Computed tomography (CT) scan and cancer
Computed tomography (CT) scans are advanced imaging tests used to create detailed cross-sectional images of various parts of the body, providing more anatomical detail than traditional X-rays. They play a crucial role in cancer diagnosis and management by helping to locate tumors, assess their size and shape, determine if cancer has spread, and plan treatment strategies. CT scans can also guide biopsies and certain cancer treatments, like radiofrequency ablation.
The procedure typically involves the use of high-energy radiation beams and may require the use of contrast dye to enhance image clarity. While CT scans are generally safe, they are not suitable for everyone, particularly pregnant women or individuals with specific health conditions. Patients may experience minor side effects from contrast dyes, and there is a risk of allergic reactions. Following the scan, a radiologist interprets the images to identify any abnormalities, which could indicate the presence of cancer or other health issues. Overall, CT scans are a valuable tool in modern oncology, aiding in both diagnosis and treatment planning.
On this Page
Subject Terms
Computed tomography (CT) scan and cancer
ALSO KNOWN AS: Computed axial tomography (CAT) scan, abdominal CT, brain CT, chest CT, contrast CT scan, conventional CT, cranial CT, CT-guided biopsy, electron-beam CT scan, full body CT scan, helical CT scan, lumbosacral CT, multislice CT scan, orbit CT, pelvic CT, spiral CT, thoracic CT, 3–D CT, virtual bronchoscopy, virtual colonography, virtual colonoscopy, virtual CT, virtual endoscopy, volumetric CT scan
DEFINITION: A computed tomography (CT) scan is a radiological imaging test used to create cross-sectional slice images of a portion of or the entire body. The slice images are stacked to create three-dimensional images. CT images provide more anatomical detail than X-rays.
Cancers diagnosed: Most
Why performed: CT is a valuable tool for screening for cancer, locating tumors, performing a guided biopsy, identifying cancer that has spread, staging cancer, planning and monitoring cancer treatment, and checking for cancer recurrence. CT can identify blood vessels that support a tumor, as well as the tumor’s shape, size, location, and volume. CT scans are used with procedures to diagnose cancer, such as needle-guided biopsies. They are used in cancer treatments, such as radiofrequency ablation and interstitial therapy.
CT images are archived in computers or printed form. Images are printed on film or with laser imaging. They can be sent and viewed online within a facility and compared for changes over time.
Conventional CT was developed in the early 1970s. CT uses controlled amounts of thin, high-energy radiation beams. Images are taken from a variety of angles. A computer calculates information about the images and produces a slice image of a specific body area. CT can be taken of the entire body or a specific section. Dye enhances images with more detail and contrast. The contrast dye is swallowed, received intravenously, or administered in an enema.
CT has evolved to become faster and to use lower doses of radiation. Spiral or helical CT allows images to be collected quickly. The rapid process helps compensate for movements or breathing that otherwise can blur images. Additionally, spiral CT produces thinner slices of images that show even greater detail. A computer stacks the images to create three-dimensional, rotational pictures of a tumor. Spiral CT is especially useful for imaging liver, lung, and pancreatic cancer.
Recent technology allows doctors to use CT with endoscopy to create virtual endoscopy, virtual bronchoscopy, and virtual colonoscopy or CT colonography. The process uses a computer to create and manipulate three-dimensional images to create a “fly-through” view of an organ, as seen on endoscopy.
CT is used to guide surgeons precisely during procedures. CT is used with needle for tumors, such as for breast cancer biopsies. The CT guidance eliminates the need for invasive exploratory surgery.
CT is used to guide certain radiation treatments. For example, interstitial therapy uses CT guidance to insert radioactive material into a tumor. CT is also used to create a three-dimensional image of a tumor to allow external beam radiation to precisely target the tissue and spare as much healthy tissue as possible.
Patient preparation: CT scans may not be appropriate for some people. Patients should inform their doctor if they have diabetes, kidney disease, or are pregnant. Some facilities conduct a pregnancy test on all women before scanning because radiation can be dangerous to the fetus. Children with movement disorders or claustrophobic patients may receive a mild sedative before the test. In extreme situations, people may be sedated if they can not remain still while the images are taken. Some CT machines may only be used for people who weigh up to three hundred pounds because of the size parameters of the machinery. A small percentage of patients are allergic to contrast dye. Patients should let their doctor know if they are allergic or sensitive to contrast dye, iodine, or shellfish.
