DOI: 10.1148/rg.282075038
RadioGraphics 2008;28:379-390
© RSNA, 2008
Spectrum of CT Findings after Radiofrequency Ablation of Hepatic Tumors1
Mi-hyun Park, MD,
Hyunchul Rhim, MD,
Young-sun Kim, MD,
Dongil Choi, MD,
Hyo K. Lim, MD, and
Won Jae Lee, MD
1 From the Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-dong, Kangnam-ku, Seoul 135–710, Korea. Presented as an education exhibit at the 2006 RSNA Annual Meeting. Received March 5, 2007; revision requested April 2 and received May 4; accepted June 15. All authors have no financial relationships to disclose.
Address correspondence to H.R. (e-mail: forest{at}smc.samsung.co.kr).
 |
Abstract
|
|---|
Image-guided radiofrequency (RF) ablation has been used to treat both resectable and nonresectable hepatic tumors. A precise imaging assessment of the therapeutic response and of any complications is mandatory after ablation. Contrast material–enhanced ultrasonography, computed tomography (CT), and magnetic resonance imaging all may be useful for this assessment. At most institutions, a three-phase contrast-enhanced CT examination is performed immediately or within 1 month after RF ablation to assess the technical success of treatment. If ablation was technically successful, three-phase CT may be repeated at 3-month intervals for evaluation of tumor recurrence. The typical CT finding in the zone subjected to RF ablation is an area of low attenuation that encompasses the tumor and an ablative margin. However, the appearance of the ablative zone may vary greatly, depending on the success of treatment and the time elapsed after the procedure. Ringlike enhancement representing benign reactive hyperemia around the ablation zone, central high-attenuation areas representing greater cellular disruption, and tiny air bubbles frequently are seen at immediate follow-up CT but usually have disappeared by the first or second follow-up examination. The successfully ablated zone gradually involutes. The appearance of the zone differs when residual tumor tissue or local tumor progression is present. Immediate or delayed complications also may be seen at follow-up CT. Radiologists must be familiar with both typical and atypical CT findings and their clinical significance.
© RSNA, 2008
|
Introduction
|
|---|
Image-guided radiofrequency (RF) ablation has been used increasingly during the past decade to treat both resectable and nonresectable hepatic tumors (1–13). Follow-up imaging studies are needed to evaluate the results of RF ablation and to identify any complications. Various imaging modalities, such as contrast material–enhanced ultrasonography (US), computed tomography (CT), and magnetic resonance (MR) imaging may be used for follow-up evaluations (14–20). At most institutions, contrast-enhanced CT is used for this purpose (14–16). If the results of CT are inconclusive, combined fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) and CT may be performed when the presence of residual tumor tissue or local tumor progression is suspected (21–24). The three-phase CT technique is used with delays of 30, 60, and 180 seconds after contrast material injection. At our institution, a total of 120 mL of a nonionic contrast agent is administered intravenously at a rate of 3 mL/sec with a power injector. All CT examinations are performed with a collimation of 7 mm and a table speed of 7 mm/sec. At most institutions, three-phase contrast-enhanced CT is performed immediately or within 1 month to assess the technical success of RF ablation. At our institution, if the treatment was technically successful, three-phase CT is repeated at 3-month intervals for evaluation of tumor recurrence.
The appearance of the ablated zone varies greatly, depending on the degree of success and the time that has elapsed after RF ablation. Radiologists who are responsible for the interpretation of follow-up CT images after RF ablation must be able to recognize typical chronological changes in the ablated zone as well as atypical findings (Fig 1). The article provides a review of both typical and atypical findings that are commonly seen at follow-up CT after RF ablation.
View larger version (10K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 1a. Schemas of the RF ablation zone. HCC = hepatocellular carcinoma, META = metastasis, Pre-Tx = index tumor. (a) Schema shows successful ablation and subsequent involution of the ablation zone. At initial follow-up CT (Immediate), the zone covers the index tumor (black-filled dotted gray circle) and an ablative margin (black ring around dotted gray circle) and is surrounded by a ring of enhancement (solid gray circle) that usually disappears by 1-month follow-up CT. The ablation zone involutes gradually over the next several years. (b) Schema shows incomplete ablation, with a crescent-shaped remnant of tumor tissue (*) at the margin of the ablation zone. If the volume of residual tumor tissue is minimal, it is difficult to differentiate from the enhanced ring of benign tissue surrounding the ablation zone on CT images obtained immediately after ablation. (c) Schema shows tumor recurrence after incomplete ablation. If the ablative margin is not wide enough, a small nodular tumor (*) may appear adjacent to the margin on follow-up CT images, a finding considered indicative of local tumor progression.
|
|
View larger version (27K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 1b. Schemas of the RF ablation zone. HCC = hepatocellular carcinoma, META = metastasis, Pre-Tx = index tumor. (a) Schema shows successful ablation and subsequent involution of the ablation zone. At initial follow-up CT (Immediate), the zone covers the index tumor (black-filled dotted gray circle) and an ablative margin (black ring around dotted gray circle) and is surrounded by a ring of enhancement (solid gray circle) that usually disappears by 1-month follow-up CT. The ablation zone involutes gradually over the next several years. (b) Schema shows incomplete ablation, with a crescent-shaped remnant of tumor tissue (*) at the margin of the ablation zone. If the volume of residual tumor tissue is minimal, it is difficult to differentiate from the enhanced ring of benign tissue surrounding the ablation zone on CT images obtained immediately after ablation. (c) Schema shows tumor recurrence after incomplete ablation. If the ablative margin is not wide enough, a small nodular tumor (*) may appear adjacent to the margin on follow-up CT images, a finding considered indicative of local tumor progression.
|
|
View larger version (14K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 1c. Schemas of the RF ablation zone. HCC = hepatocellular carcinoma, META = metastasis, Pre-Tx = index tumor. (a) Schema shows successful ablation and subsequent involution of the ablation zone. At initial follow-up CT (Immediate), the zone covers the index tumor (black-filled dotted gray circle) and an ablative margin (black ring around dotted gray circle) and is surrounded by a ring of enhancement (solid gray circle) that usually disappears by 1-month follow-up CT. The ablation zone involutes gradually over the next several years. (b) Schema shows incomplete ablation, with a crescent-shaped remnant of tumor tissue (*) at the margin of the ablation zone. If the volume of residual tumor tissue is minimal, it is difficult to differentiate from the enhanced ring of benign tissue surrounding the ablation zone on CT images obtained immediately after ablation. (c) Schema shows tumor recurrence after incomplete ablation. If the ablative margin is not wide enough, a small nodular tumor (*) may appear adjacent to the margin on follow-up CT images, a finding considered indicative of local tumor progression.
|
|
|
Typical CT Features of Successful Ablation
|
|---|
First Follow-up Examination (Immediately after Ablation)
At the initial follow-up CT examination, the ablation zone typically appears as a nonenhancing area of low attenuation, a finding that represents coagulation necrosis (Fig 2). The area of low attenuation should completely cover the entire index tumor and the ablative margin, which is defined as the ablated hepatic parenchyma around the index tumor. The thickness of the ablative margin must be at least 0.5 cm for ablation of the index tumor to be considered complete. In other words, the total volume of the ablated tumor and the ablative margin must be larger than that of the index tumor. If it is not, then ablation of the index tumor is incomplete (14–18).
