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Erschienen in:
01.06.2015 | Diagnostic Neuroradiology
The impact of reliable prebolus T 1 measurements or a fixed T 1 value in the assessment of glioma patients with dynamic contrast enhancing MRI
Erschienen in: Neuroradiology | Ausgabe 6/2015
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Introduction
Accurate quantification of hemodynamic parameters using dynamic contrast enhanced (DCE) MRI requires a measurement of tissue T
1 prior to contrast injection (T
1). We evaluate (i) T
1 estimation using the variable flip angle (VFA) and the saturation recovery (SR) techniques and (ii) investigate if accurate estimation of DCE parameters outperform a time-saving approach with a predefined T
1 value when differentiating high- from low-grade gliomas.
Methods
The accuracy and precision of T
1 measurements, acquired by VFA and SR, were investigated by computer simulations and in glioma patients using an equivalence test (p > 0.05 showing significant difference). The permeability measure, K
trans, cerebral blood flow (CBF), and - volume, V
p, were calculated in 42 glioma patients, using fixed T
1 of 1500 ms or an individual T
1 measurement, using SR. The areas under the receiver operating characteristic curves (AUCs) were used as measures for accuracy to differentiate tumor grade.
Results
The T
1 values obtained by VFA showed larger variation compared to those obtained using SR both in the digital phantom and the human data (p > 0.05). Although a fixed T
1 introduced a bias into the DCE calculation, this had only minor impact on the accuracy differentiating high-grade from low-grade gliomas, (AUCfix = 0.906 and AUCind = 0.884 for K
trans; AUCfix = 0.863 and AUCind = 0.856 for V
p;
p for AUC comparison > 0.05).
Conclusion
T
1 measurements by VFA were less precise, and the SR method is preferable, when accurate parameter estimation is required. Semiquantitative DCE values, based on predefined T
1 values, were sufficient to perform tumor grading in our study.