In general radiology, the term QCT describes the analysis
of the CT images beyond a visual radiological evaluation.
Typically, the analysis involves the use of dedicated software
to extract quantitative parameters. As such, the term QCT is
not restricted to bone densitometry, in which QCT describes
a technique for measuring BMD in specific regions or
volumes of interest in trabecular or cortical bone. The term
peripheral QCT (pQCT) defines the application of QCT to
appendicular skeleton sites, such as the arms or legs, thus
QCT is more general than pQCT.
From the perspective of bone densitometry, differences in
the acquisition scheme (step and scan vs spiral CT) are of
lesser importance than the image analysis approach: the traditional
2D analysis of regions of interest (ROI) on one or
multiple slices that can also be applied to data from spiral
CT acquisitions, should be distinguished from the 3D analysis
of volumes of interest (VOI) in a contiguous stack of