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Tumor Ablation with Radio-frequency Energy¹

¹ From the Decision Analysis and Technology Assessment Group, Department of Radiology, Massachusetts General Hospital, Zero Emerson Pl, Ste 2H, Boston, MA 02114 (G.S.G.); the Department of Health Policy and Management, Harvard School of Public Health, Boston, Mass (G.S.G.); the Minimally Invasive Therapies Laboratory, Department of Radiology, Beth Israel Deaconess Medical Center, Boston, Mass (S.N.G.); the Department of Radiology, General Hospital, Busto Arsizio, Italy (L.S.); and the Department of Radiology, Ospedale Civile, Vimercate, Milan, Italy (T.L.). Received August 11, 1999; revision requested September 24; revision received November 16; accepted December 6; updated July 26, 2000. S.N.G. supported by research funding from Radionics. Address correspondence to. G.S.G. (e-mail: gazelle@nmr.mgh.harvard.edu).

View larger version (157K): [in a new window]   Figure 1a. Successful treatment of a large HCC lesion. (a) Transverse contrast agent-enhanced CT scan obtained in the hepatic arterial phase shows a large hypervascular tumor (arrows) located in Couinaud segment 7. (b) Oblique subcostal US image obtained during RF ablation with an internally cooled cluster electrode system shows two of three electrodes (arrowheads) well positioned in the tumor. Hypervascularity is related to microbubble formation during treatment. Also note small bubbles (arrows) escaping into an adjacent hepatic vein, a fairly common occurrence. (c) Lateral oblique US image obtained 6 months after treatment shows that electrode tracks (arrows) remain visible. (d) Transverse contrast-enhanced arterial phase CT scan obtained 6 months after treatment shows uniform hypoattenuation (arrow) and absence of contrast enhancement, which are evidence of successful treatment.

View larger version (152K): [in a new window]   Figure 1b. Successful treatment of a large HCC lesion. (a) Transverse contrast agent-enhanced CT scan obtained in the hepatic arterial phase shows a large hypervascular tumor (arrows) located in Couinaud segment 7. (b) Oblique subcostal US image obtained during RF ablation with an internally cooled cluster electrode system shows two of three electrodes (arrowheads) well positioned in the tumor. Hypervascularity is related to microbubble formation during treatment. Also note small bubbles (arrows) escaping into an adjacent hepatic vein, a fairly common occurrence. (c) Lateral oblique US image obtained 6 months after treatment shows that electrode tracks (arrows) remain visible. (d) Transverse contrast-enhanced arterial phase CT scan obtained 6 months after treatment shows uniform hypoattenuation (arrow) and absence of contrast enhancement, which are evidence of successful treatment.

View larger version (156K): [in a new window]   Figure 1c. Successful treatment of a large HCC lesion. (a) Transverse contrast agent-enhanced CT scan obtained in the hepatic arterial phase shows a large hypervascular tumor (arrows) located in Couinaud segment 7. (b) Oblique subcostal US image obtained during RF ablation with an internally cooled cluster electrode system shows two of three electrodes (arrowheads) well positioned in the tumor. Hypervascularity is related to microbubble formation during treatment. Also note small bubbles (arrows) escaping into an adjacent hepatic vein, a fairly common occurrence. (c) Lateral oblique US image obtained 6 months after treatment shows that electrode tracks (arrows) remain visible. (d) Transverse contrast-enhanced arterial phase CT scan obtained 6 months after treatment shows uniform hypoattenuation (arrow) and absence of contrast enhancement, which are evidence of successful treatment.

