Project Summary / Abstract (from parent application)
We propose to create and explore a radio-frequency (RF)-penetrable positron emission tomography (PET)
system technology that can be inserted into a magnetic resonance imaging (MRI) system for acquiring
simultaneous PET/MRI data. Integrated PET/MRI has risen to the cutting edge of medical imaging technology,
showing promise to be a powerful tool in disease characterization as it enables the simultaneous measurement
of molecular, functional, and anatomical information in soft tissues of the body. Because of this promise,
companies such as Siemens, GE, and Philips have developed and are now offering combined PET/MR systems.
However, one of the challenges affecting the long-term impact of this technology is the current cost ($5-6M) due
to the huge investment required by a company to develop an integrated product, and the need for the user to
purchase both PET and MRI sub-systems. Our lab is addressing these issues by creating the world’s first RF-
penetrable PET ring, which can in principle be inserted into any existing MR system, while still allowing use of
the built-in MR RF transmit coil. This would avoid the expensive integration of the two modalities, which, up to
now, in order to achieve whole-body PET/MR, has required substantial modifications to the MR system, including
re-engineering the body transmit coil sub-system to reside inside the PET ring. Thus, the proposed technology
would substantially lower the cost barrier for an existing MR site to upgrade to PET/MR capability since they
would just need to purchase the RF-transmissive PET insert, and it also would reduce the industry investment
to achieve integrated PET/MRI.
Hypothesis: Using the novel electro-optical signal transmission scheme proposed, we can create a
PET insert that is penetrable to a RF field and thus can achieve simultaneous ToF-PET/MR using the
built in body transmit coil of an MR system. The basic idea to enable the PET ring insert to be RF-
penetrable (i.e. for the RF field to leak inside of the PET ring) is to have it electrically floating with respect to the
MR system, and to have small gaps between PET detector modules where the field lines can leak in. This
floating PET ring is made possible via the concept of “electro-optical” signal transmission, which draws from
the field of telecommunications; in our formulation, the fast scintillation detector signals are coupled to tiny
lasers, converted to near infrared light, and transmitted down long telecommunications-grade optical fibers,
thus enabling electrical isolation from the MR system. In addition, since the electro-optical approach uses
optical fibers, it substantially reduces the electrical footprint within the MR system compared to a PET system
design that uses long electrical cables, while achieving excellent spatial, energy, and temporal resolutions
required for PET. In this project, we will develop a full proof-of-principle of this RF-penetrable concept
via a brain-size PET insert, and test its RF transmissivity in a 3T MRI system. In order to achieve these
goals, we explore many innovative concepts.