The application of metal artifact reduction (MAR) in CT scans for radiation oncology by monoenergetic extrapolation with a DECT scanner

Metal artifacts in computed tomography CT images are one of the main problems in radiation oncology as they introduce uncertainties to target and organ at risk delineation as well as dose calculation. This study is devoted to metal artifact reduction (MAR) based on the monoenergetic extrapolation of a dual energy CT (DECT) dataset. In a phantom study the CT artifacts caused by metals with different densities: aluminum (ρ_Al=2.7 g/cm³), titanium (ρ_Ti=4.5 g/cm³), steel (ρ_steel=7.9 g/cm³) and tungsten (ρ_W=19.3 g/cm³) have been investigated. Data were collected using a clinical dual source dual energy CT (DECT) scanner (Siemens Sector Healthcare, Forchheim, Germany) with tube voltages of 100 kV and 140 kV (Sn). For each tube voltage the data set in a given volume was reconstructed. Based on these two data sets a voxel by voxel linear combination was performed to obtain the monoenergetic data sets. The results were evaluated regarding the optical properties of the images as well as the CT values (HU) and the dosimetric consequences in computed treatment plans. A data set without metal substitute served as the reference. Also, a head and neck patient with dental fillings (amalgam ρ=10 g/cm³) was scanned with a single energy CT (SECT) protocol and a DECT protocol. The monoenergetic extrapolation was performed as described above and evaluated in the same way. Visual assessment of all data shows minor reductions of artifacts in the images with aluminum and titanium at a monoenergy of 105 keV. As expected, the higher the densities the more distinctive are the artifacts. For metals with higher densities such as steel or tungsten, no artifact reduction has been achieved. Likewise in the CT values, no improvement by use of the monoenergetic extrapolation can be detected. The dose was evaluated at a point 7 cm behind the isocenter of a static field. Small improvements (around 1%) can be seen with 105 keV. However, the dose uncertainty remains of the order of 10% to 20%. Thus, the improvement is not significant for radiotherapy planning. For amalgam with a density between steel and tungsten, monoenergetic data sets of a patient do not show substantial artifact reduction. The local dose uncertainties around the metal artifact determined for a static field are of the order of 5%. Although dental fillings are smaller than the phantom inserts, metal artifacts could not be reduced effectively. In conclusion, the image based monoenergetic extrapolation method does not provide efficient reduction of the consequences of CT-generated metal artifacts for radiation therapy planning, but the suitability of other MAR methods will be subsequently studied.     

Validation of a low-cost laser scanner device for the assessment of three-dimensional facial anatomy in living subjects

The present study compared the reliability of a low-cost laser scanner device to an already-validated stereophotogrammetric instrument. Fifty volunteers underwent duplicate facial scans through laser scanner and stereophotogrammetry. Intra- and inter-instrument reproducibility of linear distances, angles, facial surface area and volume was verified through the Bland–Altman test and calculation of absolute (TEM) and relative (rTEM) technical errors of measurement; rTEM was then classified as follows: <1% excellent; 1–3.9% very good; 4–6.9% good; 7–9.9% moderate; >10% poor. The scans performed through different devices were registered and superimposed to calculate the root mean square (RMS) (point-to-point) distance between the two surfaces. The same protocol was applied to a mannequin head. In inter-instruments comparison, 12/26 measurements showed a “good” rTEM; 5 were “very good”. In intra-instrument comparison, most performances worsened, with only 10 of 26 measurements classified as “good” and “very good”. All the measurements made on mannequin scans were at least “good”, and 14/26 were “very good”. Surface area was “very good” only in intra-instrument comparison; conversely, volumes were poorly repeatable for all the comparisons. On average, RMS point-to-point distances were 0.65 mm (inter-devices comparison), 0.56 mm (mannequin scans), 0.42 mm (intra-device comparison). In conclusion, the low-cost laser scan device can be reliably applied to inanimate objects, but does not meet the standards for three-dimensional facial acquisition on living persons.     

麻杏二陈汤煮散质量标准

目的:建立麻杏二陈汤煮散质量标准。方法:采用薄层色谱法(TLC)对煮散处方中的炙麻黄、苦杏仁、射干、陈皮进行定性鉴别,采用高效液相色谱法(HPLC)对煮散中的射干苷和橙皮苷含量进行同时测定。结果:TLC法能定性检出炙麻黄、苦杏仁、射干、陈皮,斑点清晰,且阴性对照无干扰。HPLC法测定射干苷在12.0~120.0 mg·L-1呈良好的线性关系(r=0.999 8),平均回收率100.00%(RSD 1.9%);橙皮苷在6.6~66.0 mg·L-1呈良好的线性关系(r=0.999 9),平均回收率98.16%(RSD 1.8%)。结论:该研究所建立的定性、定量检测方法操作简便,结果准确可靠,重复性好,能有效地控制麻杏二陈汤煮散的质量。     

