Table 3.
Methodological Issues of Longitudinal MRI Studies
| Study Reference | Areas Assessed | Methods of Measurement | Imaging Techniques |
| Frazier et al25,51 | Lateral ventricle volume, basal ganglia (caudate, putamen, and globus pallidus) volume | Automated procedure (lateral ventricular vol), mouse-driven tracing tool (basal ganglia) | 1.5-T scannera, ROI analyses |
| Rapoport et al23 | Total cerebral volume, lateral ventricle volume, ventricle/brain ratio, basal ganglia (caudate, putamen, and globus pallidus), and midsagittal thalamic area | Automated procedure (lateral ventricular vol), mouse-driven tracing tool (basal ganglia), and manual outlining (midsagittal thalamic area) | 1.5-T scannera, ROI analyses |
| Rapoport et al18 | Regional cortical (temporal, frontal, parietal, and occipital) GM and WM volume | Automated procedure separates GM, WM, and CSF and separates cortex into anatomically defined lobar regions | 1.5-T scannera, ROI analyses |
| Thompson et al19 | Cortical GM volume | Automated procedure separates cortical GM, WM, and CSF | 1.5-T scannera, generation of brain mapping algorithms (dynamic cortical mapping)b |
| Keller et al24 | Total cerebral volume, cerebellar volume (total, R, and L), vermal midsagittal area, and posterior-inferior vermal volume | Automated procedure (total cerebral and cerebellar volumes) and manual outlining (midsagittal vermal area and posterior inferior vermal lobe) | 1.5-T scannera, analysis of longitudinal data from all available scans (108 scans from 50 patients and 101 scans from 50 controls) with polynomial growth models, ROI analyses |
| Sporn et al22 | Total cerebral volume, total and regional (F, P, T) GM volume, and ventricular volume | Automated procedure separates GM, WM, and CSF and separates cortex into lobar regions | 1.5-T scannera, analysis of longitudinal data from all available scans (131 scans from 60 patients and 140 scans from 64 controls) with polynomial growth models, ROI analyses |
| Gogtay et al7,38 | Total cerebral volume and total and regional (F, P, T, O) GM volume | Automated procedure separates GM, WM, and CSF and separates cortex into lobar regions | 1.5-T scannera, ROI analyses |
| Vidal et al41 | Interhemispheric medial cortical surface | Automated method generates maps of cortical GM, WM, and CSF | 1.5-T scannera, generation of brain mapping algorithms (dynamic cortical mapping)b |
| Greenstein et al26 | Cortical regions (except R and L insula, R cuneus, and R parahippocampus) | Automated method measures cortical thickness at 40 962 points across the cerebral hemispheres | 1.5-T scannera, analysis of longitudinal data from all available scans (162 scans from 70 patients and 168 scans from 72 controls) with mixed model regression; ROI analyses |
| Nugent et al27 | Hippocampi (R, L, and subregional level) | Manual outlining by a single individual. Anatomical mesh modeling methods to match equivalent surface points across subjects. | 1.5-T scannera, generation of ratio maps at each age (dynamic sequence)c |
| James et al37 | Total brain, cerebral volume, cerebellar volume, lateral ventricle (L, R), third ventricular volume, fourth ventricular volume, temporal WM (L, R), temporal horn (L, R), temporal lobe (L, R), hippocampues (L, R), and amygdala (L, R) | Manual outlining, hierarchical semiautomated method of segmentation of GM and WM in the temporal lobes | 1,5-T scanner, ROI analyses |
| James et al36 | Total brain volume, prefrontal cortex volume, cerebellum volume, thalamus volume, vermis volume, and fourth ventricle volume | Manual outlining | 1.5-T scanner, ROI analyses |
| S. Reig, C. Moreno, D. Moreno, M. Burdalo, J. Janssen, M. Parellada, A. Zabala, M. Desco, C. Arango, submitted | Total intracranial volume, total and regional (F, P, T, O) GM volume, total and regional (F, P, T, O) CSF volume, and total WM volume | Semiautomated segmentation | 1.5-T scanner, ROI analyses |
Note: ROI, region of interest; R, right; L, left; WM, white matter; CSF, cerebrospinal fluid; F, frontal; T, temporal; P, parietal; O, occipital.
All scans obtained with the same 1.5-T scanner.
The 3-dimensional distribution of GM in the brain was computed from one scan to the next with a computational cortical pattern matching strategy that aligns corresponding locations on the cortical surface across time and across subjects. A local measurement of GM density was made in each subject and averaged across equivalent cortical locations. This procedure allows to pool maps of individual GM loss over time.
Ratio maps at each age obtained by dividing the average hippocampal size of patients at a given age at each hippocampal point by the size at the corresponding hippocampal point of the control group at the matched age. Mixed model regression analyses at each of 30 000 hippocampal points were used to test for differences in longitudinal hippocampal development in patients vs controls.