RESUMO
Objective To discuss the application of enhanced CT subtraction technique in evaluating residual hepatocelluar carcinoma activity after transcatheter arterial chemoembolization (TACE).Methods A total of consecutive 22 patients with clinically-confirmed hepatocellular carcinoma (HCC),who received TACE,were retrospectively collected.Multi-phase enhanced CT examination of liver was performed in all patients after the initial TACE,and the presence or absence of residual active tumor was determined at the second time of TACE.The enhanced arterial phase CT images were used to subtract the corresponding plain scan images,and the subtraction images were thus obtained.The post-subtraction CT values of the lesions that showed iodine oil deposit were measured,which were compared with angiography findings performed at the second time of TACE.The residual tumor activity indicated by post-subtraction images was statistically analyzed.Results In 22 HCC patients receiving TACE,a total of 37 lesions showed iodine oil deposit after the initial TACE.Assessment of tumor activity indicated that 34 lesions had tumor activity and 3 lesions had no tumor activity.The mean post-subtraction CT value of the lesions in the tumor activity group was (79±68) HU,while it was (1 ±1) HU in the tumor non-activity group;the difference between the two groups was statistically significant (P=0.007).Analysis with receiver operating characteristic (ROC) curve indicated that when the post-subtraction CT value of the lesion was greater than one HU,the sensitivity and specificity for diagnosing residual tumor were 97.06％ and 100％ respectively,and the area under the ROC curve was up to 0.975.Conclusion The subtraction images obtained by subtracting the enhanced arterial phase CT images from the plain scan images can accurately and intuitively determine the presence or absence of residual active HCC lesions after TACE.