HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Figures Only Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Raman, S. S. Articles by Lassman, C. Search for Related Content PubMed PubMed Citation Articles by Raman, S. S. Articles by Lassman, C. Social Bookmarking                      What's this? Hotlight (NEW!) What's Hotlight?

Creation of Radiofrequency Lesions in a Porcine Model

Correlation with Sonography, CT, and Histopathology

¹ Department of Radiological Sciences, UCLA School of Medicine, 10833 LeConte Ave., Los Angeles, CA 90095-1721.
² Department of Pathology, UCLA School of Medicine, Los Angeles, CA 90095-1721.

Received February 3, 2000; accepted after revision May 3, 2000.

 
Partially supported by Radiotherapeutics, Inc., Mountain View, CA.

Address correspondence to D. S. K. Lu.

Abstract

Top Abstract Introduction Materials and Methods Results Discussion References

 
OBJECTIVE. We studied the correlation between sonographic and CT appearances of radiofrequency thermal lesions created in porcine liver and histopathologic findings to evaluate the accuracy of these techniques in revealing the extent of tissue necrosis.

MATERIALS AND METHODS. We used sonographic guidance and a 2.0-cm-diameter, eight-prong retractable radiofrequency electrode to view 12 hepatic lesions that were created in five pigs. Biphasic helical CT was performed 12-48 hr after ablation. The animals were sacrificed immediately after CT, and their livers were histopathologically examined. The maximum lesion size in the long and short axes as measured on CT and sonography was then correlated with the histopathologically determined lesion size.

RESULTS. On sonography, lesions changed rapidly within 5 min after the termination of ablation. An early echogenic cloud became peripherally hypoechoic with a variable thin echogenic rim. Early (0-2 min after ablation) sonograms led to an underestimation of true lesion sizes on histopathology (r = 0.3-0.49; p < 0.05). Delayed (2-5 min after ablation) sonograms also led to an underestimation of true lesion size (r = 0.5-0.62; p < 0.05); however, lesions were larger and better demarcated. Biphasic contrast-enhanced helical CT revealed avascular lesions surrounded by hyperemic rims that closely correlated with true pathologic lesions size (r = 0.93-0.95; p < 0.05). Lesions with hyperemic rims that were measured on CT led to overestimations of true lesion size.

CONCLUSION. Sonography led to underestimations of the true size of ablated lesions within the first 5 min after creation; however, delayed images provided better results. The avascular lesion measured on contrast-enhanced helical CT closely correlated with the size of ablated tissue; therefore, contrast-enhanced CT is preferred for serially monitoring the effect of radiofrequency ablation.

Introduction

Top Abstract Introduction Materials and Methods Results Discussion References

 
Radiofrequency ablation is a rapidly evolving minimally invasive technique that is applied for the treatment of primary and metastatic hepatic tumors in patients who are ineligible for surgical resection. Selective tumor ablation is facilitated by the precise insertion of a radiofrequency probe into the target lesion using sonographic, CT, or MR imaging guidance. Although sonography is the dominant image guidance technique, the accuracy of sonography depicting the extent of ablated tissue has been controversial, and most investigators rely on contrast-enhanced CT or MR imaging to determine the size of the lesion after ablation [1,2,3,4,5,6,7]. However, to our knowledge, no prior reports have directly correlated the sonographic appearance of percutaneously radiofrequency-ablated lesions with contrast-enhanced CT and gross and histopathologic findings.

Using an in vivo porcine model, we describe the sonographic and dual-phase contrast-enhanced helical CT appearance of percutaneously created radiofrequency lesions compared with histopathologic findings to determine the relative accuracy and usefulness of sonography and CT in revealing the extent of true tissue necrosis.

