Scholarly Publications - UMRAM

Permanent URI for this collectionhttps://hdl.handle.net/11693/115674

Browse

Browsing Scholarly Publications - UMRAM by Author "Açıkel, Volkan"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    Decreasing SAR of a multi-dimensional central brightening inhomogeneity correction pulse using nonlinear gradient fields and VERSE
    (ISMRM, 2012-05) Kopanoğlu, Emre; Gökhalk, Yıldıray; Yılmaz, Uğur; Açıkel, Volkan; Atalar, Ergin
    To correct for B1 inhomogeneity artifacts, multi-dimensional pulses are widely used. However, such pulses increase SAR significantly. In this study, we compare, and combine two SAR reduction methods, the variable rate selective excitation and excitation using nonlinear gradient fields in order to observe their effect on SAR. 5-spoke pulses are designed for both methods to correct for a central brightening inhomogeneity, which is widely seen at the UHF regime. When two methods are used separately, SAR reductions around 75% were obtained whereas when combined, the methods yielded an SAR reduction of 91%.
  • Thumbnail Image
    ItemOpen Access
    Localizing the excitation to reduce scan time using nonlinear gradient fields
    (ISMRM, 2012) Kopanoğlu, Emre; Yılmaz, Uğur; Akın, Burak; Açıkel, Volkan; Atalar, Ergin
    elatively low SAR, but they cannot excite local regions and therefore causes long scan times. Although small volumes can be excited using multi-dimensional excitation pulses, such pulses are long and/or have relatively high SAR. It is shown that, using gradient fields with nonlinear variation in space, excitation regions can be confined in three dimensions without increasing pulse duration and SAR. In this abstract we show that a 60% decrease in required phase-encoding steps is obtained while imaging the occipital lobe of the brain. Initial in-vivo results are presented.