DOI: 10.1148/radiol.2362041107
(Radiology 2005;236:716-724.)
© RSNA, 2005
Vascular and Interventional Radiology |
Renal Tumors: MR Imaging–guided Percutaneous Cryotherapy—Initial Experience in 23 Patients1
Stuart G. Silverman, MD,
Kemal Tuncali, MD,
Eric vanSonnenberg, MD,
Paul R. Morrison, MS,
Sridhar Shankar, MD,
Nikhil Ramaiya, MD and
Jerome P. Richie, MD
1 From the Division of Abdominal Imaging and Intervention, Department of Radiology (S.G.S., K.T., E.V., P.R.M., N.R.) and Division of Urology, Department of Surgery (J.P.R.), Brigham and Women's Hospital, 75 Francis St, Boston, MA 02115; and Department of Radiology, University of Massachusetts, Worcester (S.S.). Received June 23, 2004; revision requested August 30; revision received September 27; accepted October 4. Supported in part by Galil Medical, Yokneam, Israel.
Address correspondence to S.G.S. (e-mail: sgsilverman{at}partners.org).
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ABSTRACT
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PURPOSE: To evaluate the initial clinical experience of magnetic resonance (MR) imaging–guided percutaneous cryotherapy of renal tumors.
MATERIALS AND METHODS: Twenty-six renal tumors (diameter range, 1.0–4.6 cm; mean, 2.6 cm) in 23 patients were treated with 27 cryoablation procedures by using a protocol approved by the human subjects committee at the authors' institution. The study complied with the Health Insurance Portability and Accountability Act. Written informed consent was obtained from each patient. There were 17 men and six women with an average age of 66 years (range, 43–86 years). Of 26 masses, 24 were renal cell carcinoma, one was a transitional cell carcinoma, and one was an angiomyolipoma. By using a 0.5-T open MR imaging system and general anesthesia in patients, one to five (mean, 2.4) needlelike cryoprobes were placed and lesions were ablated by using real-time MR imaging for intraprocedural monitoring of ice balls. Tumors were considered successfully ablated if they demonstrated no contrast enhancement at follow-up computed tomography or MR imaging (mean, 14 months; range, 4–30 months).
RESULTS: Twenty-four of 26 tumors were successfully ablated, 23 of which required only one treatment session. Two complications occurred in a total of 27 cryoablations: one hemorrhage, which required a blood transfusion, and one abscess, which was treated successfully with percutaneous catheter drainage.
CONCLUSION: MR imaging–guided percutaneous cryotherapy of renal tumors shows promise for the treatment of selected small renal tumors, and MR imaging can be used to monitor the treatment intraprocedurally. This technique may prove useful for ablation of renal tumors completely in one session, but long-term follow-up is needed.
© RSNA, 2005
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INTRODUCTION
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With advances in computed tomography (CT) and ultrasonography (US) and their burgeoning use in clinical practice, the number of detected renal cell carcinomas has been increasing (1,2). The mainstay of treatment is surgical excision with radical nephrectomy (3). Although treatment with radical nephrectomy has produced good results, nephron-sparing surgery has been proposed as a more appropriate treatment for small (
4-cm) renal cell carcinomas (4–8). In fact, partial nephrectomy is now recommended for small renal cell carcinomas (9).
Percutaneous thermal ablation therapies, principally radiofrequency (RF) ablation, have been advocated recently as an alternative to surgery for renal cell carcinoma; preliminary data are promising (10–14). Cryotherapy of renal tumors has been performed by using open, laparoscopic, and percutaneous approaches and is likely just as effective in ablating cancerous tissues as is RF ablation (15–21).
Although CT- and US-guided RF ablation of renal tumors has been shown to be feasible and safe, only magnetic resonance (MR) imaging guidance allows the procedure to be monitored in real time, such that the entire circumference of the treatment effects can be viewed during the treatment. Intraprocedural monitoring is valuable for two reasons: First, it maximizes the chance of completely covering the tumor during the treatment and, therefore, the chance of treating it successfully in a single treatment session. Second, it allows the operator to limit damage to normal structures, including renal parenchyma. This is particularly important in patients with solitary kidneys, multiple tumors, or renal insufficiency, in whom it is important to spare as much normal renal parenchyma as possible while achieving complete tumor ablation (22–24).
On the basis of the established effectiveness of cryotherapy for ablation of cancerous tissues, the safety benefits of percutaneous approaches, and the advantages of MR imaging in monitoring tissue effects of freezing, we treated patients' renal tumors with MR imaging–guided percutaneous cryotherapy (15,17–19, 21). The purpose of our study, therefore, was to evaluate our initial experience with MR imaging–guided percutaneous therapy of renal tumors.
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MATERIALS AND METHODS
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Interventional MR Imaging Procedure Room
Interventional guidance and monitoring for cryotherapy were performed by using a 0.5-T open-configuration MR imaging system (Signa SP; GE Medical Systems, Milwaukee, Wis) (25). Flexible surface coils, applied to the surface of the patient, over the kidneys, operated as both RF transmitters and receivers. Images were obtained by using the standard planes, in transverse, sagittal, and coronal sections; during targeting of the tumor, the imaging plane was determined with optical tracking of the handheld probe (26). Images obtained during the procedure were displayed on a monitor in the interventional MR imaging procedure room. The room also contained an anesthetic delivery system (Narcomed; North American Drager, Telford, Pa) and a patient monitoring system (MagLife C; Schiller America, Miami, Fla). The latter monitors heart rate, blood pressure, oxygen saturation of the blood, and exhaled carbon dioxide levels.
Cryotherapy System
Percutaneous cryotherapy was performed by using a Food and Drug Administration–approved cryotherapy delivery system (Cryohit; manufactured by Galil Medical, Yokneam, Israel, and distributed by Oncura, Plymouth Meeting, Pa) that is based on the conversion of high-pressure argon gas to cold low-pressure liquid by using the Joule-Thomson effect (27). This system is composed of a computer workstation, a gas distribution apparatus, and needlelike cryoprobes (27). The computer workstation and gas distribution apparatus were provided to the Brigham and Women's Hospital, Boston, Mass, to support the launching of its clinical cryotherapy program. Although one of the authors (S.G.S.) is a consultant with Oncura, all of the authors had full control of the study data and the information provided in this article. To thaw the tissues, a high-pressure gas (helium) is converted to a warm low-pressure gas. The workstation must be housed outside the procedure room because it is not MR-compatible. The gas flows through pipes that pass through the wall of the procedure room, course under the floor, and exit directly from the side of the interventional MR imaging system. Gas is delivered by using up to five MR-compatible needlelike 2.4-mm cryoprobes that are designed for placement with the trocar technique (Fig 1). Each cryoprobe is equipped with a thermocouple for monitoring of the probe-tip temperature throughout the procedure, during both freezing and thawing. The system includes a monitor that displays probe-tip temperatures and a remote control device that can be used to adjust the temperature during the procedure.
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Figure 1. MR imaging–compatible 2.4-mm-diameter 20-cm-long cryoprobe, specially designed for use in MR imaging–guided percutaneous cryotherapy, before (top) and after (bottom) formation of an ice ball (lateral diameter, 2.9 cm) in vitro with a 10-minute freeze in 8 oz (240 mL) of water.
