脑血管疾病患者的脑白质异常信号的MR随访研究

目的 对脑血管病人群MR图像上的白质高信号(WMH)进行体积定量测量的随访研究,探讨影响其发展的危险因素.方法 对138例临床诊断为脑血管病的患者间隔1年先后进行2次头颅MRI检查.严格记录所有患者研究初始阶段的年龄、收缩压、血糖、血脂、烟酒嗜好以及有无高血压、糖尿病、高脂血症病史等情况,并进行了简易精神状态检查评分(MMSE)和美国国立卫生研究院卒巾量表(NIH Stroke Scale,NIHSS)评分.先采用半自动体积测量软件测量患者前后2次WMH体积以及初始状态下的新近脑梗死灶体积,然后采用多元回归方法筛选对WMH的增加存在影响的危险因素,并分析临床评分、梗死灶体积与WMH增加量之间的相关性.结果 初始WMH体积为(13155±18782)mm3,WMH增加量为(7687±9079)mm3.多元回归方程显示初始WMH体积、灰质梗死、白质梗死对WMH的增加有影响作用.WMH增加量与MMSE评分存在低度负相关(r=-0.266,P=0.002);WMH增加量与NIH评分存在低度正相关(r=0.257,P=0.002).患者脑内灰白质梗死体积之和为(5080.958±12709.2136)mm3,脑梗死体积与WMH增加量存在中度正相关(r=0.416,P<0.001).结论 WMH的发生和发展不但有自身的规律,还会受到脑血管病的影响,尤其与新近脑梗死的体积关系密切.WMH的增加可能与认知功能的下降有关.     

磁共振弥散张量成像联合弥散张量纤维束成像在早期弥漫性轴索损伤中的应用

目的探讨磁共振弥散张量成像(DTI)与弥散张量纤维束示踪技术(DTT)对早期弥漫性轴索损伤(DAI)的诊断应用价值。方法对22例DAI早期(伤后10天内)患者(DAI组)及12例正常志愿者(对照组)分别行常规MR扫描及弥散张量成像扫描。在FA图上分别测量DAI组及对照组双侧半球白质感兴趣区(胼胝体压部、胼胝体膝部、内囊前肢、内囊后肢)部分各向异性(FA)值,将两组感兴趣区(ROI)平均FA值的差异进行比较,并对DAI组FA值与临床GCS评分进行相关性分析。运用弥散张量纤维束成像显示通过病灶的纤维束特征。结果病变组与对照组比较,DAI早期FA值(胼胝体压部0.647±0.069、胼胝体膝部0.615±0.043、内囊前肢0.541±0.065、内囊后肢0.639±0.035)较对照组(胼胝体压部0.748±0.045、胼胝体膝部0.729±0.058、内囊前肢0.622±0.038、内囊后肢0.667±0.027)FA值显著降低(P0.001)。胼胝体压部FA值的变化与GCS评分呈正相关(r=0.736,P=0.001)。DTT较好显示感兴趣区白质纤维束形态,更直观显示脑白质损伤程度。结论 DTI联合DTT是DAI患者检查的敏感方法,FA值评估是DAI程度的重要依据,DDT可观察神经纤维束受损范围。     

扩散张量成像在皮质脊髓束华勒变性中的应用

目的 利用扩散张量成像(DTI)研究皮质脊髓束(CST)不同程度华勒变性(WD)微结构变化特点及临床价值.方法 回顾性分析我院47例单侧运动区脑梗死患者,依据CST信号和体积是否异常将WD分成三组,Ⅰ组:CST白质纤维束无信号及形态学改变,共17例;Ⅱ组:CST白质纤维束呈高信号,但无萎缩,共12例;Ⅲ组:CST白质纤维束呈高信号伴萎缩,共18例.所有患者DTI数据经分析处理,在CST患侧和健侧内囊后支、大脑脚、中脑、延髓层面走行区获取FA、MD、λ1、λ2+3值,将各组WD不同部位健侧与患侧DTI各参数指标行t检验,将大脑脚层面神经生物学指标与NIHSS和MI评分行Spearman相关分析.结果 (1)Ⅰ组患侧与健侧皮质脊髓束λ1有统计学差异(P＜0.05),Ⅱ组患侧与健侧皮质脊髓束FA、MD、λ2+3差异有统计学意义(P＜0.05),Ⅲ组患侧与健侧皮质脊髓束FA、MD、λ1、λ2+3均有统计学差异(P＜0.05).(2)Ⅰ组患者大脑脚区CSTrλ1与NIHSS评分存在负相关(r=-0.747,P＜0.01),rλ1与运动力指数呈正相关(r=0.862,P＜0.01).结论 DTI判断CST WD的严重程度有一定特征,其中λ1可以作为早期发现WD微结构变化以及评价病情严重程度的神经生物学指标.     

