CT冠状动脉成像与冠状动脉导管造影评估冠状动脉钙化所致狭窄程度的一致性

目的 探讨CT冠状动脉成像(CTCA)与冠状动脉导管造影(ICA)评估冠状动脉钙化狭窄程度的一致性。方法 选取接受CTCA和ICA、且图像无明显伪影的45例冠状动脉钙化狭窄患者;分别测量其病灶处钙化CT值、血管CT值,计算二者的CT比值,即血管钙化CT比值=病灶周围钙化最高CT值/病灶周围血管近端无钙化层面的血管CT值。以所用患者血管钙化CT比值的总平均值为分界值,将病例分为A、B两组。分别比较两组中CTCA与ICA诊断冠状动脉钙化狭窄程度的一致性。结果 45例患者血管钙化CT比值的总平均值为3.04±0.89;A组血管钙化CT比值<3.04,共21例,CTCA与ICA对其狭窄程度评估的吻合率为95.24%(20/21),诊断一致性极好(Kappa=0.82,P<0.05);B组血管钙化CT比值≥3.04,共24例,CTCA与ICA对其狭窄程度评估的吻合率为37.50%(9/24),诊断一致性差(Kappa=0.172,P<0.05)。结论 当血管钙化CT比值<3.04时,采用CTCA评估冠状动脉钙化狭窄程度,与ICA的评估结果具有较好的一致性。     

MSCT测量心外膜脂肪体积与零钙化积分冠心病的相关性

目的 评价应用64层MSCT所测心外膜脂肪(EAT)体积与零钙化积分(CACS)冠心病的相关性.方法 回顾性分析接受冠状动脉CTA检查的零CACS患者102例,根据CTA结果分为冠心病和非冠心病患者,记录患者性别、年龄、体质量指数(BMI)以及高血压、糖尿病和血脂代谢异常病史.采用MSCT测量EAT体积,评价EAT体积与冠心病发生的相关性.结果 102例患者中,冠心病18例(18/102,17.65%)、非冠心病84例(84/102,82.35%).零CACS冠心病患者EAT体积为(144.60±36.23)cm³,明显高于非冠心病患者 (P<0.001);EAT体积诊断零CACS冠心病的ROC曲线下面积为0.76,诊断界值为120.82 cm³,该界值下诊断敏感度为72.2%,特异度为65.5%;Logistic回归分析显示,校正心血管危险因素后,EAT体积为零CACS冠心病的独立危险因素(OR=1.02,P=0.027).结论 EAT体积与零CACS冠心病的发生有关,可作为评估零CACS冠心病风险的一个非创伤性指标.     

双源CT冠状动脉成像评价冠状动脉狭窄

目的 评价双源CT冠状动脉成像(DSCTA)诊断冠状动脉狭窄的价值。方法 回顾性分析41例临床疑似冠心病或已经确诊的冠心病患者的DSCTA和CAG检查资料。以CAG结果为金标准,计算DSCTA诊断轻度(管腔狭窄＜50%)、中度(管腔狭窄50%~75%)、重度(管腔狭窄≥75%)冠状动脉狭窄及DSCTA诊断冠状动脉狭窄的总体敏感度、特异度、阳性预测值、阴性预测值及准确率。结果 41例患者共546个直径≥1.5 mm的冠状动脉节段中535个满足诊断要求,其余11个因钙化斑块遮蔽管腔而无法诊断。DSCTA诊断轻度、中度、重度冠状动脉狭窄敏感度、特异度、阳性预测值、阴性预测值及准确率分别为69.23%(36/52)、96.60%(341/353)、75.00%(36/48)、95.52%(341/357)、93.09%(377/405),68.42%(26/38)、99.42%(341/343)、92.86%(26/28)、96.60%(341/353)、96.33%(367/381),70.67%(53/75)、99.71%(341/342)、98.15%(53/54)、93.94%(341/363)、94.48%(394/417),诊断冠状动脉狭窄的总体敏感度、特异度、阳性预测值、阴性预测值及准确率分别为64.61%(115/178)、95.52%(341/357)、87.79%(115/131)、84.41%(341/404)、85.23%(456/535)。结论 作为一种无创性检查手段,DSCTA对评价冠状动脉狭窄程度具有较高的准确性。     

