Oncologic imaging includes the diagnostic tools doctors use at each step of a patient's cancer care. Where imaging technology such as magnetic resonance imaging (MRIs) or chest X-rays once played narrowly defined roles, particularly in diagnosing and staging, these same tools can now help decide which treatment plan may work best, guide the actual treatments, and determine if a change is necessary. Doctors also rely more heavily on imaging to monitor patients once treatment is complete.
How and when is imaging used?1
- Screening: There are many reasons why a patient's doctor may request oncologic imaging, such as obvious physical symptoms, family history, age, and lifestyle (e.g., smoking, diet, alcohol or drug consumption, exposure to carcinogens through work). Imaging can help doctors locate and identify abnormalities that might indicate pre-cancer or cancer. For example, a mammogram machine is a common imaging tool used to examine breast tissue for abnormalities.2 Another commonly used imaging tool is a low-dose computed tomography (CT) scan, which can help detect lung cancer early, when it is most treatable.3 Oncologists in the United States adhere to comprehensive standards and practices to support clinical decision-making with imaging. These guidelines, called the Appropriate Use Criteria, are defined by the National Comprehensive Cancer Network.15 In the U.K., similar guidelines for the use of oncologic imaging are maintained by the Royal College of Radiologists.16
- Staging: Imaging is an important part of modern cancer care. Doctors can use imaging tools to determine how serious, or how advanced, a case of cancer is. This includes locating cancerous tissues in or on the patient's body, whether it has metastasized (i.e., spread), and how much or how little the cancer has grown. All of this information, which imaging helps provide, collectively allows doctors to stage a patient's cancer. Imaging can even be used to improve the quality of a biopsy, allowing for a more targeted, accurate sample, often from directly within a tumor or lesion.4 The most common types of imaging used for staging are CT, MRI and combined positron emission tomography (PET)/CT scans.
- Guiding treatment: Imaging is now an essential part of the treatment process. It helps target treatments more effectively, and can increase a patient's quality of life during the process by allowing for more precise, less-invasive treatment procedures. For example, imaging can target radiation therapy much more specifically, allowing for less radiation and a shorter recovery period in many cases. Imaging procedures such as ultrasound, MRI, or CT scans can help determine exact tumor locations, allowing treatments to be focused, and minimizing the negative impact on nearby healthy tissues.
- Interventional imaging: This form of radiology uses minimally-invasive, image-guided procedures that can help diagnose and treat diseases in nearly every organ system. The concept behind interventional radiology is to diagnose and treat patients using the least invasive techniques currently available in order to minimize risk to the patient and improve health outcomes. These procedures have less risk, less pain and less recovery time than open surgery.14 Image-guided x-rays, for example, are the most common form of interventional imaging for patients with liver cancer.
- Changing a course of treatment: Imaging can provide insights during treatment that can alter how a doctor treats his or her patient. For example, is the tumor shrinking or growing as a result of the treatment plan? Has the cancer ceased to spread, or is continuing to affect new areas? Is a tumor transitioning from malignant to benign? All of these critical questions can be answered and responded to with the help of imaging technologies like MRIs, and CT and PET scans.
- Monitoring: Imaging is also used after treatment to help doctors determine if it was successful, or if the cancer has returned or metastasized. For example, patients who undergo treatment for breast cancer should continue routine annual mammograms to ensure no cancerous tissues return.5 The use of oncologic imaging is essential to maintaining a clear, accurate picture of how a patient has responded to treatment, whether cancerous tissue has returned, or whether a new cancer has started to develop.
What are the main types of oncologic imaging tools?
- CT scans show images of the targeted area in slices. Each slice shows part of the patient's body, such as bones, organs, and soft tissues, with more clarity than standard X-rays. CT scans provide non-invasive, detailed, multi-layered images that can help doctors see a tumor’s shape, size, and location, as well as the blood vessels that feed the tumor. A CT scans can pair with biopsies and surgical procedures to more precisely target affected tissues and minimize patient safety and recovery time. Guided biopsy aids during surgical procedures in removing cancerous tissue. Comparing CT scans throughout treatment and recovery can help doctors see how a tumor is responding, as well as determine if the cancer has come back or spread.6 CT scans and PET scans (see below) are the most commonly prescribed form of oncologic imaging.
