肺血管流动参数的CT相关测量研究

目的：探讨活体肺血管分支几何学和流动状态参数的特征。方法：在63例正常人胸部螺旋CT图像上测量20l0套两分支的血管横径，计算Z值和雷诺数，分析并判断不同横径血管内血液的流动状态。结果：Z值与标本数据比较有显著不同；雷诺数随血管横径的增大而增大，但不超过l000。结论：2—4mm的正常肺小血管内雷诺数＜l000，流动为层流。     

多层面螺旋CT血管成像应用参数优化

目的 探讨多层面螺旋CT血管成像(MSCTA)中扫描参数和重建方法的影响。资料与方法 60例共120次MSCT扫描，Marconi Mx8000型4层CT扫描仪，分别将准直层厚5．0mm、2．5mm、1．0mm与PitchO．875、1．25、1．75相匹配，各组数据分别以0％、50％、70％重叠重建率，对容积再现(VR)重建血管图像的图像质量和血管分支级数显示评分，不同层厚、重叠重建率和Pitch分组比较，将准直层厚2．5mm、1．0mm组，重叠50％重建68次血管成像行最大密度投影(MIP)重建，与对应VR图像行配对t检验。结果准直层厚1．0mm组O％和50％重叠重建及准直层厚2．5mm组重叠重建率50％、70％图像得分无显著性差异，但与准直层厚2．5mm组重叠重建率0％及准直层厚5．0mm组图像得分有显著性差异；准直层厚2．5mm时3种Pitch图像得分无显著性差异；准直层厚2．5mm和1．0mm时VR重建和MIP重建的得分无显著性差异。结论MSCTA时选择适当的扫描重建参数，可以显示较多血管分支级数，获得较好的图像质量，其优化的条件为：准直层厚2．5mm，Pitch1．75，50％重叠重建，两种重建方法VR和MIP在显示血管方面无明显差别。     

正常肺小叶高分辨率CT研究

目的：评价HRCT能否显示正常人肺小叶结构。材料和方法：5例肺标本和40例正常人进行高分辨率CT（HRCT）检查，扫描层厚1mm～1．5mm，间隔10mm～15mm，采用高空间频率重建算法。结果：正常肺标本和活体肺小叶结构可被HRCT显示。正常人显示完整小叶0个～2个／层（平均0．05个），小叶间隔线0条～8条／g（平均1．4条）。外围肺血管的解剖特点可能有助于正常肺小叶结构的辨认。结论：正常肺小叶结构可在HRCT图像上显示和辨认，肺小叶是肺脏放射学基本单位。     

婴幼儿膀胱神经母细胞瘤1例

患儿男，60 d ，无意中发现腹部肿块，无其他明显不适。查体：中下腹膨隆，可触及一大小约60 mm×60 mm×45 mm的光滑、质硬、无痛包块，未触及明显肿大淋巴结。实验室检查：CA19‐973．32μ／mL、神经元特异性烯醇化酶（NSE）139．90 ng／mL。CT示：右侧髂血管旁膀胱腔内可见巨大软组织肿块影，大小约为59 mm×47 mm×34 mm（前后径×左右径×上下径），以实性成分为主，内密度不均匀，周围组织受压受侵（图1）；增强扫描呈中重度明显不均匀强化，内可见髂血管分支穿行（图2）；门脉期强化程度更明显，内可见斑片状低密度囊变坏死影，腹膜后未见肿大淋巴结影（图3）；冠状位上肿块呈纵向凸向膀胱腔内外生长，与膀胱壁连接处似有一窄茎（图4）。     

先天性支气管闭锁的MDCT诊断

目的：回顾性分析先天性支气管闭锁的多层CT（MDCT）影像特征，提高对该病的诊断准确性。方法：回顾性分析9例经临床随访或纤维支气管镜证实的先天性支气管闭锁的MDCT资料，全部病例采取各向同性（层厚≤1mm）CT容积采集，并同时重建5～10mm的常规图像，5例完成增强检查。结果：7例呈典型表现，MDCT表现为受累支气管近端与中心气道不相通，远端扩张，呈粗大而弯曲的分支，其内含气含液6例，单纯含液1例，受累肺组织肺气肿；5例增强扫描显示肺血管变细变少；2例呈不典型表现，直接显示支气管中断伴远侧肺结构紊乱1例，显示受累支气管闭塞伴扩张和含气、含液但无肺气肿1例。三维重建显示病变特征优于常规横断面。结论：先天性支气管闭锁多呈典型表现，包括闭锁的支气管扩张伴黏液栓和肺气肿，现代MDCT各向同性成像三维重建可充分显示其特征从而获得正确诊断；不典型表现需要结合纤维支气管镜检查进行诊断。     

