Emerging technology in head and neck ultrasonography.

Increased use of ultrasonography of the head and neck by clinicians has resulted from more compact, higher resolution ultrasound machines that can be more readily used in the office setting. Palm-sized machines are already used for vascular access and bladder assessment. As the resolution of these machines becomes adequate for head and neck assessment, ultrasonography is likely to become a routine adjunct to the office physical examination. Further techniques to reduce artifact beyond spatial compounding, second harmonics, and broadband inversion techniques are likely to be developed to improve ultrasound images. Manual palpation using the ultrasound transducer or "sound palpation," using sound to recreate vibration provides information on tissue "stiffness," which has been successfully used to distinguish between benign and malignant lesions in the head and neck (particularly thyroid nodules). Microbubble contrast-enhanced ultrasound provides improved resolution of ultrasound images. Three- and four-dimensional ultrasonography provides for more accurate diagnosis. The ability of microbubbles with ligands affixed to their outer surface to target specific tissue makes them excellent delivery vehicles. DNA plasmids, chemotherapy agents, and therapeutic drugs can be released at a specific anatomic site. The motion of microbubbles stimulated by ultrasound can be used to increase drug penetration through tissues and has been shown to be effective in breaking up clots in stroke patients (without increased risk). High-intensity focused ultrasound can be used to create coagulation necrosis without significant damage to adjacent tissue. It has been effectively used in neurosurgery and urology, but its effectiveness in the head and neck is still being determined. A prototype for surgical navigation with ultrasound has been developed for the head and neck, which allows real-time imaging of anatomic surgical changes.