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Patient Selection, Imaging, and Preparation
In accordance with the protocol approved by the human subjects committee at Brigham and Women's Hospital, the criterion for the inclusion of patients in this study was either biopsy-proved kidney malignancy or findings on CT scans or MR images that were interpreted as highly suspicious and likely to represent a primary or metastatic kidney tumor. Patients without biopsy-proved malignancy underwent percutaneous biopsy prior to treatment. To be included in the study, patients had to have normal or correctable hemostatic parameters, no contraindications to MR imaging, and no history of active ischemic heart disease. The latter criterion was necessary because the magnetic field of the MR imaging system distorts the S-T and T-wave segments of the electrocardiographic waveform, and these distortions can mask ischemia and other cardiac disorders. Thus, electrocardiographic waves cannot be monitored in an MR imaging procedure room (28,29). As a result, patients with recent myocardial infarction, recent symptoms of angina, or ischemic changes on the electrocardiogram were excluded from the study. All patients were referred by a urologist who suggested that the patient be evaluated for this trial. Written informed consent for enrollment in the trial and performance of the procedure was obtained from all patients. Our study complied with the Health Insurance Portability and Accountability Act.
If MR imaging had not been performed before patient referral, preprocedural MR images were acquired to serve as the baseline study with which postablation MR images could be compared and to assist in the planning of the MR imaging–guided treatment. The 1.5-T MR imaging protocol was limited to the abdomen and included transverse T2-weighted imaging with fast spin-echo (SE) (3267–7000/100 [repetition time msec/echo time msec]; echo train length, 12; section thickness, 4 mm; gap, 1 mm; field of view, 30–36 cm; n = 12), breath-hold fast-recovery fast SE (1200–2996/91–94; echo train length, 17–22; section thickness, 5 mm; gap, 1 mm; field of view, 32–40 cm; n = 11), and/or single-shot fast SE (17240–53380/184–190; section thickness, 5 mm; gap, 1 mm; field of view, 32–40; n = 7) sequences; transverse T1-weighted imaging with an SE sequence (500–800/14; section thickness, 4–5 mm; gap, 1 mm; field of view, 30–36 cm; n = 15) or spoiled gradient-recalled echo (GRE) sequence (300–400/2.2, 4.7; dual echo; flip angle, 90°; section thickness, 5 mm; gap, 1 mm; field of view, 32–40 cm; n = 8); and transverse fat-suppressed T1-weighted dynamic imaging with a spoiled GRE sequence (260–435/4.2; flip angle, 75°; section thickness, 4–6 mm; gap, 1 mm; field of view, 34–40 cm; n = 15) or a three-dimensional fast-acquisition multiple-excitation spoiled GRE sequence (5.2–7.3/1.5–2.2; flip angle, 10°; section thickness, 2.5 mm [effective]; gap, 0 mm; field of view, 32–40 cm; n = 8) before and four phases after the intravenous administration of 20 mL of contrast medium (469.01 mg gadopentetate dimeglumine per milliliter, Magnevist; Berlex Laboratories, Wayne, NJ).
Preprocedural evaluation also included an interventional radiology consultative visit (during which all preprocedural images were reviewed), imaging in the open-configuration MR imaging system to plan the approach, and a consultation with an anesthesiologist. Preprocedural laboratory tests included prothrombin time, partial thromboplastin time, hematocrit level, white blood cell count, platelet count, serum creatinine level, and serum myoglobin level.
Twenty-three patients were enrolled, including 17 men and six women. Principal indications for enrollment included comorbid disease or advanced age (n = 13), need for nephron-sparing treatment (n = 8), and patient preference (n = 2). Of eight patients who needed a nephron-sparing procedure, three had renal insufficiency (serum creatinine level of 1.5 mg/mL or greater), two had solitary kidneys, two had solitary kidneys and renal insufficiency, and one had bilateral tumors. Among the 23 patients, two had a hereditary form of renal cell carcinoma, one of whom had von Hippel–Lindau disease. The average age of the patients was 66 years (range, 43–86 years).
All patients underwent percutaneous renal mass biopsy. Percutaneous biopsy was performed during the treatment session, just prior to treatment, by using MR imaging guidance in nine patients. In 12 patients, biopsy was performed with CT guidance before the treatment session. In two patients, biopsy was performed both with CT guidance before the treatment session and with MR guidance just prior to treatment. One patient who had a history of hereditary multifocal renal cell carcinoma had two adjacent lesions with a similar appearance, and biopsy was performed in only one lesion. All percutaneous biopsies were performed by using fine-needle aspiration with a 22- and/or 20-gauge Chiba-design needle (Cook, Bloomington, Ind) or MR imaging-compatible needle (E-Z-Em, Westbury, NY), except in one case in which only an 18-gauge MR imaging-compatible needle (E-Z-Em) was used. A cytologist was present during the biopsy procedure for immediate assessment of the specimen for adequacy. Preliminary results of cytologic analysis were available during the procedure. Final cytopathologic results typically were reported 2–5 days later.
Treatment Procedures
All 26 renal tumors were treated during 24 initial treatment procedures. Fifteen tumors were in the right kidney; 11 were in the left kidney. Ten tumors were located in the upper pole, 10 in the lower pole, and six in the middle portion of the kidney. All 26 tumors underwent cryoablation during a single procedure, except for one that was re-treated; thus, there were 27 cryoablation procedures. In three patients with two tumors each, both masses were ablated in the same procedure. Two of these patients had two tumors in the same kidney: One of the patients previously had undergone a partial nephrectomy of one kidney and total nephrectomy of the contralateral kidney, and neither tumor in this patient was visible at US or CT. The other patient had one tumor in each kidney. Tumors ranged from 1.0 to 4.6 cm in diameter, with a mean diameter of 2.6 cm. All treated tumors were malignant except one angiomyolipoma, in which no evidence of fat was seen at CT and MR imaging and in which biopsy was not performed until the treatment session. Although the preliminary cytologic analysis was nondiagnostic, the mass was treated with cryoablation because the protocol allowed the treatment of suspicious renal masses. The result of biopsy of the angiomyolipoma was reported 2 days after the treatment. Malignant tumors were proved at biopsy, except in seven tumors: In four, biopsy yielded suspicious cells; in two, atypical cells. In one tumor, biopsy was nondiagnostic. The latter tumor was proved a renal cell carcinoma at surgery for local recurrence.
Procedures were performed during general anesthesia of the patient. Prophylaxis was provided for infection with 1 g intravenous cefazolin sodium (Ancef; SmithKline Beecham Pharmaceuticals, Philadelphia, Pa) administered every 8 hours for 24 hours, beginning just prior to the procedure. The 27 cryoablations were performed either by using an anterolateral approach with the patient in an oblique (30°–45°) supine position (n = 9) or by using a posterior approach with the patient prone (n = 18). Tumors were located within 1 cm of the intrarenal collecting system in 20 cryoablations and within 1 cm of the colon or small intestines in seven cases. The colon was pushed aside by the operator's finger in one case (Fig 2) and by an injection of sterile normal saline in another (Fig 3).
