Low-Dose CT Scan vs. X-ray

Low-Dose CT Scan vs. X-ray

Is there a difference between a Low-Dose CT Scan and a traditional X-ray when screening for lung cancer?

The type of low-dose CT scan that is recommended for lung cancer screening is a newer form of CT scan known as a low-dose spiral or helical CT scan. The low-dose spiral CT scan continuously rotates in a spiral motion and takes several 3-dimensional X-rays of the lungs. These X-rays are very detailed and can show early-stage lung cancers that may be too small to be detected by a traditional X-ray. Traditional X-rays can identify lung cancers the size of a dime, whereas low-dose spiral CT scans can reveal lung abnormalities the size of a grain of rice. This is a crucial difference-- the smaller the tumor is when it is detected; the less likely the cancer cells have spread to other parts of the body. This means more treatment options and a higher chance of survival.

One other difference between the low-dose spiral CT scan and traditional X-rays is that spiral CT scans take much less time than a traditional X-ray. A low-dose CT scan takes less than a minute [5]!

What should I expect during a Low-Dose CT Scan?

A low-dose CT scan is a quick, painless, and non-invasive approach to screen for lung cancer [6]. This type of CT scan uses no dyes, no injections, and requires nothing to swallow by mouth. The actual scan itself takes less than a minute to complete and from start-to-finish, the entire appointment takes approximately 30-minutes.

Prior to getting a low-dose CT scan, you will change into an exam gown. Then you will be asked to lie on your back on the table of the CT machine with arms raised above the head. The table will then slowly pass through the center of a large CT machine while detailed X-ray images are taken of the lungs. It is important to stay very still during the scan to prevent any possible blurring of the images; at times, patients may be asked to hold their breath to decrease chance of blurring. While in the CT machine, you may hear a whirling sound as the scan rotates in a spiral rotation around the area of the body being scanned.

Though the scanner will cover your entire body for a short period of time, both ends of the machine are completely open for you to see and hear outside of the machine. The physician or technician performing the scan is able to see and hear the you at all times [5, 6].

Are there any associated risks involved in CT screenings?

Many diagnostic tests and treatment therapies use radiation. For many diseases, these tests and therapies have reduced the need for surgery and dramatically increased life expectancy. The Swedish Cancer Institute (SCI) is aware of radiation exposure risks and aims to reduce your exposure by using the lowest possible dose of radiation with the latest technology in low-dose CT scanners.

Compared to a conventional CT, the low-dose CT scan for lung cancer uses approximately 5 times less radiation. Depending on the size of the patient, a low-dose CT scan will typically deliver 1-4 millisieverts of radiation exposure. A conventional CT scan typically delivers between 5-20 millisieverts [4, 5]. Radiation exposure is always something to consider when going in for a procedure like a low-dose CT scan. Though the radiation exposure from a low-dose CT scan is higher than a typical X-ray, the benefits of receiving such a screening dramatically outweigh the risks of not having the screening, especially if lung cancer is detected. The amount of radiation patients are exposed to during a low-dose CT scan is approximately equivalent to each of the following [4, 5]:

  • Receiving 15 traditional X-rays
  • Taking 50 cross-country flights
  • 6 months of natural background radiation

What happens if the scan finds something?

Results from a low-dose CT scan normally take about a week. It should be noted that abnormalities are common and that most are noncancerous and harmless. After the CT scan is completed, a follow-up appointment will be scheduled with a member of the Lung Cancer Screening Program team to discuss the results of the scan in person. If the CT scan reveals something abnormal, you and a member of the Lung Cancer Screening Program team will discuss next steps in the process, including further diagnostic tests and/or repeat imaging. The good news is that when lung cancer is found at an early stage, success rates for treating the disease are much higher.


[4]. Memorial Sloan-Kettering Cancer Center. Screening Guidelines: Lung Cancer. [July 20, 2012]; Available from: http://www.mskcc.org/cancer-care/screening-guidelines/screening-guidelines-lung.

[5]. National Cancer Institute at the National Institutes of Health. Computed Tomography (CT): Questions and Answers. [July 20, 2012]; Available from: http:://www.cancer.gov/cancertopics/factsheet/detection/CT.

[6]. Cedars-Sinai. CT Lung Screening. [July 20, 2012]; Available from: http://www.cedars-sinai.edu/Patients/Programs-and-Services/Imaging-Center/For-Patients/Exams-by-Procedure/CT-Scans/CT-Lung-Screening.aspx.

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