Comparison between voxel-based and subtraction methods for measuring diffusion-weighted imaging lesion growth after thrombolysis. Issue 2 (February 2016)

• Record Type: Journal Article
• Authors: Hassen, Wajih Ben; Tisserand, Marie; Turc, Guillaume; Charron, Sylvain; Seners, Pierre; Edjlali, Myriam; Legrand, Laurence; Lion, Stéphanie; Calvet, David; Naggara, Olivier; Mas, Jean-Louis; Meder, Jean-François; Baron, Jean-Claude; Oppenheim, Catherine
• Is Part Of: International journal of stroke. Volume 11:Issue 2(2016)
• Page Start: 221
• Page End: 228
• Publication Date: 2016-02
• Subjects: MRI -- diffusion-weighted imaging -- infarct growth -- outcomes -- thrombolysis -- coregistration; 616.8005
• DOI: 10.1177/1747493015616636
• Languages: English
• ISSNs: 1747-4930

Abstract

Background: Infarct growth (IG) is used as surrogate end-point in therapeutic trials. For practical reasons, infarct growth is commonly assessed using simple subtraction of acute from follow-up diffusion-weighted imaging (DWI) lesion volumes. However, the volume subtraction method will underestimate true infarct growth in case of diffusion-weighted imaging lesion reversal. Aim: To measure the size of the difference between true infarct growth on voxel-based coregistration and infarct growth approximated with simple volume subtraction. Methods: We retrospectively analyzed 322 consecutive stroke patients (median (IQR) age: 70 years (57–80), National Institute of Health Stroke Score at admission 14 (8–19)), who underwent a magnetic resonance imaging before (DWI1 ) and ≈24 h (DWI2 ) after IV-thrombolysis. IGvoxel-based was defined as the volume of signal changes on DWI2 that did not overlap with that on coregistered DWI1 . This was compared with simply subtracting DWI1 from DWI2 lesion volume (IGsubtracted ). We also compared these two metrics for the prediction of three-month unfavorable outcome (mRS ≥ 2) using c-statistics of multivariable models, adjusted for age, and National Institute of Health Stroke Score. Results: Infarct growth volume metrics were strongly correlated (ρ = 0.94), but IGsubtracted substantially underestimated IGvoxel-based (median (IQR): 9.52 (0.23–38.9) vs. 16.98 (4.4–45.4) mL). Of the 75 patients with shrinking or stable diffusion-weighted imaging lesion using volume subtraction, IGvoxel-based was ≥5 mL in 20 (27% of the subset, 6.2% of the whole population). Moreover, IGvoxel-based better predicted unfavorable outcome than IGsubtracted (c-statistics = 0.86 (95% CI, 0.82–0.90) vs. 0.82 (0.78–0.87), P = 0.003). Conclusion: At early post-thrombolysis time points, the simple subtraction of lesion volumes masked substantial diffusion-weighted imaging lesion growth in 6.2% of patients. Although more time-consuming, the voxel-based method may impact results of trials that use infarct growth attenuation as an end-point.