DOI: 10.1148/radiol.2472070808
(Radiology 2008;247:374-380.)
© RSNA, 2008
Heat Distribution in the Spinal Canal during Radiofrequency Ablation for Vertebral Lesions: Study in Swine1
Akira Adachi, MD,
Toshio Kaminou, MD, PhD,
Toshihide Ogawa, MD, PhD,
Tsuyoshi Kawai, MD,
Yasunobu Takaki, MD,
Kimihiko Sugiura, MD,
Yasufumi Ohuchi, MD, and
Masayuki Hashimoto, MD
1 From the Department of Pathophysiological and Therapeutic Science, Division of Radiology, Faculty of Medicine, Tottori University, 36-1 Nishicho, Yonago, Tottori 683-8504, Japan. Received May 8, 2007; revision requested July 6; revision received August 1; accepted August 28; final version accepted October 4. Address correspondence to A.A. (e-mail: july1st{at}grape.med.tottori-u.ac.jp).
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ABSTRACT
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Purpose: To prospectively evaluate the safety of radiofrequency (RF) ablation for vertebral lesions by monitoring the temperature in swine vertebral models with and without a cortical bone defect.
Materials and Methods: The institutional animal care and use committee approved the animal studies. In vivo and ex vivo studies were performed. In the in vivo study, 20 lumbar vertebrae from six swine were locally heated by using 1- or 2-cm active-tip internally cooled electrodes. In the ex vivo study, 12 fresh pig cadaver lumbar vertebrae were extracted from four swine, and spinal tumor models with or without cortical bone defect were created by stuffing a cavity with muscle tissue and locally heated by using a 1-cm active-tip internally cooled electrode. The temperature was monitored in the spinal canal and around the vertebral body during ablation. Mann-Whitney U test was used to indicate a significant difference between groups by using 1- and 2-cm active tip in the in vivo study and between groups with and without cortical defect in the ex vivo study.
Results: In the in vivo study in which 1- and 2-cm active-tip needles were used, the temperature in the spinal canal rose to 38.2°C ± 2.7 (standard deviation) and 45.5°C ± 6.2, respectively. The latter was significantly higher than the former (P < .001). In the ex vivo study in which tumor models with or without a cortical bone defect were used, the temperature in the spinal canal rose to 48.4°C ± 6.2 and 31.3°C ± 3.4, respectively. The former was significantly higher than the latter (P < .001).
Conclusion: For in vivo cases with a 2-cm active tip and ex vivo cases with a vertebral posterior bone defect, the temperature rose to over 45°C, potentially injuring the spinal cord and peripheral nerves.
© RSNA, 2008
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INTRODUCTION
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Radiofrequency (RF)-induced tissue coagulation necrosis is an image-guided method of tumor ablation. Rosenthal et al (1–3) first described the use of RF ablation for the treatment of osteoid osteomas and proposed RF ablation as an alternative to surgical treatment in patients with osteoid osteoma. In preliminary reports, some authors found that RF ablation may provide a new method for palliation of painful skeletal metastases when radiation therapy or chemotherapy has failed (4,5). Pain relief was achieved in 90%–100% of patients treated with RF ablation (4–9).
RF ablation can also be applied to malignancies in the spine; however, the spine includes important nerve tissues such as the spinal cord and nerve root, and RF ablation may affect these tissues. The temperature-related effects of RF heating on the adjacent thecal sac contents should be evaluated before RF ablation of vertebral lesions is more widely adopted. However, there are only a few experimental or clinical reports on heat distribution around the vertebral bone during RF ablation. Importantly, to our knowledge, there have been no detailed studies about injury to tissue surrounding the vertebral bone such as the spinal cord and nerve root. Thus, the purpose of our study was to prospectively evaluate the safety of RF ablation for vertebral lesions by monitoring the temperature in swine vertebral models with and without a cortical bone defect.
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MATERIALS AND METHODS
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In vivo and ex vivo studies were performed. Approval of the institutional subcommittee on animal research care was obtained for our study.
