显微CT多阈值分析评价骨折愈合效果

目的研究显微CT多阈值分析对骨折愈合过程中不同类型骨组织表达的可靠性,为采用显微CT影像学方法有效评价骨折愈合奠定实验基础。方法制备大鼠股骨中段闭合性骨折模型,5 w后采用显微CT对骨折部位进行扫描,分别于225～700(代表全骨组织),225～330(代表钙化软骨和骨痂)和331～700(代表成熟骨组织)3个阈值范围内,测量和分析骨折标本的骨体积(bonevolume,BV)、组织体积(tissue volume,TV)和骨体积分数(BV/TV)。然后,对标本进行四点弯曲生物力学测试,分别测量和计算标本的刚度(stiffness,S)和弹性模量(elastic modulus,E)。最后,制作上述标本的不脱钙组织切片,分别行苏木精-伊红(H&E)和Von Kossa(VK)染色,并采用Osteomea-sure软件对切片的骨体积分数(bone volume/tissue volume,BV/TV)进行测量和分析。上述实验均以正常大鼠股骨作为对照。结果显微CT重建:实验组骨折已完全连接,髓腔再通。显微CT测量结果示:在225～700阈值内,实验组BV值与正常对照组无显著差异(P>0.05),其BV/TV也略低于正常对照组(P=0.054);在225～330阈值内,实验组BV和BV/TV均明显高于正常对照组(P<0.05);在331～700阈值内,实验组BV和BV/TV明显低于正常对照组(P<0.05)。生物力学测量示:实验组S和E均明显低于正常对照组(P<0.05)。H&E染色示:实验组骨折已完全被新生组织桥接修复,但修复组织多为软骨样或编织骨组织。VK染色示:实验组骨折部位填充组织钙盐含量较低,部分组织VK染色阴性。采用Osteomeasure软件对VK染色阳性区域进行测量和统计学分析示:实验组BV/TV明显低于正常对照组(P<0.05)。结论①采用显微CT单阈值分析会将部分不成熟的骨组织成分当做正常骨组织进行评价,造成对骨修复效果和骨强度误判。②通过显微CT多阈值分析可以明确表示不同的骨质成分,相关结果与组织学和生物力学检测存在较好的依从性。③采用显微CT多阈值分析技术能够有效评价骨折愈合效果。     

Lung tumour growth kinetics in SPC-c-Raf-1-BB transgenic mice assessed by longitudinal in-vivo micro-CT quantification

Background

SPC-c-Raf-1-BxB transgenic mice develop genetically induced disseminated lung adenocarcinoma allowing examination of carcinogenesis and evaluation of novel treatment strategies. We report on assessment of lung tumour growth kinetics using a semiautomated region growing segmentation algorithm.

Methods

156 non contrast-enhanced respiratory gated micro-CT of the lungs were obtained in 12 SPC-raf transgenic (n = 9) and normal (n = 3) mice at different time points. Region-growing segmentation of the aerated lung areas was obtained as an inverse surrogate for tumour burden. Time course of segmentation volumes was assessed to demonstrate the potential of the method for follow-up studies.

Results

Micro-CT allowed assessment of tumour growth kinetics and semiautomated region growing enabled quantitative analysis. Significant changes of the segmented lung volumes over time could be shown (p = 0.009). Significant group differences could be detected between transgenic and normal animals for time points 8 to 13 months (p = 0.043), when marked tumour progression occurred.

Conclusion

The presented region-growing segmentation algorithm allows in-vivo quantification of multifocal lung adenocarcinoma in SPC-raf transgenic mice. This enables the assessment of tumour load and progress for the study of carcinogenesis and the evaluation of novel treatment strategies.     

Age- and sex-related changes of mandibular condylar cartilage and subchondral bone: A histomorphometric and micro-CT study in rats

Objective

To quantify the age- and sex-related changes in the rat condylar cartilage and subchondral bone.

Methods

SD rats were obtained at the ages of 2, 3, 4, 5, 6 and 7 months. For each sex, the temporomandibular joints tissue blocks from four rats were subjected to histological assessment of cartilage thickness and subchondral bone architecture; for the remaining three rats, the mandibular condyles were delivered for gross measurement and evaluation of the mineralization and architecture properties of the subchondral bone by means of micro-CT.

Results

Rapid decrease of cartilage thickness but increase of subchondral bone density occurred respectively from 2 to 3 and 3 to 4 months old in female and 2 to 4 and 3 to 5 months old in male (P < 0.05), whereas rapid changes of subchondral bone architecture occurred from 3 to 4 months old in both sexes (P < 0.05). The significant enlargement of condyle size occurred at 4 or 5 months old in female but at 5 or 6 months in male (P < 0.05).

