Perfusion MRI of the human brain with dynamic susceptibility contrast: Gradient-echo versus spin-echo techniques

Speck, Oliver; Chang, Linda; DeSilva, N. Menaka; Ernst, Thomas

doi:10.1002/1522-2586(200009)12:3<381::aid-jmri2>3.0.co;2-y

Cited by 80 publications

(62 citation statements)

References 27 publications

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“…The value of ε empirically found was 0.15 for the GE and 0.075 for the SE measurements. The following function with a postcontrast baseline was fitted directly to the signal time course of each selected voxel using Powell's algorithm to minimize the sum of squared differences between the data points and the model function (17,18):…”

Section: Data Processingmentioning

confidence: 99%

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Vessel size imaging in humans

Kiselev

Strecker

Ziyeh

et al. 2005

Magnetic Resonance in Med

180

286

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The relation of contrast-enhanced transverse relaxation rates R 2 * and R 2 provides in vivo mapping of the mean caliber of cerebral vessels. This technique is referred to as vessel size imaging (VSI) The microvasculature, which includes the smallest and intermediate vessels, cannot be imaged directly with current MRI techniques. MRI examinations yield averaged microvasculature-related characteristics of perfusion or pharmacokinetics. Recently, attempts have been made to measure the mean vessel caliber in vivo (1, 2) in animal models. The feasibility of such measurements is granted by the difference in the contributions of small vessels to the transverse relaxation rates of the free induction decay, R* 2 , and that of the spin echo (SE), R 2 , (3-7) (Fig. 1). The method is based on measuring the changes in both rates, ⌬R* 2 and ⌬R 2 , after administration of a paramagnetic contrast agent. The average vessel size in a tissue can be estimated from ⌬R* 2 and ⌬R 2 according to theoretical predictions provided either by Monte Carlo simulations (2, 3) or by analytical modeling (4,8,9)..A quantitative assessment of the microvasculature might have diagnostic impact on the differential diagnosis of intracranial tumors. In a recent study (5) a correlation was found between glioma grade and regional cerebral blood volume (rCBV) measured with a gradient echo (GE) technique, while SE data showed no significant correlation. This result was qualitatively explained by the higher sensitivity of R* 2 to large vessels, which are inherent to malignant tumor tissues. Similarly, it was reported (6, 7) that the difference in regional blood volume assessed with GE and SE techniques increases for high-grade brain tumors.In the present study, quantitative imaging of the mean vessel caliber was performed in brain tumor patients undergoing routine MRI examinations. Previous experiments were performed in animals (2) using an intravascular contrast agent (USPIO) and monitoring its blood concentration invasively. The present method has been developed to meet the conditions of human studies in a clinical environment, in particular, the transient character of the contrast enhancement during the first bolus passage. The analysis presented and computer simulations help to understand the restrictions of the method and its shortcomings, which are caused by the complex relationship between the microvascular morphology and the measured NMR signal. Four illustrative cases of brain tumors are discussed in the context of the model developed.

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Section: Data Processingmentioning

confidence: 99%

“…[12] are measured as the differences between the relaxation rates during the bolus passage and their baseline values. Equation [17] yields the following mathematical model for these quantities:…”

Section: Contribution Of Intravascular Spinsmentioning

confidence: 99%

Vessel size imaging in humans

Kiselev

Strecker

Ziyeh

et al. 2005

Magnetic Resonance in Med

180

286

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“…Practical application of Eq. [5] to measurement of CBV, the relative volume of the microvasculature within an ROI, requires additional corrections for the density of brain tissue ( ϭ 1.04 g/ml) (23) and for the fact that the hematocrit in large vessels is greater than the hematocrit in small vessels (9). The necessary hematocrit correction factor, h, can be calculated from the animal's measured venous hematocrit as [8] where Hct and mHct are the large vessel and microvessel hematocrits, respectively, and r ϭ mHct / Hct.…”

Section: Theorymentioning

confidence: 99%

Cerebral blood volume measurements by rapid contrast infusion and T‐weighted echo planar MRI

Tudorica

Li²,

Hospod³

et al. 2002

Magnetic Resonance in Med

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Cerebral blood volume (CBV) provides information complementary to that of cerebral blood flow in cerebral ischemia, tumors, and other conditions. We have developed an alternative theory and method for measuring CBV based on dynamic imaging by MRI or CT during a short contrast infusion. This method avoids several limitations of traditional approaches that involve waiting for steady state or measuring the area under the curve (AUC) during bolus contrast injection. Anesthetized dogs were studied by T* 2 -weighted echo planar imaging during gadolinium-DTPA infusions lasting 30 -60 sec. CBV was calculated from the ratio of the signal changes in tissue and artery. Method responsiveness was compared to AUC measurements using the vasodilator acepromazine. The ratio of signal change in tissue to that in artery rapidly approached an asymptotic value even while the amount of contrast in artery continued to increase. Using 30-sec infusions, the mean (؎SD) of CBV for control animals was 3.6 ؎ 0.9 ml blood/100 g tissue in gray matter and 2.3 ؎ 0.8 ml blood/100 g tissue in white matter (ratio ‫؍‬ 1.6). Acepromazine increased CBV to 5.7 ؎ 1.5 ml blood/100 g tissue in gray matter and 3.1 ؎ 0.8 ml blood/100 g tissue in white matter (ratio ‫؍‬ 2.0). AUC measurements after bolus injection yielded similar values for control animals but failed to demonstrate any change after acepromazine. It is possible to measure CBV using dynamic MRI or CT during 30 -60-sec contrast infusions. This method may be more sensitive to changes in CBV than traditional AUC methods.

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“…4 Measurement of T2* and T2Ј values has been used for determination of iron tissue concentration, 5 and calculation of T2Ј values has already been used in MR imaging in acute stroke to investigate the oxygen extraction fraction (OEF) in acute ischemic stroke 2,6 and chronic misery perfusion. 7,8 However, normal reference T2Ј values have not been reported so far, and the determination of T2Ј reference values is mandatory for future applications in ischemic disease. In our study, T2* and T2Ј values (and T2 values as control) were determined with MR imaging in distinct regions of interest (ROIs) in the WM and in the basal ganglia in subjects without intraparenchymal pathologic processes to determine age-related normal values.…”

mentioning

confidence: 99%