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All treatments for glaucoma aim to reduce the intraocular pressure and can have two mechanisms of action: reducing aqueous humor production by the partial destruction or medical inhibition of the ciliary body and facilitating the evacuation of aqueous humor out of the eye. Several physical methods can be used to destroy the ciliary body, diode laser transscleral cyclophotocoagulation being currently the clinical standard. All the currently available methods have two major drawbacks which limit their use to the treatment of refractory and advanced glaucoma: they are nonselective of the organ to be treated, often resulting in damage to the adjacent structures and related side effects (ocular inflammation, cataract formation, etc.), and they have an unpredictable dose-effect relationship, which prevents accurate prediction of the treatment effect. Specific advantages of ultrasound, particularly when compared to laser, are that the energy can be focused through optically opaque media without uncontrolled energy absorption, especially through the sclera which is a strongly light-scattering medium, and that energy deposition and tissue heating at the focus site do not depend on tissue pigmentation, which may vary greatly, particularly in the ciliary body. Focused ultrasound is therefore a possible method for partial coagulation of the ciliary body. A commercially available device using ultrasound to coagulate the ciliary body (Sonocare Therapeutic Ultrasound System Model, Sonocare Inc., Ridgewood, NJ) was marketed in the 1980s and early 1990s. Despite being efficient to reduce IOP, the procedure was rather lengthy and complex to perform, and the use of ultrasound for cyclocoagulation was gradually abandoned in the mid-1990s. Taking advantage of recent breakthroughs in the field of high-intensity focused ultrasound (HIFU) technology, high-frequency miniaturized transducers were recently integrated into a small device with a circular design, adapted to the geometry of the ciliary body. This design allows this new device to be placed directly against the eye, thus enabling a one-step, quick, and reproducible treatment. Animal experiments have shown selective coagulation necrosis of the treated ciliary body. The first clinical trials performed in humans showed that this method is well tolerated and allows a significant, predictable, and sustained reduction in intraocular pressure, both in patients with refractory secondary glaucoma and in patients with primary open-angle glaucoma, whether naive of previous filtering surgery or not.

Lymph node infarction is defined as confluent coagulative necrosis of all or a proportion of the lymph node parenchyma, presumably as a result of ischemia. Lymph node infarction following chemotherapy for malignant neoplasms is excluded from this category. Although most are associated with a preexisting diagnosis of malignancy, lymph node infarcts may precede the diagnosis of malignant lymphoma or other neoplasm. Cases of lymph node infarction have been also reported in association with non-neoplastic conditions such as recent fine needle aspiration biopsy, mediastinoscopy, infectious mononucleosis, disseminated intravascular coagulation, and regional administration of gold for treatment of rheumatoid arthritis.

Percutaneous ethanol injection (PEI) was first proposed about 30 years ago for sclerotherapy of different kind of lesions, such as hepatocellular carcinoma, hepatic and renal cysts, adrenal adenoma, and parathyroid hyperplasia. Ethanol exerts its sclerosing properties through cellular dehydration and protein denaturation, which lead to coagulative necrosis and small vessel thrombosis. As a consequence, hemorrhagic infarcts and reactive fibrosis are the prevailing histological changes described in tissues exposed to ethanol. In the thyroid gland, the first documented use of PEI for treating thyroid cysts dates to 1989 (Period Biol 91:1116–1118, 1989); shortly after, this technique was also suggested as an alternative therapeutic option to surgery and radioiodine for the treatment of autonomous functioning nodules. Since then, PEI sclerotherapy of thyroid cysts has gained a world-wide diffusion, whereas the fortunes of PEI as a candidate first-line therapy for toxic and pre-toxic solid nodules have gradually faded. PEI treatment of thyroid cysts will therefore constitute the heart of the present chapter. PEI has also proved to be quite effective in treating other neck lesions, like thyroglossal duct cysts, enlarged parathyroid glands, and metastatic lymph nodes. These applications of PEI will also be briefly discussed.

Although its use for therapeutic purposes predates diagnostic applications by several decades, ultrasound is most widely known for its imaging capabilities. The passage of ultrasound (US) through tissue can lead to biological changes that may be reversible or irreversible. The biological significance of these effects depends to a large extent on the energy in the ultrasound beam and the goal of the exposure. At diagnostic levels, any changes are largely believed to be biologically insignificant. For therapeutic ultrasound, beneficial cellular or functional effects are deliberately sought, whether these are at the cell membrane level (e.g., transient changes in permeability to facilitate drug delivery) or less subtle effects such as the localised temperatures rises that are required to achieve immediate thermal necrosis in high intensity focused ultrasound (HIFU; this technique is sometimes also referred to as FUS).

Ultrasound represents sound waves above the capacity for human hearing (16 kHz). Generally, the ultrasound used in clinical practice utilizes a spectrum of frequencies between 1 and 20 MHz. When applied diffusely, these waves have broad applicability as a diagnostic imaging modality.

