In vivo¹H MRS of human gallbladder bile at 3 T in one and two dimensions: detection and quantification of major biliary lipids

Abstract

In vitro1 H MRS of human bile has shown potential in the diagnosis of various hepatopancreatobiliary (HPB) diseases. Previously, in vivo 1 H MRS of human bile in gallbladder using a 1.5 T scanner demonstrated the possibility of quantification of choline-containing phospholipids (chol-PLs). However, other lipid components such as bile acids play an important role in the pathophysiology of the HPB system. We have employed a higher magnetic field strength (3 T), and a custom-built receive array coil, to improve the quality of in vivo 1 H MRS of human bile in the gallbladder. We obtained significant improvement in the quality of 1D spectra (17 healthy volunteers) using a respiratory-gated PRESS sequence with well distinguished signals for total bile acids (TBAs) plus cholesterol resonating at 0.66 ppm, taurine-conjugated bile acids (TCBAs) at 3.08 ppm, chol-PLs at 3.22 ppm, glycineconjugated bile acids (GCBAs) at 3.74 ppm, and the amide proton (ÀNH) arising from GCBAs and TCBAs in the region 7.76-8.05 ppm. The peak areas of these signals were measured by deconvolution, and subsequently the molar concentrations of metabolites were estimated with good accuracy, except for that of TBAs plus cholesterol. The concentration of TBAs plus cholesterol was overestimated in some cases, which could be due to lipid contamination. In addition, we report the first 2D L-COSY spectra of human gallbladder bile in vivo (obtained in 15 healthy volunteers). 2D L-COSY spectra will be helpful in differentiating various biliary chol-PLs in pathological conditions of the HPB system.

In vivo 1H MRS of human gallbladder bile in understanding the pathophysiology of primary sclerosing cholangitis (PSC): Immune‐mediated disease versus bile acid‐induced injury

“…In order to achieve a comparable quality, the bandwidth of water suppression pulse was increased to 50 Hz on VB 17. The increase in bandwidth did not affect any of the peaks of interest …”

“…Seven patients had inflammatory bowel disease (IBD) and one patient had already developed cirrhosis. 1D spectra from 14 healthy volunteers who were recruited for our recent study (11 females and 3 males, mean ages 40 and 33 years respectively, range 21–55 years) were included as control datasets. The healthy volunteers had no history of chronic liver disease or IBD.…”

“…The remaining 6/11 patients were composed of three females and three males (mean ages 43 and 36 years respectively, range 24–48 years). After applying the same exclusion criteria as above, 11 2D L‐COSY spectra from our recent study on healthy volunteers were also included as a control group. The healthy volunteers included in the study were seven females and four males (mean ages 41 and 35 years respectively, range 26–55 years).…”

“…We also acquired 2D L‐COSY spectra using the sequence edited from Siemens PRESS as described by Thomas et al According to this method, we replaced the last 180° refocusing pulse of the PRESS sequence by a hyperbolic secant 90°, the same as the first 90° excitation RF pulse. We applied a 0.8 ms time increment (Δ t 1 ) between the first refocusing and the second 90° (coherence transfer) RF pulse in each measurement . In order to minimize lipid contamination, in both 1D and 2D experiments, we optimized the voxel size to 12 × 12 × 12 mm 3 and positioned six to eight spatial saturation bands around the gallbladder.…”

“…This might have been due to the use of low magnetic field strength (1.5 T), long delays ( T E = 60 ms), and/or lipid contamination. Later, Künnecke et al were successful in obtaining a good quality spectrum of bile in vivo in cynomolgus monkeys by increasing the magnetic field strength from 1.5 T to 4.7 T. Recently, we were able to obtain high quality in vivo 1 H spectra non‐invasively from gallbladder bile in healthy volunteers using a 3 T scanner and a custom‐built receive array coil . We were able to detect and quantify major biliary lipids: total bile acids (TBAs) plus cholesterol (0.66 ppm), TCBAs (3.08 ppm), chol‐PLs (3.22 ppm), GCBAs (3.74 ppm), and the sum of TCBAs and GCBAs as determined from the amide proton region (7.76–8.05 ppm).…”