In Vivo Experiments
Six adult swine weighing 38.0–44.7 kg (mean, 42.1 kg ± 2.7 [standard deviation]) were included in our study. The animals were intubated and anesthetized with halothane (Fluothane; Takeda Pharmaceutical, Osaka, Japan) and placed in the left lateral decubitus position. Cardiac and respiratory parameters were monitored during the procedure.
A 13-gauge bone biopsy needle (Medical Device Technologies, Gainesville, Fla) was placed in lumbar vertebral bodies (L1 through L5) by using a fluoroscopic guide (Infinix Celeve CC; Toshiba Medical Systems, Ohtawara, Tochigi, Japan). A 17-gauge internally cooled RF electrode with a 1- or 2-cm active tip was placed through the bone biopsy needle. A metallic needle covered with a 20-gauge fine plastic tube (Happy Cath PTCD Medikit; Hyuga, Miyazaki, Japan) was advanced into the spinal canal through the intervertebral foramen at the same level and 1 cm away from the RF needle. One additional hole was made in the vertebral body for placement of another bone biopsy needle 1 cm away from the RF electrode in the cranial direction.
Another covered metallic needle was placed on the front surface of the vertebra. Three temperature sensors (TM-301; As One, Nishiku, Osaka, Japan) were inserted, one into each of the tubes and one to monitor the bone biopsy needle. Two authors performed all ablations and placed sensors (A.A. and T.K., each with more than 5 years experience in RF ablation of malignant bone tumors). Three temperatures were recorded every 30 seconds during ablation. The temperature of the electrode tip was recorded at the start and end of the ablation. Ten lumbar vertebrae were used for each arm of the in vivo experiment (1- vs 2-cm active tip), respectively (Fig 1).
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Figure 1a: (a) Lateral radiograph shows RF needle placed in vertebral body through bone biopsy needle (arrow) and three temperature sensors (arrowheads). Temperature sensors were placed in spinal canal, on front surface of vertebra and in vertebral body. (b) Diagram shows RF needle position and three temperature sensors. RF needle placed in vertebral body through bone biopsy needle. Temperature sensors placed in spinal canal through intervertebral foramen at level of RF needle, on front surface of vertebra, and in vertebral body through other bone biopsy needle.
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Figure 1b: (a) Lateral radiograph shows RF needle placed in vertebral body through bone biopsy needle (arrow) and three temperature sensors (arrowheads). Temperature sensors were placed in spinal canal, on front surface of vertebra and in vertebral body. (b) Diagram shows RF needle position and three temperature sensors. RF needle placed in vertebral body through bone biopsy needle. Temperature sensors placed in spinal canal through intervertebral foramen at level of RF needle, on front surface of vertebra, and in vertebral body through other bone biopsy needle.
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Ex Vivo Experiments
Twelve ex vivo studies were performed to compare the heat distribution around the lumbar vertebral body with or without cortical bone defect. Four adult swine weighing 38.5–43.2 kg (mean, 40.9 kg ± 2.0) were used in this study and fresh lumbar vertebral bodies (L1 through L4) were excised from these four pig cadavers. The average vertebral sizes measured were depth, 19.1 mm ± 1.4 (as measured from anterior wall to posterior wall of the vertebral body); width, 31.7 mm ± 2.5 (as measured from left wall to right wall); and height, 30.0 mm ± 2.9. For a metastatic bone tumor model, a cortical bone defect at the posterior wall of the vertebral body was created: two holes were made on each lateral wall of the vertebral body and a cavity was made in the vertebral body via these two holes. Then, fresh muscle tissue was stuffed into the cavity as a tumor model.
The RF electrode was inserted through the lateral holes. A temperature sensor was placed beside the anterior wall of the spinal canal at the same level as the RF electrode to monitor the temperature in the spinal canal. The other temperature sensor was placed beside the anterior wall of the vertebral body to measure the temperature at the paravertebral region. The vertebral model and temperature sensors were placed in a plastic case with a copper bottom, which was filled with egg white. The grounding pads were fixed on the copper bottom. The temperatures of the spinal canal and paravertebral region were recorded every 30 seconds. The temperature of the electrode tip was measured at the start and end of the ablation (Fig 2).
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Figure 2: Transverse diagram shows RF needle position and sensors in ex vivo tumor model. Schema shows two temperature sensors positioned at posterior and anterior walls of vertebral body.