正常儿童脑白质发育的DTI研究

目的 :用DTI研究正常儿童脑白质发育特点。方法 :收集50例1~12岁健康儿童脑DTI图像,分析第1组(1~3岁)、第2组(4~6岁)、第3组(7~9岁)及第4组(10~12岁)4个年龄组与脑白质内囊前肢、内囊后肢、胼胝体膝部、胼胝体压部及尾状核头部5个部位的各向异性指数(FA)值、ADC值的相关性及差异性。结果:内囊前肢、内囊后肢、胼胝体膝部及胼胝体压部的FA值与年龄呈正相关,尾状核头部的FA值与年龄呈负相关;内囊前肢、内囊后肢、胼胝体膝部、胼胝体压部及尾状核头部的ADC值均与年龄呈负相关。第1、2组间及第2、3组间内囊前肢、内囊后肢、胼胝体膝部及胼胝体压部的FA值、ADC值差异均有统计学意义(均P0.05);第3、4组组间胼胝体膝部及胼胝体压部的FA值、ADC值差异均有统计学意义(均P0.05)。结论:DTI的FA值和ADC值能反映脑白质发育差异。     

颞叶癫痫患者的颞叶以外白质MR扩散张量成像研究

目的 应用MR扩散张量成像(DTI)探讨颞叶癫痫(TLE)患者的颞叶以外白质是否存在隐匿性损伤,并研究这些白质结构的DTI参数值与患者初次发病年龄及病程长短的相关性.资料与方法 对临床确诊的42例发作间期TLE患者和32名健康志愿者行常规MRI和DTI检查,定量测量胼胝体膝部、体部、压部、内囊前肢、后肢及外囊的平均扩散系数(Dcavg)和部分各向异性(FA)值并进行统计学分析.结果 TLE患者胼胝体压部、内囊后肢及外囊的Dcavg值显著高于正常人(P<0.01),胼胝体膝部、压部、内囊前肢及外囊的FA值显著低于正常人(P<0.05).TLE患者内囊后肢Dcavg值与病程长短呈正相关.结论 TLE患者的颞叶以外白质存在隐匿性损伤,内囊后肢的损伤程度与病程长短有关.     

Detection of Cerebral Microbleeding By Susceptibility Weighted Imaging Sequence and Research on Relation Between CMBs and Risk Factors

目的 探讨磁敏感加权成像(susceptibility weighted imaging sequence,SWI)检测脑微出血(cerebral microb-leeds,CMBs)的优势,并分析CMBs的相关临床危险因素及其临床意义.资料与方法 经磁共振常规序列及SWI序列检测CMBs,搜集189例患者,其中CMBs阳性者79例,且经蒙特利尔认知评估(MoCA)量表及简易智能状态检查量表(MMSE)评价CMBs阳性患者的认知功能情况.结果 SWI对CMBs的病灶检出数较常规序列明显增多;CMBs主要分布在颞叶及基底节区,高血压、糖尿病、白质严重程度、急性梗死及腔隙性梗死与CMBs的存在与否有显著性差异(P＜0.01),且CMBs阳性患者的MoCA量表总分(r=-0.86,P＜0.00)及MMSE总分(r=-0.79,P＜0.00)与CMBs总数呈明显负相关.结论 SWI较常规序列能更好地显示CMBs,具有重要的临床价值;高血压、糖尿病、白质改变、急性梗死及腔隙性梗死与CMBs的存在有密切相关性,大量CMBs与患者认知功能受损密切相关.     

