Table 4.
Linear mixed-effects model results of imaging biomarkers of injury (volume, FA, and MD) as predictors of processing speed raw scores.
| Processing Speed |
||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| D-KEFS-TM Number Sequencing | D-KEFS-TM Letter Sequencing | WAIS Coding | ||||||||
| Region | Biomarker | Estimate (β)* | Standard Error | P Value | Estimate (β) | Standard Error | P value | Estimate (β) | Standard Error | P Value |
| Total CC | Volume | 1.110 | 2.340 | .640 | −6.870 | 2.580 | .791 | 3.780 | 2.280 | .099 |
| FA | −0.293 | 0.241 | .227 | −0.086 | 0.255 | .737 | 0.438 | 0.233 | .062 | |
| MD | 12.123 | 10.838 | .264 | −8.587 | 11.017 | .427 | −5.377 | 10.266 | .601 | |
| Posterior CC | Volume | 4.210 | 6.500 | .518 | −0.183 | 7.690 | .981 | 6.590 | 7.360 | .372 |
| FA | −0.168 | 0.149 | .262 | −0.121 | 0.157 | .442 | 0.219 | 0.149 | .142 | |
| MD | 6.137 | 11.163 | .583 | −9.679 | 11.358 | .395 | −4.231 | 10.894 | .698 | |
| Mid-Posterior CC | Volume | 6.420 | 12.400 | .606 | −2.690 | 13.100 | .837 | 16.700 | 12.000 | .169 |
| FA | −0.029 | 0.191 | .881 | −0.060 | 0.201 | .765 | 0.360 | 0.175 | .042 | |
| MD | 6.544 | 10.231 | .523 | −4.977 | 10.332 | .630 | −8.604 | 9.382 | .360 | |
| Central CC | Volume | 5.010 | 13.500 | .721 | −11.400 | 14.300 | .427 | 18.400 | 12.800 | .155 |
| FA | −0.202 | 0.210 | .337 | 0.054 | 0.221 | .808 | 0.265 | 0.197 | .180 | |
| MD | 11.803 | 10.599 | .268 | −11.271 | 10.686 | .293 | −2.816 | 9.784 | .774 | |
| Mid-Anterior CC | Volume | −14.200 | 13.500 | .300 | −24.400 | 14.900 | .109 | 37.800 | 14.600 | .011† |
| FA | −0.172 | 0.200 | .393 | 0.075 | 0.210 | .722 | 0.135 | 0.167 | .420 | |
| MD | 8.906 | 9.129 | .330 | −8.541 | 9.248 | .357 | −3.591 | 8.517 | .674 | |
| Anterior CC | Volume | 3.780 | 7.300 | .612 | 0.224 | 8.440 | .979 | 8.770 | 8.120 | .281 |
| FA | −0.103 | 0.183 | .578 | −0.012 | 0.197 | .950 | 0.327 | 0.188 | .086 | |
| MD | 10.781 | 8.100 | .187 | −3.174 | 8.266 | .701 | −4.481 | 7.511 | .551 | |
| Total IHWM | Volume | −0.101 | 0.068 | .141 | −0.113 | 0.077 | .146 | 0.156 | 0.077 | .046† |
| FA | −0.777 | 0.670 | .249 | −0.173 | 0.807 | .831 | 2.924 | 0.806 | .0004† | |
| MD | 13.327 | 14.136 | .347 | −14.346 | 14.214 | .314 | −7.713 | 13.396 | .565 | |
| Right IHWM | Volume | −0.026 | 0.203 | .899 | −0.111 | 0.237 | .641 | 0.354 | 0.245 | .155 |
| FA | −0.080 | 0.682 | .907 | 0.221 | 0.802 | .783 | 2.202 | 0.811 | .008† | |
| MD | 11.737 | 14.355 | .414 | −15.419 | 14.438 | .287 | −7.456 | 13.572 | .583 | |
| Left IHWM | Volume | −0.454 | 0.201 | .025† | −0.510 | 0.218 | .024† | 0.636 | 0.218 | .004† |
| FA | −1.052 | 0.675 | .125 | −0.242 | 0.793 | .768 | 2.154 | 0.781 | .007† | |
| MD | 14.151 | 14.010 | .314 | −15.401 | 14.006 | .273 | −6.603 | 13.324 | .620 | |
Abbreviations: CC = corpus callosum; D-KEFS-TM = Delis-Kaplan Executive Function System Trail Making; FA = fractional anisotropy; IHWM = intrahemispheric white matter tracts; MD = mean diffusivity; ROI = region of interest; RT = radiation therapy; WAIS-IV = Weschler Adult Intelligence Scale IV.
Note: Processing speed was assessed via the D-KEFS-TM Number Sequencing and Letter Sequencing tests and the WAIS-IV Coding test. Models for each ROI and imaging parameter were created and analyzed independently. All volume models control for percentage of ROI censored. Significant results (P < .05) are shown in bold.
β estimate units are points/(mo*cm3) for volume; points/mo for FA, and points/(mo*μm2/ms) for MD.
Results that remained significant after corrections for multiple comparisons.