CT scans are outpatient procedures performed at a hospital radiology department or freestanding radiology center. Patients receive instructions before their procedure, which vary depending on the chosen procedure. For example, patients may be instructed not to eat or drink for several hours before the CT. Some patients need to use an enema or laxatives. Patients may also need to drink a liquid contrast agent before or upon arriving at the clinic.
Patients wear an examination gown or robe for the procedure. They must remove metal objects that may interfere with the imaging process, such as jewelry, hearing aids, hair clips, glasses, or dentures.
Steps of the procedure: Patients are led into the imaging room. A radiology technologist conducts the CT. Patients lie on a narrow table. The technologist may use positioning devices to help patients maintain specific postures for the test. Head-stabilizing devices may be used for brain scans. Patients may be instructed to change positions throughout the procedure.
During the CT scan, the radiologist technician steps into a room separated by a glass partition. The radiologist constantly contacts the patient via a microphone and intercom system and operates the CT machine.
To take a CT, the table slides into the doughnut-shaped hole of the scanner. Patients must remain motionless while the images are taken. Patients are instructed to take a deep breath and hold it until they are told to exhale. The CT scanner has an X-ray component that emits beams at specific angles. The beams pass through the body and are detected by equipment on the opposite side. The equipment makes buzzing or clicking noises while the scanner is employed.
Patients receiving contrast material may have a CT scan first, receive the contrast material, and then receive a final CT scan. An intravenous (IV) line is inserted into the hand or forearm to deliver the injected contrast material, which may be swallowed. An enema is also used to insert contrast material for gastrointestinal-related CT scans. The contrast material may make patients feel temporarily warm or flushed.
The actual CT scan is short, but preparation and positioning make the procedure last ten to thirty minutes. Spiral CTs are shorter in length. Patients are asked to wait until it is confirmed that the images are clear. They are observed for allergic reactions for a short time following the procedure.
After the procedure: There are usually no aftercare procedures following CT. A friend or relative must drive the patient home if the patient has received sedating medication.
Risks: Patients may experience an allergic reaction to the contrast dye. Symptoms include hives, shortness of breath, nausea, wheezing, itching, or a bitter taste in the mouth. Severe allergic reaction or anaphylactic shock is a rare risk. Radiation from CT is higher than that of standard X-rays. CT is not recommended for pregnant women.
Results: CT images are read by a radiologist and conveyed to the ordering doctor. The doctor may view the images as well. CT images depict anatomical structures in black, white, and shades of gray. Air, soft tissue, hard tissue, fluids, and the contrast agent show details that otherwise cannot be seen. Abnormal results show different characteristics from what is expected, such as tumors, cysts, cancer metastasis, tumor density, tumor composition, enlarged lymph nodes, or atypical fluid accumulations. In some cases, CT can help differentiate between types of tumors.
Bibliography
Applegate, Kimberly. “Pregnancy Screening of Adolescents and Women Before Radiologic Testing: Does Radiology Need a National Guideline?” Journal of American College of Radiology, vol. 4, no. 8, 2007, pp. 533–36.
"Computed Tomography (CT) Scans and Cancer." National Cancer Institute, 8 Feb. 2024, www.cancer.gov/about-cancer/diagnosis-staging/ct-scans-fact-sheet. Accessed 20 July 2024.
"CT Scan." Mayo Clinic, 7 May 2024, www.mayoclinic.org/tests-procedures/ct-scan/about/pac-20393675. Accessed 20 July 2024.
Ishikawa, Susumu., et al. “Mass Screening of Multiple Abdominal Solid Organs Using Mobile Helical Computed Tomography Scanner: A Preliminary Report.” Asian Journal of Surgery, vol. 30, no. 2, 2007, pp. 118–21.
Markman, Maurie. "Computed Tomography (CT) Scan for Cancer." City of Hope Cancer Center, 2 Mar. 2022, www.cancercenter.com/diagnosing-cancer/diagnostic-imaging/ct-scans. Accessed 20 July 2024.
Pearce, Mark S., et al. "Radiation Exposure from CT Scans in Childhood and Subsequent Risk of Leukaemia and Brain Tumours: A Retrospective Cohort Study." Lancet, 4 Aug. 2012, pp. 499–505.
Sone, Shusuke., et al. “Long-Term Follow-up Study of a Population-Based 1996–1998 Mass Screening Programme for Lung Cancer Using Mobile Low-Dose Spiral Computed Tomography.” Lung Cancer, vol. 58, no. 3, 2007, pp. 329–41.
Storrs, Carina. "How Much Do CT Scans Increase the Risk of Cancer?" Scientific American, www.scientificamerican.com/article/how-much-ct-scans-increase-risk-cancer. Accessed 20 July 2024.