Double Image: Adding PET/MR Systems into the Imaging Unit Mix

Article excerpt

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Health care has evolved gradually and consistently with the emergence of new technologies, especially those designed to improve the quality of patient care. New technologies long have aided clinicians in diagnosing and treating patients, particularly those with complex medical issues. This level of complexity is no more evident than in a health care facility's imaging department.

Within the past 20 years, combining imaging technologies has become popular. This practice, in fact, has become common in the world of nuclear medicine, where both positron emission tomography (PET) and single-photon emission computed tomography (SPECT) have been combined with computed tomography (CT) to create PET/CT and SPECT/CT, respectively.

Until recently, most clinicians have been leaning on PET/CT and SPECT/CT for the majority of their work in oncology. But that's about to change.

What is PET/MR?

PET/MR combines PET, which uses a tracer to highlight tumors, and magnetic resonance (MR) imaging, which uses a strong magnetic field to produce images of soft-tissue filled areas. The advantage of combining these two technologies into one system is that oncologists now are able to get the best available image of a tumor located in a soft tissue area.

This hybrid system can provide clinicians with new insights into the worlds of neuroscience and neurological disorders. It also will allow oncologists the option to scan a patient's whole body, which is especially important with increasing instances of cardiovascular disease and cancer. Imagine a system that can scan a patient's entire body with the sensitivity to detect any brain, bone or liver tumors all in one scan.

Another advantage of PET/MR is the ability to utilize other imaging techniques to complement the main technology. For example, by using spectroscopy with a PET/MR scan, clinicians can investigate the properties of specific organs to determine if there are any abnormalities. Functional MRI (fMRI) also can be used along with PET/MR to assess brain function by detecting a contrast dependent on the blood-oxygenation level. Combining PET with cardiac MRI and whole-body MR angiography also enables physicians to detect and differentiate between vulnerable plaques.

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Along with these advantages, PET/MR also eliminates the existence of ionizing radiation incurred by the patient when compared with PET/CT. The amount of radiation exposure through PET/CT can be significant, especially if repeated whole-body examinations are required for monitoring purposes. By using PET/MR instead of PET/CT, radiation is reduced to the minimal amount emitted by the radiopharmaceutical required for the PET portion of the scan.

Present and future

The first PET/MR prototype was assembled at the University of California-Davis in 1997. Since then, the major imaging vendors have been working to perfect the PET/MR technology to serve the needs of health care.

As of 2011, the first two PET/MR models were approved for sale in the United States by the Food and Drug Administration. One additional model since has been approved.

In general, there are two main configurations in PET/MR.

* The simplest configuration is a tandem one, where PET and MR images are taken sequentially in two separate scanners. This can be achieved either by having both systems in the same room or in separate rooms. The former rotates the patient table between imaging systems, while the latter moves the same patient transfer tabletop between both rooms and docks it on both system gantries. In addition to the simplicity of image registration, the advantages of a tandem configuration are that it's less expensive than a concurrent system and it minimizes claustrophobia because of the large space between scanners.

* The more complex method, known as concurrent PET/MR imaging, combines both PET and MR in a single platform. …