螺旋CT对肺血管疾病诊断的临床应用

目的 探讨螺旋CT肺动脉造影(SCTPA)在肺血管疾病诊断中的临床应用价值。方法 对65例肺血管疾病行SCTPA检查，包括先天性肺血管疾病(肺动静脉瘘6例，特发性肺动脉扩张8例，肺动脉发育不全3例，一侧肺动脉缺如1例及肺静脉畸形引流5例)、获得性肺血管疾病(肺动脉栓塞41例，大动脉炎累及肺动脉1例)。SCTPA扫描层厚3mm，螺距1～1.5，亚秒级扫描时间0.8s，重建层厚1mm，重建方法包括MIP、MPR和SSD。结果 SCTPA对6例肺动静脉瘘共显示供血动脉13条、引流静脉9条和瘤囊8个，漏诊1例为多发性肺动静脉漏中的小瘤囊；特发性肺动脉扩张、肺动脉发育不全、一侧肺动脉缺如者SCTPA均能明确诊断；5例肺静脉畸形引流中的心外畸形部分SCTPA与手术对照良好；45例肺动脉栓塞，SCTPA诊断中心型肺栓塞35例，周围型肺栓塞6例。结论 SCTPA即可以显示肺血管的形态、结构与走行，又可显示肺血管内特征，对肺血管疾病的诊断有较高的临床实用价值，可大部分取代有创性肺血管造影。     

生物可降解性血管内支架的制备及其性能研究

目的 对采用聚左旋乳酸(PLLA)制备生物可降解性血管内支架(BIS)进行研究，并评估其物理学、机械力学性能及其生物相容性?方法先采用分子量为100 000 U的PLLA制作支架基杆，继而对支架基杆造孔和涂膜。支架固化成形后，对其主要的物理学和机械力学特性进行测试，并将22枚Z形BIS置入11只实验犬的腹主动脉和髂动脉内，分期处死动物行病理学观察。结果 制备出螺旋形和Z形2种型号支架，基杆直径为0．1～0．6mm，支架扩张后直径为6～15mm、长度为30～80mm；支架径向支持力为1．6～2．0kPa(1kPa=7．5mm Hg)、扩张率(压缩后支架直径与释放后完全展开支架直径的比值)为6．0～6．5，短缩率小于8％～10％，表面积与扩张后表面积的比值为0．16～0．18(小于0．2)，此种支架X线显示性差，透视下看不到。支架置入后1周，显微镜下可见支架杆部有少许纤维组织和少量血小板沉着；4周，支架杆部大部分被新生内膜覆盖；8周时支架被内膜完全覆盖，未见明显内膜增生，管壁光整，管腔通畅。图像分析显示8周后内膜生长趋势减弱。结论 此种BIS的物理学和机械力学特性可满足支架血管内置入的要求，特别是Z形BIS更适合于置入、释放：置入动物血管后的早期，支架可引起轻度炎性反应；8周时，支架被内膜完全覆盖；8周后未见显著的内膜增生性改变。具有可靠的机械强度和良好的生物相容性。     

肺内球形灶血管支气管平行CT征与病理对照研究

目的：探讨肺内球形灶血管支气管平行CT征的病理基础及诊断价值。方法：选择12例肺内球形灶血管支气管平行CT征进行病理对照研究。所有病灶大小为3．0－6．0cm。机型为Elscient CT Twin和GE　Prospeed CT机，12例均经肝静脉注射对比剂后，从肺尖至肺底扫描，层厚10．0mm，依病灶大小，加扫薄层3．0－5．0mm，手术标本按Heitzman法制标本。根据CT横断面扫描特点，将桂标本病灶部分进行横断，作0．5－1．0cm厚组织切片，然后，对“兴趣区”取材作石腊切片，HE染色，光镜观察，进行病理对照。结果：在12例肺球形灶血管支气管平行CT征中，除1例肺炎性假瘤外，其余均为肺恶性肿瘤。结论：肺内球形灶血管支气管平行CT征对肺恶性肿瘤有诊断价值。     