Materials and Methods

Top Abstract Introduction Materials and Methods Results Discussion References

 
Preapproval was obtained from the animal institutional review board for all experiments reported in this article. Five Yorkshire pigs weighing an average of 33.75 kg were used for our study. For all procedures, the pigs were sedated with general anesthesia. Induction was achieved using an intramuscular injection of 150 mg of ketamine hydrochloride (Ketaset; Animal Health, Fort Dodge, IA) and 150 mg of xylazine (Butler xylazine-100; Butler, Columbus, OH). The animals were then intubated and inhaled 5L/min of 0.5-1.5% halothane (Fluothane; Halocarbon Laboratories, River Edge, NJ).

After adequate anesthesia was achieved, the pigs were placed in the supine position. The right upper quadrant and epigastrium were shaved and sterilized, and grounding pads were placed on the animal's thighs. Using sonographic guidance (SSH-140, Toshiba, Toshigi-ken, Japan; or HDI-3000 and HDI-5000, Advanced Technology Laboratories, Bothell, WA), sites were chosen in all hepatic lobes for lesion creation. We intentionally chose regions located in liver parenchyma away from the liver surface, porta hepatis, large vessels, and visualized fissures to create spheric, nondistorted lesions.

A 16-gauge radiofrequency probe (LeVeen Electrode; Radiotherapeutics, Mountain View, CA) was used (Fig. 1). The probe was equipped with eight retractable, curved distal hooks or tines that when fully expanded form an umbrella shape 2 cm in maximum diameter perpendicular to the axis of the probe. The probe was advanced into the hepatic parenchyma, and an average of 3-4 lesions were created in each animal. A 90-W monopolar radiofrequency generator (RF 2000; Radiotherapeutics) was used as the energy source. Power output was initially set at 30 W and manually titrated to maintain maximum power without a rise in impedance for at least 5 min. Thereafter, impedance was allowed to rise with automatic power adjustment until power output was terminated. Two such sessions, without change in probe position, were used to create each lesion; most sessions lasted between 5 and 10 min.

View larger version (115K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1. —Photograph of LeVeen electrode (Radiotherapeutics, Mountain View, CA). Note eight retractable, distal curved hooks that deploy and expand to form umbrella shape with radial diameter of 2 cm.

After ablation, early (0-2 min) and late (2-5 min) phase gray-scale sonograms of the lesions were obtained. Images were obtained in the axes parallel and perpendicular to the electrode. The lesions tended to be ovoid or elliptic, with the short axis of the lesion along the length of the probe, and the long axis in the plane of the expanded hooks, perpendicular to the probe.

Contrast-enhanced dual-phase helical CT (CTi; General Electric Medical Systems, Milwaukee, WI) was performed on all animals between 12 and 48 hr after ablation. The animals were sedated using the induction anesthesia protocol discussed earlier. After initial unenhanced images of the liver were obtained, 40 mL of iohexol (Omnipaque 350; Nycomed, Princeton, NJ) was power injected at a rate of 3mL/sec; images were obtained during the arterial phase (20 sec after injection) and in the portal venous phase (60 sec after injection. The following CT parameters were used: mA, 250; kV, 120; collimation, 3 mm; pitch, 2:1. Source images and multiplanar reformatted images were obtained (Advantage Workstation; General Electric Medical Systems); the latter whenever images showed more representative long and short axes dimensions. Attempt was made to match the long- and short-axes of the sonograms on the basis of the approximate course of the radiofrequency probe tract.

Within 1 hr of obtaining the CT scan, we euthanized the pigs with an overdose of pentobarbital sodium and phenytoin sodium (Beuthanasia-D; Schering-Plough Animal Health, Kenilworth, NJ). The liver was harvested and sectioned through the visible or palpated lesions in the approximate course of the radiofrequency electrode tract. All lesions were photographed and measured with calipers in the axes parallel and perpendicular to the electrode tract. Representative sections were fixed in 10% formalin and prepared for routine microscopic analysis using H and E staining. For histologic analysis, the margin of cell death was marked by placing pen marks along the margin on low-power microscopy. Then the corresponding margin on the gross specimen was determined.