View larger version (140K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 2a. Typical imaging appearance of the ablation zone after complete RF ablation for hepatocellular carcinoma in the liver of a 59-year-old man. (a) T2-weighted MR image obtained before ablation shows a 2-cm index tumor in the right hepatic lobe. (b) Axial arterial phase CT image obtained 20 minutes after ablation shows coverage of the index tumor with a sufficient ablative margin and a surrounding ring of benign enhancement. Note the central area of high attenuation. (c) Axial CT image from 1-month follow-up shows the same central area of high attenuation depicted in b. (d) CT image from 1-year follow-up depicts involution of the ablation zone, with continuing high attenuation at its center.
|
|
View larger version (123K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 2b. Typical imaging appearance of the ablation zone after complete RF ablation for hepatocellular carcinoma in the liver of a 59-year-old man. (a) T2-weighted MR image obtained before ablation shows a 2-cm index tumor in the right hepatic lobe. (b) Axial arterial phase CT image obtained 20 minutes after ablation shows coverage of the index tumor with a sufficient ablative margin and a surrounding ring of benign enhancement. Note the central area of high attenuation. (c) Axial CT image from 1-month follow-up shows the same central area of high attenuation depicted in b. (d) CT image from 1-year follow-up depicts involution of the ablation zone, with continuing high attenuation at its center.
|
|
View larger version (106K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 2c. Typical imaging appearance of the ablation zone after complete RF ablation for hepatocellular carcinoma in the liver of a 59-year-old man. (a) T2-weighted MR image obtained before ablation shows a 2-cm index tumor in the right hepatic lobe. (b) Axial arterial phase CT image obtained 20 minutes after ablation shows coverage of the index tumor with a sufficient ablative margin and a surrounding ring of benign enhancement. Note the central area of high attenuation. (c) Axial CT image from 1-month follow-up shows the same central area of high attenuation depicted in b. (d) CT image from 1-year follow-up depicts involution of the ablation zone, with continuing high attenuation at its center.
|
|
View larger version (103K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 2d. Typical imaging appearance of the ablation zone after complete RF ablation for hepatocellular carcinoma in the liver of a 59-year-old man. (a) T2-weighted MR image obtained before ablation shows a 2-cm index tumor in the right hepatic lobe. (b) Axial arterial phase CT image obtained 20 minutes after ablation shows coverage of the index tumor with a sufficient ablative margin and a surrounding ring of benign enhancement. Note the central area of high attenuation. (c) Axial CT image from 1-month follow-up shows the same central area of high attenuation depicted in b. (d) CT image from 1-year follow-up depicts involution of the ablation zone, with continuing high attenuation at its center.
|
|
Another frequent finding is a uniform peripheral rim of enhancement that envelops the ablation zone on contrast-enhanced CT images obtained immediately after treatment (Figs 2, 3). This finding is considered indicative of a benign physiologic response to thermal injury, and it frequently disappears over time (15–18). Lim et al reported this transient CT finding in 79% of cases and noted that it usually disappeared by the 1-month follow-up CT examination (18). The zone of ablation also often contains a central area of high attenuation along the electrode needle tract on immediate follow-up CT images (Fig 2). This area of increased attenuation, which is believed to represent greater cellular disruption (15,16), usually has disappeared by the time of the next follow-up CT examination.
View larger version (98K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 3a. Typical CT findings in the ablation zone after RF ablation for hepatocellular carcinoma in the liver of a 50-year-old woman. (a) Axial arterial phase CT image obtained before ablation shows a 2-cm index tumor in segment VII. (b) Axial arterial phase CT image obtained 20 minutes after ablation shows uniform peripheral enhancement (arrowheads) around the ablation zone and tiny air bubbles (arrow) within it. (c) Axial CT image obtained at 1-month follow-up shows the disappearance of both the peripheral enhancement and air bubbles.
|
|
View larger version (112K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 3b. Typical CT findings in the ablation zone after RF ablation for hepatocellular carcinoma in the liver of a 50-year-old woman. (a) Axial arterial phase CT image obtained before ablation shows a 2-cm index tumor in segment VII. (b) Axial arterial phase CT image obtained 20 minutes after ablation shows uniform peripheral enhancement (arrowheads) around the ablation zone and tiny air bubbles (arrow) within it. (c) Axial CT image obtained at 1-month follow-up shows the disappearance of both the peripheral enhancement and air bubbles.
|
|
View larger version (107K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 3c. Typical CT findings in the ablation zone after RF ablation for hepatocellular carcinoma in the liver of a 50-year-old woman. (a) Axial arterial phase CT image obtained before ablation shows a 2-cm index tumor in segment VII. (b) Axial arterial phase CT image obtained 20 minutes after ablation shows uniform peripheral enhancement (arrowheads) around the ablation zone and tiny air bubbles (arrow) within it. (c) Axial CT image obtained at 1-month follow-up shows the disappearance of both the peripheral enhancement and air bubbles.
|
|
In addition, tiny air bubbles produced during ablation may be seen at immediate follow-up CT and should not be confused with a hepatic abscess (17–20). These air bubbles also usually resolve within 1 month (Fig 3). The shape of the ablation zone usually appears round or oval, depending on the electrode type used in the procedure (14,17, 18). However, when the index tumor is located between large branches of hepatic vessels, the shape of the zone may be irregular because of a heat-sink effect from blood flow (Fig 4).