View larger version (156K): [in a new window]   Figure 1d. Successful treatment of a large HCC lesion. (a) Transverse contrast agent-enhanced CT scan obtained in the hepatic arterial phase shows a large hypervascular tumor (arrows) located in Couinaud segment 7. (b) Oblique subcostal US image obtained during RF ablation with an internally cooled cluster electrode system shows two of three electrodes (arrowheads) well positioned in the tumor. Hypervascularity is related to microbubble formation during treatment. Also note small bubbles (arrows) escaping into an adjacent hepatic vein, a fairly common occurrence. (c) Lateral oblique US image obtained 6 months after treatment shows that electrode tracks (arrows) remain visible. (d) Transverse contrast-enhanced arterial phase CT scan obtained 6 months after treatment shows uniform hypoattenuation (arrow) and absence of contrast enhancement, which are evidence of successful treatment.

View larger version (151K): [in a new window]   Figure 2a. Successful treatment of locally recurrent HCC. (a) Transverse contrast-enhanced arterial phase CT scan demonstrates a large hypervascular tumor (arrows) in Couinaud segment 8. (b) Transverse contrast-enhanced CT scan obtained 1 month after treatment with an internally cooled cluster electrode system shows internal hyperattenuation (arrows), which likely represents blood. The lack of contrast enhancement suggests that there is no residual viable tumor. (c) Transverse contrast-enhanced CT scan obtained 6 months after treatment demonstrates marked hypoattenuation throughout the majority of the tumor; however, a single crescentic focus of enhancing tissue posteromedially (arrow) indicates local tumor recurrence. (d) Transverse contrast-enhanced CT scan obtained 3 months after repeat treatment with a single internally cooled electrode demonstrates uniform hypoattenuation (arrows), suggestive of a complete response.

View larger version (150K): [in a new window]   Figure 2b. Successful treatment of locally recurrent HCC. (a) Transverse contrast-enhanced arterial phase CT scan demonstrates a large hypervascular tumor (arrows) in Couinaud segment 8. (b) Transverse contrast-enhanced CT scan obtained 1 month after treatment with an internally cooled cluster electrode system shows internal hyperattenuation (arrows), which likely represents blood. The lack of contrast enhancement suggests that there is no residual viable tumor. (c) Transverse contrast-enhanced CT scan obtained 6 months after treatment demonstrates marked hypoattenuation throughout the majority of the tumor; however, a single crescentic focus of enhancing tissue posteromedially (arrow) indicates local tumor recurrence. (d) Transverse contrast-enhanced CT scan obtained 3 months after repeat treatment with a single internally cooled electrode demonstrates uniform hypoattenuation (arrows), suggestive of a complete response.

View larger version (140K): [in a new window]   Figure 2c. Successful treatment of locally recurrent HCC. (a) Transverse contrast-enhanced arterial phase CT scan demonstrates a large hypervascular tumor (arrows) in Couinaud segment 8. (b) Transverse contrast-enhanced CT scan obtained 1 month after treatment with an internally cooled cluster electrode system shows internal hyperattenuation (arrows), which likely represents blood. The lack of contrast enhancement suggests that there is no residual viable tumor. (c) Transverse contrast-enhanced CT scan obtained 6 months after treatment demonstrates marked hypoattenuation throughout the majority of the tumor; however, a single crescentic focus of enhancing tissue posteromedially (arrow) indicates local tumor recurrence. (d) Transverse contrast-enhanced CT scan obtained 3 months after repeat treatment with a single internally cooled electrode demonstrates uniform hypoattenuation (arrows), suggestive of a complete response.

View larger version (144K): [in a new window]   Figure 2d. Successful treatment of locally recurrent HCC. (a) Transverse contrast-enhanced arterial phase CT scan demonstrates a large hypervascular tumor (arrows) in Couinaud segment 8. (b) Transverse contrast-enhanced CT scan obtained 1 month after treatment with an internally cooled cluster electrode system shows internal hyperattenuation (arrows), which likely represents blood. The lack of contrast enhancement suggests that there is no residual viable tumor. (c) Transverse contrast-enhanced CT scan obtained 6 months after treatment demonstrates marked hypoattenuation throughout the majority of the tumor; however, a single crescentic focus of enhancing tissue posteromedially (arrow) indicates local tumor recurrence. (d) Transverse contrast-enhanced CT scan obtained 3 months after repeat treatment with a single internally cooled electrode demonstrates uniform hypoattenuation (arrows), suggestive of a complete response.