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Figure 2a. MR imaging–guided percutaneous cryotherapy of papillary-type renal cell carcinoma in 85-year-old woman. (a) Preprocedural transverse contrast-enhanced GRE (7.0/2.2; no echo train; section thickness, 5 mm; field of view, 40 cm) image obtained at 1.5 T shows an enhancing 1.5-cm renal mass (arrow). (b, c) Intraprocedural transverse GRE (51/10.3; number of excitations, one; no echo train; flip angle, 60°; section thickness, 8 mm; field of view, 24 cm) images obtained at 0.5 T show tumor (arrow in b) adjacent to colon (arrowhead in b) that was subsequently deflected by the operator's finger (arrow in c). (d, e) Transverse T2-weighted SE (6000/110; number of excitations, one; echo train length, 16; section thickness, 5 mm; field of view, 24 cm) images show (d) placement of cryoprobe and (e) ice ball formation in tumor. Warm gauze (arrowheads in e) was applied to prevent freezing of skin. (f) Postprocedural contrast-enhanced GRE image obtained at 1.5 T with the same sequence as a shows no evidence of tumor enhancement.
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Figure 2b. MR imaging–guided percutaneous cryotherapy of papillary-type renal cell carcinoma in 85-year-old woman. (a) Preprocedural transverse contrast-enhanced GRE (7.0/2.2; no echo train; section thickness, 5 mm; field of view, 40 cm) image obtained at 1.5 T shows an enhancing 1.5-cm renal mass (arrow). (b, c) Intraprocedural transverse GRE (51/10.3; number of excitations, one; no echo train; flip angle, 60°; section thickness, 8 mm; field of view, 24 cm) images obtained at 0.5 T show tumor (arrow in b) adjacent to colon (arrowhead in b) that was subsequently deflected by the operator's finger (arrow in c). (d, e) Transverse T2-weighted SE (6000/110; number of excitations, one; echo train length, 16; section thickness, 5 mm; field of view, 24 cm) images show (d) placement of cryoprobe and (e) ice ball formation in tumor. Warm gauze (arrowheads in e) was applied to prevent freezing of skin. (f) Postprocedural contrast-enhanced GRE image obtained at 1.5 T with the same sequence as a shows no evidence of tumor enhancement.
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Figure 2c. MR imaging–guided percutaneous cryotherapy of papillary-type renal cell carcinoma in 85-year-old woman. (a) Preprocedural transverse contrast-enhanced GRE (7.0/2.2; no echo train; section thickness, 5 mm; field of view, 40 cm) image obtained at 1.5 T shows an enhancing 1.5-cm renal mass (arrow). (b, c) Intraprocedural transverse GRE (51/10.3; number of excitations, one; no echo train; flip angle, 60°; section thickness, 8 mm; field of view, 24 cm) images obtained at 0.5 T show tumor (arrow in b) adjacent to colon (arrowhead in b) that was subsequently deflected by the operator's finger (arrow in c). (d, e) Transverse T2-weighted SE (6000/110; number of excitations, one; echo train length, 16; section thickness, 5 mm; field of view, 24 cm) images show (d) placement of cryoprobe and (e) ice ball formation in tumor. Warm gauze (arrowheads in e) was applied to prevent freezing of skin. (f) Postprocedural contrast-enhanced GRE image obtained at 1.5 T with the same sequence as a shows no evidence of tumor enhancement.
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Figure 2d. MR imaging–guided percutaneous cryotherapy of papillary-type renal cell carcinoma in 85-year-old woman. (a) Preprocedural transverse contrast-enhanced GRE (7.0/2.2; no echo train; section thickness, 5 mm; field of view, 40 cm) image obtained at 1.5 T shows an enhancing 1.5-cm renal mass (arrow). (b, c) Intraprocedural transverse GRE (51/10.3; number of excitations, one; no echo train; flip angle, 60°; section thickness, 8 mm; field of view, 24 cm) images obtained at 0.5 T show tumor (arrow in b) adjacent to colon (arrowhead in b) that was subsequently deflected by the operator's finger (arrow in c). (d, e) Transverse T2-weighted SE (6000/110; number of excitations, one; echo train length, 16; section thickness, 5 mm; field of view, 24 cm) images show (d) placement of cryoprobe and (e) ice ball formation in tumor. Warm gauze (arrowheads in e) was applied to prevent freezing of skin. (f) Postprocedural contrast-enhanced GRE image obtained at 1.5 T with the same sequence as a shows no evidence of tumor enhancement.
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Figure 2e. MR imaging–guided percutaneous cryotherapy of papillary-type renal cell carcinoma in 85-year-old woman. (a) Preprocedural transverse contrast-enhanced GRE (7.0/2.2; no echo train; section thickness, 5 mm; field of view, 40 cm) image obtained at 1.5 T shows an enhancing 1.5-cm renal mass (arrow). (b, c) Intraprocedural transverse GRE (51/10.3; number of excitations, one; no echo train; flip angle, 60°; section thickness, 8 mm; field of view, 24 cm) images obtained at 0.5 T show tumor (arrow in b) adjacent to colon (arrowhead in b) that was subsequently deflected by the operator's finger (arrow in c). (d, e) Transverse T2-weighted SE (6000/110; number of excitations, one; echo train length, 16; section thickness, 5 mm; field of view, 24 cm) images show (d) placement of cryoprobe and (e) ice ball formation in tumor. Warm gauze (arrowheads in e) was applied to prevent freezing of skin. (f) Postprocedural contrast-enhanced GRE image obtained at 1.5 T with the same sequence as a shows no evidence of tumor enhancement.
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Figure 2f. MR imaging–guided percutaneous cryotherapy of papillary-type renal cell carcinoma in 85-year-old woman. (a) Preprocedural transverse contrast-enhanced GRE (7.0/2.2; no echo train; section thickness, 5 mm; field of view, 40 cm) image obtained at 1.5 T shows an enhancing 1.5-cm renal mass (arrow). (b, c) Intraprocedural transverse GRE (51/10.3; number of excitations, one; no echo train; flip angle, 60°; section thickness, 8 mm; field of view, 24 cm) images obtained at 0.5 T show tumor (arrow in b) adjacent to colon (arrowhead in b) that was subsequently deflected by the operator's finger (arrow in c). (d, e) Transverse T2-weighted SE (6000/110; number of excitations, one; echo train length, 16; section thickness, 5 mm; field of view, 24 cm) images show (d) placement of cryoprobe and (e) ice ball formation in tumor. Warm gauze (arrowheads in e) was applied to prevent freezing of skin. (f) Postprocedural contrast-enhanced GRE image obtained at 1.5 T with the same sequence as a shows no evidence of tumor enhancement.
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Figure 3a. Percutaneous MR imaging–guided cryotherapy of 2.4-cm renal cell carcinoma in 76-year-old man with a solitary kidney. (a–c) Intraprocedural transverse T1-weighted GRE (250/2.9; no echo train; flip angle, 60°; section thickness, 8 mm; field of view, 30 cm) images obtained at 0.5 T with patient in oblique supine position show (a) colon (arrowhead) adjacent to the tumor (arrow), (b) two cryoprobes (arrow) inserted in the tumor and fine needle (arrowhead) placed in the perinephric space, and (c) displacement of the colon from the tumor with 80-mL saline injection (arrow) via the fine needle. (d) Intraprocedural transverse T2-weighted fast SE (6000/110; number of excitations, one; echo train length, 16; section thickness, 5 mm; field of view, 24 cm) image obtained at 0.5 T shows ice ball (arrow) that eclipses tumor separated from colon by injected saline (arrowhead).
