摘要  目的：通过观察急性白血病治疗前后骨髓的MRI表现和T1及对比度噪声比（CNR）的测定，对照临床、病理资料，探讨急性白血病骨髓MRI定性和定量诊断价值。材料与方法：选择经临床确诊为急性白血病的患者38例，缓解组25例，对照组35例进行MRI检查及T1值和对比度噪声比（CNR）的测定。结果：急性白血病T1WI ：治疗前组38例,腰骶椎、髂骨及股骨近段均表现为信号降低；化疗缓解组25例表现为不同程度的信号增高。 T2WI：38例治疗前组和25例化疗后组各椎体、髂骨、股骨上段呈等信号。外周血B%、骨髓B%、腰椎T1值、腰椎/皮下脂肪CNR、股骨骨髓/皮下脂肪CNR于急性白血病治疗前组与正常对照组、治疗前组与缓解组间的差异均有显著性（P<0.05），缓解组与正常对照组间的差异无显著性（P>0.05），不同细胞类型间的差异无显著性（ P>0.05）。腰椎T1值于不同性别、年龄组间的差异无显著性（ P>0.05）。治疗前组骨髓B%与腰椎T1值、与腰椎/皮下脂肪CNR，外周血B%与腰椎T1值、与腰椎/皮下脂肪CNR及腰椎T1值与腰椎/皮下脂肪CNR 之间成直线相关（P<0.05）。结论：急性白血病的ＭＲＩ检查为一种无创性方法，MRI表现具有一定的特征性，在估计病情的严重程度及治疗效果的评价简便实用，为避免多次重复骨髓穿刺检查以及全面观察急性白血病骨髓浸润范围和程度有着重要的临床意义。关键词：急性白血病  磁共振成像（MRI） 诊断  治疗The Vale of MRI in acute leukemia naturally and quantitatively[Abstract]  objective  To evaluate MRI diagnosis of bone narrow in acute leukemia by observing MRI appearance and calculating T1 value,CNR(ratio of contrast/noise) in patients before and after chemothrapy, contrasting to materials in clinic and pathology. Materials and methods Thirty-eight patients, with acute leukemia were examined.  Twenty-five patients served as remission group. As control group ,35 healthy volunteers were performed MR examination with identical methods. Serial MR studies include observation of MRI character and measurement of T1 value and CNR in all patients. Result  Of all 38 cases of acute leukemia at the time of diagnosis compare with control group: Hypointense signal in T1WI by well-distribute were found in lumbosacral vertebral, iliac, and femur approaching. Isointense signal in T2WI was found in all cases we done. The signal intensity in T1WI tended to normal in all 25 remission cases of acute leukemia. Isointense signal also found in T2WI in remission cases. The difference of T1 value in lumber, CNR in lumber/subcutaneous fat and femur/subcutaneous fat, B% in blood and marrow were significant (P<0.05) among groups of diagnosis and control, diagnosis and remission; but they weren’t significant (p>0.05) between groups of control and remission, and cellulality among ALL, AML, ALL+AML .Positive linear correlation was found among T1 value in lumber and B% in blood, T1 value in lumber and B% in marrow, CNR in lumber/subcutaneous fat and B% in blood, CNR in lumber/subcutaneous fat and B% in marrow, T1 value in lumber and CNR in lumber/subcutaneous fat. There were statistic Significant among them (P<0.05). Conclution MRI is  a none-invasive method in check marrow in acute leukemia .The MRI appearance  in acute leukemia was convenient and useful especially in estimating the state of illness and monitoring therapeutic efficacy .There was great clinical valuable in acute leukemia to avoid repetition marrow puncture and observe the scope and level of infiltration.[Key words]  acute leukemia; Magnetic resonance imaging (MRI); diagnosis; chemothyrapy.    既往，急性白血病定性及定量的检查方法为骨髓穿刺涂片或活检，为有创伤性的检查。自从磁共振成像仪（MRI）问世并于1980年开始应用于临床以后，由于其能灵敏地反映骨髓组织结构和化学成分的变化，故在一定程度上能从宏观的图象改变而反映骨髓微观分子结构的改变。至今，国外已有较多的研究[1~2]，国内只有少数文献报道[3]。本研究旨在结合本地的病例特点，采用大病例组，探讨急性淋巴细胞性白血病（ALL）和急性髓细胞性白血病（AML）的MRI表现，并与临床、病理联系，系统而深入进行定性和定量的研究，以期使MRI成为诊断本病和观察其疗效的一种重要手段。                              材料与方法 搜集本院1997~1999年间住院经骨髓穿刺涂片或活检检查确诊为急性白血病且未经化疗的患者38例，男19例，女19例，年龄4~65岁，平均18±15 岁。其中ALL27例，AML11例。缓解组25例次，其中，10例只作了缓解后MRI检查，15例有化疗前后MRI对比，9例化疗后作了2次以上MRI追踪复查。对照组35例，选择年龄匹配的，无造血系统疾病史的正常志愿者。检查使用Elscint公司生产的GYREX-V  DLX型0.5T超导磁共振成像仪，所有病例均作了腰骶椎矢状面和髂骨、股骨近段冠状面的检查。对腰椎，采用腰椎表面线圈作矢状面T1WI(TR450/TE20,TR700/TE20ms)、T2WI(TR3600/TE80ms)；对骨盆（包括双股骨上段），用体部线圈做冠状面T1WI(TR450ms、TE20,TR700、TE20ms)、T2WI(TR3600ms、TE80ms)成像。层厚5mm，层距1mm，矩阵180×256。MRI信号的肉眼观察分析方法：以MRI信号相对固定的脊髓为参照物，腰椎、骨盆及股骨近段的MRI信号与脊髓相等、高、低相应设为等信号、高信号、低信号。T1值的测量是对T1WI的两种序列(TR450/TE20,TR700/TE20ms)进行T1-MAPS重建，取第一至第三腰椎正中矢状面最大ROI测量三个椎体T1值，再求得三个椎体T1值的平均值代表本病例腰椎的T1值。股骨近段用与腰椎类似的方法，在两侧股骨转子间测量T1值，其平均值代表本病例股骨近段的T1值。标准化信号强度的测量和计算：选择腰椎及股骨近段的最大层面，选择相同的ROI测量皮下脂肪，骨髓的信号强度S和标准差σ，按CNR=∣S1-S2∣/（σ1-σ2）1/2来计算骨髓与皮下脂肪及骨髓与