Ferrite-enhanced MR imaging of hepatic lymphoma: an experimental study in rats

The purpose of this investigation was to define the potential of unenhanced and ferrite-enhanced MR to detect hepatic lymphoma. Rats were implanted with diffuse and focal hepatic lymphoma. Both in vitro measurements of relaxation times and in vivo MR imaging of normal liver and of diffuse and focal hepatic lymphoma were compared. Diffuse infiltrative hepatic lymphoma showed increased T1 (45%) and T2 (41%) relaxation times in vitro, but could not be distinguished from normal control livers on in vivo spin echo (SE) images with a repetition time of 500 msec and an echo time of 30 msec (SE 500/30) or SE 1500/60 images. Focal hepatic lymphoma showed increased T1 (185%) and T2 (115%) relaxation times relative to normal liver tissue. Focal hepatic lymphoma was undetectable on unenhanced SE 500/30 MR images (contrast-to-noise ratio, C/N = 0.4) and was slightly hyperintense on SE 1500/60 images (C/N = 1.1). Ferrite (50 mumol Fe/kg) was administered to improve tissue contrast. In normal control animals, T2 of liver in vitro decreased from 29.3 +/- 3.3 msec to 11.1 +/- 1.2 msec, and image signal-to-noise ratio (S/N) of liver in vivo decreased from 16.1 +/- 2.4 to 2.8 +/- 0.3 (p less than .005). Ferrite-enhanced diffuse hepatic lymphoma showed in vitro T2 values and in vivo MR image S/N values indistinguishable from those of normal control animals. The T2 of focal hepatic lymphoma was essentially unaltered by ferrite. On SE 500/30 images, focal hepatic lymphoma became readily detectable, quantitated by a 35-fold increase in tumor-liver C/N. We conclude that clinical studies are warranted to determine the value of ferrite enhanced MR as a technique for the enhanced detection of focal hepatic lymphoma.