For size correlation, only spheric or oval lesions on pathology and CT, without gross contour distortion caused by proximity to major vessels, liver surface, or interlobar fissures, were chosen for analysis. All measurements were obtained using calipers on film by three observers; however, for reformatted CT scans viewed on workstations, measurements were electronically determined. From the recorded sonograms, the most representative early and late images were chosen, and the maximum diameter of the lesion was measured in the axes parallel and perpendicular to the electrode tract. For CT, the source images or multiplanar reformatted images that best approximated the short and long axes of the lesions were measured. Measurements were obtained for both the nonvascular hypodense core and for the outer limit of the enhancing rim. Correspondingly, at pathology, the most representative gross specimen section was chosen for maximum short- and long-axes measurements on the basis of the histologically determined outer margin of cell necrosis.

Correlation of lesion size between early sonography, late sonography, hypodense CT core, CT lesion including enhancing rim, and pathologic measurements were then analyzed using the Pearson's correlation coefficient, which was used to describe the degree of correlation between all possible two-variable comparisons. Statistical significance was established using the two-tailed Student's t test.

Results

Top Abstract Introduction Materials and Methods Results Discussion References

 
Twenty-one radiofrequency lesions were created. On real-time sonography, the hepatic parenchyma became diffusely echogenic in an elliptic fashion at the end of the radiofrequency session in all 21 lesions (Figs. 2A,2B,2C,2D and 3A,3B). We use the term "echogenic cloud" when referring to this central ovoid hyperechoic region, which forms rapidly, is transient in nature, and has somewhat ill-defined margins. The cause of this cloud has been ascribed to the formation of microbubbles in charred tissue [1, 3, 6, 8, 9]. The short axis of the lesion was along the course of the radiofrequency probe; the long axis of the lesion was perpendicular to the probe and along the plane created by the deployed curved distal hooks. Posterior acoustic shadowing was sometimes observed. Over the course of 5 min, the echogenic cloud faded from the periphery of the lesion, leaving a predominantly nypoechoic lesion with a smaller central echogenic nidus. Often an echogenic outer rim was also noted (Fig. 3A,3B). On late (2-5 min) images, radiofrequency lesions tended to be better demarcated, larger, and more spheric when compared with the immediate or early (within 2 min) images.

View larger version (107K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2A. —Sonographic appearance of radiofrequency lesion. Initial oblique sagittal sonogram obtained through plane of radiofrequency probe (straight arrows) reveals deployed distal curved hooks (curved arrows) in normal liver parenchyma.

View larger version (109K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2B. —Sonographic appearance of radiofrequency lesion. Sonogram obtained during ablation but just before termination shows echogenic cloud (arrows) that developed centrally and increased in size.

View larger version (124K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2C. —Sonographic appearance of radiofrequency lesion. Early sonogram obtained after ablation (within 2 min) shows echogenic cloud that begins to rapidly dissipate leaving hypoechoic rim (arrows).

View larger version (121K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2D. —Sonographic appearance of radiofrequency lesion. Late sonogram obtained after ablation (between 2 and 5 min) shows radiofrequency lesion that is primarily hypoechoic (arrows), more distinct, and larger in size than in C. Note residual central echogenicity.

View larger version (106K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3A. —Various sonographic appearances of radiofrequency lesions. Early (within 2 min) sonogram obtained after ablation shows echogenic cloud (arrows).

View larger version (102K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3B. —Various sonographic appearances of radiofrequency lesions. Late (2-5 min) sonogram shows fading echogenic cloud centrally within larger hypoechoic lesion that is demarcated by thin hyperechoic rim (arrows).

Dual-phase helical CT showed sharply demarcated hypodense nonenhancing lesions surrounded by a variable hyperemic rim on arterial phase images, portal venous phase images, or both (Fig. 4A,4B,4C). On unenhanced images, the lesions appear hypodense with variable internal hyperdensity, the latter likely indicative of hemorrhagic products.

