Ultrasound-based sensors for the fusion and motion correction of MRI and PET/CT data

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Project summary Radiology departments are equipped with many different types of medical imaging scanners, such as Magnetic Resonance Imaging (MRI), Positron Emission Tomography (PET), Computed Tomography (CT), X-ray, ultrasound imaging (USI) and Single-Photon Emission Computed Tomography (SPECT), among others. Clearly, none of these modalities is ideal; otherwise, there would be no rationale for anybody to purchase any others. Each modality is characterized by its own contrast mechanism and provides its own type of information. An ideal scanner might be defined here as one that could provide any of these contrasts, whose hardware would include that required for all of the main scanning techniques, whereby one could simply select the desired scan type, e.g., MRI+CT+USI, and proceed. Clearly, in practice, such an ideal scanner would be quite impractical. Hardware components associated with each modality would compete for the small amount of space available around the patient and these components would interfere in ways that might seriously impede their functioning. Even if such technical problems could be solved, complexity would likely drive cost to prohibitive heights. A more realistic multi-modality strategy is to perform scans sequentially, on different physical scanners, and to fuse images afterward, mostly through software. Exceptions include hybrid scanners such as PET/CT, which are widespread, and PET/MRI, which are available but uncommon. The fact that both involve PET is not a coincidence, but rather a testimony to the fact that PET may well currently be the best available tool for diagnosing/staging cancer, and that it further requires good anatomical images such as those provided by CT or MRI for proper attenuation correction maps to be calculated. In particular, PET/MRI scanners are true masterpieces of engineering. The two combined modalities prove especially useful in the fields of cancer detection/staging and neuroscience. Arguably, the main problem with these scanners may be that they are rare and very expensive, two problems that are not unrelated of course. Masterpieces of engineering may demand respect but they also tend to demand a high price; in contrast, the present project represents a practical and low-cost approach to multi-modality imaging. For the same reasons that drove vendors to develop PET/MRI scanners, because both modalities are so powerful in their own rights yet so complementary as well, we focus here on combining PET and MRI acquisitions. But the proposed work is not limited to these two scan types, and in the future it might well prove generalizable to any combination of sequential scans from any imaging modalities and/or radiation therapy devices. It is based on the developments of ultrasound-based sensors that can be attached to the patient's skin and accompany him/her through sequential scans, acting as a common thread across modalities. Fifty-four patients scheduled for a clinical PET/CT scan will be recruited to validate the proposed technology, and half of them will be scanned by MRI as well.