The introduction of simultaneous MR/PET scanners has, for the first time, provided a synergistic imaging platform where the simultaneously acquired dual-modality data can be used to provide significant improvements in image quality, interpretation and quantification. Motion correction stands as one application where immediate benefit can be garnered from the use of such synergies. Motion correction of PET images relies on MR-based motion tracking information that can be used to sort the PET listmode data into different motion states or gates. The MR images corresponding to these gates are then used to modify the system matrix and produce motion-corrected PET images. Prior implementations of this approach have relied on the use of a self-navigated sequence, such as a stack of stars [1], where the motion tracking information is derived from the center of k-space. While effective, however, this approach only allows the correction of the listmode data acquired when the motion tracking sequence is used. Recently, it has been demonstrated that self-refocused [2] MR signals or signatures of coil load variations [3,4] can be used to monitor respiratory, and sometimes, cardiac motion. In this work we demonstrate that the use of a reference RF signal (the pilot tone, PT) can be used, as proposed in [5], as an effective means to identify individual motion states throughout the duration of an entire MR/PET examination. The PT navigator approach was implemented on a Siemens MAGNETOM mMR (Siemens Healthcare, Erlangen, Germany) using a 2cm surface coil (Fig 1), which was placed outside the bore of the magnet. The coil was driven by a signal generator with -20dBm amplitude. The PT frequency was between 7 and 50Khz away from the center frequency of the scanner (123.216MHz) to avoid interference with the desired MRI data. Data were acquired with both conventional gradient echo (TR/TE=20/10ms, BW=260Hz/Pixel, 1x5mm slice) as well as a golden angle radial imaging (RI) in-house-modified prototype sequence (TR/TE=7.92/4.94ms, BW=680Hz/Pixel, 48x6mm slices, 2002 radial views) equipped with an additional rosette [6] navigator readout, which allows for comparison of the PT navigator to the conventional k-space center self-navigation [7] and coil fingerprinting approaches [2]. The PT data from different coils in the receive array were used to sort the measured echo into motion 'bins'. These motion bins were then used to reconstruct the images corresponding to the different motion states.Figure 2 shows a GRE image from a normal human volunteer acquired while using the PT signal to monitor the motion throughout the scan. A plot of the temporal variation of the PT signal illustrates that the variations in its amplitude are correlated to the motion of the chest cavity. Further analysis of this signal allows the synthesis of motion bins from which individual motion states can be reconstructed (Figure 3). Use of the rosette-navigated RI sequence allows exclusive monitoring of the motion signal via the rosette readout (Figure 4). Fourier analysis of this signal demonstrates the presence of a respiratory peak (Figure 5). This signal correlates well with the tracking signal from the center of k-space (Figure 6)and can, likewise, be used to generate motion bins (Figure 7) from which 3D motion states can be reconstructed (Figure 8).We have demonstrated that an external RF signal, as proposed in [5], can indeed be used to provide effective respiratory motion tracking information in real time. The technique is straightforward to implement, requires minimal hardware, and is transparent to the pulse sequence since specialized navigator modules are not required. Integration of this tracking signal with MR image reconstruction via sorting into motion bins is compatible with most MR sequences and can provide a means to fully navigate an entire MR/PET examination.