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Large Liver Tumors: Protocol for Radiofrequency Ablation and Its Clinical Application in 110 Patients—Mathematic Model, Overlapping Mode, and Electrode Placement Process¹

¹ From the Department of Ultrasound, School of Clinical Oncology, Peking University, 52 Fu-cheng Rd, Hai-Dian District, Beijing 100036, China (M.H.C., W.Y., K.Y., Y.D.); Department of Mathematics, High School Affiliated to Capital Normal University, Beijing, China (M.W.Z.); Department of Radiology, Ospedale Generale, Busto Arsizio, Italy (L.S.); and Department of Radiology, Thomas Jefferson University Hospital, Philadelphia, Pa (J.B.L.). Received May 26, 2003; revision requested August 6; revision received October 15; accepted November 25. Address correspondence to M.H.C. (e-mail: minhuachen@vip.sina.com).

View larger version (24K): [in a new window]   Figure 1. Computer representations of regular tetrahedron model. A, Transillumination view of the model: A regular tetrahedron is inscribed in a target sphere. The centers of three sides of the imaginary regular tetrahedron are in one section (the lower section comprising two-fifths of the tumor), and the center of the fourth side is above this section. Each side of the regular tetrahedron might be treated with one ablation. B, The lower two-fifths of the cross section of the tumor: Three target sites are determined, and each site is 0.8 cm from the center of this section. C, Anterior view of the model: The fourth ablation sphere is placed directly above the ablated area in the section that is perpendicular to the plane illustrated in B. Then, the target sphere circumscribing the tetrahedron can be treated with four ablation spheres. x indicates the target site of the ablation—that is, the ablation sphere center. In our experience, the electrode tip was inserted 1.5 cm proximal to the target site.

View larger version (29K): [in a new window]   Figure 2. Computer representations of a regular five-sided prism model. A, Transillumination view of the model: A regular five-sided prism is inscribed in a target sphere. The ablation model is constructed by performing five ablations on the five lateral sides, one ablation on the upper side, and another ablation on the lower side, for a total of seven ablations. B, Anterosuperior view of the model: Five ablations are performed on lateral sides of the regular prism. C, Two additional spheres are used to cover the upper and lower sides. The drawing depicts the ablation volume encompassing the target sphere—that is, the tumor plus at least 0.5 cm of tumor-free margin. x indicates the target site of each ablation—that is, the ablation sphere center.

View larger version (21K): [in a new window]   Figure 3. Illustration of US sections used to guide RF ablation with use of a regular five-sided prism model. A, Maximum transverse view of the tumor: Five target sites are determined to guide electrode insertions. B, Same section as A: Five ablations are performed in the middle part of the tumor. C, The section perpendicular to A: Two additional ablations are performed at the two poles of the tumor. The tumor can be effectively ablated with seven ablation spheres. x indicates the target site of the ablation—that is, the ablation sphere center. In our experience, the electrode tip was inserted 1.5 cm proximal to the target site.

View larger version (122K): [in a new window]   Figure 4a. Images obtained in 61-year-old man with a 5.3 x 5.2-cm HCC. The regular five-sided prism model with seven ablation spheres was used to ablate this tumor. (a) Contrast material-enhanced transverse CT scan obtained before treatment shows a spherical tumor (arrowhead) in the right lobe of the liver. (b) US evaluation of the maximum size of the tumor. Left: Maximum transverse view of the tumor shows that five target sites, 1-5, were determined. In our experience, the electrode tip was inserted 1.5 cm proximal to the target site. Right: Sagittal view of the tumor shows the sixth, 6, and seventh, 7, target sites at the two poles of the tumor, which are located, respectively, in the left and right regions of this section. (c) Transverse US scan obtained during RF treatment shows the fifth ablation. Arrow indicates the prongs deployed from the needle cannula, and arrowhead indicates the hyperechogenicity of the ablated area.

View larger version (108K): [in a new window]   Figure 4b. Images obtained in 61-year-old man with a 5.3 x 5.2-cm HCC. The regular five-sided prism model with seven ablation spheres was used to ablate this tumor. (a) Contrast material-enhanced transverse CT scan obtained before treatment shows a spherical tumor (arrowhead) in the right lobe of the liver. (b) US evaluation of the maximum size of the tumor. Left: Maximum transverse view of the tumor shows that five target sites, 1-5, were determined. In our experience, the electrode tip was inserted 1.5 cm proximal to the target site. Right: Sagittal view of the tumor shows the sixth, 6, and seventh, 7, target sites at the two poles of the tumor, which are located, respectively, in the left and right regions of this section. (c) Transverse US scan obtained during RF treatment shows the fifth ablation. Arrow indicates the prongs deployed from the needle cannula, and arrowhead indicates the hyperechogenicity of the ablated area.

