MRI-guided radiofrequency thermal ablation of implanted VX2 liver tumors in a rabbit model: Demonstration of feasibility at 0.2 T

Merkle, Elmar M.; Boll, Daniel T.; Boaz, Travis; Duerk, Jeffrey L.; Chung, Yio C.; Jacobs, Gretta H.; Varnes, Marie E.; Lewin, Jonathan S.

doi:10.1002/(sici)1522-2594(199907)42:1<141::aid-mrm19>3.0.co;2-i

Cited by 61 publications

(33 citation statements)

References 28 publications

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“…The medial lobe of the liver was ablated with a 19‐gauge needle electrode (Radionics®, Burlington, MA) at 90 ± 3°C for 3 min to create an ablation zone of approximately 6 mm in diameter. This RF ablation procedure is similar to those described previously 9, 10. A short segment of a doxorubicin millirod was implanted into the ablated lobe.…”

Section: Methodsmentioning

confidence: 99%

In vivo drug distribution dynamics in thermoablated and normal rabbit livers from biodegradable polymers

Gao

Qian

Exner

et al. 2002

J. Biomed. Mater. Res.

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Image-guided radiofrequency ablation combined with intratumoral drug delivery provides a novel and minimally invasive treatment of liver cancers. In this study, the in vivo transport properties of doxorubicin in thermoablated and nonablated rabbit livers were characterized and compared. Doxorubicin was released from polymer implants (millirods) to the ablated and nonablated liver tissue. At different time points, the 2D distribution profiles were quantitatively determined by a fluorescence imaging method. Analysis of the doxorubicin concentration at the ablation boundary showed that it reached a maximum of 49.8 microg/g at 24 h after implantation, which was higher than the reported cytotoxic concentration of doxorubicin (6.4 microg/g) for liver VX-2 cancer cells. This value dropped to 0.4 microg/g at 48 h after implantation due to the depletion of doxorubicin from the polymer millirod. Results also showed that the area of drug distribution was significantly larger in ablated tissue than nonablated tissue. The therapeutic penetration distance was found to be 5.2 mm in thermoablated livers, compared to 1.2 mm in nonablated livers at 24 h. This difference in drug transport properties is attributed to destruction of the vasculature network in the ablated tissue as supported by histological analysis. Consequently, drug washout by blood perfusion is hampered while drug diffusion becomes the dominant process of transport in the ablated tissue. Results from this study provide insightful information on the rational design and development of polymer millirods for intratumoral drug delivery applications.

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Section: Methodsmentioning

confidence: 99%

In vivo drug distribution dynamics in thermoablated and normal rabbit livers from biodegradable polymers

Gao

Qian

Exner

et al. 2002

J. Biomed. Mater. Res.

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“…Goldberg et al (11) proved in a porcine model that a decrease in liver perfusion leads to an increase in lesion size using computed tomography (CT) for guidance. Our own group established a rabbit model for RF ablations of the liver (12) concluding that thermal lesion size can be accurately monitored using an open C‐arm shaped 0.2‐T MRI system.…”

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confidence: 99%

How does alteration of hepatic blood flow affect liver perfusion and radiofrequency-induced thermal lesion size in rabbit liver?