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RF Ablation
Experiments were performed with an RF generator (CC-1; Radionics Valley Lab, Burlington, Mass) capable of producing maximal output of 200 W. Internally cooled RF electrodes with either 1 or 2 cm of exposed metallic tip (Radionics Valley Lab) were used to transmit energy to the tissue. These electrically insulated 17-gauge electrodes contained two central lumina that allowed delivery of chilled perfusate to the tip of the electrode and return of the warmed effluent to a collection unit outside the body. A peristaltic pump (Radionics Valley Lab) was used to deliver 0°C distilled water through the electrodes at more than 60 mL/min.
A single RF application was performed by using a 1- or 2-cm active-tip needle in the in vivo studies and by using a 1-cm active-tip needle in the ex vivo studies. Application started with a 10-W output and increased by 5 W every 1 minute in 1-cm active-tip needles or with a 30-W output and increased by 10 W every 1 minute in 2-cm active-tip needles. The application was observed with impedance control, which delivered power until the impedance rose to 20 
above the baseline value.
Safety
We referred to previous literature regarding thermal injury for nerve tissue and considered that a temperature of more than 45°C in the spinal canal can potentially induce thermal injury for nerve tissue, making the procedure unsafe.
Statistical Analysis
For each in vivo study, performed with 1- or 2-cm active-tip RF needles, we used 10 lumbar vertebral bodies. The temperatures in the spinal canal achieved with a 1-cm active-tip RF electrode were compared with those obtained with a 2-cm active-tip RF electrode. Ex vivo studies were performed on six lumbar vertebral bodies with or without cortical defect by using a 1-cm active-tip RF needle. The temperatures in the spinal canal measured in the cortical bone defect model with RF ablation were compared with those obtained in the intact cortical bone model. Results were subject to routine statistical analysis, as appropriate. Unless otherwise specified, the Mann-Whitney U test was used to determine a significant difference. All tests were two-sided, and a P value of less than .05 was considered to indicate a significant difference. Data analysis was performed by using software (StatMate III for Macintosh; ATMS, Bunkyo, Tokyo, Japan).
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RESULTS
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In Vivo Experiments
In the group with a 1-cm active-tip needle, the mean ablation time was 129.3 seconds ± 23.5 (range, 90–177 seconds; median, 128.5 seconds). At the end of the ablation, the temperatures in the spinal canal, vertebral body, and paravertebral region had risen to 38.2°C ± 2.7 (range, 34.5°–41.6°C; median, 38.3°C), 52.8°C ± 11.4 (range, 38.8°–69.3°C; median, 50.0°C), and 33.6°C ± 2.4 (range, 28.4°–36.8°C; median, 33.1°C), respectively. The temperature at the needle tip had risen to 71.5°C ± 4.3 (range, 64°–76°C; median, 73.5°C) (Fig 3a). In the group with a 2-cm active-tip needle, the mean ablation time was 144.6 seconds ± 30.3 (range, 90–206 seconds; median, 145.5 seconds). At the end of ablation, the temperature in the spinal canal, vertebral body, and paravertebral region had risen to 45.5°C ± 6.2 (range, 37.9°–55.4°C; median, 47.0°C), 83.8°C ± 18.9 (range, 57.0°–104.0°C; median, 83.9°C), and 38.3°C ± 3.7 (range, 33.9°–42.2°C; median, 37.7°C), respectively. The temperature of the tip had risen to 86.1°C ± 4.0 (range, 78°–92°C; median, 87.0°C) (Fig 3b). The temperature in the spinal canal with a 2-cm active-tip needle was significantly higher than the temperature with a 1-cm active-tip needle (P < .001).
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Figure 3a: (a) Graph of four mean temperatures at RF ablation start and end with 1-cm active-tip needle shows temperature of spinal canal slightly increased. (b) Graph of four mean temperatures at RF ablation start and end with 2-cm active-tip needle shows significantly higher temperature (over 45°C) in spinal canal (P < .001) compared with that of 1-cm active tip.
