Reliable and computationally efficient maximum-likelihood estimation of "proper" binormal ROC curves

RATIONALE AND OBJECTIVES: Estimation of ROC curves and their associated indices from experimental data can be problematic, especially in multireader, multicase (MRMC) observer studies. Wilcoxon estimates of area under the curve (AUC) can be strongly biased with categorical data, whereas the conventional binormal ROC curve-fitting model may produce unrealistic fits. The "proper" binormal model (PBM) was introduced by Metz and Pan to provide acceptable fits for both sturdy and problematic datasets, but other investigators found that its first software implementation was numerically unstable in some situations. Therefore, we created an entirely new algorithm to implement the PBM. MATERIALS AND METHODS: This paper describes in detail the new PBM curve-fitting algorithm, which was designed to perform successfully in all problematic situations encountered previously. Extensive testing was conducted also on a broad variety of simulated and real datasets. Windows, Linux, and Apple Macintosh OS X versions of the algorithm are available online at http://xray.bsd.uchicago.edu/krl/. RESULTS: Plots of fitted curves as well as summaries of AUC estimates and their standard errors are reported. The new algorithm never failed to converge and produced good fits for all of the several million datasets on which it was tested. For all but the most problematic datasets, the algorithm also produced very good estimates of AUC standard error. The AUC estimates compared well with Wilcoxon estimates for continuously distributed data and are expected to be superior for categorical data. CONCLUSION: This implementation of the PBM is reliable in a wide variety of ROC curve-fitting tasks.     

桃花红色素提取方法及性质研究

本文研究了桃花中提取红色素的最佳条件,并就pH值、温度、氧化剂、还原剂、食品添加剂和金属离子对色素性质的影响进行了讨论。     

常法与变法——顽固性脘腹痛证的辨治体会

临床辨治脘腹顽痛证医案两则,一以火土合德(益火暖土法)取效.一从脏腑法时用药建功.认为顽固性脘腹痛证常法不效,当辨证更易其法,才能切中病机.     

指掌侧固有动脉的应用解剖

目的：通过对指掌侧固有动脉的掌侧分支分布情况的研究,为临床上取手指掌侧皮瓣修复手指提供解剖学依据。方法：通过对手指血管进行灌注,解剖及测量指掌侧固有动脉掌横支与皮纹的距离和管径。结果：近侧掌横支距皮纹为(6．16±1．51)mm,外径为(0．4l±0．08)mm。中间掌横支距皮纹为(4．34±1．40)mm,外径为(0．40±0．09)mm。远侧掌横支距皮纹为(5．98±2．30)mm,外径为(0．42±0．09)mm。近侧掌横支与中间掌横支之间的距离为(26．62±2．08)mm,中间掌横支与远侧掌横支之间的距离为(10．33±2．77)mm。结论：在手指修复取皮瓣时,要考虑掌横支的特点及分布情况。     

Comparison of Bolus Versus Dual-Syringe Administration Systems on Glass Yttrium-90 Microsphere Deposition in an In Vitro Microvascular Hepatic Tumor Model

PurposeTo utilize an in vitro microvascular hepatic tumor model to compare the deposition characteristics of glass yttrium-90 microspheres using the dual-syringe (DS) and traditional bolus administration methods.Materials and MethodsThe microvascular tumor model represented a 3.5-cm tumor in a 1,400-cm³ liver with a total hepatic flow of 160 mL/min and was dynamically perfused. A microcatheter was placed in a 2-mm artery feeding the tumor model and 2 additional nontarget arteries. Glass microspheres with a diameter of 20–30 μm were administered using 2 methods: (a) DS delivery at a concentration of 50 mg/mL in either a single, continuous 2-mL infusion or two 1-mL infusions and (b) bolus delivery (BD) of 100 mg of microspheres in a single 3-mL infusion.ResultsOverall, the degree of on-target deposition of the microspheres was 85% ± 11%, with no significant differences between the administration methods. Although the distal penetration into the tumor arterioles was approximately 15 mm (from the second microvascular bifurcation of the tumor model) for all the cases, the distal peak particle counts were significantly higher for the DS delivery case (approximately 5 × 10⁵ microspheres achieving distal deposition vs 2 × 10⁵ for the BD case). This resulted in significantly higher deposition uniformity within the tumor model (90% for the DS delivery case vs 80% for the BD case, α = 0.05).ConclusionsThe use of this new in vitro microvascular hepatic tumor model demonstrated that the administration method can affect the deposition of yttrium-90 microspheres within a tumor, with greater distal deposition and more uniform tumor coverage when the microspheres are delivered at consistent concentrations using a DS delivery device. The BD administration method was associated with less favorable deposition characteristics of the microspheres.