MRI works by using great big magnets that bounce sound waves off our tissues to create pictures of our insides. A more detailed explanation of MRI can be found HERE.
PET Scan uses a sugar molecule attached to a radioactive tracer and a CT image. The theory is that cells that are active are going to need sugar(glucose) to do their work and cancer cells are notorious for working overtime. So with a PET scan - you are injected with the radioactive glucose, you rest for 15-60 minutes to let it find the (metabolically) active cells and then you are put in the special PET/CT scanner to collect the images. But just as MRI can not tell you if a spot is malignant or benign, a PET scan just tells you which areas are active. If you have an infection, such as strep- that area would light up on a PET scan.
|Magnetic Resonance Imaging||Positron Emission Tomography/ Computed Tomography|
|TIme for scan||About 30-45 min per area scanned(about 2-3 hours whole body)||About 5-10 min per area(about 45 min whole body)|
|Cost||Varies from $1000- over $4000||Varies from $3000 and up|
|Effects||No hazards reported||Risks from radiation|
|Soft Tissue||Higher detail in soft tissues||Less detailed, better for tumors >2cm.|
|Bony Structures||Less detailed||More detailed|
|Best for||Soft tissues, inflammation, cross section pictures.||Bone injuries, lung and chest imaging, cancer detection, showing metabolic activity|
|Advantages||Can change the contrast of images, superior for detection of tumors, no radiation, few side effects to contrast||Good for imaging metabolic activity, shorter time in scanner|
|Disadvantages||Claustrophobia, can not use with metal implants, takes time and you have to be still. Cost||Uses ionizing radiation. Cost. Availability.|
So how do we balance the risks and the benefits from scans? It is often said in our group "a scan is only as good as the doctor reading it". The same goes for ordering scans when you have LFS. It is very important to speak with your doctor and that they understand your concerns about cancer and potential radiation exposure. It is also important to keep an open mind and listen to your doctor when they have a concern that leads them to order a scan. A cancer that goes undetected, cannot be treated. Some questions to ask you doctor when discussing further tests:
Is it necessary?
What are the benefits?
What are the risks?
Is this scan going to give us the most amount of information with the least amount of radiation?
By understanding what the scans are and how doctors use them to diagnose and treat, we can better advocate for ourselves while living LFS. Radiation is all around us and can be dangerous to our already mutated cells. But radiation can be very useful in diagnosing tumors, we just have to find the balance between risks and benefits and one of the best ways to do this is to speak with your doctor about it.
CT Scan vs MRI
PET/CT Screening and LFS-
Masciari S, Van den Abbeele AD, Diller LR, et al. F18-Fluorodeoxyglucose–Positron Emission Tomography/Computed Tomography Screening in Li-Fraumeni Syndrome. JAMA. 2008;299(11):1315-1319. doi:10.1001/jama.299.11.1315.
Dana Farber- Scans Spot Hidden Tumors in Rare Cancer Syndromes