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Imaging-guided Radiofrequency Ablation of Renal Masses¹

¹ From the Department of Radiology, Wake Forest University Health Sciences, Medical Center Blvd, Winston-Salem, NC 27157-1088. Received February 25, 2004; revision requested April 2 and received May 11; accepted May 19. The author has no financial relationships to disclose. Address correspondence to the author (e-mail: rzagoria@wfubmc.edu).

View larger version (125K): [in a new window]   Figure 1a.  Radiofrequency electrodes currently available. (a) A, Starburst configuration multi-tine electrode (RITA [radiofrequency interstitial tissue ablation] system; Rita Medical Systems, Mountain View, Calif). B and C are the single and cluster electrodes, respectively, used in the Cool-tip radiofrequency ablation system (Radionics, Burlington, Mass). (b) The LeVeen electrode (Radiotherapeutics, Mountain View, Calif) is another multi-tine electrode design.

View larger version (103K): [in a new window]   Figure 1b.  Radiofrequency electrodes currently available. (a) A, Starburst configuration multi-tine electrode (RITA [radiofrequency interstitial tissue ablation] system; Rita Medical Systems, Mountain View, Calif). B and C are the single and cluster electrodes, respectively, used in the Cool-tip radiofrequency ablation system (Radionics, Burlington, Mass). (b) The LeVeen electrode (Radiotherapeutics, Mountain View, Calif) is another multi-tine electrode design.

View larger version (136K): [in a new window]   Figure 2a.  Steps in radiofrequency ablation of a renal tumor. The patient, an 83-year-old man with a history of bladder cancer and myocardial infarction, was referred for radiofrequency ablation because of his comorbidities. (a) Contrast-enhanced CT scan shows an avidly enhancing 3.8-cm-diameter mass (arrow) arising from the left kidney. (b) Unenhanced CT scan obtained with the patient in a prone position shows placement of a 19-gauge needle at the edge of the tumor. Fine-needle aspiration and core biopsy were performed at this position immediately before ablation. Biopsy results confirmed that the tumor was a clear cell renal adenocarcinoma. (c) CT scan obtained immediately after biopsy shows a cluster electrode being advanced into the tumor. The electrode was positioned near the interface of the kidney and the tumor in an attempt to ablate tumor at this margin. (d, e) CT scans obtained immediately after the first ablation show the electrode being repositioned into different areas of the tumor to overlap ablation zones. Additional ablations were performed after repositioning. (f) Contrast-enhanced CT scan obtained immediately after the three ablations shows no evidence of tumor enhancement. A thin rim of kidney adjacent to the tumor also does not enhance. This finding indicates ablation of the adjacent renal margin. A small amount of blood and gas is visible in the perinephric space. These findings are expected immediately after ablation. (g, h) Unenhanced (g) and contrast-enhanced (h) CT scans obtained 2 months after ablation show no evidence of residual viable tumor. On the unenhanced scan (g), the tumor appears slightly hyperattenuating, measuring 64 HU. This finding is believed to reflect coagulation necrosis in the tumor induced by ablation. The tumor does not enhance on the contrast-enhanced scan (h), where it measures 61 HU. The treated tumor is smaller than it was before treatment, which is also a typical feature following ablation.

View larger version (130K): [in a new window]   Figure 2b.  Steps in radiofrequency ablation of a renal tumor. The patient, an 83-year-old man with a history of bladder cancer and myocardial infarction, was referred for radiofrequency ablation because of his comorbidities. (a) Contrast-enhanced CT scan shows an avidly enhancing 3.8-cm-diameter mass (arrow) arising from the left kidney. (b) Unenhanced CT scan obtained with the patient in a prone position shows placement of a 19-gauge needle at the edge of the tumor. Fine-needle aspiration and core biopsy were performed at this position immediately before ablation. Biopsy results confirmed that the tumor was a clear cell renal adenocarcinoma. (c) CT scan obtained immediately after biopsy shows a cluster electrode being advanced into the tumor. The electrode was positioned near the interface of the kidney and the tumor in an attempt to ablate tumor at this margin. (d, e) CT scans obtained immediately after the first ablation show the electrode being repositioned into different areas of the tumor to overlap ablation zones. Additional ablations were performed after repositioning. (f) Contrast-enhanced CT scan obtained immediately after the three ablations shows no evidence of tumor enhancement. A thin rim of kidney adjacent to the tumor also does not enhance. This finding indicates ablation of the adjacent renal margin. A small amount of blood and gas is visible in the perinephric space. These findings are expected immediately after ablation. (g, h) Unenhanced (g) and contrast-enhanced (h) CT scans obtained 2 months after ablation show no evidence of residual viable tumor. On the unenhanced scan (g), the tumor appears slightly hyperattenuating, measuring 64 HU. This finding is believed to reflect coagulation necrosis in the tumor induced by ablation. The tumor does not enhance on the contrast-enhanced scan (h), where it measures 61 HU. The treated tumor is smaller than it was before treatment, which is also a typical feature following ablation.