View larger version (123K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4A. —CT scans obtained 24 hr after ablation of radiofrequency lesion (same lesion as shown in Fig. 2A,2B,2C,2D). Initial unenhanced CT scan shows hypodense lesion (arrowheads) with variable hyperdensity centrally indicating possible hemorrhage. Note how second lesion (curved arrow), located medially, is partially imaged only.

View larger version (141K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4B. —CT scans obtained 24 hr after ablation of radiofrequency lesion (same lesion as shown in Fig. 2A,2B,2C,2D). Contrast-enhanced arterial (B) and portal venous (C) phase CT scans show variable hyperemic rim (straight arrows) surrounding hypodense, nonenhancing core (arrowheads). Note how second lesion (curved arrow), located medially, is partially imaged only.

View larger version (152K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4C. —CT scans obtained 24 hr after ablation of radiofrequency lesion (same lesion as shown in Fig. 2A,2B,2C,2D). Contrast-enhanced arterial (B) and portal venous (C) phase CT scans show variable hyperemic rim (straight arrows) surrounding hypodense, nonenhancing core (arrowheads). Note how second lesion (curved arrow), located medially, is partially imaged only.

At gross pathology, in all pigs, the created lesion was sharply demarcated with three distinct regions, and the histologic examination showed a difference between viable and nonviable tissue. A central, predominantly pale, tan zone was surrounded by a variably sized red ring. In most pigs, a pink, variably sized outer rim surrounded the pale zone and red ring and showed variable demarcation from normal hepatic parenchyma (Fig. 5). Histologically, the central pale zone contained completely coagulated tissue with no viable cells. The red ring contained mainly hemorrhage, debris, and fibrin without viable cells. The outermost pink rim of tissue contained an admixture of viable hepatic parenchyma, necrosis, and hemorrhage (Fig. 6). On the basis of these findings, we used the junction between the red and pink rims at gross pathology to define the outer margin of definite cell death.

View larger version (138K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5. —Gross pathology of representative radiofrequency lesion. Between 24 and 48 hr after ablation, the typical radiofrequency lesion is delimited by three concentric areas: central core that is pale or tan (N), middle hemorrhagic or red rim (arrowheads), and outer pink rim (arrows) of variable thickness that merges with normal hepatic parenchyma (L).

View larger version (120K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6. —Low-power photomicrograph of representative radiofrequency lesion (same lesion as shown in Figure 5) shows three zones: inner necrotic pale zone (N) that contained dead, empty vacuolated hepatocytes on highpower microscopy; red rim (H) that contained hemorrhagic material and thrombosed vessels without any viable cells; and outer pink rim (P) that contained an admixture of hemorrhage and viable hepatocytes. These zones corresponded to zones visible on Figure 5. Normal liver (L) surrounds radiofrequency lesion.

Twelve radiofrequency lesions were chosen for image analysis because they were located away from the hepatic surface, fissures, and major vessels with a nondistorted spheric or ovoid shape. For all imaging techniques we used, average lesion sizes are summarized in Table 1. The corresponding values for the Pearson's correlation coefficient and statistical significance are shown in Table 2. Lesion size as shown by the nonenhancing region on portal venous phase helical CT scans closely correlated with gross pathologic findings, although the hyperattenuating rim significantly contributed to an overestimation of pathologic lesion size. However, on sonography, early (within 2 min) images did not show lesions that represented the true pathologic size. On late (2-5 min) images, the lesions were larger, but the images still led to an underestimation of lesion size compared with CT or pathology.

Discussion

Top Abstract Introduction Materials and Methods Results Discussion References

 
Although sonography is the predominant imaging technique used for guiding the radiofrequency ablation of liver tumors, controversy continues regarding the accuracy and usefulness of sonography in reliably revealing the true size of lesions. Although studies have correlated the pathologic size of lesions with sonography or CT, to our knowledge, none have directly correlated sonography with contrast-enhanced CT or both with pathology.

