Dr. Greene’s Answer:
Plain x-rays use low doses of radiation, but give limited information. Sometimes this limited information is exactly what is needed. What to do if more detail is needed? The CT scan is one possibility.
As technology advances rapidly, medical imaging possibilities are also changing quickly. Still, the most common alternatives to CT scans are ultrasounds and MRIs. Unlike CT scans, neither uses ionizing radiation. Ultrasound constructs a picture using sound waves; MRI uses magnetic fields to produce an image that often has greater clarity than a CT.
Ultrasounds are blocked by bone, so head ultrasounds are not an option once a child’s soft spot has closed. Current head MRIs are not a good option for emergency evaluation of head trauma, in part because they can take 45 minutes or more to obtain, even when everyone is available and ready. When it comes to most head trauma (once the soft spot has closed), the best imaging options remain skull x-rays (to look for bone fractures) and CT scans (to look for injuries inside the skull). The main alternative to these is careful examination and observation.
MRIs are almost always preferable to CTs for imaging the head, and usually for the spine, except during trauma or when MRIs are not practical – such as when there are metal clips in the head. MRIs provide equal or superior imaging without the ionizing radiation. MRIs are also better than CTs for most musculoskeletal problems. Unfortunately, since MRIs take so much longer, children often need to undergo sedation, with its own risks, in order to remain still long enough for an MRI.
For imaging the abdomen or pelvis, the best bet might be ultrasound, MRI or CT, depending on the situation. I prefer using ultrasound whenever it will work.
Within the chest, especially within the lungs, CT scans remain the option of choice for most situations – though even here, MRI may become the best over the next few years as the technology continues to improve.
Read More From This Series:
CT Scan Defined
CT Scan, Ultrasound or MRI?
CT Scan Safety
CT Scans and Radiation Exposure
CT Scan Risks
Higher Risks in Children
Who Should Receive a CT Scan?
X-Ray or a CT Scan?
Alternatives to a CT Scan
When Should a CT Scan be Performed?
Important Tip to Reduce Radiation
Questions to Ask before Every CT Scan
Other Radiation Exposures Measures That Radiologists Should Adhere to When Administering a CT Scan
CT Scans and Cancer
When are MRIs not Practical?
What is Ionizing Radiation?
Who are Radiologists?
Last reviewed: February 14, 2008