View larger version (145K): [in a new window]   Figure 4c. Images obtained in 61-year-old man with a 5.3 x 5.2-cm HCC. The regular five-sided prism model with seven ablation spheres was used to ablate this tumor. (a) Contrast material-enhanced transverse CT scan obtained before treatment shows a spherical tumor (arrowhead) in the right lobe of the liver. (b) US evaluation of the maximum size of the tumor. Left: Maximum transverse view of the tumor shows that five target sites, 1-5, were determined. In our experience, the electrode tip was inserted 1.5 cm proximal to the target site. Right: Sagittal view of the tumor shows the sixth, 6, and seventh, 7, target sites at the two poles of the tumor, which are located, respectively, in the left and right regions of this section. (c) Transverse US scan obtained during RF treatment shows the fifth ablation. Arrow indicates the prongs deployed from the needle cannula, and arrowhead indicates the hyperechogenicity of the ablated area.

View larger version (65K): [in a new window]   Figure 5. Computer representations of regular dodecahedron model (ie, three-segment overlapping ablations). A, Transillumination view of the model: The target sphere is divided into deep, middle, and superficial segments, which are parallel to each other. Six target sites are determined on the maximum transverse section of the tumor. B, Anterosuperior view of the model shows six ablations in the middle segment. C, Anteroinferior view of the model shows three ablations in the deep segment. D, Anterosuperior view of the model shows three ablations in the superficial segment. Then, a 7.5-cm target sphere is treated by performing 12 ablations. x indicates the target site of each ablation—that is, the ablation sphere center.

View larger version (153K): [in a new window]   Figure 6a. Adjuvant measure for electrode placement in 52-year-old man with a 5.3 x 5.4-cm HCC protruding from the liver surface. The regular five-sided prism model was used to ablate this tumor. (a) Five ablations were required for the middle part of the tumor. The adjuvant method was used to facilitate the precise electrode placements and to avoid injury to surrounding structures such as bowel. The first ablation is shown; two very small needles are inserted into the tumor from two puncture points to guide the electrode placements of the other four ablations. (b) Maximum transverse US view of the tumor shows three hyperechogenic spots, which are three needle tips. The lowest spot is the position of the first ablation. 1 indicates the first ablation site, and 2-5 are the sites of the other four ablations, which are positioned around the two small needles, which represent the lateral-side ablations of the regular five-sided prism. Finally, ablations at the two poles of the tumor on the perpendicular section were accomplished.

View larger version (141K): [in a new window]   Figure 6b. Adjuvant measure for electrode placement in 52-year-old man with a 5.3 x 5.4-cm HCC protruding from the liver surface. The regular five-sided prism model was used to ablate this tumor. (a) Five ablations were required for the middle part of the tumor. The adjuvant method was used to facilitate the precise electrode placements and to avoid injury to surrounding structures such as bowel. The first ablation is shown; two very small needles are inserted into the tumor from two puncture points to guide the electrode placements of the other four ablations. (b) Maximum transverse US view of the tumor shows three hyperechogenic spots, which are three needle tips. The lowest spot is the position of the first ablation. 1 indicates the first ablation site, and 2-5 are the sites of the other four ablations, which are positioned around the two small needles, which represent the lateral-side ablations of the regular five-sided prism. Finally, ablations at the two poles of the tumor on the perpendicular section were accomplished.

View larger version (143K): [in a new window]   Figure 7. Contrast-enhanced transverse CT scan obtained 1 month after RF ablation treatment in the same patient as in Figure 4 shows a low-attenuation coagulation area (arrowhead) with a clear margin and no enhancement. The regular five-sided prism model was used to treat this 5.3 x 5.2-cm HCC. The patient had no local tumor recurrence during the 1-year follow-up period.