View larger version (123K): [in a new window]   Figure 2c.  Steps in radiofrequency ablation of a renal tumor. The patient, an 83-year-old man with a history of bladder cancer and myocardial infarction, was referred for radiofrequency ablation because of his comorbidities. (a) Contrast-enhanced CT scan shows an avidly enhancing 3.8-cm-diameter mass (arrow) arising from the left kidney. (b) Unenhanced CT scan obtained with the patient in a prone position shows placement of a 19-gauge needle at the edge of the tumor. Fine-needle aspiration and core biopsy were performed at this position immediately before ablation. Biopsy results confirmed that the tumor was a clear cell renal adenocarcinoma. (c) CT scan obtained immediately after biopsy shows a cluster electrode being advanced into the tumor. The electrode was positioned near the interface of the kidney and the tumor in an attempt to ablate tumor at this margin. (d, e) CT scans obtained immediately after the first ablation show the electrode being repositioned into different areas of the tumor to overlap ablation zones. Additional ablations were performed after repositioning. (f) Contrast-enhanced CT scan obtained immediately after the three ablations shows no evidence of tumor enhancement. A thin rim of kidney adjacent to the tumor also does not enhance. This finding indicates ablation of the adjacent renal margin. A small amount of blood and gas is visible in the perinephric space. These findings are expected immediately after ablation. (g, h) Unenhanced (g) and contrast-enhanced (h) CT scans obtained 2 months after ablation show no evidence of residual viable tumor. On the unenhanced scan (g), the tumor appears slightly hyperattenuating, measuring 64 HU. This finding is believed to reflect coagulation necrosis in the tumor induced by ablation. The tumor does not enhance on the contrast-enhanced scan (h), where it measures 61 HU. The treated tumor is smaller than it was before treatment, which is also a typical feature following ablation.

View larger version (126K): [in a new window]   Figure 2d.  Steps in radiofrequency ablation of a renal tumor. The patient, an 83-year-old man with a history of bladder cancer and myocardial infarction, was referred for radiofrequency ablation because of his comorbidities. (a) Contrast-enhanced CT scan shows an avidly enhancing 3.8-cm-diameter mass (arrow) arising from the left kidney. (b) Unenhanced CT scan obtained with the patient in a prone position shows placement of a 19-gauge needle at the edge of the tumor. Fine-needle aspiration and core biopsy were performed at this position immediately before ablation. Biopsy results confirmed that the tumor was a clear cell renal adenocarcinoma. (c) CT scan obtained immediately after biopsy shows a cluster electrode being advanced into the tumor. The electrode was positioned near the interface of the kidney and the tumor in an attempt to ablate tumor at this margin. (d, e) CT scans obtained immediately after the first ablation show the electrode being repositioned into different areas of the tumor to overlap ablation zones. Additional ablations were performed after repositioning. (f) Contrast-enhanced CT scan obtained immediately after the three ablations shows no evidence of tumor enhancement. A thin rim of kidney adjacent to the tumor also does not enhance. This finding indicates ablation of the adjacent renal margin. A small amount of blood and gas is visible in the perinephric space. These findings are expected immediately after ablation. (g, h) Unenhanced (g) and contrast-enhanced (h) CT scans obtained 2 months after ablation show no evidence of residual viable tumor. On the unenhanced scan (g), the tumor appears slightly hyperattenuating, measuring 64 HU. This finding is believed to reflect coagulation necrosis in the tumor induced by ablation. The tumor does not enhance on the contrast-enhanced scan (h), where it measures 61 HU. The treated tumor is smaller than it was before treatment, which is also a typical feature following ablation.

View larger version (129K): [in a new window]   Figure 2e.  Steps in radiofrequency ablation of a renal tumor. The patient, an 83-year-old man with a history of bladder cancer and myocardial infarction, was referred for radiofrequency ablation because of his comorbidities. (a) Contrast-enhanced CT scan shows an avidly enhancing 3.8-cm-diameter mass (arrow) arising from the left kidney. (b) Unenhanced CT scan obtained with the patient in a prone position shows placement of a 19-gauge needle at the edge of the tumor. Fine-needle aspiration and core biopsy were performed at this position immediately before ablation. Biopsy results confirmed that the tumor was a clear cell renal adenocarcinoma. (c) CT scan obtained immediately after biopsy shows a cluster electrode being advanced into the tumor. The electrode was positioned near the interface of the kidney and the tumor in an attempt to ablate tumor at this margin. (d, e) CT scans obtained immediately after the first ablation show the electrode being repositioned into different areas of the tumor to overlap ablation zones. Additional ablations were performed after repositioning. (f) Contrast-enhanced CT scan obtained immediately after the three ablations shows no evidence of tumor enhancement. A thin rim of kidney adjacent to the tumor also does not enhance. This finding indicates ablation of the adjacent renal margin. A small amount of blood and gas is visible in the perinephric space. These findings are expected immediately after ablation. (g, h) Unenhanced (g) and contrast-enhanced (h) CT scans obtained 2 months after ablation show no evidence of residual viable tumor. On the unenhanced scan (g), the tumor appears slightly hyperattenuating, measuring 64 HU. This finding is believed to reflect coagulation necrosis in the tumor induced by ablation. The tumor does not enhance on the contrast-enhanced scan (h), where it measures 61 HU. The treated tumor is smaller than it was before treatment, which is also a typical feature following ablation.

