Simultaneous proton resonance frequency T1 - MR shear wave elastography for MR-guided focused ultrasound multiparametric treatment monitoring.

PURPOSE: To develop an efficient MRI pulse sequence to simultaneously measure multiple parameters that have been shown to correlate with tissue nonviability following thermal therapies. METHODS: A 3D segmented EPI pulse sequence was used to simultaneously measure proton resonance frequency shift (PRFS) MR thermometry (MRT), T1 relaxation time, and shear wave velocity induced by focused ultrasound (FUS) push pulses. Experiments were performed in tissue mimicking gelatin phantoms and ex vivo bovine liver. Using a carefully designed FUS triggering scheme, a heating duty cycle of approximately 65% was achieved by interleaving FUS ablation pulses with FUS push pulses to induce shear waves in the tissue. RESULTS: In phantom studies, temperature increases measured with PRFS MRT and increases in T1 correlated with decreased shear wave velocity, consistent with material softening with increasing temperature. During ablation in ex vivo liver, temperature increase measured with PRFS MRT initially correlated with increasing T1 and decreasing shear wave velocity, and after tissue coagulation with decreasing T1 and increasing shear wave velocity. This is consistent with a previously described hysteresis in T1 versus PRFS curves and increased tissue stiffness with tissue coagulation. CONCLUSION: An efficient approach for simultaneous and dynamic measurements of PRSF, T1 , and shear wave velocity during treatment is presented. This approach holds promise for providing co-registered dynamic measures of multiple parameters, which correlates to tissue nonviability during and following thermal therapies, such as FUS.

Consensus on an implicit bias and health disparities curriculum in neonatal medicine: a Delphi study.

OBJECTIVE: Despite longstanding and recurrent calls for effective implicit bias (IB) education in health professions education as one mechanism to reduce ongoing racism and health disparities, such curricula for neonatal-perinatal medicine (NPM) are limited. We aim to determine the key curricular elements for educating NPM fellows, advanced practice providers, and attending physicians in the critical topics of IB and health disparities. STUDY DESIGN: A modified Delphi study was performed with content experts in IB and health disparities who had educational relationships to those working and training in the neonatal intensive care unit. RESULT: Three Delphi rounds were conducted from May to November 2021. Experts reached consensus on a variety of items for inclusion in the curriculum, including educational goals, learning objectives, teaching strategies, and educator principles. CONCLUSION: Essential curricular components of an IB and health disparities curriculum for neonatal medicine were defined using rigorous consensus building methodology.

Histology to 3D in vivo MR registration for volumetric evaluation of MRgFUS treatment assessment biomarkers.

Advances in imaging and early cancer detection have increased interest in magnetic resonance (MR) guided focused ultrasound (MRgFUS) technologies for cancer treatment. MRgFUS ablation treatments could reduce surgical risks, preserve organ tissue and function, and improve patient quality of life. However, surgical resection and histological analysis remain the gold standard to assess cancer treatment response. For non-invasive ablation therapies such as MRgFUS, the treatment response must be determined through MR imaging biomarkers. However, current MR biomarkers are inconclusive and have not been rigorously evaluated against histology via accurate registration. Existing registration methods rely on anatomical features to directly register in vivo MR and histology. For MRgFUS applications in anatomies such as liver, kidney, or breast, anatomical features that are not caused by the treatment are often insufficient to drive direct registration. We present a novel MR to histology registration workflow that utilizes intermediate imaging and does not rely on anatomical MR features being visible in histology. The presented workflow yields an overall registration accuracy of 1.00 ± 0.13 mm. The developed registration pipeline is used to evaluate a common MRgFUS treatment assessment biomarker against histology. Evaluating MR biomarkers against histology using this registration pipeline will facilitate validating novel MRgFUS biomarkers to improve treatment assessment without surgical intervention. While the presented registration technique has been evaluated in a MRgFUS ablation treatment model, this technique could be potentially applied in any tissue to evaluate a variety of therapeutic options.

Technical Note: Quantification of blood-spinal cord barrier permeability after application of magnetic resonance-guided focused ultrasound in spinal cord injury.

