Air as an ultrasound contrast marker for accurate determination of needle placement. Tumor biopsy localization and other applications.

Computed tomography (CT) and ultrasonography can be performed to localize tumors for percutaneous biopsy. With CT, the biopsy needle can be visualized within the sample volume. The needle can not be seen within the tumor on B-scan ultrasound images. The authors have devised an air contrast technique to determine the location of the needle tip and the biopsy site. This technique can also be used for organ biopsies.