Comparison of dynamic susceptibility-weighted contrast-enhanced MR methods: recommendations for measuring relative
Eric S Paulson1, Kathleen M Schmainda
1Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Purpose:
To investigate whether estimates of relative cerebral blood volume (rCBV) in brain tumors, obtained by using dynamic susceptibility-weighted contrast material-enhanced magnetic resonance (MR) imaging vary with choice of data acquisition and postprocessing methods.
Materials And Methods:
Four acquisition methods were used to collect data in 22 high-grade glioma patients, with informed written consent under HIPAA-compliant guidelines approved by the institutional review board. During bolus administration of a standard single dose of gadolinium-based contrast agent (0.1 mmol per kilogram of body weight), one of three acquisition methods was used: gradient-echo (GRE) echo-planar imaging (echo time [TE], 30 msec; flip angle, 90 degrees ; n = 10), small-flip-angle GRE echo-planar imaging (TE, 54 msec; flip angle, 35 degrees ; n = 7), or dual-echo GRE spiral-out imaging (TE, 3.3 and 30 msec; flip angle, 72 degrees ; n = 5). Next, GRE echo-planar imaging (TE, 30 msec; flip angle, 90 degrees ; n = 22) was used to collect data during administration of a second dose of contrast agent (0.2 mmol/kg). Subsequently, six methods of analysis were used to calculate rCBV. Mean rCBV values from whole tumor, tumor hot spots, and contralateral brain were normalized to mean rCBV in normal-appearing white matter.
Results:
Friedman two-way analysis of variance and Kruskal-Wallis one-way analysis of variance results indicated that qualitative rCBV values were dependent on acquisition and postprocessing methods for both tumor and contralateral brain. By using the nonparametric Mann-Whitney test, a consistently positive (greater than zero) tumor-contralateral brain rCBV ratio resulted when either the preload-postprocessing correction approach or dual-echo acquisition approach (P < .008 for both methods) was used.
Conclusion:
The dependence of tumor rCBV on the choice of acquisition and postprocessing methods is caused by their varying sensitivities to T1 and T2 and/or T2* leakage effects. The preload-correction approach and dual-echo acquisition approach are the most robust choices for the evaluation of brain tumors when the possibility of contrast agent extravasation exists.
