| dc.description.abstract |
<p>Computed tomography (CT) is a valuable technology to the healthcare enterprise
as evidenced by the more than 70 million CT exams performed every year. As a result,
CT has become the largest contributor to population doses amongst all medical imaging
modalities that utilize man-made ionizing radiation. Acknowledging the fact that ionizing
radiation poses a health risk, there exists the need to strike a balance between diagnostic
benefit and radiation dose. Thus, to ensure that CT scanners are optimally used in
the clinic, an understanding and characterization of image quality and radiation dose
are essential.</p><p>The state-of-the-art in both image quality characterization and
radiation dose estimation in CT are dependent on phantom based measurements reflective
of systems and protocols. For image quality characterization, measurements are performed
on inserts imbedded in static phantoms and the results are ascribed to clinical CT
images. However, the key objective for image quality assessment should be its quantification
in clinical images; that is the only characterization of image quality that clinically
matters as it is most directly related to the actual quality of clinical images. Moreover,
for dose estimation, phantom based dose metrics, such as CT dose index (CTDI) and
size specific dose estimates (SSDE), are measured by the scanner and referenced as
an indicator for radiation exposure. However, CTDI and SSDE are surrogates for dose,
rather than dose per-se.</p><p>Currently there are several software packages that
track the CTDI and SSDE associated with individual CT examinations. This is primarily
the result of two causes. The first is due to bureaucracies and governments pressuring
clinics and hospitals to monitor the radiation exposure to individuals in our society.
The second is due to the personal concerns of patients who are curious about the health
risks associated with the ionizing radiation exposure they receive as a result of
their diagnostic procedures.</p><p>An idea that resonates with clinical imaging physicists
is that patients come to the clinic to acquire quality images so they can receive
a proper diagnosis, not to be exposed to ionizing radiation. Thus, while it is important
to monitor the dose to patients undergoing CT examinations, it is equally, if not
more important to monitor the image quality of the clinical images generated by the
CT scanners throughout the hospital.</p><p>The purposes of the work presented in this
thesis are threefold: (1) to develop and validate a fully automated technique to measure
spatial resolution in clinical CT images, (2) to develop and validate a fully automated
technique to measure image contrast in clinical CT images, and (3) to develop a fully
automated technique to estimate radiation dose (not surrogates for dose) from a variety
of clinical CT protocols.</p>
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