64排CT冠状动脉成像诊断冠状动脉狭窄的临床价值

目的 评价64排CT冠状动脉成像(CTCA)技术诊断冠状动脉显著狭窄(≥50%管腔狭窄)的临床价值.方法 采用CTCA对61例临床疑诊冠心病患者进行检查,并于CTCA检查后2周内行选择性冠状动脉造影(SCA).结果 1例患者因冠状动脉严重钙化4支血管CTCA不可评估,其余60例患者240支冠状动脉血管CTCA均可良好显影,240支血管显著狭窄诊断的灵敏度、特异度、阳性预测值及阴性预测值分别为90.0%(72/80)、91.9%(147/160)、84.7%(72/85)、94.8%(147/155).结论 CTCA显示了较高的阴性预测值,可以作为排除冠状动脉显著病变的一种无创标准性检查.     

PET/CT心肌灌注显像联合冠状动脉CTA诊断冠心病

目的 评价PET/CT心肌灌注显像(MPI)联合冠状动脉CTA(CTCA)诊断冠心病的准确性。方法 检索2001-2011年有关PET/CTCA诊断冠心病的原始研究,经过质量评价后对符合纳入标准的文献进行数据提取,并行Meta分析和亚组分析,绘制森林图和拟合ROC曲线。结果 纳入6篇文献(252例),按照随机效应模型合并后,MPI/CTCA、单独MPI和单独CTCA(段)的诊断敏感度(SEN)、特异度(SPE)、阳性预测值(PPV)、阴性预测值(NPV)、诊断比值比(DOR)、诊断准确率(ACC)及曲线下面积(AUC)分别为0.91(95%CI 0.84~0.96)、0.91(95%CI 0.84~0.96)和0.87(95%CI 0.80~0.92),0.99(95%CI 0.96~1.00)、0.91(95%CI 0.84~0.96)和0.91(95%CI 0.88~0.94),0.95(95%CI 0.82~1.00)、0.94(0.86~1.00)和0.85(0.59~0.92),0.93(0.88~0.99)、0.84(0.78~0.97)和0.91(0.69~1.00),381.23(95%CI 98.04~1482.48)、113.20(95%CI 36.39~352.19)和73.59(95%CI 35.70~151.69),0.9671、0.9638和0.9575。结论 MPI/CTCA较单独MPI或单独CTCA无绝对优势,但鉴别冠状动脉痉挛所致MPI假阳性与代偿期冠状动脉狭窄所致MPI假阴性优势互补。     

心肌二维跨壁纵向应变诊断冠状动脉狭窄程度

目的 探讨采用二维斑点追踪成像(STI)技术检测心肌跨壁纵向应变诊断冠状动脉狭窄程度的价值.方法 对31例可疑冠心病患者行超声心动图检查和CT冠状动脉造影(CTCA),根据CTCA结果将心肌节段分为正常心肌组、轻度狭窄心肌组、中度狭窄心肌组、重度狭窄心肌组,测量心内膜下心肌纵向应变(LS-endo)、心外膜下心肌纵向应变(LS-epi)及整体心肌纵向应变(LS-global),计算跨壁纵向应变(LS-mural);比较4组心肌间各纵向应变参数差异.结果 正常心肌组和轻度狭窄心肌组各应变参数差异无统计学意义(P均>0.05),均大于中度狭窄心肌组及重度狭窄组(P均<0.001);重度狭窄心肌组LS-endo、LS-epi及LS-global小于中度狭窄心肌组(P均<0.001).以-2.42%为界值,LS-mural诊断中度冠状动脉狭窄的敏感度及特异度分别为51.6%和56.5%     