View larger version (139K): [in a new window]   Figure 2f.  Steps in radiofrequency ablation of a renal tumor. The patient, an 83-year-old man with a history of bladder cancer and myocardial infarction, was referred for radiofrequency ablation because of his comorbidities. (a) Contrast-enhanced CT scan shows an avidly enhancing 3.8-cm-diameter mass (arrow) arising from the left kidney. (b) Unenhanced CT scan obtained with the patient in a prone position shows placement of a 19-gauge needle at the edge of the tumor. Fine-needle aspiration and core biopsy were performed at this position immediately before ablation. Biopsy results confirmed that the tumor was a clear cell renal adenocarcinoma. (c) CT scan obtained immediately after biopsy shows a cluster electrode being advanced into the tumor. The electrode was positioned near the interface of the kidney and the tumor in an attempt to ablate tumor at this margin. (d, e) CT scans obtained immediately after the first ablation show the electrode being repositioned into different areas of the tumor to overlap ablation zones. Additional ablations were performed after repositioning. (f) Contrast-enhanced CT scan obtained immediately after the three ablations shows no evidence of tumor enhancement. A thin rim of kidney adjacent to the tumor also does not enhance. This finding indicates ablation of the adjacent renal margin. A small amount of blood and gas is visible in the perinephric space. These findings are expected immediately after ablation. (g, h) Unenhanced (g) and contrast-enhanced (h) CT scans obtained 2 months after ablation show no evidence of residual viable tumor. On the unenhanced scan (g), the tumor appears slightly hyperattenuating, measuring 64 HU. This finding is believed to reflect coagulation necrosis in the tumor induced by ablation. The tumor does not enhance on the contrast-enhanced scan (h), where it measures 61 HU. The treated tumor is smaller than it was before treatment, which is also a typical feature following ablation.

View larger version (130K): [in a new window]   Figure 2g.  Steps in radiofrequency ablation of a renal tumor. The patient, an 83-year-old man with a history of bladder cancer and myocardial infarction, was referred for radiofrequency ablation because of his comorbidities. (a) Contrast-enhanced CT scan shows an avidly enhancing 3.8-cm-diameter mass (arrow) arising from the left kidney. (b) Unenhanced CT scan obtained with the patient in a prone position shows placement of a 19-gauge needle at the edge of the tumor. Fine-needle aspiration and core biopsy were performed at this position immediately before ablation. Biopsy results confirmed that the tumor was a clear cell renal adenocarcinoma. (c) CT scan obtained immediately after biopsy shows a cluster electrode being advanced into the tumor. The electrode was positioned near the interface of the kidney and the tumor in an attempt to ablate tumor at this margin. (d, e) CT scans obtained immediately after the first ablation show the electrode being repositioned into different areas of the tumor to overlap ablation zones. Additional ablations were performed after repositioning. (f) Contrast-enhanced CT scan obtained immediately after the three ablations shows no evidence of tumor enhancement. A thin rim of kidney adjacent to the tumor also does not enhance. This finding indicates ablation of the adjacent renal margin. A small amount of blood and gas is visible in the perinephric space. These findings are expected immediately after ablation. (g, h) Unenhanced (g) and contrast-enhanced (h) CT scans obtained 2 months after ablation show no evidence of residual viable tumor. On the unenhanced scan (g), the tumor appears slightly hyperattenuating, measuring 64 HU. This finding is believed to reflect coagulation necrosis in the tumor induced by ablation. The tumor does not enhance on the contrast-enhanced scan (h), where it measures 61 HU. The treated tumor is smaller than it was before treatment, which is also a typical feature following ablation.

View larger version (141K): [in a new window]   Figure 2h.  Steps in radiofrequency ablation of a renal tumor. The patient, an 83-year-old man with a history of bladder cancer and myocardial infarction, was referred for radiofrequency ablation because of his comorbidities. (a) Contrast-enhanced CT scan shows an avidly enhancing 3.8-cm-diameter mass (arrow) arising from the left kidney. (b) Unenhanced CT scan obtained with the patient in a prone position shows placement of a 19-gauge needle at the edge of the tumor. Fine-needle aspiration and core biopsy were performed at this position immediately before ablation. Biopsy results confirmed that the tumor was a clear cell renal adenocarcinoma. (c) CT scan obtained immediately after biopsy shows a cluster electrode being advanced into the tumor. The electrode was positioned near the interface of the kidney and the tumor in an attempt to ablate tumor at this margin. (d, e) CT scans obtained immediately after the first ablation show the electrode being repositioned into different areas of the tumor to overlap ablation zones. Additional ablations were performed after repositioning. (f) Contrast-enhanced CT scan obtained immediately after the three ablations shows no evidence of tumor enhancement. A thin rim of kidney adjacent to the tumor also does not enhance. This finding indicates ablation of the adjacent renal margin. A small amount of blood and gas is visible in the perinephric space. These findings are expected immediately after ablation. (g, h) Unenhanced (g) and contrast-enhanced (h) CT scans obtained 2 months after ablation show no evidence of residual viable tumor. On the unenhanced scan (g), the tumor appears slightly hyperattenuating, measuring 64 HU. This finding is believed to reflect coagulation necrosis in the tumor induced by ablation. The tumor does not enhance on the contrast-enhanced scan (h), where it measures 61 HU. The treated tumor is smaller than it was before treatment, which is also a typical feature following ablation.

