Investigation of age dependent contrast and t1 differences in MR images at 3.0 T: A study on MPRAGE, spin echo and flash protocols

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Enformatik Enstitüsü, Sağlık Bilişimi Anabilim Dalı, Türkiye

Tezin Onay Tarihi: 2013

Öğrenci: HAYRİYE AKTAŞ DİNÇER

Danışman: DİDEM GÖKÇAY

Özet:

During healthy aging, the brain undergoes several structural changes such as brain atrophy, decreased volume of GM and WM and increase in CSF volume. These changes introduce prominent low contrast effects to the MRI images of the aging population, causing segmentation problems in the data processing pipeline. Measures of tissue characteristics such as T1, T2 provide unique and complementary information to widely used measures of brain atrophy. In this study, image quality metrics such as contrast, SNR, CNR and GWR devised from 3 cortical and 2 sub-cortical regions of interest are used to evaluate the efficiency of MPRAGE and spin echo (SE) scans across ages. Multiple FLASH images are collected with varying flip angles for estimation of T1 within the GM areas in order to guarantee optimal TR values before the acquisition of SE images. While investigating the results of our parameter selection by calculations on MPRAGE and SE scans, we also utilized whole brain T1 images computed from multi-contrast FLASH images. As a result, we found that in terms of contrast and gray-white ratios (GWR), T1 estimated whole brain images are superior to MPRAGE and SE protocols, especially within sub-cortical areas. Furthermore, in T1 estimated whole brain images, degradation of contrast and GWR due to aging processes is observed to be less pronounced. In our comprehensive evaluation of MPRAGE, SE and FLASH images in young and aged healthy subjects, we observed that T1 estimations derived from FLASH images are useful for improving contrast and GWR.