw) decreased. The median CNR_ (Ca-GW) at b values of 300, 600 and 1000 s / mm ~ 2 were 24.31, 20.97 and 12.73, respectively <0.01). The median of SIR Ca-Gw at b values of 300, 600 and 1000 s / mm 2 were 1.90, 2.29 and 2.45 (χ ~ 2 = 9.923, P <0.01). The ADC value of gastric cancer decreased when b value increased. The ADC values of gastric cancer with b value of 300, 600 and 1000 s / mm ~ 2 were (1.96 ± 0.91) × 10 ~ (-3) and (1.43 ± 0.41) × 10 ~ (-3) and (1.18 ± 0.25) × 10 ~ (-3) mm ~ 2 / s (F = 12.066, P <0.05). High b value DWI CNR_ (Ca-GW) (median 12.46) and SIR Ca-GW (median 2.45) were higher than the conventional T_1WI (median were 2.35 and 1.04 respectively; Z values were -3.746 and -4.432, P <0.01) and T_2WI sequences (median 3.92 and 1.20 respectively; Z values were -3.518 and -4.407 respectively, P <0.01). Conclusions The ADC value of gastric cancer with high b value DWI is closer to the true value of the tissue and can effectively inhibit the contents of gastric contents and highlight the difference of cancer signals. DWI can be used to confirm the diagnosis of gastric cancer.