View larger version (138K): [in a new window]   Figure 3a.  Hyperechoic zone caused by radiofrequency ablation in a patient who was enrolled in a "treat and resect" study (20) of renal tumor ablation. (a) Contrast-enhanced CT scan shows a 1.5-cm-diameter mass (arrow) in the right kidney. Biopsy findings confirmed that the tumor was an RCC. (b) Intraoperative US scan shows the isoechoic renal tumor (cursors) located anteriorly in the right kidney. (c) With US guidance, the electrode (arrow) was advanced into the tumor immediately before ablation. (d) US scan obtained during ablation of the tumor shows the hyperechoic zone (arrow) caused by radiofrequency ablation. This hyperechoic zone obscures the electrode and US detail of the treatment area. After nephrectomy, histologic examination of the specimen showed complete ablation of the tumor.

View larger version (109K): [in a new window]   Figure 3b.  Hyperechoic zone caused by radiofrequency ablation in a patient who was enrolled in a "treat and resect" study (20) of renal tumor ablation. (a) Contrast-enhanced CT scan shows a 1.5-cm-diameter mass (arrow) in the right kidney. Biopsy findings confirmed that the tumor was an RCC. (b) Intraoperative US scan shows the isoechoic renal tumor (cursors) located anteriorly in the right kidney. (c) With US guidance, the electrode (arrow) was advanced into the tumor immediately before ablation. (d) US scan obtained during ablation of the tumor shows the hyperechoic zone (arrow) caused by radiofrequency ablation. This hyperechoic zone obscures the electrode and US detail of the treatment area. After nephrectomy, histologic examination of the specimen showed complete ablation of the tumor.

View larger version (112K): [in a new window]   Figure 3c.  Hyperechoic zone caused by radiofrequency ablation in a patient who was enrolled in a "treat and resect" study (20) of renal tumor ablation. (a) Contrast-enhanced CT scan shows a 1.5-cm-diameter mass (arrow) in the right kidney. Biopsy findings confirmed that the tumor was an RCC. (b) Intraoperative US scan shows the isoechoic renal tumor (cursors) located anteriorly in the right kidney. (c) With US guidance, the electrode (arrow) was advanced into the tumor immediately before ablation. (d) US scan obtained during ablation of the tumor shows the hyperechoic zone (arrow) caused by radiofrequency ablation. This hyperechoic zone obscures the electrode and US detail of the treatment area. After nephrectomy, histologic examination of the specimen showed complete ablation of the tumor.

View larger version (118K): [in a new window]   Figure 3d.  Hyperechoic zone caused by radiofrequency ablation in a patient who was enrolled in a "treat and resect" study (20) of renal tumor ablation. (a) Contrast-enhanced CT scan shows a 1.5-cm-diameter mass (arrow) in the right kidney. Biopsy findings confirmed that the tumor was an RCC. (b) Intraoperative US scan shows the isoechoic renal tumor (cursors) located anteriorly in the right kidney. (c) With US guidance, the electrode (arrow) was advanced into the tumor immediately before ablation. (d) US scan obtained during ablation of the tumor shows the hyperechoic zone (arrow) caused by radiofrequency ablation. This hyperechoic zone obscures the electrode and US detail of the treatment area. After nephrectomy, histologic examination of the specimen showed complete ablation of the tumor.

View larger version (154K): [in a new window]   Figure 4a.  Treatment of a biopsy-proved 3-cm-diameter RCC in a patient with heart failure. (a) Unenhanced CT scan shows a solid, exophytic tumor arising from the right kidney. (b) Contrast-enhanced CT scan obtained at the same level as a shows an enhancing solid RCC (arrow). (c) Unenhanced CT scan obtained 1 month later shows the electrode advanced into the tumor for treatment. (d) Contrast-enhanced CT scan obtained 7 months after ablation shows that the tumor has decreased in size. There is no longer any detectable enhancement. These findings indicate successful tumor ablation.

View larger version (152K): [in a new window]   Figure 4b.  Treatment of a biopsy-proved 3-cm-diameter RCC in a patient with heart failure. (a) Unenhanced CT scan shows a solid, exophytic tumor arising from the right kidney. (b) Contrast-enhanced CT scan obtained at the same level as a shows an enhancing solid RCC (arrow). (c) Unenhanced CT scan obtained 1 month later shows the electrode advanced into the tumor for treatment. (d) Contrast-enhanced CT scan obtained 7 months after ablation shows that the tumor has decreased in size. There is no longer any detectable enhancement. These findings indicate successful tumor ablation.

View larger version (156K): [in a new window]   Figure 4c.  Treatment of a biopsy-proved 3-cm-diameter RCC in a patient with heart failure. (a) Unenhanced CT scan shows a solid, exophytic tumor arising from the right kidney. (b) Contrast-enhanced CT scan obtained at the same level as a shows an enhancing solid RCC (arrow). (c) Unenhanced CT scan obtained 1 month later shows the electrode advanced into the tumor for treatment. (d) Contrast-enhanced CT scan obtained 7 months after ablation shows that the tumor has decreased in size. There is no longer any detectable enhancement. These findings indicate successful tumor ablation.

