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Published on: July 28, 2013
Apparent transverse relaxation (R2∗) on MRI as a method to differentiate treatment effect (pseudoprogression) versus
Jean-Guy Belliveau1,2, Glenn S Bauman1,3,4, David Macdonald3,4
1Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada.
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 (R2∗), 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 R2∗ 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 R2∗ 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 R2∗ 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.
Insights
Quantitative MRI using apparent transverse relaxation rate (R2∗) shows promise in accurately identifying pseudoprogression (psPD) in glioma patients. This technique offers improved diagnostic accuracy compared to ADC for distinguishing psPD from treatment effects.
Area of Science:
- Radiology
- Neuro-oncology
- Medical Imaging
Background:
- Pseudoprogression (psPD) is a common transient imaging finding after glioma treatment with chemotherapy and radiation.
- Accurate differentiation of psPD from true tumor progression is crucial for appropriate patient management.
- Current imaging methods may have limitations in reliably distinguishing psPD.
Purpose of the Study:
- To investigate the utility of apparent transverse relaxation rate (R2∗) derived from contrast-free multi-echo gradient echo MRI for quantitative identification of psPD in glioma patients.
- To compare the diagnostic performance of R2∗ with apparent diffusion coefficient (ADC) in differentiating psPD from treatment effects.
Main Methods:
- Acquisition of multi-echo gradient echo MRI sequence at 3T to calculate R2∗.
- Segmentation of contrast-enhancing lesions (CEL) and non-enhancing lesions (NEL) from T1-gadolinium and FLAIR images, respectively.
- Application of R2∗ measurements within CEL and NEL, and correlation with ADC data.
Main Results:
- Patients with psPD demonstrated higher R2∗ values within the CEL and a higher CEL to NEL ratio.
- The R2∗ method accurately distinguished psPD from treatment effects in all 9 evaluated patients (100% accuracy).
- ADC correctly identified 7 out of 9 patients (78% accuracy) using a threshold of 1200 × 10-6 mm2/s.
Conclusions:
- Quantitative R2∗ imaging is a promising technique for accurate psPD identification in glioma.
- The R2∗ method shows superior performance compared to ADC in differentiating psPD from treatment effects.
- This technique warrants further evaluation in larger, multi-center studies.
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