View larger version (183K): [in a new window]   Figure 3a. Successful treatment of multifocal HCC. (a) Transverse contrast-enhanced CT scan obtained 1 month after RF ablation demonstrates an apparent complete response, indicated by the hypoattenuating area (arrow). (b) Follow-up transverse contrast-enhanced CT scan obtained 1 year after treatment demonstrates four small satellite lesions (arrows) but apparently complete necrosis of the initially treated lesion. (c) Transverse contrast-enhanced CT scan obtained 3 months after successful treatment of satellite lesions by using internally cooled electrodes. Treatment required two separate electrode insertions. Three additional small lesions (not seen on this image) in different hepatic segments were present in this patient and were successfully treated with RF ablation.

View larger version (177K): [in a new window]   Figure 3b. Successful treatment of multifocal HCC. (a) Transverse contrast-enhanced CT scan obtained 1 month after RF ablation demonstrates an apparent complete response, indicated by the hypoattenuating area (arrow). (b) Follow-up transverse contrast-enhanced CT scan obtained 1 year after treatment demonstrates four small satellite lesions (arrows) but apparently complete necrosis of the initially treated lesion. (c) Transverse contrast-enhanced CT scan obtained 3 months after successful treatment of satellite lesions by using internally cooled electrodes. Treatment required two separate electrode insertions. Three additional small lesions (not seen on this image) in different hepatic segments were present in this patient and were successfully treated with RF ablation.

View larger version (188K): [in a new window]   Figure 3c. Successful treatment of multifocal HCC. (a) Transverse contrast-enhanced CT scan obtained 1 month after RF ablation demonstrates an apparent complete response, indicated by the hypoattenuating area (arrow). (b) Follow-up transverse contrast-enhanced CT scan obtained 1 year after treatment demonstrates four small satellite lesions (arrows) but apparently complete necrosis of the initially treated lesion. (c) Transverse contrast-enhanced CT scan obtained 3 months after successful treatment of satellite lesions by using internally cooled electrodes. Treatment required two separate electrode insertions. Three additional small lesions (not seen on this image) in different hepatic segments were present in this patient and were successfully treated with RF ablation.

View larger version (151K): [in a new window]   Figure 4a. Successful treatment of a single small metastasis from colon cancer. (a) Transverse contrast-enhanced CT scan obtained before treatment shows a single small tumor (arrow) in Couinaud segment 8. There was no other evidence of metastatic disease. (b) Transverse contrast-enhanced CT scan obtained 1 month after RF ablation with two insertions of a single internally cooled electrode shows a 4.5 x 6.0-cm zone (indicated by cursors and 1 and 2) of hypoattenuation without contrast enhancement (arrow), suggestive of a complete response. (c) Transverse contrast-enhanced CT scan obtained 10 months after treatment demonstrates decreased size of the zone of coagulation necrosis (arrow), without evidence of local recurrence. At many centers, this patient might have been considered a candidate for hepatic resection. Successful treatment with RF obviated surgery and allowed a period of observation to confirm that no other metastatic lesions were present.

View larger version (156K): [in a new window]   Figure 4b. Successful treatment of a single small metastasis from colon cancer. (a) Transverse contrast-enhanced CT scan obtained before treatment shows a single small tumor (arrow) in Couinaud segment 8. There was no other evidence of metastatic disease. (b) Transverse contrast-enhanced CT scan obtained 1 month after RF ablation with two insertions of a single internally cooled electrode shows a 4.5 x 6.0-cm zone (indicated by cursors and 1 and 2) of hypoattenuation without contrast enhancement (arrow), suggestive of a complete response. (c) Transverse contrast-enhanced CT scan obtained 10 months after treatment demonstrates decreased size of the zone of coagulation necrosis (arrow), without evidence of local recurrence. At many centers, this patient might have been considered a candidate for hepatic resection. Successful treatment with RF obviated surgery and allowed a period of observation to confirm that no other metastatic lesions were present.