南柴胡与常见混伪品的鉴别方法研究

 目的 研究建立南柴胡与混伪品锥叶柴胡的鉴别方法。方法 采用植物鉴定、药材性状鉴别、薄层色谱鉴别及DNA分子鉴定方法,对南柴胡及其混伪品锥叶柴胡进行鉴别研究。结果 南柴胡与锥叶柴胡在植物形态、药材性状、薄层色谱方面有较明显的区别,DNA分子鉴定表明,南柴胡和锥叶柴胡的最小种间K-2-P距离大于种内最大K-2-P距离,NJ树中柴胡的不同基原样品各聚为一支,南柴胡与锥叶柴胡等其他混伪品分别表现出单系性,可明显区分开。结论 本实验在对南柴胡及锥叶柴胡原植物形态学比较研究的基础上,找出了两者主要的鉴别特征,同时采用药材性状鉴别、薄层色谱鉴别与DNA分子鉴定手段相结合的方式模式,建立了南柴胡和锥叶柴胡的鉴别要点。DNA分子鉴定技术是传统鉴别技术的重要补充,具有很大的潜力和应用前景。     

双能量CT虚拟平扫图像检测泌尿系结石

[摘要]目的探讨双能量CT虚拟平扫（VNCT）检测泌尿系结石的应用价值。方法对71例泌尿系结石患者行双源CT尿路造影,依次进行普通平扫（CNCT）和动脉期、实质期常规扫描及排泄期双能量扫描。对排泄期双能量扫描图像去碘,生成VNCT图像,比较CNCT、VNCT及排泄期扫描图像对结石的显示情况,采用Kappa检验对VNCT及CNCT图像上结石大小进行一致性分析。结果在CNCT图像上共发现152个结石。以此为参考标准,VNCT图像对1-2mm结石和≥3mm结石的检出率分别为84．21％（16／19）和100％（133／133）,差异有统计学意义（X^2=14．039,P〈0．001）。排泄期图像对结石的检出率为65．13％（99／152）。与CNCT图像比较,VNCT图像上1-2mm、3-4mm和5-6mm的结石的大小一致性一般（Kappa值=0．425、0．575和0．542）,7-10mm和≥11mm结石的大小一致性好（Kappa值=0．894和0．996）。结论CT尿路造影中双能量VNCT图像可用于检测泌尿系结石,特别是≥3mm的结石。     

Role of the laboratory in monitoring patients receiving dual antiplatelet therapy

Introduction: The increasing demand for therapeutic monitoring in patients receiving antiplatelet therapy has been paralleled by the development of instruments and tests whose clinical usefulness is still under debate. We devised a laboratory approach to detect patients with antiplatelet resistance at risk to develop thrombotic events. Methods: One hundred and eighty patients, under aspirin and clopidogrel after angioplasty and stent implantation, were studied by PFA100^® with collagen/epinephrine (CoEPI, cutoff 165s) cartridge and by Multiplate^® using arachidonic acid (ASPItest, pos < 862AUC), ADP (ADPtest, pos < 417AUC), and collagen (COLtest, pos < 607AUC). Results: Only 67 of 173 patients with ASPI < 862 displayed a prolonged CoEPI and up to 65 patients had normal CoEPI despite ASPI < 300. Patients with ASPI < 300 had significantly lower COL than patients with ASPI > 300. One hundred and thirty‐eight patients displaying ADP < 417 had significantly lower COL than those with ADP > 417. Association between COL and ADP remained after ASPI stratification: in patients with suboptimal (ASPI 300–892) or maximal (ASPI < 300) response to aspirin, having ADP < 417 (clopidogrel responsive) increased COL positivity, respectively, from 9.5 to 58.8% and from 47.6 to 82.7%. Conclusion: A combination of specific tests may be useful in identifying higher‐risk patients with poor compliance or drug resistance who potentially may benefit from therapy change.     

双能成像技术的最新进展

自从CT发明后,能谱信息就开始被用来对物质进行区分和描述。为了实现一台双能CT,其设计需要满足对放射源和探测器的要求,本文简单介绍了目前市场上三款双能CT,并着重观察这三种不同设计的双能CT对扫描剂量的影响。     

双解剖钢板治疗严重胫骨平台粉碎性骨折39例报告

目的探讨双解剖钢板治疗严重胫骨平台粉碎性骨折的临床疗效。方法将2008年8月至2011年11月我院收治79例胫骨平台粉碎性骨折患者随机分为观察组和对照组,观察组39例采用双解剖钢板治疗,对照组40例采用传统手术方法(松质骨螺钉)治疗,比较两组患者治疗的临床疗效。结果观察组治疗优良率为92.31%,对照组治疗优良率为62.50%,观察组明显优于对照组,两组差异具有统计学意义(P<0.05)。结论双解剖钢板治疗严重胫骨平台粉碎性骨折固定牢固,膝关节恢复良好,疗效显著,值得临床应用与推广。