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Anatomical and Biological Imaging of Pediatric Brain Tumor
Published in David A. Walker, Giorgio Perilongo, Roger E. Taylor, Ian F. Pollack, Brain and Spinal Tumors of Childhood, 2020
Rob A. Dineen, Shivaram Avula, Andrew C. Peet, Giovanni Morana, Monika Warmuth-Metz
Perfusion MRI provides biomarkers of tumor vascularity such as cerebral blood flow (CBF), cerebral blood volume (CBV), and vascular permeability (ktrans). Several methods are used, each with its own properties, and each tends to be most accurate in measuring a specific biomarker. Dynamic susceptibility contrast (DSC) MRI is the most commonly used technique and is a rapid way to acquire CBV. Dynamic contrast-enhanced (DCE) MRI requires approximately 5 minutes and is particularly useful for obtaining ktrans. Both techniques require gadolinium-based contrast injection via a mechanical pump and these are commonly not compatible with a central venous catheter. Arterial spin labeling (ASL) measures CBF without contrast injection in about 5 minutes. An alternative method for acquiring information on perfusion without injecting contrast agent is multi-b value DWI, which can provide estimates of perfusion fraction (f), which has some equivalence to CBV. Some studies quote tumor blood volume (TBV) or tumor blood flow (TBF) which are equivalent to CBV and CBF respectively when the latter has been measured over the tumor. We use them interchangeably here.
Biomedical Imaging Magnetic Resonance Imaging
Published in Lawrence S. Chan, William C. Tang, Engineering-Medicine, 2019
In a technique that relies on an endogenous tracer, the magnetization of arterial blood spins is labeled by an inversion RF pulse, causing a signal reduction when the labeled blood enters the imaging location. This method is known as arterial spin labeling (ASL) which can produce quantitative or semi-quantitative maps of cerebral blood flow and other parameters (Alsop et al. 2015). ASL can be implemented in a number of ways depending on the type of the labeling pulse, the imaging sequence employed, the strategies to compensate for magnetization transfer effects, and other factors. Despite the variations, a consensus has been developed for consistent use of ASL techniques (Alsop et al. 2015).
Neuroimaging
Published in John W. Scadding, Nicholas A. Losseff, Clinical Neurology, 2011
Gradient echo or susceptibility weighted imaging depend on local field inhomogeneities from paramagnetic substances, such as iron or gadolinium contrast media, and the signal loss they cause. These sequences show blood products not readily visible on other sequences and are particularly important in acute stroke imaging. Susceptibility effects induced by an infused bolus of gadolinium contrast medium form the basis of perfusion weighted imaging. Arterial spin labelling is a perfusion imaging technique that does not require injected contrast medium. Moving protons in arterial blood are ‘labelled’ and a territorial map of brain perfusion can be made by labelling individual arteries.
Advances in imaging techniques to assess kidney fibrosis
Published in Renal Failure, 2023
Buchun Jiang, Fei Liu, Haidong Fu, Jianhua Mao
Arterial spin labeling (ASL) MRI uses the endogenous water of arterial blood as an endogenous tracer to detect tissue perfusion. Because of the affluent blood supply of the renal cortex, the cortical ASL perfusion or renal blood flow is the main indicator of this technique. Earlier studies found that ASL perfusion could reflect and quantify the perfusion in native and transplanted kidneys [103,104]. An animal experiment of ASL-MRI in rats after renal transplantation showed that the mean cortical perfusion was higher in rats with chronic rejections than in those with acute rejections, and the cortical renal blood flow was positively correlated with renal creatinine clearance [28]. Subsequently, several studies confirmed that ASL perfusion had a significantly positive correlation with eGFR in CKD, including diabetic nephropathy [105–107], and in transplanted kidneys [108].
Psychiatric onset of prodromal dementia with Lewy bodies: Current insights into neuroimaging tools
Published in The World Journal of Biological Psychiatry, 2023
Niels Hansen, Sebastian Johannes Müller, Eya Khadhraoui, Marielle Ernst, Christian Heiner Riedel, Jens Wiltfang, Claudia Lange, Carolin Bouter
There are several limitations in this review article worth mentioning. First, this is a narrative, not a systematic review, so the selection of articles for this review is subjective. Second, the number of articles on employing neuroimaging methods in a pro-DLB subgroup is very low, as this subgroup has also only recently published research criteria (McKeith et al. 2020). There are few papers on alternative methods, but the value of each is compromised by such low patient numbers. Thus, caution is needed in interpreting our data. In addition, certain methods are mentioned, i.e. functional MRI or DTI, although there is no conclusive data on any pro-DLB subgroup with a psychiatric symptom onset (nevertheless, the early DLB data suggests that this method may be promising). There is also the arterial spin labelling MRI method, but as the evidence level of is still too low (only one reported case), more data is needed before drawing conclusions on its use. Thus, the majority of the methodologies we describe are promising, but more research is required involving with higher case numbers to be clinically applicable.
Erythritol and xylitol differentially impact brain networks involved in appetite regulation in healthy volunteers
Published in Nutritional Neuroscience, 2022
Anne Christin Meyer-Gerspach, Jed O. Wingrove, Christoph Beglinger, Jens F. Rehfeld, Carel W. Le Roux, Ralph Peterli, Patrick Dupont, Owen O’Daly, Lukas Van Oudenhove, Bettina K. Wölnerhanssen
Twenty-three volunteers were recruited, but two did not meet the eligibility criteria, and one did not tolerate the nasogastric tube. This person’s data was excluded from analysis and replaced by a new participant, giving a final total of 20 participants. For details, see the participant flow diagram (Figure 2). Administration of fifty grams of xylitol led to bloating and diarrhea in 40% of all subjects (8 out of 20), and 75 g of erythritol had the same side effects in 16.6% of all subjects (3 out of 20; xylitol vs. erythritol p = 0.16). Despite diarrhea (which usually stopped after 1–2 bowel movements), no study session had to be terminated prematurely. Data from 20 volunteers were obtained for analysis. For BOLD analysis, one scan for one subject had to be excluded because of excessive head motion (according to the criteria reported in supplement), and two scans of two subjects because of raw data quality problems. For arterial spin labeling (ASL) analysis, we had to exclude two additional subjects because of data quality problems.