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 Snow Canyon Clinic is again in the forefront in providing ground breaking diagnostic medical services to residents of Southern Utah, South East Nevada, and Northern Arizona. About three years ago Snow Canyon Clinic was the first to provide PET-CT services to residents of Utah; not only Southern Utah, but the entire State. No comparable technology existed in Utah prior to Snow Canyon Clinic's pioneering efforts.
What is a PET-CT scan? PET-CT represents the most advanced technology in the world in cancer diagnostics. A PET-CT scan detects cancer in all parts of the body earlier and more accurately than any other imaging technology, including CT, MRI, ultrasound, and X-ray. It detects primary and secondary, or metastatic disease better than any other technology. For example, when one considers colorectal cancer the accuracy of PET-CT is at least 97%, while with CT alone the accuracy is only 89%. In the detection of liver metastases (spread to the liver) the accuracy is at least 91%, compared with 89% for CT alone. Most importantly, in the detection of metastases outside of the liver (extrahepatic) the accuracy is at least 92% compared with 82% for CT.
As this is a discussion for the lay person who may have little understanding of statistics, where one must discuss sensitivity and specificity, we will avoid the temptation to "prove" exactly how good PET-CT technology is. However, consider that the overall accuracy of PET-CT in non small cell lung cancer is 88% when compared to 58% with CT alone and 40% with PET alone. It has changed the management of 29% of patients with non small cell lung cancer. It detected unsuspected metastases in more than 20% of such patients when compared with conventional imaging. Recent studies have shown that breast cancer staging in increased from State 2 to Stage 3 in as many as a quarter of patients imaged with PET-CT.
"PET" stands for "positron emission tomography" and CT stands for "computed tomography." PET-CT represents a fusion of the "molecular" or functional information obtained with PET with the anatomical information from CT. The study is a single exam. With PET alone one can see a bright spot where a malignancy might be, but it might remain unknown just how deep that malignancy might be. The combination of PET with CT in a single exam provides precise information not only regarding the functional nature of the abnormality, but it's localization as well. This often permits easy diagnosis by guided biopsy. The functional information provided by PET is particularly important because functional changes occur at the cellular level in cancer (and other diseases; see below) before physical changes occur that would permit detection with CT or MRI alone. This is the single most important element in the advance provided by PET-CT.
What are some of the benefits of a PET-CT scan not elaborated upon above? Perhaps formost, PET-CT reduces or eliminates ineffective or unnecessary surgical or medical treatments. Equally important, though, PET-CT shows the progress of disease and how the body responds to treatement. It helps to determine whether treatment was effective, the degree of effectiveness, and whether further treatments are necessary (whether they be surgical, chemotherapeutic, or radiation therapeutics). PET-CT will show whether a tumor is benign or cancerous. It replaces multiple testing procedures with a single exam. To reinforce what has already been stated, it detects desease before it shows up on other exams; and it shows all organs in a single exam, so it can indicate whether cancer has spread. It is highly effective in the discovery of cancer recurrence, distinguishing between surgical
or radiation scars with great efficacy.
How is the PET-CT scan conducted? A small amount of radioactive sugar (glucose) is injected into your blood stream, and you are provided with a peaceful environment in which to relax while the sugar circulates through your body for approximately one hour. You then lie on a bed that slowly passes through the "open" scanner (there are other PET-CT scanners in Utah now, but none provide the comfort and accuracy of the open "double doughnut" design seen in the picture above). The scan takes about 30 minutes, and you are then ready to go home. The radiologist will have your report within 24 hours, and your physician at the Clinic will be happy to show you the study on computer and provide you with a CD of the study so that you can have this forever for your personal medical records.
Is a PET-CT scan safe? Yes. The risks are minimal and there is no certainty of the presence of "any" risk. The radioactive glucose molecule is metabolized very rapidly in your body and leaves the body very quickly. The glucose isotope is not a contrast agent, so there is no concern regarding contrast reactions (such as with iodine). The radiation exposure associated with a PET/CT scan is similar to that associated with conventional imaging exams, such as CT alone. It probably should not be done in women 35 years and younger, as a routine screening tool; but certainly would be indicated in either gender at any age if there was a concern for cancer whose diagnosis was not forthcoming by other technology.
What Does Medicare Pay For? Medicare approves payment for the diagnosis, staging, and re staging of lung, colorectal, lymphoma, melanoma, head and neck, and esophageal cancer. It has also been approved for restaging and monitoring treatment of breast cancer, thyroid cancer, and cervical cancer. Most private insurers cover these cancers and often others. Furthermore, Medicare now has a registry for all other cancers so that a physician can complete a pre and post imaging test questionaire, and Medicare will thereby approve payment for PET-CT undertaken for any cancer.
Uses for PET-CT other than cancer: Medicare has approved PET-CT for use in Alzheimer's disease diagnosis, where it's application has both high sensitivity and specificity (approaching 90% and 80%, respectively). Payment is also approved for the investigation of an active seizure focus in the brain in one who has refractory epilepsy; thus enabling the surgical resection of a very small portion of the brain safely, and thereby mitigating the problems with seizure control.
The proper role of PET-CT in cardiology is beginning to clarified, and PET-CT is approved for the assessment of myocardial (heart) viability (function) and evidence of scars from previous heart attacks. This is useful information for the interventional cardiologist or surgeon, because fore knowledge that a particular area of the heart is not viable would lead an interventionalist or surgeon away from revascularization of that area. This is a difficult area to discuss because there is still much debate in the professions; but let me print a paraphrase from The Jounarl of Nuclear medicine that might help one understand how the use of PET-CT is advancing in this area: "Multislice CT technology is rapidly approaching the goal of allowing coronary angiography to be performed noninvasively. With the ability to characterize coronary lesion severity at a level of diagnostic accuracy similar to that of invasive coronary angiography, the close correlation of plaque morphology with functional measurements such as myocardial perfusion will be increasingly appreciated (with the inclusion of PET; editor's comment, for clarification). Furthermore, early detection of CAD will be improved by the use of detailed structural and molecular information provided by PET/CT. For example, coronary calcification measurements combined with specific tracer techniques for the characterization of inflammatory processes may help to identify patients who are at high risk for the development of acute ischemic syndromes. Tracer techniques will continue to be of use for the characterization of myocardial tissue viability in patients with advanced CAD and heart failure and may also be applied to monitor new metabolic therapy strategies. The combination of CT morphology and PET perfusion may serve as a surrogate endpoint in new drug evaluations aimed at reversing CAD."
We at Snow Canyon Clinic utilize PET-CT mostly for cancer diagnostics and assessment of response to therapy, but our neurologists utilize the technology for both Alzheimer's diagnosis and refractory seizure disorders. We do not yet use it in cardiology, routinely, but have in the past collaborated with the Texas Heart Institute and now the Cleveland Clinic in developing better protocols and generally advancing this science.
Snow Canyon Clinic has always been on the cutting edge of modern diagnostic technology, and this will continue. Soon there will be a revolution in PET-CT scanning that will markedly improve the ability to assist in the management of the above disease states, and Snow Canyon Clinic will be part of this.
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