Narr Katherine L, Hageman Nathan, Woods Roger P, Hamilton Liberty S, Clark Kristi, Phillips Owen, Shattuck David W, Asarnow Robert F, Toga Arthur W, Nuechterlein Keith H
Laboratory of Neuro Imaging, Geffen School of Medicine, UCLA, Los Angeles, CA, USA.
Psychiatry Res. 2009 Jan 30;171(1):20-32. doi: 10.1016/j.pscychresns.2008.03.008. Epub 2008 Dec 10.
Mean diffusivity (MD), the rotationally invariant magnitude of water diffusion that is greater in cerebrospinal fluid (CSF) and smaller in organized brain tissue, has been suggested to reflect schizophrenia-associated cortical atrophy. Regional changes, associations with CSF, and the effects of genetic predisposition towards schizophrenia, however, remain uncertain. Six-direction diffusion tensor imaging DTI and high-resolution structural images were obtained from 26 schizophrenia patients, 36 unaffected first-degree patient relatives, 20 control subjects and 32 control relatives (N=114). Registration procedures aligned diffusion tensor imaging (DTI) data across imaging modalities. MD was averaged within lobar regions and the cingulate and superior temporal gyri. CSF volume and MD were highly correlated. Significant bilateral temporal, and superior temporal MD increases were observed in schizophrenia compared with unrelated control probands. First-degree relatives of schizophrenia probands showed larger MD measures compared with controls within bilateral superior temporal regions with CSF volume correction. Superior temporal lobe brain tissue deficits and proximal CSF enlargements are widely documented in schizophrenia. Larger MD indices in patients and their relatives may thus reflect similar pathophysiological mechanisms. However, persistence of regional MD effects after controlling for CSF volume, suggests that MD is a sensitive biological marker of disease and genetic liability, characterizing at least partially distinct aspects of brain structural integrity.
平均扩散率（MD）是水扩散的旋转不变量，在脑脊液（CSF）中较高，在有组织的脑组织中较低，有人认为它反映了与精神分裂症相关的皮质萎缩。然而，区域变化、与脑脊液的关联以及精神分裂症遗传易感性的影响仍不确定。对26名精神分裂症患者、36名未受影响的一级患者亲属、20名对照受试者和32名对照亲属（N = 114）进行了六方向扩散张量成像（DTI）和高分辨率结构成像。配准程序使不同成像模态的扩散张量成像（DTI）数据对齐。在叶区域以及扣带回和颞上回内对MD进行平均。脑脊液体积与MD高度相关。与无关对照先证者相比，精神分裂症患者双侧颞叶和颞上MD显著增加。在进行脑脊液体积校正后，精神分裂症先证者的一级亲属在双侧颞上区域的MD测量值比对照组更大。颞上叶脑组织缺损和近端脑脊液扩张在精神分裂症中已有广泛记录。因此，患者及其亲属中较大的MD指数可能反映了相似的病理生理机制。然而，在控制脑脊液体积后区域MD效应仍然存在，这表明MD是疾病和遗传易感性的敏感生物学标志物，至少部分地表征了脑结构完整性的不同方面。