Earlier reports described a good correlation between sonographically measured size of the created lesion and final pathologic results [1, 2]. However, most studies showed that gray-scale, color Doppler, and power Doppler sonography correlate poorly with the extent of coagulation-induced necrosis [3,4,5,6,7]. In our study, gray-scale sonography consistently led to underestimations of lesion size after ablation when compared with CT and pathologic findings; however, delayed sonograms revealed more closely approximated pathologic size. On early images, the precise outer lesion margins were obscured because of the formation of the expanding echogenic cloud with variable posterior shadowing. On later images, the echogenic cloud dissipated peripherally leaving a better defined outer margin, either hypoechoic relative to the normal liver or demarcated by a thin outer echogenic zone.

Our findings concur with previous reports that describe the progression of sonographic findings during and after percutaneous radiofrequency ablation. McGahan et al. [8] initially described similar sonographic findings during single-needle intraoperative (postlaparotomy) radiofrequency ablation using an in vivo swine liver. An initially diffuse echogenic lesion gradually became less echogenic over 5 weeks. Quantitation of lesion size on sonography and pathology was not made in this study. Solbiati et al. [9] reported that lesions stabilized in their sonographic appearance (outer hypoechoic rim and inner echogenic rim) after 15 min with only slight change on serial sonograms obtained over 6 months. In that study, sonography also led to an underestimation of overall lesion size, but pathologic correlation was provided 6 months after ablation.

Dual-phase contrast-enhanced helical CT performed between 12 and 48 hr after ablation closely approximated the gross pathologic size in the long and short axes. On CT, lesions were nearly spheric, low in attenuation, and nonenhancing. A 1- to 3-mm hypervascular rim was present mainly on the arterial phase images and sometimes persisted into the portal venous phase. Although some previous studies have observed close correlation between overall size of lesions on contrast-enhanced CT and gross pathologic findings, only Goldberg et al. [10] reported close qualitative lesion size correlation between contrast-enhanced CT scans and gross pathologic findings in a porcine model. In our study, we quantitatively demonstrated in 12 lesions with a high degree of size correlation between contrast-enhanced CT and gross pathologic findings. The nonenhancing CT lesion corresponded with the inner necrotic zone plus the hemorrhagic rim. The outer enhancing rim approximated the pink rim, an area with viable cells, on pathology. When we measured with the outer rim, CT led to an overestimation of true lesion size.

On gross and histopathologic sections, three distinct zones consistently characterized each lesion: central pale yellow necrotic zone, hemorrhagic rim, and outer pink rim. These roughly correlate to the zones 1, 2, and 3 described by McGahan et al. [8], although they sectioned the liver between 1 week and 5 months after in vivo ablation. Our histopathologic findings support previously published findings. In our study, histopathologic examination was performed between 12 and 48 hr after ablation to allow changes that permit distinction between viable and nonviable tissue. The central necrotic area and the hemorrhagic rim closely corresponded to the nonenhancing, low-attenuation CT lesion. Goldberg et al. [10] reported this finding in their porcine model with radiofrequency ablation. No viable hepatocytes, bile ducts, arteries, or veins were present in the central or hemorrhagic zone, in keeping with the lack of enhancement on contrast-enhanced images. The presence of numerous viable and engorged blood vessels in the pink rim may account in part for the contrast enhancement observed on concentric layers of differing histology within normal porcine liver tissue examined 1 week after radiofrequency ablation in the study of Goldberg et al. Slight differences between reported appearances are likely caused by differences in postprocedural time course.

