Radiology: Imaging & Scans

What is Radiology? 

Radiology is the use various forms of energy to produce images of/inside of the body. This is different than radiation therapy which is the use of various forms of energy to destroy and kill cancer cells. 

What can scans tell us? 

Scans provide information that can help determine: 

• your diagnosis 
• your prognosis
• your cancer's response to therapy (how well did treatment work?)
• if your cancer has metastasized (spread to other areas of the body)
• the status of your cancer at any time from diagnosis onward
• the recurrence or relapse of your cancer

QUICK OVERVIEW: Radiographic Analysis Modalities

Imaging Modalities:

• CT (Computed Tomography or CAT) scan: uses x-rays to create 3D images, exposes patients to radiation
• MRI (Magnetic Resonance Imaging): uses magnets and radio waves to create 3D images; does not expose patient to radiation; no metal can be in or on the body including jewelry, accents on clothing, microbead/micro ring hair extensions, hearing aids, pacemakers and other implanted medical devices.
• PET (Positron-Emission Tomography) with radiolabeled glucose (F-fluorodeoxyglucose, FDG): visualizes glucose uptake in tissues throughout the body; tests for metabolically active cancer cells, exposes patients to radiation
• SPECT (Single photon emission tomography) can detect changes in cerebral blood flow, exposes patients to radiation
• X-Ray- uses ionizing radiation to produce 2D images, exposes patients to radiation
• Ultrasound- uses sound waves to produce images; does not expose patient to radiation
• Mammography- uses x-rays to produce 2D and 3D images, exposes patients to radiation
• Endoscopy- uses a camera and light to examine internal organs and tissues

See the graphic in the next section for a comparison of MRI, CT, and PET scans.

Contrasts Used in Cancer Imaging

Contrasts are substances that are administered to a patient prior to an imaging study to highlight different structures, materials, features, or functions inside the body.

Types of Contrast and Administration Routes

• Iodine-based contrast: used for CT and X-ray;  IV, injection, and sometimes oral or rectally administered
• Barium sulfate: used for CT and X-ray; oral and rectal administration
• Radioactive glucose tracers: used for PET scans; IV administration
• Gadolinium-based contrast: used for MRI; IV administration
• Saline
• Gas/Air

Surveillance

Surveillance is the period after treatment has concluded or during maintenance therapy in which various tests, including medical imaging, are completed periodically to monitor for recurrence or changes in cancer. This term is also used more generally to refer to any tests used to monitor your cancer whether you are in therapy or not. 

Did you know? 

A square centimeter of cancer has about 1 billion cancer cells in it, and the smallest lesion/tumor we can usually detect with current imaging is a few millimeters. Imaging cannot detect microscopic disease or micrometastases. Due to the limitations of current cancer imaging technologies, it's important to recognize that a complete radiologic response (no tumors seen on scan) is not the same as a complete pathologic response (cancer is not detected in tissue or blood samples). If microscopic cancer exists in the body that cannot be seen on a scan, it can linger and potentially lead to a cancer recurrence. Talk to your doctor about tests that may help identify microscopic disease that remains after treatment, also known as a Minimal Residual Disease (MRD) tests. You can read more about MRD on our Labs, Biomarkers & ctDNA page. 

In the next few sections, we'll discuss test sensitivity and specificity, scope imaging procedures, and "scanxiety."

Specificity and sensitivity are quantitative measures of a test's clinical performance, meaning how good is the test at doing what it's designed to do for patients? 

These concepts can get a little fuzzy given the way they're often described, so we won't focus too much on all the details right now. Instead, we'll discuss how a test's sensitivity or specificity correlates with its results and what that means for you. 

Where's My Unicorn Test?

If you're looking for a test, be it a scan, blood test, or other lab test, to have 100% specificity and 100% sensitivity, you're going to be disappointed because it's not a thing. This would be considered a unicorn and, even though researchers and test developers strive for 100+100 in theory, in practice it's not realistically achievable. As you can imagine, there is give-and-take when designing these tests and factors like cost, time, availability of resources, feasibility, safety, reliability, and accuracy all come into play. Each of these factors can have an impact on the test's sensitivity and specificity, usually in an inverse relationship to each other.  If one goes up, the other goes down. You can see the tug-of-war that can arise when designing a test and trying to determine the avenue (100% specificity or 100% sensitivity) that ultimately provides the most benefit and least harm to patients.  Since there are no perfect tests, we have to work with the ones we've got so let's take a look at these two measures of clinical performance: specificity and sensitivity. 

Up first...

SPECIFICITY

How specific is that test? is another way of saying...

• How likely will the test differentiate between a patient with cancer and one without?
• How likely will the test be negative when I don't have cancer?
• If I do not have cancer, how many times out of 10 will this test give a negative result?

• If the test's specificity is 87% it means that 87% of people tested who do not have cancer will have a negative test result. This is called a true negative. It is true that the patient with the negative test does not have cancer. 

• If a test is more specific, it will result in fewer false positives.
• If a test has lower specificity, it will produce more false positives. If you happen to take a test that has low specificity, it may be helpful to keep in mind that there is a greater chance you may receive a false positive which would indicate that you DO have cancer even if you do not. This can definitely cause some unnecessary stress if you mistakenly believe the cancer is back.

SENSITIVITY

How sensitive is that test? is another way of saying...

• How likely will the test identify cancer that is there? 
• How likely will the test be positive when I do have cancer?
• If I have cancer, how many times out of 10 will this test pick it up? 

