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Hepatic malignancies are one of the most difficult therapeutic challenges in oncology. Cure usually is not possible because of the predilection for intrahepatic recurrence, despite complete resection or ablation of the initial tumor. Nonetheless, durable local control can be achieved through vigilant monitoring and aggressive multimodality therapy coordinated by a multidisciplinary team of specialists in medical, surgical, and interventional oncology. For tumors that tend not to metastasize aggressively beyond the liver, regional control may benefit quality of life and overall survival.

This chapter reviews the basic principles of focused ultrasound therapy. The physical principles are discussed and explained. The technical requirements and instrumentation used are illustrated. The critical value of using magnetic resonance (MR) as an image guidance method for planning, delivering, and monitoring this form of ablation therapy is reviewed, and its application in uterine leiomyomas is highlighted as an example of current clinical practice.

The technology and engineering of tumor ablation are evolving more rapidly than the clinical validation. Technical descriptions risk being obsolete by publication time. General principles and developing technical paradigms provide a simplified framework to practice and study radiofrequency ablation (RFA).This chapter reviews the general limitations of tissue ablation methods, the optimization of ablation in the radiofrequency range, and several emerging technologies and paradigms feasible in the laboratory and possibly translatable to clinical practice.

Radiofrequency ablation (RFA) is most effective for small tumors. In metastases, complete treatment has been reported in 91% of tumors <2cm, 88% of tumors <3cm, and 53% of 3 to 4.5 cm tumors (1,2). In hepatocellular carcinoma (HCC), RFA achieved complete necrosis in 90% of lesions <3cm and 71% of lesions 3.1 to 5.0cm in diameter (3). In our practice, most patients present with larger lesions.

Metastatic liver disease represents one of the most common clinical problems in oncology practice. Multiple treatment options are available including hepatic resection, chemoembolization, intraarterial and systemic chemotherapy, cryotherapy, and radiofrequency ablation (RFA) (,).

Hepatocellular carcinoma (HCC) is the fifth most common cancer in the world, and it represents more than 5% of all cancers (). It usually coexists with underlying chronic liver disease, and according to the stage, one disease will prevail over the other. The stage of HCC at the time of diagnosis is very important to decide the type of treatment—possibly curative when the diagnosis is early, palliative or no treatment when the diagnosis is late.

Neuroendocrine tumors encompass a wide spectrum of neoplasms with a common origin in the neuroendocrine cell system. They share the capacity for hormone secretion that results in distinct clinical syndromes. Although neuroendocrine tumors can arise in organs such as the adenohypophysis, thymus, lung, thyroid, adrenal medulla/paraganglia, and skin (), most familiar are the gastroenteropancreatic neuroendocrine tumors that include carcinoid and islet cell neoplasms. Given the high occurrence of hepatic metastases within this subgroup of neuroendocrine tumors, they are a model for the management of other hormonally active tumors.

The interventional radiologist who establishes a percutaneous tumor ablation program will likely become skilled in liver tumor ablation before attempting to treat renal cell carcinoma. Liver tumors are more common than primary renal tumors, and most patients with liver tumors are not surgical candidates. Thus, a steady influx of patients eligible for percutaneous ablation of hepatic tumors can be expected in many centers. In contrast, surgical removal remains the standard therapy for small renal cell carcinomas, and most patients can undergo resection (). Nevertheless, with the incidence of renal cell carcinoma (RCC) increasing and with the aging population in the United States, the number of patients with small RCCs who are not good surgical candidates is expected to increase (–). Thus, from time to time, the radiologist experienced in percutaneous tumor ablation can expect to encounter patients for whom percutaneous treatment of RCC is the only option or the most reasonable one.

Lung cancer statistics in the United States estimate that 171,900 people in 2003 were diagnosed with lung cancer (1). As the leading cause of cancer death among men and women in the United States, the associated death rate for lung cancer is 28%, surpassing mortality rates of colon, prostate, and breast cancer combined (1). This startling fact underscores the importance of improved methods to treat this aggressive form of cancer. Its ominous prognosis is reflected by the overall 5-year survival rates for previously untreated patients with primary non-small-cell lung cancer (NSCLC) after surgical treatment (according to pathologic stage): 63% to 67% in stage IA, 46% to 57% in IB, 52% to 55% in IIA, 33% to 39% in IIB, and 19% to 23% in IIIA (2,3).

Over the past several years, percutaneous image-guided tumor ablation procedures have proliferated ()–(). Several new technologies, in addition to the previously available percutaneous injection of toxic substances (such as alcohol, hot saline, acetic acid), have been added to the interventional radiologist’s armamentarium. These technologies include radiofrequency ablation (RFA), laser (laser interstitial tumor therapy, LITT), cryotherapy, microwave therapy, and high-intensity focused ultrasound (HIFU) therapy; all except HIFU are percutaneous techniques, and HIFU is trans-cutaneous (). Several centers are now using these techniques clinically, and a large body of experience has accumulated. While most of these ablative techniques have been used predominantly for the treatment of malignant liver tumors, new sites and indications continue to emerge.