View larger version (175K): [in a new window]   Figure 4d.  Treatment of a biopsy-proved 3-cm-diameter RCC in a patient with heart failure. (a) Unenhanced CT scan shows a solid, exophytic tumor arising from the right kidney. (b) Contrast-enhanced CT scan obtained at the same level as a shows an enhancing solid RCC (arrow). (c) Unenhanced CT scan obtained 1 month later shows the electrode advanced into the tumor for treatment. (d) Contrast-enhanced CT scan obtained 7 months after ablation shows that the tumor has decreased in size. There is no longer any detectable enhancement. These findings indicate successful tumor ablation.

View larger version (147K): [in a new window]   Figure 5a.  Radiofrequency ablation of a biopsy-proved RCC in an elderly patient with coronary artery disease. (a) Unenhanced CT scan obtained immediately before ablation, with the patient in prone position, shows an exophytic 4.5-cm-diameter tumor (arrow) in the left kidney. (b) Unenhanced CT scan obtained during ablation shows the electrode tip positioned within the RCC. Multiple tines can be seen deployed from the electrode. There is some hemorrhage from the tumor puncture surrounding the mass. (c) Gadolinium-enhanced MR image (three-dimensional dynamic image, repetition time msec/echo time msec = 4.6/0.956) obtained 5 weeks after ablation shows residual enhancing tumor (arrows) in the periphery of the treated RCC. (d) Unenhanced CT scan obtained 3 months after a second ablation session shows that the tumor is slightly heterogeneous and has higher attenuation than expected for an uncomplicated tumor. This finding is believed to reflect coagulation necrosis in the tumor induced by ablation. The peritumor stranding is an expected finding after ablation. (e) Contrast-enhanced CT scan at the same level as d shows no enhancement in the retreated tumor. This finding indicates successful tumor ablation.

View larger version (164K): [in a new window]   Figure 5b.  Radiofrequency ablation of a biopsy-proved RCC in an elderly patient with coronary artery disease. (a) Unenhanced CT scan obtained immediately before ablation, with the patient in prone position, shows an exophytic 4.5-cm-diameter tumor (arrow) in the left kidney. (b) Unenhanced CT scan obtained during ablation shows the electrode tip positioned within the RCC. Multiple tines can be seen deployed from the electrode. There is some hemorrhage from the tumor puncture surrounding the mass. (c) Gadolinium-enhanced MR image (three-dimensional dynamic image, repetition time msec/echo time msec = 4.6/0.956) obtained 5 weeks after ablation shows residual enhancing tumor (arrows) in the periphery of the treated RCC. (d) Unenhanced CT scan obtained 3 months after a second ablation session shows that the tumor is slightly heterogeneous and has higher attenuation than expected for an uncomplicated tumor. This finding is believed to reflect coagulation necrosis in the tumor induced by ablation. The peritumor stranding is an expected finding after ablation. (e) Contrast-enhanced CT scan at the same level as d shows no enhancement in the retreated tumor. This finding indicates successful tumor ablation.

View larger version (127K): [in a new window]   Figure 5c.  Radiofrequency ablation of a biopsy-proved RCC in an elderly patient with coronary artery disease. (a) Unenhanced CT scan obtained immediately before ablation, with the patient in prone position, shows an exophytic 4.5-cm-diameter tumor (arrow) in the left kidney. (b) Unenhanced CT scan obtained during ablation shows the electrode tip positioned within the RCC. Multiple tines can be seen deployed from the electrode. There is some hemorrhage from the tumor puncture surrounding the mass. (c) Gadolinium-enhanced MR image (three-dimensional dynamic image, repetition time msec/echo time msec = 4.6/0.956) obtained 5 weeks after ablation shows residual enhancing tumor (arrows) in the periphery of the treated RCC. (d) Unenhanced CT scan obtained 3 months after a second ablation session shows that the tumor is slightly heterogeneous and has higher attenuation than expected for an uncomplicated tumor. This finding is believed to reflect coagulation necrosis in the tumor induced by ablation. The peritumor stranding is an expected finding after ablation. (e) Contrast-enhanced CT scan at the same level as d shows no enhancement in the retreated tumor. This finding indicates successful tumor ablation.

View larger version (165K): [in a new window]   Figure 5d.  Radiofrequency ablation of a biopsy-proved RCC in an elderly patient with coronary artery disease. (a) Unenhanced CT scan obtained immediately before ablation, with the patient in prone position, shows an exophytic 4.5-cm-diameter tumor (arrow) in the left kidney. (b) Unenhanced CT scan obtained during ablation shows the electrode tip positioned within the RCC. Multiple tines can be seen deployed from the electrode. There is some hemorrhage from the tumor puncture surrounding the mass. (c) Gadolinium-enhanced MR image (three-dimensional dynamic image, repetition time msec/echo time msec = 4.6/0.956) obtained 5 weeks after ablation shows residual enhancing tumor (arrows) in the periphery of the treated RCC. (d) Unenhanced CT scan obtained 3 months after a second ablation session shows that the tumor is slightly heterogeneous and has higher attenuation than expected for an uncomplicated tumor. This finding is believed to reflect coagulation necrosis in the tumor induced by ablation. The peritumor stranding is an expected finding after ablation. (e) Contrast-enhanced CT scan at the same level as d shows no enhancement in the retreated tumor. This finding indicates successful tumor ablation.