PURPOSE: To demonstrate that magnetic resonance-guided focused ultrasound (MRgFUS) facilitates blood-spinal cord barrier (BSCB) permeability and develop observer-independent MRI quantification of BSCB permeability after MRgFUS for spinal cord injury (SCI). METHODS: Noninjured Sprague-Dawley rats (n = 3) underwent MRgFUS and were administered Evans blue post-MRgFUS to confirm BSCB opening. Absorbance was measured by spectrophotometry and correlated with its corresponding image intensity. Rats (n = 21) underwent T8-T10 laminectomy and extradural compression of the spinal cord (23g weighted aneurysm-type clip, 1 min). The intervention group (n = 11) was placed on a preclinical MRgFUS system, administered microbubbles (Optison, 0.2 mL/kg), and received 3 MRgFUS sonications (25 ms bursts, 1 Hz pulses for 3 min, 3 acoustic W, approximately 1.0-2.1 MPa peak pressure as measured via hydrophone). The sham group (n = 10) received equivalent procedures with no sonications. T1w MRI was obtained both pre- and post-MRgFUS BSCB opening. Spinal cords were segmented manually or semiautomatically and a Pearson correlation with P ≤ 0.001 was used to correlate the two segmentation methods. MRgFUS sonication and control regions intensity values were evaluated with a paired t-test with a P ≤ 0.01. RESULTS: Semiautomatic segmentation reduced computational time by 95% and was correlated with manual segmentation (Pearson = 0.92, P < 0.001, n = 71 regions). In the noninjured rat group, Evans blue absorbance correlated with image intensity in the MRgFUS and control regions (Pearson = 0.82, P = 0.02, n = 6). In rats that underwent the SCI procedure, an increase in signal intensity in the MRgFUS targeted region relative to control was seen in all SCI rats (10.65 ± 12.4%, range: 0.96-43.9%, n = 11, P = 0.002). SCI sham MRgFUS revealed no change (0.63 ± 0.52%, 95% CI 0.320.95, n = 10). This result was significant between both groups (P = 0.003). CONCLUSION: The implemented semiautomatic segmentation procedure improved data analysis efficiency. Quantitative methods using contrast-enhanced MRI with histological validation are sensitive for detection of blood-spinal cord barrier opening induced by magnetic resonance-guided focused ultrasound.

Isolated kidney phantom for development of biothermal vascular models with application to high intensity focused ultrasound therapy.

A methodology using magnetic resonance angiography (MRA) is presented for identifying thermally significant blood vessels in isolated kidneys, specifically for use in biothermal model development with application to high intensity focused ultrasound (HIFU). A combination of a proven preservation technique, newly developed MR-compatible experimental procedures and the refinement of MR pulse sequence parameters was used to determine vascular characteristics using high-resolution three-dimensional time-of-flight MRA image of flow through isolated kidneys. Results presented are twofold. First, improved vessel visibility was attained through decreasing the magnetic resonance imaging bandwidth from 150 to 30 Hz/pixel while simultaneously increasing the echo time, repetition time, and flip angle; vascular center line extraction showed an 18% improvement in the number of vessel segments detected and a 23% increase in length of the terminal segments over a base line technique without improvements. Second, the overall system was shown to be practical to determine vascular flow effects during HIFU heating; testing results from heating the kidney with HIFU are presented, showing a decrease of average kidney temperature with an increase of flow rate through the kidney with localized cooling demonstrated surrounding known vessel locations.

Magnetic resonance imaging-guided focused ultrasound to increase localized blood-spinal cord barrier permeability.

Spinal cord injury (SCI) affects thousands of people every year in the USA, and most patients are left with some permanent paralysis. Therapeutic options are limited and only modestly affect outcome. To address this issue, we used magnetic resonance imaging-guided focused ultrasound (MRgFUS) as a non-invasive approach to increase permeability in the blood-spinal cord barrier (BSCB). We hypothesize that localized, controlled sonoporation of the BSCB by MRgFUS will aid delivery of therapeutics to the injury. Here, we report our preliminary findings for the ability of MRgFUS to increase BSCB permeability in the thoracic spinal cord of a normal rat model. First, an excised portion of normal rat spinal column was used to characterize the acoustic field and to estimate the insertion losses that could be expected in an MRgFUS blood spinal cord barrier opening. Then, in normal rats, MRgFUS was applied in combination with intravenously administered microbubbles to the spinal cord region. Permeability of the BSCB was indicated as signal enhancement by contrast administered prior to T1-weighted magnetic resonance imaging and verified by Evans blue dye. Neurological testing using the Basso, Beattie, and Breshnahan scale and the ladder walk was normal in 8 of 10 rats tested. Two rats showed minor impairment indicating need for further refinement of parameters. No gross tissue damage was evident by histology. In this study, we have opened successfully the blood spinal cord barrier in the thoracic region of the normal rat spine using magnetic resonance-guided focused ultrasound combined with microbubbles.

