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In vivo perfusion measurements in the human placenta using echo planar imaging at 0.5 T
Author(s) -
Gowland Penny A.,
Francis Susan T.,
Duncan Keith R.,
Freeman Alan J.,
Issa Bashar,
Moore Rachel J.,
Bowtell Richard W.,
Baker Philip N.,
Johnson Ian R.,
Worthington Brian S.
Publication year - 1998
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910400318
Subject(s) - perfusion , placenta , standard deviation , pulse sequence , in vivo , nuclear magnetic resonance , nuclear medicine , biomedical engineering , mathematics , physics , medicine , fetus , biology , cardiology , pregnancy , statistics , genetics , microbiology and biotechnology
This paper presents the first in vivo measurements of perfusion in the human placenta from 20 weeks gestational age until term, using the non‐selective/selective inversion recovery echo‐planar imaging sequence, in which data is alternately acquired following a selective and non‐selective inversion pulse. Twenty pairs of images were collected, two each at the following inversion times: 20, 310, 610, 910, 1110, 1410, 1910, 2810, 3310, and 4510 ms with the sequence being repeated with a repetition time (TR) of 10 s. The results of these measurements were used to suggest the optimum sequence for future work in terms of the signal to noise ratio in the measured perfusion rate in a given measurement time. The sequence was also analyzed to determine the expected variability in the measurements. In normal pregnancies the average value of perfusion rate was found to be 176 (standard error = ±24) ml/100 mg/min. ( n = 16, standard deviation = 96 ml/100 mg/min). The expected variability in the measured parameters due to signal to noise ratio considerations alone was calculated to be 71%. For a maximum scanning time of 400 s, the optimum sequence for measuring placental perfusion was found to require 8 repetitions at each of 10 inversion times which were geometrically spaced (given by a 0 a 0 r 0 a 0 r 2 a 0 r 3 ,…), with a 0 = 850 ms, r = 1.073 and TR = 5 s, giving a pixel variability of 38%. Other timing schemes are recommended for measuring perfusion in other anatomical regions with different values of perfusion rate and longitudinal relaxation time.