64层螺旋CT冠状动脉成像诊断心率≥70次/分或心律不齐患者冠状动脉狭窄病变

目的 评价64层螺旋CT冠状动脉成像(MSCTCA)对心率≥70次/分或心律不齐患者冠状动脉狭窄病变诊断的准确性。 方法 对临床诊断和疑诊冠心病的心率≥70次/分或心律不齐患者51例(研究组)及窦性心律且心率＜70次/分者40例(对照组),在1个月内完成MSCTCA和DSA检查。以DSA为标准,评价MSCTCA对研究组患者冠状动脉狭窄病变诊断的准确性。 结果 研究组MSCTCA检出冠状动脉轻度狭窄的敏感度、准确率、特异度、阳性预测值及阴性预测值分别为52.73%(29/55)、78.02%(142/182)、88.98%(113/127)、67.44%(29/43)、81.29%(113/139),中度狭窄为62.50%(30/48)、87.82%(137/156)、99.07%(107/108)、96.77%(30/31)、85.60%(107/125),重度狭窄为69.89%(65/93)、90.07%(263/292)、99.50%(198/199)、98.48%(65/66)、87.61%(198/226)。MSCTCA与DSA检出冠状动脉不同狭窄程度的总节段数差异无统计学意义(χ²=0.859,P＞0.05);两种方法在检出冠状动脉狭窄方面显著相关(r=0.731,P＜0.01)。 结论 与DSA相比,MSCTCA评价心率较高、心律不齐患者冠状动脉狭窄病变的敏感度虽然偏低,但采用适当的扫描和后处理技术后有较高的准确率和特异度,与DSA相关性较好,能满足临床筛选介入治疗冠状动脉狭窄适应证的需要。     

320排容积CT低管电压结合低浓度对比剂冠状动脉成像与冠状动脉造影的对比研究

目的 探讨320排容积CT冠状动脉CTA低管电压、低浓度对比剂扫描的可行性。方法 前瞻性分析54例临床疑似冠状动脉粥样硬化性心脏病患者的CCTA检查结果,并与经导管冠状动脉造影术(CCA)结果进行对照。CCTA采用100 kV管电压,对比剂采用270 mgI/ml的碘克沙醇。结果 CCTA显示冠状动脉中度以上狭窄(≥50%)及重度狭窄(≥75%)的敏感度、特异度、阳性预测值、阴性预测值、正确指数及符合率分别为89.55%、96.08%、78.95%、98.25%、85.63%、96.84%及92.68%、97.24%、76.00%、99.29%、89.92%、95.16%。CCTA与CCA在显示冠状动脉狭窄程度方面的一致性良(Kappa=0.752,P<0.001)。CCTA诊断冠状动脉中度以上狭窄(≥50%)的ROC曲线下面积为0.930。结论 应用320排容积CT行CCTA低管电压、低浓度对比剂扫描诊断冠状动脉狭窄具有可行性。     

MSCT评价冠状动脉软斑块狭窄程度与左心室收缩功能

目的 探讨MSCT在评价冠状动脉软斑块狭窄的同时测定左心室功能的临床应用价值。方法 回顾性分析232例接受MSCT冠状动脉造影的患者,包括46例单纯软斑块致冠状动脉狭窄(软斑块组,又分为轻、中、重度狭窄组)和186例冠状动脉正常者(正常组)。以测量血管直径法,按照冠状动脉狭窄程度分为I~Ⅳ组,并计算左心室舒张末期容积(EDV)、左心室收缩末期容积(ESV)、左心室每搏输出量(SV)、左心室射血分数(EF)。结果 轻度、中度狭窄组与正常组间EF的差异无统计学意义,其他组间差异有统计学意义(P＜0.01);轻度狭窄组、中度狭窄组与正常组间ESV值差异性无统计学意义,其他组间差异有统计学意义(P＜0.01);EDV、SV、心率组间差异无统计学意义(P＞0.05)。结论 冠状动脉CTA可评估冠状动脉狭窄情况。当冠状动脉管径狭窄＞50%时,左心室收缩功能有不同程度下降;当冠状动脉管径狭窄＞75%时,左心室收缩功能下降明显。MSCT可准确、可靠地定量评价冠状动脉硬化狭窄及左心室收缩功能。     