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Figure 3b: (a) Graph of four mean temperatures at RF ablation start and end with 1-cm active-tip needle shows temperature of spinal canal slightly increased. (b) Graph of four mean temperatures at RF ablation start and end with 2-cm active-tip needle shows significantly higher temperature (over 45°C) in spinal canal (P < .001) compared with that of 1-cm active tip.
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Ex Vivo Experiments
In the specimens with cortical defect, the mean ablation time was 172.1 seconds ± 24.6 (range, 137–193 seconds; median, 187.0 seconds). At the end of ablation, the temperature in the spinal canal and on the anterior wall of the vertebral body had risen to 48.4°C ± 6.2 (range, 40.0°–57.3°C; median, 48.4°C) and 31.6°C ± 2.9 (range, 28.0°–35.1°C; median, 31.8°C), respectively. The temperature of the tip had risen to 77.5°C ± 7.3 (range, 63°–83°C; median, 80.0°C) (Fig 4a). In the specimens without cortical defect at the posterior wall of the vertebral bodies, the mean ablation time was 133.7 seconds ± 24.1 (range, 90–155 seconds; median, 136.0 seconds). At the end of ablation, the temperature in the spinal canal and on the anterior wall of the vertebral body had risen to 31.3°C ± 3.4 (range, 25.6°–34.8°C; median, 32.1°C) and 32.1°C ± 2.4 (range, 28.0°–35.1°C; median, 32.7°C), respectively. The temperature of the tip had risen to 77.0°C ± 4.3 (range, 72°–83°C; median, 77.0°C) (Fig 4b). The temperature in the spinal canal with a cortical bone defect model was significantly higher than the temperature in the intact cortical bone model (P < .001).
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Figure 4a: (a) Graph of three mean temperatures at RF ablation start and end in specimen with posterior wall cortical defect. Temperature in spinal canal was significantly higher in model with cortical defect than without (P < .001). (b) Graph of three mean temperatures at RF ablation start and end in specimen without posterior wall cortical defect shows slight increase in temperature of spinal canal.
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Figure 4b: (a) Graph of three mean temperatures at RF ablation start and end in specimen with posterior wall cortical defect. Temperature in spinal canal was significantly higher in model with cortical defect than without (P < .001). (b) Graph of three mean temperatures at RF ablation start and end in specimen without posterior wall cortical defect shows slight increase in temperature of spinal canal.
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DISCUSSION
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RF tissue ablation is a well-known technique for inducing thermal lesions around the tip of an electrode as a result of tissue coagulation caused by resistive heating. When the electrode is attached to an appropriate generator, an RF current is emitted from the exposed, noninsulated portion of the electrode. This current translates to ion agitation in the surrounding tissue, which is then converted to heat by using friction, inducing cellular death as a result of coagulation necrosis.
At present, the main field of application for RF ablation is the treatment of primary or secondary tumors of the liver (10–14). However, the technique has been effectively used to treat tumors in other organs such as the prostate, kidney, lung, brain, pancreas, and breast and to control pain caused by osteoid osteomas (15–24). Rosenthal et al (1–3) have reported the use of RF ablation for the treatment of osteoid osteoma. Researchers in three preliminary works have demonstrated that RF ablation is a new promising technique for controlling pain in patients with bone metastases in whom radiation therapy or chemotherapy has failed 4–6).
RF can also be applied to malignancies in the spine, a common location for painful bone metastases, where tumors abut vital structures such as the spinal cord and thermal injury can cause severe damage. However, RF ablation for vertebral lesions has not been performed for a detailed study of the risks of injuring tissue surrounding the vertebral bone such as the spinal cord and nerve root.