Study of the Relationship Between Internal Capsule Volume and Age in Healthy Chinese Han Adults

目的 探讨中国汉族正常成人内囊体积与年龄的相关性,为内囊病变的临床诊断提供直接依据.资料与方法 选择汉族健康成人1000名,按年龄分为A(18 ～ 30岁)、B(31 ～ 40岁)、C(41 ～50岁)、D(51 ～ 60岁)、E(61 ～ 80岁)5组,每组200名,男、女各100名.对每名志愿者用1.5 TMR扫描仪进行研究,应用3D体积分析软件手动逐层勾画出内囊边界,软件自动测算出体积.结果 测量得A、B、C、D、E5组左、右侧内囊(总的、前肢、膝部、后肢)体积,将A、B、C、D、E5组左侧内囊(总的、前肢、膝部、后肢)体积分别与右侧内囊比较,经统计学检验左右侧间均有显著性差异(P＜0.05).将左、右侧内囊的体积进行标准化处理后,左、右侧内囊体积与年龄之间均呈负相关(r值分别为-0.718、-0.637,P值均＜0.05).结论 内囊体积与年龄呈负相关,即随着年龄的增大内囊体积逐渐缩小.     

急性一氧化碳中毒脑损伤的磁共振扩散张量成像

目的：利用磁共振扩散张量成像(DTI )评估急性一氧化碳(CO)中毒患者的脑结构损伤情况。方法25例急性(5.0 d±1.44 d) CO 中毒患者和37例性别、年龄、利手、受教育程度匹配的健康志愿者进行 DTI 扫描,获得扩散张量纤维束成像(DTT)图像,并分别测量双侧小脑半球(齿状核)、黑质、海马、额叶白质(侧脑室前角前下方、侧脑室体部上方)、尾状核头、苍白球、丘脑、内囊前肢、内囊后肢、枕叶白质(视中枢)、顶叶白质(侧脑室体部上方)及胼胝体膝部、压部共26个感兴趣(ROI)的各向异性分数(FA)值和表观扩散系数(ADC)值,进行组间配对 t 检验。结果病患组双侧苍白球、双侧内囊前肢、双侧黑质、右侧小脑、左侧额叶下部白质、右额叶上下部白质、胼胝体膝部的 FA 值显著低于对照组(P <0.05)。病患组右侧黑质、左侧苍白球的 ADC 值显著降低(P <0.05),病患组右额叶上下部白质及双侧枕叶白质 ADC 值显著升高(P <0.05)。结论急性 CO 中毒患者广泛脑微结构受损,提示脑微结构的原发损伤可能是 CO 中毒迟发性脑病潜在的病理生理基础。     

2个CADASIL患者的弥散张量成像与20例正常人的比较

目的　分析2例CADASIL患者的MR特点及弥散张量指标的变化。方法　收集2例通过病理和基因检查确诊为CA DASIL的先证者的临床资料,对其进行常规MR扫描和弥散张量成像,将弥散张量成像的指标与20例正常志愿者的指标进行比较。结果　2例CADASIL患者的MR主要表现为双侧额顶叶白质内多发腔梗、脱髓鞘改变和双侧颞叶前部白质脱髓鞘。1例患者双侧外囊、内囊后肢、胼胝体膝部和压部的部分各向异性(FA)值均小于正常组的平均值减去2倍标准差,另1例患者左侧外囊的FA值小于对照组的平均值减去2倍标准差。结论　常规MR表现和弥散张量成像指标的测量均反映了CADASIL患者中存在严重的白质病变。     

中国汉族正常成人内囊体积的高分辨率MRI测量

目的 测量中国正常汉族成人内囊体积,分析内囊体积与年龄、体质量及颅脑容积的相关性.方法 选择健康汉族成人志愿者1000名,按照年龄18 ～ 30、31～40、41 ～ 50、51 ～ 60、61～80岁分为5组,每组男、女各100名.所有受试者均行3D磁化强度预备梯度回波序列T1WI,应用3D体积分析软件手工勾绘ROI,测量受试者内囊体积,并进行标准化处理.双侧内囊体积间比较采用配对t检验分析,不同性别间内囊体积比较用两独立样本t检验分析,不同年龄段之间内囊体积的比较采用单因素方差分析,并对内囊体积和年龄、体质量、颅脑容积的相关性做积差相关分析.结果 1000名受试者左、右侧内囊体积分别为(2809±393)、(2677±343) mm3,左侧大于右侧(t=12.078,P＜0.05).男性左、右侧内囊体积分别为(2863±396)、(2744±358)mm3,女性分别为( 2754±385)、( 2609±314 )mm3,男性左、右侧内囊体积均大于女性(t值分别为1.982、2.851,P值均＜0.05).5组上述不同年龄志愿者左侧内囊体积分别为(3273±361)、(2943±299)、(2777±255)、(2607±199)、(2444±213)mm3,右侧分别为(2993±361)、(2814±270)、(2682±239)、(2543±219)、(2351±210)mm3,5组间左、右侧内囊体积差异均有统计学意义(F值分别为55.244、34.493,P值均＜0.05).左、右侧内囊体积均与年龄呈负相关(r值分别为-0.718、-0.637,P值均＜0.05).结论1.5 TMR扫描仪能明确辨别内囊的边界,精确测量内囊体积;内囊体积与年龄呈负相关.     