Behavioral Problems and Socioemotional Competence at 18 to 22 Months of Extremely Premature Children.

BACKGROUND: Behavior and socioemotional development are crucial aspects of child development . METHODS: A total of 2505 children born at <27 weeks' gestation was evaluated at 18 to 22 months' corrected age between January 1, 2008 and December 12, 2012 (86% follow-up). The Brief Infant and Toddler Social and Emotional Assessment was used to evaluate behavioral and socioemotional problems. Cognition and language were evaluated by using the Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III). Logistic regression analysis was used to evaluate for perinatal and demographic factors associated with behavioral problems (≥75th percentile) and delayed socioemotional competence (≤15th percentile). Structural equation modeling with bootstrapping was used to identify possible associated risk factors and Bayley-III scores as mediators. RESULTS: Thirty-five percent (873) of children had behavioral problems, and 26% (637) displayed deficits in socioemotional competence. Male sex, public insurance, mothers with less than a high school education, and lower maternal age were associated with behavioral problems. Deficits in competence were associated with lower birth weight, public insurance, mothers with less than a high school education, and abnormal neuromotor exam. Bayley-III language and cognitive scores were significant mediators of the relationships between risk factors and both behavioral and competence scores (P < .05). CONCLUSIONS: Extremely premature children are at risk for behavioral problems and deficits in socioemotional competence. Sociodemographic factors were associated with both socioemotional competence and behavioral problems. Deficits in socioemotional competence were also associated with neuromotor abnormalities and cognitive and language function.

The problems of moderate preterm infants.

Moderate preterm infants are the largest group of preterm infants but are an understudied population. Care practices are adapted from studies of full term infants or extremely preterm infants. Studies are needed to tailor treatments for this vulnerable population. The NRN began investigation in this population with a registry of characteristics, and neonatal outcomes of these infants. This work compares outcomes of MPR with those of full term infants reported in the literature.

Neurodevelopmental outcomes of extremely low-gestational-age neonates with low-grade periventricular-intraventricular hemorrhage.

IMPORTANCE: Low-grade periventricular-intraventricular hemorrhage is a common neurologic morbidity among extremely low-gestational-age neonates, yet the outcomes associated with this morbidity are not fully understood. In a contemporary multicenter cohort, we evaluated the impact of such hemorrhages on early (18-22 month) neurodevelopmental outcomes of extremely premature infants. OBJECTIVE: To compare neurodevelopmental outcomes at 18 to 22 months' corrected age for extremely low-gestational-age infants with low-grade (grade 1 or 2) periventricular-intraventricular hemorrhage with those of infants with either no hemorrhage or severe (grade 3 or 4) hemorrhage demonstrated on cranial ultrasonography. DESIGN: Longitudinal observational study. SETTING: Sixteen centers of the Eunice Kennedy Shriver National Institute of Child Health and Human Development Neonatal Research Network. PARTICIPANTS: A total of 1472 infants born at less than 27 weeks' gestational age between January 1, 2006, and December 31, 2008, with ultrasonography results within the first 28 days of life and surviving to 18 to 22 months with complete follow-up assessments were eligible. MAIN EXPOSURE: Low-grade periventricular-intraventricular hemorrhage. MAIN OUTCOME MEASURES: Outcomes included cerebral palsy; gross motor functional limitation; cognitive and language scores according to the Bayley Scales of Infant Development, 3rd Edition; and composite measures of neurodevelopmental impairment. Regression modeling evaluated the association of hemorrhage severity with adverse outcomes while controlling for potentially confounding variables and center differences. RESULTS: Low-grade hemorrhage was not associated with significant differences in unadjusted or adjusted risk of any adverse neurodevelopmental outcome compared with infants without hemorrhage. Compared with low-grade hemorrhage, severe hemorrhage was associated with decreased adjusted continuous cognitive (ß, -3.91 [95% CI, -6.41 to -1.42]) and language (ß, -3.19 [-6.19 to -0.19]) scores as well as increased odds of each adjusted categorical outcome except severe cognitive impairment (odds ratio [OR], 1.46 [0.74 to 2.88]) and mild language impairment (OR, 1.35 [0.88 to 2.06]). CONCLUSIONS AND RELEVANCE: At 18 to 22 months, the neurodevelopmental outcomes of extremely low-gestational-age infants with low-grade periventricular-intraventricular hemorrhage are not significantly different from those without hemorrhage. Additional study at school age and beyond would be informative.