缺氧时肺动脉内皮细胞生长状态的变化

目的 研究低氧时内皮细胞生长状态的变化，以揭示缺氧性肺水肿的发生机制。方法 利用体外培养的肺动脉内皮细胞（PAEC），观察了在缺氧条件（3％O2）下，PAEC的生长曲线，细胞周期及细胞内特征性蛋白因子的变化，对PAEC的生长状态进行了质和量综合评价。结果 在观察的48h范围内，缺氧对PAEC的生长数量无明显影响（P＞0．05），细胞的S期在缺氧2h时出现了一过性的增加，同时G0/G1期出现了一过性的降低（P＜0．05），但随着缺氧时间的延长，PAEC的各个生长周期均无明显变化（P＞0．05），因子Ⅷ相关抗原阳性细胞数在缺氧过程中均呈明显下降（P＜0．05或P＜0．01）。结论 缺氧时，虽然PAEC在生长数量和生长周期上无明显变化，但生长质量出现了明显的下降，这将影响其功能状态，降低血管屏障作用的发挥。     

分叉病变的经皮冠状动脉介入治疗

目的　分叉病变的经皮冠状动脉介入治疗 (PCI)是一个十分棘手的问题 ,选择正确的处理策略是手术成功的关键。方法　自 1999年 12月至 2 0 0 4年 5月在我院心脏中心收治的 84例分叉病变患者 ,按Lefevre分型I型 35例 ,II型 2 2例 ,III型 16例 ,IVb型 11例。根据分支大小和病变情况 ,选择性使用钢丝保护、交换钢丝和球囊对吻扩张。 84例患者使用双钢丝保护时 ,视分叉病变严重程度 ,首先将钢丝送入病变较重的血管远端 ,然后放置第 2支钢丝至另一血管远端。分叉血管应注意避免放置亲水涂层钢丝 ,以免交换钢丝时扯断。结果　共有 74例患者进行双钢丝保护 ,5 3例患者进行对吻扩张 ,31例患者因分支影响较小或分支较细仅用球囊通过分支开口处 ,未进行扩张。 7例患者行对吻扩张分支血流仍为TIMIII级血流 ,1例患者分支 (直径 <1.5mm)完全闭塞。结论　选择并运用正确的策略是处理分叉病变的关键 ,对大多数分叉病变而言 ,双钢丝保护是十分必要的。对分叉病变的分支扩张后 ,必须进行主、分支对吻扩张 ,而确保主支血管畅通和适当的分支结果是明智之举     

Digitized cerebral synchrotron radiation angiography: quantitative evaluation of the canine circle of Willis and its large and small branches.

BACKGROUND AND PURPOSE: Conventional X-ray angiography lacks the sensitivity and spatial resolution needed to detect small amounts of iodinated contrast material and to quantitate diameters of the small vessels in the brain. The purpose of this study was to ascertain whether digitized synchrotron radiation microangiography, with the use of a high-definition TV camera system, can accurately show small cerebral vessels. METHODS: Six anesthetized dogs were exposed to monochromatic synchrotron radiation with an energy level of 33.3 keV optimized for iodine detection while iodinated contrast material was injected into the brachiocephalic and vertebral arteries. The images were detected with a high-definition TV camera system with a spatial resolution of 30 microm. In all, 26 cerebral angiograms of the circle of Willis with its branches were obtained, and the images were digitized at a workstation. RESULTS: The small branches of the circle of Willis were clearly visible on all images. Vasodilatation of the circle of Willis and its large and small branches induced by CO2 inhalation was quantitatively confirmed on the images: for example, the diameter of one small branch was increased from 0.24 +/- 0.04 mm to 0.38 +/- 0.12 mm. Temporal subtraction improved the image quality. CONCLUSION: The synchrotron radiation angiographic system is useful for visualizing large and small vessels deep in the brain as well as for quantitating their diameters.     

