Arterial spin labeling‐fast imaging with steady‐state free precession (ASL‐FISP): a rapid and quantitative perfusion technique for high‐field MRI

Arterial spin labeling (ASL) is a valuable non‐contrast perfusion MRI technique with numerous clinical applications. Many previous ASL MRI studies have utilized either echo‐planar imaging (EPI) or true fast imaging with steady‐state free precession (true FISP) readouts, which are prone to off‐resonance artifacts on high‐field MRI scanners. We have developed a rapid ASL‐FISP MRI acquisition for high‐field preclinical MRI scanners providing perfusion‐weighted images with little or no artifacts in less than 2 s. In this initial implementation, a flow‐sensitive alternating inversion recovery (FAIR) ASL preparation was combined with a rapid, centrically encoded FISP readout. Validation studies on healthy C57/BL6 mice provided consistent estimation of in vivo mouse brain perfusion at 7 and 9.4 T (249 ± 38 and 241 ± 17 mL/min/100 g, respectively). The utility of this method was further demonstrated in the detection of significant perfusion deficits in a C57/BL6 mouse model of ischemic stroke. Reasonable kidney perfusion estimates were also obtained for a healthy C57/BL6 mouse exhibiting differential perfusion in the renal cortex and medulla. Overall, the ASL‐FISP technique provides a rapid and quantitative in vivo assessment of tissue perfusion for high‐field MRI scanners with minimal image artifacts. Copyright © 2014 John Wiley & Sons, Ltd.     

右侧30°半卧位在胶囊内镜检查 中的作用研究

目的 探讨实时监视下右侧30°半卧位在胶囊内镜检查过程中的应用价值。方法 将80例行胶囊内镜检查的受检者按就诊顺序随机分为观察组和对照组，观察组40例，对照组40例。观察组取右侧30°半卧位，对照组取右侧卧位，两组患者吞入胶囊内镜后由内镜医师通过影像工作站实时监控系统判断胶囊所在位置，待胶囊通过幽门后患者可自由活动，对比分析两组受检者胶囊内镜的胃转运时间、小肠转运时间以及全小肠检查完成率的差异。结果 观察组平均胃转运时间为（54.78±28.75）min，明显短于对照组（77.70±42.04）min（U=566.500，P =0.024）；平均小肠转运时间为（254.85±103.57）min，与对照组（246.26±105.48）min比较差异无显著性（t =0.360，P =0.720）；全小肠检查完成率为75.0%（30/40），明显高于对照组的47.5%（19/40）（χ2=4.381，P =0.036）。结论 实时监视下右侧30°半卧位在胶囊内镜检查中具有较好的临床应用价值。     

Triple‐echo steady‐state T2 relaxometry of the human brain at high to ultra‐high fields

Quantitative MRI techniques, such as T₂ relaxometry, have demonstrated the potential to detect changes in the tissue microstructure of the human brain with higher specificity to the underlying pathology than in conventional morphological imaging. At high to ultra‐high field strengths, quantitative MR‐based tissue characterization benefits from the higher signal‐to‐noise ratio traded for either improved resolution or reduced scan time, but is impaired by severe static (B₀) and transmit (B₁) field heterogeneities. The objective of this study was to derive a robust relaxometry technique for fast T₂ mapping of the human brain at high to ultra‐high fields, which is highly insensitive to B₀ and B₁ field variations. The proposed method relies on a recently presented three‐dimensional (3D) triple‐echo steady‐state (TESS) imaging approach that has proven to be suitable for fast intrinsically B₁‐insensitive T₂ relaxometry of rigid targets. In this work, 3D TESS imaging is adapted for rapid high‐ to ultra‐high‐field two‐dimensional (2D) acquisitions. The achieved short scan times of 2D TESS measurements reduce motion sensitivity and make TESS‐based T₂ quantification feasible in the brain. After validation in vitro and in vivo at 3 T, T₂ maps of the human brain were obtained at 7 and 9.4 T. Excellent agreement between TESS‐based T₂ measurements and reference single‐echo spin‐echo data was found in vitro and in vivo at 3 T, and T₂ relaxometry based on TESS imaging was proven to be feasible and reliable in the human brain at 7 and 9.4 T. Although prominent B₀ and B₁ field variations occur at ultra‐high fields, the T₂ maps obtained show no B₀‐ or B₁‐related degradations. In conclusion, as a result of the observed robustness, TESS T₂ may emerge as a valuable measure for the early diagnosis and progression monitoring of brain diseases in high‐resolution 2D acquisitions at high to ultra‐high fields. Copyright © 2014 John Wiley & Sons, Ltd.     