View larger version (136K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 4a. Irregularly shaped ablation zone in the liver of a 39-year-old man who underwent RF ablation for hepatocellular carcinoma. (a) Arterial phase CT image obtained before ablation shows a 1.6-cm index tumor (arrow) that extends between the right hepatic veins (arrowheads). (b) Portal venous phase CT image obtained at 1-month follow-up after ablation shows a triangular ablation zone (arrow) that abuts the hepatic veins (arrowheads). The unusual shape of the zone is due to the heat-sink effect of blood flowing through the hepatic vessels. (c) CT image obtained 3 years later shows nearly complete involution of the ablation zone (arrow).
|
|
View larger version (145K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 4b. Irregularly shaped ablation zone in the liver of a 39-year-old man who underwent RF ablation for hepatocellular carcinoma. (a) Arterial phase CT image obtained before ablation shows a 1.6-cm index tumor (arrow) that extends between the right hepatic veins (arrowheads). (b) Portal venous phase CT image obtained at 1-month follow-up after ablation shows a triangular ablation zone (arrow) that abuts the hepatic veins (arrowheads). The unusual shape of the zone is due to the heat-sink effect of blood flowing through the hepatic vessels. (c) CT image obtained 3 years later shows nearly complete involution of the ablation zone (arrow).
|
|
View larger version (136K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 4c. Irregularly shaped ablation zone in the liver of a 39-year-old man who underwent RF ablation for hepatocellular carcinoma. (a) Arterial phase CT image obtained before ablation shows a 1.6-cm index tumor (arrow) that extends between the right hepatic veins (arrowheads). (b) Portal venous phase CT image obtained at 1-month follow-up after ablation shows a triangular ablation zone (arrow) that abuts the hepatic veins (arrowheads). The unusual shape of the zone is due to the heat-sink effect of blood flowing through the hepatic vessels. (c) CT image obtained 3 years later shows nearly complete involution of the ablation zone (arrow).
|
|
Second Follow-up Examination (1 Month after Ablation)
At 1-month follow-up CT, the zone of RF ablation appears as a well-defined area of low attenuation without peripheral enhancement. The ablation zone typically involutes gradually (Fig 4), but the rate of involution varies from case to case. Lim et al reported a pattern of gradually decreasing volume in the ablation zone over time in patients who underwent RF ablation for hepatocellular carcinoma (Fig 5) (18).
View larger version (8K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 5. Graph shows the pattern of gradual decrease in the volume of the ablation zone over time in patients who underwent RF ablation for hepatocellular carcinoma. (Reprinted, with permission, from reference 18.)
|
|
|
Residual Tumor Tissue
|
|---|
A comparison of CT images obtained before RF ablation with CT images obtained immediately after ablation is essential to determine the technical success of the procedure. If the RF ablation zone on immediate follow-up CT images does not contain the entire index tumor identified at pre-treatment CT, residual tumor tissue is considered to be present, and additional treatment is needed. Residual tumor tissue appears as an enhancing nodular area within the ablation zone on immediate follow-up CT images (Fig 6). In cases with a hypovascular index tumor, the residual tumor tissue also may appear as a disruption of the smooth interface of the ablation zone with the surrounding hepatic parenchyma. It may be difficult to identify residual tumor tissue because of the peripheral enhancement that often is present around the ablation zone on immediate follow-up CT images. More eccentric and more focal enhancing features are more likely indicative of residual tumor tissue than of a benign cause of enhancement (15,18). If the findings in the ablation zone on immediate follow-up CT images are inconclusive, follow-up CT or MR imaging is necessary (14–20). Gadolinium-enhanced dynamic MR imaging is useful for detecting residual tumor tissue and local tumor progression and correlates well with contrast-enhanced CT (19,20). As a functional imaging modality, FDG PET/CT may be an important diagnostic method for early detection of residual tumor tissue and local tumor progression (21–24). The reported technical success rate for RF ablation of hepatic tumors is more than 80% (25–27), but the technical success of treatment in a particular case is influenced by factors such as tumor size and location.
View larger version (122K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 6a. Residual tumor tissue in the dome of the liver in a 53-year-old woman after RF ablation for hepatocellular carcinoma. (a) Arterial phase CT image obtained before ablation shows a 2.4-cm index tumor in liver segment VII. (b, c) Axial (b) and coronal (c) arterial phase CT images obtained 20 minutes after ablation depict an enhancing mass (arrow) in the superior aspect of the ablation zone, a finding indicative of residual tumor tissue. The tumor remnant subsequently was treated with transarterial chemoembolization.
|
|
View larger version (121K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 6b. Residual tumor tissue in the dome of the liver in a 53-year-old woman after RF ablation for hepatocellular carcinoma. (a) Arterial phase CT image obtained before ablation shows a 2.4-cm index tumor in liver segment VII. (b, c) Axial (b) and coronal (c) arterial phase CT images obtained 20 minutes after ablation depict an enhancing mass (arrow) in the superior aspect of the ablation zone, a finding indicative of residual tumor tissue. The tumor remnant subsequently was treated with transarterial chemoembolization.
|
|
View larger version (155K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 6c. Residual tumor tissue in the dome of the liver in a 53-year-old woman after RF ablation for hepatocellular carcinoma. (a) Arterial phase CT image obtained before ablation shows a 2.4-cm index tumor in liver segment VII. (b, c) Axial (b) and coronal (c) arterial phase CT images obtained 20 minutes after ablation depict an enhancing mass (arrow) in the superior aspect of the ablation zone, a finding indicative of residual tumor tissue. The tumor remnant subsequently was treated with transarterial chemoembolization.
|
|
|
Local Tumor Progression
|
|---|
Local tumor progression is defined as the appearance of residual unablated tumor tissue in the RF ablation zone at follow-up in patients in whom the index tumor was previously considered completely ablated (15). However, in many cases, it is difficult to differentiate between local tumor progression and the occurrence of a new tumor in the zone of ablation (15). The frequency of local tumor progression varies widely; progression reportedly has occurred in as few as 1.8% and as many as 56.9% of cases (25,28–35). Regular follow-up with CT is important for the detection of local tumor progression to facilitate timely treatment. At follow-up CT, local tumor progression appears as a newly developed focal enhancing lesion within an ablation zone in which the index hepatocellular carcinoma was previously considered to have been completely ablated (Fig 7). If the index tumor was hypovascular, any distortion in the smooth interface of the ablation zone or any increase in the size of the zone is considered indicative of local tumor progression (Fig 8).
