128-Slice CT Scanner Technology at St. John’s

Clearest Imaging Possible and Enhanced Diagnostic Accuracy

St. John’s is proud to announce that St. John’s Regional Medical Center in Oxnard is now home to a new SOMATOM Definition AS+ 128-slice computed tomography (CT) scanner by Siemens.

The scanner is one of the newest adaptive scanners, which means that it can adapt quickly to the specific needs of each patient and it can be used in a variety of clinical settings, including non-invasive imaging of the coronary arteries, perfusion, cardiovascular care, urgent care, and much more. This advanced scanner also features extreme safety measures, including the ability to block clinically irrelevant radiation exposure, ensuring that the only dose applied to the patient is the dose that is clinically relevant, with no compromise in image quality.

It produces the clearest images possible, allowing our experts to diagnose with greater accuracy. For our patients, this means that, in many cases, early detection and prevention will play an even more significant role in their treatment and future care.

For more information about St. John’s Diagnostic Imaging Services, call (805) 988-2872.

Coronary Computed Tomography Angiogram (CTA)

What Is It For? A coronary CTA is a heart-imaging test currently undergoing rapid development and evaluation for non-invasively determining whether either fatty deposits or calcium deposits have built up in the coronary arteries, which supply blood to the heart muscle. If left untreated, these areas of build-up, called plaque, can cause heart muscle disease. Heart muscle disease, in turn, can lead to fatigue, shortness of breath, chest pain and/or heart attack.

How Does It Work? A coronary CTA comes from a special type of X-ray examination. Patients undergoing a coronary CTA scan receive an iodine-containing contrast media as an IV solution to ensure the best images possible. The same IV in the arm may be used to give a medication to slow or stabilize the patient’s heart rate for better imaging results. During the examination, X-rays pass through the body and are picked up by special detectors in the scanner. Typically, higher numbers (especially 16 or more) of these detectors result in clearer final images. For that reason, coronary CTA is often referred to as “multi-detector” or “multi-slice” CT scanning.

St. John’s Regional Medical Center’s new CT scanner has 128 detectors. The information collected during the coronary CTA examination is used to identify the coronary arteries and, if present, plaque in their walls with the creation of 3-D images on a computer screen. St. John’s Regional Medical Center uses state-of-the-art TeraRecon Intuition software to produce life-like 3-D pictures of the heart and coronary arteries.

How is Coronary CTA Different from Other Heart Tests? One of the most common heart tests is the coronary angiogram or cardiac catheterization. This test is more invasive and requires more patient recovery time than coronary CTA. Patients who receive coronary angiograms must have a catheter, or small transport tube, threaded into their coronary arteries, which run along the outside of the heart. The catheter typically is inserted into a blood vessel in the upper thigh and then maneuvered up to the coronary arteries. The catheter then is used to inject the iodine dye needed for the test, which uses X-rays to record “movies” of the interior of the coronary arteries.

Although coronary CTA examinations are growing in use, coronary angiograms remain the “gold standard” for detecting coronary artery stenosis, which is a significant narrowing of an artery that could require catheter-based intervention (such as stenting) or surgery (such as bypassing). On the other hand, this new technology has consistently shown the ability to rule out significant narrowing of the major coronary arteries and can, non-invasively, detect “soft plaque,” or fatty matter, in their walls that has not yet hardened but that may lead to future problems without lifestyle changes or medical treatment.

Coronary Computed Tomography Angiogram (CTA)

Who Should Consider Coronary CTA? The single most important step for patients trying to determine whether they should consider a coronary CTA is consultation with their primary physician. This is because some coronary CTA uses are more appropriate than others, and the scan carries some risk from X-ray exposure (potential for stimulating cancer) and contrast dye exposure (allergic reactions and kidney damage). St. John’s applies careful patient selection and risk-reduction efforts to successfully perform this procedure.

Overall, coronary CTA examinations have tended to help determine a lack of significant narrowing and calcium deposits in the coronary arteries, as well as a presence of fatty deposits. This has been found to be particularly valuable in asymptomatic patients with higher risk for coronary disease, in patients with atypical symptoms but lower risk of coronary disease, or in patients with unclear stress-test results. Therefore, St. John’s currently supports the careful use of coronary CTA for patients who have:

• Intermediate to high-risk profiles for coronary artery disease, but who have atypical symptoms (such as shortness of breath, or fatigue during heavy physical activity.)
• Unusual symptoms for coronary artery disease (such as chest pain unrelated to physical exertion), but intermediate to high risk profiles for coronary artery disease.
• Unclear or inconclusive stress-test (treadmill test) results.

For these types of patients, coronary CTA can provide important insights to their primary physician into the extent and nature of plaque formation with or without any narrowing of the coronary arteries.

Coronary CTA can also, non-invasively, exclude narrowing of the arteries as the cause of chest discomfort and detect other possible causes of symptoms. But again, initial consultation with a primary physician is important for patients seeking to determine the appropriateness of coronary CTA.

Who Should Not Have Coronary CTA? To date, coronary CTA has not been proven as effective as the coronary angiogram in detecting disease in the smaller heart arteries that branch off the major coronary arteries. For that reason, St. John’s physicians do not consider coronary CTA as an adequate substitute for needed coronary angiography in patients with strong evidence of narrowing of the coronary arteries. Such patients include those with a history of chest pain during heavy physical activity, a history of positive stress-test results, or a known history of coronary artery disease or heart attack. Coronary CTA also is of limited use in patients with extensive areas of old calcified or hardened plaque, which is often the case in older patients. Patients who are extremely overweight or who have abnormal heart rhythms also tend not to be suitable candidates for this test because imaging quality is compromised.

What Type of Coronary CTA is used at St. John’s? St. John’s uses the new state-of-the-art SOMATOM Definition AS+ 128-slice CT scanner by Siemens. Contact your primary care physician or cardiologist for more information about coronary CTA.

To find a physician / cardiologist on staff at St. John’s, click here.