42 Chapter 2 Table 4. Linear mixed model on the three gyri of the frontal lobe of 41 subjects using the Hammers Atlas (mL/100g/min). Inferior Frontal Gyrus Value Std.Error 2.5% 97.5% (Intercept) 52.81 4.68 43.54 62.08 trigonocephaly patient 8.13 5.34 -2.71 18.97 regASLrigid 9.33 0.90 7.55 11.12 regASLaffine 17.11 0.90 15.32 18.89 regASLdct 17.45 0.90 15.67 19.24 Middle frontal Gyrus (Intercept) 50.15 5.07 40.09 60.21 trigonocephaly patient 1.93 5.78 -9.82 13.67 regASLrigid 10.59 1.05 8.51 12.68 regASLaffine 18.94 1.05 16.86 21.02 regASLdct 18.49 1.05 16.40 20.57 Superior Frontal Gyrus (Intercept) 45.75 4.63 36.58 54.93 trigonocephaly patient 9.39 5.27 -1.32 20.09 regASLrigid 14.28 1.00 12.29 16.26 regASLaffine 18.99 1.00 17.01 20.98 regASLdct 18.88 1.00 16.90 20.87 DISCUSSION In this study, we have shown that direct normalization of ASL images to MNI space using ASL CBF as image contrast outperforms spatial normalization based on T1w segmentation in MRI brain studies of both patients and controls who are less than 2 years of age. The nonlinear registration outperformed both rigid and affine registration among the methods using the ASL CBF contrast. While better results in TC of the regASLdct were shown for the control group, the difference between regT1 and regASLdct was even higher in patients in both qualitative analysis and CBF analysis. The CBF values in three gyri of the frontal lobe, which are clinically relevant for trigonocephaly patients, were significantly different compared with the CBF values extracted using the spatial normalization with the regT1 method. This shows the impact of the choice of registration contrast and the importance of this proposed method in a cohort where gray-white matter contrast in structural images is low due to ongoing myelination. Using the SPM-based segmentation and normalization pipeline in ExploreASL with T1w, our initial attempts to register and segment the brain of trigonocephaly patients
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