3.0TMR自动呼吸导航对比增强全心冠状动脉磁共振血管成像的临床应用

目的 评价3.0T MR自动呼吸导航全心冠状动脉磁共振血管成像(CMRA)诊断冠状动脉狭窄的临床应用价值.方法 对50例临床疑诊或确诊冠心病或心肌病的患者行自动呼吸导航对比增强CMRA,其中33例经冠状动脉造影(CAG)证实.评价CMRA图像质量,并与CAG相对照,评价CMRA诊断冠状动脉狭窄的效能.结果 1例CMRA图像质量较差,为1级;余49例CMRA图像质量均满足诊断要求,为2~4级.33例经CAG证实的患者共286段血管中,CRMA可显示238段(238/286,83.22%),未显示48段(48/286,16.78%).以患者数、血管支和血管段为单位,CMRA诊断冠状动脉狭窄的敏感度分别为80.95%(17/21)、79.31%(23/29)、84.62%(33/39),特异度分别为75.00%(9/12)、91.09%(92/101)、75.00%(33/44),阳性预测值(PPV)分别为85.00%(17/20)、71.88%(23/32)、75.00%(33/44),阴性预测值(NPV)分别为69.23%(9/13)、93.88%(92/98)、96.91%(188/194),准确率分别为78.79%(26/33)、88.46%(115/130)、92.86%(221/238).结论 3.0T MR自动呼吸导航对比增强全心CMRA有助于诊断冠状动脉狭窄.     

Deriving coronary artery calcium scores from CT coronary angiography: a proposed algorithm for evaluating stable chest pain

We validate a method of calcium scoring on CT coronary angiography (CTCA) and propose an algorithm for the assessment of patients with stable chest pain. 503 consecutive patients undergoing coronary artery calcium score (CACS) and CTCA were included. A 0.1 cm² region of interest was used to determine the mean contrast density on CTCA images either in the left main stem (LM) or right coronary artery. Axial 3 mm CTCA images were scored for calcium using conventional software with a modified threshold: mean LM contrast density (HU) + 2SD. A conversion factor (CF) for predicting CACS from raw CTCA scores (rCTCAS) was determined using a multivariable regression model adjusted for model over-optimism (1,000 bootstrap samples). Accuracy of this method was determined using weighted kappa for NICE recommended CACS groupings (0, 1–400, >400) and Bland–Altman analysis for absolute score. With the CF applied: CACS = (1.183 × rCTCAS) + (0.002 × rCTCAS × threshold), there was excellent agreement between methods for absolute score (mean difference 5.44 [95 % limits of agreement ?207.0 to 217.8]). The method discriminated between high (>400) and low risk (<400) calcium scores with a sensitivity and specificity of 85 and 99 %, and a PPV and NPV of 92 and 98 %, respectively, and led to a significant reduction in radiation exposure (6.9 [5.1–10.2] vs. 5.2 [6.3–8.7] mSv; p < 0.0001). Our proposed method allows a comprehensive assessment of coronary artery pathology through the use of an individualised, semi-automated approach. If incorporated into stable chest pain guidelines the need for further functional testing or invasive angiography could be determined from CTCA alone, supporting a change to the current guidelines.     

Coronary artery ectasia diagnosed using multidetector computed tomography: morphology and relation to coronary artery calcification

Coronary artery ectasia (CAE) is usually considered a variant of coronary artery atherosclerosis; however, a definite link has not yet been confirmed. As not all patients with CAE are symptomatic, the real incidence is unknown. The aim of this study was to evaluate the prevalence of CAE and its clinical and angiographic characteristics as well as its relation to coronary artery calcification and any associated vascular abnormality by using multidetector computed tomography (MDCT). We prospectively enrolled 2,600 patients (mean age 55 ± 10 years) who were scheduled for computed tomography coronary angiography (CTCA). CTCA was performed using 64-MDCT with dedicated software for calcium measurement. CAE was defined as an arterial segment with a diameter of >1.5 times the diameter of the adjacent normal segment. The presence of ≥70 % diameter stenosis of any major epicardial vessel was considered an obstructive lesion. CAE was encountered in 192 (7.4 %) patients and showed gender predominance in men (88 %). Patients with CAE were more hypertensive but less diabetic. Left anterior descending artery was the most commonly affected vessel. Only 16 % of CAE patients had no atherosclerotic lesion. Coronary artery calcium score (CACS) and prevalence of ascending aorta aneurysm were shown to be significantly higher in CAE patients compared to patients having no ectasia. A significant negative correlation was noted between CACS and Markis classification. CTCA is a feasible technique to identify and evaluate morphology of CAE. The link between CACS and CAE may favor the consideration that ectasia is an advanced form of atherosclerosis.     