View larger version (147K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 7a. Local tumor progression in a 59-year-old man after RF ablation for hepatocellular carcinoma. (a) Arterial phase CT image obtained before ablation shows a 2-cm index tumor in liver segment V. (b) Arterial phase CT image obtained 20 minutes after ablation shows that the ablation zone covers the index tumor, but the ablative margin is insufficient because of the location of the index tumor adjacent to the gallbladder. The ablation zone contains tiny air bubbles and a central area of high attenuation. The uniform peripheral enhancement that envelops the ablation zone was believed to represent benign change in normal ablated tissue. (c) Arterial phase CT image obtained 4 months later shows a newly developed enhancing mass (arrow) in the posterolateral aspect of the ablation zone, a finding indicative of local tumor progression. (d) Unenhanced CT image obtained after transarterial chemoembolization shows lipiodol uptake in the tumor.
|
|
View larger version (145K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 7b. Local tumor progression in a 59-year-old man after RF ablation for hepatocellular carcinoma. (a) Arterial phase CT image obtained before ablation shows a 2-cm index tumor in liver segment V. (b) Arterial phase CT image obtained 20 minutes after ablation shows that the ablation zone covers the index tumor, but the ablative margin is insufficient because of the location of the index tumor adjacent to the gallbladder. The ablation zone contains tiny air bubbles and a central area of high attenuation. The uniform peripheral enhancement that envelops the ablation zone was believed to represent benign change in normal ablated tissue. (c) Arterial phase CT image obtained 4 months later shows a newly developed enhancing mass (arrow) in the posterolateral aspect of the ablation zone, a finding indicative of local tumor progression. (d) Unenhanced CT image obtained after transarterial chemoembolization shows lipiodol uptake in the tumor.
|
|
View larger version (158K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 7c. Local tumor progression in a 59-year-old man after RF ablation for hepatocellular carcinoma. (a) Arterial phase CT image obtained before ablation shows a 2-cm index tumor in liver segment V. (b) Arterial phase CT image obtained 20 minutes after ablation shows that the ablation zone covers the index tumor, but the ablative margin is insufficient because of the location of the index tumor adjacent to the gallbladder. The ablation zone contains tiny air bubbles and a central area of high attenuation. The uniform peripheral enhancement that envelops the ablation zone was believed to represent benign change in normal ablated tissue. (c) Arterial phase CT image obtained 4 months later shows a newly developed enhancing mass (arrow) in the posterolateral aspect of the ablation zone, a finding indicative of local tumor progression. (d) Unenhanced CT image obtained after transarterial chemoembolization shows lipiodol uptake in the tumor.
|
|
View larger version (152K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 7d. Local tumor progression in a 59-year-old man after RF ablation for hepatocellular carcinoma. (a) Arterial phase CT image obtained before ablation shows a 2-cm index tumor in liver segment V. (b) Arterial phase CT image obtained 20 minutes after ablation shows that the ablation zone covers the index tumor, but the ablative margin is insufficient because of the location of the index tumor adjacent to the gallbladder. The ablation zone contains tiny air bubbles and a central area of high attenuation. The uniform peripheral enhancement that envelops the ablation zone was believed to represent benign change in normal ablated tissue. (c) Arterial phase CT image obtained 4 months later shows a newly developed enhancing mass (arrow) in the posterolateral aspect of the ablation zone, a finding indicative of local tumor progression. (d) Unenhanced CT image obtained after transarterial chemoembolization shows lipiodol uptake in the tumor.
|
|
View larger version (153K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 8a. Local tumor progression in a 44-year-old man after incomplete RF ablation for a hepatic metastasis from ascending colon cancer. (a) Portal phase CT image obtained before ablation shows a 2-cm index tumor in the right hepatic lobe. (b) Contrast-enhanced gray-scale US image obtained after ablation shows no evidence of vascularity in the ablation zone (arrows). (c) CT image obtained at 1-month follow-up shows a distortion in the smooth interface of the ablation zone (arrow), a finding suggestive of incomplete ablation of the tumor. (d) Portal phase CT image obtained 3 months later shows a mass (arrow) in the periphery of the ablation zone, a finding indicative of local tumor progression.
|
|
View larger version (170K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 8b. Local tumor progression in a 44-year-old man after incomplete RF ablation for a hepatic metastasis from ascending colon cancer. (a) Portal phase CT image obtained before ablation shows a 2-cm index tumor in the right hepatic lobe. (b) Contrast-enhanced gray-scale US image obtained after ablation shows no evidence of vascularity in the ablation zone (arrows). (c) CT image obtained at 1-month follow-up shows a distortion in the smooth interface of the ablation zone (arrow), a finding suggestive of incomplete ablation of the tumor. (d) Portal phase CT image obtained 3 months later shows a mass (arrow) in the periphery of the ablation zone, a finding indicative of local tumor progression.
|
|
View larger version (148K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 8c. Local tumor progression in a 44-year-old man after incomplete RF ablation for a hepatic metastasis from ascending colon cancer. (a) Portal phase CT image obtained before ablation shows a 2-cm index tumor in the right hepatic lobe. (b) Contrast-enhanced gray-scale US image obtained after ablation shows no evidence of vascularity in the ablation zone (arrows). (c) CT image obtained at 1-month follow-up shows a distortion in the smooth interface of the ablation zone (arrow), a finding suggestive of incomplete ablation of the tumor. (d) Portal phase CT image obtained 3 months later shows a mass (arrow) in the periphery of the ablation zone, a finding indicative of local tumor progression.
|
|
View larger version (139K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 8d. Local tumor progression in a 44-year-old man after incomplete RF ablation for a hepatic metastasis from ascending colon cancer. (a) Portal phase CT image obtained before ablation shows a 2-cm index tumor in the right hepatic lobe. (b) Contrast-enhanced gray-scale US image obtained after ablation shows no evidence of vascularity in the ablation zone (arrows). (c) CT image obtained at 1-month follow-up shows a distortion in the smooth interface of the ablation zone (arrow), a finding suggestive of incomplete ablation of the tumor. (d) Portal phase CT image obtained 3 months later shows a mass (arrow) in the periphery of the ablation zone, a finding indicative of local tumor progression.
|
|
|
Atypical CT Features of the RF Ablation Zone
|
|---|
In most patients, CT images of the ablation zone show the typical chronological changes described. The appearance of the zone differs when residual tumor or local tumor progression is present. Immediate or delayed complications and miscellaneous rare features may be observed in the ablation zone at follow-up CT. The physician who performed the RF ablation should be familiar with these atypical CT features to ensure proper management.
