Whole brain quantitative T2 MRI across multiple scanners with dual echo FSE: applications to AD, MCI, and normal aging

Abstract

The ability to pool data from multiple MRI scanners is becoming increasingly important with the influx in multi-site research studies. Fast spin echo (FSE) dual spin echo sequences are often chosen for such studies based principally on their short acquisition time and the clinically useful contrasts they provide for assessing gross pathology. The practicality of measuring FSE-T2 relaxation properties has rarely been assessed. Here, FSE-T2 relaxation properties are examined across the three main scanner vendors (General Electric (GE), Philips, and Siemens). The American College of Radiology (ACR) phantom was scanned on four 1.5T platforms (two GE, one Philips, and one Siemens) to determine if the dual echo pulse sequence is susceptible to vendor-based variance. In addition, data from 85 subjects spanning the spectrum of normal aging, mild cognitive impairment (MCI), and Alzheimer's disease (AD) was obtained from the Alzheimer's Disease Neuroimaging Initiative (ADNI) to affirm the presence of any phantom based between vendor variance and determine the relationship between this variance and disease. FSE-T2 relaxation properties, including peak FSE-T2 and histogram width, were calculated for each phantom and human subject. Direct correspondence was found between the phantom and human subject data. Peak FSE-T2 of Siemens scanners was consistently at least 20ms prolonged compared to GE and Philips. Siemens scanners showed broader FSE-T2 histograms than the other scanners. Greater variance was observed across GE scanners than either Philips or Siemens. FSE-T2 differences were much greater with scanner vendor than between diagnostic groups, as no significant changes in peak FSE-T2 or histogram width between normal aged, MCI, and AD subject groups were observed. These results indicate that whole brain histogram measures are not sensitive enough to detect FSE-T2 changes between normal aging, MCI, and AD and that FSE-T2 is highly variable across scanner vendors.

Figure 1

Flow chart showing the post-processing data analysis used to obtain histograms from the directly-acquired images.

Figure 2

Representative T2 quantitative MR maps. a) T2 map of a 79 year old male control subject on a GE Signa Excite platform. b) T2 map of a 77 year old female subject with MCI scanned on a Siemens Sonata platform. c) Shows a T2 map from a 75 year old male AD subject scanned with a Siemens Avanto platform.

Figure 3

Representative example of segmented brain tissue using a dual-clustering segmentation algorithm. a) The brain tissue included in the segmentation is represented in the highlighted region. b) Segmented brain.

Figure 4

ICM T2 histograms from all subjects and scanner platforms, a) Philips b) GE c) Siemens.

Figure 5

Quantitative ICM T2 histogram averaged within scanner vendor: Philips, GE, and Siemens. The slight bimodal nature of the GE curve represents those subjects from site 005, which had average values approximately 20 ms lower than other GE sites. a) Normal control subjects: Philips and GE peak at 97.35 and 98.37 while Siemens peaks at 119.69ms. The width of the spectrum is approximately 50.6 for Philips, GE, and Siemens respectively. b) MCI subjects: Philips peak T2 = 94.29ms, GE peak = 99.38ms, while Siemens peaks at 119.09ms. The width of the spectrum is 52, 53, and 55 units for Philips, GE, and Siemens respectively. c) AD subjects: Philips peak = 95.68ms, GE peak = 102.08, and Siemens peak = 116.75ms. The width of the spectrum is 51, 53, and 54 for Philips, GE, and Siemens respectively.