VX2 carcinoma in rabbits after radiofrequency ablation: comparison of MR contrast agents for help in differentiating benign periablational enhancement from residual tumor.
OBJECTIVE
To prospectively compare the accuracy of a blood pool agent, SH L 643A, with that of gadopentetate dimeglumine in differentiating benign periablational enhancement from residual tumor in VX2 carcinomas in rabbits after radiofrequency (RF) ablation.


METHODS
Experiment was approved by the animal care committee. Sequential MR images were obtained before and with SH L 643A (17 000 Da, 0.05 mmol/kg) and, after a 24-hour interval, gadopentetate dimeglumine (546 Da, 0.1 mmol/kg) in 12 rabbits with VX2 carcinoma in the back muscle prior to (n = 12) and early (n = 12), 1 week (n = 8), and 4 weeks (n = 4) after RF ablation. RF ablation was performed with output of 90 W but at less than 300 seconds to ensure incomplete tumor ablation. The pathologic specimens were sectioned in the same plane as MR imaging, and the enhancement ratios (ie, the ratios of postcontrast to precontrast signal intensity) and the microvessel densities of residual tumor and benign periablational enhancement were assessed.


RESULTS
With SH L 643A, the peak enhancement ratios of residual tumor (1.64 +/- 0.31 [standard deviation]) were significantly higher than those of benign periablational enhancement (0.97 +/- 0.16) (P < .001). With gadopentetate dimeglumine, the peak enhancement ratios of residual tumor (1.82 +/- 0.33) were not different from those of benign periablational enhancement (1.71 +/- 0.36). In benign periablational enhancement, enhancement ratios with injection of SH L 643A were lower than those with injection of gadopentetate dimeglumine for all time points up to 30 minutes (P < .05). The microvessel density was 25.72 +/- 5.43 vessels per field of view for residual tumor and 10.37 +/- 2.88 vessels per field of view for benign periablational enhancement (P < .001).


CONCLUSIONS
Blood pool contrast agent SH L 643A permits more accurate differentiation of benign periablational enhancement from residual tumor compared with the extracellular agent gadopentetate dimeglumine.
Kim
Tae Jung
TJ
Department of Radiology and Clinical Research Institute, Seoul National University Hospital and the Institute of Radiation Medicine, Seoul National University Medical Research Center, 28 Yongon-dong, Chongno-gu, Seoul 110-744, Korea.
Moon
Woo Kyung
WK
Cha
Joo Hee
JH
Goo
Jin Mo
JM
Lee
Kyoung Ho
KH
Kim
Keon Ha
KH
Lee
Joon Woo
JW
Han
Joon Goo
JG
Weinmann
Hanns-Joachim
HJ
Chang
Kee Hyun
KH
D000818:Animals; D017115:Catheter Ablation; D003287:Contrast Media; D003937:Diagnosis, Differential; D005682:Gadolinium; D019786:Gadolinium DTPA; D008279:Magnetic Resonance Imaging; D018365:Neoplasm, Residual / Q000175:diagnosis*; D009374:Neoplasms, Experimental / Q000175:diagnosis / Q000601:surgery*; D011446:Prospective Studies; D011817:Rabbits
D003287:Contrast Media; C402765:gadomer 17; D005682:Gadolinium; D019786:Gadolinium DTPA