木本植物木质部空穴和栓塞化研究(综述)

木本植物木质部空穴和栓塞化现象的发现至今已近80年历史,国外学者对此做了较多的研究,国内此方面的研究极少。木质部空穴和栓塞化研究是木本植物体内水分传输研究的前沿所在,不同学者在不同地区对不同材料的研究结果各异,争议颇多。本文对这一研究方向近年来的资料作了概括和总结,包括栓塞化现象的发现、检测方法、诱因及形成机理、木质部栓塞化同输水结构间的关系等方面。     

Higher patient doses through X-ray imaging procedures

Medical imaging using X-rays has been one of the most popular imaging modalities ever since the discovery of X-rays 125 years ago. With unquestionable benefits, concerns about radiation risks have frequently been raised. Computed tomography (CT) and fluoroscopic guided interventional procedures have the potential to impart higher radiation exposure to patients than radiographic examinations. Despite technological advances, there have been instances of increased doses per procedure mainly because of better diagnostic information in images. However, cumulative dose from multiple procedures is creating new concerns as effective doses >100 mSv are not uncommon. There is a need for action at all levels. Manufacturers must produce equipment that can provide a quality diagnostic image at substantially lesser dose and better implementation of optimization strategies by users. There is an urgent need for the industry to develop CT scanners with sub-mSv radiation dose, a goal that has been lingering. It appears that a new monochromatic X-ray source will lead to replacement of X-ray tubes all over the world in coming years and will lead to a drastic reduction in radiation doses. This innovation will impact all X-ray imaging and will help dose reduction. For interventional procedures, the likely employment of robotic systems in practice may drastically reduce radiation exposures to operators- but patient exposure will still remain an issue. Training needs always need to be emphasized and practiced.     

Conversion factors for effective dose and organ doses with the air kerma area product in patients undergoing percutaneous transhepatic biliary drainage and trans arterial chemoembolization

Conversion factors used to estimate effective (E) and organ doses (H_T) from air Kerma area product (KAP) are required to estimate population doses in percutaneous transhepatic biliary drainage (PTBD) and trans arterial chemoembolization (TACE) interventional procedures.In this study, E and H_T for ten critical organs/tissues, were derived in 64 PTBD and 48 TACE procedures and in 14,540 irradiation events from dosimetric, technical and geometrical information included in the radiation dose structured report using the PCXMC Monte Carlo model, and the ICRP 103 organ weighting factors. Conversion factors of: 0.13; 0.19; 0.26 and 0.32 mSv Gy⁻¹ cm⁻² were established for irradiation events characterized by a Cu filtration of 0.0; 0.1; 0.4 and 0.9 mm, respectively. While a single coefficient of conversion is not able to provide estimates of E with enough accuracy, a high agreement is obtained between E estimated through Monte Carlo methods and E estimated through E/KAP conversion factors accounting separately for the different modes of fluoroscopy and the fluorography component of the procedures.An algorithm for the estimation of effective and organ doses from KAP has been established in biliary procedures which considers the Cu filtration in the X-ray irradiation events. A similar algorithm could be easily extended to other interventional procedures and incorporated in radiation dose monitoring systems to provide dosimetric estimates automatically with enough accuracy to assess population doses.     

PTVE 与TIPS治疗肝硬化门静脉高压合并食管胃底静脉曲张破裂出血 的疗效比较

目的:研究经皮胃底曲张静脉栓塞术(PTVE)和经颈静脉肝内门体分流术(TIPS)治疗肝硬化门静脉高压合并食管胃底静脉曲张破裂出血的临床疗效,为临床治疗提供依据。方法:选取2001年4月到2015年4月我院肝硬化门静脉高压合并食管胃底静脉曲张破裂患者169例,根据手术方式分为PTVE组(行PTVE治疗)141例和TIPS组(行TIPS治疗)28例,比较两组术前、术后门静脉压力,术前、术后3个月、6个月以及1年两组Child-Pugh评分、白蛋白以及直接胆红素,并比较两组再出血和肝性脑病发生率。结果:TIPS组术后门静脉压力较术前显著降低,比较差异具有统计学意义(P0.05),术后PTVE组及TIPS组组间比较差异具有统计学意义(P0.05);两组术前和术后各时间直接胆红素无统计学意义(P0.05);PTVE组术后1年白蛋白水平显著升高,与术前和TIPS组比较差异具有统计学意义(P0.05),TIPS组术后白蛋白有所升高,但各时间比较差异无统计学意义(P0.05),PTVE组术后各时间Child-Pugh评分较术前明显改善,比较差异具有统计学意义(P0.05),TIPS组术后3个月和术后6个月Child-Pugh评分较术前明显改善,比较差异具有统计学意义(P0.05);两组术后再出血发生率比较无统计学意义(P0.05),PTVE组肝性脑病发生率显著低于TIPS组,比较差异具有统计学意义(P0.05)。结论:PTVE和TIPS治疗肝硬化门静脉高压合并食管胃底静脉曲张破裂出血效果相当,TIPS能显著降低门静脉压,PTVE能降低肝性脑病的发生率,改善患者Child-Pugh评分。     