View larger version (159K): [in a new window]   Figure 4c. Successful treatment of a single small metastasis from colon cancer. (a) Transverse contrast-enhanced CT scan obtained before treatment shows a single small tumor (arrow) in Couinaud segment 8. There was no other evidence of metastatic disease. (b) Transverse contrast-enhanced CT scan obtained 1 month after RF ablation with two insertions of a single internally cooled electrode shows a 4.5 x 6.0-cm zone (indicated by cursors and 1 and 2) of hypoattenuation without contrast enhancement (arrow), suggestive of a complete response. (c) Transverse contrast-enhanced CT scan obtained 10 months after treatment demonstrates decreased size of the zone of coagulation necrosis (arrow), without evidence of local recurrence. At many centers, this patient might have been considered a candidate for hepatic resection. Successful treatment with RF obviated surgery and allowed a period of observation to confirm that no other metastatic lesions were present.

View larger version (179K): [in a new window]   Figure 5a. Successful treatment of two metastases from colon cancer. (a) Transverse contrast-enhanced portal venous phase CT scan obtained 1 month after treatment of two large tumors by using internally cooled cluster electrode systems. Note the thick rims of enhancing tissue (arrowheads), which were thought to be somewhat suggestive of residual viable tumor versus posttreatment hyperemia. Repeat treatment was not performed at this time due to unfavorable geometry and because of the possibility that the rims of enhancement were related to hyperemia rather than tumor. (b) Transverse contrast-enhanced CT scan obtained 6 months after initial treatment demonstrates reduction in peripheral hyperattenuation, confirming that the rims represented hyperemia rather than tumor.

View larger version (169K): [in a new window]   Figure 5b. Successful treatment of two metastases from colon cancer. (a) Transverse contrast-enhanced portal venous phase CT scan obtained 1 month after treatment of two large tumors by using internally cooled cluster electrode systems. Note the thick rims of enhancing tissue (arrowheads), which were thought to be somewhat suggestive of residual viable tumor versus posttreatment hyperemia. Repeat treatment was not performed at this time due to unfavorable geometry and because of the possibility that the rims of enhancement were related to hyperemia rather than tumor. (b) Transverse contrast-enhanced CT scan obtained 6 months after initial treatment demonstrates reduction in peripheral hyperattenuation, confirming that the rims represented hyperemia rather than tumor.

View larger version (136K): [in a new window]   Figure 6a. Transverse color Doppler US scans demonstrate treatment of hyperfunctioning parathyroid adenoma by using combined PEI and RF ablation. (a) Pretreatment scan shows a hypervascular parathyroid mass (arrows). (b) Scan obtained during RF ablation shows hyperechogenicity within the mass (arrows), which is related to microbubble formation due to tissue heating. The tip of the RF electrode (arrowhead) can be seen as a pinpoint focus of increased echogenicity. (c) Posttreatment scan shows hypoechogenicity (arrows) replacing the mass and elimination of hypervascularity. The small focus of color signal is related to an adjacent blood vessel.

View larger version (155K): [in a new window]   Figure 6b. Transverse color Doppler US scans demonstrate treatment of hyperfunctioning parathyroid adenoma by using combined PEI and RF ablation. (a) Pretreatment scan shows a hypervascular parathyroid mass (arrows). (b) Scan obtained during RF ablation shows hyperechogenicity within the mass (arrows), which is related to microbubble formation due to tissue heating. The tip of the RF electrode (arrowhead) can be seen as a pinpoint focus of increased echogenicity. (c) Posttreatment scan shows hypoechogenicity (arrows) replacing the mass and elimination of hypervascularity. The small focus of color signal is related to an adjacent blood vessel.

