Motion Correction in Emission Tomography - Correction Techniques in Emission Tomography - page 159

TABLE 8.1: Maximum respiratory motion of different organs.

Organ Motion [mm] Reference

Diaphragm 38.0 Vedam et al. [64]

Heart 23.5 McLeish et al. [47]

Liver 25.0 Brandner et al. [6]

Spleen 25.0 Brandner et al.[6]

outer surface of the thorax, the kidneys, etc., are also moved. This respira-
tory motion is a 3D motion with major components in the cranio-caudal and
the anterior-posterior directions and leads to image blur (see Figure 8.1). The
respiratory pattern of each patient is unique as can be seen in Figure 8.2.
The maximum motion of different organs due to respiration as measured in
clinical studies is given in Table 8.1. It is obvious from the table that the extent
of the motion exceeds or is comparable to the dimensions of small objects of
interest. This means that in absence of motion correction, the activity from
such organs or tumors might be spread over a relatively large volume and
distort the quantification and analysis of the data.

8.1.1.3 Cardiac motion

The heart performs a complex motion during its contraction phase: it not
only contracts in length but also twists during the contraction. A major change
in the size and shape of the heart results. The blood volume inside the heart
is thereby reduced and the thickness of the heart muscle, the myocardium,

FIGURE 8.1: The respiratory motion causes blurring of PET data. Left:
coronal, right: saggital slices of a cardiac study. The effect of image blur is
evident from the images. Top row shows all PET data, bottom row shows only
one phase from the data.