- MRI uses magnets, not radiation, to create cross-sectional images in slices, or "views." These views cover many angles, and allow doctors to examine tissues that may be difficult to see in other imaging tests. MRI is a critical diagnostic and staging tool that can be paired with a contrast dye for even greater levels of detail. It also helps doctors determine whether tissue abnormalities are in fact cancer, and even whether the cancer has begun to metastasize. MR images are an important component in determining which course of treatment may be most effective.7
- Vascular and interventional radiology (VIR) is a sub-specialty of general interventional imaging standards and practices. It is paired with imaging tools, such as ultrasound and CT scans, to deliver minimally invasive treatment directly to the affected area. VIR enables doctors to perform a number of critical oncologic procedures, including image-guided biopsies. For patients with cases of liver cancer, VIR can be used to deliver treatments such as chemotherapy or radioactive particles directly into the tumor via catheters.14
- X-rays create images of bones and certain organs and other tissues. More sophisticated imaging such as MRI and CT scans provide a higher level of detail and clarity, but X-rays are a quick, easy, and cost-effective way for doctors to take an initial look at areas of potential concern.8
- Mammograms are a form of X-ray imaging that specifically target breast tissue. Mammogram machines use plates to compress and flatten the patient's breast, which helps create a clearer picture using less radiation than standard X-ray imaging.9
- Nuclear medicine scans (e.g., PET scans) help locate cancerous tissues and determine whether those tissues have metastasized. PET scans and related imaging tests are usually painless and can be performed as an outpatient procedure.10
- Ultrasounds creates images, or "sonograms," by sending sound waves into the body, where they bounce off the targeted area. As the sound waves bounce and reflect, they create "echoes." The ultrasound machine compiles these echoes into a coherent image doctors can use to called sonograms by giving off high-frequency sound waves that go through your body. As the sound waves bounce off organs and tissues, they create echoes in real time. These echoes show organs, tissues, and blood vessels. Ultrasound can image areas that an X-ray can't, and is especially useful for differentiating solid tumors from fluid filled cysts. Like X-rays, the procedure can be done quickly and non-invasively, but is not as detailed as other imaging tests, such as CT scans or MRI.11
How can patients prep for each type of imaging procedure?
- CT scans are usually done as an outpatient procedure, which means no overnight stay at a hospital. Doctors ordering CT scans may request the use of a contrast dye, which can cause an adverse reaction. To counteract a reaction, patients may be prescribed a steroid prior to the procedure. Patients who have had reactions to contrast dye in the past may be given a steroid and a test dose to help prevent another reaction. Some patients may be instructed to refrain from eating or drinking for up to one full day before the CT scan. If the procedure involves the intestines, patients may need to undergo an enema first to clean out the area and ensure a quality image.6
- MRI scans are generally performed as outpatient procedures. No fasting is required before the procedure. Often, a contrast dye, called gadolinium, is used to help improve the contrast and overall quality of the imaging. Patients who are claustrophobic or wary of enclosed spaces should tell their doctor. The doctor will prescribe an anti-anxiety medication that may also have a sedative effect. The MRI machine encloses the patient's body, but there is a two-way speaker to ensure the test can be paused or stopped if the patient is experiencing claustrophobic symptoms. It's critical that patients disclose any prostheses, body art, or implants, such as surgical clips, staples, screws, plates, stents, artificial joints, metal fragments (shrapnel), tattoos, permanent makeup, artificial heart valves, implanted infusion ports, or implanted nerve stimulators. The patient's doctor and the imaging technologist can consult to determine how best to work around such impediments.7
- X-ray imaging doesn't require much in the way of special preparation. Patients who wear metal jewelry should disclose that to the imaging technologist and remove it safely before the procedure. Patients may be asked to fast before the X-ray is taken, but that information will be detailed in the instructions the imaging center provides. A contrast dye may be used, so patients who have had adverse reactions to iodine or other contrast dyes should discuss those experiences with the imaging technologist.8
- Mammograms are a common breast cancer screening tool and they do cause some physical discomfort during the procedure. Patients must take care to work with the imaging center to find a time when breast tissues are least likely to be tender. Pre-menopausal patients often find that breast tenderness tends to lessen the week after their menstrual period. Patients will want to make sure all previous mammogram images are available to their doctor for comparison. A common mistake for first-time patients is to wear deodorant the day of the mammogram. Using deodorants, antiperspirants, powders, lotions, creams, or perfumes under the arms or on the breasts can alter the quality of the image and cause confusion for the radiologist examining it. For discomfort, patients may opt to take over-the-counter pain medicine such as acetaminophen or ibuprofen before the procedure.12
- Nuclear medicine scans, such as PET scans, have particular instructions based on the type of procedure. Some scans may require an enema to clear the bowels, while others may only require fasting for a set period of time. Patients must take care to disclose all medicines they take, over the counter and prescription, as well as nutritional supplements. Reactions to nuclear medicine imaging is rare, but patients who have had adverse reactions in the past must disclose that before testing occurs.10
- Ultrasounds rarely require any special preparation. Patients may be asked, however, to fast, take a laxative, or use an enema prior to the procedure if the abdomen is being imaged. Abdominal ultrasounds work better with a full bladder, so patients may be instructed to drink water before the procedure.11
Oncologic imaging is an important part of all aspects of cancer care, from diagnosis and staging to treatment and recovery. But these procedures can also be sources of stress, anxiety, and discomfort. To ensure the best possible imaging results, it's critical that patients read and understand the imaging center's instructions, and share any questions or concerns with the imaging technologist. Knowing how to prepare, and what different imaging tests entail, can help patients and their loved ones decrease tension and anxiety prior to the procedure.13
- "Cancer Imaging Program." https://imaging.cancer.gov/imaging_basics/cancer_imaging/uses_of_imaging.htm. Accessed December 25, 2018.
