Positron Emission Tomography
347
the likelihood that any one of them will decay to a lower energy state, thus providing
a higher frequency of detections.
The preceding equations form a topographic problem in which the set of equations
must be solved for the integrand. The details on how these tomographic equations are
solved using methods such as Fourier slice theorem have been provided in the previous
chapters.
17.5 SIGNIFICANCE OF PET
Despite its relatively low resolution, PET imaging has many advantages in
imaging and detection of physiological characteristics that are still being explored
and expanded. The main significance of PET in biomedical diagnostics lies in
the fact that direct metabolic activity can be imaged often on a significantly finer
levels than what can be detected using other technologies such as f MRI described
in Chapter 15.
The applications of PET imaging are significantly more limited than other
scintigraphy-based imaging methods due to the extremely short half-lives of the
radioisotopes used in PET imaging. A more detailed comparison of the PET with
more aggressive nucleotide used in other scintigraphy-based imaging systems will
be discussed in Chapter 18.
The medical significance of the PET modality will become more evident in our
discussion of the applications of the PET imaging given in the following.
17.6 APPLICATIONS OF PET
PET is an invaluable technique for diagnosing specific diseases and disorders,
because it is possible to target the radiochemicals used for particular bodily
functions.
17.6.1 CANCER TUMOR DETECTION
The functional imaging features of PET are most prominent in the diagnosis of
cancer. Healthy tissue replenishes its cells by continuous regeneration, while old
cells gradually die off. Both malignant and benign cancer cells divide more rapidly than normal healthy cells. This process by itself will be identified under PET
imaging due to the increased cellular metabolic rate. In cancer detection using
PET, the tracer FDG is used because it mimics glucose in its metabolic stage and
is avidly taken up and retained by most tumors. As a result, this technique can be
used for the diagnosis and monitoring of the treatment of various cancer tumors.
Due to its specific sensitivity, PET is mostly used to diagnose brain tumors. Other
PET applications in cancer diagnosis are in detection of the breast tumors, lung
tumors, and colorectal tumors.
The difference between malignant and benign tumor growth is the fact that in
malignant cancer cells the surrounding tissue is destroyed as well. The amount of
18 F that accumulates in a tissue over a specific period of time makes it possible to
calculate the rate of glucose uptake in that tissue. An accelerated glucose metabolism
347
the likelihood that any one of them will decay to a lower energy state, thus providing
a higher frequency of detections.
The preceding equations form a topographic problem in which the set of equations
must be solved for the integrand. The details on how these tomographic equations are
solved using methods such as Fourier slice theorem have been provided in the previous
chapters.
17.5 SIGNIFICANCE OF PET
Despite its relatively low resolution, PET imaging has many advantages in
imaging and detection of physiological characteristics that are still being explored
and expanded. The main significance of PET in biomedical diagnostics lies in
the fact that direct metabolic activity can be imaged often on a significantly finer
levels than what can be detected using other technologies such as f MRI described
in Chapter 15.
The applications of PET imaging are significantly more limited than other
scintigraphy-based imaging methods due to the extremely short half-lives of the
radioisotopes used in PET imaging. A more detailed comparison of the PET with
more aggressive nucleotide used in other scintigraphy-based imaging systems will
be discussed in Chapter 18.
The medical significance of the PET modality will become more evident in our
discussion of the applications of the PET imaging given in the following.
17.6 APPLICATIONS OF PET
PET is an invaluable technique for diagnosing specific diseases and disorders,
because it is possible to target the radiochemicals used for particular bodily
functions.
17.6.1 CANCER TUMOR DETECTION
The functional imaging features of PET are most prominent in the diagnosis of
cancer. Healthy tissue replenishes its cells by continuous regeneration, while old
cells gradually die off. Both malignant and benign cancer cells divide more rapidly than normal healthy cells. This process by itself will be identified under PET
imaging due to the increased cellular metabolic rate. In cancer detection using
PET, the tracer FDG is used because it mimics glucose in its metabolic stage and
is avidly taken up and retained by most tumors. As a result, this technique can be
used for the diagnosis and monitoring of the treatment of various cancer tumors.
Due to its specific sensitivity, PET is mostly used to diagnose brain tumors. Other
PET applications in cancer diagnosis are in detection of the breast tumors, lung
tumors, and colorectal tumors.
The difference between malignant and benign tumor growth is the fact that in
malignant cancer cells the surrounding tissue is destroyed as well. The amount of
18 F that accumulates in a tissue over a specific period of time makes it possible to
calculate the rate of glucose uptake in that tissue. An accelerated glucose metabolism