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- Arvidsson, Jonathan, et al.
(författare)
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Effects of bolus injection duration on perfusion estimates in dynamic CT and dynamic susceptibility contrast MRI
- 2023
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Ingår i: Magnetic Resonance Materials in Physics, Biology and Medicine. - : Springer Science and Business Media LLC. - 0968-5243 .- 1352-8661. ; 36:1, s. 95-106
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Tidskriftsartikel (refereegranskat)abstract
- Estimates of cerebral blood flow (CBF) and tissue mean transit time (MTT) have been shown to differ between dynamic CT perfusion (CTP) and dynamic susceptibility contrast MRI (DSC-MRI). This study investigates whether these discrepancies regarding CBF and MTT between CTP and DSC-MRI can be attributed to the different injection durations of these techniques. Five subjects were scanned using CTP and DSC-MRI. Region-wise estimates of CBF, MTT, and cerebral blood volume (CBV) were derived based on oscillatory index regularized singular value decomposition. A parametric model that reproduced the shape of measured time curves and characteristics of resulting perfusion parameter estimates was developed and used to simulate data with injection durations typical for CTP and DSC-MRI for a clinically relevant set of perfusion scenarios and noise levels. In simulations, estimates of CBF/MTT showed larger negative/positive bias and increasing variability for CTP when compared to DSC-MRI, especially for high CBF levels. While noise also affected estimates, at clinically relevant levels, the injection duration effect was larger. There are several methodological differences between CTP and DSC-MRI. The results of this study suggest that the injection duration is among those that can explain differences in estimates of CBF and MTT between these bolus tracking techniques.
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- Bane, Octavia, et al.
(författare)
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Consensus-based technical recommendations for clinical translation of renal BOLD MRI
- 2020
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Ingår i: Magnetic Resonance Materials in Physics, Biology and Medicine. - : Springer. - 0968-5243 .- 1352-8661. ; 33:1, s. 199-215
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Forskningsöversikt (refereegranskat)abstract
- Harmonization of acquisition and analysis protocols is an important step in the validation of BOLD MRI as a renal biomarker. This harmonization initiative provides technical recommendations based on a consensus report with the aim to move towards standardized protocols that facilitate clinical translation and comparison of data across sites. We used a recently published systematic review paper, which included a detailed summary of renal BOLD MRI technical parameters and areas of investigation in its supplementary material, as the starting point in developing the survey questionnaires for seeking consensus. Survey data were collected via the Delphi consensus process from 24 researchers on renal BOLD MRI exam preparation, data acquisition, data analysis, and interpretation. Consensus was defined as >= 75% unanimity in response. Among 31 survey questions, 14 achieved consensus resolution, 12 showed clear respondent preference (65-74% agreement), and 5 showed equal (50/50%) split in opinion among respondents. Recommendations for subject preparation, data acquisition, processing and reporting are given based on the survey results and review of the literature. These technical recommendations are aimed towards increased inter-site harmonization, a first step towards standardization of renal BOLD MRI protocols across sites. We expect this to be an iterative process updated dynamically based on progress in the field.
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- Bibic, Adnan, et al.
(författare)
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Denoising of arterial spin labeling data: wavelet-domain filtering compared with Gaussian smoothing.
- 2010
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Ingår i: Magma. - : Springer Science and Business Media LLC. - 1352-8661. ; 23:3, s. 125-137
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To investigate a wavelet-based filtering scheme for denoising of arterial spin labeling (ASL) data, potentially enabling reduction of the required number of averages and the acquisition time. METHODS: ASL magnetic resonance imaging (MRI) provides quantitative perfusion maps by using arterial water as an endogenous tracer. The signal difference between a labeled image, where inflowing arterial spins are inverted, and a control image is proportional to blood perfusion. ASL perfusion maps suffer from low SNR, and the experiment must be repeated a number of times (typically more than 40) to achieve adequate image quality. In this study, systematic errors introduced by the proposed wavelet-domain filtering approach were investigated in simulated and experimental image datasets and compared with conventional Gaussian smoothing. RESULTS: Application of the proposed method enabled a reduction of the number of averages and the acquisition time by at least 50% with retained standard deviation, but with effects on absolute CBF values close to borders and edges. CONCLUSIONS: When the ASL perfusion maps showed moderate-to-high SNRs, wavelet-domain filtering was superior to Gaussian smoothing in the vicinity of borders between gray and white matter, while Gaussian smoothing was a better choice for larger homogeneous areas, irrespective of SNR.
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- Bjørnerud, A., et al.
(författare)
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Pre-clinical results with Clariscan (NC100150 Injection) : experience from different disease models
- 2001
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Ingår i: Magnetic Resonance Materials in Physics, Biology and Medicine. - 0968-5243 .- 1352-8661. ; 12:2-3, s. 99-103
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A superparamagnetic nanoparticle (NC100150 Injection) was investigated in two different animal models; renal perfusion in pigs and tumour imaging in mice. In the pig model, qualitative first-pass perfusion maps following a bolus injection of NC100150 Injection enabled good visualisation of hypoperfused regions of the renal cortex following partial ligation of the renal artery. High temporal resolution was found to be essential to accurately capture the first passage of the contrast agent through the kidney due to the very rapid blood flow in normal renal cortex. In the tumour model (LS174T cells implanted in nude mice), NC100150 Injection was found to cause a gradual (over 60 min) signal increase on T1-w images in part of the tumours which was attributed to contrast agent leakage from the vascular space to the extravascular space in areas of increased capillary permeability. This observation is consistent with previous reports on the molecular cut-off size for vascular extraction for this tumour cell line. The specific enhancement of tumour tissue suggest potential utility of NC100150 Injection as an angiogenesis marker.
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- Carlsson, Åsa, 1978, et al.
(författare)
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Degraded water suppression in small volume ¹H MRS due to localised shimming.
- 2011
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Ingår i: Magma (New York, N.Y.). - : Springer Science and Business Media LLC. - 0968-5243. ; 24:2, s. 97-107
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Tidskriftsartikel (refereegranskat)abstract
- High quality, artifact free, ¹H MRS require a homogeneous magnetic field over the volume of interest (VOI) and an effective global water suppression (WS). However, the shim coils act globally and, hence, affect the resonance frequency over the entire object, making the frequency selective WS spatially selective. Unsuppressed water signal may cause spurious echo artifacts. Aim: Study and visualise the effect localised shimming has on WS.
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