High-resolution computed tomography of the pig lung

Computed tomographic (CT)-anatomic correlation of the lung was performed on young Yorkshire pigs. After in vivo CT, the lungs were removed, fixed, and dried. The lung specimens were studied with CT and on several specimens, bronchography and arteriography also were done to establish the normal anatomy. Subsequently, the specimens were sliced at corresponding levels of the CT cuts and histology was done as needed. The lobules in the pig lung are very well demarcated. On the specimen radiographs with bronchography and in vivo CT in pulmonary edema, "sublobular units" can be readily identified that are rather uniform in size. On the in vivo CT with the standard algorithm, the relationship between the branches of the pulmonary artery and bronchus can be shown to the level of segmental bronchi. With the bone detail algorithm, vessels are clearly shown and lobar bronchi become visible. On in vivo CT, the lobular demarcations cannot be seen in the normal pig but clearly are visible in pulmonary edema. In cases of pulmonary edema, in addition to the lobules, the sublobular units and the sublobular bronchi, which measure .5 to .7 mm in diameter, also can be appreciated. Because of the well-developed pulmonary lobules and the uniformly sized sublobular units, the Yorkshire pig is potentially a good model for radiologic-pathologic correlation, particularly of airspace disease.     

Peripheral anatomic evaluation using 3D CT hepatic venography in donors: significance of peripheral venous visualization in living-donor liver transplantation

OBJECTIVE: The purpose of this study was to determine clinical roles for 3D CT hepatic venography in the evaluation of peripheral hepatic venous anatomy during living-donor liver transplantation. MATERIALS AND METHODS: Subjects comprised 54 donors (age range, 20-60 years) who had undergone surgery to donate a liver for transplantation. Visualization of each hepatic venous branch and total visualization using 3D CT hepatic venography were evaluated. Maximum venous branch order visualized was graded as nil, first branch, second branch, or third branch or more. The distance between the hepatic surface and the tip of each hepatic venous branch was classified as 0-5 mm, 6-10 mm, 11-15 mm, 16-20 mm, or 21-25 mm. Quality of total 3D CT hepatic venography was evaluated subjectively as poor, good, fair, or excellent. Dominance of large hepatic veins in the right lobe, peripheral branching pattern of the middle hepatic vein, and branching pattern of the vein draining segment IVb were also assessed. RESULTS: Most hepatic venous branches (96.2% [275/286]) were visualized up to at least the second-order branches, and 93.7% (268/286) of branches were within 10 mm of the hepatic surface. As for total visualization, 98% (53/54) of cases were regarded as excellent. The dominant vein in the right lobe was the right hepatic vein in 27 cases, inferior hepatic vein in 25, and middle hepatic vein in one. The branching pattern of the middle hepatic vein was type 1 in 36 cases, type 2 in nine, and type 3 in eight. Segment IVb vein branched from the middle hepatic vein in 20 patients, and from the left hepatic vein in 34. CONCLUSION: Because 3D CT hepatic venography visualizes peripheral hepatic venous branches in detail, the technique is useful for determining operative indications in living-donor liver transplantation.     

枕骨骨膜瓣的应用解剖

为枕骨骨膜瓣的临床应用提供解剖学基础。在６ 具成人尸体标本上观测了枕骨骨膜瓣的血管分布。结果发现枕动脉发出骨膜支（１２０ ±１８） 个分支，分支起始处外径为（０２ ±０１） ｍ ｍ ，枕动脉枕支起始处外径为（１２ ±０２） ｍ ｍ 。椎动脉枕部的外径为（２ ．９±０２） ｍ ｍ ，发出骨膜支（３５ ±０５） 支，其分支起始处外径为（０２±００７） ｍ ｍ 。骨膜血管网与对侧吻合丰富。结果提示可设计带骨膜血管蒂的枕骨骨膜瓣向下翻转植骨修复枕颈部骨缺损。     

多层螺旋CT肺动脉成像的图像后处理技术及应用

目的：探讨多层螺旋CT肺动脉成像的各种图像后处理技术对显示肺动脉的优缺点及临床应用价值。方法：采用Philips Brillance 16排螺旋CT,美国MADRAD双筒高压注射器。图像后处理分析软件包括MIP、VR、VE、VIP。分析58例行胸部CTA检查的血管重建图像,比较各种图像后处理技术对肺动脉的显示效果。结果：58例患者都能清晰显示肺动脉走形、分支及管径。各种常用图像后处理技术中,MIP既能清晰显示肺动脉的解剖学形态,又能显示其与周围组织关系;在完整显示肺动脉的解剖学形态方面,VR优于MIP,但不能显示血管腔内情况;VIP优势在于单条血管的跟踪观察;在显示肺动脉分支,尤其是细小分支时,VE能跟踪血管发现血管的分支及其走形,并了解管壁是否光滑,在这一方面优于其他后处理技术。结论：多层螺旋CT的肺动脉成像可直观地、准确地显示肺动脉及其分支、走形、形态、管径。肺动脉成像的各种后处理技术中,MIP和VR两者联合应用对解剖学形态及其与周围组织关系显示很好;VIP及VE亦有很好的辅助作用。     

