Using Monte Carlo simulations to commission photon beam output factors--a feasibility study

This study investigates the feasibility of using Monte Carlo methods to assist the commissioning of photon beam output factors from a medical accelerator. The Monte Carlo code, BEAMnrc, was used to model 6 MV and 18 MV photon beams from a Varian linear accelerator. When excellent agreements were obtained between the Monte Carlo simulated and measured dose distributions in a water phantom, the entire geometry including the accelerator head and the water phantom was simulated to calculate the relative output factors. Simulated output factors were compared with measured data, which consist of a typical commission dataset for the output factors. The measurements were done using an ionization chamber in a water phantom at a depth of 10 cm with a source-detector distance of 100 cm. Square fields and rectangular fields with widths and lengths ranging from 4 cm to 40 cm were studied. The result shows a very good agreement (< 1.5%) between the Monte Carlo calculated and the measured relative output factors for a typical commissioning dataset. The Monte Carlo calculated backscatter factors to the beam monitor chamber agree well with measured data in the literature. Monte Carlo simulations have also been shown to be able to accurately predict the collimator exchange effect and its component for rectangular fields. The information obtained is also useful to develop an algorithm for accurate beam modelling. This investigation indicates that Monte Carlo methods can be used to assist commissioning of output factors for photon beams.     

用γ射线显影法研究磷酸川芎嗪脉冲塞胶囊在犬胃肠道内的崩解释药和转运行为

为了解所研制的新型脉冲给药系统一磷酸川芎嗪脉冲塞胶囊能否在体内实现脉冲释药及其在体内的崩解释药部位。采用7射线显影法研究了在含药片中含有放射性同位素。^99mTc标记二乙三胺五醋酸（DTPA）的脉冲塞胶囊在犬胃肠道内的崩解释药和转运行为。结果表明，自制的脉冲塞胶囊在间隔一定时间（时滞）后，其中的含药片开始在犬的胃幽门部位或小肠崩解释药。且释药较为迅速。与希望的脉冲释药方式一致。此外．脉冲塞胶囊在犬体内的释药时滞随溶蚀塞重量的减少而缩短，可以通过调节凝胶塞的重量来获得所需时滞的脉冲塞胶囊满足时辰治疗的要求。     

生物陶瓷微颗粒引发的细胞和组织损害

为论证生物陶瓷烧结不完全形成的微颗粒（〈5μm）引发细胞和组织损害的假设，对该类颗粒在体内和体外的细胞和组织损害进行了研究：（1）对4种双相生物陶瓷（BCP）进行细胞毒性试验。试验发现所有的浸出液出现细胞毒性，但是浸出液经离心后，毒性消失；（2）对羟基磷灰石（HA）、p磷酸三钙（pTCP）和40％pTCP／60％HA混合物微颗粒进行细胞抑制实验。结果显示随着微颗粒的浓度增加，成纤维细胞活力下降；而当微颗粒浓度达到一万个／细胞时，细胞活力和增殖能力完全消失；（3）HA，pTCP和BCP陶瓷颗粒（500-1500um）被植入到兔子股骨远端，种植12周后β-TCP的降解率为40％，BCP为5％，但是HA接近不降解。新骨形成在β-TCP（21％）和HA（18％）比BCP（12％）更为明显。同时BCP颗粒的周围有很多的微颗粒形成，可见吞噬细胞吞噬微颗粒，形成吞噬体。以上结果提示，微颗粒可能是局部炎症和细胞损害的首要原因，而且有可能影响骨形成。因此，我们必须注意生物陶瓷烧结的重要性，它们的烧结不良就可形成微颗粒，引发细胞和组织的损害。特别是BCP陶瓷含有两种需要不同烧结温度的粉体，它的烧结难度较高，很易形成微颗粒。     

Müller glial cells express nestin coupled with glial fibrillary acidic protein in experimentally induced glaucoma in the rat retina

This study was aimed to investigate reactive changes of Müller glial cells in rats subjected to experimentally induced glaucoma. In the latter, it is well documented that elevated intraocular pressure leads to the loss of ganglion cells as confirmed in this study. The present results have shown that Müller glial cells as well as astrocytes closely associated with the ganglion cells reacted vigorously to increased intraocular pressure as manifested by the induced and upregulated expression of nestin and glial fibrillar acidic protein. A major finding in glaucomatous rats was the induced expression of nestin together with glial fibrillar acidic protein with the rise of the intraocular pressure beginning at 2 h. The marked nestin expression appeared to be most intense at 1 week after operation and was sustained at 3 weeks. Induced nestin expression in Müller glial cells was demonstrated unequivocally in whole-mount preparation of the retina. In the same tissue preparation, nestin expression was also detected in some astrocytes. Western blotting analysis confirmed a marked increase in expression of nestin and glial fibrillar acidic protein. Present results suggest that nestin as well as glial fibrillar acidic protein is a useful biomarker for retina injury. The induced expression of these intermediate filament proteins in Müller glial cells especially at their end-feet and also in some astrocytes adjoining the neuronal injury suggests a potential neuroprotective mechanism in response to acute rise in intraocular pressure resulting in neuronal degeneration.     