View larger version (186K): [in a new window]   Figure 5e.  Radiofrequency ablation of a biopsy-proved RCC in an elderly patient with coronary artery disease. (a) Unenhanced CT scan obtained immediately before ablation, with the patient in prone position, shows an exophytic 4.5-cm-diameter tumor (arrow) in the left kidney. (b) Unenhanced CT scan obtained during ablation shows the electrode tip positioned within the RCC. Multiple tines can be seen deployed from the electrode. There is some hemorrhage from the tumor puncture surrounding the mass. (c) Gadolinium-enhanced MR image (three-dimensional dynamic image, repetition time msec/echo time msec = 4.6/0.956) obtained 5 weeks after ablation shows residual enhancing tumor (arrows) in the periphery of the treated RCC. (d) Unenhanced CT scan obtained 3 months after a second ablation session shows that the tumor is slightly heterogeneous and has higher attenuation than expected for an uncomplicated tumor. This finding is believed to reflect coagulation necrosis in the tumor induced by ablation. The peritumor stranding is an expected finding after ablation. (e) Contrast-enhanced CT scan at the same level as d shows no enhancement in the retreated tumor. This finding indicates successful tumor ablation.

View larger version (103K): [in a new window]   Figure 6a.  Local tumor recurrence after radiofrequency ablation of RCC in a patient with renal insufficiency. (a) Gadolinium-enhanced T1-weighted MR image (4.368/0.972) shows a 5.2-cm-diameter, enhancing exophytic tumor (arrow) in the left kidney. (b) Unenhanced CT scan obtained with the patient prone shows placement of the electrode in the tumor. An MR image obtained 2 months later (not shown) demonstrated no evidence of tumor enhancement. (c) T2-weighted MR image (45/4.652) obtained 1 year after ablation shows enlargement of the left renal vein with solid tissue within its lumen (arrow). (d) Gadolinium-enhanced T1-weighted MR image (4.368/0.972) shows enhancement of the tumor thrombus and of tissue in the tumor bed (arrows), findings that indicate recurrence of RCC. Examination of the resected specimen showed clear cell adenocarcinoma in the kidney and left renal vein.

View larger version (127K): [in a new window]   Figure 6b.  Local tumor recurrence after radiofrequency ablation of RCC in a patient with renal insufficiency. (a) Gadolinium-enhanced T1-weighted MR image (4.368/0.972) shows a 5.2-cm-diameter, enhancing exophytic tumor (arrow) in the left kidney. (b) Unenhanced CT scan obtained with the patient prone shows placement of the electrode in the tumor. An MR image obtained 2 months later (not shown) demonstrated no evidence of tumor enhancement. (c) T2-weighted MR image (45/4.652) obtained 1 year after ablation shows enlargement of the left renal vein with solid tissue within its lumen (arrow). (d) Gadolinium-enhanced T1-weighted MR image (4.368/0.972) shows enhancement of the tumor thrombus and of tissue in the tumor bed (arrows), findings that indicate recurrence of RCC. Examination of the resected specimen showed clear cell adenocarcinoma in the kidney and left renal vein.

View larger version (137K): [in a new window]   Figure 6c.  Local tumor recurrence after radiofrequency ablation of RCC in a patient with renal insufficiency. (a) Gadolinium-enhanced T1-weighted MR image (4.368/0.972) shows a 5.2-cm-diameter, enhancing exophytic tumor (arrow) in the left kidney. (b) Unenhanced CT scan obtained with the patient prone shows placement of the electrode in the tumor. An MR image obtained 2 months later (not shown) demonstrated no evidence of tumor enhancement. (c) T2-weighted MR image (45/4.652) obtained 1 year after ablation shows enlargement of the left renal vein with solid tissue within its lumen (arrow). (d) Gadolinium-enhanced T1-weighted MR image (4.368/0.972) shows enhancement of the tumor thrombus and of tissue in the tumor bed (arrows), findings that indicate recurrence of RCC. Examination of the resected specimen showed clear cell adenocarcinoma in the kidney and left renal vein.

View larger version (159K): [in a new window]   Figure 6d.  Local tumor recurrence after radiofrequency ablation of RCC in a patient with renal insufficiency. (a) Gadolinium-enhanced T1-weighted MR image (4.368/0.972) shows a 5.2-cm-diameter, enhancing exophytic tumor (arrow) in the left kidney. (b) Unenhanced CT scan obtained with the patient prone shows placement of the electrode in the tumor. An MR image obtained 2 months later (not shown) demonstrated no evidence of tumor enhancement. (c) T2-weighted MR image (45/4.652) obtained 1 year after ablation shows enlargement of the left renal vein with solid tissue within its lumen (arrow). (d) Gadolinium-enhanced T1-weighted MR image (4.368/0.972) shows enhancement of the tumor thrombus and of tissue in the tumor bed (arrows), findings that indicate recurrence of RCC. Examination of the resected specimen showed clear cell adenocarcinoma in the kidney and left renal vein.