Optimal branching of human arterial bifurcations

The area ratio, defined as the combined cross-sectional areas of the daughter branches divided by that of the parent artery, is an important indicator of "expansion" or "narrowing" in an arterial tree. In 120 morphologically normal human arterial bifurcations, angiographically studied, we measured branch artery diameters at and away from the bifurcation point to obtain "beta" and "D" ratios, respectively. These results were compared with optimal curves. Area ratio D values showed better agreement than area ratio beta with theoretical curves; for area ratio D, the positive regression line showed the same trend as expected from theory (y = 1.26 + 0.153x); for area ratio beta, the regression line was negative, showing a trend opposite to theory (y = 0.962 - 0.191x). Area ratio beta showed a significant correlation coefficient (r = 0.194; P less than 0.05) associated with aging, while for area ratio D it was not the same (r = 0.023; P less than 0.05). A significant correlation coefficient was also found between both of the area ratios and total branching angle. The new area ratio D, reflecting the branching geometry nearer to the bifurcation, is more promising than area ratio beta in the evaluation of optimal arterial bifurcation.     

正常成人肺动脉分支心动周期不同时相影像对比研究

目的建立正常成人多排螺旋CT(MDCT)心动周期不同时相肺动脉分支几何学数据库。方法选择正常成人胸部心电门控MDCT增强扫描,分别进行代表心动周期不同时相的心电间期的滑动薄层块最大密度投影(STS M IP)重建,并测量主肺动脉至叶段级分支的直径及长度;采用Dopp ler超声心动图心电门控测量主肺动脉瓣上及左右肺动脉近端内径作为对比。结果MDCT显示主肺动脉瓣上直径收缩期较舒张期增大,双肺动脉近端、右肺动脉远端、右中叶动脉、右下后基底段及左下内基底段动脉直径舒张期较收缩期增大,右上叶后段长度舒张期较收缩期增大,其余肺动脉分支数值未出现显著性差异。主肺动脉/右肺动脉跨度舒张期较收缩期增大。超声心动图除主肺动脉瓣上直径双期变化与MDCT相一致外,左右肺动脉近端内径双期无显著性差异。结论将MDCT胸部增强扫描得到主肺动脉至肺叶段动脉分心动周期不同时相进行测量对建立肺动脉流态模型是有必要的。     

Microwave Ablation of the Lung in a Porcine Model: Vessel Diameter Predicts Pulmonary Artery Occlusion

Purpose

To determine the size of pulmonary artery (PA) at risk for occlusion during percutaneous microwave ablation and to assess the effect of vessel diameter, number, and patency, on ablation zone volume.

Materials and Methods

Computed tomography (CT) fluoroscopy-guided percutaneous microwave ablations were performed in 8 pigs under general anesthesia. All ablations were performed at 65 W for 5 min with a single 17-gauge antenna positioned in the central third of the lungs. A CT pulmonary angiogram was performed immediately after the ablations. The maximum diameter, number and patency of PA branches within each ablation zone were recorded. Ablation volumes were measured at gross dissection and with CT. Student’s t test was used to compare ablation zone volumes among groups.

Results

Twenty-one pulmonary ablations were performed. Six of the ablation zones (29%) contained at least 1 occluded PA branch. The mean diameter of the occluded PA branches in the ablation zones (2.4 mm; range, 2.0–2.8 mm) was significantly smaller than non-occluded PA branches (3.7 mm; range: 2.1–6.9 mm; p = 0.009). No PA branches ≥3 mm in size were occluded. There was no significant difference in volume of gross ablation zones that contained occluded versus non-occluded PAs (p = 0.42), one versus multiple PAs (p = 0.71), or PAs <3 mm versus ≥3 mm in diameter (p = 0.44).

