Diffusion spectrum imaging(DSI),a newly developed MRI technique,affords the capacity to map complex fiber architectures in tissues with sufficient angular resolution by imaging the spectra of tissue water diffusion.By contrast,diffusion tensor imaging(DTI),the currently widely used technique based on the 2nd order tensor model,obtains an approximation of the complex diffusion,and provides only one global maximal direction corresponding to the primary eigenvector for each voxel.As a generalized model-free diffusion imaging technique,firstly,DSI employs the probability density function to describe the diffusion process in each voxel;secondly,a sufficient dense signal sample derived from repeated applications of diffusion-weighed gradients ensures its capability to resolve the diffusion probability density function;thirdly,specific computer visualization techniques are used to extract the diffusion information and reconstruct the geometrical properties of tissue microstructure.The capacity to unravel complex tissue architecture,recent improvements in hardware and ongoing optimization of sequence design and algorithm enable a rapid growth of DSI for research use and future incorporation into clinical protocols.This paper introduces the basic principles of DSI and then compares the characteristics of DSI and DTI schemes.Finally,the typical applications of DSI to date are reviewed.Abstract:SUMM ARY D iffusion spectrum imaging(DSI),a newly developed MR I technique,affords the capacity to map complex fiber architectures in tissues with sufficient angular resolution by imaging the spectra of tissue water d iffusion.By contrast,d iffusion tensor imaging(DTI),the currently widely used technique based on the 2nd order tensormodel,obtains an approximation of the complex d iffusion,and provides on-ly one globalmaximal d irection correspond ing to the primary eigenvector for each voxel.As a generalized model-free d iffusion imaging technique,firstly,DSI employs the probability density function to describe the d iffusion process
抑郁症的序贯治疗（Sequenced Treatment Alternatives to Relieve Depression，简称STAR＊D）研究是目前为止关于重度抑郁障碍的最大型的前瞻性临床研究，由美国国立精神卫生研究所（National Institute of Mental Health，NIMH）出资3500万美金，自2001年开始历时7年完成。该研究以期能够对现实世界中对治疗抵抗的抑郁症患者的治疗措施的可行性进行评估，并改善其临床转归，尽管没有最终发现哪种药物或者方法可以一标中的或者一劳永逸，但是当临床医生在开始为抑郁症患者开始治疗时或者最初的治疗失败后，这项研究的结果都可以为医生们提供指导。
