CONTRAST-ENHANCED MR-IMAGING OF DIFFUSE AND FOCAL SPLENIC DISEASE WITH USE OF MAGNETIC STARCH MICROSPHERES

The diagnostic value of magnetic starch microspheres (MSM), a new supe rparamagnetic contrast agent, was studied in experimental models of di ffuse and focal splenic disease in rats by means of ex vivo relaxometr y and in vivo magnetic resonance (MR) imaging. Owing to small differen ces in unenhanced T1 and T2 values between diffuse lymphoma and normal spleen, MR imaging failed to distinguish tumor-bearing animals from c ontrol animals by signal-to-noise ratios (SNRs) obtained with T1- and T2-weighted spin-echo sequences. One hour after injection of 20 mumol/ kg MSM, lymphomatous spleen showed significantly (P < .001) reduced en hancement relative to normal splenic tissue. As a result, animals with diffuse lymphoma (SNR: 10.3 +/- 1.7) could be easily differentiated f rom control animals (SNR: 5.5 +/- 0.6) on T2-weighted (TR msec/TE msec = 2,000/45) images. In focal splenic disease, MSM produced normal enh ancement of nontumorous splenic tissue, whereas relaxation times of tu mors were not different before and after contrast agent injection. On T2-weighted images (2,000/45), the tumor-spleen contrast-to-noise rati o increased from 4.8 +/- 1.6 to 21.8 +/- 1.9 (+354%). improving conspi cuity of splenic tumors. The results show that MSM-enhanced MR imaging improves the detection of diffuse and focal splenic disease.