Abstract
Accurate tumor grading is essential for treatment planning of pediatric brain tumors. We hypothesized that multiparametric analyses of a combination of permeability metrics and ADC histogram metrics would differentiate high- and low-grade tumors with high accuracy. DTI and dynamic contrast-enhanced MR imaging using T1-mapping with flip angles of 2°, 5°, 10°, and 15°, followed by a 0.1-mmol/kg body weight gadolinium-based bolus was performed on all patients in addition to standard MR imaging. Permeability data were processed and transfer constant from the blood plasma into the extracellular extravascular space, rate constant from the extracellular extravascular space back into blood plasma, extravascular extracellular volume fraction, and fractional blood plasma volume were calculated from 3D tumor volumes. Apparent diffusion coefficient histogram metrics were calculated for 3 separate tumor volumes derived from T2-FLAIR sequences, T1 contrast-enhanced sequences, and permeability maps, respectively. Results from 41 patients (0.3-16.76 years of age; mean, 6.22 years) with newly diagnosed contrast-enhancing brain tumors (16 low-grade; 25 high-grade) were included in the institutional review board-approved retrospective analysis. Wilcoxon tests showed a higher transfer constant from blood plasma into extracellular extravascular space and rate constant from extracellular extravascular space back into blood plasma, and lower extracellular extravascular volume fraction (P < .001) in high-grade tumors. The mean ADCs of FLAIR and enhancing tumor volumes were significantly lower in high-grade tumors (P < .001). ROC analysis showed that a combination of extravascular volume fraction and mean ADC of FLAIR volume differentiated high- and low-grade tumors with high accuracy (area under receiver operating characteristic curve = 0.918). ADC histogram metrics combined with permeability metrics differentiate low- and high-grade pediatric brain tumors with high accuracy.
Highlights
MethodsDTI and dynamic contrast-enhanced MR imaging using T1-mapping with flip angles of 2°, 5°, 10°, and 15°, followed by a 0.1-mmol/kg body weight gadolinium-based bolus was performed on all patients in addition to standard MR imaging
BACKGROUND AND PURPOSEAccurate tumor grading is essential for treatment planning of pediatric brain tumors
Receiver operating characteristic (ROC) analysis showed that a combination of extravascular volume fraction and mean ADC of FLAIR volume differentiated high- and low-grade tumors with high accuracy
Summary
DTI and dynamic contrast-enhanced MR imaging using T1-mapping with flip angles of 2°, 5°, 10°, and 15°, followed by a 0.1-mmol/kg body weight gadolinium-based bolus was performed on all patients in addition to standard MR imaging. All patients underwent a DCE-MR imaging protocol as follows: 1) variable flip angle echo-spoiled gradient-echo T1-mapping sequences using flip angles of 15°, 10°, 5°, and 2°; TR ϭ 5 seconds; TE ϭ minimum; FOV ϭ 240 mm; section thickness ϭ 5 mm; and 2) DCE-MR imaging sequence consisting of 50 phases, 7 seconds apart, flip angle ϭ 15°, TR ϭ 4 seconds, TE ϭ minimum. Low- and high-grade tumor groups were compared for permeability variables and ADC histogram metrics using the Wilcoxon test and t test using the NPAR1WAY and t test procedures of SAS (SAS Institute, Cary, North, Carolina).[16] Corresponding to the t test, estimates and 95% confidence intervals for the difference between means were calculated. The AROC estimates the average true-positive rate over all possible false-positive rates and is an estimate of the probability of correctly classifying a random pair of patients, 1 from the low-grade group and 1 from the high-grade group
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