View larger version (128K): [in a new window]   Figure 7a.  Technique for displacing adjacent organs before radiofrequency ablation of a renal tumor. (a) Contrast-enhanced CT scan shows a 1-cm-diameter enhancing, exophytic tumor (arrow) arising anteriorly from the left kidney. The small intestine is immediately adjacent to the tumor. The patient was referred for radiofrequency ablation because of his severe emphysema. (b) CT scan obtained with the patient in the prone position for the ablation procedure shows that the tumor (arrow) has a calcified rim and is adjacent to a loop of small intestine, which increases the risk of thermal damage to the intestine. (c) With CT guidance, a 22-gauge needle was advanced into the perinephric space. Fifty milliliters of sterile water was injected at this point to displace the intestine away from the tumor and thus avoid thermal damage to the small intestine during ablation. (d) Repeat CT scan obtained after the injection of sterile water shows that there was sufficient space between the tumor and small intestine to advance the injection needle farther. This scan illustrates the needle position after advancing it farther. An additional 100 mL of sterile water was injected at this point to increase the space between the tumor and the intestine. (e) CT scan obtained after sterile water injection shows the electrode positioned to bisect the exophytic tumor. Ablation was performed with the electrode in this position. (f) Contrast-enhanced CT scan obtained immediately after ablation shows no enhancement of the tumor or of a thin rim of adjacent kidney (arrows). This finding indicates successful ablation of the tumor and the adjacent margin of kidney.

View larger version (116K): [in a new window]   Figure 7b.  Technique for displacing adjacent organs before radiofrequency ablation of a renal tumor. (a) Contrast-enhanced CT scan shows a 1-cm-diameter enhancing, exophytic tumor (arrow) arising anteriorly from the left kidney. The small intestine is immediately adjacent to the tumor. The patient was referred for radiofrequency ablation because of his severe emphysema. (b) CT scan obtained with the patient in the prone position for the ablation procedure shows that the tumor (arrow) has a calcified rim and is adjacent to a loop of small intestine, which increases the risk of thermal damage to the intestine. (c) With CT guidance, a 22-gauge needle was advanced into the perinephric space. Fifty milliliters of sterile water was injected at this point to displace the intestine away from the tumor and thus avoid thermal damage to the small intestine during ablation. (d) Repeat CT scan obtained after the injection of sterile water shows that there was sufficient space between the tumor and small intestine to advance the injection needle farther. This scan illustrates the needle position after advancing it farther. An additional 100 mL of sterile water was injected at this point to increase the space between the tumor and the intestine. (e) CT scan obtained after sterile water injection shows the electrode positioned to bisect the exophytic tumor. Ablation was performed with the electrode in this position. (f) Contrast-enhanced CT scan obtained immediately after ablation shows no enhancement of the tumor or of a thin rim of adjacent kidney (arrows). This finding indicates successful ablation of the tumor and the adjacent margin of kidney.

View larger version (124K): [in a new window]   Figure 7c.  Technique for displacing adjacent organs before radiofrequency ablation of a renal tumor. (a) Contrast-enhanced CT scan shows a 1-cm-diameter enhancing, exophytic tumor (arrow) arising anteriorly from the left kidney. The small intestine is immediately adjacent to the tumor. The patient was referred for radiofrequency ablation because of his severe emphysema. (b) CT scan obtained with the patient in the prone position for the ablation procedure shows that the tumor (arrow) has a calcified rim and is adjacent to a loop of small intestine, which increases the risk of thermal damage to the intestine. (c) With CT guidance, a 22-gauge needle was advanced into the perinephric space. Fifty milliliters of sterile water was injected at this point to displace the intestine away from the tumor and thus avoid thermal damage to the small intestine during ablation. (d) Repeat CT scan obtained after the injection of sterile water shows that there was sufficient space between the tumor and small intestine to advance the injection needle farther. This scan illustrates the needle position after advancing it farther. An additional 100 mL of sterile water was injected at this point to increase the space between the tumor and the intestine. (e) CT scan obtained after sterile water injection shows the electrode positioned to bisect the exophytic tumor. Ablation was performed with the electrode in this position. (f) Contrast-enhanced CT scan obtained immediately after ablation shows no enhancement of the tumor or of a thin rim of adjacent kidney (arrows). This finding indicates successful ablation of the tumor and the adjacent margin of kidney.

View larger version (123K): [in a new window]   Figure 7d.  Technique for displacing adjacent organs before radiofrequency ablation of a renal tumor. (a) Contrast-enhanced CT scan shows a 1-cm-diameter enhancing, exophytic tumor (arrow) arising anteriorly from the left kidney. The small intestine is immediately adjacent to the tumor. The patient was referred for radiofrequency ablation because of his severe emphysema. (b) CT scan obtained with the patient in the prone position for the ablation procedure shows that the tumor (arrow) has a calcified rim and is adjacent to a loop of small intestine, which increases the risk of thermal damage to the intestine. (c) With CT guidance, a 22-gauge needle was advanced into the perinephric space. Fifty milliliters of sterile water was injected at this point to displace the intestine away from the tumor and thus avoid thermal damage to the small intestine during ablation. (d) Repeat CT scan obtained after the injection of sterile water shows that there was sufficient space between the tumor and small intestine to advance the injection needle farther. This scan illustrates the needle position after advancing it farther. An additional 100 mL of sterile water was injected at this point to increase the space between the tumor and the intestine. (e) CT scan obtained after sterile water injection shows the electrode positioned to bisect the exophytic tumor. Ablation was performed with the electrode in this position. (f) Contrast-enhanced CT scan obtained immediately after ablation shows no enhancement of the tumor or of a thin rim of adjacent kidney (arrows). This finding indicates successful ablation of the tumor and the adjacent margin of kidney.