The presence,characterization and prognosis of coronary plaques among patients with zero coronary calcium scores

Patients with coronary artery calcium (CAC) scores of zero are generally considered not to have atherosclerosis. Recent studies involving computed tomography coronary angiography (CTCA) challenge this assumption. This goal of the present study is to assess the frequency, morphology, location, and the prognosis of patients with plaque detected on CTCA and zero CAC. 1,119 patients (51 ± 12 years, 52% male) with a zero CAC score during CTCA study were retrospectively identified. The CTCA studies were assessed for the presence, morphology, location and severity of all coronary plaques. All-cause mortality was assessed. The prevalence of coronary plaque was 13% (147 patients). Among the 212 plaques identified 154 (73%) were non-calcified, 28 (13%) were calcified, and 30 (14%) were of mixed morphology. Notably, ≥70% stenosis was noted among only 0.4% of all patients. ROC analysis revealed that coronary artery disease risk factors did not add to the prediction of plaque among our patients. Over a mean follow-up of 2.5 ± 0.6 years there were 4 deaths (0.4%), all in patients without coronary plaque on CTCA. The presence of coronary plaque is not uncommon among patients with zero CAC scores. These plaques were rarely associated with hemodynamically significant stenoses and were associated with an excellent prognosis. Clinical factors do not appear to be useful in predicting which patients with zero CAC scores have undetected coronary plaque.     

320排CT血管成像对冠状动脉瘘的诊断价值

目的探讨320排CT血管成像对冠状动脉瘘的诊断价值。方法回顾性分析34例冠状动脉瘘患者的320排CT血管成像资料及临床资料,其中11例患者同时进行冠状动脉造影检查。结果 26 590例患者中共34例诊断为冠状动脉瘘,发病率为0.13%。34例冠状动脉瘘中冠状动脉-肺动脉瘘26例(76.5%),冠状动脉-左心室瘘3例(8.8%),冠状动脉-右心房瘘3例(8.8%),冠状动脉-左心房瘘1例(2.9%),冠状动脉-右心室瘘1例(2.9%)。起源于左冠状动脉8例(23.5%),起源于右冠状动脉10例(29.4%),同时起源于两侧冠状动脉者16例(47.1%)。16例(47.1%)伴随瘤样扩张。瘘口直径范围2.0~13.0 mm,中位直径2.5 mm。瘘口两端见浓染征15例(44.1%),射血征10例(29.4%),等密度征9例(26.5%)。11例均经冠状动脉造影证实为冠状动脉瘘。结论冠状动脉瘘发病率低,其中冠状动脉-肺动脉瘘是最常见的类型(占76.5%),同时起源于两侧冠状动脉占47.1%。320排CT血管成像能无创、准确地显示冠状动脉瘘的起源、瘘血管走行、瘘口直径及引流部位,可作为诊断冠状动脉瘘的首选检查方法。     

64排螺旋CT对伴有钙化的冠状动脉狭窄诊断准确性的多中心研究

评价64排螺旋CT在不同情况下对冠状动脉钙化病变所致狭窄的诊断准确性. 方法 收集165例经CT冠状动脉成像(CTCA)检查发现冠状动脉钙化并至少1个主要分支狭窄＞50%的患者,分别以个体、冠状动脉主支、节段、病变狭窄程度及钙化斑块形态为分析对象,测量Agatston积分(ACS)和狭窄率.以冠状动脉造影(CAG)作为标准,通过绘制ROC曲线来判定不同情况下CTCA的诊断价值并确定最佳的诊断切点. 结果 以个体为分析对象,ROC曲线下面积为0.791,以ACS值113.5为切点时诊断准确性最高.以冠状动脉主支为分析对象,对右冠状动脉及其属支狭窄的诊断效果最佳,ROC曲线下面积为0.897.以冠状动脉节段为分析对象,对RCA1段狭窄诊断准确性最高,ROC曲线下面积为0.894.以钙化斑块形态为研究对象,ROC曲线下面积仅在0.601～0.667之间,诊断价值较低.CTCA对狭窄程度＜50%的狭窄诊断价值较大,曲线下面积为0.856. 结论 CTCA中,钙化对不同主支、不同节段及不同狭窄程度冠状动脉狭窄的诊断准确性影响不同;钙化斑块的形态不是影响诊断准确性的主要因素.     