磁共振成像应用于检测胎盘植入介入治疗

为了探讨磁共振成像(magnetic resonance imaging, MRI)在胎盘植入介入治疗中的诊断作用和为临床治疗提供依据,本研究选取30例于2012年6月至2015年12月间在我院进行介入治疗的胎盘植入患者作为研究对象,根据病理诊断标准,分析患者胎盘植入介入治疗前后的MRI检查结果。结果显示,粘连性胎盘的敏感性和特异性分别为77.5%和90.2%,植入性胎盘的敏感性和特异性分别为75.5%和87.7%,穿透性胎盘的敏感性和特异性分别为85%和100%。最好的预测胎盘植入的MRI特征是在T2W磁共振成像(T2W-MRI)序列上存在暗色的胎盘内条带。介入治疗1年后复查时,发现患者子宫恢复为正常大小,宫腔内的胎盘组织基本消失,宫壁与植入胎盘融合、宫腔内膜线和子宫结合带的信号完整。综上结果,说明MRI可作为检测胎盘植入可靠性和可重复性的工具,并且能够显示胎盘植入部位及子宫肌层受侵程度,可用于评价胎盘植入介入治疗的疗效。     

Radioprotection of eye lens using protective material in neuro cone-beam computed tomography: Estimation of dose reduction rate and image quality

PurposeIn cerebral angiography, for diagnosis and interventional neuroradiology, cone-beam computed tomography (CBCT) scan is frequently performed for evaluating brain parenchyma, cerebral hemorrhage, and cerebral infarction. However, the patient’s eye lens is more frequently exposed to excessive doses in these scans than in the previous angiography and interventional neuroradiology (INR) procedures. Hence, radioprotection for the lenses is needed. This study selects the most suitable eye lens protection material for CBCT from among nine materials by evaluating the dose reduction rate and image quality.MethodsTo determine the dose reduction rate, the lens doses were measured using an anthropomorphic head phantom and a real-time dosimeter. For image quality assessment, the artifact index was calculated based on the pixel value and image noise within various regions of interest in a water phantom.ResultsThe protective materials exhibited dose reduction; however, streak artifacts were observed near the materials. The dose reduction rate and the degree of the artifact varied significantly depending on the protective material. The dose reduction rates were 14.6%, 14.2%, and 26.0% when bismuth shield: normal (bismuth shield in the shape of an eye mask), bismuth shield: separate (two separate bismuth shields), and lead goggles were used, respectively. The “separate” bismuth shield was found to be effective in dose reduction without lowering the image quality.ConclusionWe found that bismuth shields and lead goggles are suitable protective devices for the optimal reduction of lens doses.     

介入治疗成人非创伤性股骨头缺血性坏死的疗效分析

目的：分析介入治疗对于成人非创伤性股骨头缺血性坏死的疗效。方法：采用介入方法治疗95例共117髋非创伤性股骨头缺血性坏死。对比介入治疗前后DSA造影分型结果及血供异常例数。结果：117患髋中,Ia型的31病髋中,11髋（35．48％）介入治疗后动脉主干再通;Ib型的27髋中,24髋（88．89％）介入治疗后分支再通;II型的11髋中,5髋（45．45％）实质期股骨头缺损面积缩小;III型的10髋中,8髋（80．00％）静脉期见股骨头浓密染色明显减轻;Ⅳ型的33髋中,28髋（84．85％）可见动脉主干再通、分支增粗、实质期股骨头缺损面积缩小和静脉期股骨头染色减轻等。治疗前117病髋异常率为95．73％。经过介入治疗后,异常率为30．77％。治疗后异常率明显低于治疗前异常率（P〈0．01）。结论：介入治疗可有效改善非创伤性股骨头缺血性坏死血供异常,增加股骨头血供,具有操作简单、创伤小、疗效确切等优点。关键阗：股骨头缺血性坏死;介入治疗;数字减影血管造影     

