Background: In pediatric epilepsy, T1-weighted brain MRI with Gadolinium ('T1+Gd') can be rendered to display vasculature and cortical morphology for surgical planning. T1+Gd images are not always available, and may not be preferable where patients have needle or procedural aversion, or allergies to contrast agent. We utilized T2-weighted ('T2') images to generate 'T2 Vessel Maps' that emulate the tissue and vessel intensities in T1+Gd images. We aimed to quantitatively validate T2 Vessel Maps with relation to T1+Gd versions, and qualitatively describe clinical utility of T2- and T1+Gd Vessel Maps.
Methods: The study design was a retrospective quantitative validation study and clinical case series. For the quantitative analysis, we retrospectively identified 16 epilepsy patients with operative photographs and T2 and T1+Gd images (age 1.0-18.1 years; 6 female). For the qualitative case series, we retrospectively identified 10 epilepsy patients with operative photographs and T2 Vessel Maps used in presurgical planning (0.4-18.1 years, 4 female). For the quantitative analysis, vessel segments were traced by raters on T2- and T1+Gd Vessel Maps, and traced on operative photographs as "ground truth". Quantities of vessels captured by T2- and T1+Gd Vessel Maps were assessed using ratios of rater-traced vessel segments to ground truth, and rater-traced vessel segments on T2- vs. T1+Gd Maps. Linear mixed effects models were used to test effects of MRI modality and vessel type on ratios. For the case series, neurosurgeons were interviewed regarding utility of T2- and T1+Gd Vessel Maps.
Results: For the quantitative analysis, the ratio of rater-traced segments to ground truth was lower for T2- than T1+Gd Vessel Maps (estimate -0.137, 95 % CI [-0.180, -0.095], t = -6.30, p < 0.001). The ratio of traced vessel segments for T2 vs T1+Gd Vessel Maps had mean = 0.752. No difference was found for vessel type (estimate -0.02, 95 % CI [-0.115, 0.067], t = -0.51, p = 0.610). For the case series, neurosurgeons described use, advantages and disadvantages of T2 and T1+Gd Vessel Maps. Usage was primarily in providing vessel and surface morphology landmarks for surgical planning. In most cases, vessels on T2 Vessel Maps were reported to be a good match with those on the cortical surface.
Conclusion: Whilst T2 Vessel Maps were found to capture fewer vessels than T1+Gd versions, they were reported useful in pediatric epilepsy surgery, avoiding the need for additional T1+Gd sequences.
Keywords: 3D visualisation; Epilepsy surgery; Pediatrics; Presurgical planning; T2-weighted MRI; Vasculature.
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