99m Tc-methoxyisobutyl isonitrile(MIBI) is a suitable transport substrate for the multidrug resistance gene product P-glycoprotein(P-gp) and widely used for tumor imaging.Bromocriptine has been shown to inhibit the ATPase activity and the function of P-gp.We hypothesized that bromocriptine could promote the accumulation of MIBI by inhibiting P-gp activities,a feature that can be taken advantage of for enhancing 99mTc-MIBI imaging.In the current study,we sought to investigate whether bromocriptine enhanced the uptake of 99mTc-MIBI in hepatocellular carcinoma patients.Sixty primary hepatocellular carcinoma patients received 99mTc-MIBI single photon emission computer tomgraphy(SPECT) prior to surgery.99mTc-MIBI SPECT was performed 15 and 120 min after injection of 20 mCi 99mTc-MIBI,and early uptake,delayed uptake(L/Nd),and washout rate(L/Nwr) of 99mTc-MIBI were obtained.In addition,a second 99mTc-MIBI SPECT was performed according to the same method 48 h after bromocriptine administration.We found that,prior to bromocriptine administration,significant MIBI uptake in tumor lesions was noted in only 10(16.7%,10/60) patients with hepatocellular carcinoma.No significant MIBI uptake was observed in the tumor lesions of the remaining 50(83.3%,50/60) hepatocellular carcinoma patients.Following bromocriptine administration,all the patients without apparent MIBI uptake demonstrated significant MIBI uptake on 99mTc-MIBI SPECT(P < 0.05).Our findings indicate that bromocriptine enhances the uptake of 99m Tc-MIBI in patients with hepatocellular carcinoma. 99m Tc-methoxyisobutyl isonitrile (MIBI) is a suitable transport substrate for the multidrug resistance gene product P-glycoprotein (P-gp) and widely used for tumor imaging. Briocriptine has been shown to inhibit the ATPase activity and the function of P-gp We hypothesized that bromocriptine could promote the accumulation of MIBI by inhibiting P-gp activities, a feature that can be taken advantage of for 99mTc-MIBI imaging. The current study, we sought to investigate whether bromocriptine enhanced the uptake of 99mTc- MIBI in hepatocellular carcinoma patients. 99mTc-MIBI single photon emission computer tomography (SPECT) prior to surgery. 99mTc-MIBI SPECT was performed 15 and 120 min after injection of 20 mCi 99mTc-MIBI, and early uptake, delayed uptake (L / Nd), and washout rate (L / Nwr) of 99mTc-MIBI were obtained. In addition, a second 99mTc- MIBI SPECT was performed according to the same method for 48 h after bromocriptine administration We found that, prior to bromocriptine administration, significant MIBI uptake in tumor lesions was noted in only 10 (16.7%, 10/60) patients with hepatocellular carcinoma. No significant MIBI uptake was observed in the tumor lesions of the remaining 50 (83.3 % Of 50/60) hepatocellular carcinoma patients. After bromocriptine administration, all the patients without apparent MIBI uptake of significant MIBI uptake on 99mTc-MIBI SPECT (P <0.05). These results indicate that bromocriptine enhances the uptake of 99m Tc-MIBI in patients with hepatocellular carcinoma.