手术切除与介入栓塞治疗肝癌术后复发患者的临床对比研究

目的:比较手术切除与介入栓塞治疗肝癌术后复发患者的临床疗效。方法:选择2010年6月到2011年6月本院收治的92例肝癌手术切除术后复发患者,按随机数字表法分为手术切除组和介入栓塞组,各46例。手术切除组患者给予再次切除治疗,介入栓塞组患者给予介入栓塞治疗。记录并比较两组患者治疗后1年、3年及5年的生存率。检测并比较两组患者治疗前后血清肝纤维化指标,包括血清透明质酸(HA)、层黏蛋白(LN)、人Ⅲ型前胶原(HPC-Ⅲ)及IV型胶原(IV-C)水平。检测并比较两组患者治疗前后血清白细胞(WBC)、甲胎蛋白(AFP)及癌胚抗原(CEA)水平。结果:手术切除组患者治疗后1年、3年、5年的生存率均明显高于介入栓塞组,差异均具有统计学意义(P0.05)。治疗后,介入栓塞组血清HA、LN、HPC-Ⅲ及IV-C明显高于治疗前,且均明显高于手术切除组,差异均具有统计学意义(P0.05)。两组患者治疗后血清WBC、AFP及CEA水平均明显低于治疗前,且手术切除组患者血清WBC明显高于介入栓塞组,而血清AFP、CEA水平明显低于介入栓塞组,差异均具有统计学意义(P0.05)。结论:手术切除治疗肝癌术后复发能够明显提高患者生存率,降低肝纤维化程度,改善血清AFP及CEA水平,值得在临床上推广应用。     

Occupational exposures during abdominal fluoroscopically guided interventional procedures for different patient sizes — A Monte Carlo approach

In this study we evaluated the occupational exposures during an abdominal fluoroscopically guided interventional radiology procedure. We investigated the relation between the Body Mass Index (BMI), of the patient, and the conversion coefficient values (CC) for a set of dosimetric quantities, used to assess the exposure risks of medical radiation workers. The study was performed using a set of male and female virtual anthropomorphic phantoms, of different body weights and sizes. In addition to these phantoms, a female and a male phantom, named FASH3 and MASH3 (reference virtual anthropomorphic phantoms), were also used to represent the medical radiation workers. The CC values, obtained as a function of the dose area product, were calculated for 87 exposure scenarios. In each exposure scenario, three phantoms, implemented in the MCNPX 2.7.0 code, were simultaneously used. These phantoms were utilized to represent a patient and medical radiation workers. The results showed that increasing the BMI of the patient, adjusted for each patient protocol, the CC values for medical radiation workers decrease. It is important to note that these results were obtained with fixed exposure parameters.     

Feasibility of setting up generic alert levels for maximum skin dose in fluoroscopically guided procedures

PurposeThe feasibility of setting-up generic, hospital-independent dose alert levels to initiate vigilance on possible skin injuries in interventional procedures was studied for three high-dose procedures (chemoembolization (TACE) of the liver, neuro-embolization (NE) and percutaneous coronary intervention (PCI)) in 9 European countries.MethodsGafchromic® films and thermoluminescent dosimeters (TLD) were used to determine the Maximum Skin Dose (MSD). Correlation of the online dose indicators (fluoroscopy time, kerma- or dose-area product (KAP or DAP) and cumulative air kerma at interventional reference point (K_a,r)) with MSD was evaluated and used to establish the alert levels corresponding to a MSD of 2 Gy and 5 Gy. The uncertainties of alert levels in terms of DAP and K_a,r, and uncertainty of MSD were calculated.ResultsAbout 20–30% of all MSD values exceeded 2 Gy while only 2–6% exceeded 5 Gy. The correlations suggest that both DAP and K_a,r can be used as a dose indicator for alert levels (Pearson correlation coefficient p mostly >0.8), while fluoroscopy time is not suitable (p mostly <0.6). Generic alert levels based on DAP (Gy cm²) were suggested for MSD of both 2 Gy and 5 Gy (for 5 Gy: TACE 750, PCI 250 and NE 400). The suggested levels are close to the lowest values published in several other studies. The uncertainty of the MSD was estimated to be around 10–15% and of hospital-specific skin dose alert levels about 20–30% (with coverage factor k = 1).ConclusionsThe generic alert levels are feasible for some cases but should be used with caution, only as the first approximation, while hospital-specific alert levels are preferred as the final approach.