儿童异染性脑白质营养不良的MRI表现

目的 观察异染性脑白质营养不良（MLD）的特征性表现。方法 回顾分析我院经生化检查证实的MLD共11例,观察MRI上脑内白质病变的部位和特殊结构（白质纤维束、丘脑、胼胝体）受累的情况。结果 11例均表现为双侧脑室周围白质T2WI对称高信号,10例双侧半卵圆中心T2WI对称高信号;4例累及皮层下白质。8例累及胼胝体膝部,9例累及压部,两者同时受累为8例;7例累及内囊后肢,4例累及外囊,4例累及脑干皮质脊髓束（3例中脑,1例桥脑）。1例累及小脑白质,8例半卵圆中心T2WI有虎纹征,8例T2WI丘脑呈低信号;5例侧脑室扩大,1例全脑萎缩。结论 MLD的典型表现为双侧半卵圆中心和侧脑室周围白质T2WI对称高信号,早期皮层下白质不受累,胼胝体膝部和压部受累为重要征象;另外征象包括脑干皮质脊髓束和内、外囊受累及虎纹征。     

佩梅病的头颅MRI表现及其与临床、基因分型的关系

目的 探讨佩梅病( PMD)患儿的头颅MRI特点,以及与临床及基因分型的关系.方法 回顾性分析16例经临床诊断为佩梅病患儿的临床和影像资料.患儿均为男性,年龄5个月至9岁8个月.由儿科神经医师对患儿的症状和体征进行检查,将其按照临床症状进行临床分型.由影像科医师对头颅MRI图像的特点进行分析,病灶的位置包括苍白球、锥体束、胼胝体、小脑白质、半卵圆中心,判断大、小脑是否萎缩、是否有“豹纹征”.结果 临床诊断经典型佩梅病8例,中间型7例,先天型1例.16例佩梅病患儿MRI均以广泛的脑白质髓鞘化延迟为特点,病灶累及苍白球13例、锥体束7例、胼胝体11例、小脑白质7例、半卵圆中心12例、脑萎缩5例、小脑萎缩1例,5例有“豹纹征”.锥体束和小脑白质受累在点突变患儿中多见;临床症状较重的中间型及先天型患儿出现小脑白质病变频率较高;“豹纹征”多见于经典型患儿,提示患儿的髓鞘化程度相对较高.结论 佩梅病患儿的头颅MRI具有典型的影像特点,其影像学表现与临床分型和基因突变类型有一定的相关性.     

Cerebral White Matter in the Centrum Semiovale Exhibits a Larger N-acetyl Signal than Does Gray Matter in Long Echo Time 1H-Magnetic Resonance Spectroscopic Imaging

Long echo time (272 ms) ¹H magnetic resonance spectro-scopic imaging was used to measure the relative magnitudes of the N-acetylaspartate (NAA) signal in a variety of anatomically defined brain structures (centrum semiovale, thalamus, medial frontal cortex, and genu of the corpus callosum) composed primarily of gray matter or white matter. Six normal young adult humans aged 30–40 were studied. With a 95% level of statistical confidence, the white matter in the centrum semiovale (CSO) produced a more intense NAA signal than did the gray matter in the thalamus and the frontal cortex. Differences between the white matter regions were also noted. The CSO white matter's NAA signal yielded a larger NAA signal than did the white matter of the genu of the corpus callosum. Possible reasons for the anatomical variation in the cerebral NAA signal intensity are discussed.     