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Figure 3b. Percutaneous MR imaging–guided cryotherapy of 2.4-cm renal cell carcinoma in 76-year-old man with a solitary kidney. (a–c) Intraprocedural transverse T1-weighted GRE (250/2.9; no echo train; flip angle, 60°; section thickness, 8 mm; field of view, 30 cm) images obtained at 0.5 T with patient in oblique supine position show (a) colon (arrowhead) adjacent to the tumor (arrow), (b) two cryoprobes (arrow) inserted in the tumor and fine needle (arrowhead) placed in the perinephric space, and (c) displacement of the colon from the tumor with 80-mL saline injection (arrow) via the fine needle. (d) Intraprocedural transverse T2-weighted fast SE (6000/110; number of excitations, one; echo train length, 16; section thickness, 5 mm; field of view, 24 cm) image obtained at 0.5 T shows ice ball (arrow) that eclipses tumor separated from colon by injected saline (arrowhead).
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Figure 3c. Percutaneous MR imaging–guided cryotherapy of 2.4-cm renal cell carcinoma in 76-year-old man with a solitary kidney. (a–c) Intraprocedural transverse T1-weighted GRE (250/2.9; no echo train; flip angle, 60°; section thickness, 8 mm; field of view, 30 cm) images obtained at 0.5 T with patient in oblique supine position show (a) colon (arrowhead) adjacent to the tumor (arrow), (b) two cryoprobes (arrow) inserted in the tumor and fine needle (arrowhead) placed in the perinephric space, and (c) displacement of the colon from the tumor with 80-mL saline injection (arrow) via the fine needle. (d) Intraprocedural transverse T2-weighted fast SE (6000/110; number of excitations, one; echo train length, 16; section thickness, 5 mm; field of view, 24 cm) image obtained at 0.5 T shows ice ball (arrow) that eclipses tumor separated from colon by injected saline (arrowhead).
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Figure 3d. Percutaneous MR imaging–guided cryotherapy of 2.4-cm renal cell carcinoma in 76-year-old man with a solitary kidney. (a–c) Intraprocedural transverse T1-weighted GRE (250/2.9; no echo train; flip angle, 60°; section thickness, 8 mm; field of view, 30 cm) images obtained at 0.5 T with patient in oblique supine position show (a) colon (arrowhead) adjacent to the tumor (arrow), (b) two cryoprobes (arrow) inserted in the tumor and fine needle (arrowhead) placed in the perinephric space, and (c) displacement of the colon from the tumor with 80-mL saline injection (arrow) via the fine needle. (d) Intraprocedural transverse T2-weighted fast SE (6000/110; number of excitations, one; echo train length, 16; section thickness, 5 mm; field of view, 24 cm) image obtained at 0.5 T shows ice ball (arrow) that eclipses tumor separated from colon by injected saline (arrowhead).
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During MR imaging guidance, an MR imaging–compatible cryoprobe was placed in tandem alongside an MR imaging–compatible 22–20-gauge biopsy needle (E-Z-Em) by using the trocar technique (26,27). All procedures were performed by a team consisting of one of several staff interventional radiologists (S.G.S., K.T., E.V.), each with a minimum of 7 years of experience in interventional radiology techniques, and by one of two fellows (S.S., N.R.). Additional cryoprobes (1–5 probes in total; mean, 2.4) were placed as needed to treat the tumor. In general, one cryoprobe generates an ice ball that is 2 cm in short-axis diameter (27). Therefore, to cover the tumor in all dimensions, two to three cryoprobes were used for masses that were 1–3 cm in diameter, and four to five cryoprobes were used for larger masses. Two freeze-thaw cycles (15-minute freeze, 10-minute thaw) were used. During freezing, cryoprobe-tip temperatures reached a nadir of approximately –130°C. Repetitive imaging every 1–3 minutes by using a T2-weighted fast SE (3000–6200/92–110; echo train length, 8–16; section thickness, 5–8 mm; field of view, 22–30 cm; n = 15) or GRE (24–250/10–13; flip angle, 60°–90°; section thickness, 5–8 mm; field of view, 20–32 cm; n = 11) sequence or a T1-weighted fast SE (400/18; echo train length, four; section thickness, 8 mm; field of view, 26 cm; n = 1) sequence was applied in one or two different planes to monitor ice ball formation and tumor coverage. Acquisition times ranged from 20 to 60 seconds. The frequency with which the ice balls were imaged was related to the rate at which they formed. Imaging every 1–3 minutes was frequent enough to monitor progress in ice ball formation. If the ice ball did not encompass the tumor entirely and include a 5-mm margin of tissue beyond the tumor, additional cryoprobes were placed.
Imaging and Laboratory Evaluation
At the end of the treatment procedure, transverse T2-weighted fast SE imaging (3000–5000/92; echo train length, eight; section thickness, 10 mm; field of view, 28–32 cm) was performed through the kidneys. Patients were observed in the recovery room for 2 hours and then were admitted for a short period during which they were observed and monitored and blood tests were performed. Serum hematocrit level, platelet count, creatinine level, and myoglobin level were measured at 12 and 24 hours and at 1 week after the procedure.
MR imaging with a 1.5-T system and with the same protocol used prior to the treatment was performed also at 24–48 hours after treatment for assessment of complications such as bleeding or urinoma formation. MR images from this examination also were compared with the pretreatment MR images to determine the amount of cryonecrosis, defined as tissues that no longer appeared to be enhanced by intravenous contrast material. Follow-up MR images, obtained at 3-month intervals for the 1st year and every 6–12 months (mean, 14 months; range, 4–30 months) thereafter, were read in consensus by two radiologists (S.G.S., K.T.), each with a minimum of 5 years of experience in reading renal MR images. Tumors were considered completely ablated if there was no evidence of tumor enhancement by intravenous contrast material.
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RESULTS
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All but two tumors were completely ablated, and all but three tumors were completely ablated with a single session of treatment. All tumors that were considered completely ablated showed no contrast material enhancement after treatment. One tumor was not contrast-enhanced prior to treatment, and all follow-up MR images demonstrated no tumor growth and no enhancement in the surrounding renal parenchyma (Fig 3). The first two patients enrolled in the trial had small residual enhanced nodules at the periphery of the lesion; both of these nodules were detected at 24–48 hours after the procedure. One of these patients, who underwent cryotherapy for a small (2.0-cm) renal cell carcinoma, had been undergoing treatment also for ovarian cancer. The renal cell carcinoma was not re-treated, because the ovarian cancer had progressed. The other patient's tumor, also a 2.0-cm renal cell carcinoma, showed residual enhancement in the portion that abutted the collecting system. The only indication for ablation in this case was patient preference, and the patient elected to undergo partial nephrectomy rather than repeat ablation. The third patient who had a recurrent tumor was suspected to have a small residual nodule on the basis of findings on 6-month follow-up MR images; the residual nodule was confirmed at 9-month MR imaging, was biopsy proved at 10 months, and was successfully re-treated at 11 months. MR images obtained in this patient at 3 months after initial treatment did not show evidence of recurrence, even in retrospect. The ice balls were seen as sharply delineated regions of signal void on fast SE and GRE MR images. These regions could be distinguished from unfrozen tumor and unfrozen renal parenchyma (Figs 2–6).