Impact of fillers on dissolution kinetic of fenofibrate dry foams

Abstract

Dry foam technology reveals the opportunity to improve the dissolution behavior of poorly soluble drugs tending to agglomeration due to micronization. In this study, the impact of fillers on the manufacturability, the properties of dry foams and granules as well as the dissolution kinetics of dry foam tablets was investigated using fenofibrate as a model compound. Different maltodextrins and dried glucose syrups, a maltodextrin–phosphatidylcholine complex, isomalt and a 1:1 mixture of mannitol/glucose syrup were used as filler. Within the group of maltodextrins and glucose syrups, the influences of dextrose equivalent (DE), particle morphology and botanical source of starch were investigated. Comparable macroscopic foam structures were obtained with maltodextrins and glucose syrups whereas different foam morphologies were obtained for the other fillers tested. Regarding the maltodextrins and glucose syrups, different physicochemical and particle properties had a minor impact on granule characteristics and tablet dissolution. Using the maltodextrin–phosphatidylcholine complex resulted in a low specific surface area of the granules and a slow tablet dissolution caused by a slow disintegration. In contrast, a high specific surface area and a fast release were obtained with isomalt and glucose syrup/mannitol mixture indicating that high soluble low molecular weight fillers enable the development of fast dissolving dry foam tablets.     

Prehospital fast track care for patients with hip fracture: Impact on time to surgery,hospital stay,post-operative complications and mortality a randomised,controlled trial

IntroductionAmbulance organisations in Sweden have introduced prehospital fast track care (PFTC) for patients with suspected hip fracture. This means that the ambulance nurse starts the pre-operative procedure otherwise implemented at the accident & emergency ward (A&E) and transports the patient directly to the radiology department instead of A&E. If the diagnosis is confirmed, the patient is transported directly to the orthopaedic ward. No previous randomised, controlled studies have analysed PFTC to describe its possible advantages.The aim of this study is to examine whether PFTC has any impact on outcomes such as time to surgery, length of stay, post-operative complications and mortality.MethodsThe design of this study is a prehospital randomised, controlled study, powered to include 400 patients. The patients were randomised into PFTC or the traditional care pathway (A&E group).ResultsTime from arrival to start for X-ray was faster for PFTC (mean, 28 vs. 145 min; p < 0.001), but the groups did not differ with regard to time from start of X-ray to start of surgery (mean 18.40 h in both groups). No significant differences between the groups were observed with regard to: time from arrival to start of surgery (p = 0.07); proportion operated within 24 h (79% PFTC, 75% A&E; p = 0.34); length of stay (p = 0.34); post-operative complications (p = 0.75); and 4 month mortality (18% PFTC, 15% A&E p = 0.58).ConclusionPFTC improved time to X-ray and admission to a ward, as expected, but did not significantly affect time to start of surgery, length of stay, post-operative complications or mortality. These outcomes were probably affected by other factors at the hospital. Patients with either possible life-threatening conditions or life-threatening conditions prehospital were excluded.     

Can T1w/T2w ratio be used as a myelin‐specific measure in subcortical structures? Comparisons between FSE‐based T1w/T2w ratios,GRASE‐based T1w/T2w ratios and multi‐echo GRASE‐based myelin water fractions

Given the growing popularity of T₁‐weighted/T₂‐weighted (T₁w/T₂w) ratio measurements, the objective of the current study was to evaluate the concordance between T₁w/T₂w ratios obtained using conventional fast spin echo (FSE) versus combined gradient and spin echo (GRASE) sequences for T₂w image acquisition, and to compare the resulting T₁w/T₂w ratios with histologically validated myelin water fraction (MWF) measurements in several subcortical brain structures. In order to compare these measurements across a relatively wide range of myelin concentrations, whole‐brain T₁w magnetization prepared rapid acquisition gradient echo (MPRAGE), T₂w FSE and three‐dimensional multi‐echo GRASE data were acquired from 10 participants with multiple sclerosis at 3 T. Then, after high‐dimensional, non‐linear warping, region of interest (ROI) analyses were performed to compare T₁w/T₂w ratios and MWF estimates (across participants and brain regions) in 11 bilateral white matter (WM) and four bilateral subcortical grey matter (SGM) structures extracted from the JHU_MNI_SS ‘Eve’ atlas. Although the GRASE sequence systematically underestimated T₁w/T₂w values compared to the FSE sequence (revealed by Bland–Altman and mountain plots), linear regressions across participants and ROIs revealed consistently high correlations between the two methods (r² = 0.62 for all ROIs, r² = 0.62 for WM structures and r² = 0.73 for SGM structures). However, correlations between either FSE‐based or GRASE‐based T₁w/T₂w ratios and MWFs were extremely low in WM structures (FSE‐based, r² = 0.000020; GRASE‐based, r² = 0.0014), low across all ROIs (FSE‐based, r² = 0.053; GRASE‐based, r² = 0.029) and moderate in SGM structures (FSE‐based, r² = 0.20; GRASE‐based, r² = 0.17). Overall, our findings indicated a high degree of correlation (but not equivalence) between FSE‐based and GRASE‐based T₁w/T₂w ratios, and low correlations between T₁w/T₂w ratios and MWFs. This suggests that the two T₁w/T₂w ratio approaches measure similar facets of subcortical tissue microstructure, whereas T₁w/T₂w ratios and MWFs appear to be sensitized to different microstructural properties. On this basis, we conclude that multi‐echo GRASE sequences can be used in future studies to efficiently elucidate both general (T₁w/T₂w ratio) and myelin‐specific (MWF) tissue characteristics.