Limitations of this study include potential differences between porcine liver and human liver that may affect the sonographic and CT appearances of radiofrequency lesions. Every attempt was made to ensure validity of size correlation among sonographic, CT, and pathologic findings, but absolute precision is not possible because of the intrinsic differences in scanning planes between sonography and CT and the difficulty in replicating the corresponding plane in pathologic sections. Nevertheless, standardization was sought by analyzing only minimally distorted lesions that were close to spheric in shape, using both long- and shortaxes measurements; using multiplanar reformatted CT images; and sectioning the pathologic lesion through the plane of the radiofrequency probe tract. This study did not evaluate the role of sonographic contrast agents in the assessment of lesions created by radiofrequency. Preliminary studies in rabbits by Goldberg et al. [11] and in humans by Lencioni et al. (Lencioni et al., presented at Radiological Society of North America meeting, December 1999) suggest that sonographic agents may be of value in the real-time assessment of tumor ablation. Further study is required to assess the efficacy of these agents in predicting the true extent of radiofrequency-induced necrosis.

In summary, radiofrequency lesion size as revealed on a nonenhancing area on portal venous phase contrast-enhanced CT closely correlated with gross pathologic findings. Because most radiofrequency procedures are performed with sonographic guidance, it is important to keep in mind that gray-scale sonography tends to lead to an underestimation of lesion size, although delayed images obtained after ablation provide better results than images obtained immediately after ablation.

References

Top Abstract Introduction Materials and Methods Results Discussion References

 

1. Sanchez R, vanSonnenberg E, D'Agostino H, et al. Percutaneous tissue ablation by radiofrequency thermal energy as a prelim to tumor ablation. Min Inv Ther 1993;2:299 -305
2. Curley SA, Davidson BS, Fleming RY, et al. Laparoscopically guided bipolar radiofrequency ablation of areas of porcine liver. Surg Endosc 1997;11:729 -733[Medline]
3. Lorentzen T, Cristensen NE, Nolsoe CP, et al. Radiofrequency tissue ablation with a cooled needle in vitro: ultrasonography, dose response, and lesion temperature. Acad Radiol 1997;4:292 -297[Medline]
4. 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]
5. Solbiati L, Goldberg SN, Ierace T, et al. Radio-frequency ablation of hepatic metastases: postprocedural assessment with a US microbubble contrast agent—early experience. Radiology 1999;211:643 -649[Abstract/Free Full Text]
6. Goldberg SN, Gazelle GS, Solbiati L, et al. Ablation of liver tumors using percutaneous RF therapy. AJR 1998;170:1023 -1028[Free Full Text]
7. Rossi S, Di Stasi M, Buscarini E, et al. Percutaneous RF interstitial thermal ablation in the treatment of hepatic cancer. AJR 1996;167:759 -768[Abstract/Free Full Text]
8. McGahan JP, Brock JM, Tesluk H, et al. Hepatic ablation with use of radio-frequency electrocautery in the animal model. J Vasc Interv Radiol 1992;3:291 -297[Medline]
9. Solbiati L, Ierace T, Goldberg SN, et al. Percutaneous US-guided radio-frequency tissue ablation of liver metastases: treatment and follow-up in 16 patients. Radiology 1997;202:195 -203[Abstract/Free Full Text]
10. Goldberg SN, Hahn PF, Tanabe KK, et al. Percutaneous radiofrequency tissue ablation: does perfusion-mediated tissue cooling limit coagulation necrosis? J Vasc Interv Radiol 1998;9:101 -111[Medline]
11. Goldberg SN, Walovitch RC, Straub JA, Shore MT, Gazelle GS. Radio-frequency-induced coagulation necrosis in rabbits: immediate detection at US with a synthetic microsphere contrast agent. Radiology 1999;213:438 -444[Abstract/Free Full Text]

CiteULike

Complore

Connotea

Del.icio.us

Digg

Reddit

Technorati

This article has been cited by other articles:

				A. P. S. Kirkham, M. Emberton, I. M. Hoh, R. O. Illing, A. A. Freeman, and C. Allen MR Imaging of Prostate after Treatment with High-Intensity Focused Ultrasound Radiology, March 1, 2008; 246(3): 833 - 844. [Abstract] [Full Text] [PDF]

