Preliminary investigation of respiratory self-gating for free-breathing segmented cine MRI.

Segmented cine MRI generally requires breath-holding, which can be problematic for many patients. Navigator echo techniques, particularly successful for free-breathing coronary MRA, are incompatible with the acquisition strategies and SSFP pulse sequences commonly used for cine MRI. The purpose of this work is to introduce a new self-gating technique deriving respiratory gating information directly from the raw imaging data acquired for segmented cine MRI. The respiratory self-gating technique uses interleaved radial k-space sampling to provide low-resolution images in real time during the free-breathing acquisition that are compared to target expiration images. Only the raw data-producing images with high correlation to the target images are included in the final high-resolution reconstruction. The self-gating technique produced cine series with no significant differences in quantitative image sharpness to series produced using comparable breath-held techniques. Because of the difficulties associated with breath-holding, the respiratory self-gating technique represents an important practical advance for cardiac MRI. , Inc.     

Diffusion-weighted magnetic resonance imaging in rat kidney using two-dimensional navigated,interleaved echo-planar imaging at 7.0 T

The purpose of this study was to investigate the feasibility of two-dimensional (2D) navigated, interleaved multishot echo-planar imaging (EPI) to enhance kidney diffusion-weighted imaging (DWI) in rats at 7.0 T. Fully sampled interleaved four-shot EPI with 2D navigators was tailored for kidney DWI (Sprague–Dawley rats, n = 7) on a 7.0-T small bore preclinical scanner. The image quality of four-shot EPI was compared with T₂-weighted rapid acquisition with relaxation enhancement (RARE) (reference) and single-shot EPI (ss-EPI) without and with parallel imaging (PI). The contrast-to-noise ratio (CNR) was examined to assess the image quality for the EPI approaches. The Dice similarity coefficient and the Hausdorff distance were used for evaluation of image distortion. Mean diffusivity (MD) and fractional anisotropy (FA) were calculated for renal cortex and medulla for all DWI approaches. The corticomedullary difference of MD and FA were assessed by Wilcoxon signed-rank test. Four-shot EPI showed the highest CNR among the three EPI variants and lowest geometric distortion versus T₂-weighted RARE (mean Dice: 0.77 for ss-EPI without PI, 0.88 for ss-EPI with twofold undersampling, and 0.92 for four-shot EPI). The FA map derived from four-shot EPI clearly identified a highly anisotropic region corresponding to the inner stripe of the outer medulla. Four-shot EPI successfully discerned differences in both MD and FA between renal cortex and medulla. In conclusion, 2D navigated, interleaved multishot EPI facilitates high-quality rat kidney DWI with clearly depicted intralayer and interlayer structure and substantially reduced image distortion. This approach enables the anatomic integrity of DWI-MRI in small rodents and has the potential to benefit the characterization of renal microstructure in preclinical studies.     

三维超声下颌定位技术在(牙合)垫治疗颞颌关节绞锁中的应用

目的应用三维超声下颌定位技术,观察颞颌关节绞锁应用于（牙合）垫治疗前后髁突运动轨迹的变化。方法对21例单侧颞颌关节绞锁患者使用下颌稳定性（牙合）垫治疗。运用三维超声下颌定位技术观察绞锁性颞颌关节在（牙合）垫治疗前后健患侧髁突运动轨迹在最大开口运动、最大前伸运动和侧方运动中运动范围的变化。结果通过三维超声下颌定位技术可观察到患者髁突运动轨迹表现为双侧的不对称性。患侧关节在（牙合）垫治疗前后运动范围的比较发现,在最大开口运动的矢状位、冠状位、轴位的髁突运动范围增大（P〈0．05）;前伸和侧方运动的矢状位、冠状位的髁突运动范围增大（P〈0．05）。结论（牙合）垫治疗后绞锁性颞颌关节健患侧髁突的运动轨迹更加对称,患侧关节运动轨迹的范围增大。三维超声下颌定位技术可作为（牙合）垫治疗颞颌关节绞锁髁突运动轨迹改变有效的观测与评价手段。     

Impact of a Hybrid Lung Cancer Screening Model on Patient Outcomes and Provider Behavior

BackgroundLung cancer screening (LCS) implementation is complicated by the Centers for Medicare and Medicaid Services reimbursement requirements of shared decision-making and tobacco cessation counseling. LCS programs can utilize different structures to meet these requirements, but the impact of programmatic structure on provider behavior and screening outcomes is poorly described.Patients and MethodsIn a retrospective chart review of 624 patients in a hybrid structure, academic LCS program, we compared characteristics and outcomes of primary care provider (PCP)- and specialist-screened patients. We also assessed the impact of the availability of an LCS specialty clinic and best practice advisory (BPA) on PCP ordering patterns using electronic medical record generated reports.ResultsDuring the study period of July 1, 2014 through June 30, 2018, 48% of patients were specialist-screened and 52% were PCP-screened; there were no clinically relevant differences in patient characteristics or screening outcomes between these populations. PCPs demonstrate distinct practice patterns when offered the choice of specialist-driven or PCP-driven screening. Increased exposure to a LCS BPA is associated with increased PCP screening orders. The addition of a nurse navigator into the LCS program increased documentation of shared decision-making and tobacco cessation counseling to > 95% and virtually eliminated screening of ineligible patients.ConclusionsSystematic interventions including a BPA and nurse navigator are associated with increased screening and improved program quality, as evidenced by reduced screening of ineligible patients, increased lung cancer risk of the screened population, and improved compliance with LCS guidelines. Individual PCPs demonstrate clear preferences regarding LCS that should be considered in program design.     

全心冠状动脉磁共振成像初步探讨

目的：探讨自由呼吸导航全心冠状动脉磁共振成像（CMRA）心率对成像效果的影响。方法：对28例正常者,用自由呼吸导航触发3D-TFE序列行全心冠状动脉成像,用＂Soap Bubble＂软件进行冠状动脉曲面重建;以显示冠状动脉的节段数及图像质量为评价指标,分析比较不同心率对成像效果的影响。结果：28例中显示冠状动脉112支208段。不同心率冠状动脉显示节段数差异有统计学意义,当心率〈70次/min时各支冠状动脉主干近、中、远段均可良好显示。图像质量一级17例,二级5例,三级3例,四级2例,五级1例。不同心率的图像质量差异有统计学意义（P〈0.05）,当心率〈70次/min时图像质量较好。结论：自由呼吸导航全心CMRA的成像效果与心率有关,心率慢时,冠状动脉各支、段显示较完整,图像质量也较好。     

Real‐time motion and B0 corrected single voxel spectroscopy using volumetric navigators

In population groups where head pose cannot be assumed to be constant during a magnetic resonance spectroscopy examination or in difficult‐to‐shim regions of the brain, real‐time volume of interest, frequency, and shim optimization may be necessary. We investigate the effect of pose change on the B₀ homogeneity of a (2 cm)³ volume and observe typical first‐order shim changes of 1 μT/m per 1° rotation (chin down to up) in four different volumes of interest in a single volunteer. An echo planar imaging volume navigator was constructed to measure and apply in real‐time within each pulse repetition time: volume of interest positioning, frequency adjustment, and first‐order shim adjustment. This volume navigator is demonstrated in six healthy volunteers and achieved a mean linewidth of 4.4 Hz, similar to that obtained by manual shim adjustment of 4.9 Hz. Furthermore, this linewidth is maintained by the volume navigator at 4.9 Hz in the presence of pose change. By comparison, a mean linewidth of 7.5 Hz was observed, when no correction was applied. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.