PET attenuation correction for rigid MR Tx/Rx coils from 176Lu background activity.

We present a straightforward method to measure the attenuation of Tx/Rx coils in simultaneous MR-PET imaging based on the natural 176Lu background contained in the scintillator of the PET detector without the requirement of an external CT scanner or PET scanner with transmission source. The method was evaluated on a prototype 3T MR-BrainPET produced by Siemens Healthcare GmbH, both with phantom studies and with true emission images from patient/volunteer examinations. Furthermore, the count rate stability of the PET scanner and the x-ray properties of the Tx/Rx head coil were investigated. Even without energy extrapolation from the two dominant γ energies of 176Lu to 511 keV, the presented method for attenuation correction, based on the measurement of 176Lu background attenuation, shows slightly better performance than the coil attenuation correction currently used. The coil attenuation correction currently used is based on an external transmission scan with rotating 68Ge sources acquired on a Siemens ECAT HR  +  PET scanner. However, the main advantage of the presented approach is its straightforwardness and ready availability without the need for additional accessories.
PMID: 29408803 [PubMed - in process]

Source: Physics in Medicine and Biology - February 6, 2018 Category: Physics Authors: Lerche CW, Kaltsas T, Caldeira L, Scheins J, Rota Kops E, Tellmann L, Pietrzyk U, Herzog H, Shah NJ Tags: Phys Med Biol Source Type: research