Multimodality Imaging Approaches: PET/CT vs. PET/MR

For many years PET/CT has been the preferred imaging method for the diagnosis, staging and restaging of malignant diseases and metastases along with the evaluation of treatment responses.

Now however, PET/MR is an up-and-coming option as a viable competing imaging technology. PET/CT is the combination of anatomical structures from CT and the functional information from PET into one fused image; however, the system has some drawbacks.

First, the radiation dose to the patient; in an environment that is increasingly concerned with the effect of radiation on patients and dose reduction, PET/CT is at a disadvantage to PET/MR. Second, because PET and CT are hard wired back to back, sharing a patient bed does not allow simultaneous data acquisition and can cause artifacts by patient movement or respiration.

Recently, researchers have been concentrating on how to combine PET and MRI into one single system, which would mean integrating the PET detectors in the MRI scanner.

Photo Credit – National Institutes of Health

Siemens Healthcare has introduced the Biograph MMR which consists of both PET and MR technology housed in one device, providing a single image. The system is configured such that a PET ring detector fits inside a 3T magnet for simultaneous imaging.

Philips’ offering, the Ingenuity TF, places the MR and PET scanners about 10 feet apart with the patient table in the middle.  The table rotates so the patient is scanned in the exact same position by each machine sequentially.

GE is still finalizing their system which will consist of a PET/CT + MRI.  MR and PET exams will be performed sequentially with a shared patient transport table system.  Patients remain on the table and the table moves between rooms/devices.  After the sequential exams, the GE system merges the data.

Hospitals will soon not only have to make decisions between PET/CT and PET/MR systems, they will have to assess each vendor’s technologies and see what scanning configuration works best for their needs. You can be sure that I’ll be watching this space very closely in the near future and talk about any new developments.

So the question is now: PET/CT vs. PET/MR; although PET/MR is new and very expensive, radiation doses to patients will be much lower, so it’s decision making time. Which do you prefer?

Jamie Dildy, BS, R.T. (R)
Jamie Dildy, BS, R.T. (R), Clinical Analyst — At MD Buyline, Ms. Dildy is the clinical analyst for mini and mobile C-arms, contrast injectors, lithotripters, SPECT and SPECT/CT, PET/CT and PET MR, urology systems, gamma detection systems and infant care and infant security. She has over 10 years of experience as an interventional radiology technologist and holds her registry license in Radiology Technology through the American Registry of Radiology Technologists (ARRT). Ms. Dildy graduated from The University of Arkansas for Medical Sciences in with a Bachelor of Science in Radiologic Technology.