Parametric mapping of scaled fitting error in dynamic susceptibility contrast enhanced MR perfusion imaging.

Li, K L; Zhu, Xiaoping; Jackson, Alan

doi:10.1259/bjr.73.869.10884742

Cited by 17 publications

(14 citation statements)

References 25 publications

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“…Also depicted in Fig. 3 is a map of the corresponding residual fitting errors (SFE) (22), as well as the time course of the averaged ASL data in cortical gray matter. Fits of the experimental data based on the FPSCS model (solid line) or the FPOCK model (dashed line) are also shown for comparison.…”

Section: Resultsmentioning

confidence: 99%

Four‐phase single‐capillary stepwise model for kinetics in arterial spin labeling MRI

Zhu

Hylton

et al. 2005

Magnetic Resonance in Med

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An extended model for extracting measures of brain perfusion from pulsed arterial spin labeling (ASL) data while considering transit effects and restricted permeability of capillaries to blood water is proposed. We divided the time course of the signal difference between control and labeled images into four phases with respect to the arrival time of labeled blood water at the voxel of interest (t A ), transit time through the arteries in the voxel (t ex ), and duration of the bolus of labeled spins (). Dividing the labeled slab of blood water into many discrete segments, and adapting numerical integration methods allowed us to conveniently model restricted capillary-tissue exchange based on a modified distributed parameter model. We compared this four-phase single-capillary stepwise (FPSCS) model with models that treat water as a freely diffusible tracer, using both simulations and experimental ASL brain imaging data at 1.5T from eight healthy subjects ( Arterial spin labeling (ASL) MRI, which uses endogenous arterial water as a tracer for blood flow, is entirely noninvasive and is increasingly being used to study brain perfusion and function (1,2). Quantification of tissue perfusion with ASL MRI is generally accomplished by modeling the signal evolution of ASL based on pharmacokinetic information, such as the exchange of blood water between capillaries and brain tissue, and the Bloch-Terry equations, which describe spin magnetization in the presence of relaxation and flow (3-15). However, early applications of ASL (3-6) relied on single-compartment kinetics for quantification, which limited accuracy for several reasons. First, it was assumed that labeled water delivered to the brain would instantaneously enter the capillary bed for exchange. Second, permeability of the capillaries was assumed to be infinitely high for water. Together, these assumptions require an instantaneous equilibrium for water in intra-and extracapillary spaces.More recently, two conceptually different models have been proposed to account for restricted water exchange between intra-and extracapillary compartments. One model (14,15) assumes well-mixed concentrations of ASL water in each of the two compartments. The other model, also known as a distributed model, accounts for variations of ASL water concentration along the capillary path (or along both intra-and extracapillary spaces) (12,13). In practice, however, this approach may not be applicable, since some parameters (e.g., capillary length) are not accurately known (12). Although both models focus on the effect of restricted water exchange, they do not systematically include transit effects for labeled spins, such as the time to arrival (t A ) and the bolus duration (). Both parameters are generally associated with heterogeneous values for labeled spins because they travel along different trajectories of the feeding vessels.After the labeled spins arrive at the image voxel, there may also be an additional delay (t ex ) before water exchange in the capillary bed can begin, because labe...

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Section: Resultsmentioning

confidence: 99%

Four‐phase single‐capillary stepwise model for kinetics in arterial spin labeling MRI

Zhu

Hylton

et al. 2005

Magnetic Resonance in Med

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“…Both single or multishot echo planar imaging (EPI) and fast low angle shot (FLASH) can achieve this temporal resolution, but vary in the number of slices that may be acquired: EPI sequences can typically acquire up to 15 slices (matrix resolution 1286128 or greater) within this time frame [14,15]. Three-dimensional volumetric sequences have been employed in an attempt to increase volume coverage at the expense of either spatial or temporal resolution [16].…”