				H. W. Head, G. D. Dodd III, N. C. Dalrymple, S. R. Prasad, F. M. El-Merhi, M. W. Freckleton, and L. G. Hubbard Percutaneous Radiofrequency Ablation of Hepatic Tumors against the Diaphragm: Frequency of Diaphragmatic Injury Radiology, June 1, 2007; 243(3): 877 - 884. [Abstract] [Full Text] [PDF]

				M. J. Dill-Macky, M. Asch, P. Burns, and S. Wilson Radiofrequency ablation of hepatocellular carcinoma: predicting success using contrast-enhanced sonography. Am. J. Roentgenol., May 1, 2006; 186(5 Suppl): S287 - S295. [Abstract] [Full Text] [PDF]

				A. Yamamoto, K. Nakamura, T. Matsuoka, M. Toyoshima, T. Okuma, Y. Oyama, Y. Ikura, M. Ueda, and Y. Inoue Radiofrequency Ablation in a Porcine Lung Model: Correlation Between CT and Histopathologic Findings Am. J. Roentgenol., November 1, 2005; 185(5): 1299 - 1306. [Abstract] [Full Text] [PDF]

				A. S. Wright, L. A. Sampson, T. F. Warner, D. M. Mahvi, and F. T. Lee Jr Radiofrequency versus Microwave Ablation in a Hepatic Porcine Model Radiology, July 1, 2005; 236(1): 132 - 139. [Abstract] [Full Text] [PDF]

				T. J. Kim, W. K. Moon, J. H. Cha, J. M. Goo, K. H. Lee, K. H. Kim, J. W. Lee, J. G. Han, H.-J. Weinmann, and K. H. Chang VX2 Carcinoma in Rabbits after Radiofrequency Ablation: Comparison of MR Contrast Agents for Help in Differentiating Benign Periablational Enhancement from Residual Tumor Radiology, February 1, 2005; 234(2): 423 - 430. [Abstract] [Full Text] [PDF]

				S. S. Raman, D. Aziz, X. Chang, J. Sayre, C. Lassman, and D. Lu Minimizing Diaphragmatic Injury During Radiofrequency Ablation: Efficacy of Intraabdominal Carbon Dioxide Insufflation Am. J. Roentgenol., July 1, 2004; 183(1): 197 - 200. [Abstract] [Full Text] [PDF]

				C. T. Sofocleous, K. M. Klein, B. Hubbi, K. T. Brown, S. H. Weiss, G. Kannarkat, C. R. Hinrichs, D. Contractor, P. Bahramipour, A. Barone, et al. Histopathologic Evaluation of Tissue Extracted on the Radiofrequency Probe After Ablation of Liver Tumors: Preliminary Findings Am. J. Roentgenol., July 1, 2004; 183(1): 209 - 213. [Abstract] [Full Text] [PDF]

				J. R. Leyendecker, G. D. Dodd III, G. A. Halff, V. A. McCoy, D. H. Napier, L. G. Hubbard, K. N. Chintapalli, S. Chopra, W. K. Washburn, R. M. Esterl, et al. Sonographically Observed Echogenic Response During Intraoperative Radiofrequency Ablation of Cirrhotic Livers: Pathologic Correlation Am. J. Roentgenol., May 1, 2002; 178(5): 1147 - 1151. [Abstract] [Full Text] [PDF]

				S. S. Raman, D. S. K. Lu, D. J. Vodopich, J. Sayre, and C. Lassman Minimizing Diaphragmatic Injury during Radio-frequency Ablation: Efficacy of Subphrenic Peritoneal Saline Injection in a Porcine Model Radiology, March 1, 2002; 222(3): 819 - 823. [Abstract] [Full Text] [PDF]

This Article Abstract Figures Only Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Raman, S. S. Articles by Lassman, C. Search for Related Content PubMed PubMed Citation Articles by Raman, S. S. Articles by Lassman, C. Social Bookmarking                      What's this? Hotlight (NEW!) What's Hotlight?