Contrast-material-enhanced MR urography in evaluation of postoperative lower urinary tract fistulae and leakages

Urinary fistulas and leakages of lower urinary tract are serious complications of various surgical procedures. Radiologists need to have enough information about these situations to perform precise diagnosis and treatment. Various techniques [such as intravenous pyelography, ultrasound, computed tomography (CT), CT urography, cystoscopy, cystography and magnetic resonance (MR) imaging] are used for the diagnosis of these conditions. Application of all these techniques reduces the comfort and cooperation of the patients and increases the cost. Here we present four postoperative patients with lower urinary tract fistula or leakage. To the best of our knowledge, there is no report regarding the use of contrast-material-enhanced MR urography (CE-MRU) in the demonstration of postoperative lower urinary tract fistulae and leakages. In conclusion, CE-MRU could show the existence and location of the urinary fistulae and leakages clearly without the need for another investigation technique, as described in our patients. Also, CE-MRU is a safe and relatively inexpensive technique that avoids exposure to radiation as well as nephrotoxic and more allergic contrast-material administration.     

Practical considerations in T1 mapping of prostate for dynamic contrast enhancement pharmacokinetic analyses

There are many challenges in developing robust imaging biomarkers that can be reliably applied in a clinical trial setting. In the case of dynamic contrast-enhanced (DCE) MRI, one such challenge is to obtain accurate precontrast T₁ maps for subsequent use in two-compartment pharmacokinetic models commonly used to fit the MR enhancement time courses. In the prostate, a convenient and common approach for this task has been to use the same 3D spoiled gradient-echo sequence used to collect the DCE data, but with variable flip angles (VFAs) to collect data suitable for T₁ mapping prior to contrast injection. However, inhomogeneous radiofrequency conditions within the prostate have been found to adversely affect the accuracy of this technique. Herein we demonstrate the sensitivity of DCE pharmacokinetic parameters to precontrast T₁ values and examine methods to improve the accuracy of T₁ mapping with flip angle-corrected VFA SPGR methods, comparing T₁ maps from such methods with “gold standard” reference T₁ maps generated with saturation recovery experiments performed with fast spin-echo (FSE) sequences.     

基于目标任务性能的红外系统评价新方法

分析了美国对红外系统进行评价时的最准确的目标任务性能(TTP)模型。通过阐述TTP建模的理论依据,解释了它相对于Johnson准则的本质区别,主要在于系统阈值对比度概念和对被人眼感知的所有有效频率的积分。介绍了如何将TTP模型过渡到任务性能概率的实验过程,并通过实验数据和TTP的基本理念总结了它相对于Johnson准则的特点。     

Neutron Interferometer with very thin Lamellae

We describe the manufacturing and testing of a monolithic perfect crystal interferometer with very thin lamellae, optimized for neutron phase contrast imaging where high spatial phase resolution is required. The two main characteristics of our new interferometer design are thin lamellae (t=0.56 mm) for beam splitter S and analyzer A, and mirrors M1, M2 of twice the thickness (t_M=1.12 mm) of Sand A. The different stages of crystal preparation and the successful test with X‐rays are reported.     

Barrier-breaking effects of ultrasonic cavitation for drug delivery and biomarker release

Recently, emerging evidence has demonstrated that cavitation actually creates important bidirectional channels on biological barriers for both intratumoral drug delivery and extratumoral biomarker release. To promote the barrier-breaking effects of cavitation for both therapy and diagnosis, we first reviewed recent technical advances of ultrasound and its contrast agents (microbubbles, nanodroplets, and gas-stabilizing nanoparticles) and then reported the newly-revealed cavitation physical details. In particular, we summarized five types of cellular responses of cavitation in breaking the plasma membrane (membrane retraction, sonoporation, endocytosis/exocytosis, blebbing and apoptosis) and compared the vascular cavitation effects of three different types of ultrasound contrast agents in breaking the blood-tumor barrier and tumor microenvironment. Moreover, we highlighted the current achievements of the barrier-breaking effects of cavitation in mediating drug delivery and biomarker release. We emphasized that the precise induction of a specific cavitation effect for barrier-breaking was still challenged by the complex combination of multiple acoustic and non-acoustic cavitation parameters. Therefore, we provided the cutting-edge in-situ cavitation imaging and feedback control methods and suggested the development of an international cavitation quantification standard for the clinical guidance of cavitation-mediated barrier-breaking effects.