Molinari Francesco, Madhuranthakam Ananth J, Lenkinski Robert, Bankier Alexander A
From the Department of Radiology (F.M. e-mail:
Diagn Interv Radiol. 2014 Jan-Feb;20(1):34-41. doi: 10.5152/dir.2013.13232.
We aimed to develop a predictive model for lung water content using ultrashort echo time (UTE) magnetic resonance imaging (MRI) and a sponge phantom.
Image quality was preliminarily optimized, and the signal-to-noise ratio (SNR) of UTE was compared with that obtained from a three-dimensional fast gradient echo (FGRE) sequence. Four predetermined volumes of water (3.5, 3.0, 2.5, and 2.0 mL) were soaked in cellulose foam sponges 1.8 cm3 in size and were imaged with UTE-MRI at 1.5 and 3.0 Tesla (T). A multiple echo time experiment (range, 0.1-9.6 ms) was conducted, and the T2 signal decay curve was determined at each volume of water. A three-parameter equation was fitted to the measured signal, allowing for the calculation of proton density and T2*. The calculation error of proton density was determined as a function of echo time. The constants that allowed for the determination of unknown volumes of water from the measured proton density were calculated using linear regression.
UTE-MRI provided excellent image quality for the four phantoms and showed a higher SNR, compared to that of FGRE. Proton density decreased proportionally with the decreases in both lung water and field strength (from 3.5 to 2.0 mL; proton density range at 1.5 T, 30.5-17.3; at 3.0 T, 84.2-41.5). Minimum echo time less than 0.6 ms at 1.5 T and 1 ms at 3.0 T maintained calculation errors for proton density within the range of 0%-10%. The slopes of the lines for determining the unknown volumes of water with UTE-MRI were 0.12±0.003 at 1.5 T and 0.05±0.002 at 3.0 T (P < 0.0001).
In a sponge phantom imaged at 1.5 and 3.0 T, unknown volumes of water can be predicted with high accuracy using UTE-MRI.
我们旨在利用超短回波时间（UTE）磁共振成像（MRI）和海绵体模开发一种预测肺含水量的模型。
对图像质量进行初步优化，并将UTE的信噪比（SNR）与三维快速梯度回波（FGRE）序列获得的信噪比进行比较。将四个预定体积的水（3.5、3.0、2.5和2.0 mL）浸泡在尺寸为1.8 cm³的纤维素泡沫海绵中，并在1.5和3.0特斯拉（T）下用UTE-MRI进行成像。进行了多回波时间实验（范围为0.1 - 9.6 ms），并确定了每个水体积下的T2信号衰减曲线。将一个三参数方程拟合到测量信号上，从而计算质子密度和T2*。确定质子密度的计算误差作为回波时间的函数。使用线性回归计算从测量的质子密度确定未知水体积所需的常数。
UTE-MRI为四个体模提供了出色的图像质量，并且与FGRE相比显示出更高的SNR。质子密度随着肺含水量和场强的降低而成比例下降（从3.5降至2.0 mL；1.5 T时质子密度范围为30.5 - 17.3；3.0 T时为84.2 - 41.5）。1.5 T时最小回波时间小于0.6 ms，3.0 T时小于1 ms可将质子密度的计算误差保持在0% - 10%范围内。使用UTE-MRI确定未知水体积的直线斜率在1.5 T时为0.12±0.003，在3.0 T时为0.05±0.002（P < 0.0001）。
在1.5和3.0 T成像的海绵体模中，使用UTE-MRI可以高精度预测未知体积的水。