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Figure 4a. Percutaneous MR imaging–guided cryotherapy of two small renal cell carcinomas after ipsilateral partial nephrectomy and contralateral nephrectomy in 58-year-old man with renal insufficiency. (a, b) Preprocedural transverse contrast-enhanced GRE (450/4.2; number of excitations, one; section thickness, 4 mm; field of view, 40 cm) images obtained at 1.5 T show (a) 2.2-cm enhancing mass (arrow) in the anterior aspect of the middle portion of the right kidney and (b) 1.5-cm enhancing mass (arrowhead) in the posterior aspect of the middle portion of the right kidney. (c–f) Intraprocedural transverse T2-weighted fast SE (6000/92; number of excitations, one; echo train length, 16; section thickness, 8 mm; field of view, 28 cm) images obtained at 0.5 T show (c) cryoprobe (arrow) in anterior tumor, (d) signal void where ice ball (arrowhead) eclipses anterior tumor, (e) cryoprobe (arrow) in posterior tumor, and (f) ice ball (arrowhead) that eclipses posterior tumor. (g, h) Postprocedural MR images obtained at 10 months with 1.5 T and same parameters as a and b show virtually complete resolution of tumors in (g) anterior and (h) posterior sites. The serum creatinine level rose transiently from a preprocedural value of 2.5 to 3.0 mg/mL after the procedure, then returned to the baseline value.
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Figure 4b. Percutaneous MR imaging–guided cryotherapy of two small renal cell carcinomas after ipsilateral partial nephrectomy and contralateral nephrectomy in 58-year-old man with renal insufficiency. (a, b) Preprocedural transverse contrast-enhanced GRE (450/4.2; number of excitations, one; section thickness, 4 mm; field of view, 40 cm) images obtained at 1.5 T show (a) 2.2-cm enhancing mass (arrow) in the anterior aspect of the middle portion of the right kidney and (b) 1.5-cm enhancing mass (arrowhead) in the posterior aspect of the middle portion of the right kidney. (c–f) Intraprocedural transverse T2-weighted fast SE (6000/92; number of excitations, one; echo train length, 16; section thickness, 8 mm; field of view, 28 cm) images obtained at 0.5 T show (c) cryoprobe (arrow) in anterior tumor, (d) signal void where ice ball (arrowhead) eclipses anterior tumor, (e) cryoprobe (arrow) in posterior tumor, and (f) ice ball (arrowhead) that eclipses posterior tumor. (g, h) Postprocedural MR images obtained at 10 months with 1.5 T and same parameters as a and b show virtually complete resolution of tumors in (g) anterior and (h) posterior sites. The serum creatinine level rose transiently from a preprocedural value of 2.5 to 3.0 mg/mL after the procedure, then returned to the baseline value.
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Figure 4c. Percutaneous MR imaging–guided cryotherapy of two small renal cell carcinomas after ipsilateral partial nephrectomy and contralateral nephrectomy in 58-year-old man with renal insufficiency. (a, b) Preprocedural transverse contrast-enhanced GRE (450/4.2; number of excitations, one; section thickness, 4 mm; field of view, 40 cm) images obtained at 1.5 T show (a) 2.2-cm enhancing mass (arrow) in the anterior aspect of the middle portion of the right kidney and (b) 1.5-cm enhancing mass (arrowhead) in the posterior aspect of the middle portion of the right kidney. (c–f) Intraprocedural transverse T2-weighted fast SE (6000/92; number of excitations, one; echo train length, 16; section thickness, 8 mm; field of view, 28 cm) images obtained at 0.5 T show (c) cryoprobe (arrow) in anterior tumor, (d) signal void where ice ball (arrowhead) eclipses anterior tumor, (e) cryoprobe (arrow) in posterior tumor, and (f) ice ball (arrowhead) that eclipses posterior tumor. (g, h) Postprocedural MR images obtained at 10 months with 1.5 T and same parameters as a and b show virtually complete resolution of tumors in (g) anterior and (h) posterior sites. The serum creatinine level rose transiently from a preprocedural value of 2.5 to 3.0 mg/mL after the procedure, then returned to the baseline value.
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Figure 4d. Percutaneous MR imaging–guided cryotherapy of two small renal cell carcinomas after ipsilateral partial nephrectomy and contralateral nephrectomy in 58-year-old man with renal insufficiency. (a, b) Preprocedural transverse contrast-enhanced GRE (450/4.2; number of excitations, one; section thickness, 4 mm; field of view, 40 cm) images obtained at 1.5 T show (a) 2.2-cm enhancing mass (arrow) in the anterior aspect of the middle portion of the right kidney and (b) 1.5-cm enhancing mass (arrowhead) in the posterior aspect of the middle portion of the right kidney. (c–f) Intraprocedural transverse T2-weighted fast SE (6000/92; number of excitations, one; echo train length, 16; section thickness, 8 mm; field of view, 28 cm) images obtained at 0.5 T show (c) cryoprobe (arrow) in anterior tumor, (d) signal void where ice ball (arrowhead) eclipses anterior tumor, (e) cryoprobe (arrow) in posterior tumor, and (f) ice ball (arrowhead) that eclipses posterior tumor. (g, h) Postprocedural MR images obtained at 10 months with 1.5 T and same parameters as a and b show virtually complete resolution of tumors in (g) anterior and (h) posterior sites. The serum creatinine level rose transiently from a preprocedural value of 2.5 to 3.0 mg/mL after the procedure, then returned to the baseline value.
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Figure 4e. Percutaneous MR imaging–guided cryotherapy of two small renal cell carcinomas after ipsilateral partial nephrectomy and contralateral nephrectomy in 58-year-old man with renal insufficiency. (a, b) Preprocedural transverse contrast-enhanced GRE (450/4.2; number of excitations, one; section thickness, 4 mm; field of view, 40 cm) images obtained at 1.5 T show (a) 2.2-cm enhancing mass (arrow) in the anterior aspect of the middle portion of the right kidney and (b) 1.5-cm enhancing mass (arrowhead) in the posterior aspect of the middle portion of the right kidney. (c–f) Intraprocedural transverse T2-weighted fast SE (6000/92; number of excitations, one; echo train length, 16; section thickness, 8 mm; field of view, 28 cm) images obtained at 0.5 T show (c) cryoprobe (arrow) in anterior tumor, (d) signal void where ice ball (arrowhead) eclipses anterior tumor, (e) cryoprobe (arrow) in posterior tumor, and (f) ice ball (arrowhead) that eclipses posterior tumor. (g, h) Postprocedural MR images obtained at 10 months with 1.5 T and same parameters as a and b show virtually complete resolution of tumors in (g) anterior and (h) posterior sites. The serum creatinine level rose transiently from a preprocedural value of 2.5 to 3.0 mg/mL after the procedure, then returned to the baseline value.
