Biomedical Engineering Reference
In-Depth Information
3.
M
APPING
A
NATOMY
Introduction ..........................................................................................23
Volumes of Interest (GTV, CTV, PTV,OAR etc.) ..................................25
Tumor-related terms................................................................................25
Normal tissue-related terms ....................................................................27
Other terms..............................................................................................28
3D and 2D Images................................................................................28
Sectional images .....................................................................................29
Projection images ....................................................................................29
Computed Tomography (CT)................................................................29
The basis of tomographic reconstruction................................................30
The information content of CT ...............................................................32
The interpretation of CT images .............................................................34
Re-slicing of the CT Data .......................................................................37
Four-dimensional CT (4DCT) ................................................................37
Digitally reconstructed radiograph (DRR) .............................................38
Magnetic Resonance Imaging (MRI)....................................................40
Principle of operation..............................................................................40
Comparison of CT and MRI .................................................................43
Spatial accuracy ......................................................................................43
The visualization of bone in MRI ...........................................................44
Clinical information ................................................................................44
Positron-Emission Tomography (PET) ................................................46
Image Registration ...............................................................................48
Rigid body image registration.................................................................48
Deformable image registration ...............................................................50
The use of diagnostic imaging studies ....................................................51
Delineation of Anatomy ........................................................................52
Manual delineation..................................................................................52
Automatic feature extraction...................................................................53
Uncertainty in the delineation of the target volume ...............................54
Delineation of uninvolved normal tissues and organs ............................55
Summary ...............................................................................................56
I
NTRODUCTION
The possibility of treating deep-seated tumors with radiation depends
fundamentally on the ability to “see” - that is, to image - the patient's
internal anatomy and, potentially, functional information about it.
Otherwise, one would not know what to include and what to exclude
from any given radiation beam, or where to aim it. The mapping of
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