[Contrast-enhanced ultrasound with Optison in percutaneous thermoablation of liver tumors].
OBJECTIVE
To detect vascularization of liver tumors by ultrasound enhanced with Optison and to determine whether increasing necrosis during a percutaneous thermal ablation can be visualized by this method.


METHODS
Twenty-two patients with non-resectable malignant liver tumors (9 patients with HCC, 13 patients with metastases) and a total number of 34 lesions underwent percutaneous radiofrequency thermoablation using a needle applicator perfused with a 0.9 % NaCl solution (Electrotome HiTT 106, Berchtold). The tumor size ranged from 2 to 8 cm with an average size of 3.6 cm. While intermittent energy was supplied during thermoablation, multi-slice CT (Volume-Zoom, Siemens) and ultrasound were obtained. Ultrasound was performed with a multi-frequency transducer (3 - 7 MHz, LOGIQ 700, GE) and 0.5 to 1 ml of Optison as contrast agent. If necessary, the injection of the contrast agent was repeated after about 30 min. The mechanical index (MI) was set low (0.2 - 0.3) to prevent bubble destruction. Ultrasound power Doppler (PD), contrast harmonic imaging (CHI) and coded harmonic angiography (CHA) as subtraction mode of harmonic imaging were applied intermittently.


RESULTS
Only 21 of the 34 lesions showed increased intratumoral perfusion when the conventional B-Mode with PD was used. Similar to spiral CT, the tumor vascularization in the early arterial phase was only reliably visible with CHA after application of contrast agent. CHI with PD was best to detect increasing hypoperfusion of the tumors. When the energy supply was continued, hyperechoic border zones became visible around the central hypoechoic defects. The contrast between remaining tumor and surrounding liver tissue improved in CHI for up to 30 min after the bolus injection of contrast medium, considerably facilitating the evaluation of perfusion. Metal artifacts and the limited amount of contrast agent that can be safely administered interfered with monitoring the thermal ablation with spiral-CT. After an administered energy of maximal 100.000 watts, no more tumor vascularization was seen in 28 of 34 cases. Follow-up spiral-CT showed a complete necrosis in these cases.


CONCLUSIONS
Evaluating perfusion with contrast-enhanced ultrasound may be helpful in monitoring the evolving necrosis during thermoablation of liver tumors. The more reliable assessment of the tumor necrosis enables a more targeted therapy.
Jung
E M
EM
Institut für Röntgendiagnostik, Klinikum Passau. jung@fmi.uni-passau.de
Clevert
D-A
DA
Rupp
N
N
D000368:Aged; D000418:Albumins; D015901:Angiography, Digital Subtraction; D001943:Breast Neoplasms / Q000098:blood supply / Q000000981:diagnostic imaging / Q000628:therapy; D006528:Carcinoma, Hepatocellular / Q000098:blood supply / Q000000981:diagnostic imaging / Q000628:therapy*; D015179:Colorectal Neoplasms / Q000098:blood supply / Q000000981:diagnostic imaging / Q000628:therapy; D003287:Contrast Media; D005260:Female; D005466:Fluorocarbons; D005500:Follow-Up Studies; D006801:Humans; D006979:Hyperthermia, Induced / Q000379:methods*; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008099:Liver / Q000473:pathology; D008113:Liver Neoplasms / Q000098:blood supply / Q000000981:diagnostic imaging / Q000556:secondary* / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D009336:Necrosis; D015203:Reproducibility of Results; D036542:Tomography, Spiral Computed; D018608:Ultrasonography, Doppler / Q000379:methods; D018084:Ultrasonography, Interventional / Q000379:methods*
D000418:Albumins; D003287:Contrast Media; C099458:FS 069; D005466:Fluorocarbons