Pituitary fossa: chemical shift effect in MR imaging

The effect of chemical shift on magnetic resonance (MR) imaging of the pituitary fossa was studied. Healthy volunteers underwent conventional MR imaging of the pituitary fossa and then imaging with the frequency-encoding gradient reversed or with the phase- and frequency-encoding gradients interchanged. Comparison of the image pairs in each subject showed that the thin, black stripe evident at the water-fat interface within the pituitary fossa was altered when the gradients were changed. Therefore, the low-intensity signal within the pituitary fossa is a chemical shift misregistration effect.     

Anulus fibrosus in bulging intervertebral disks

In this investigation the association of radial tears of the anulus fibrosus and bulging of the intervertebral disk was studied. An index of disk bulging was measured in sagittal anatomic sections in 149 lumbar disks from 31 cadavers. The indexes of disk bulging were correlated with stages of disk development and the presence of an annular tear. The largest disk-bulging indexes were always associated with radial tears of the anulus. Eighty-four percent of the disks with radial tears had disk-bulging indexes greater than 2.5 mm. Most normal adult disks had an index of less than 2.5 mm. The results challenge the concept that the anulus fibrosus is intact in bulging disks, although ruptured in herniated disks.     

Cholesteryl-grafted functional amphiphilic poly(N-isopropylacrylamide-co-N-hydroxylmethylacrylamide): synthesis, temperature-sensitivity, self-assembly and encapsulation of a hydrophobic agent

A thermally responsive amphiphilic grafted copolymer comprised of hydroxyl-containing random poly(N-isopropylacrylamide-co-N-hydroxylmethylacrylamide) as the hydrophilic chain and cholesteryl groups as hydrophobic side arms was developed for the controlled release of hydrophobic drugs. The polymer was temperature-sensitive with a lower critical solution temperature of 40.5 degrees C and a critical micelle concentration of 4 mg/l. Dynamic light-scattering studies showed that the amphiphilic polymer self-assembled into micelles in aqueous media with their mean sizes in the range of 25-34 nm. Transmission electron microscope studies showed that the nanoparticles prepared from the micelle solutions exhibited multiple morphologies including unusual cubic and cuboids-like shapes, and normal spherical shapes, which could be controlled by the formation conditions. Wide-angle X-ray scattering studies showed that these nanoparticles were amorphous in nature but a small crystalline phase existed and the crystallinity of particles increased with the decrease of initial formation concentration. Pyrene was employed as a model hydrophobic agent to examine the encapsulation ability of the polymer with respect to hydrophobic agents in aqueous media. The loading level of the polymer with respect to pyrene was 4.4 mg/g, indicating that the thermally responsive amphiphilic polymer would be able to be used for the encapsulation of hydrophobic drugs.     

Osteopetrosis: MR characteristics at 1.5 T

Four patients with proved osteopetrosis (three with the infantile malignant form and one with the benign form) were examined with magnetic resonance imaging at 1.5 T. All patients were studied in the coronal and sagittal planes using both short and long repetition time/echo time sequences. The infantile malignant form was characterized by a complete lack of signal from the marrow alternating with a signal intensity equivalent to that of the intervertebral disks, resulting in a "stepladder" appearance. In the benign form or after successful marrow transplantation in the infantile malignant form, intermediate or high signal intensity in the vertebrae was noted, suggesting the presence of some marrow elements.     

基于清晰集定性比较分析的地方政府县域医共体创新实践影响因素及其组合路径分析

背景地方政府创新的影响因素分析一直是地方治理创新研究的重要议题。目的探究影响地方政府县域医共体创新实践的因素，并分析其组合路径。方法于2021年3月，以中国医院协会医共体分会举办的第二届"寻找县域医共体实践价值案例"评选活动的初选结果为案例源，将"政策创新类型"作为结果变量（中央主导型创新/地方回应型创新=0，地方自发型创新=1），以经济发展水平、行政层级、地理区位、问题属性及平台作为条件变量，采用清晰集定性比较分析（csQCA）法，通过必要条件分析、充分条件组合分析，探究影响地方政府县域医共体创新实践的因素并构建地方政府县域医共体创新实践的影响路径模型。结果5个条件变量一致性均<0.9，即经济发展水平、行政层级、地理区位、问题属性及平台均不是地方自发型创新的必要条件。条件变量组合分析（基于中间解）结果显示，共得到5组前因条件组合，分别为：经济发展水平*~地理区位*平台，行政层级*~地理区位*平台，经济发展水平*问题属性*平台，~经济发展水平*地理区位*~问题属性*平台，经济发展水平*行政层级*地理区位*问题属性（*表示"且"，~表示"非"）。5组前因条件组合一致性指标均为1，原始覆盖率为0.14~0.43，净覆盖率为0.14~0.43，总体覆盖率为1。地方政府县域医共体创新实践主要呈现出两类模式，即平台型创新模式和动机型创新模式。结论若要实现高水平的医共体创新实践，应该关注政策与当地经济发展水平之间的强相关性，激活地方政府的主动创新意愿，以及加强对县域医共体的平台支持。本研究对于理解地方政府县域医共体创新实践的机理乃至地方政府创新都具有一定价值。