Conclusion

This study demonstrated that the rapid developmental changes of rat condylar cartilage and subchondral bone primarily occurred before 4 months of age, resulting in thinner cartilage but larger and thicker subchondral bone, and they were followed by rapid growth in condylar size. Sex differences were identified that the endochondral ossification of fibrocartilage and formation of subchondral bone were faster in female than in male rats, leading to the earlier enlargement of condyle in female than in male.     

Role of WNT Agonists,BMP and VEGF Antagonists in Rescuing Osteoarthritic Knee Cartilage in a Rat Model

IntroductionThe superficial zone of articular cartilage (AC) is vital for its function and biomechanics. The damaged AC gets vascularized and undergoes hypertrophy and ossification. Studies have highlighted these two as the major causative factors in osteoarthritis (OA). We aimed at preventing the OA progression in a rat knee instability model by inhibiting the vascular ingrowth and ossification using VEGF and BMP antagonist. A WNT agonist was also used to promote AC regeneration because of its protective effect on the superficial layer.MethodsRat knee OA was created by surgical excision of the medial meniscus and medial collateral ligament. Forty rats were divided into two groups of twenty each for surgical control and tests (surgery + intra-articular injection of drugs every two weeks). Ten animals from each group were sacrificed at four and eight weeks. Histology was mainly used to evaluate the outcome.ResultsA surgical OA model was successfully created with higher histological scores for operated knees, both in short- (P = 0.0001) and long-term (P = 0.001). Modified Mankin score was lesser in the test animals as compared to control (P = 0.17) in the short-term, but the trend was reversed in the long-term (P = 0.13). Subgroup analysis revealed that repeated injections in the anterolateral compartment contributed to higher scores in the lateral (P = 0.03) and anterior (P = 0.03) compartment of the knee in the long-term.ConclusionThe combinatorial approach was effective in controlling the OA in short-term. Further studies are needed to test the sustained drug delivery system to improve the outcome.     

华东地区汉族人下颌第一前磨牙根管弯曲度的测量

目的 采用显微CT精确测量下颌第一前磨牙根管的弯曲度,为临床根管治疗提供依据。方法 收集华东地区汉族人154颗离体下颌第一前磨牙并进行显微CT扫描,采用Mimics 10.01（Materialise,Leuven,比利时）对牙齿及根管系统进行三维重建,在平行投照模式下,采集根管系统颊面观及邻面观的影像并测量根管的弯曲度。结果 下颌第一前磨牙单根管在颊面观上初次弯曲的平均角度仅为11.1°（Schneider法）,二次弯曲出现率较低,在颊面观出现6例,邻面观出现4例。下颌第一磨牙双根管时,重度弯曲（>20°）主要位于邻面观,颊、舌根管初次弯曲的平均角度分别为17.5°和28.7°,二次弯曲的发生率分别为19.1%（9/47）和85.1%（40/47）。舌侧副根管的弯曲半径和圆心角均值分别为6.6 mm和54.2°;舌侧根管的根管口离根尖的平均距离为6.6 mm。结论 下颌第一前磨牙舌侧根管多出现在根中及根尖1/3,在邻面观常有重度弯曲。     

