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T2 and DWI in pilocytic and pilomyxoid astrocytoma with pathologic correlation
M Horger1, M N Vogel, R Beschorner
1Department of Diagnostic and Interventional Radiology, Eberhard-Karls-University, Tübingen, Germany.
Objective:
To quantify and compare T2 signal and apparent diffusion coefficient (ADC) in pilocytic and pilomyxoid astrocytoma (PA and PMA) and correlate results with myxoid content.
Methods:
Echo-planar diffusion weighted images (DWI) and standard magnetic resonance imaging (MRI) findings were reviewed retrospectively in patients with PA (n=34) and PMA (n=8). Regions of interest (ROIs) were drawn on ADC maps within tumor parts with lowest ADC values. Apparent diffusion coefficient values in tumor were normalized to those in cerebrospinal fluid (ADC/CSF). The ratio of T2 signal intensity in solid tumor parts to CSF (T2/CSF) was registered. Myxoid matrix was histologically quantified retrospectively in 8 PMAs and 17 PAs and correlated with imaging findings.
Results:
Mean ADC/CSF for PA and PMA was 0.53±0.10 and 0.69±0.10 (p<0.01). Mean T2/CSF for PA and PMA was 0.78±0.19 and 0.93±0.09 (p<0.01). Mean proportion of myxoid tumor matrix in PA was 50% (range, 10-100%) and 93% (range, 90-100%) in PMA (p=0.004). Eight patients (32%; all PA) had less than 50% myxoid content and 17 (68%; 8 PA; 9 PMA) had more. There was positive correlation of ADC/CSF, T2/CSF and ADC (r2=0.61, 0.65 and 0.60 respectively) and significant difference between the groups with more and less than 50% myxoid content (p=0.01 for ADC/CSF and T2/CSF and p=0.02 for ADC).
Conclusions:
General imaging features of PA and PMA are non-specific, ADC values and T2 signal intensity are generally higher in the latter, reflecting the proportion of myxoid matrix in these tumors.
Insights
Pilocytic astrocytoma (PA) and pilomyxoid astrocytoma (PMA) show higher apparent diffusion coefficient (ADC) and T2 signal intensity in PMA, reflecting increased myxoid matrix content. These MRI features aid in differentiating these pediatric brain tumors.
Area of Science:
- Neuro-oncology
- Pediatric neurosurgery
- Radiology and medical imaging
Background:
- Pilocytic astrocytoma (PA) and pilomyxoid astrocytoma (PMA) are common pediatric brain tumors.
- Distinguishing between PA and PMA can be challenging due to overlapping imaging features.
- Myxoid matrix content is a key histological differentiator between PA and PMA.
Purpose of the Study:
- To quantitatively compare T2 signal intensity and apparent diffusion coefficient (ADC) values between pilocytic astrocytoma (PA) and pilomyxoid astrocytoma (PMA).
- To correlate these magnetic resonance imaging (MRI) findings with the proportion of myxoid matrix in the tumors.
- To assess the utility of ADC and T2 signal intensity in differentiating PA from PMA.
Main Methods:
- Retrospective review of echo-planar diffusion-weighted imaging (DWI) and standard MRI in 34 PAs and 8 PMAs.
- Regions of interest (ROIs) were placed on ADC maps to calculate normalized ADC (ADC/CSF) and normalized T2 signal intensity (T2/CSF).
- Histological quantification of myxoid matrix was performed and correlated with imaging parameters.
Main Results:
- PMA demonstrated significantly higher mean ADC/CSF (0.69±0.10) and T2/CSF (0.93±0.09) compared to PA (0.53±0.10 and 0.78±0.19, respectively).
- PMA had a significantly higher proportion of myxoid matrix (93%) compared to PA (50%).
- Positive correlations were found between ADC/CSF, T2/CSF, and ADC values with myxoid content, with significant differences observed between tumors with <50% and >50% myxoid content.
Conclusions:
- General imaging features of PA and PMA are non-specific.
- Higher ADC values and T2 signal intensity in PMA generally reflect a greater proportion of myxoid matrix.
- These quantitative MRI parameters may aid in differentiating between PA and PMA, particularly when considering myxoid content.