Hepatic Abscess
The presence of a hepatic abscess is a major complication of RF ablation. The prevalence of this problem has been reported to be 0.3%–2.0% (36–41). The clinical symptoms include a relatively persistent fever and pain. Because fever and pain are also common symptoms of postablation syndrome, the operator should be aware of the possibilities of postablation syndrome and hepatic abscesses. Persistent fever over 2 weeks may be indicative of a hepatic abscess (38). Risk factors for the development of an abscess include a bilioenteric anastomosis, the retention of iodized oil from previous transcatheter arterial chemoembolization, and diabetes mellitus (36–38). The CT features of an abscess in the ablation zone are similar to those of a hepatic abscess. They usually appear as low-attenuation lesions with peripherally enhancing rims in a characteristic layering pattern (Fig 9). Occasionally, air bubbles that were not depicted at immediate follow-up CT are depicted; these may be a sign of the formation of a hepatic abscess. Expansion of the RF ablation zone at follow-up CT also may be a sign of a hepatic abscess, especially if the patient has clinical symptoms.
View larger version (133K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 9a. Hepatic abscess in a 46-year-old man after RF ablation for hepatocellular carcinoma. (a) CT image, obtained because the patient had developed a high fever 7 days after ablation, shows gas bubbles in the ablation zone, findings indicative of an abscess. US-guided percutaneous drainage of the abscess was performed. (b) Follow-up CT image obtained 14 days later shows a remnant of the abscess with the drainage catheter. (c) Contrast-enhanced CT image obtained 8 months after ablation shows complete healing of the abscess and a small remnant of the ablation zone with retraction of the liver capsule.
|
|
View larger version (143K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 9b. Hepatic abscess in a 46-year-old man after RF ablation for hepatocellular carcinoma. (a) CT image, obtained because the patient had developed a high fever 7 days after ablation, shows gas bubbles in the ablation zone, findings indicative of an abscess. US-guided percutaneous drainage of the abscess was performed. (b) Follow-up CT image obtained 14 days later shows a remnant of the abscess with the drainage catheter. (c) Contrast-enhanced CT image obtained 8 months after ablation shows complete healing of the abscess and a small remnant of the ablation zone with retraction of the liver capsule.
|
|
View larger version (129K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 9c. Hepatic abscess in a 46-year-old man after RF ablation for hepatocellular carcinoma. (a) CT image, obtained because the patient had developed a high fever 7 days after ablation, shows gas bubbles in the ablation zone, findings indicative of an abscess. US-guided percutaneous drainage of the abscess was performed. (b) Follow-up CT image obtained 14 days later shows a remnant of the abscess with the drainage catheter. (c) Contrast-enhanced CT image obtained 8 months after ablation shows complete healing of the abscess and a small remnant of the ablation zone with retraction of the liver capsule.
|
|
Bile Duct Change
Bile duct change after RF ablation is relatively common, but symptomatic bile duct changes requiring treatment are rare (42). Bile duct dilatation peripheral to the ablation zone is the most commonly observed change. Transient bile duct dilatation is thought to be caused by biliary stasis. However, if bile duct dilatation persists on follow-up CT images that also depict a decreased volume of the ablation zone, the ductal dilatation is an irreversible change caused by thermal damage to the bile duct during RF ablation (Fig 10). Such bile duct injury occurs in the peripheral intrahepatic bile ducts and not the central intrahepatic bile ducts. The large hepatic vessels adjacent to the central intrahepatic bile ducts protect them from thermal damage by exerting a cooling effect (43–46). The reported prevalence of bile duct injury due to RF ablation is 0.1%–1.0% (37–42).
View larger version (154K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 10. Bile duct injury in a 70-year-old man after RF ablation for hepatocellular carcinoma. Contrast-enhanced CT image obtained 3 months after ablation shows dilatation of the intrahepatic bile duct (arrow), a finding without clinical significance.
|
|
Biloma
A biloma appears as a fluid collection that surrounds the necrotic tissue in the RF ablation zone on follow-up CT images (Fig 11). Bilomas caused by bile leakage from injured ducts in the ablation zone usually resolve within 4 months and, in most cases, have no clinical significance. Symptomatic bilomas may be treated with percutaneous drainage (47).
View larger version (143K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 11. Biloma in a 69-year-old man after RF ablation for hepatocellular carcinoma. Contrast-enhanced CT image obtained 1 month after ablation shows a fluid collection (arrow) surrounding the ablation zone, a finding indicative of a biloma.
|
|
Pseudoaneurysm Formation
Pseudoaneurysm of the hepatic artery is a rare complication that may result from RF ablation. Few cases are reported in the literature. This complication is rare because the hepatic vessels near the index tumor are protected from thermal injury during RF ablation by the heat-sink effect of blood flow (43–46). Tamai et al reported a case of intrahepatic pseudoaneurysm formation after RF ablation and suggested that it was a mechanical injury caused by the extended hooks of the needle-tip electrode (48). We treated a pseudoaneurysm of the hepatic artery that occurred as a result of intraoperative RF ablation for a hepatic metastasis from rectal cancer (Fig 12). Careful evaluation of follow-up CT images is required to detect tiny pseudoaneurysmal sacs. If such sacs are detected, angiographic intervention is recommended to avoid rupture and bleeding.
View larger version (118K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 12a. Hepatic artery pseudoaneurysm in a 65-year-old woman after RF ablation for a hepatic metastasis from rectal cancer. (a) Portal phase CT image obtained before ablation shows a 1-cm index tumor (arrow) that abuts the right portal vein in the central part of the liver. (b) Arterial phase CT image obtained 1 year later shows a pseudoaneurysm (arrow) of a previously noted hepatic artery in the ablation zone. (c) Selective hepatic angiogram clearly shows an aneurysmal sac (arrow) that has arisen from the right hepatic artery.
|
|
View larger version (142K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 12b. Hepatic artery pseudoaneurysm in a 65-year-old woman after RF ablation for a hepatic metastasis from rectal cancer. (a) Portal phase CT image obtained before ablation shows a 1-cm index tumor (arrow) that abuts the right portal vein in the central part of the liver. (b) Arterial phase CT image obtained 1 year later shows a pseudoaneurysm (arrow) of a previously noted hepatic artery in the ablation zone. (c) Selective hepatic angiogram clearly shows an aneurysmal sac (arrow) that has arisen from the right hepatic artery.