View larger version (154K): [in a new window]   Figure 6c. Transverse color Doppler US scans demonstrate treatment of hyperfunctioning parathyroid adenoma by using combined PEI and RF ablation. (a) Pretreatment scan shows a hypervascular parathyroid mass (arrows). (b) Scan obtained during RF ablation shows hyperechogenicity within the mass (arrows), which is related to microbubble formation due to tissue heating. The tip of the RF electrode (arrowhead) can be seen as a pinpoint focus of increased echogenicity. (c) Posttreatment scan shows hypoechogenicity (arrows) replacing the mass and elimination of hypervascularity. The small focus of color signal is related to an adjacent blood vessel.

View larger version (142K): [in a new window]   Figure 7a. Transverse contrast-enhanced CT scans demonstrate RF ablation of a 3.5-cm renal cell carcinoma in a patient with ovarian cancer in regression after treatment with systemic chemotherapy. (a) Pretreatment scan demonstrates a hypervascular mass (arrow) in upper pole of the right kidney. (b) Scan obtained 1 year after RF ablation with a single internally cooled electrode demonstrates hypoattenuation (arrow) and no evidence of local recurrence.

View larger version (159K): [in a new window]   Figure 7b. Transverse contrast-enhanced CT scans demonstrate RF ablation of a 3.5-cm renal cell carcinoma in a patient with ovarian cancer in regression after treatment with systemic chemotherapy. (a) Pretreatment scan demonstrates a hypervascular mass (arrow) in upper pole of the right kidney. (b) Scan obtained 1 year after RF ablation with a single internally cooled electrode demonstrates hypoattenuation (arrow) and no evidence of local recurrence.

View larger version (178K): [in a new window]   Figure 8a. Transverse contrast-enhanced CT scans demonstrate successful treatment of a solitary metastasis from colorectal carcinoma, with a surgical margin obtained. (a) Before treatment, a single small lesion (arrow) is present in Couinaud segments 5 and 6. (b) Scan obtained 3 months after treatment with an internally cooled clustered-electrode system shows a large focus of hypoattenuation (arrows) devoid of contrast enhancement and completely enveloping the previously seen tumor. A small adjacent focus of hypoattenuation (arrowhead) is related to placement of the RF electrodes.

View larger version (170K): [in a new window]   Figure 8b. Transverse contrast-enhanced CT scans demonstrate successful treatment of a solitary metastasis from colorectal carcinoma, with a surgical margin obtained. (a) Before treatment, a single small lesion (arrow) is present in Couinaud segments 5 and 6. (b) Scan obtained 3 months after treatment with an internally cooled clustered-electrode system shows a large focus of hypoattenuation (arrows) devoid of contrast enhancement and completely enveloping the previously seen tumor. A small adjacent focus of hypoattenuation (arrowhead) is related to placement of the RF electrodes.

View larger version (85K): [in a new window]   Figure 9. Oblique subcostal US scans show the evolution of US findings in HCC treated with RF ablation. A, Before treatment, a somewhat hyperechoic tumor (arrow) in the right lobe is visible. B, During RF ablation with a single internally cooled electrode, increased echogenicity secondary to microbubble formation completely envelops the tumor (arrows). The electrode (arrowhead) can be seen as a faint line of increased echogenicity. C, At 30 minutes after RF ablation, the focus of increased echogenicity has decreased markedly in size. The rapid change in appearance illustrates the difficulty in using US to determine the extent of treatment effect.

View larger version (148K): [in a new window]   Figure 10. Transverse gradient-echo MR image (repetition time, 125 msec; echo time, 4.2 msec; echo train length, one; one signal acquired) obtained 6 months after RF ablation with a single internally cooled electrode shows unsuccessful treatment of metastasis (arrowheads) from colorectal carcinoma, with unfavorable geometry for re-treatment. The tumor completely surrounds a central area of coagulation necrosis, resulting from inadequate tissue margins. When a complete rim of locally recurrent tumor is present after unsuccessful RF ablation, successful re-treatment is often impossible because of the difficulty in adequately covering the entire surface of the now-larger sphere of tumor.