常染色体显性遗传性脑动脉病伴皮层下梗死和白质脑病的颅脑MRI表现

目的 提高对常染色体显性遗传性脑动脉病伴皮层下梗死和白质脑病(CADASIL)的颅脑MRI表现的认识.方法 对一家系2代5例患者进行头颅常规MR和MR血管成像(MRA)检查.对经Notch3基因检查或皮肤组织活检超微病理检查确诊的3例和经MRI与临床诊断的1例CADASIL的MRI资料进行分析.结果 MR检查的5例中4例CADASIL均获得明确诊断,1例排除诊断.4例CADASIL均见两侧颞叶、额叶和顶叶大致对称性皮层下与侧脑室旁白质病灶,呈长T1、长T2信号,但枕叶累及甚少且皮层不受累;O'Sullivan征阳性4例,皮层下腔隙性损害(SLLs)征阳性2例;3例半卵圆中心可见多发圆形或卵圆形囊性梗死即"黑洞",4例均见多发圆点状血管周间隙即"胡椒罐盖"样征象;4例全部显示胼胝体单发或多发斑片状显著长T1、长T2信号,其中2例伴萎缩;内囊前肢与外囊均受累,呈"人"字征;基底节和脑干可见单发或多发陈旧性腔隙性梗死灶;1例伴右侧小脑小片状梗死灶;4例全部有轻度至中度的脑干、小脑和大脑萎缩;MRA颅内Ⅰ-Ⅲ级较大动脉均未见明显异常.结论 CADASIL的颅脑MRI表现具有一定的特征性,可为CADASIL的初诊和筛选提供重要依据.     

MR of childhood metachromatic leukodystrophy.

PURPOSETo investigate the MR findings of childhood metachromatic leukodystrophy (MLD).METHODSNine MR imaging studies in seven children (five girls and two boys, 10 to 32 months old) with MLD were evaluated retrospectively for the extent and progression of white matter abnormalities and the presence of contrast enhancement.RESULTSAll seven cases showed symmetric, confluent high signal intensity on T2-weighted images in the periventricular white matter and centrum semiovale. A posterior predominance of white matter abnormalities was noted in all cases. Although initially spared from demyelination in all cases, in one case, the subcortical U fibers were later involved in demyelination of follow-up MR studies. Other sites of involvement were the genu (n = 5) and splenium (n = 6) of the corpus callosum, the posterior limbs of the internal capsule (n = 5), the descending pyramidal tracts (n = 4), the claustrum (n = 4), and the cerebral white matter (n = 2); diffuse brain atrophy was seen in two cases. No enhancement of the lesion was seen on any of the five postcontrast examinations. A "tigroid" pattern, previously described in cases of Pelizaeus-Merzbacher disease, was noted in the centrum semiovale in six cases.CONCLUSIONIn late-infantile MLD, demyelination is more prominent in the occipital region. In addition to demyelination of the periventricular white matter, common manifestations include a "tigroid" pattern and involvement of the corpus callosum, the internal capsule, and the corticospinal tract.     

Acute and chronic brain infarcts on MR imaging in a 20-year-old woman with acute posterior multifocal placoid pigment epitheliopathy

A 20-year-old woman recently diagnosed with acute posterior multifocal placoid pigment epitheliopathy developed headaches, weakness, and paresthesias. MR imaging of the brain revealed an acute infarct (demonstrated by diffusion-weighted images) in the head of the right caudate nucleus, a chronic infarct with encephalomalacia in the body of the corpus callosum, and multiple foci of abnormal signal intensity in the white matter of the centrum semiovale.     

遗传性弥漫性脑白质病变合并轴索球样变的磁共振特征附2例报告

目的探讨遗传性弥漫性脑白质病变合并球状轴索(HDLS)的磁共振特点,以加深对该病的理解和认识。方法报道2例确诊为集落刺激因子1受体基因突变的HDLS患者的临床诊疗经过,结合文献对其磁共振不同序列的影像学特征进行讨论及分析。结果2例均为青年,慢性起病,亚急性进展,临床表现为体重减轻,口齿不清,反应迟钝,近记忆力减退及肢体运动功能障碍。头颅MRI表现为双侧侧脑室旁、半卵圆中心对称性白质病变、DWI显示弥散受限,MRS提示病变区域NAA峰减低,Cho峰增高,2例均有不同程度脑萎缩,以顶叶及胼胝体体部较明显。结论HDLS为罕见疾病,临床表现多样,容易误诊,双侧侧脑室体旁、半卵圆中心区多发持续性DWI高信号伴有Cho峰增高为本病较特异性的影像学表现,有助于HDLS的早期诊断。     

Evaluation of brain metabolism in steno-occlusive carotid artery disease by proton MR spectroscopy: a correlative study with oxygen metabolism by PET.