显微计算机断层扫描对体表恶性肿瘤成像的研究

目的探讨术中应用显微计算机断层扫描(Micro-CT)对体表恶性肿瘤成像的参数设置和效果,总结体表软组织和肿瘤的Micro-CT影像特点。方法根据入选标准,收集2018年10月至2020年1月解放军总医院第一医学中心整形修复科收治的体表恶性肿瘤患者。通过手术切除肿瘤,将离体肿瘤标本分割成合适大小(长×宽×厚不超过5 cm×3 cm×3 cm),置于Micro-CT扫描床上,在不同参数下进行扫描。(1)采用不同时间扫描:保持扫描电压不变(肉瘤为50 kV、鳞状细胞癌及其他肿瘤为70 kV),对同一标本选择4 min和14 min分别进行扫描。(2)采用不同电压扫描:保持扫描时间不变(4 min),对同一标本选择30、50、70、90 kV 4种电压分别进行扫描。对比不同扫描时间及扫描电压下的成像效果,得出不同肿瘤的最佳扫描参数。(3)对影像学感兴趣区进行取材,制作病理学HE染色切片,并采用Precice全自动数字切片扫描系统扫描获得数字切片,与Micro-CT相应截面的影像图进行对比,记录不同组织的影像学特点。结果共纳入27例患者,其中男15例,女12例,年龄33~82岁,平均63.9岁,其中皮肤鳞状细胞癌16例、基底细胞癌2例、乳房外Paget病2例、黑色素瘤1例、隆突性皮肤纤维肉瘤3例、血管肉瘤1例、脂肪肉瘤2例,对比影像学和病理学标本共65组。(1)扫描时间:扫描4 min与14 min均能获得清晰的影像,并能满足观察肿瘤形态、判读肿瘤边界的要求。(2)扫描电压:对于鳞状细胞癌,电压为30、50 kV时成像不清晰,70、90 kV时成像效果较好,部分病例中的微小钙化点在90 kV时与肿瘤组织对比度不高;对于各种肉瘤,电压为30 kV时成像不清晰,50 kV时成像效果较好,70、90 kV时肿瘤与周围脂肪组织对比度不高。(3)Micro-CT影像图与病理切片对比结果显示,体表肿瘤及其周围正常软组织的影像学形态与病理学切片十分接近。正常皮肤与皮下组织分界清楚,毛囊清晰可辨。肿瘤组织的影像特点与肿瘤的种类、瘤细胞密集程度有关,主要表现为高密度影,体积较正常皮肤明显增厚,基底部相对平滑、无皮下脂肪伸入真皮内形成参差的低密度影,也无毛囊等正常的皮肤附属器影,偶尔可见散在的高密度钙化点。鳞状细胞癌、肉瘤与正常皮肤、皮下的边界可以分辨。对于局限于皮肤内的肿瘤,如基底细胞癌、乳房外Paget病等,成像效果不佳。结论Micro-CT扫描参数需要根据肿瘤性质进行选择,扫描时间对评估肿瘤影响不大,推荐术中扫描时长为4 min;鳞状细胞癌扫描电压推荐为70 kV,肉瘤为50 kV。Micro-CT对体表软组织标本皮肤结构成像清楚;对侵袭至皮下、与周围组织密度相差较大的肿瘤,形态可辨;对于生长范围不超过真皮的肿瘤,成像效果不佳。     

Effect of fixation on neovascularization during bone healing

Fixation and vascularity after bone fracture are two critical factors for successful healing, and their influences on bone healing have been studied by many researchers. This research aims to obtain three-dimensional (3D) reconstruction images of neovascularization of the soft tissues surrounding the fracture with vascular perfusion and micro-computer tomography (micro-CT) imaging, and to investigate the effect of stable fixation on neovascularization and the pattern of vascularity during the process of bone healing. To accomplish this, 36 Sprague-Dawley (SD) rats underwent mid-shaft transverse osteotomy of the right tibia. Half of them received stable fixation with a newly custom-designed external fixator (FSF, the group of fracture with stable fixation), while the rest received no fixation (FNF, the group of fracture with no fixation). The results indicated that FNF samples had more transversal vascular distribution than FSF samples; FSF samples had more longitudinal vascular distribution than FNF samples; and the spatio-temporal pattern of vascularity in FSF samples was more similar to that in the control group (CON, the group without fracture) than that in FNF samples. At the time of 2 and 4 weeks postoperatively, FNF samples had significantly higher vessel volume ratio (VV/TV), larger vessel number (VN) and higher vessel surface density (VS/TV) than CON samples. At all sacrifice times, FSF samples contained significantly higher VV/TV, VN and VS/TV values compared with FNF samples. In summary, neovascularization and its pattern are obviously influenced by the mechanical fixation. Stable fixation can promote longitudinal vascularity pattern formation, which tends to be similar to the natural vascularity pattern, and this benefits the inter-fragmentary blood fluid connectivity during bone healing process.     

气雾攻击法感染结核病小鼠模型的建立及其综合评价

目的模拟自然感染方式建立结核病小鼠模型,并对其病理变化进行综合评价。方法通过气雾攻击方式将结核分枝杆菌H37Rv接种至C57BL/6J小鼠体内。在感染后的4周、6周、8周对小鼠进行micro-CT活体动态扫描,无菌分离肺脏和脾脏,肉眼观察病变情况,活菌菌落计数,组织病理检测(HE和抗酸染色)。结果肉眼观察和micro-CT扫描发现,不同时间小鼠肺部感染情况逐渐加重,至感染后第8周时病变弥漫至整个肺部；HE染色肺组织出现弥漫性肉芽肿样实变；抗酸染色可见结核分枝杆菌。结论通过大体病变、病理、影像、菌落计数几个方面对建立的小鼠模型进行综合分析,证明利用气雾攻击法感染的结核病小鼠模型建立成功；该模型在形成病变时与结核患者的情况存在一定差异,对其完善的综合评价有助于在相关研究中对该小鼠模型的合理应用。     

