CT scans are valuable for finding cancers, but deliver a lot of radiation in the process. That's an especially big concern for children.
Full body CT scans can save lives by helping detect cancer early. But the scans use high doses of radiation to create their detailed images, which means they also increase patients' risk of developing cancer later on in life.
Children and teenagers are at greatest risk, because they tend to live long enough to develop secondary cancers. And their growing tissues may be more susceptible to radiation.
Doctors are overprescribing CT scans to kids, a recent study found. And radiation exposure from the scans can increase children's risk of brain cancer and leukemia, according to an international study published last year. A single CT scan can contain hundreds of times as much radiation as a regular X-ray.
So researchers have been looking for ways to reduce the amount of radiation patients are exposed to during diagnostic tests, either by dialing down the intensity of CT scans or by looking into safer imaging techniques.
Researchers at Stanford University think they've found another way. They used MRI scans, which don't use radiation, along with iron nanoparticle contrast agents to locate and identify tumors in young patients with lymphoma. Their results were published Tuesday in The Lancet Oncology.
courtesy Heike E. Daldrup-Link
Scans through the lower neck and upper chest show malignant lymph nodes (yellow/white areas) on an MRI with iron contrast (left) and a PET scan.
Scans through the lower neck and upper chest show malignant lymph nodes (yellow/white areas) on an MRI with iron contrast (left) and a PET scan. courtesy Heike E. Daldrup-Link
"What we developed is a one-stop-shop imaging test that can diagnose a primary tumor without any radiation exposure," says Dr. Heike Daldrup-Link, a radiologist and associate professor at Stanford. "That is, I think, the most exciting part of this study."
Patients are first injected with a dose of tiny sugar-coated iron oxide particles, which is currently FDA approved as a supplement for patients with iron deficiency. Under an MRI, the iron causes healthy tissue to appear darker, making tumors stand out.
While some MRI contrast agents have brought up safety concerns — a common contrast agent called gadolinium can be harmful for people with kidney problems — Daldrup-Link says the iron nanoparticles used in the Stanford research are fairly safe. In rare cases, people are allergic to them – most likely to dextran, the sugar that coats the iron particles, she says. Stanford screened all the patients for allergies before administering the iron. "In our patients, we did not see any side effects," she says.
"Technically, anyone who has an up to date MRI scanner could get these images," Daldrup-Link tells Shots. But the researchers need to go a few steps further before this new MRI technique can be widely used.
The study tested the MRI technique in 22 patients between 8 and 33 years old. The next step is to test it in more patients, she says. The Stanford researchers have teamed up with five children's hospitals in North America, and are looking to conduct a larger trial.
And other researchers are investigating the same technique to detect brain tumors and to track stem cells.
"Next, doctors need to be convinced that our new test provides the clinically needed information," says Daldrup-Link.