In our study, we used a straight electrode with an internally cooled tip instead of an expandable-array electrode, because an expandable-array electrode cannot easily reach the bone tumor, whereas a straight electrode is usually used in a clinical setting. In our in vivo model with preserved cancellous and cortical bone, the temperature of the spinal canal reached 38.2°C (maximum, 41.6°C) during ablation with a 1-cm active-tip needle. However, in the in vivo model, in which we used a 2-cm active-tip needle, the temperature of the spinal canal reached 45.5°C (maximum, 55.4°C). As described by Froese et al (25), the effects of temperature increase on neural structures in the spinal cord of mice indicate a 50% damage rate for nerve tissue after warming to 45°C for 10.8 minutes; a time reduction factor of 2.25 was found to occur for comparable nerve tissue damage for every degree of increase in temperature. Damage to nerve tissue at 45°C has also been shown for peripheral nerves (26). Dupuy et al (4) performed a small study and reported that cancellous and cortical bone decreased heat transmission in their ex vivo studies and the maximum temperature observed in the epidural space was 44°C in a porcine in vivo model by using a 1-cm active-tip needle. They concluded that, in the presence of preserved cancellous or cortical bone between the lesion and the spine, a margin of safety will be provided. The findings of our in vivo study with a 1-cm active-tip needle support the findings of the in vivo study by Dupuy et al, but the findings of our in vivo study with a 2-cm active-tip needle suggest that RF ablation for a spinal lesion by using a needle with a longer active tip potentially induces thermal injury, even in the presence of intact cancellous or cortical bone between the lesion and spinal cord.
RF application with the 2-cm active tip was started at 30 W and at 10 W with the 1-cm active tip. Because the input and output power of the 2-cm active-tip needle were higher than those with the 1-cm active-tip needle, the former produced more calories than the latter. These high caloric values may affect the temperature in the spinal canal.
Most painful spinal metastases involve the cortex and sometimes the posterior wall, which compress the dural sac contents. Dupuy et al (4) reported that, in patients with extensive osteolysis with no intact cortex between the tumor and spinal cord or nerve roots, RF ablation may not be an option because of the potential for thermal injury to adjacent neural tissue. Nakatsuka et al (27) reported neural damage in four patients in whom the tumor had invaded the posterior cortex of the vertebral body and pedicle. To our knowledge, despite some studies describing its clinical use, there are no publications concerning the thermodynamic processes affecting posterior cortical bone during RF ablation.
In our ex vivo model without cortical defect, the temperature in the spinal canal was similar to that in our in vivo model during RF ablation with a 1-cm active-tip needle. However, in our ex vivo model with cortical defect with a 1-cm active-tip needle, which was safe in our in vivo intact cortical bone model, the temperature in the spinal canal reached 48.4°C. This temperature, which can potentially induce thermal injury to nerve tissue, is significantly higher than that in the intact cortical bone model, where the temperature in the spinal canal reached 31.3°C.
Because the level of heat generated in cortical bone is lower than that generated in parenchymal tumors, the surrounding bone can withstand thermal injury, as has been proved in our clinical practice and elsewhere, for two reasons.
First, cortical bone has an insulative effect and cancellous bone decreases heat transmission. Dupuy et al (4) reported that ex vivo experiments confirmed a decreased level of heat transmission through cancellous bone at a distance of 10 mm from the electrode (13.4°C ± 4.5) when compared with a liver (20.0°C ± 3.4) or an agar (18.5°C ± 3.1) phantom (both P < .05), and that temperatures in the bone cortex with the electrode increased (25.7°C ± 7.0) when compared with temperatures at an equal distance but on the other side of the cortical bone (11.2°C ± 2.0, P > .001).
Second, the tissue resistivity of liver or bone marrow compared with that of cortical bone varies considerably and is much higher (10- to 100-fold) in cortical bone and there is more heat generation in tissue with less resistance (28).
Our study had limitations in that some aspects of our model differed from the conditions found during clinical use. For the tumor model with or without cortical defect, we performed ex vivo studies because it would have been difficult to create such a model in vivo. In ex vivo models, there is no flow of blood or cerebrospinal fluid; therefore, in the clinical setting, the heat distribution might be expected to be lower than our results in ex vivo models.
Practical application: RF ablation, as used in our swine study, may carry a risk of thermal injury to neural tissue, even for a spinal lesion without a cortical defect. Therefore, for the treatment of a spinal lesion, one without invasion to the posterior cortical bone of the vertebral body should be a candidate for this treatment and short active-tip needles should be used. On the other hand, it may be helpful to place a temperature sensor near the thecal sac or the peripheral nerves and to monitor the temperature to avoid nerve injury. Magnetic resonance thermometry also might prove to be a useful technique for temperature monitoring to improve the safety of RF therapy for spinal lesions (28,29).