|
|
View larger version (166K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 12c. Hepatic artery pseudoaneurysm in a 65-year-old woman after RF ablation for a hepatic metastasis from rectal cancer. (a) Portal phase CT image obtained before ablation shows a 1-cm index tumor (arrow) that abuts the right portal vein in the central part of the liver. (b) Arterial phase CT image obtained 1 year later shows a pseudoaneurysm (arrow) of a previously noted hepatic artery in the ablation zone. (c) Selective hepatic angiogram clearly shows an aneurysmal sac (arrow) that has arisen from the right hepatic artery.
|
|
Hepatic Infarction
Because the liver has a dual blood supply from the hepatic artery and portal vein, hepatic infarction rarely results from RF ablation of hepatic tumors (49–53). This complication has a reported incidence of about 0.07% (37–39). Hepatic infarction appears as nonenhanced hepatic parenchyma peripheral to the ablation zone at contrast-enhanced CT (Fig 13). Clinical symptoms of hepatic infarction are similar to those of postablation syndrome and include abdominal pain and fever. Treatment is conservative.
View larger version (124K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 13a. Hepatic infarction in a 50-year-old man with abdominal pain and a mild fever after RF ablation for hepatocellular carcinoma. (a) Portal phase CT image obtained 20 minutes after ablation shows the ablation zone (arrow) with evidence of infarction (arrowheads) in segment VI of the liver. (b) CT image obtained at 4-month follow-up shows the absence of infarction, with only minimal residual scar tissue (arrowheads) and capsular retraction.
|
|
View larger version (165K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 13b. Hepatic infarction in a 50-year-old man with abdominal pain and a mild fever after RF ablation for hepatocellular carcinoma. (a) Portal phase CT image obtained 20 minutes after ablation shows the ablation zone (arrow) with evidence of infarction (arrowheads) in segment VI of the liver. (b) CT image obtained at 4-month follow-up shows the absence of infarction, with only minimal residual scar tissue (arrowheads) and capsular retraction.
|
|
Other Uncommon Findings
Unusual findings in the RF ablation zone on follow-up CT images include capsular retraction without hepatic infarction (Fig 14) and calcification of the RF ablation zone (Fig 15). These conditions, which have unknown causes, do not require treatment.
View larger version (119K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 14a. Retraction of the liver capsule in a 53-year-old man after RF ablation for a hypovascular hepatocellular carcinoma proved at automated core-needle biopsy. (a) Delayed phase CT image obtained before ablation shows a 2.6-cm index tumor (arrow) in the right hepatic lobe. (b) Arterial phase CT image obtained 1 month after ablation shows the ablation zone with no evidence of residual tumor tissue. (c) CT image obtained at 1-year follow-up shows capsular retraction adjacent to the ablation zone.
|
|
View larger version (125K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 14b. Retraction of the liver capsule in a 53-year-old man after RF ablation for a hypovascular hepatocellular carcinoma proved at automated core-needle biopsy. (a) Delayed phase CT image obtained before ablation shows a 2.6-cm index tumor (arrow) in the right hepatic lobe. (b) Arterial phase CT image obtained 1 month after ablation shows the ablation zone with no evidence of residual tumor tissue. (c) CT image obtained at 1-year follow-up shows capsular retraction adjacent to the ablation zone.
|
|
View larger version (119K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 14c. Retraction of the liver capsule in a 53-year-old man after RF ablation for a hypovascular hepatocellular carcinoma proved at automated core-needle biopsy. (a) Delayed phase CT image obtained before ablation shows a 2.6-cm index tumor (arrow) in the right hepatic lobe. (b) Arterial phase CT image obtained 1 month after ablation shows the ablation zone with no evidence of residual tumor tissue. (c) CT image obtained at 1-year follow-up shows capsular retraction adjacent to the ablation zone.
|
|
View larger version (126K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 15a. Calcification in the ablation zone in a 68-year-old-woman after RF ablation for hepatocellular carcinoma. (a) Arterial phase CT image obtained before ablation shows a 1.6-cm index tumor without calcification in the right hepatic lobe. (b) Arterial phase CT image obtained 20 minutes after ablation shows a typical appearance of the ablation zone, with benign peripheral enhancement and tiny air bubbles. (c) Contrast-enhanced CT image obtained 5 years after ablation shows peripheral calcification of the ablation zone and decreased hepatic volume due to the gradual progression of cirrhosis.
|
|
View larger version (128K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 15b. Calcification in the ablation zone in a 68-year-old-woman after RF ablation for hepatocellular carcinoma. (a) Arterial phase CT image obtained before ablation shows a 1.6-cm index tumor without calcification in the right hepatic lobe. (b) Arterial phase CT image obtained 20 minutes after ablation shows a typical appearance of the ablation zone, with benign peripheral enhancement and tiny air bubbles. (c) Contrast-enhanced CT image obtained 5 years after ablation shows peripheral calcification of the ablation zone and decreased hepatic volume due to the gradual progression of cirrhosis.
|
|
View larger version (137K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 15c. Calcification in the ablation zone in a 68-year-old-woman after RF ablation for hepatocellular carcinoma. (a) Arterial phase CT image obtained before ablation shows a 1.6-cm index tumor without calcification in the right hepatic lobe. (b) Arterial phase CT image obtained 20 minutes after ablation shows a typical appearance of the ablation zone, with benign peripheral enhancement and tiny air bubbles. (c) Contrast-enhanced CT image obtained 5 years after ablation shows peripheral calcification of the ablation zone and decreased hepatic volume due to the gradual progression of cirrhosis.
|
|
|
Conclusions
|
|---|
The typical CT finding in the RF ablation zone is a nonenhancing area of low attenuation that encompasses the index tumor and that gradually involutes. However, atypical findings also may be observed in the ablation zone at follow-up. These include residual tumor tissue, delayed complications, and local tumor progression requiring further management. Interventional radiologists should be aware of both the typical and the atypical CT findings in the RF ablation zone and their clinical significance.
|
Footnotes
|
|---|
Abbreviations: FDG = fluorodeoxyglucose, RF = radiofrequency
See the commentary by Arellano following this article.
|
References
|
|---|
- Dodd GD 3rd, Soulen M, Kane R, et al. Minimally invasive treatment of malignant hepatic tumors: at the threshold of a major breakthrough. RadioGraphics 2000;20:9–27.[Abstract/Free Full Text]
- Rhim H, Goldberg SN, Dodd GD 3rd, et al. Essential techniques for successful radio-frequency thermal ablation of malignant hepatic tumors. RadioGraphics 2001;21(Spec Issue):S17–S35; discussion S36–S39.[Abstract/Free Full Text]
- Gazelle GS, Goldberg SN, Solbiati L, Livraghi T. Tumor ablation with radio-frequency energy. Radiology 2000;217:633–646.[Abstract/Free Full Text]
- McGhana JP, Dodd GD 3rd. Radiofrequency ablation of the liver: current status. AJR Am J Roentgenol 2001;176:3–16.[Free Full Text]
- Goldberg SN, Dupuy DE. Image-guided radiofrequency tumor ablation: challenges and opportunities—part I. J Vasc Interv Radiol 2001;12:1020–1032.