View larger version (135K): [in a new window]   Figure 8a. Images obtained in 40-year-old woman with a single 4.6 x 4.4-cm hepatic metastatic nodule from rectal carcinoma. The regular three-sided prism model with five ablation spheres was considered. (a) Contrast-enhanced transverse CT scan obtained before RF ablation shows a spherelike tumor (arrowhead) in the right lobe of the liver. (b) Maximum transverse US view of the tumor shows three proposed target sites on the lateral sides of the prism. (c) Transverse US scan obtained during RF ablation shows the first ablation sphere is correctly positioned. (d) Sagittal US view of the tumor shows the position of the fifth ablation (arrowhead) in the superficial part of the tumor after the fourth ablation (arrow) in the deep part was accomplished. The hyperechoic ablated region extends 6.5 cm. (e) Contrast-enhanced transverse CT scan obtained 1 month after RF ablation shows complete necrosis of the tumor (arrowhead). The ablated area is larger than 6 cm in diameter. (f) Contrast-enhanced transverse CT scan obtained 6 months after RF ablation shows the markedly decreased size of the ablation zone (arrowhead). No enhancement or new lesion is detected. This patient survived for more than 2 years after the treatment.

View larger version (128K): [in a new window]   Figure 8b. Images obtained in 40-year-old woman with a single 4.6 x 4.4-cm hepatic metastatic nodule from rectal carcinoma. The regular three-sided prism model with five ablation spheres was considered. (a) Contrast-enhanced transverse CT scan obtained before RF ablation shows a spherelike tumor (arrowhead) in the right lobe of the liver. (b) Maximum transverse US view of the tumor shows three proposed target sites on the lateral sides of the prism. (c) Transverse US scan obtained during RF ablation shows the first ablation sphere is correctly positioned. (d) Sagittal US view of the tumor shows the position of the fifth ablation (arrowhead) in the superficial part of the tumor after the fourth ablation (arrow) in the deep part was accomplished. The hyperechoic ablated region extends 6.5 cm. (e) Contrast-enhanced transverse CT scan obtained 1 month after RF ablation shows complete necrosis of the tumor (arrowhead). The ablated area is larger than 6 cm in diameter. (f) Contrast-enhanced transverse CT scan obtained 6 months after RF ablation shows the markedly decreased size of the ablation zone (arrowhead). No enhancement or new lesion is detected. This patient survived for more than 2 years after the treatment.

View larger version (129K): [in a new window]   Figure 8c. Images obtained in 40-year-old woman with a single 4.6 x 4.4-cm hepatic metastatic nodule from rectal carcinoma. The regular three-sided prism model with five ablation spheres was considered. (a) Contrast-enhanced transverse CT scan obtained before RF ablation shows a spherelike tumor (arrowhead) in the right lobe of the liver. (b) Maximum transverse US view of the tumor shows three proposed target sites on the lateral sides of the prism. (c) Transverse US scan obtained during RF ablation shows the first ablation sphere is correctly positioned. (d) Sagittal US view of the tumor shows the position of the fifth ablation (arrowhead) in the superficial part of the tumor after the fourth ablation (arrow) in the deep part was accomplished. The hyperechoic ablated region extends 6.5 cm. (e) Contrast-enhanced transverse CT scan obtained 1 month after RF ablation shows complete necrosis of the tumor (arrowhead). The ablated area is larger than 6 cm in diameter. (f) Contrast-enhanced transverse CT scan obtained 6 months after RF ablation shows the markedly decreased size of the ablation zone (arrowhead). No enhancement or new lesion is detected. This patient survived for more than 2 years after the treatment.

View larger version (125K): [in a new window]   Figure 8d. Images obtained in 40-year-old woman with a single 4.6 x 4.4-cm hepatic metastatic nodule from rectal carcinoma. The regular three-sided prism model with five ablation spheres was considered. (a) Contrast-enhanced transverse CT scan obtained before RF ablation shows a spherelike tumor (arrowhead) in the right lobe of the liver. (b) Maximum transverse US view of the tumor shows three proposed target sites on the lateral sides of the prism. (c) Transverse US scan obtained during RF ablation shows the first ablation sphere is correctly positioned. (d) Sagittal US view of the tumor shows the position of the fifth ablation (arrowhead) in the superficial part of the tumor after the fourth ablation (arrow) in the deep part was accomplished. The hyperechoic ablated region extends 6.5 cm. (e) Contrast-enhanced transverse CT scan obtained 1 month after RF ablation shows complete necrosis of the tumor (arrowhead). The ablated area is larger than 6 cm in diameter. (f) Contrast-enhanced transverse CT scan obtained 6 months after RF ablation shows the markedly decreased size of the ablation zone (arrowhead). No enhancement or new lesion is detected. This patient survived for more than 2 years after the treatment.

