Biomedical Engineering Reference
In-Depth Information
Table 1.2:
Comparison between approximate times for single and composite
volume registration
Composite
Single-Stage
Surface Matching
No. of
Volume
Total time
MI-GA
Case
slices
Features Extraction
Matching
Matching
(sec)
(sec)
CT/CT
236
20 sec
30 sec
100 sec
150
300
CT/MR
33/19
8 sec
20 sec
80 sec
108
250
in a variety of clinically observable deficiencies, such as speech difficulties, pain,
impairment of senses, loss of muscle control, and cognitive abnormalities [36].
In the brain, MS results in the inflammation and destruction of myelin, a fatty
covering insulating nerve cells [36]. This damage results in decreased ability
of the nervous system to control the body, leading to the clinically-observable
symptoms of the disease. The causes of MS are not clearly accepted in the med-
ical community. Geographic, genetic, and environmental factors all seem to be
present [35]. Many researchers have proposed that MS is an autoimmune dis-
ease [35]. Though there are promising research developments, at this time, no
cure is known for this disease. Several treatment options are available, and allow
for management of the disease. Despite this, most patients progress in disability
over the course of their life [35]. Though not usually a fatal disease in and of
itself, the resulting disabilities may contribute to accidental mishaps [35].
When patients with MS are imaged using MRI modalities, lesions (also re-
ferred to as plaques or deficits) can be contrasted against surrounding, normal
brain tissue, by choice of appropriate scan parameters, and depending on the
state of the lesion [37]. Figure 1.14 shows several slices of different FLAIR MR
images of patients with MS. MS lesions appear as hyper intense regions in the
patient's brain.
The use of MR imagery in the evaluation of MS involves the identification of
abnormal brain tissue (MS lesions), and normal, non-diseased brain tissue (gray
and white matter). MRI has been found to be a sensitive marker to changes
in disease progression, and evaluation of MRI studies of MS patients can be
useful as an outcome measurement in MS studies [4]. Despite these statements,
evaluation of the disease cannot be completely based upon MRI findings. MS
lesion activity observed in MRI studies of the brain does not always correspond
