title: Performance of sampling density-weighted and postfiltered density-adapted projection reconstruction in sodium magnetic resonance imaging.
abstract: Sampling density-weighted apodization projection reconstruction sequences are evaluated for three-dimensional radial imaging. The readout gradients of the sampling density-weighted apodization sequence are designed such that the locally averaged sampling density matches a Hamming filter function. This technique is compared with density-adapted projection reconstruction with nonfiltered and postfiltered image reconstruction. Sampling density-weighted apodization theoretically allows for a 1.28-fold higher signal-to-noise ratio compared with postfiltered density-adapted projection reconstruction sequences, if T(2)* decay is negligible compared with the readout duration T(RO). Simulations of the point-spread functions are performed for monoexponential and biexponential decay to investigate the effects of T(2)* decay on the performance of the different sequences. Postfiltered density-adapted projection reconstruction performs superior to sampling density-weighted apodization for large T(RO)/T(2)* ratios [>1.36 (monoexponential decay); >0.35 (biexponential decay with T(2s)*/T(2f)* = 10)], if signal-to-noise ratio of point-like objects is considered. In conclusion, it depends on the readout parameters, the T(2)* relaxation times, and the dimensions of the subject which of both sequences is most suitable.
authors.affiliation: Computer Assisted Clinical Medicine, Heidelberg University, Mannheim, Germany.
authors.forename: Simon
authors.initials: S
authors.lastname: Konstandin
authors.forename: Armin M
authors.initials: AM
authors.lastname: Nagel
mesh_terms: D000465:Algorithms; D001921:Brain / Q000033:anatomy & histology*; D003287:Contrast Media; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015203:Reproducibility of Results; D018401:Sample Size; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D012964:Sodium
chemical_list: D003287:Contrast Media; D012964:Sodium