Conclusions

PAs ≥3 mm in size have a low risk for iatrogenic occlusion during percutaneous microwave ablation. The presence of multiple adjacent PA branches, an occluded PA branch, and a vessel diameter ≥3 mm within the ablation zone had no observed effect on ablation zone volume.

     

咯血患者肺外体循环动脉供血的CT血管造影

目的探讨咯血患者肺外体循环动脉(ESCA)供血的CT血管成像(CTA)表现及其与胸膜增厚的关系。资料与方法回顾性分析233例咯血患者的影像学资料,通过数字减影血管成像(DSA)明确咯血责任血管的来源和数量,分析ESCA的CTA表现及其与胸膜增厚的关系。结果 233例咯血患者中,84例(36.1%)存在ESCA供血,共318支,包括肋间后动脉171支,锁骨下动脉分支56支,胸廓内动脉分支47支,腋动脉分支23支,腹主动脉分支21支;CTA表现为管径增粗、走行纡曲,发出分支至病灶区域参与供血,部分与肺动脉或供血支气管动脉相互吻合形成血管网。84例有ESCA供血患者中,82例(97.62%)伴有靶胸膜增厚;149例无ESCA供血患者,90例(60.40%)伴有靶胸膜增厚;有ESCA供血患者伴靶胸膜增厚率高于无ESCA患者(χ2=36.60,P<0.01),且ESCA来源与靶胸膜增厚部位之间存在对应关系。结论 ESCA是重要的咯血责任血管,其数目、来源与病灶部位及胸膜增厚密切相关。     

肺磨玻璃结节高分辨率CT影像特征及其与血管内皮生长因子、Ki-67、p53的相关性研究

目的 探讨肺磨玻璃结节（GGN）高分辨率CT（HRCT）影像特征及其与免疫组织化学（IHC）检查指标的相关性,评估其对临床的应用价值。 方法 回顾性分析2019年1月至2020年5月于南方医科大学顺德医院（佛山市顺德区第一人民医院）经手术和组织病理学检查结果确诊的144例肺GGN患者的临床资料,其中男性46例、女性98例,年龄28~80（51.9±11.9）岁。所有患者均行手术及IHC检查,根据2021年世界卫生组织肺肿瘤组织新分类方法,将144例肺GGN患者分为浸润前病变（PI）、微浸润性腺癌（MIA）和浸润性腺癌（IA）3组,比较3组肺GGN患者HRCT影像特征的差异及其与IHC检查指标的相关性。影像特征的组间比较采用方差分析或χ2检验。采用单因素及多因素Logistic回归模型分析影响因素及建立预测模型,并绘制受试者工作特征曲线,获得最佳诊断临界值。采用χ2检验分析HRCT影像特征与IHC检查指标表达水平的相关性。 结果 单因素Logistic回归分析结果显示,GGN长径、分叶征、毛刺征、胸膜牵拉征、瘤-肺边界、微血管穿行征、空气支气管征在3组间的差异均有统计学意义（F=8.952~82.901,均P<0.05）。多因素Logistic回归分析结果显示,GGN长径是评估肺GGN浸润性的独立危险因素。当GGN长径<6 mm时倾向于PI;当6 mm≤GGN长径≤10 mm时倾向于MIA;当GGN长径>10 mm时倾向于IA。IHC检查结果显示,血管内皮生长因子（VEGF）、p53、细胞增殖核抗原（Ki-67）对肺GGN浸润程度的预测价值较高,曲线下面积分别为0.829、0.773、0.760。相关性分析结果显示,GGN长径>10 mm、分叶征、毛刺征、胸膜牵拉征、瘤-肺边界与VEGF、p53、Ki-67的高表达水平具有相关性（χ2=13.582~41.351,均P<0.05）;微血管穿行征与Ki-67的高表达和VEGF、p53的低表达水平具有相关性（χ2=15.111、15.644、16.121,均P<0.05）。 结论 GGN长径是评估肺GGN浸润性的独立危险因素,具有较好的诊断效能。肺GGN的HRCT影像特征与Ki-67、p53和VEGF表达水平具有相关性,将肺GGN的HRCT影像特征和IHC检查指标综合分析可以有效评估组织病理学分型、肿瘤细胞的增殖活性及浸润程度,为临床对肺GGN患者的管理及选择合适的治疗方案提供有价值的参考。