The Differentiation Characterization Of Arterial Phase Perfusion Of Focal Liver Lesions On Contrast-enhanced Ultrasound And Contrast-enhanced CT

Study background: As the preferred method of examination, ultrasoud has many advantages in focal liver lesions(FLL) screening. For example Non-invasive, economic, efficient and so on. However, because of the lack of enhanced information,ultrasound is slightly inferior to contrast-enhanced computed tomography (CECT) in the qualitative diagnosis of liver tumors. The diagnostic and differential diagosis capability of CECT is based on the vascularity and enhancement pattern within the lesion, it is mature in the application of FLL. As an emerging technology, real-time contrast-enhanced ultrasound (CEUS) allows the continuous assessment of tumor vascularity and enhancement during the different vascular phases with better image contrast resolution. All of those advantages greatly improve the sensitivity and specificity of CEUS. So we can say, the emergence of CEUS opens up new area for the diagnosis of FLL, and this is a leap forward in the field of Ultrasound. At present, CEUS has made remarkable achievements in the diagnostic performance of FLL. In clinical practice, CECT remains the major method in the differential diagnosis of FLL. The comparison of the two methods mostly focus on specificity,sensibility and accuracy, and the research of the subtle difference of enhanced features in all enhanced phases is less. In this paper, we will make a comparision of CEUS and CECT in the differential diagnosis of FLL.Objective: To observe the perfusion process of FLL on CEUS and CECT, especially in arterial phase. To recommend the primary examination for different liver disease by comparing the enhanced time and enhanced features of the focal liver lesions in the arterial phase on CEUS and CECT,Material and Method:22patients (31 lesions) who were admitted to our hospital because of the FLL were examined with contrast-enhanced ultrasound and contrast-enhanced CT.Liver has hepatic artery (25~30%) and portal vein (70~75%) dual blood supply. CEUS can define and observe the three overlapping vascular phase. According to the state of individual cycle, the real-time CEUS can be divided into three phases: (1) arterial phase (0～35s, 0～25s as the early arterial phase, 25～35s as the late arterial phase); (2) portal phase (35～120s); (3) late phase (after 120s). The CECT also can be divided into three phases: (1) arterial phase (around 25s after intravenous injection of contrast agent ), (2) portal phase (70s after intravenous injection of contrast agent), (3) balance phase (120～180s).CEUS: The CEUS examinations were performed with 2～5 MHz convex transducer and 0.06～0.08 mechanical index (iU22, Philips), and CEUS with contrast pulse sequence imaging was performed. The contrast agent of CEUS is SonoVue, dissolving the agent with 5ml saline and shaking it into suspension for ready. Firstly, the entire liver was scanned with gray-scale imaging. The location, size, boundary and internal echo of lesions were observed. Secondly, The Color Doppler was used to observe the blood flow of the lesions. Finally, Switch to CEUS, SonoVue was injected intravenously as a bolus of 2.4 ml, followed by a flush of 5 ml nomorl saline solution. the enhancement level, enhancement modality and the changes in different phases were observed. The enhancement time (arrive time, peak time) and enhanced features of early arterial phase were focused on. All sequences were recorded and stored digitally. Intratumoral vascular geometry and enhancement pattern of the lesions were described, and compared with CECT. Note: The arterial phase of CECT is in the 25s or so. So we regard 0～25s as the early arterial phase.CECT: All patients received the examination with CT(16-slice, GE), Enhanced scanning after the first scanning. The arterial phase scanning began at 25 s after 80-90 ml Iohexol, an iodinated contrast, was high-pressured injected at a flow rate of 3 ml/s, followed by a portal venous phase sequence beginning at 70 s after contrast infusion, and the balance phase sequence was obtained at 120～180s, late phase(after 4min). The enhancement pattern was recorded and stored digitally.Because the enhancement patterns of CEUS and CECT are based on the blood supply. The more blood supply, the more enhancement. So the imaging features were compared and classified into four grades separately(0～3grades):0grade, non-enhancing; 1 grade, peripheral enhancement or a little central enhancement; 2 grade, spoke-wheel enhancement,honey comb-like enhancement,heterogeneous enhancement; 3 grade, complete enhancement.All the data obtained were analyzed by SPSS13.0 software, X2 test was used to Compare the difference between count datas, P<0.05 was considered as statistically significant difference。Results:1. On CEUS, there were 30 lesions (96.77%)out of 31 lesions whose arriving time was less than 25 s, and there were 25 lesions(80.65%)whose peaking time was less than 25 s.2. The number of 2～3 grade flow lesions on CEUS was 21 lesions(67.74%), and the number on CECT was 9 lesions(29.03%). In statistically , the comparison between the two examinations was significantly difference.3. In 31 lesions, there were 6 lesions which the CEUS diagnosised correctly but the CECT did not. The arriving times of all the 6 lesions were less than 25 s, and there were 5 lesions whose peaking times were less than 25 s.4. In 31 lesions, there were 3 lesions which the CECT diagnosised correctly but the CEUS did not. 2 HCC lesions were at the background of cirrhosis, 1 hepatic hemangioma was at the top diaphragm of the severe fatty liver. On two-dimensional ultrasound, all the 3 lesions were not shown clearly, and the CT scan showed low density lesions .5. In 31 lesions, 1 Cholangiocarcinoma lesion was misdiagnosised by CEUS and also CECT.Conclusion:1. CEUS can observe the whole enhancement dynamically and consecutively, especially in the early arterial phase. And contrast-enhanced CT scan the focal liver lesions at intervals, it is impossible to demonstrate the hemodynamics of focal liver lesions before 25 s. However, the enhanced features in the period of 0～25 s are very important for the diagnosis of the lesions, so CEUS plays an important role in diagnosis of focal liver lesions which enhanced early in the arterial phase(<25s).2. CEUS showed those focal liver lesions poor which are at the background of cirrhosis or at the top diaphragm of the severe fatty liver,.3. To improve the accuracy of the diagnosis of CEUS, we must analyze the enhancement characteristics of specific types of liver cancer correctly.