MR Imaging–guided Focused Ultrasound for Treatment of Bone Metastasis

Abstract

Magnetic resonance (MR) imaging-guided focused ultrasound is an alternative noninvasive method for reducing the pain in skeletal metastases. MR imaging-guided focused ultrasound ablation offers several key advantages over other noninvasive treatment modalities. This technology enables the performance of three-dimensional treatment planning with MR imaging and continuous temperature mapping of treated tissue by using MR thermometry, thereby enabling real-time monitoring of thermal damage in the target zone. The concentration of acoustic energy on the intact surface of cortical bone produces a rapid temperature increase that mediates critical thermal damage to the adjacent periosteum, the most innervated component of mature bone tissue. Such thermal ablation has been shown to be an extremely effective approach for pain management. Energy delivered during MR imaging-guided focused ultrasound ablation and accumulated inside the pathologic soft tissue of the metastases can create a variable amount of tissue necrosis. This technique has also a potential role in achieving local tumor control, allowing remineralization of trabecular bone or reduction in lesion size. The current report presents a detailed step-by-step guide for performing MR imaging-guided focused ultrasound ablation of bone metastases, including use of MR thermometry for monitoring treatment, protocol selection for simple palliation of pain or for local tumor control, and a description of imaging features of periosteal neurolysis or metastasis ablation. Two case studies are also presented: in the first, the technique provided palliation of pain in bone metastases, and in the second, the technique achieved tumor control as further proof of primary efficacy. MR imaging-guided focused ultrasound ablation is a promising method for successful palliation of bone metastasis pain and tumor control, because of the bony structure remodeling induced by thermo-related coagulative necrosis.

Focused ultrasound for treatment of bone tumours

“…Details on treatment planning of image-guided FUS are outside the scope of this review, and can be found elsewhere for MRgFUS [16] and USgFUS [33].…”

“…Attenuation of ultrasound energy as it propagates through biologic tissue results in a rise of temperature in the treated volume. Coagulative necrosis and cell death occur within seconds at temperatures in the range of 65-85°C [16], so that the ablative treatment must be well localized to the tumor target and avoid surrounding normal tissues. To achieve the required focusing and rapid elevation of tissue temperature at depth, the ultrasound energy is usually intensified at a focal spot by using multiple intersecting ultrasound beams that converge on the target.…”

“…This reduces the potentially detrimental thermal smearing and energy dissipation effects to surrounding tissue due to blood perfusion. Because of these technical issues, ablation of a typical tumor requires sequential tiling of multiple sonications to create homogeneous thermal damage and coagulative necrosis of the entire target volume [16,17].…”

MRI-guided focused ultrasound surgery in musculoskeletal diseases: the hot topics

“…75 MRgFUS has been first proposed with a potential in pain palliation of bone metastases, for its good results in patients non-responding to radiotherapy while applying acoustic energy on the bone surface resulting in bone cortex heating, and indirectly ablating the adjacent periosteum-the most innervated component of mature bone tissue, and tumour tissue, and a major source of pain. 11,76 The bone is a common site for metastasis. The primary cancers that most frequently metastasize to bone are breast and prostate cancers (post-mortem incidence of bone metastases: breast 73%, prostate 68%, thyroid 42%, lung 36%, renal 35%), and these are among the most incident and curable worldwide.…”

Treatment of focal benign lesions of the bone: MRgFUS and RFA

“…[1][2][3][4][5][6][7][8][9][10][11] Conversely, benign diseases are still under investigation and, so far, the treatment of only osteoid osteoma has appeared in literature. [12][13][14][15] There is scarce literature describing the characteristics and the treatment of benign lesions other than osteoid osteoma, 16 and the studies are usually restricted to a low number of patients.…”