Given our results, RF ablation by using a 2-cm active-tip needle may carry a risk of thermal injury to neural tissue, even for a spinal lesion without cortical bone defect. However, by using a 1-cm active-tip needle, which was relatively safe in an in vivo intact cortical bone model, the temperature in the spinal canal with no intact cortex between the tumor and spinal cord reached a temperature that potentially induces thermal injury to nerve tissue.
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ADVANCES IN KNOWLEDGE
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- Radiofrequency (RF) ablation, as used in our swine study, may carry a risk of thermal injury to neural tissue, even for a spinal lesion without a cortical defect.
- By using a 1-cm active-tip needle, which was relatively safe in an in vivo intact cortical bone model, the temperature in the spinal canal with no intact cortex between the tumor and spinal cord reached a temperature that potentially induces thermal injury to nerve tissue.
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IMPLICATION FOR PATIENT CARE
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- RF ablation may carry a risk of thermal injury to the spinal canal neural tissue, even if the lesion does not have a cortical bone defect.
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FOOTNOTES
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Abbreviations: RF = radiofrequency
Author contributions: Guarantors of integrity of entire study, all authors; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; approval of final version of submitted manuscript, all authors; literature research, T.K.; experimental studies, all authors; statistical analysis, T.K.; and manuscript editing, T.O.
Authors stated no financial relationship to disclose.
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References
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|---|
- Rosenthal DI, Alexander A, Rosenberg AE, Springfield D. Ablation of osteoid osteoma with a percutaneously placed electrode: a new procedure. Radiology 1992;183:29–33.[Abstract/Free Full Text]
- Rosenthal DI, Springfield D, Gebhardt MC, Rosenberg AE, Mankin HJ. Osteoid osteoma: percutaneous radio-frequency ablation. Radiology 1995;197:451–454.[Abstract/Free Full Text]
- Rosenthal DI, Hornicek FJ, Wolfe MW, Jennings LC, Gebhardt MC, Mankin HJ. Percutaneous radiofrequency coagulation of osteoid osteoma compared with operative treatment. J Bone Joint Surg Am 1998;80:815–821.[Abstract/Free Full Text]
- Dupuy DE, Hong R, Oliver B, Goldberg SN. Radiofrequency ablation of spinal tumors: temperature distribution in the spinal canal. AJR Am J Roentgenol 2000;175:1263–1266.[Free Full Text]
- Gronemeyer DH, Schirp S, Gevargez A. Image-guided radiofrequency ablation of spinal tumors: preliminary experience with an expandable array electrode. Cancer J 2002;8:33–39.[Medline]
- Callstrom MR, Charboneau JW, Goetz MP, et al. Painful metastases involving bone: feasibility of percutaneous CT- and US-guided radio-frequency ablation. Radiology 2002;224:87–97.[Abstract/Free Full Text]
- Schaefer O, Lohrmann C, Markmiller M, Uhrmeister P, Langer M. Technical innovation: combined treatment of a spinal metastasis with radiofrequency heat ablation and vertebroplasty. AJR Am J Roentgenol 2003;180:1075–1077.[Free Full Text]
- Schaefer O, Lohrmann C, Herling M, Uhrmeister P, Langer M. Combined radiofrequency thermal ablation and percutaneous cementoplasty treatment of a pathologic fracture. J Vasc Interv Radiol 2002;13:1047–1050.[CrossRef][Medline]
- Goetz MP, Callstrom MR, Charboneau JW, et al. Percutaneous image-guided radiofrequency ablation of painful metastases involving bone: a multicenter study. J Clin Oncol 2004;22:300–306.[Abstract/Free Full Text]
