Optimization of quantitative susceptibility mapping for regional estimation of oxygen extraction fraction in the brain.

PURPOSE: We sought to determine the degree to which oxygen extraction fraction (OEF) estimated using quantitative susceptibility mapping (QSM) depends on two critical acquisition parameters that have a significant impact on acquisition time: voxel size and final echo time. METHODS: Four healthy volunteers were imaged using a range of isotropic voxel sizes and final echo times. The 0.7 mm data were downsampled at different stages of QSM processing by a factor of 2 (to 1.4 mm), 3 (2.1 mm), or 4 (2.8 mm) to determine the impact of voxel size on each analysis step. OEF was estimated from 11 veins of varying diameter. Inter- and intra-session repeatability were estimated for the optimal protocol by repeat scanning in 10 participants. RESULTS: Final echo time was found to have no significant effect on OEF. The effect of voxel size was significant, with larger voxel sizes underestimating OEF, depending on the proximity of the vein to the superficial surface of the brain and on vein diameter. The last analysis step of estimating vein OEF values from susceptibility images had the largest dependency on voxel size. Inter-session coefficients of variation on OEF estimates of between 5.2% and 8.7% are reported, depending on the vein. CONCLUSION: QSM acquisition times can be minimized by reducing the final echo time but an isotropic voxel size no larger than 1 mm is needed to accurately estimate OEF in most medium/large veins in the brain. Such acquisitions can be achieved in under 4 min.

Evaluation of patient preparedness for surgery: a randomized controlled trial.

BACKGROUND: Patient preparedness for pelvic reconstructive surgery has important implications for patient satisfaction and the perception of improvement after surgery. The ideal method in which to optimally prepare patients for surgery has not been determined. OBJECTIVE: The objective of the study was to evaluate the impact of a preoperative patient education video on patient preparedness prior to sacrocolpopexy as measured by a preoperative preparedness questionnaire. STUDY DESIGN: We performed a single-blind, randomized, stratified clinical trial at a single academic center evaluating the use of a preoperative patient education video as an adjunct to preoperative counseling on patient preparedness. Eligible patients presenting for their preoperative appointment prior to undergoing pelvic reconstructive surgery were randomized to watch a preoperative video vs usual care. Preoperative questionnaires assessing patient preparedness, understanding, perception of time, and actual time spent with a health care team were administered at the end of this visit. The primary outcome was patient preparedness for pelvic reconstructive surgery as measured by a preoperative preparedness questionnaire. Secondary outcomes included actual time spent during the physician-patient encounter, perception of time spent with the health care team, and identification of patient factors associated with patient preparedness. RESULTS: Of the total 100 recruited patients, 52 were randomized to the video group and 48 to the usual-care group. The use of the video did not increase overall patient preparedness (71.1% with video vs 68.8% usual care, P = .79) prior to surgery. The use of the video did not decrease the amount of time spent during the physician-patient encounter (16.9 ± 5.6 min vs 17.1 ± 5.4 min, P = .87). There was a significant association between patient preparedness and perception that the health care team spent sufficient time with the patient (89.5% vs 10.5%; P < .001), but no association was observed between preparedness and actual time spent (17.4 ± 5.4 min vs16.5 ± 5.5 min, P = .47). Those with a history of a previous surgery (82.1% vs 33.3%, P = .002) and those with more significant apical prolapse (0.6 ± 4.6 vs -1.6 ± 3.9, P = .05) were more likely to report feeling prepared for surgery. CONCLUSION: The majority of patients undergoing pelvic surgery at our institution felt prepared prior to undergoing surgery. The use of preoperative education video did not increase overall patient preparedness for surgery. Greater preparedness was associated with patient perception of how much time the health care team spent with the patient but not actual time spent.

Characterisation of microvessel blood velocity and segment length in the brain using multi-diffusion-time diffusion-weighted MRI.

Multi-diffusion-time diffusion-weighted MRI can probe tissue microstructure, but the method has not been widely applied to the microvasculature. At long diffusion-times, blood flow in capillaries is in the diffusive regime, and signal attenuation is dependent on blood velocity (v) and capillary segment length (l). It is described by the pseudo-diffusion coefficient (D*=vl/6) of intravoxel incoherent motion (IVIM). At shorter diffusion-times, blood flow is in the ballistic regime, and signal attenuation depends on v, and not l. In theory, l could be estimated using D* and v. In this study, we compare the accuracy and repeatability of three approaches to estimating v, and therefore l: the IVIM ballistic model, the velocity autocorrelation model, and the ballistic approximation to the velocity autocorrelation model. Twenty-nine rat datasets from two strains were acquired at 7 T, with b-values between 0 and 1000 smm-2 and diffusion times between 11.6 and 50 ms. Five rats were scanned twice to assess scan-rescan repeatability. Measurements of l were validated using corrosion casting and micro-CT imaging. The ballistic approximation of the velocity autocorrelation model had lowest bias relative to corrosion cast estimates of l, and had highest repeatability.

Barriers to malaria prevention in US-based travellers visiting friends and relatives abroad: a qualitative study of West African immigrant travellers†.

BACKGROUND: Over half of malaria cases reported in the USA occur among people travelling to visit friends and relatives (VFRs), predominantly to West Africa. Few studies have queried VFR travellers directly on barriers to seeking pre-travel care. We aim to describe the knowledge, attitudes and practices of VFRs travelling to malaria-endemic countries from the USA. With these findings, we aim to design interventions to encourage preventive behaviours before and during travel. METHODS: Sixteen focus groups were held in two US metropolitan areas with West African immigrant populations: Minneapolis-St. Paul, MN, and New York City, NY. A total of 172 people from 13 African countries participated. Focus group discussions were audio-recorded and transcribed, and modified grounded theory analysis was performed. Participants reviewed themes to verify intent of statements. RESULTS: Participants described the high cost of provider visits and chemoprophylaxis, challenges in advocating for themselves in healthcare settings and concerns about offending or inconveniencing hosts as barriers to malaria prevention. Cultural barriers to accessing pre-travel care included competing priorities when trip planning, such as purchasing gifts for family, travel logistics and safety concerns. When participants sought pre-travel care, most consulted their primary care provider. Participants expressed low confidence in US providers' knowledge and training about malaria and other tropical diseases. CONCLUSION: Barriers to pre-travel care for VFR travellers are multifaceted and extend beyond their perception of disease risk. Only some barriers previously reported in anecdotal and qualitative literature were supported in our findings. Future interventions should be aimed at barriers identified by individual communities and involve primary and travel specialist healthcare providers. Additional work is needed to address systems-level barriers to accessing care and establishing community-based programs to support West African VFR traveller health.