- Dupuy DE, Goldberg SN. Image-guided radiofrequency tumor ablation: challenges and opportunities—part II. J Vasc Interv Radiol 2001;12:1135–1148.[Medline]
- Solbiati L, Goldberg SN, Ierace T, et al. Hepatic metastases: percutaneous radio-frequency ablation with cooled-tip electrodes. Radiology 1997;205: 367–373.[Abstract/Free Full Text]
- Rhim H, Dodd GD 3rd. Radiofrequency thermal ablation of liver tumors. J Clin Ultrasound 1999; 27:221–229.[CrossRef][Medline]
- Goldberg SN, Solbiati L, Hahn PF, et al. Large-volume tissue ablation with radio frequency by using a clustered, internally cooled electrode technique: laboratory and clinical experience in liver metastases. Radiology 1998;209:371–379.[Abstract/Free Full Text]
- Goldberg SN, Gazelle SG, Mueller PR. Thermal ablation therapy for focal malignancy: a unified approach to underlying principles, techniques, and diagnostic imaging guidance. AJR Am J Roentgenol 2000;174:323–331.[Free Full Text]
- Livraghi T, Goldberg SN, Lazzaroni S, et al. Hepatocellular carcinoma: radio-frequency ablation of medium and large lesions. Radiology 2000; 214:761–768.[Abstract/Free Full Text]
- Livraghi T, Goldberg SN, Lazzaroni S, Meloni F, Solbiati L, Gazelle GS. Small hepatocellular carcinoma: treatment with radio-frequency ablation versus ethanol injection. Radiology 1999;210:655–661.[Abstract/Free Full Text]
- Rossi S, Buscarini E, Garbagnati F, et al. Percutaneous treatment of small hepatic tumors by an expandable RF needle electrode. AJR Am J Roentgenol 1998;170:1015–1022.[Abstract/Free Full Text]
- Choi H, Loyer EM, DuBrow RA, et al. Radiofrequency ablation of liver tumors: assessment of therapeutic response and complications. RadioGraphics 2001;21(Spec Issue):S41–S54.[Abstract/Free Full Text]
- Goldberg SN, Grassi CJ, Cardella JF, et al. Image-guided tumor ablation: standardization of terminology and reporting criteria. Radiology 2005;235: 728–739.[Abstract/Free Full Text]
- Goldberg SN, Gazelle GS, Compton CC, Mueller PR, Tanabe KK. Treatment of intrahepatic malignancy with radiofrequency ablation: radiologic-pathologic correlation. Cancer 2000;88:2452–2463.[CrossRef][Medline]
- Kim SK, Lim HK, Kim YH, et al. Hepatocellular carcinoma treated with radio-frequency ablation: spectrum of imaging findings. RadioGraphics 2003;23:107–121.[Abstract/Free Full Text]
- Lim HK, Choi D, Lee WJ, et al. Hepatocellular carcinoma treated with percutaneous radio-frequency ablation: evaluation with follow-up multiphase helical CT. Radiology 2001;221:447–454.[Abstract/Free Full Text]
- Sironi S, Livraghi T, Meloni F, De Cobelli F, Ferrero C, Del Maschio A. Small hepatocellular carcinoma treated with percutaneous RF ablation: MR imaging follow-up. AJR Am J Roentgenol 1999; 173:1225–1229.[Abstract/Free Full Text]
- Dromain C, de Baere T, Elias D, et al. Hepatic tumors treated with percutaneous radio-frequency ablation: CT and MR imaging follow-up. Radiology 2002;223:255–262.[Abstract/Free Full Text]
- Veit P, Antoch G, Stergar H, Bockisch A, Forsting M, Kuehl H. Detection of residual tumor after radiofrequency ablation of liver metastasis with dual-modality PET/CT: initial results. Eur Radiol 2006;16:80–87.[CrossRef][Medline]
- Donckier V, Van Laethem JL, Goldman S, et al. [F-18] fluorodeoxyglucose positron emission tomography as a tool for early recognition of incomplete tumor destruction after radiofrequency ablation for liver metastases. J Surg Oncol 2003;84: 215–223.[CrossRef][Medline]
- Langenhoff BS, Oyen WJ, Jager GJ, et al. Efficacy of fluorine-18-deoxyglucose positron emission tomography in detecting tumor recurrence after local ablative therapy for liver metastases: a prospective study. J Clin Oncol 2002;20:4453–4458.[Abstract/Free Full Text]
- Anderson GS, Brinkmann F, Soulen MC, Alavi A, Zhuang H. FDG positron emission tomography in the surveillance of hepatic tumors treated with radiofrequency ablation. Clin Nucl Med 2003;28: 192–197.[CrossRef][Medline]
- Choi D, Lim HK, Kim MJ, et al. Recurrent hepatocellular carcinoma: percutaneous radiofrequency ablation after hepatectomy. Radiology 2004;230:135–141.[Abstract/Free Full Text]
- Yang W, Chen MH, Yin SS, et al. Radiofrequency ablation of recurrent hepatocellular carcinoma after hepatectomy: therapeutic efficacy on early-and late-phase recurrence. AJR Am J Roentgenol 2006;186(5 Suppl):S275–S283.[Abstract/Free Full Text]
- Curley SA, Izzo F, Ellis LM, Nicolas Vauthey J, Vallone P. Radiofrequency ablation of hepatocellular cancer in 110 patients with cirrhosis. Ann Surg 2000;232:381–391.[CrossRef][Medline]
- Lencioni R, Allgaier HP, Cioni D, et al. Small hepatocellular carcinoma in cirrhosis: randomized comparison of radiofrequency thermal ablation versus percutaneous ethanol injection. Radiology 2003;228:235–240.[Abstract/Free Full Text]
- Lencioni R, Cioni D, Crocetti L, et al. Early-stage hepatocellular carcinoma in patients with cirrhosis: long-term results of percutaneous image-guided radiofrequency ablation. Radiology 2005; 234:961–967.[Abstract/Free Full Text]