Aschoff

Merkle

Wong

et al. 2001

J. Magn. Reson. Imaging

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The purpose of this study was to test the hypothesis that decreasing liver perfusion in rabbits results in an increase in thermal lesion size and that these effects can be accurately monitored using magnetic resonance imaging (MRI). We additionally tested the hypothesis that the increase in thermal lesion size would depend on the particular vessel or vessels occluded (hepatic artery, portal vein, or both). Using an Institutional Animal Care and Use Committee approved protocol, 20 New Zealand white rabbits were randomly assigned to four treatment groups (five in each group): control and ligation of portal vein (PV), hepatic artery (HA), or both PV and HA (HAPV). Surgical ligation of the appropriate vessel was performed under general anesthesia. Immediately after ligation, the rabbits were placed in a 0.2‐T open MR system, and an 18‐G copper radiofrequency (RF) electrode with a 2‐cm exposed tip was inserted into the liver. RF was applied for 10 minutes with the tip temperature maintained at 90° ± 2°C. Before and after ablation, perfusion data were obtained for 90 seconds using 30 3‐second sequential single oblique‐slice fast imaging with steady‐state progression (FISP) acquisitions after injection of gadolinium‐diethylene triamine pentaacetic acid (Gd‐DTPA) via the inferior vena cava. Postablation scanning included axial and oblique turbo spin‐echo (TSE) T2‐weighted (T2w), STIR, and Gd‐enhanced T1w sequences. Lesion size was determined perpendicular to the RF electrode using software calipers on the imager. The rabbits were sacrificed after completion of the post‐therapy scans, and their livers were harvested for histologic analysis. The liver showed a mean increase in signal amplitude (SA) of 76% 24 seconds after Gd contrast injection in the control group. After contrast injection, the SA increased to a mean of only 66% in the group with ligated hepatic arteries, with no difference in the time to peak compared with the control group. No significant SA increase over baseline could be found in the groups with ligated PV or ligated PV and HA. T2‐weighted images demonstrated the highest lesion‐to‐liver contrast‐to‐noise ratios (CNRs; mean −5.5) on postprocedure images, followed by STIR images (mean −2.2) in the control group. The lesions were poorly delineated on the Gd‐enhanced images. Average maximum lesion sizes (mean ± 95% confidence interval) were 22 ± 4.3 mm after ligation of PV, 22 ± 2.6 mm after ligation of both PV and HA, 14 ± 2.0 mm after ligation of HA, and 13 ± 1.9 mm in the control group. We accept the hypothesis that the diameter of the region of coagulation necrosis achieved by standardized RF ablation in the liver increases with reduced organ perfusion and that this effect can be accurately monitored using MRI. The major factor influencing the size of the coagulation area is the portal venous flow. Occlusion of the hepatic artery alone does not significantly increase lesion size. T2w sequences are best suited for postprocedure imaging due to the high lesion‐to‐liver CNR in rabbits with normal ...

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“…In this work, two types of radial k‐space keyhole schemes are proposed and compared for their potential use in IMRI applications in which needle‐like devices are percutaneously introduced into the patient. Two existing widely performed example applications include biopsy (43–45) and thermal ablation of lesions (37–40, 46, 47). This project does not explore contrast requirements for IMRI procedures because the sequence type (FISP: unspoiled steady state, also termed GRASS) has a well‐established reputation for generating sufficient contrast between normal and pathologic tissue in many IMRI‐guided procedures (36–39, 43, 44, 48).…”

Section: Discussionmentioning

confidence: 99%

“…A normal 2DFT unspoiled steady‐state free precession (SSFP) sequence [fast imaging with steady‐state free precession (35) (FISP, also termed GRASS)], shown previously to be useful in MRI guidance and monitoring (36–39), was modified to achieve a 180‐view, 256 samples/view radial k‐space data acquisition (Fig. 3).…”

Section: Methodsmentioning

confidence: 99%

Radial keyhole sequences for low field projection reconstruction interventional MRI

Shankaranarayanan

Aschoff

Lewin

et al. 2001

J. Magn. Reson. Imaging

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Interventional magnetic resonance imaging (IMRI) is a rapidly emerging application for MRI in which diagnostic and therapeutic procedures are performed with MR image guidance. Real‐time or near‐real‐time image acquisition and relative insensitivity to motion are essential for most intraoperative, therapeutic, and diagnostic procedures performed under MR guidance. The purpose of this work was to demonstrate the development and utility of two alternative rapid acquisition strategies during IMRI that are analogous to computed tomography fluoroscopy or keyhole MRI in a radial rather than rectilinear coordinate frame. The two strategies discussed here, interleaved projection reconstruction and continuous projection reconstruction, are compared and the feasibility of their application in experimental interventional applications is studied. J. Magn. Reson. Imaging 2001;13:142–151. © 2001 Wiley‐Liss, Inc.

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MRI-guided radiofrequency thermal ablation of implanted VX2 liver tumors in a rabbit model: Demonstration of feasibility at 0.2 T

Cited by 61 publications

References 28 publications

In vivo drug distribution dynamics in thermoablated and normal rabbit livers from biodegradable polymers

In vivo drug distribution dynamics in thermoablated and normal rabbit livers from biodegradable polymers

How does alteration of hepatic blood flow affect liver perfusion and radiofrequency-induced thermal lesion size in rabbit liver?

Radial keyhole sequences for low field projection reconstruction interventional MRI

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