Abstract

Purpose: To quantify baseline relaxation rates R-2(*) and R-1 in the abdomen, their changes after respiratory challenges, and their reproducibility in healthy volunteers and patients with hepatocellular carcinoma (HCC) at 1.5T and 3.0T. Materials and Methods: R-2(*) measurements were acquired in the liver in 8 volunteers and 27 patients with 34 HCCs using multiecho T-2(*) at baseline and after respiratory challenges with 100% oxygen (O-2) and carbogen (CB=95%O-2/5%CO2). R-1 was measured at 1.5T in one volunteer and 21 patients with 23 HCCs. Test-retest coefficient of variation (CV) was assessed in 10 subjects. Intra- and interobserver variability of R-2(*) and R-1 measurements was assessed in 12 and 10 patients, respectively. Parameters for HCC, liver, and muscle were compared between baseline and after gas challenges. Results: We observed that R-2(*) and R-1 imaging of HCCs with O-2 and CB is feasible and reproducible (test-retest CV R-2(*)15%/R-15%; intra- and interobserver intraclass correlation coefficient R-2(*)>0.88/R-1>0.7 and CV R-2(*)7%/R-13% at 1.5T). measurements were observed to be less reproducible at 3.0T (CV35%). There was a statistically significant decrease in R-2(*) values in HCC before and after O-2 (P=0.02) and increase in R-1 after O-2 (P=0.004). CB had no significant effect (P R-2(*)=0.47/R-1=0.278). Conclusion: R-2(*) measurements in HCC and liver parenchyma are more reproducible at 1.5T than at 3.0T, and with O-2 than with CB challenge. We observed a decrease in R-2(*) and an increase in R-1 of HCCs from baseline in response to O-2 challenge, as expected with increased tissue and blood oxygenation.