UVa Introduces Latest Diagnostic Tool to Aid Early Diagnosis of Cancer and
The University of Virginia Health System now offers patients a revolutionary new diagnostic imaging
technique, PET -CT , to aid
physicians in the diagnosis and treatment of certain cancers and other diseases.
UVa's PET-CT is the only one of it kind in the statee of Virginia. "We are excited to be able to provide this
unique diagnostic service to
residents of Virginia and the region," notes Dr. Patrice Rehm, Director of Nuclear Medicine at UVa.
Who Can Benefit from PET-CT?
PET -CT diagnostic procedures can benefit a range of patients experiencing cancer, as well as other
non-cancerous conditions. Dr. Rehm explained, "PET -CT allows us to find cancers and other diseases earlier
and more effectively than current diagnostic procedures. For example, before PET -CT, a tumor had to grow
large enough to be caught by the available technology, and even then we could not locate it with the same
precision as with this new procedure."
PET -CT allows physicians to detect and pinpoint smaller tumors, lesions or other abnormalities,
earlier in the development of disease. For cancerous conditions, it enables physicians to determine where a
cancerous tumor is located, how far it has spread, and how much surrounding tissue is affected. Previous
techniques were unable to locate with precision small tumors representing the spread of cancer such as those in
lymph nodes, Dr, Rehm explains, "to best treat cancers, the physician needs to know the exact location of the
tumors to determine most effective course of treatment, whether by surgery, chemotherapy, radiation therapy or
By pinpointing tumors or other abnormalities for precise surgical or other therapies, PET -CT can
reduce some of the side-effects of therapy for the patient. For example, through the greater precision in
treatment made possible by PET-CT, cancer
therapy can have lesser impact on surrounding, non-diseased tissue.
During and after treatment for cancerous conditions, PET -CT allows physicians to assess whether the
treatment has been successful in destroying cancer cells. PET -CT enables early detection of the reoccurrence
of cancer, and thus is an effective tool for
ongoing patient monitoring following therapy and remission. PET -CT can reveal tumors" that may be masked
to other imaging techniques by the tissue scarring or other distortions of normal anatomy that often result from
surgery or radiation therapy. In addition to a range of
cancerous conditions, PET-CT can be used to diagnose non-cancerous conditions. Currently, PET-CT is used
to diagnose heart disease as well as brain disorders such as epilepsy, Alzheimer’s disease and Parkinson’s
disease. Dr. Rehm adds, “The same ability to detect and locate, with great precision, malfunctions at the
molecular level will enable PET-CT to be used effectively for a range of diseases.
How Does PET -CT Work?
As its name implies, PET -CT combines the techniques and technologies of PET scans and CT scans in
a single procedure. The combined PET-CT, however, provides a more powerful diagnostic tool for certain
disease applications than either PET or CT alone.
PET, or positron emission tomography, images the distribution through the patient’s body of labeled
glucose (F-18 fluorodeoxyglucose, usually referred to as FDG). Many cancers utilize more glucose than
normal cells, and thus appear as "hot spot" on a standard PET scan. Because of its higher sensitivity, PET
identifies cancer cells at an earlier stage than other imaging modalities. But determining the exact anatomic
location of the "hot spots" can be difficult from PET, because PET essentially provides a "glucose utilization
map" of the body, not an anatomical map.
CT, or computed tomography, essentially provides the anatomic map of the body needed to locate
abnormalities. But it may not reveal
the small, early cancers that can be detected with PET.
To combine the strengths of the two technologies, why not simply compare the results of a separate
PET scan with those of a separate CT scan? After all, a radiologist commonly would look at a patient's prior
CT or MRI scans for an anatomic map when making a diagnosis from a conventional PET scan. But a
comparison of two separate scans does not allow the same degree of precision as that enabled by PET -CT
combined in a single procedure. Much the way that one person's nose is different from another person's nose,
internal organs can differ in shape and size. Those normal differences in anatomy can be amplified by tumor,
by surgery or even by differences in a patient's position during scans. While computer software has been
developed to superimpose a PET scan done one day with a CT scan performed on another day, the software
cannot adjust for unique physical and physiologic states of the patient during the two exams. And the longer the
lapse of time between separate PET and CT scans, the greater the risk that physical or physiologic differences
will reduce the fidelity and precision of any comparison of separate PET and CT procedures.
How Can a Patient Get PET.CT?
Like PET alone, Medicare and private insurance cover the cost of the PET -CT procedure for approved applications. Medicare
coverage includes cancer of the lung, colon, breast, head and neck, esophagus, lymphoma, melanoma, and thyroid. Private insurance may
cover additional types of cancer. The charge for the combined PET -CT is the same as that for PET; there is no additional charge for the
results of the CT scan.
Patient preparation is simple. Typical1y, a patient would need to fast for at least four hours because any sugars ingested would
compete with the radioactive glucose for cellular (and tumor) uptake. High blood glucose can mask a tumor on the PET scan. [Diabetic
patients should check a few days in advance that their blood glucose levels are controlled; specific instructions arc provided when the
appointment is made.] Patients also are advised to avoid strenuous exercise or physical labor for at least 24 hours prior to their appointment.
Significant muscle activity can cause the muscles to take up more of the FDG than usual, and thereby make a tumor harder to identify.
Prior to the scan, a small amount of FDG is given to the patient by an intravenous injection. The patient rest quietly for about 45 minutes to
allow the FDG to be taken up by the cells of the body. The PET-CT scan itself normally takes about 30 minutes. A
report is issued for the PET -CT and is available to the referring physician within 24 hours.
For referring physicians, PET -CT provides a powerful new diagnostic tool that images both anatomic and metabolic activity. For
patients, PET -CT can mean earlier detection, more effective treatment and ultimately improved prognosis.
For more information about PET -CT at UVa, call 434-924-9363.