乳房mr扩散加权成像：比较正常乳腺组织与良性和恶性乳腺病变表观扩散系数值dwi,adc.ppt

The microscopic movement of biological tissues consist of molecular diffusion in the extracellular compartment and microcirculation of blood in the capillary network (flow). Therefore, perfusion is another factor that affects ADC values. 生物组织的微观运动包括在细胞外和微循环的血液中的毛细管网络的水分子扩散（流量）。因此，灌注是另一个影响ADC值的因素。 ADC values also differ with various b-values, as seen in the literature. Images with low b-values result in less diffusion-weighted images, as a lower gradient is applied. 文献报道ADC值因b值的不同而不同。图像的低b值，导致扩散加权图像较低的梯度。 Also, the extension of microvascular structures in malignant lesions may increase the perfusion effect on ADC values in images with low b-values. 此外，在恶性病变微血管结构灌注增加可能会影响低b值的ADC值。 However, the signal-to-noise ratio in these images is higher than that in diffusion images with high b-values. 低b值的信号噪声比高于高b值所在扩散图像。 Typically, at least two b-values should be used during DWI in order to enable meaningful ADC interpretation,although accuracy increases when more b-values are used. 虽然使用更多的b值提高精确度，通常情况下至少两个b值。 In our study, we had used b-values of 0 s/mm2 and 600 s/mm2 in order to limit the examination time. 我们的研究使用0 s/mm2和600 s/mm2 b值，以限制测试时间。 Pereira et al, however, reported no significant difference between the ADC values of benign and malignant lesions when different combinations of b-values were used, and thus concluded that using multiple b-values in a DWI sequence was unnecessary. 但是Pereira等人报告，不同的b值测量D的不同ADC值,对区别良性和恶性病变没有明显差异。因而认为，使用多个b值在DWI序列是不必要的。 Wood hams et al reported that b 750 mm2/s was highly efficient detecting breast masses. Woodhams等报道，B 750 mm2 / s可以高效检测乳腺肿块。 The diagnostic accuracy of DWI for breast can only be ascertained once technical parameters and post-processing procedures are standardised for the modality. DWI对乳腺的诊断准确率在于技术参数和后处理程序方法的标准化。 Major technical limitations associated with it are distortion of the images secondary to susce