An in vivo NMR imaging determination of multiexponential Hahn T2 of normal lung

Abstract

We describe the first in vivo imaging determination of normal lung tissue's multiexponential transverse magnetization decay. Normal spontaneously breathing rats were used for the measurements. To obtain motion-insensitive images, we used a modified line scan imaging technique which we call the interleaved line scan (ILS). The ILS overcomes the following difficulties associated with imaging lungs: low signal-to-noise ratio (S/N) due to lung's low proton density and short T2 decay, artifacts associated with cardiac and respiratory motion, and excessively long imaging times with conventional line scan techniques. Using the ILS, a 16-line 32-average image with an 8-s repetition time requires 4.3 min. From a series of 16 Hahn spin-echo images with echo times ranging from 16 to 90 ms, we obtained a two-component T2 decay for normal peripheral lung tissue. The measured fast and slow T2 components were 9.5 +/- 1.0 and 34 +/- 5.0 ms for the right lung and 9.0 +/- 1.5 and 32 +/- 4.5 for the left lung. The relative magnetization for the slow T2 component was 7.0 +/- 4.5% for the right lung and 10 +/- 3.0% for the left lung.