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Figure 20c.  Suprasternal approach with the triangulation method. (a) Schematic drawing shows the triangulation method (25). Z represents the point on the skin in the same transaxial plane as the target lesion (M). C or the depth of needle insertion is calculated with the Pythagorean theorem (A² + B² = C²). The angle of needle insertion (a) is equal to the angle , which is calculated by means of the tangent B/A. ST = sternum. (b) Axial CT scan shows an anterior mediastinal mass (M) located behind the sternum. (c) Axial CT scan shows the tip of the biopsy needle (arrow) in the mass (M). The needle was inserted through the suprasternal notch and angled downward.