Diagnostic ultrasound ( PDFDrive )

802 PART III Small Parts, Carotid Artery, and Peripheral Vessel Sonography
A
B
FIG. 21.63 Lesions That Appear Spherical on Mammography Often Appear Elliptical on Sonography. (A) Circumscribed isodense mammographic
nodules appeared circular in both views (spherical) because the mammogram demonstrates only the axes of the cyst that lie perpendicular
to the axis of compression and not the compressed axis. Sonography, however, does show the compressed axis. The mean diameter calculated
from mammograms includes three large diameters that all lie in axes perpendicular to the axis of compression. (B) The mean diameter calculated
from the sonographic views includes two large diameters that lie perpendicular to the axis of compression (solid arrow) and one smaller diameter
that lies parallel to the axis of compression (dotted arrow). For compressible lesions, the mean diameter obtained from sonograms is often smaller
than the mean diameter obtained from mammography, but the maximum diameters from mammography and sonography will be similar.
FIG. 21.64 Mammographic-Sonographic Compression and Lesion Orientation. Mammographic compression (left) tends to rotate the long
axis of the lesion perpendicular to the chest wall, whereas sonographic compression (right) tends to rotate the long axis parallel to the chest wall.
The long axes of lesions on mammography and sonography often differ by almost 90 degrees. The double-headed arrows show the long axis of
the lesions.