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X-Ray Imaging and Computed Tomography
what the topic is for the registration exercise. When monitoring changes, the changes
can be either in intensity or in volume. Changes in intensity can be minimized by
normalization. Volume changes will rely on the location of boundary outlines as
described in Chapter 4 and to some degree in Chapter 3.
Most registration applications rely on correspondence for comparison, such as
the position, shape, and size of the eye, nose, and particular bones. When analyzing
correspondence in image changes over time, such as tumor growth over a period of
several months, the algorithm may require scaling based on anatomical and geometric landmarks.
An entirely different class of registration is recognition of correspondence
between different individuals. On a coarse scale, the images may correspond after
appropriate nonrigid transformations have been made to the images. However, under
higher-resolution observation, they may not give the conclusive evidence needed for
pathological evaluation.
14.11 COMPLICATIONS OF X-RAY IMAGING
Some of the biological effects of x-rays resulting from the high energy interaction with
molecules and atoms in the biological medium, respectively, may cause ejection of one
or more orbital electrons by a photon that creates an ion pair; ions are unstable and give
rise to free radicals. These free radicals are chemically aggressive and may have undesirable consequences since they are mutagenic (cause changes in the DNA structure),
teratogenic (x-ray radiation may be life shortening), and even lethal. The most prominent
complication is the fact that x-ray radiation has carcinogenic consequences.
14.12 SUMMARY
The advantage of radiography is the fact that it is relatively cheap, in addition to the
fact that it reveals ample contrast between bone, soft tissue, and lung. Some of the disadvantages are poor soft tissue contrast in addition to the fact that it has not much use
for distinguishing adjacent healthy and diseased soft tissues. One major disadvantage
is the radiation hazards and epidemiological effects of x-ray radiation.
PROBLEMS
14.1 Read image file “p_14_1.jpg.” This is an x-ray film image of the left and right
breast combined.* The right breast shows asymmetric changes. Compare the
left breast (LMLO) with the right breast (RMLO) and locate the region of
change. Pick a convenient location in the region of asymmetric change and use
seed growing to find the outline of the suspected area.
14.2 Read image file “p_14_2.jpg.” This image shows a fracture of the fibula and
medial malleolus.*
* Courtesy of MedPix. http://rad.usuhs.mil/medpix/
X-Ray Imaging and Computed Tomography
what the topic is for the registration exercise. When monitoring changes, the changes
can be either in intensity or in volume. Changes in intensity can be minimized by
normalization. Volume changes will rely on the location of boundary outlines as
described in Chapter 4 and to some degree in Chapter 3.
Most registration applications rely on correspondence for comparison, such as
the position, shape, and size of the eye, nose, and particular bones. When analyzing
correspondence in image changes over time, such as tumor growth over a period of
several months, the algorithm may require scaling based on anatomical and geometric landmarks.
An entirely different class of registration is recognition of correspondence
between different individuals. On a coarse scale, the images may correspond after
appropriate nonrigid transformations have been made to the images. However, under
higher-resolution observation, they may not give the conclusive evidence needed for
pathological evaluation.
14.11 COMPLICATIONS OF X-RAY IMAGING
Some of the biological effects of x-rays resulting from the high energy interaction with
molecules and atoms in the biological medium, respectively, may cause ejection of one
or more orbital electrons by a photon that creates an ion pair; ions are unstable and give
rise to free radicals. These free radicals are chemically aggressive and may have undesirable consequences since they are mutagenic (cause changes in the DNA structure),
teratogenic (x-ray radiation may be life shortening), and even lethal. The most prominent
complication is the fact that x-ray radiation has carcinogenic consequences.
14.12 SUMMARY
The advantage of radiography is the fact that it is relatively cheap, in addition to the
fact that it reveals ample contrast between bone, soft tissue, and lung. Some of the disadvantages are poor soft tissue contrast in addition to the fact that it has not much use
for distinguishing adjacent healthy and diseased soft tissues. One major disadvantage
is the radiation hazards and epidemiological effects of x-ray radiation.
PROBLEMS
14.1 Read image file “p_14_1.jpg.” This is an x-ray film image of the left and right
breast combined.* The right breast shows asymmetric changes. Compare the
left breast (LMLO) with the right breast (RMLO) and locate the region of
change. Pick a convenient location in the region of asymmetric change and use
seed growing to find the outline of the suspected area.
14.2 Read image file “p_14_2.jpg.” This image shows a fracture of the fibula and
medial malleolus.*
* Courtesy of MedPix. http://rad.usuhs.mil/medpix/