- "Mammogram - Mayo Clinic." https://www.mayoclinic.org/tests-procedures/mammogram/about/pac-20384806. Accessed December 26, 2018.
- "Lung Cancer Screening Program." https://www.mskcc.org/cancer-care/risk-assessment-screening/screening/lung?gclid=Cj0KCQiAjZLhBRCAARIsAFHWpbFd4uarJldT7g1mhq4i0HlvGDShul-qwW7vuZRDVW9KVHAMyl48AbEaAi40EALw_wcB. Accessed December 25, 2018.
- "Stages of Cancer." https://www.webmd.com/cancer/cancer-stages#1. Accessed December 27, 2018.
- "Follow-Up Care for Breast Cancer." https://www.cancer.net/research-and-advocacy/asco-care-and-treatment-recommendations-patients/follow-care-breast-cancer. Accessed December 27, 2018.
- "CT Scan for Cancer." https://www.cancer.org/treatment/understanding-your-diagnosis/tests/ct-scan-for-cancer.html. Accessed December 27, 2018.
- "MRI for Cancer." https://www.cancer.org/treatment/understanding-your-diagnosis/tests/mri-for-cancer.html. Accessed 27, 2018.
- "X-rays and Other Radiographic Tests for Cancer." https://www.cancer.org/treatment/understanding-your-diagnosis/tests/x-rays-and-other-radiographic-tests.html. Accessed December 27, 2018.
- "Mammograms Basics" https://www.cancer.org/cancer/breast-cancer/screening-tests-and-early-detection/mammograms/mammograms-what-to-know-before-you-go.html. Accessed December 27, 2018.
- "Nuclear Medicine Scans for Cancer." https://www.cancer.org/treatment/understanding-your-diagnosis/tests/nuclear-medicine-scans-for-cancer.html. Accessed December 27, 2018.
- "Ultrasound for Cancer." https://www.cancer.org/treatment/understanding-your-diagnosis/tests/ultrasound-for-cancer.html. Accessed December 27, 2018.
- "Mammogram - Mayo Clinic." https://www.mayoclinic.org/tests-procedures/mammogram/about/pac-20384806. Accessed December 27, 2018.
- "Cancer Scans & Imaging | How to Prepare." https://www.merckengage.com/conditions/cancer/cancer-imaging. Accessed December 27, 2018.
- "What is Vascular and Interventional Radiology." https://www.hopkinsmedicine.org/interventional-radiology/what_is_IR.html. Accessed January 5, 2019.
- "NCCN Imaging Appropriate Use Criteria." https://www.nccn.org/professionals/imaging/default.aspx. Accessed January 6, 2019.
- "iRefer: making the best use of clinical radiology, eighth edition." https://www.rcr.ac.uk/publication/irefer-making-best-use-clinical-radiology-eighth-edition. Accessed January 6, 2019.
- "Imaging and IGRT in Liver Cancer." https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3428059/. Accessed January 23, 2019.
- "Imaging and radiology: MedlinePlus Medical Encyclopedia." https://medlineplus.gov/ency/article/007451.htm. Accessed January 25, 2019.