View larger version (136K): [in a new window]   Figure 8e. Images obtained in 40-year-old woman with a single 4.6 x 4.4-cm hepatic metastatic nodule from rectal carcinoma. The regular three-sided prism model with five ablation spheres was considered. (a) Contrast-enhanced transverse CT scan obtained before RF ablation shows a spherelike tumor (arrowhead) in the right lobe of the liver. (b) Maximum transverse US view of the tumor shows three proposed target sites on the lateral sides of the prism. (c) Transverse US scan obtained during RF ablation shows the first ablation sphere is correctly positioned. (d) Sagittal US view of the tumor shows the position of the fifth ablation (arrowhead) in the superficial part of the tumor after the fourth ablation (arrow) in the deep part was accomplished. The hyperechoic ablated region extends 6.5 cm. (e) Contrast-enhanced transverse CT scan obtained 1 month after RF ablation shows complete necrosis of the tumor (arrowhead). The ablated area is larger than 6 cm in diameter. (f) Contrast-enhanced transverse CT scan obtained 6 months after RF ablation shows the markedly decreased size of the ablation zone (arrowhead). No enhancement or new lesion is detected. This patient survived for more than 2 years after the treatment.

View larger version (129K): [in a new window]   Figure 8f. Images obtained in 40-year-old woman with a single 4.6 x 4.4-cm hepatic metastatic nodule from rectal carcinoma. The regular three-sided prism model with five ablation spheres was considered. (a) Contrast-enhanced transverse CT scan obtained before RF ablation shows a spherelike tumor (arrowhead) in the right lobe of the liver. (b) Maximum transverse US view of the tumor shows three proposed target sites on the lateral sides of the prism. (c) Transverse US scan obtained during RF ablation shows the first ablation sphere is correctly positioned. (d) Sagittal US view of the tumor shows the position of the fifth ablation (arrowhead) in the superficial part of the tumor after the fourth ablation (arrow) in the deep part was accomplished. The hyperechoic ablated region extends 6.5 cm. (e) Contrast-enhanced transverse CT scan obtained 1 month after RF ablation shows complete necrosis of the tumor (arrowhead). The ablated area is larger than 6 cm in diameter. (f) Contrast-enhanced transverse CT scan obtained 6 months after RF ablation shows the markedly decreased size of the ablation zone (arrowhead). No enhancement or new lesion is detected. This patient survived for more than 2 years after the treatment.

View larger version (135K): [in a new window]   Figure 9. Images obtained in 46-year-old woman with 6.6 x 4.5-cm HCC that recurred after surgical resection. The three-segment overlapping model with 12 ablation spheres was used to ablate this tumor. A, Contrast-enhanced transverse CT scan obtained before RF ablation shows a multinodular tumor (arrowheads). B, Maximum transverse US view of the tumor shows the tumor size (6.6 x 4.5 cm). C, Left: Transverse US scan shows the position of the third ablation in the deep segment of the tumor. Middle: Transverse US scan shows the position of the fourth ablation in the middle segment, which is adjacent to the diaphragm and the heart (H). Right: Transverse US scan shows the position of the fifth ablation in the middle segment of the tumor after the angle of the transducer was adjusted. D, The RF procedure was interrupted after 10 ablations because the patient could not tolerate the ablation for the entire duration of the procedure. Contrast-enhanced transverse CT scan obtained 24 hours after RF ablation shows residual tumor tissue (arrow) in the superficial area of the tumor. E, US scans obtained 48 hours after RF ablation show a region of residual tumor tissue with an irregular border and a blood supply. A second ablation session was required. Left: Right subcostal oblique scan shows the positions of two additional ablations in the superficial area of the tumor. Right: Subxiphoid oblique scan obtained immediately after the second ablation session shows the hyperechogenic ablated area (arrowhead). F, Contrast-enhanced transverse CT scan obtained 1 month after the second ablation session shows a low-attenuation coagulation area extending 7 cm; the ablated region includes the tumor and the tumor-free margin. No enhancement at the circumference of the tumor is seen.