Significance of noncalcified coronary plaque in asymptomatic subjects with low coronary artery calcium score: assessment with coronary computed tomography angiography

We aimed to investigate the prevalence and severity of noncalcified coronary plaques (NCP) using coronary CT angiography (CCTA) and analyze predictors of significant coronary stenosis by NCP in asymptomatic subjects with low coronary artery calcium score (CACS). The institutional review board approved this retrospective study and all patients gave written, informed consent. The presence of plaque, severity of stenosis, plaque characteristics, and CACS were assessed in 7,515 asymptomatic subjects. We evaluated the prevalence and severity of NCP in subjects having low CACS (707 subjects; men with CACS from 1 to 50 and women from 1 to 10) in comparison to those having 0 CACS (6,040 subjects) as the reference standard. Conventional risk factors were assessed for predictors of NCP and significant stenosis by NCP. We also investigated the cardiac events of the patients through medical records. Compared to subjects with 0 CACS, those with low CACS showed higher prevalence of NCP (6.9% vs. 31.5%, P < 0.001) and significant stenosis caused by NCP (0.8% vs. 7.5%, P < 0.001). In the low CACS group, independent predictors for significant NCP included diabetes mellitus (DM), hypertension, and elevated low-density lipoprotein (LDL)-cholesterol (all P < 0.05). However, 47.2% of subjects with significant NCP were classified into the low to intermediate risk according to Framingham Risk Score. At the median follow up of 42 months (range: 3-60 months), cardiac events were significantly higher in the low CACS group compared to the 0 CACS group (2.6% vs. 0.27%, P < 0.001). In asymptomatic subjects having low CACS, the prevalence and severity of NCP were higher as compared to subjects having zero CACS and predictors of significant stenosis by NCP were DM, hypertension and LDL-Cholesterol. Therefore, CCTA may be useful for risk stratification of coronary artery disease as added value over CACS in selected populations with low CACS who have predictors of significant NCP.     

64排螺旋CT心肌灌注显像评价冠状动脉狭窄对心肌缺血的诊断效能

目的 利用99mTc-MIBI心肌灌注显像(MPI)探讨64排螺旋CT冠状动脉造影(CTCA)发现的冠状动脉狭窄对心肌缺血的诊断效能.方法 30例患者接受MPI和CTCA检查.将CTCA三支冠状动脉分为12段,以MPI为诊断标准,分别以CTCA血管狭窄≥50%和≥75%为截断值,统计对应节段MPI是否出现异常,分析CTCA诊断的冠状动脉狭窄对心肌缺血的效能评价.结果 MPI发现灌注异常9例(6例可逆性,3例固定性血流灌注减低).CTCA共分析327个冠状动脉节段,其中狭窄≥50%者占25段(7.65%);狭窄≥75%者12段(3.67%).以MPI异常为标准观察病变血管,以狭窄≥50%为界值时,CTCA的敏感性、特异性、阴性预测值(NPV)、阳性预测值(PPV)和准确性分别是68.42%、96.14%、99.01%、52.00%和95.41%;以狭窄≥75%为界值,则分别为66.67%、99.04%、98.73%、66.67%、97.55%.以MPI异常为标准观察患者,当血管狭窄≥50%为界值时,CTCA 的敏感性、特异性、NPV、PPV和准确性分别是66.67%、57.14%、80.00%、40.00%和60.00%;当≥75%为界值时,上述指标分别是55.56%、85.71%、81.82%、62.50%和76.67%.结论 正常CTCA对心肌缺血患者的排查是可靠的,CTCA异常是否存在心肌缺血需要进一步检查.     

成人冠状动脉瘘的CT血管成像特点

目的 探讨冠状动脉瘘(CAF)的CT血管成像特征。方法 分析45例接受DSCT (31例)及256 iCT(14例)成像CAF患者的图像质量、辐射剂量及影像学特征。结果 45例CAF患者的CTCA图像质量均满足诊断需要,平均有效剂量为(12.92±3.73)mSv。CAF起自左冠状动脉23例、右冠状动脉13例、起自两者7例,起自右冠状动脉及支气管动脉1例,起自右冠状动脉及头臂干1例。CAF单一瘘管33例,多发瘘管12例。瘘入右心系统共40例,其中瘘入肺动脉31例、冠状窦4例、右心房3例、右心室1例、上腔静脉1例;瘘入左心系统5例,其中瘘入左心房2例、左心室2例、肺静脉1例。瘘血管可有纡曲、血管丛样、扩张或动脉瘤形成等表现。结论 CTCA检查可无创、准确地显示CAF的部位、走行及并发畸形,可作为临床诊断CAF的首选检查方法。