- Curley SA, Izzo F, Delrio P, et al. Radiofrequency ablation of unresectable primary and metastatic hepatic malignancies: results in 123 patients. Ann Surg 1999;230:1–8.[CrossRef][Medline]
- Komorizono Y, Oketani M, Sako K, et al. Risk factors for local recurrence of small hepatocellular carcinoma tumors after a single session, single application of percutaneous radiofrequency ablation. Cancer 2003;97:1253–1262.[CrossRef][Medline]
- Hori T, Nagata K, Hasuike S, et al. Risk factors for the local recurrence of hepatocellular carcinoma after a single session of percutaneous radiofrequency ablation. J Gastroenterol 2003;38:977–981.[CrossRef][Medline]
- Harrison LE, Koneru B, Baramipour P, et al. Locoregional recurrences are frequent after radiofrequency ablation for hepatocellular carcinoma. J Am Coll Surg 2003;197:759–764.[CrossRef][Medline]
- Pawlik TM, Izzo F, Cohen DS, et al. Combined resection and radiofrequency ablation for advanced hepatic malignancies: results in 172 patients. Ann Surg Oncol 2003;10:1059–1069.[Abstract/Free Full Text]
- Kim YS, Rhim H, Cho OK, Koh BH, Kim Y. Intrahepatic recurrence after percutaneous radiofrequency ablation of hepatocellular carcinoma: analysis of the pattern and risk factors. Eur J Radiol 2006;59:432–441.[CrossRef][Medline]
- Choi D, Lim HK, Kim MJ, et al. Liver abscess after percutaneous radiofrequency ablation for hepatocellular carcinomas: frequency and risk factors. AJR Am J Roentgenol 2005;184:1860–1867.[Abstract/Free Full Text]
- Akahane M, Koga H, Kato N, et al. Complications of percutaneous radiofrequency ablation for hepatocellular carcinoma: imaging spectrum and management. RadioGraphics 2005;25(Spec Issue):S57–S68.[Abstract/Free Full Text]
- Rhim H, Yoon KH, Lee JM, et al. Major complications after radio-frequency thermal ablation of hepatic tumors: spectrum of imaging findings. RadioGraphics 2003;23:123–134; discussion 134–136.[Abstract/Free Full Text]
- Livraghi T, Solbiati L, Meloni MF, Gazelle GS, Halpern EF, Goldberg SN. Treatment of focal liver tumors with percutaneous radio-frequency ablation: complications encountered in a multi-center study. Radiology 2003;226:441–451.[Abstract/Free Full Text]
- de Baere T, Risse O, Kuoch V, et al. Adverse events during radiofrequency treatment of 582 hepatic tumors. AJR Am J Roentgenol 2003;181: 695–700.[Abstract/Free Full Text]
- Shibata T, Yamamoto Y, Yamamoto N, et al. Cholangitis and liver abscess after percutaneous ablation therapy for liver tumors: incidence and risk factors. J Vasc Interv Radiol 2003;14:1535–1542.[Medline]
- Kim SH, Lim HK, Choi D, et al. Changes in bile ducts after radiofrequency ablation of hepatocellular carcinoma: frequency and clinical significance. AJR Am J Roentgenol 2004;183:1611–1617.[Abstract/Free Full Text]
- Hansen PD, Rogers S, Corless CL, Swanstrom LL, Siperstien AE. Radiofrequency ablation lesions in a pig liver model. J Surg Res 1999;87: 114–121.[CrossRef][Medline]
- de Baere T, Elias D, Dromain C, et al. Radiofrequency ablation of 100 hepatic metastases with a mean follow-up of more than 1 year. AJR Am J Roentgenol 2000;175:1619–1625.[Abstract/Free Full Text]
- Patterson EJ, Scudamore CH, Owen DA, Nagy AG, Buczkowski AK. Radiofrequency ablation of porcine liver in vivo: effects of blood flow and treatment time on lesion size. Ann Surg 1998;227: 559–565.[CrossRef][Medline]
- Lu DS, Raman SS, Vodopich DJ, Wang M, Sayre J, Lassman C. Effect of vessel size on creation of hepatic radiofrequency lesions in pigs: assessment of the "heat sink" effect. AJR Am J Roentgenol 2002;178:47–51.[Abstract/Free Full Text]
- Shankar S, vanSonnenberg E, Silverman SG, Tuncali K, Morrison PR. Diagnosis and treatment of intrahepatic biloma complicating radiofrequency ablation of hepatic metastases. AJR Am J Roentgenol 2003;181:475–477.[Free Full Text]
- Tamai F, Furuse J, Maru Y, Yoshino M. Intrahepatic pseudoaneurysm: a complication following radio-frequency ablation therapy for hepatocellular carcinoma. Eur J Radiol 2002;44:40–43.[CrossRef][Medline]
- Smith GS, Birnbaum BA, Jacobs JE. Hepatic infarction secondary to arterial insufficiency in native livers: CT findings in 10 patients. Radiology 1998;208:223–229.[Abstract/Free Full Text]
- Holbert BL, Baron RL, Dodd GD 3rd. Hepatic infarction caused by arterial insufficiency: spectrum and evolution of CT findings. AJR Am J Roentgenol 1996;166:815–820.[Abstract/Free Full Text]
- Lev-Toaff AS, Friedman AC, Cohen LM, Radecki PD, Caroline DF. Hepatic infarcts: new observations by CT and sonography. AJR Am J Roentgenol 1987;149:87–90.[Abstract/Free Full Text]
- Kanter DM. Hepatic infarction. Arch Intern Med 1965;115:479–481.[Abstract/Free Full Text]
- Ternberg JL, Butcher HR Jr. Blood-flow relation between hepatic artery and portal vein. Science 1965;150:1030–1031.[Abstract/Free Full Text]
Related Article
-
Invited Commentary
- Ronald S. Arellano
RadioGraphics 2008 28: 390-392.
[Full Text]
[PDF]
This article has been cited by other articles:
|
|
|
|
 
R. S. Arellano
Invited Commentary
RadioGraphics,
March 1, 2008;
28(2):
390 - 392.
[Full Text]
[PDF]
|
|
|
Top
Abstract
Introduction