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Figure 4f. Percutaneous MR imaging–guided cryotherapy of two small renal cell carcinomas after ipsilateral partial nephrectomy and contralateral nephrectomy in 58-year-old man with renal insufficiency. (a, b) Preprocedural transverse contrast-enhanced GRE (450/4.2; number of excitations, one; section thickness, 4 mm; field of view, 40 cm) images obtained at 1.5 T show (a) 2.2-cm enhancing mass (arrow) in the anterior aspect of the middle portion of the right kidney and (b) 1.5-cm enhancing mass (arrowhead) in the posterior aspect of the middle portion of the right kidney. (c–f) Intraprocedural transverse T2-weighted fast SE (6000/92; number of excitations, one; echo train length, 16; section thickness, 8 mm; field of view, 28 cm) images obtained at 0.5 T show (c) cryoprobe (arrow) in anterior tumor, (d) signal void where ice ball (arrowhead) eclipses anterior tumor, (e) cryoprobe (arrow) in posterior tumor, and (f) ice ball (arrowhead) that eclipses posterior tumor. (g, h) Postprocedural MR images obtained at 10 months with 1.5 T and same parameters as a and b show virtually complete resolution of tumors in (g) anterior and (h) posterior sites. The serum creatinine level rose transiently from a preprocedural value of 2.5 to 3.0 mg/mL after the procedure, then returned to the baseline value.
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Figure 4g. Percutaneous MR imaging–guided cryotherapy of two small renal cell carcinomas after ipsilateral partial nephrectomy and contralateral nephrectomy in 58-year-old man with renal insufficiency. (a, b) Preprocedural transverse contrast-enhanced GRE (450/4.2; number of excitations, one; section thickness, 4 mm; field of view, 40 cm) images obtained at 1.5 T show (a) 2.2-cm enhancing mass (arrow) in the anterior aspect of the middle portion of the right kidney and (b) 1.5-cm enhancing mass (arrowhead) in the posterior aspect of the middle portion of the right kidney. (c–f) Intraprocedural transverse T2-weighted fast SE (6000/92; number of excitations, one; echo train length, 16; section thickness, 8 mm; field of view, 28 cm) images obtained at 0.5 T show (c) cryoprobe (arrow) in anterior tumor, (d) signal void where ice ball (arrowhead) eclipses anterior tumor, (e) cryoprobe (arrow) in posterior tumor, and (f) ice ball (arrowhead) that eclipses posterior tumor. (g, h) Postprocedural MR images obtained at 10 months with 1.5 T and same parameters as a and b show virtually complete resolution of tumors in (g) anterior and (h) posterior sites. The serum creatinine level rose transiently from a preprocedural value of 2.5 to 3.0 mg/mL after the procedure, then returned to the baseline value.
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Figure 4h. Percutaneous MR imaging–guided cryotherapy of two small renal cell carcinomas after ipsilateral partial nephrectomy and contralateral nephrectomy in 58-year-old man with renal insufficiency. (a, b) Preprocedural transverse contrast-enhanced GRE (450/4.2; number of excitations, one; section thickness, 4 mm; field of view, 40 cm) images obtained at 1.5 T show (a) 2.2-cm enhancing mass (arrow) in the anterior aspect of the middle portion of the right kidney and (b) 1.5-cm enhancing mass (arrowhead) in the posterior aspect of the middle portion of the right kidney. (c–f) Intraprocedural transverse T2-weighted fast SE (6000/92; number of excitations, one; echo train length, 16; section thickness, 8 mm; field of view, 28 cm) images obtained at 0.5 T show (c) cryoprobe (arrow) in anterior tumor, (d) signal void where ice ball (arrowhead) eclipses anterior tumor, (e) cryoprobe (arrow) in posterior tumor, and (f) ice ball (arrowhead) that eclipses posterior tumor. (g, h) Postprocedural MR images obtained at 10 months with 1.5 T and same parameters as a and b show virtually complete resolution of tumors in (g) anterior and (h) posterior sites. The serum creatinine level rose transiently from a preprocedural value of 2.5 to 3.0 mg/mL after the procedure, then returned to the baseline value.
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Figure 5a. Single-session MR imaging–guided cryotherapy of bilateral renal cell carcinoma in 62-year-old-man. (a, b) Preprocedural transverse contrast-enhanced GRE (7.5/1.4; no echo train; section thickness, 5 mm; field of view, 39 cm) images obtained at 1.5 T show (a) 4.0-cm renal cell carcinoma (arrow) in the right kidney and (b) 4.2-cm renal cell carcinoma (arrow) in the left kidney. (c, d) Intraprocedural transverse GRE (51/10.3; number of excitations, one; flip angle, 60°; section thickness, 6 mm; field of view, 24 cm) images obtained at 0.5 T show ice balls (arrows) eclipsing both tumors. (e, f) Postprocedural contrast-enhanced MR images obtained at 1.5 T with the same parameters as a and b show no evidence of contrast enhancement in the tumor sites.
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Figure 5b. Single-session MR imaging–guided cryotherapy of bilateral renal cell carcinoma in 62-year-old-man. (a, b) Preprocedural transverse contrast-enhanced GRE (7.5/1.4; no echo train; section thickness, 5 mm; field of view, 39 cm) images obtained at 1.5 T show (a) 4.0-cm renal cell carcinoma (arrow) in the right kidney and (b) 4.2-cm renal cell carcinoma (arrow) in the left kidney. (c, d) Intraprocedural transverse GRE (51/10.3; number of excitations, one; flip angle, 60°; section thickness, 6 mm; field of view, 24 cm) images obtained at 0.5 T show ice balls (arrows) eclipsing both tumors. (e, f) Postprocedural contrast-enhanced MR images obtained at 1.5 T with the same parameters as a and b show no evidence of contrast enhancement in the tumor sites.
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Figure 5c. Single-session MR imaging–guided cryotherapy of bilateral renal cell carcinoma in 62-year-old-man. (a, b) Preprocedural transverse contrast-enhanced GRE (7.5/1.4; no echo train; section thickness, 5 mm; field of view, 39 cm) images obtained at 1.5 T show (a) 4.0-cm renal cell carcinoma (arrow) in the right kidney and (b) 4.2-cm renal cell carcinoma (arrow) in the left kidney. (c, d) Intraprocedural transverse GRE (51/10.3; number of excitations, one; flip angle, 60°; section thickness, 6 mm; field of view, 24 cm) images obtained at 0.5 T show ice balls (arrows) eclipsing both tumors. (e, f) Postprocedural contrast-enhanced MR images obtained at 1.5 T with the same parameters as a and b show no evidence of contrast enhancement in the tumor sites.
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Figure 5d. Single-session MR imaging–guided cryotherapy of bilateral renal cell carcinoma in 62-year-old-man. (a, b) Preprocedural transverse contrast-enhanced GRE (7.5/1.4; no echo train; section thickness, 5 mm; field of view, 39 cm) images obtained at 1.5 T show (a) 4.0-cm renal cell carcinoma (arrow) in the right kidney and (b) 4.2-cm renal cell carcinoma (arrow) in the left kidney. (c, d) Intraprocedural transverse GRE (51/10.3; number of excitations, one; flip angle, 60°; section thickness, 6 mm; field of view, 24 cm) images obtained at 0.5 T show ice balls (arrows) eclipsing both tumors. (e, f) Postprocedural contrast-enhanced MR images obtained at 1.5 T with the same parameters as a and b show no evidence of contrast enhancement in the tumor sites.
