Higher-Resolution Magnetic Resonance Elastography in Meningiomas to Determine Intratumoral Consistency

Abstract

Background: Magnetic resonance elastography (MRE) analyzes shear wave movement through tissue to determine stiffness. In a prior study, measurements with first-generation brain MRE techniques correlated with intraoperative observations of overall meningioma stiffness.

Objective: To evaluate the diagnostic accuracy of a higher-resolution MRE technique to preoperatively detect intratumoral variations compared with surgeon assessment.

Methods: Fifteen meningiomas in 14 patients underwent MRE. Tumors with regions of distinctly different stiffness were considered heterogeneous. Intratumoral portions were considered hard if there was a significant area ≥6 kPa. A 5-point scale graded intraoperative consistency. A durometer semiquantitatively measured surgical specimen hardness. Statistics included χ, sensitivity, specificity, positive and negative predicative values, and Spearman rank correlation coefficient.

Results: For MRE and surgery, 9 (60%) and 7 (47%) tumors were homogeneous, 6 (40%) and 8 (53%) tumors were heterogeneous, 6 (40%) and 10 (67%) tumors had hard portions, and 14 (93%) and 12 (80%) tumors had soft portions, respectively. MRE sensitivity, specificity, and positive and negative predictive values were as follows: for heterogeneity, 75%, 100%, 100%, and 87%; for hardness, 60%, 100%, 100%, and 56%; and for softness, 100%, 33%, 86%, and 100%. Overall, 10 tumors (67%) matched well with MRE and intraoperative consistency and correlated between intraoperative observations (P = .02) and durometer readings (P = .03). Tumor size ≤3.5 cm or vascular tumors were more likely to be inconsistent (P < .05).

Conclusion: MRE was excellent at ruling in heterogeneity with hard portions but less effective in ruling out heterogeneity and hard portions, particularly in tumors more vascular or <3.5 cm. MRE is the first technology capable of prospectively evaluating intratumoral stiffness and, with further refinement, will likely prove useful in preoperative planning.

Figures

Figure 1

(A) CT head of a large parietooccipital parasagittal meningioma with a nodule of tumor on the left extending further anteriorly. The right side of the tumor is calcified. (B) T1 weighted MRI with contrast defines the tumor further.(C) MRE shows the tumor is heterogenous with the posterior portion being hard and the more left lateral and anterior nodule becoming progressively softer. Intraoperatively, the posterior region of the tumor had to be removed with heavy scissors, but as the dissection moved to the left and anteriorly, the tumor was easily removed with the ultrasonic aspirator at low settings.

Figure 2

(A) CT head of an isodense right frontal convexity tumor. (B) T1 weighted MRI with contrast shows a homogenously enhancing tumor consistent with meningioma.(C) MRE shows a soft homogenous tumor. Intraoperatively, the tumor was easily removed with ultrasonic aspirator and was consistent throughout.

Figure 3

Flow diagram of MRE results compared with surgeon assessment.

Figure 4

Graphs showing correlation of MRE measurements and the surgeons’ impression (A), MRE measurements and durometer readings (B), and durometer measurements and the surgeon’s impression (C) in the tumors that were similar between MRE and intraoperative findings. All had good correlation with p

Figure 5

Examples of tumors that did not correlate well with MRE and surgical findings. (A). A small planum sphenoidale meningioma that measured 2.2 cm in maximum diameter. MRE showed the tumor to be homogenous and soft; intraoperatively the tumor was 70% soft, but 30% was very firm in the region along the left internal carotid artery. (B) A right convexity meningioma that measured 6.5 cm in maximum diameter. Note the flow voids within the tumor and preoperative angiography confirmed a highly vacular tumor. MRE showed the tumor to be soft and homogenous. At surgery, the tumor was consistent throughout, but required cautery to remove as it was fibrous.