Non-invasive study of human gall bladder bile in vivo using (1)H-MR spectroscopy.

The sampling of gall bladder bile for analytical studies remains an invasive procedure. We demon- strate the application of the non-invasive methodology of 1 H-MR spectroscopy to the qualitative and quanti- tative assessment of human gall bladder bile in vivo. Spectral profiles in vivo are shown in relation to model and porcine gall bladder bile and the quantitation in man of the trimethylamine (choline) and lecithin concentrations were estimated to range from 25.9 mM to 48.4 mM (mean: 35.8 mM, standard deviation: 9.8). The composition of human gall bladder bile together with the quantitation of various constituents can be studied non-invasively in vivo. The techniques currently available for sampling chole- dochal or gall bladder (GB) bile in humans remain invasive (1). In addition, biliary sampling via choledochal surgical access has diminished considerably since the widespread introduction of endoscopic techniques, whilst serial peri- operative sampling of normal GB bile carries considerable ethical and practical restrictions. Nevertheless, the com- position of GB bile remains an important determinant of biliary lithogenicity (2), while many classes of drug undergo significant biliary excretion (3). The development of a non- invasive methodology capable of interrogating the com- position of bile in vivo would therefore be of considerable clinical and scientific benefit. In a previous publication we demonstrated the in vivo localization of the bile-acid con- jugate of a-fluoro-b-alanine in the GB of patients receiving the anti-cancer agent 5-fluorouracil using 19 F-MR spectr- oscopy (MRS) (4). 1 H-MRS on the other hand remains to be developed and applied to the study of GB bile other than for in vitro analytic studies (5, 6). The aim of the present study was to qualitatively and quantitatively assess the available 1 H-MR spectra from in vivo human GB bile. Materials and methods 10 healthy male volunteers (mean age: 31.2 years, range: 24-47 years), fasted overnight, were studied using a 1.5 T Siemens (Erlangen, Germany) Vision system using a 16 cm receive surface coil placed over the surface-markings of the GB. The GB was localized using a T2 weighted image. A PRESS (point-resolved spectroscopy) sequence with echo time (TE)560 ms and repetition time (TR)52500 ms was used after automatically shimming the volume of the right upper quadrant to between 6 Hz and 25 Hz. The shortest echo-time available to the sequence (TE560 ms) was chosen to maintain the signal from short T2 metabolites. A total of 128 individual signal acquisitions were acquired in each study. In addition, an unsuppressed water signal was acquired with four averages from the target voxel. In half the volunteers the exact same sequence was run with the voxel placed within the liver. This was done in order to assess whether there might be spectral hepatic metabolite