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    Low-Dose Screening CT Chest for Detection of Lung Cancer

    Screening CT Chest shows lung
    carcinoma in the left lower lobe
    which was obscured by the heart on
    the routine chest x-ray performed
    two weeks earlier.
    Why is there a need for lung cancer screening?

    In 1998 there were:

    • 160,000 deaths due to lung cancer in the United States
    • 172,000 new cases of lung cancer
    • 12% cure rate for lung cancer
    By contrast,
    • the 5 year survival rate for lung cancer detected early (Stage IA) was 85-100%
    Routine chest x-ray screening often are unable to detect lung cancers until they are of advanced stage.

    What studies have been done to evaluate this test?

    A study by Henschke, et al. found that non-calcified pulmonary nodules were detected in 23% participants by low dose CT at baseline, compared with 7% by chest radiography. Malignant disease was detected in 2-7% by CT and of the 27 CT-detected cancers, 26 were resectable. It was concluded that low-dose CT can greatly improve the likelihood of detection of small (early) lung cancers, and thus potentially more curable stage.

    Who should consider lung cancer screening?

    People at high risk for developing lung cancer, i.e., those 50 to 80 years of age with at least 10 pack-year history. You have a 10 pack-year history if you have smoked one pack a day for ten years, two packs a day for 5 years, etc.

    How does this test differ from a Diagnostic CT Scan of the Chest?

    Diagnostic Chest CT scans require a prescription by a physician and will only be reimbursed by insurance companies if strict criteria are met. Usually this test is performed if there is an abnormal chest x-ray or history of cancer. Diagnostic CT Scans of the Chest are ordered as a problem solving modality, and usually necessitate intravenous administration of iodinated contrast.

    Low-Dose Screening CT is intended to supplement or replace routine CXRs which are performed in patients without symptoms or known disease. Like screening mammography, it is essential to minimize the amount of radiation exposure in asymptomatic patients. The test is specifically designed to rapidly screen the lungs with minimal radiation exposure, to allow detection of pulmonary nodules. No intravenous contrast is used.

    Low-Dose Screening CT is specifically designed to screen for pulmonary nodules, and is neither designed nor intended to screen for abnormalities elsewhere in the thorax (i.e., heart, aorta, lymph nodes, bones).

    What type of machine is required?

    Since it is critical to minimize radiation and to provide complete lung coverage in a breathhold, this test should only be performed on a helical (spiral) CT scanner with current software and hardware upgrades.

    What does the procedure involve?

    First, you complete a brief risk factor questionnaire. Next, you lie down on the imaging table and a CT technologist will ask you to hold your breath while the images are taken. That's it. In twenty seconds, your exam is complete, and you may return to your regular routine. The procedure is pain free, non-invasive, and inexpensive.

    Your examination will be overread by two board certified radiologists, and results will be sent to you and your doctor within 48 hours.

    What results should I expect?

    If your test was read as negative, then no pulmonary nodules were detected. If you are at high risk for lung cancer, then you should consider repeating the exam yearly.

    If the radiologists detected a pulmonary nodule that raises concern, then you will be urged to make an appointment with a lung specialist. You may be asked to return for a diagnostic CT Chest, which is performed with higher spatial resolution and thin cuts through areas of concern, allowing characterization of nodules detected by the screening exam. Frequently, nodules detected on the screening exam are subsequently revealed to be benign granulomas or scars on the diagnostic study. Therefore, an initially positive screening test does not necessarily mean that you have lung cancer.

    Why should I have this test performed at DMG?

    • At Diagnostic Medical Group, you can be assured of receiving the quality of care that has been a tradition for more than 20 years. DMG and its physicians have a reputation of dedication to offer the community's highest quality diagnostic images and exam interpretation.
    • State-of-the-art multi-slice detector CT scanners, including San Gabriel Valley’s first outpatient 64-slice CT scanner.
    • Exam requires less than 20 seconds.
    • Does not require intravenous contrast injection.
    • Radiation dose is very low, equaling to that of a standard cardiac nuclear test.

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