Percutaneous laser therapy is one of the general percutaneous ablation therapy strategies. In principle, laser therapy is possible using fibers or by laser-induced thermotherapy (LITT). The LITT procedure currently is performed at laparotomy, by laparoscopic control intraoperatively, or percutaneously. Monitoring is essential for percutaneous interventions; magnetic resonance imaging (MRI) has proven to be the most reliable thermal measure, while ultrasound has been unable to show an adequate estimation of the thermal changes induced by the applied energy. Laser-induced thermotherapy makes available a photothermal tumor destruction technique that allows solid tumors within parenchymal organs to be destroyed. The laser energy is transmitted via thin optic fibers and causes a well-defined area of coagulative necrosis. This effect results in destruction of tissue by direct heating, while limiting damage to surrounding structures. Magnetic resonance imaging has proven to be an ideal clinical instrument to define the exact position of the optical fibers in the target area, provides real-time monitoring of the thermal effects, and the subsequent evaluation of the extent of coagulative necrosis.

Recent trends in the care of cancer patients emphasize minimizing invasiveness while improving the effectiveness of treatment by utilizing medical resources in a cost-effective manner. This has been evident in the emerging and steadily evolving utilization of interventional radiology over the past quarter century.

The physical and biologic principles of localized high-temperature thermal therapy are well understood. If the targeted tissue volume is heated beyond 57° to 60°C, the threshold for protein denaturation, then coagulation necrosis occurs. This type of thermal treatment results in irreversible cell damage in both normal and neoplastic tissues. Since heat energy deposited above this critical level is not selective, thermal ablation is more comparable to surgery than to the more selective hyperthermia. In the case of cryoablation, the underlying physical and biologic principles are less well understood; nevertheless multiple freezings at a relatively low temperature also result in cell death.

Percutaneous image-guided radiofrequency (RF) tumor ablation continues to gain momentum in adult patients as a viable and effective therapeutic option in the treatment of solid tumors in a variety of locations including the skeleton, liver, spleen, kidney, adrenal gland, and lung (1, 2, 3, 4, 5, 6). In all these areas, the basic concept of RF tumor ablation is similar: localized and contained heat generation systematically induces focal coagulative necrosis and cell death. Cytotoxicity is best induced when regional temperatures reach and maintain 50° to 100°C. In children, RF tumor ablation has been used most widely in the treatment of osteoid osteoma. Percutaneous RF ablation (RFA) has fewer indications in the pediatric population, and hence, has been slower to evolve in the treatment of diseases of the liver, kidney, lung, and soft tissues.

Numerous techniques have been developed for tissue ablation. Techniques to kill tumor cells include heating, freezing, radiation, chemotherapy, occluding the tumor blood supply, injection of caustic agents directly into the tumor, as well as various combinations of these. While most of these were introduced in the late 20th century, at least one dates back to the 19th century. This chapter reviews the general historical perspectives of these different methods, with particular emphasis on radiofrequency ablation.

Although surgical resection remains the “gold standard” for potentially curative therapy for colorectal carcinoma liver metastases, recent improvements in RFA technology have provided patients and physicians with a new treatment option. Advances in RFA device technology, imaging modalities, and minimally invasive tools offer the promise of a more effective and less invasive treatment in the future. The pace with which advances have been made in RFA for liver tumors has added to the excitement in the field. RFA will presumably complement established therapies, including regional and systemic chemotherapy and resection. Results of small, single-institution clinical trials evaluating RFA in this role are promising. Large-scale clinical trials and more long-term outcome data are needed to evaluate the efficacy and role of RFA for the treatment of liver metastases.

The majority of patients with primary or metastatic hepatic tumors are not candidates for resection because of tumor size, location near major intrahepatic blood vessels precluding a margin-negative resection, multifocality, or inadequate hepatic function related to coexistent cirrhosis. Radiofrequency ablation (RFA) is an evolving technology being used to treat patients with unresectable primary and metastatic hepatic cancers. RFA produces coagulative necrosis of tumor through local tissue heating. Liver tumors are treated percutaneously, laparoscopically, or during laparotomy using ultrasonography to identify tumors and to guide placement of the RFA needle electrode. For tumors smaller than 2.0 cm in diameter, one or two deployments of the monopolar multiple array needle electrode is sufficient to produce complete coagulative necrosis of the tumor. However, with increasing size of the tumor, there is a concomitant increase in the number of deployments of the needle electrode and the overall time necessary to produce complete coagulative necrosis of the tumor. In general, RFA is a safe, well-tolerated, effective treatment for unresectable hepatic malignancies less than 6.0 cm in diameter. Effective treatment of larger tumors awaits the development of more powerful, larger array monopolar and bipolar RFA technologies.