• If the test's sensitivity is 87% it means that 87% of people tested who do have cancer will have a positive test result. This is called a true positive. It is true that the patient with the positive test result does have cancer. 

• If a test is more sensitive, it will result in fewer false negatives. 
• If a test has lower sensitivity, it will result in more false negatives. If you happen to take a test that has low sensitivity, it may be helpful to keep in mind that there is a greater chance you may receive a false negative which would indicate that you do NOT have cancer when you actually do. This scenario can mislead you to believe the cancer is gone when, unfortunately, that is not the case. 

Another way to describe test results: 

True positive- test is positive and patient does have cancer

True negative- test is negative and patient does not have cancer

False negative- test is negative but patient does have cancer

False positive- test is positive but patient does not have cancer

Please don't worry that every test result is inaccurate or misleading. These are the best tests we have and they are reliable MUCH more often than not. Plus, there are multiple ways to test for most things which means there are likely tests out there that can step in and double-check the work of the previous test.

When your doctor orders a test, ask them if it's more likely to produce a false positive (tells me I have it when I don't) or false negative (tells me I don't have it when I actually do). By knowing that information, you can shift your expectations as needed about the test results. If you're concerned about a result, you can ask your doctor how confident they are in the result, if you can retake it and/or if there is another test out there that could provide similar information.

"People often feel especially anxious when they’re due for a scan or other follow-up medical visit—a feeling that some cancer survivors have dubbed “scanxiety.” 'Scans are like revolving doors, emotional roulette wheels that spin us around for a few days and spit us out the other side,' wrote cancer survivor Bruce Feiler, in a June 2011 Time magazine article. 'Land on red, we're in for another trip to Cancerland; land on black, we have a few more months of freedom.'"(source)

Scanxiety is a portmanteau combining the words "scan" and "anxiety," and it's used to describe the worry, fear, uncertainty, and anxiety that accompanies an upcoming scan or while waiting on the results of a recent scan. This is a common feeling expressed by both patients and their caregivers, and though it usually only lasts a matter of days, the emotions can be powerful and interfere with daily life. 

"Just don't think about it" is not a reasonable solution. What's the deal with people telling cancer patients not to "think" or "worry" about things, anyway? Has this ever worked? Is this the best advice we have for people going through (likely) the most emotionally and physically challenging experience of their life?  We want them to take their REAL, VALID emotions and concerns and just ignore them and stuff 'em under the couch?  Ridiculous. 

Scans are the most "telling" tests cancer patients receive on a regular basis. They let us know what the heck is going on with the cancer. Where is it? How big is it? How did the size(s) change? There are few things in life that may be more impactful than learning the status of your cancer, and that should not be minimized.  

Cancer, as a disease, is characterized as "out of control," and that characterization seems to mirror how many patients feel from the point of diagnosis onward. And nearly every aspect of a scan is either unknown to or out of the patient's control. The frequency, the ordering, the scanning, the interpreting, the release of the report—it all has to be left in someone’s hands other than the patient’s. That can be an uncomfortable and vulnerable position to be in, compounded by the potential magnitude of the scan’s findings. Even if everything is pointing to the likelihood of a clear scan, the possibility of bad news exists, even if it’s slim, because cancer is a jerk and plays by its own rules. Long story short, patients experiencing scanxiety are well within the bounds of “it makes total sense to feel that way.” Instead of hushing patients or insinuating that their concerns are silly or unfounded, we should be looking for meaningful ways to help. Hearing and acknowledging patients’ concerns is the first step.  

Keeping It Simple

In most scenarios, there are only 5 possible outcomes of an anatomical cancer scan (MRI, CT, etc.) used to assess treatment effectiveness or durability of remission*: 

• Cancer is the same/no change
• Cancer is smaller
• Cancer is larger
• Cancer has spread to new location(s) or returned/recurred
• Cancer cannot be seen/detected

*Durable remission, or durability of remission, refers to the length of time that cancer maintains its absence/stays in remission (the duration of remission). This period is most often assessed during surveillance, after treatment has ended.

There are not endless potential outcomes when you go in for a scan. The possibilities are limited, which means you don't have to burden your brain by exploring endless potential outcomes. Focus on the five. Maybe having fewer things to consider can help quiet anxiety or maybe playing out possible scenarios helps by eliminating some future unknowns. Maybe productive distractions can help, too. If you find something that really helps you or a loved one cope with scanxiety, please share!

Can Planning Ahead Calm Your Mind?

Before your scan, think about your desired next steps for each of the five possible outcomes above. This approach may help you feel more in control. What would you want to do next if the cancer got bigger? If it shrunk? If it popped up in a new place? What if it didn’t budge? And what would you want to do if no cancer was found? Going in with a plan, even if it’s unwritten or tentative, gives you somewhere to start when the time comes to map out the next phase of your cancer journey with your doctor. 

Check out our Mental Health & Cancer page for resources on coping and stress reduction.

Types of "Scopes" in Cancer Detection and Diagnosis

Endoscopy: "Endo-" meaning inside and "-scope" meaning to see; a camera is inserted into the body to visualize internal organs and structures

Some common endoscopic procedures:

• Colonoscopy: to visualize the colon from cecum to rectum
• Upper GI Endoscopy: to visualize the esophagus, stomach, and the duodenum (part of the small intestine)
• Bronchoscopy: to visualize the lungs
• Sigmoidoscopy: to visualize the sigmoid section of the colon and the rectum
• Colposcopy: to visualize the cervix, vagina, and vulva
• Cystoscopy: to visualize the bladder and urethra
• Laparoscopy: to visualize the inside of the abdomen and pelvis