Apparent transverse relaxation (R2∗) on MRI as a method to differentiate treatment effect (pseudoprogression) versus progressive disease in chemoradiation for malignant glioma

Abstract

Introduction

Pseudoprogression (psPD) is a transient post-treatment imaging change that is commonly seen when treating glioma with chemotherapy and radiation. The use of apparent transverse relaxation rate (), which is calculated from a contrast-free multi-echo gradient echo Magnetic Resonance Imaging (MRI) sequence, may allow for quantitative identification of patients with suspected psPD.

Methods

We acquired a multi-echo gradient echo sequence using a 3T-Siemens Prisma MRI. The signal decay through the echoes was fitted to provide the coefficient. We segmented the T₁-gadolinium enhancing the image to provide a contrast enhancing lesion (CEL) and the FLAIR hyperintensity to provide a non-enhancing lesion (NEL). These regions of interest were applied to the multi-echo gradient echo to acquire a mean within the CEL and NEL. We additionally acquired ADC data to attempt to corroborate our findings.

Results

We found that patients who later exhibited PD exhibited a higher within the CEL as well as a higher ratio of CEL to NEL. Our data correctly distinguished pseudoprogression from treatment effect in 9/9 patients, while ADC corrected identified 7/9 patients using an absolute ADC of 1200 × 10⁻⁶ mm²/s.

Conclusions

Our method seems promising for the accurate identification of psPD, and the technique is amenable to evaluation in larger, multi-centre patient cohorts.

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