Section: Dynamic Susceptibility Contrast Mrimentioning

confidence: 99%

Dynamic contrast-enhanced imaging techniques: CT and MRI

O’Connor¹,

Tofts²,

Miles³

et al. 2011

BJR

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173

121

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ABSTRACT. Over the last few decades there has been considerable research into quantifying the cerebral microvasculature with imaging, for use in studies of the human brain and various pathologies including cerebral tumours. This review highlights key issues in dynamic contrast-enhanced CT, dynamic contrast-enhanced MRI and arterial spin labelling, the various applications of which are considered elsewhere in this special issue of the British Journal of Radiology. The tumour microvasculature can readily be imaged using X-ray, CT and MRI techniques. This review concentrates on three main methods. Dynamic contrast-enhanced CT (DCE-CT) and dynamic contrastenhanced MRI (DCE-MRI) are well-established techniques, where data acquisition and analysis are comparable despite inherent differences in signal production and mechanism of tissue contrast enhancement (reviewed in [1,2]). Although they can be performed on conventional clinical scanners, they require specialist image analysis to extract biomarkers of tumour vascular function. In distinction, arterial spin labelling (ASL) offers a highly specific method of measuring cerebral perfusion without exogenous contrast agent (CA) administration, but is at present a research technique. The practical applications of these techniques are considered elsewhere in this special issue. Basic principles of dynamic contrast-enhanced imagingDCE imaging describes the acquisition of a baseline image(s) without contrast enhancement followed by a series of images acquired over time after an intravenous bolus of conventional CA. The presence of CA within cerebral blood vessels and tissues affects measured X-ray attenuation on CT in a linear fashion and the calculated signal intensity on MRI in a non-linear manner. Thus, the temporal changes in contrast enhancement effectively provide a time-concentration curve, which can be analysed to quantify a range of physiological parameters that indicate the functional status of the vascular system within tumours and adjacent tissues. These parameters reflect the two-compartment pharmacokinetics exhibited by CA, comprising intravascular and extravascular components. During the first-pass of the CA through the circulation (typically 45-60 s after injection), CA is predominantly intravascular allowing evaluation of perfusion (i.e. blood flow per unit volume or mass of tissue), relative blood volume (rBV) and mean transit time. During the subsequent 2-10 min, there is increasing passage of CA into the extravascular space, and imaging during this delayed phase enables measurement of vascular permeability and relative extravascular volume. DCE-CT image acquisition protocolsA number of distinct DCE-CT techniques have been developed, reflecting the different analysis methodologies adopted by commercial software packages for perfusion CT. The main acquisition factors to be considered are summarised in Table 1. For DCE-CT, the need to keep the radiation burden as low as practicable is a constraint on the total number of images acquired and the X-ray exposure ...

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“…To assess the goodness of the fit, scaled fitting error (SFE; Ref. 16) was measured in all fitting procedures. After performing these fits, the ''best'' t 0 was chosen to be that from the fit with the lowest SFE value.…”

Section: ½2mentioning

confidence: 99%

“…An automated simplex minimization procedure (15) was used for fitting. To assess the goodness of the fit, SFEs (16) were produced in all fitting procedures. Figure 1 shows the simulated AIF and the theoretical C t (t) tissue curves generated using Eq.…”

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confidence: 99%

An improved coverage and spatial resolution—using dual injection dynamic contrast‐enhanced (ICE‐DICE) MRI: A novel dynamic contrast‐enhanced technique for cerebral tumors

Buonaccorsi

Thompson

et al. 2012

Magnetic Resonance in Med

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A new dual temporal resolution-based, high spatial resolution, pharmacokinetic parametric mapping method is describedimproved coverage and spatial resolution using dual injection dynamic contrast-enhanced (ICE-DICE) MRI. In a dualbolus dynamic contrast-enhanced-MRI acquisition protocol, a high temporal resolution prebolus is followed by a high spatial resolution main bolus to allow high spatial resolution parametric mapping for cerebral tumors. The measured plasma concentration curves from the dual-bolus data were used to reconstruct a high temporal resolution arterial input function. The new method reduces errors resulting from uncertainty in the temporal alignment of the arterial input function, tissue response function, and sampling grid. The technique provides high spatial resolution 3D pharmacokinetic maps (voxel size 1.0 3 1.0 3 2.0 mm 3 ) with whole brain coverage and greater parameter accuracy than that was possible with the conventional single temporal resolution methods. High spatial resolution imaging of brain lesions is highly desirable for small lesions and to support investigation of heterogeneity within pathological tissue and peripheral invasion at the interface between diseased and normal brain. The new method has the potential to be used to improve dynamic contrast-enhanced-MRI techniques in general. Magn Reson Med 68:452-462, 2012. V C 2012 Wiley Periodicals, Inc.

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Parametric mapping of scaled fitting error in dynamic susceptibility contrast enhanced MR perfusion imaging.

Cited by 17 publications

References 25 publications

Four‐phase single‐capillary stepwise model for kinetics in arterial spin labeling MRI

Four‐phase single‐capillary stepwise model for kinetics in arterial spin labeling MRI

Dynamic contrast-enhanced imaging techniques: CT and MRI

An improved coverage and spatial resolution—using dual injection dynamic contrast‐enhanced (ICE‐DICE) MRI: A novel dynamic contrast‐enhanced technique for cerebral tumors

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