View larger version (126K): [in a new window]   Figure 7e.  Technique for displacing adjacent organs before radiofrequency ablation of a renal tumor. (a) Contrast-enhanced CT scan shows a 1-cm-diameter enhancing, exophytic tumor (arrow) arising anteriorly from the left kidney. The small intestine is immediately adjacent to the tumor. The patient was referred for radiofrequency ablation because of his severe emphysema. (b) CT scan obtained with the patient in the prone position for the ablation procedure shows that the tumor (arrow) has a calcified rim and is adjacent to a loop of small intestine, which increases the risk of thermal damage to the intestine. (c) With CT guidance, a 22-gauge needle was advanced into the perinephric space. Fifty milliliters of sterile water was injected at this point to displace the intestine away from the tumor and thus avoid thermal damage to the small intestine during ablation. (d) Repeat CT scan obtained after the injection of sterile water shows that there was sufficient space between the tumor and small intestine to advance the injection needle farther. This scan illustrates the needle position after advancing it farther. An additional 100 mL of sterile water was injected at this point to increase the space between the tumor and the intestine. (e) CT scan obtained after sterile water injection shows the electrode positioned to bisect the exophytic tumor. Ablation was performed with the electrode in this position. (f) Contrast-enhanced CT scan obtained immediately after ablation shows no enhancement of the tumor or of a thin rim of adjacent kidney (arrows). This finding indicates successful ablation of the tumor and the adjacent margin of kidney.

View larger version (138K): [in a new window]   Figure 7f.  Technique for displacing adjacent organs before radiofrequency ablation of a renal tumor. (a) Contrast-enhanced CT scan shows a 1-cm-diameter enhancing, exophytic tumor (arrow) arising anteriorly from the left kidney. The small intestine is immediately adjacent to the tumor. The patient was referred for radiofrequency ablation because of his severe emphysema. (b) CT scan obtained with the patient in the prone position for the ablation procedure shows that the tumor (arrow) has a calcified rim and is adjacent to a loop of small intestine, which increases the risk of thermal damage to the intestine. (c) With CT guidance, a 22-gauge needle was advanced into the perinephric space. Fifty milliliters of sterile water was injected at this point to displace the intestine away from the tumor and thus avoid thermal damage to the small intestine during ablation. (d) Repeat CT scan obtained after the injection of sterile water shows that there was sufficient space between the tumor and small intestine to advance the injection needle farther. This scan illustrates the needle position after advancing it farther. An additional 100 mL of sterile water was injected at this point to increase the space between the tumor and the intestine. (e) CT scan obtained after sterile water injection shows the electrode positioned to bisect the exophytic tumor. Ablation was performed with the electrode in this position. (f) Contrast-enhanced CT scan obtained immediately after ablation shows no enhancement of the tumor or of a thin rim of adjacent kidney (arrows). This finding indicates successful ablation of the tumor and the adjacent margin of kidney.

View larger version (134K): [in a new window]   Figure 8a.  Perinephric hematoma caused by radiofrequency ablation of an RCC in a 40-year-old man. The patient was referred for ablation because of his comorbidities, which included severe hepatic cirrhosis and chronic hepatitis. (a) Contrast-enhanced CT scan shows a 2-cm-diameter tumor in the left kidney. (b) CT scan obtained with the patient in a prone position shows the electrode advanced into the tumor. Ablation was performed. (c) Contrast-enhanced CT scan obtained immediately after ablation shows a perirenal hematoma with a site of active bleeding. The patient was observed in the hospital overnight and, owing to a decreasing hematocrit level, was transfused with 2 units of blood. His hematocrit level stabilized, and he was discharged the following day in his normal state of health. Although perirenal hematomas are expected after ablation, they rarely necessitate treatment.

View larger version (125K): [in a new window]   Figure 8b.  Perinephric hematoma caused by radiofrequency ablation of an RCC in a 40-year-old man. The patient was referred for ablation because of his comorbidities, which included severe hepatic cirrhosis and chronic hepatitis. (a) Contrast-enhanced CT scan shows a 2-cm-diameter tumor in the left kidney. (b) CT scan obtained with the patient in a prone position shows the electrode advanced into the tumor. Ablation was performed. (c) Contrast-enhanced CT scan obtained immediately after ablation shows a perirenal hematoma with a site of active bleeding. The patient was observed in the hospital overnight and, owing to a decreasing hematocrit level, was transfused with 2 units of blood. His hematocrit level stabilized, and he was discharged the following day in his normal state of health. Although perirenal hematomas are expected after ablation, they rarely necessitate treatment.

View larger version (135K): [in a new window]   Figure 8c.  Perinephric hematoma caused by radiofrequency ablation of an RCC in a 40-year-old man. The patient was referred for ablation because of his comorbidities, which included severe hepatic cirrhosis and chronic hepatitis. (a) Contrast-enhanced CT scan shows a 2-cm-diameter tumor in the left kidney. (b) CT scan obtained with the patient in a prone position shows the electrode advanced into the tumor. Ablation was performed. (c) Contrast-enhanced CT scan obtained immediately after ablation shows a perirenal hematoma with a site of active bleeding. The patient was observed in the hospital overnight and, owing to a decreasing hematocrit level, was transfused with 2 units of blood. His hematocrit level stabilized, and he was discharged the following day in his normal state of health. Although perirenal hematomas are expected after ablation, they rarely necessitate treatment.