## Abstract

T_{2} decay during long echo trains of magnetic resonance (MR) imaging pulse sequences is known to cause a blurring effect, due to the peak broadening of the point spread function (PSF). In contrast, the simultaneous amplitude-loss effect, led by the peak reduction of the PSF, has gained much less attention. In this report, we analyzed the PSFs of both the truncation and T_{2} decay for Cartesian (linear profile ordering and low-high ordering) and spiral trajectories, respectively. Then, we derived simple formulas to characterize both the blurring and amplitude-loss effects, which are functions of the ratios of the echo train duration (T_{k}) over T_{2} (T_{k}/T_{2}). Signal-to-noise ratio (SNR) per unit time was thus analyzed considering both the amplitude-loss effect induced by the T_{2} decay and the SNR gain from the long acquisition duration based on MR sampling theory. Optimum T_{k}/T_{2} ratios to achieve maximum SNR per unit time were 1.2 for the Cartesian trajectory and 0.8 for the spiral trajectory.

Original language | English (US) |
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Pages (from-to) | 1134-1142 |

Number of pages | 9 |

Journal | Magnetic Resonance Imaging |

Volume | 30 |

Issue number | 8 |

DOIs | |

State | Published - Oct 2012 |

## Keywords

- Cartesian
- K-space trajectory
- Point spread function
- SNR per unit time
- Spiral
- T decay

## ASJC Scopus subject areas

- Biophysics
- Biomedical Engineering
- Radiology Nuclear Medicine and imaging

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