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Cerebrovascular reactivity (CVR) reflects the capacity of the brain to meet changing physiological demands and can predict the risk of cerebrovascular diseases. CVR can be obtained by measuring the change in cerebral blood flow (CBF) during a brain stress test where CBF is altered by a vasodilator such as acetazolamide. Although the gold standard to quantify CBF is PET imaging, the procedure is invasive and inaccessible to most patients. Arterial spin labeling (ASL) is a non-invasive and quantitative MRI method to measure CBF, and a consensus guideline has been published for the clinical application of ASL. Despite single post labeling delay (PLD) pseudo-continuous ASL (PCASL) being the recommended ASL technique for CBF quantification, it is sensitive to variations to the arterial transit time (ATT) and labeling efficiency induced by the vasodilator in CVR studies. Multi-PLD ASL controls for the changes in ATT, and velocity selective ASL is in theory insensitive to both ATT and labeling efficiency. Here we investigate CVR using simultaneous 15O-water PET and ASL MRI data from 19 healthy subjects. CVR and CBF measured by the ASL techniques were compared using PET as the reference technique. The impacts of blood T1 and labeling efficiency on ASL were assessed using individual measurements of hematocrit and flow velocity data of the carotid and vertebral arteries measured using phase-contrast MRI. Atezolizumab We found that multi-PLD PCASL is the ASL technique most consistent with PET for CVR quantification (group mean CVR of the whole brain = 42±19% and 40±18% respectively). Single-PLD ASL underestimated the CVR of the whole brain significantly by 15±10% compared with PET (p less then 0.01, paired t-test). Changes in ATT pre- and post-acetazolamide was the principal factor affecting ASL-based CVR quantification. Variations in labeling efficiency and blood T1 had negligible effects.Functional positron emission tomography (fPET) imaging using continuous infusion of [18F]-fluorodeoxyglucose (FDG) is a novel neuroimaging technique to track dynamic glucose utilization in the brain. In comparison to conventional static or dynamic bolus PET, fPET maintains a sustained supply of glucose in the blood plasma which improves sensitivity to measure dynamic glucose changes in the brain, and enables mapping of dynamic brain activity in task-based and resting-state fPET studies. However, there is a trade-off between temporal resolution and spatial noise due to the low concentration of FDG and the limited sensitivity of multi-ring PET scanners. Images from fPET studies suffer from partial volume errors and residual scatter noise that may cause the cerebral metabolic functional maps to be biased. Gaussian smoothing filters used to denoise the fPET images are suboptimal, as they introduce additional partial volume errors. In this work, a post-processing framework based on a magnetic resonance (MR) Bowsher-like prior was used to improve the spatial and temporal signal to noise characteristics of the fPET images. The performance of the MR guided method was compared with conventional denosing methods using both simulated and in vivo task fPET datasets. The results demonstrate that the MR-guided fPET framework denoises the fPET images and improves the partial volume correction, consequently enhancing the sensitivity to identify brain activation, and improving the anatomical accuracy for mapping changes of brain metabolism in response to a visual stimulation task. The framework extends the use of functional PET to investigate the dynamics of brain metabolic responses for faster presentation of brain activation tasks, and for applications in low dose PET imaging.
Traditional half-day per week continuity clinic experiences can lead to fragmented education in both the inpatient and outpatient arenas. Five pediatric residency programs were granted the ability from the ACGME to create X+Y scheduling where residents have continuity clinic in "blocks" rather than half-day per week experiences. The aim of this study is to assess the impact X+Y scheduling has on pediatric resident and faculty perceptions of patient care and other educational experiences.
Electronic surveys were sent to residents and faculty of the participating programs both prior to and 12 months after implementing X+Y scheduling. Survey questions measured resident and faculty perception of continuity clinic schedule satisfaction and the impact of continuity clinic schedules on inpatient and subspecialty rotation experiences using a 5-point Likert Scale. Data were analyzed using z-tests for proportion differences for those answering Agree or Strongly Agree between baseline and post-implementation respondents.
126 out of 186 residents (68%) responded pre-implementation and 120 out of 259 residents (47%) responded post-implementation. 384 faculty members were sent the survey with 51% response pre-implementation and 26% response at 12 months. Statistically significant (p<0.05) improvements were noted in resident and faculty perceptions of ability to have continuity with patients and inpatient workflow affected by clinic scheduling.
From both resident and faculty perspectives, X+Y scheduling may improve several aspects of patient care and education. X+Y scheduling could be considered as a potential option by pediatric residency programs, especially if validated with more objective data.
From both resident and faculty perspectives, X+Y scheduling may improve several aspects of patient care and education. X+Y scheduling could be considered as a potential option by pediatric residency programs, especially if validated with more objective data.Although DNA 5-hydroxymethylcytosine (5hmC) is recognized as an important epigenetic mark in cancer; its precise role in lymph node metastasis remains elusive. In this study, we investigated how 5hmC associates with lymph node metastasis in breast cancer. Accompanying with high expression of TET1 and TET2 proteins, large numbers of genes in the metastasis-positive primary tumors (MT) exhibit higher 5hmC levels than those in the non-metastatic primary tumors (PT). In contrast, the TETs protein expression and DNA 5hmC decrease significantly within the metastatic lesions in the lymph nodes (MLN) compared to those in their matched primary tumors. Through genome-wide analysis of 8 sets of primary tumors, we identified 100 high-confidence metastasis-associated 5hmC signatures, and it is found that increased levels of DNA 5hmC and gene expression of MAP7D1 associate with high risk of lymph node metastasis. Furthermore, we demonstrate that MAP7D1, regulated by TET1, promotes tumor growth and metastasis. In conclusion, the dynamic 5hmC profiles during lymph node metastasis suggest a link between DNA 5hmC and lymph node metastasis.
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