骨质疏松髋部骨折区骨微结构变化研究

目的 分析骨质疏松髋部骨折区张力侧骨小梁微结构的变化。方法 实验组选择16例低能量创伤致股骨颈骨折需要行髋关节置换的老年患者,术前行健侧髋部骨密度检测。因活体取材困难,故选取5根青年同种异体股骨为对照组。在实验组与对照组股骨颈张力侧骨小梁中,切取5mm×5mm×10mm的松质骨,行Micro-CT扫描分析微结构参数。分析两组之间微结构参数的差异及实验组患者微结构参数与骨密度之间关系。结果 实验组微结构：骨体积分数(BV/TV) 0.0645±0.0259,骨小梁数量(Tb.N) (0.8078±0.2212) mm-1,骨小梁厚度(Tb.Th ) (0.0836±0.0212) mm, 骨小梁距离(Tb.Sp) (1.2197±0.4492) mm,连接密度(Conn.D) 1.8577±1.0217, 结构模型指数(SMI) 1.7780±0.5168。对照组微结构：BV/TV 0.1470±0.0633,Tb.N (1.2692±0.1376)mm－1,Tb.Th (0.1201±0.0414) mm,Tb.Sp (0.6810±0.1129) mm,Conn.D 3.3585±1.7851,SMI 0.8781±0.6665。与对照组相比,实验组髋部张力侧松质骨小梁显著破坏,各微结构指标均有明显的改变,差异有统计学意义（P＜0.05）。实验组微结构参数与骨密度之间无相关性（P＞0.05）。结论 骨质疏松髋部骨折区张力侧骨小梁明显破坏,这可能是髋部骨折发生的重要原因之一。     

显微CT旋转步长对牛腰椎松质骨重建图像及数据的影响

目的:探讨显微CT对牛腰椎松质骨扫描时不同旋转步长对扫描时间、磁盘占用、重建图像质量及骨形态计量学数据的影响,为松质骨扫描设定旋转步长提供实验依据.方法:取牛同一腰椎的8块矩形离体松质骨,尺寸为4×2×2mm,依次设定旋转步长为0.25°、0.30°、0.40°、0.50°、0.75°、1.0°、1.5°、2.0°进行显微CT扫描,将步长0.25°设为对照组,比较其他7个步长组的三维重建图像质量、扫描时间、占用磁盘空间情况;分析骨体积(bone volume,BV)、骨表面积(bone surface,BS)、骨表面积密度(bone surface/volume ratio,BS/BV)、板状骨小梁厚度[trabecular thickness(plate model),Tb.Th(pl)]、板状骨小梁分离度[trabecular separation(plate model),Tb.Sp(pl)]、板状骨小梁数量[trabecular number (plate model),Tb.N(pl)]、杆状骨小梁直径[trabecular diameter (rod model),Tb.Dm (rd)]、杆状骨小梁分离度[trabecular separation (rod model),Tb.Sp (rd)]、杆状骨小梁数量[trabecular number(rod model),Tb.N(rd)]、骨小梁模式因子(trabecular bone pattern factor,TBPf)共10项骨形态学参数的统计学差异.结果:与步长0.25°组比较:(1)步长0.30°～1.5°的6组三维重建图像质量有不同程度的降低,但骨小梁结构清晰可辨,仍可较好反映松质骨标本的解剖学特征,而步长2.0°组骨小梁结构模糊,图像质量明显下降;(2)随着旋转步长的增大扫描时间、磁盘占用均呈线性降低;(3)骨形态计量学10项数据分析表明,步长0.30°、0.40°组各项数据与步长0.25°组比较均无统计学差异(P＞0.05),BV值自步长2.0°组出现统计学差异(P＜0.05),Tb.Sp(rd)、TBPf值自步长0.50°组出现统计学差异(P＜0.05),BS、BS/BV、Tb.Th(pl)、Tb.Sp(pl)、Tb.N(pl)、Tb.Dm(rd)、Tb.N(rd)7组数据自步长0.75°组出现统计学差异(P＜0.05).结论:对牛腰椎松质骨进行显微CT扫描时,旋转步长0.4°扫描时,在保证重建图像清晰、数据精确的前提下,扫描时间最短、磁盘空间占用最低,适用于精确分析椎体骨形态计量学三维数据;1.5°扫描时,虽数据结果存在误差,但扫描时间快,磁盘占用低,且重建图像清晰、骨小梁完整,适用于快速观测椎体骨小梁影像学信息;2.0°扫描时,图像模糊、数据误差显著,不推荐选用.