Expression and functional analysis of Tgif during mouse midline development.

The Tgif gene encodes a homeodomain protein that functions as a transforming growth factor beta (TGF-beta) repressor by binding to Smad2. Mutations in the TGIF gene are associated with human holoprosencephaly, a common birth defect caused by the failure of anterior ventral midline formation. However, Smad2-mediated TGF-beta signaling in the axial mesendoderm has been demonstrated to be essential for ventral midline formation, and loss of a Smad2 antagonist should in principle promote rather than inhibit ventral midline formation. This suggests a more complex mechanism for the function of TGIF in controlling ventral midline formation. To explore the role of TGIF in ventral forebrain formation and patterning, we investigated Tgif expression and function during mouse development by in situ hybridization and gene targeting. We found that Tgif is highly expressed in the anterior neural plate, consistent with the proposed neural differentiation model in which TGF-beta suppression is required for normal neural differentiation. This result suggests a possible role for Tgif in anterior neural differentiation and patterning. However, targeted disruption of the Tgif gene during mouse development does not cause any detectable defects in development and growth. Both histological examination and gene expression analysis showed that Tgif-/- embryos have a normal ventral specification in the central nervous system, including the forebrain region. One interpretation of these results is that the loss of TGIF function is compensated by other TGF-beta antagonists such as c-Ski and SnoN during vertebrate anterior neural development.     

Enhanced immunogenicity and antitumour effects with heterologous prime-boost regime using vaccines based on MG7-Ag mimotope of gastric cancer

MG7-Ag, gastric cancer-associated antigen, has been shown to be immunogenic and has been used as marker molecule for prognosis. In a previous study, we developed an oral DNA vaccine based on MG7-Ag mimotope. However, we failed to detect cellular immune response using the oral MG7-Ag mimotope DNA vaccine. To induce significant T cell response, we developed a recombinant adenovirus vaccine based on MG7-Ag mimotope and evaluated the efficacy and protective effects of heterologous prime-boost immunization protocol with an oral DNA vaccine previously developed. We found that both vaccines were able to elicit a significant humoral response against MG7-Ag, while the highest serum titre MG7 antibody was detected in mice immunized with the heterologous prime-boost immunization protocol. Enzyme-linked immunospot (ELISPOT) assay demonstrated that the heterologous prime-boost immunization strategy was more efficient in inducing T cell response than the homologous prime-boost strategy. In the tumour challenge assay, 2 of 5 mice immunized with the heterologous prime-boost protocol were tumour free, while none of the mice in homologous prime-boost groups or control groups was tumour free. Those tumour-bearing mice in the heterologous prime-boost regime had smaller tumour masses than their counterparts in the homologous prime-boost groups or control groups. Therefore, our study suggests that vaccines against MG7-Ag induce significant immune response against gastric cancer, and that the heterologous prime-boost protocol using different types of vaccines could achieve better protective effect than the homologous prime-boost protocol.     

