Biomedical Engineering Reference
In-Depth Information
(computed tomography), MRI (magnetic resonance imaging), US (ultrasound),
portal images, and (video) sequences obtained by various catheter scopes, e.g.,
by laparoscopy or laryngoscopy. Other prominent derivative techniques include,
MRA (magnetic resonance angiography), DSA (digital subtraction angiography,
derived from X-ray), CTA (computed tomography angiography), and Doppler
(derived from US, referring to the Doppler effect measured). Functional modal-
ities include (planar) scintigraphy, SPECT (single photon emission computed
tomography), PET (positron emission tomography), which together make up
the nuclear medicine imaging modalities, and fMRI (functional MRI).
An eminent example of the use of registering different modalities can be
found in the area of epilepsy surgery [1]. Patients may undergo various MR, CT,
and DSA studies for anatomical reference; ictal and interictal SPECT studies;
MEG and extra and/or intra-cranial (subdural or depth) EEG, as well as PET
studies. Registration of the images from practically any combination will benefit
the surgeon. A second example concerns radiotherapy treatment, where both
CT and MR can be employed. The former is needed to accurately compute the
radiation dose, while the latter is usually better suited for delineation of tumor
tissue.
Yet, a more prominent example is the use of medical registration for the
same modality, i.e., monomodale registration. For example, in the qualitative
evaluation of multiple sclerosis (MS) studies, where multiple MRI scans of the
same patient at different times must be compared with one another. Due to
the largely arbitrary positioning of the anatomy in the scanner, in a slice-by-
slice comparison between studies, quite different anatomy can by chance be
located on the same slice numbers in different studies. The goal of registration,
therefore, is to align the anatomy from one scan, to the anatomy from another.
Medical registration spans numerous applications and there exists a large
score of different techniques reported in the literature. In what follows is an
attempt to classify these different techniques and categorize them based on
some criteria.
1.2
Medical Registration Classifications
The classification of registration methods used in this chapter is based on the
criteria formulated by van den Elsen , Pol and Viergever [2]. Maintz and Viergever