Carotid occlusive diseases may cause ischemic changes in both the gray matter and the white matter as a result of hemodynamic compromise. To validate the use of proton magnetic resonance spectroscopy (MRS) in evaluating the carotid occlusive diseases, we compared changes in peaks of choline, in the sum of creatine and phosphocreatine, and in N-acetyl-aspartate (NAA) of the white matter with cortical oxygen metabolism measured by PET. METHODS: Eleven patients with unilateral steno-occlusive carotid artery disease underwent PET and MRS. Ten age-matched healthy volunteers underwent MRS. No subjects had cortical infarction. MRS was performed bilaterally in the centrum semiovale. Regional blood flow, regional metabolic rate of oxygen (rCMRO2), and regional oxygen extraction fraction (rOEF) of the cerebral cortex were measured by the steady-state method with 15O gas. RESULTS: The asymmetry index of the ratio of NAA to the sum of creatine and phosphocreatine (NAA/Cr) correlated positively with the asymmetry index of rCMRO2 (r = 0.77; P < 0.01). Because rCMRO2 is a marker of tissue viability, the NAA/Cr of the centrum semiovale may reflect viable neuronal cells. The asymmetry index of the ratio of choline to the sum of creatine and phosphocreatine (Cho/Cr) showed a significant positive correlation with the asymmetry index of rOEF (r = 0.65; P < 0.05). All but 1 patient with an increased Cho/Cr (>1.03) showed an increase in rOEF of the ipsilateral cortex (>0.56). This finding may indicate membrane damage caused by ischemia, because the centrum semiovale is the deep watershed zone. CONCLUSION: The metabolic changes in the centrum semiovale detected by proton MRS reflect a hemodynamically compromised state and are useful in evaluating tissue viability.     

T2 relaxation values in the developing preterm brain

BACKGROUND AND PURPOSE: MR imaging is increasingly used to assess maturation and disease in the preterm brain. Knowledge of the changes in T2 values with increasing postmenstrual age (PMA) will aid image interpretation and help in the objective assessment of maturation and disease of the brain in infants. The aim of this study was to obtain T2 values in the preterm brain from 25 weeks' gestational age (GA) until term-equivalent age in infants who had normal neurodevelopmental findings at a minimum corrected age of 1 year. METHODS: The study group consisted of 18 preterm infants, born at 33 weeks' GA or sooner. The median GA of the infants at birth was 27 weeks (range, 23-33 weeks), and the median PMA at imaging was 31 weeks (range, 25-41 weeks). T2 measurements were obtained using a 1.0-T MR system and a four-echo pulse sequence (TR/TE, 2500/ 30, 60, 110, and 600). T2 values were measured in the thalami, lentiform nuclei, frontal white matter, occipital white matter, and central white matter at the level of the centrum semiovale. RESULTS: A significant negative linear correlation between T2 values and PMA was demonstrated in the lentiform nuclei (P =.003), frontal white matter (P <.0001), occipital white matter (P <.0001), and central white matter at the level of the centrum semiovale (P <.0001). T2 values were not significantly reduced with increasing PMA in the thalami (P =.06). CONCLUSION: T2 values decrease with increasing PMA in the preterm brain.     

老年人皮质下动脉硬化性脑病的病理学基础和CT,MRI对照研究

本文就２６例皮质下动脉硬化性脑病患者的ＣＴ、ＭＲＩ检查结合病理学基础进行了分析。ＭＲＩ检查，当ＴＲ＝２０００ｍｓｅｅ，ＴＥ＝３０、６０ｍｓｅｃ时，皮质动脉硬化性脑病损害均为明显的高信号，Ｔ１加权像为低信号。ＣＴ像为低密度改变。Ｔ２加权像上半卵圆中心的白质表现为不均匀弥漫的高信号区，可累及基底节、丘脑、脑干及小脑的白质，并有不同程度的侧脑室扩大、脑室边缘呈斑片状改变可有脑萎缩。病理学特征是弥漫不完全