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Figure 5e. Single-session MR imaging–guided cryotherapy of bilateral renal cell carcinoma in 62-year-old-man. (a, b) Preprocedural transverse contrast-enhanced GRE (7.5/1.4; no echo train; section thickness, 5 mm; field of view, 39 cm) images obtained at 1.5 T show (a) 4.0-cm renal cell carcinoma (arrow) in the right kidney and (b) 4.2-cm renal cell carcinoma (arrow) in the left kidney. (c, d) Intraprocedural transverse GRE (51/10.3; number of excitations, one; flip angle, 60°; section thickness, 6 mm; field of view, 24 cm) images obtained at 0.5 T show ice balls (arrows) eclipsing both tumors. (e, f) Postprocedural contrast-enhanced MR images obtained at 1.5 T with the same parameters as a and b show no evidence of contrast enhancement in the tumor sites.
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Figure 5f. Single-session MR imaging–guided cryotherapy of bilateral renal cell carcinoma in 62-year-old-man. (a, b) Preprocedural transverse contrast-enhanced GRE (7.5/1.4; no echo train; section thickness, 5 mm; field of view, 39 cm) images obtained at 1.5 T show (a) 4.0-cm renal cell carcinoma (arrow) in the right kidney and (b) 4.2-cm renal cell carcinoma (arrow) in the left kidney. (c, d) Intraprocedural transverse GRE (51/10.3; number of excitations, one; flip angle, 60°; section thickness, 6 mm; field of view, 24 cm) images obtained at 0.5 T show ice balls (arrows) eclipsing both tumors. (e, f) Postprocedural contrast-enhanced MR images obtained at 1.5 T with the same parameters as a and b show no evidence of contrast enhancement in the tumor sites.
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Figure 6. Percutaneous MR imaging–guided cryotherapy of renal cell carcinoma in 68-year-old man. (a, b) Intraprocedural transverse T2-weighted fast SE (4000/110; echo train length, eight; section thickness, 6 mm; field of view, 28 cm) images obtained at 0.5 T in prone patient show (a) cryoprobe inserted into 1.8-cm mass (arrow) in lower pole of left kidney and (b) ice ball eclipsing tumor. (c) Intraprocedural coronal T1-weighted spoiled GRE (250/10.1; number of excitations, one; no echo train; flip angle, 60°; section thickness, 6 cm; field of view, 28 cm) image obtained at 0.5 T to monitor ice ball formation shows complete tumor cryoablation and avoidance of ablation of the intrarenal collecting system (arrow).
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Figure 6. Percutaneous MR imaging–guided cryotherapy of renal cell carcinoma in 68-year-old man. (a, b) Intraprocedural transverse T2-weighted fast SE (4000/110; echo train length, eight; section thickness, 6 mm; field of view, 28 cm) images obtained at 0.5 T in prone patient show (a) cryoprobe inserted into 1.8-cm mass (arrow) in lower pole of left kidney and (b) ice ball eclipsing tumor. (c) Intraprocedural coronal T1-weighted spoiled GRE (250/10.1; number of excitations, one; no echo train; flip angle, 60°; section thickness, 6 cm; field of view, 28 cm) image obtained at 0.5 T to monitor ice ball formation shows complete tumor cryoablation and avoidance of ablation of the intrarenal collecting system (arrow).
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Figure 6. Percutaneous MR imaging–guided cryotherapy of renal cell carcinoma in 68-year-old man. (a, b) Intraprocedural transverse T2-weighted fast SE (4000/110; echo train length, eight; section thickness, 6 mm; field of view, 28 cm) images obtained at 0.5 T in prone patient show (a) cryoprobe inserted into 1.8-cm mass (arrow) in lower pole of left kidney and (b) ice ball eclipsing tumor. (c) Intraprocedural coronal T1-weighted spoiled GRE (250/10.1; number of excitations, one; no echo train; flip angle, 60°; section thickness, 6 cm; field of view, 28 cm) image obtained at 0.5 T to monitor ice ball formation shows complete tumor cryoablation and avoidance of ablation of the intrarenal collecting system (arrow).
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There were two major complications. One patient's hematocrit level decreased from 34% (baseline) to 24% at 48 hours after the procedure; she received 1 U of blood, and, at 1 week, the hematocrit level had returned to the baseline value. One elderly patient developed an abscess after ablation of a 4.6-cm exophytic renal cell carcinoma, the largest tumor in our patient series. The abscess was caused by the inadvertent freezing of adjacent colon. A fistula developed that affected both the colon and the intrarenal collecting system. After CT-guided percutaneous catheter drainage, the abscess resolved and both fistulas healed. In retrospect, intraprocedural MR images had shown that the ice ball overlapped with adjacent colon at the site of injury. All other patients tolerated the procedure well. All but four patients were discharged on the 1st day after the procedure. Three patients were kept in the hospital an additional 1 or 2 days for treatment of unrelated comorbid illnesses. One patient was kept in the hospital 1 additional day for monitoring of an elevated serum myoglobin level. Patients experienced mild flank discomfort that was well controlled with narcotic analgesia in the recovery room and that resolved within 1 to 2 hours.
There was no change in the serum creatinine level except in one patient who had two tumors in a solitary kidney that had undergone a partial nephrectomy (Fig 2). His serum creatinine level rose transiently from 2.5 to 3.0 mg/mL and then returned to the baseline value. The serum myoglobin level was elevated at 12 hours after 22 of 24 procedures; only in one patient was the myoglobin level higher than 1000 ng/mL (normal range, 0–100 ng/mL). To prevent renal damage, this patient received 0.3 g/kg D-mannitol (Abbott Laboratories, North Chicago, Ill) and 5% dextrose in water (D5W; Abbott Laboratories) with three ampules of sodium bicarbonate (50 mEq per ampule) intravenously at a rate of 150 mL/h for 24 hours. Platelet counts trended downward, but no levels were below normal. At 1 week, all patients were either asymptomatic or reported mild flank discomfort and had resumed their usual daily activities.
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DISCUSSION
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Our initial experience suggests that MR imaging–guided percutaneous cryotherapy of kidney tumors is a successful technique. When the elimination of contrast enhancement at follow-up MR imaging was used as the measure of success, tumors in all but the first two patients enrolled in the trial were treated successfully. MR imaging allowed us to monitor the freezing process and ensure that the ice ball covered the tumor completely in all dimensions. On the basis of views of the developing ice ball and its relationship to the tumor, we were able to reposition the cryoprobes as necessary. The extremely short T2 relaxation time of ice provides clear delineation of the ice ball, which is depicted as a signal void (27,30–33). With the use of either T1- or T2-weighted sequences, excellent contrast between the ice ball, the kidney, and the tumor can be achieved in multiple planes (30–33) (Figs 3–6). The ability to visualize the ice ball with MR imaging in multiple planes allowed the operator to determine the margins of ablative effects and to be more confident that the tumor was treated completely. This information increased the chances of treating tumors in one session. Twenty-three of the 26 tumors in our patient series were treated completely in one session, including bilateral tumors in one patient.
