CT

High tech medical scans clear way for better local diagnoses

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by Sarah Nicholson, EDN

A newer, safer type of medical imaging has made its way to the Eugene area, and those in the medical field are seeing promising returns.

Oregon Imaging Centers recently received a three-year approval for PET/CT imaging from the most highly-regarded accrediting body, the Intersocietal Commission for the Accreditation of Nuclear Medicine Laboratories (ICANL).

PET/CT imaging and scanner from Oregon Imaging Center

Positron Emission Tomography and Computed Tomography, or PET/CT imaging, is a combination of two scans
that allow medical practitioners to pinpoint the location and extent of cancers, dementias and cardiac illnesses by looking at metabolic and structural changes in the body. 

Oregon Imaging Centers is the only center in Oregon approved for both oncological and neurological diagnoses, and only center approved by ICANL, which is considered the gold standard of nuclear medicine accreditation providers.

In 2007 an article published in the New England Journal of Medicine publicized the overuse of CT scans in the US, and the related cancer risk of exposing organs to low doses of radiation. Since then, media reports fraught with information about the dangers of high radiation levels have caused fear in many people about being overexposed.  The FDA also acknowledges that CT scans are associated with a higher risk of lifetime cancer and says the usage of adult-sized radiation doses in children can be particularly harmful.

The combined PET/CT scan delivers less radiation than a regular CT scan, so the danger of radiation is greatly diminishedAnd in the event that cancer is already suspected, the fear of low-dose radiation pales in comparison to other disease-related complications. Additionally, over 90% of the radioactivity from the PET portion of the scan is gone by the time the patient leaves the exam.  The only populations this diagnostic tool is contraindicated for are pregnant and lactating women, but even in lactating women the radiation is thought to be cleared from the breast milk within twelve hours of the test.

An example of (A) CT imaging, (B) PET imaging, and (C) combined PET/CT imaging. From Wikipedia/Renato M.E. Sabbatini, PhD

 

The PET/CT process uses an injected radioactive substance called fluorodeoxyglucose (or FDG) to highlight abnormal areas within the body. Similar to glucose, which fuels tissues throughout the body, FDG is taken up more eagerly by high-metabolizing abnormalities in the body. So areas that are more metabolically active, like cancerous tumors, draw attention to themselves through their greediness.

Neurological disorders such as Alzheimer’s and Parkinson’s diseases respond similarly in the brain. With an injection of FDG, the compound will accumulate in certain areas, which will then be highlighted on the PET scan images. Add the CT component (Computerized Tomography,) and you have a very specific picture of the disease.

PET(-only) scanners, which Oregon Imaging Centers used before receiving the new accreditation, can differentiate between malignant and benign lesions, and determine the spread of disease. Adding the CT component is incredibly helpful in identifying specific anatomic locations. The dual imaging technique of the PET/CT provides a much more specific picture of disease, especially when it comes to detecting cancer.  

The PET/CT scan is of enormous assistance in both diagnosis of cancer, and in evaluating the effectiveness of therapy.  Luke Breazeal, manager of the PET/CT Department at Oregon Imaging Centers said there are four key times to perform a scan: 

(1) When something malignant is detected or highly suspected
(2) to identify the extent
(3) in the middle of chemotherapy
(4) after completion of chemotherapy 

With just one scan, you can identify cancer, determine its extent in the body, and stage (or esta
blish how far the cancer has progressed.)  For many types of cancer a PET scan can show if a therapy is effective: If a significant decrease in the tumor burden is not seen after a few rounds of chemotherapy, the therapy can be switched, saving valuable time, reducing cost, and increasing life expectancy.

PET image of a brain with Alzheimer's

Although over 90% of PET/CT scans address oncological disorders, it’s an incredibly helpful tool in neurological diagnosis and treatment planning.  In “dementia imaging,” Breazeal said, “we see characteristic metabolic patterns for each specific type of dementia.”   Each of the dozens of different types of dementia displays a unique pattern of glucose (and thus FDG) uptake, and identifying the correct type puts doctors on the right track to choosing a treatment plan. Before PET scans, the only way to definitively diagnose Alzheimer’s was through autopsy.

With the green light from ICANL, Oregon Imaging has seen about a 50% increase in volume for PET/CT imaging.  According to Breazeal, the clinic does about 80-100 scans a month, mostly for oncological purposes.  More information about Oregon Imaging Centers and its new accreditation can be found on its website at www.oregonimaging.com.

Another example of PET/CT fusion imaging of the whole body