Medically reviewed by Susan Kerrigan, MD and Marianne Madsen
When a patient first hears they might have cancer, they’re usually focused on the disease, not the tests used to detect it. Yet there are several options for cancer detection. In order to determine the presence of cancer along with its stage and location, X-rays have long been used. So are there alternatives to radiation? The answer is yes, but whether you opt for an MRI, ultrasound, or an X-ray depends on several factors.
X-Rays and CT Scans
Diagnosis (and treatment) of cancer with X-rays is over a century old, but the CT scan is a more recent development. The CT (computed tomography) scan creates a collage of X-rays. During the procedure, the patient lies down on a table before traveling into a doughnut-shaped ring. Inside the ring, a machine whirs around the patient, shooting a burst of X-rays from multiple angles. Combined by a computer, a CT scan offers 3D pictures of your bones, organs, and other tissues. It’s possible to get an image of your body, from the neck to the thighs. For cancer diagnosis, the CT scan is helpful for its ability to highlight abnormalities.
British engineer Godfrey Hounsfield used half-century old mathematical theories to guide the CT scan’s development. The high school dropout was on vacation when he became obsessed with the idea of transforming a picture of a box into a 3D image. From imagining the box as a series of slices, it was a natural progression toward using an X-ray machine to capture “slices” of a human being. These slices, once assembled, offer a far more complete image than a single X-ray ever could. Interestingly, the development of the CT scan is partly owed to the success of the Beatles –– Electric and Music Industries (EMI), the developer of this technology, also owned Abbey Road Studios where the Beatles recorded their hits. Because of this, the band’s album sales helped fund medical research.
When the CT scan became available in 1972, it revolutionized medicine. Unfortunately, all those X-rays come at a price. CT scans can deliver 300 times more radiation than a single X-ray. Although CT scans may increase the possibility of developing fatal cancer to around one in 2000, the risk of dying from cancer under normal circumstances is far higher. Although it’s considered low risk, that doesn’t change the fact that CT scans account for over three-quarters of the effective radiation dose delivered from all imaging procedures. Yet only around 11% of X-ray based examinations are CT scans.
A CT scan is an extremely valuable part of an oncologist’s arsenal for detecting cancer and for monitoring its recurrence. It’s also ideal for seeing if cancer has spread –– as it often does with lung, liver, or bone cancer. CT scans are also used to determine the cancer’s stage of development. Unfortunately, many patients need to have several scans a year. The radiation risk is especially elevated for children –– and young people who have any CT scans at all often have more than one.
As with everything, there is a risk-to-reward ratio to consider. By not using a CT scan, it’s possible to leave cancer undetected –– and later stage cancer is usually more lethal. A small child with a severe head injury is at greater risk of death or disability from the injury than from the scan. Still, there are detection methods that don’t use any radiation.
MRI
Just as with the CT scan, a patient undergoing an MRI (magnetic resonance imaging) also lies on a table and is slid into a round device. Like the CT scan, patients undergoing an MRI get detailed images of their insides –– except this time instead of X-rays, radio waves combined with a powerful magnet work to create the pictures. Inside the MRI machine, it takes far longer to create the images than it does during a CT scan. It’s an arduous process –– sometimes lasting up to 40 minutes. During that time, patients are confined within the thick “donut” while enduring the noise of loud machinery. Claustrophobes are sometimes unable to complete the test. Others are challenged because certain examinations require holding their breath. Still there isn’t any radiation involved, which is beneficial. Plus, MRIs excel at detecting prostate cancer, uterine cancer, and certain liver cancers –– which are much harder to see on a CT scan.
Ultrasound
Like the MRI, ultrasound doesn’t use radiation. Although the results of an ultrasound are less detailed than MRI or CT images, they are good at detecting soft tissue diseases that aren’t revealed by X-rays. Using high-frequency sound waves which pass through your body, the ultrasound can create sonograms. These pictures show your organs’ structures and the way blood flows through blood vessels. Ultrasound machines are recommended for distinguishing cysts from tumors.
Doctors often start with a CT scan and use MRIs or ultrasounds for follow up. Parents should discuss with the doctor when CT scans can be avoided and verify that the machine has been calibrated for children. For patients, knowing the risks and what is involved is an important first step toward what can be a lengthy period of treatment.
Written by John Bankston
