Quantitative diffusion-weighted and dynamic susceptibility-weighted contrast-enhanced perfusion MR imaging analysis of T2 hypointense lesion components in pediatric diffuse intrinsic pontine glioma

Abstract

Background and purpose: Focal anaplasia characterized by T2 hypointensity, signal-intensity enhancement on postcontrast T1-weighted MR imaging and restricted water diffusion has been reported in a patient with juvenile pilocytic astrocytoma. We identified T2(HOF) with these MR imaging characteristics in children with DIPG and hypothesized that these represent areas of focal anaplasia; and may, therefore, have increased perfusion properties and should be characterized by increased perfusion. Thus, we used DSC to investigate our hypothesis.

Materials and methods: We retrospectively reviewed the baseline MR imaging scans of 86 patients (49 girls, 37 boys; median age, 6.1 years; range, 1.1-17.6 years) treated for DIPG at our hospital (2004-2009). T2(HOF) with the described MR imaging characteristics was identified in 10 patients. We used a region of interest-based approach to compare the ADC, FA, rCBV, rCBF, and rMTT of T2(HOF) with those of the typical T2(HRT).

Results: The ADC of T2(HOF) with the specified MR imaging characteristics was significantly lower than that of T2(HRT) (range, 0.71-1.95 μm(2)/ms versus 1.36-2.13 μm(2)/ms; P < .01); and the FA (range, 0.12-0.34 versus 0.07-0.24; P = .03) and rCBV (range, 0.4-2.62 versus 0.23-1.57; P = .01) values of T2(HOF)s were significantly higher.

Conclusions: Our data suggest that T2(HOF) in DIPG may represent areas of focal anaplasia and underline the importance of regional, rather than global, tumor-field analysis. T2(HOF) may be the ideal target when stereotactic biopsy of tumors that present with an inhomogeneous T2 signal intensity is considered.

Figures

Fig 1.

Regions of interest for T2HOF (1), T2HRT (2), WM (3), and GM (4) shown on the ADC map (left) and the T2*-weighted perfusion image before injection of contrast agent (right).

Fig 2.

Signal-intensity curves of the tumor areas (T2HOF and T2HRT), the normal-appearing cerebellar WM and GM, and the AIF for a single patient. The markers indicate the actual values measured; the lines indicate the fit functions to the first pass of the contrast agent.

Fig 3.

Appearance of T2HOF on conventional MR imaging and DWI for the 10 patients included in the evaluation of quantitative data. From left to right: T2-weighted, T1 subtraction image (or T1-weighted postcontrast image), diffusion trace image, and ADC map.

Fig 4.

Results of diffusion imaging. A, ADC values of all lesions are significantly lower. B, FA values (not available for all patients) are significantly higher in T2HOF (y-axis) than in T2HRT (x-axis).

Fig 5.

Results of perfusion imaging. A, rCBV values are significantly higher in T2HOF (y-axis) than in T2HRT (x-axis). B and C, No statistically significant difference is observed for (B) rCBF and (C) rMTT. Parameters were calculated relative to normal-appearing cerebellar GM.