- Rossi S, Di Stasi M, Buscarini E, et al. Percutaneous RF interstitial thermal ablation in the treatment of hepatic cancer. AJR Am J Roentgenol 1996;167:759–768.[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]
- Livraghi T, Goldberg SN, Lazzaroni S, Meloni F, Solbiati L, Gazelle GS. Small hepatocellular carcinoma: treatment with radiofrequency ablation versus ethanol injection. Radiology 1999;210:655–666.[Abstract/Free Full Text]
- Livraghi T, Goldberg SN, Lazzaroni S, et al. Hepatocellular carcinoma: radiofrequency ablation of medium and large lesions. Radiology 2000;214:761–768.[Abstract/Free Full Text]
- Solbiati L, Goldberg SN, Ierace T, et al. Hepatic metastases: percutaneous radio-frequency ablation with cooled-tip electrode. Radiology 1997;205:367–373.[Abstract/Free Full Text]
- Selli C, Scott CA, Garbagnati F, et al. Transurethral radiofrequency thermal ablation of prostatic tissue: a feasibility study in humans. Urology 2001;57:78–82.[CrossRef][Medline]
- Djavan B, Susani M, Shariat S, et al. Transperineal radiofrequency interstitial tumor ablation (RITA) of the prostate. Tech Urol 1998;4:103–109.[Medline]
- Zlotta AR, Wildschutz T, Raviv G, et al. Radiofrequency interstitial tumor ablation (RITA) is a possible new modality for treatment of renal cancer: ex vivo and in vivo experience. J Endourol 1997;11:251–258.[Medline]
- Mayo-Smith WW, Dupuy DE, Parikh PM, Pezzullo JA, Cronan JJ. Imaging-guided percutaneous radiofrequency ablation of solid renal masses: techniques and outcomes of 38 treatment sessions in 32 consecutive patients. AJR Am J Roentgenol 2003;180:1503–1508.[Abstract/Free Full Text]
- Ogan K, Jacomides L, Dolmatch BL, et al. Percutaneous radiofrequency ablation for renal tumors: technique, limitation, and morbidity. Urology 2002;60:954–958.[CrossRef][Medline]
- Dupuy DE, Mayo-Smith WW, Abbott GF, DiPetrillo T. Clinical applications of radiofrequency tumor ablation in the thorax. RadioGraphics 2002;22(Spec Issue):S259–S269.[Abstract/Free Full Text]
- Mia Y, Ni Y, Yu J, Zhang H, Marchal G. Evaluation of radiofrequency ablation as an alternative for the treatment of brain tumor in rabbits. J Neurooncol 2002;56:119–126.[CrossRef][Medline]
- Merkle EM, Haaga JR, Duerk JL, Jacobs GH, Brambs HJ, Lewin JS. MR imaging-guided radio-frequency thermal ablation in the pancreas in a porcine model with a modified clinical C-arm system. Radiology 1999;213:461–467.[Abstract/Free Full Text]
- Jeffrey SS, Birdwell RL, Ikeda DM, et al. Radiofrequency ablation of breast cancer: first report of an emerging technology. Arch Surg 1999;134:1064–1068.[Abstract/Free Full Text]
- Hayashi AH, Silver SF, van der Westhuizen NG, et al. Treatment of invasive breast carcinoma with ultrasound-guided radiofrequency ablation. Am J Surg 2003;185:429–435.[CrossRef][Medline]
- Froese G, Das RM, Dunscombe PB. The sensitivity of the thoracolumbar spinal cord of the mouse to hyperthermia. Radiat Res 1991;125:173–180.[Medline]
- Letcher FS, Goldring S. The effect of radiofrequency current and heat on peripheral nerve action potential in the cat. J Neurosurg 1968;29:42–47.[Medline]
- Nakatsuka A, Yamakado K, Maeda M, et al. Radiofrequency ablation combined with bone cement injection for the treatment of bone malignancies. J Vasc Interv Radiol 2004;15:707–712.[Medline]
- Nour SG, Aschoff AJ, Mitchell IC, Emancipator SN, Duerk JL, Lewin JS. MR imaging-guided radio-frequency thermal ablation of the lumbar vertebrae in porcine models. Radiology 2002;224:452–462.[Abstract/Free Full Text]
- McDannold NJ, King RL, Jolesz FA, Hynynen KH. Usefulness of MR imaging-derived thermometry and dosimetry in determining the threshold for tissue damage induced by thermal surgery in rabbits. Radiology 2000;216:517–523.[Abstract/Free Full Text]
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ABSTRACT
INTRODUCTION
