title: Reinvestigating hyperpolarized (129)Xe longitudinal relaxation time in the rat brain with noise considerations.
abstract: The longitudinal relaxation time of hyperpolarized (HP) (129)Xe in the brain is a critical parameter for developing HP (129)Xe brain imaging and spectroscopy and optimizing the pulse sequences, especially in the case of cerebral blood flow measurements. Various studies have produced widely varying estimates of HP (129)Xe T(1) in the rat brain. To make improved measurements of HP (129)Xe T(1) in the rat brain and investigate how low signal-to-noise ratio (SNR) contributes to these discrepancies, we developed a multi-pulse protocol during the washout of (129)Xe from the brain. Afterwards, we applied an SNR threshold theory to both the multi-pulse protocol and an existing two-pulse protocol. The two protocols yielded mean +/- SD HP (129)Xe T(1) values in the rat brain of 15.3 +/- 1.2 and 16.2 +/- 0.9 s, suggesting that the low SNR might be a key reason for the wide range of T(1) values published in the literature, a problem that might be easily alleviated by taking SNR levels into account.
authors.affiliation: Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA. dr.xin.zhou@gmail.com
authors.forename: X
authors.initials: X
authors.lastname: Zhou
authors.forename: M L
authors.initials: ML
authors.lastname: Mazzanti
authors.forename: J J
authors.initials: JJ
authors.lastname: Chen
authors.forename: Y-S
authors.initials: YS
authors.lastname: Tzeng
authors.forename: J K
authors.initials: JK
authors.lastname: Mansour
authors.forename: J D
authors.initials: JD
authors.lastname: Gereige
authors.forename: A K
authors.initials: AK
authors.lastname: Venkatesh
authors.forename: Y
authors.initials: Y
authors.lastname: Sun
authors.forename: R V
authors.initials: RV
authors.lastname: Mulkern
authors.forename: M S
authors.initials: MS
authors.lastname: Albert
mesh_terms: D000818:Animals; D001921:Brain / Q000033:anatomy & histology / Q000378:metabolism*; D007091:Image Processing, Computer-Assisted; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008433:Mathematics; D051381:Rats; D017207:Rats, Sprague-Dawley; D014979:Xenon Isotopes / Q000378:metabolism*
chemical_list: D014979:Xenon Isotopes