Unlike CT, MR imaging does not subject the patient and health care personnel to the potential harmful effects of ionizing radiation. The ability to monitor the effects of freezing during the procedure is another advantage of MR imaging–guided cryotherapy over CT-guided RF ablation. During CT-guided RF ablation, the coverage of a tumor can be estimated only from the expected result with a given RF ablation probe. Although tumor ablation with RF is performed with image guidance, the amount of necrosis achieved with RF ablation cannot be reliably predicted and is not reflected accurately at US and CT. Contrast-enhanced CT can be performed after the procedure to check for untreated portions of tumor. However, contrast material can be administered only once or twice during the procedure. If a contrast-enhanced CT scan is not obtained until 1 day or 1 week later and residual tumor is identified on the scan, patients must be re-treated at a later session. With CT-guided RF ablation used to treat renal tumors, 54 sessions were needed to treat 42 tumors in one patient series (11), and 38 sessions were needed to treat 32 tumors in another series (34); however, only 24 sessions were needed to treat 24 tumors successfully in another (13). Although US does not accurately depict the zone of necrosis produced by RF ablation, new contrast agents are being developed for use at intraprocedural US to assess necrosis (35). Experience, however, has been limited to the liver, and results are preliminary (35).
MR imaging also was used for intraprocedural guidance. The entire procedure was conducted with MR imaging guidance, including the targeting of the tumor and monitoring of ice ball formation. MR imaging also provided guidance for the operator to push the colon away from the tumor in one case, and it provided visualization for the injection of saline to deviate the colon in another. This technique of the injection of water to distance a critical nearby structure from a renal tumor has been previously described (36).
All three treatment failures (including those in the first two patients enrolled in the study) occurred early in our experience. In retrospect, intraprocedurally depicted ice balls did not cover the tumors completely; we erred on the side of caution to avoid damaging the adjacent collecting system and surrounding structures. As we gained more confidence in the safety of the technique, we were able to extend the ice ball so that tumors were completely covered. No tumor recurrences have been observed to date in patients in whom the ice ball was seen to cover the tumor intraprocedurally. As was shown in the liver, ice balls that were depicted intraprocedurally predicted cryonecrosis (27).
Renal cell carcinoma has been treated successfully with cryotherapy in the past (15–17,21). The percutaneous treatment of renal cell carcinoma by using cryotherapy with MR imaging guidance, however, has received little attention (18–20). Prior reports described probe placement with the Seldinger technique, the same technique employed during prostate cryotherapy and liver cryosurgery (18–20). Our probes could be placed by using the trocar technique, and, therefore, no sheaths, guidewires, or dilators were required.
Percutaneous MR imaging-guided cryotherapy of renal tumors proved safe. Overall, the treatment was well tolerated. Postprocedural recovery was satisfactory, and patients were able to return to their usual daily activities within several days. One patient experienced a perinephric hematoma that required a blood transfusion. There was no underlying coagulopathy or other reason for bleeding in this case. Perinephric hematoma is a frequent sequela of renal tumor ablation but usually is self limited (11). The treatment of a 4.6-cm renal cell carcinoma, the largest in the series, led to abscess formation and fistulas that involved both the renal calyx and the colon. Although the fistulas healed and the abscess was treated successfully with percutaneous drainage, this case deserves an explanation. The tumor was only one of seven tumors that was situated less than 1 cm from the colon and only one of 20 that were close to the collecting system. Although MR images obtained for monitoring displayed the relationship of the ice ball to the colon in two planes, the ice ball was extended to cover this large tumor completely, and in this process, the ice ball increased in size until it abutted the colon. As the ice ball edge represents a tissue temperature of approximately 0°C and is nonlethal, it was presumed that the colon would not be harmed. In retrospect, however, because both gas and ice were displayed as signal voids, the degree to which the two overlapped could not be ascertained, and the ice ball extended too far into the colon. As a result of this case, we now maintain a visible fat plane between the ice ball and bowel in all cases, and, when feasible, we displace the colon from the ablation site either manually or by injecting saline.
Unlike surgical treatment, in which diagnosis of a renal mass is based on a pathologist's analysis of the entire resected specimen, preprocedural diagnosis relies solely on imaging or a pretreatment percutaneous biopsy when masses are treated with percutaneous ablation. In the early part of the trial, we performed biopsies of renal masses on the day of the treatment procedure. As a result, an angiomyolipoma was inadvertently treated because the diagnosis was determined after the procedure was performed. After this occurrence, biopsies were obtained in all masses several days in advance of the treatment procedure. It has been reported that 37% of patients who are referred for ablation of presumed renal cancer harbor a benign mass (37). The inadvertent treatment of a benign renal mass can be avoided in most cases through careful preprocedural imaging analysis and biopsy of all masses that cannot be diagnosed as benign with imaging alone.
There were limitations to our study. First, as is the case with all other studies of percutaneous renal tumor ablation for which results have been published to date, we used the elimination of contrast enhancement at follow-up MR imaging or CT as the measure of treatment success, and longer periods of follow-up will be needed to consider tumors cured. The use of general anesthesia might be considered a disadvantage of our technique. Our procedures, however, lasted 3–4 hours (the total amount of time spent by the patient in the interventional MR imaging room), which is too long for conscious patients to tolerate. Furthermore, intraprocedural imaging techniques required repeated breath holding for nearly 60 seconds, which is difficult for many patients to perform. Lastly, the anecdotal evidence suggests to us that patients prefer to be asleep during long procedures.
In summary, we have described our use of a minimally invasive method for ablating renal tumors. The rationale for using MR imaging–guided percutaneous cryotherapy of renal tumors is based on two main principles: Freezing is effective in ablating tumors, and the margins of the effects can be viewed intraprocedurally with MR imaging. In this study, we demonstrated that MR imaging–guided percutaneous cryotherapy is a successful technique for treating renal tumors and that MR imaging can be used intraprocedurally to ensure that the tumor is completely treated during a single session. Although this method requires further assessment, MR imaging–guided percutaneous cryotherapy shows promise.
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ACKNOWLEDGMENTS
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The authors thank Christopher J. Doyle, MD, Kevin R. Loughlin, MD, Michael O'Leary, MD, and Graeme Steele, MD, for patient referral and surgical consultation, and Donna Vega for assistance with manuscript preparation.
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FOOTNOTES
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Abbreviations: GRE = gradient-recalled echo • RF = radiofrequency • SE = spin echo
See Materials and Methods for pertinent disclosures.
Author contributions: Guarantors of integrity of entire study, S.G.S., K.T.; study concepts, all authors; study design, S.G.S., K.T., E.V., P.R.M., J.P.R.; literature research, S.G.S., K.T., P.R.M.; clinical studies, S.G.S., K.T., E.V., P.R.M., S.S., N.R.; data acquisition and analysis/interpretation, S.G.S., K.T., E.V., P.R.M., S.S., N.R.; manuscript preparation, definition of intellectual content, and editing, S.G.S., K.T., E.V., P.R.M.; manuscript revision/review and final version approval, all authors
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- Sokoloff MH, deKern
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ABSTRACT
INTRODUCTION
