A 16-channel MR coil for simultaneous PET/MR imaging in breast cancer.

OBJECTIVES: To implement and evaluate a dedicated receiver array coil for simultaneous positron emission tomography/magnetic resonance (PET/MR) imaging in breast cancer.

METHODS: A 16-channel receiver coil design was optimized for simultaneous PET/MR imaging. To assess MR performance, the signal-to-noise ratio, parallel imaging capability and image quality was evaluated in phantoms, volunteers and patients and compared to clinical standard protocols. For PET evaluation, quantitative (18) F-FDG PET images of phantoms and seven patients (14 lesions) were compared to images without the coil. In PET image reconstruction, a CT-based template of the coil was combined with the MR-acquired attenuation correction (AC) map of the phantom/patient.

RESULTS: MR image quality was comparable to clinical MR-only examinations. PET evaluation in phantoms showed regionally varying underestimation of the standardised uptake value (SUV; mean 22 %) due to attenuation caused by the coil. This was improved by implementing the CT-based coil template in the AC (<2 % SUV underestimation). Patient data indicated that including the coil in the AC increased the SUV values in the lesions (21 ± 9 %).

CONCLUSIONS: Using a dedicated PET/MR breast coil, state-of-the-art MRI was possible. In PET, accurate quantification and image homogeneity could be achieved if a CT-template of this coil was included in the AC for PET image reconstruction.

KEY POINTS: • State-of-the-art breast MRI using a dedicated PET/MR breast coil is feasible. • A multi-channel design facilitates shorter MR acquisition times via parallel imaging. • An MR coil inside a simultaneous PET/MR system causes PET photon attenuation. • Including a coil CT-template in PET image reconstruction results in recovering accurate quantification.