伴有神经内分泌分化的乳腺梭形细胞癌

目的探讨乳腺伴有神经内分泌分化的梭形细胞癌的病理形态学和免疫表型特点及鉴别诊断。方法复习2500例乳腺癌切片,找出以梭形细胞占主要优势（〉80％）的癌5例,其中2例梭形细胞型导管内癌和3例梭形细胞型浸润癌。采用HE、阿辛蓝（AB）／PAS和网织染色,以及用癌胚抗原（CEA）、上皮膜抗原（EMA）、细胞角蛋白（CK7、3413E12、AE1／AE3）、神经元特异性烯醇化酶（NSE）、突触素、嗜铬蛋白（cg）A、Lue-7、波形蛋白,S-100、平滑肌肌动蛋白（SMA）、calponin、雌激素受体（ER）、孕激素受体（PR）、c—erbB-2、E-钙黏素、Ki-67、p53抗体进行免疫组织化学观察。其中4例有随访信息。结果患者平均年龄在68岁。镜下：5例癌细胞形态主要为长梭形的上皮样细胞,3例有少数胞质内空泡状细胞,4例可见散在AB阳性细胞。免疫组织化学5例均表达AE1／AE3、EMA、CEA、E-钙黏素和突触素,CK7有4例表达,NSE阳性3例,CgA和Lue7阳性2例,ER阳性4例,PR阳性2例,1例表达c-erbB-2,1例有灶状波形蛋白阳性。免疫组织化学结果显示2例梭形细胞型导管内癌和1例梭形细胞型浸润性癌是梭形细胞型的神经内分泌癌,另外2例梭形细胞型浸润性癌是伴有神经内分泌分化的化生性癌。随访3例存活（24～58个月）,1例27个月内死亡。结论上皮样梭形细胞和细胞内黏液的出现是乳腺伴有神经内分泌分化癌的一个形态学特点。梭形细胞神经内分泌型导管内癌需要和普通导管增生及导管内乳头状瘤鉴别。梭形细胞型的神经内分泌癌和伴神经内分泌分化的梭形细胞浸润性癌需要与梭形细胞肌上皮肿瘤、恶性黑色素瘤及某些软组织肿瘤鉴别。     

C4.4A蛋白在鳞状细胞癌和腺癌中的表达差异及其意义

目的探讨CA．4A蛋白表达在鳞癌和腺癌诊断和鉴别诊断中的意义。方法应用免疫组织化学SP法检测并观察不同部位来源、不同分化程度的157例鳞状细胞癌和177例腺癌中CA．4A蛋白的表达。结果157例鳞状细胞癌中有141例C4．4A蛋白呈阳性表达,而177例腺癌中只有8例可检测C4．4A蛋白的部分或少量散在表达。鳞癌和腺癌C4．4A蛋白表达差异有统计学意义（x^2=244．93,P=0．000）。不同分化程度的鳞癌和腺癌两两比较,其CA．4A蛋白表达差异均有统计学意义（P=0．000）。结论C4．4A蛋白可作为区分鳞癌和腺癌的一个有价值的诊断标志物,有助于上皮性肿瘤的诊断及鉴别诊断。     

乳腺癌术后上皮样血管肉瘤一例

患者女,70岁。因左上臂肿物8个月,于2005年7月15日入院。患者于1995年11月曾行左乳腺癌根治术,术后应用直线加速器放射治疗5周,化疗4个疗程。1999年春天开始左上臂肿胀,8个月前发现左上臂出现鸡蛋大肿物,无疼痛不适感,后肿物逐渐增大。体检:左上臂尺侧有一6cm×6cm×5cm 大小肿物,质韧,边界较清,表面光滑,活动度差。B 超:左上臂内侧软组织内探及一7cm×6cm×5cm 的实性低回声团块,边界清晰,内回声不均质,并可见多个小囊状液性回声区,肿块内及周边血流较丰富。术中见肿物约10cm×8cm×6cm 大小,张力大,切面呈蜂窝样,有血性液体溢出。     

髂腹股沟入路切断髂腰肌治疗髋臼骨折对术后髋关节功能的影响

目的:评价切断髂腰肌的髂腹股沟入路治疗髋臼骨折对髋关节功能的影响,探讨切断髂腰肌治疗髋臼骨折的可行性.方法:(1)选取本院解剖学教研室成年尸体标本4具,共8条完整髂腰肌标本,观察其腹股沟韧带下方部分的大体形态,肌、腱比例及切断前后显露的范围.(2)采用髂腹股沟入路治疗髋臼骨折13例,其中7例保留髂腰肌的完整性(Ⅰ组),6例切断髂腰肌(Ⅱ组),分别于术后1月、2月及6月评估屈髋肌力及术后并发症.结果:(1)髂腰肌在腹股沟韧带下方为肌、腱混杂结构,腱、肌比例平均1∶4.1,切断髂腰肌后显露范围明显扩大.(2)术后1个月Ⅱ组屈髋肌力较Ⅰ组差(P＜0.01);术后2个月两组肌力均恢复至4级以上,组间差异无统计学意义(P＞0.05);术后6个月所有患者屈髋肌力基本恢复正常.除1例髂腰肌切断患者术后并发下肢深静脉血栓形成外,其余患者无并发症.结论:切断髂腰肌对髋关节功能的影响是短暂而有限的;使用髂腹股沟入路处理髋臼骨折时,切断髂腰肌有利于骨折的显露及复位.