MR全身扩散加权成像探查小儿恶性肿瘤原发部位及转移灶的研究

目的 评价MR全身扩散加权成像(WB-DWI)探查小儿恶性肿瘤原发部位及转移灶的价值.方法 回顾性分析行WB-DWI检查的62名健康体检儿及经CT、MRI及临床均确诊为恶性肿瘤的40例患儿资料.正常组按年龄分为0～12个月、12个月以上至5岁及5岁以上3组,分析正常组WB-DWI图像特点,并采用McNemar检验比较WB-DWI与WB-DWI结合MRI、CT两种方法对转移瘤的检出情况;采用配对t检验比较肿瘤组原发灶及转移灶与正常对照组对应部位ADC值的差异.结果 WB-DWI图显示正常组小儿干骺端信号随年龄增加逐渐减低.WB-DWI检测原发灶的敏感度为100%(40/40),对全身转移灶诊断敏感度为89.2%(58/65),阳性预测值为90.6%(58/64);WB-DWI结合MRI、CT对全身转移灶诊断的敏感度为95.4%(62/65),阳性预测值为95.4%(62/65),两方法间诊断的敏感度差异无统计学意义(x2=2.25,P＞0.05).脑(5例)、肝(6例)、肾(8例)、肾上腺(11例)部位的原发肿瘤ADC值分别为(0.76±0.19)×10-3、(0.97±0.29)×10-3、(0.81±0.12)×10-3和(0.93±0.28)×10-3mm2/s,正常对照组对应部位ADC值分别为(1.02±0.11)×10-3、(1.57±0.58)×10-3、(1.19±0.15)×10-3和(2.03±0.42)×10-3mm2/s,差异均有统计学意义(t值分别为3.54、3.84、7.02和12.57,P值均＜0.05).脑(9例)、肝(13例)、肾(17例)、骨(7例)和淋巴结(6例)部位转移灶ADC值分别为(0.88±0.12)×10-3、(0.98±0.10)×10-3、(0.89±0.11)×10-3、(0.96±0.15)×10-3和(0.83±0.14)×10-3mm2/s,正常对照组对应部位ADC值分别为(1.01±0.09)×10-3、(1.45±0.39)×10-3、(1.31±0.27)×10-3、(1.34±0.20)×10-3和(0.99±0.08)×10-3mm2/s,差异均有统计学意义(t值分别为4.09、45.50、6.95、14.00和9.27,P值均＜0.05).结论 正常婴幼儿WB-DWI图像的四肢长管状骨干骺端多呈高信号;WB-DWI适用于探查小儿恶性肿瘤原发及转移灶,具有较高的敏感度,与常规CT、MRI结合有提高敏感度的趋势.

Preliminary study of whole body MR diffusion weighted imaging in detecting pediatric primary and metastatic malignant tumor

Objective To assess the efficacy of whole body diffusion weighted imaging (WB-DWI) in detecting pediatric primary and metastatic malignant tumor. Methods WB-DWI was performed in 62 healthy pediatric volunteers and 40 pediatric patients with confirmed malignant tumors. The healthy volunteers were divided into three groups: 0 to 12 months, more than 12 months to 5 years and more than 5 to 15 years. The characteristics of WB-DWI imaging were analyzed. McNemar test was used to compare the difference of detection on metastasis between WB-DWI and WB-DWI combined with MRI, CT. The mean apparent diffusion coefficient ( ADC ) values of primary tumors and metastases were measured by using paired t test and compared with those of corresponding body regions of control group. Results WB-DWI imaging shows that signal intensity of metaphysis gradually reduces with increasing age in the normal pediatric group. On WB-DWI primary malignant tumors showed 100％ (40/40) high signal intensity and metastases showed high signal intensity in 89.2％ (58/65) on WB-DWI, with a positive predictive value of 90. 6％ (58/64). The detecting rate for metastases increased to 95.4％ (62/65) when WB-DWI was combined with MRL/CT, with a positive predictive value of 95.4％ (62/65) there was no statistically significant difference ( x2 = 2. 25, P ＞ 0. 05 ). The ADC values of primary malignant tumor sites in head ( n = 5), liver(n=6), kidney(n=8), adrenal(n=ll) were (0.76 ±0. 19) ×10-3 , (0. 97 ±0.29) × 10-3,(0. 81 ±0. 12) × 10-3 and (0. 93 ±0. 28) × 10-3mm2/s and those of corresponding body regions of control group were (1.02 ±0. 11) × 10-3,(1.57 ±0.58) × 10-3, (1.19 ±0. 15) × 10-3 and (2.03 ±0.42) ×10-3mm2/s respectively, there were statistically significant difference( t values were 3.54,3. 84,7. 02 and 12. 57 ;P ＜ 0. 05 ). The A DC values of metastases sites in head ( n = 9 ), liver ( n = 13 ), kidney ( n = 17 ),bone(n =7) and lymph node(n =6) were (0. 88 ±0. 12) × 10-3, (0. 98 ±0. 10) × 10-3, (0. 89 ±0. 11 ) × 10-3, (0. 96 ±0. 15) × 10-3 and (0. 83 ±0. 14) × 10-3mm2/s, and those of corresponding body regions of control group were (1.01 ±0.09) × 10-3, (1.45 ±0.39) × 10-3, ( 1.31 ±0.27) × 10-3, ( 1.34 ±0. 20) × 10 -3 and ( 0. 99 ± 0. 08 ) × 10 -3 mm2/s, there were statistically significant difference ( t values 4. 09,45.50,6. 95,14. 00 and 9. 27 ;P ＜ 0. 05 ). Conclusions Increased signal intensity is more frequently observed in metaphysis of long bone in normal children on WB-DWI. With a high detection rate for primary and metastatic malignant tumors, WB-DWI combined with conventional CT; MRI can significantly improve their sensitivity.