title: Small animal simultaneous PET/MRI: initial experiences in a 9.4 T microMRI.
abstract: We developed a non-magnetic positron-emission tomography (PET) device based on the rat conscious animal PET that operates in a small-animal magnetic resonance imaging (MRI) scanner, thereby enabling us to carry out simultaneous PET/MRI studies. The PET detector comprises 12 detector blocks, each being a 4 × 8 array of lutetium oxyorthosilicate crystals (2.22 × 2.22 × 5 mm(3)) coupled to a matching non-magnetic avalanche photodiode array. The detector blocks, housed in a plastic case, form a 38 mm inner diameter ring with an 18 mm axial extent. Custom-built MRI coils fit inside the positron-emission tomography (PET) device, operating in transceiver mode. The PET insert is integrated with a Bruker 9.4 T 210 mm clear-bore diameter MRI scanner. We acquired simultaneous PET/MR images of phantoms, of in vivo rat brain, and of cardiac-gated mouse heart using [(11)C]raclopride and 2-deoxy-2-[(18)F]fluoro-D-glucose PET radiotracers. There was minor interference between the PET electronics and the MRI during simultaneous operation, and small effects on the signal-to-noise ratio in the MR images in the presence of the PET, but no noticeable visual artifacts. Gradient echo and high-duty-cycle spin echo radio frequency (RF) pulses resulted in a 7% and a 28% loss in PET counts, respectively, due to high PET counts during the RF pulses that had to be gated out. The calibration of the activity concentration of PET data during MR pulsing is reproducible within less than 6%. Our initial results demonstrate the feasibility of performing simultaneous PET and MRI studies in adult rats and mice using the same PET insert in a small-bore 9.4 T MRI.
authors: Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, USA.
authors: Sri Harsha
authors: SH
authors: Maramraju
authors: S David
authors: SD
authors: Smith
authors: Sachin S
authors: SS
authors: Junnarkar
authors: Daniela
authors: D
authors: Schulz
authors: Sean
authors: S
authors: Stoll
authors: Bosky
authors: B
authors: Ravindranath
authors: Martin L
authors: ML
authors: Purschke
authors: Sergio
authors: S
authors: Rescia
authors: Sudeepti
authors: S
authors: Southekal
authors: Jean-François
authors: JF
authors: Pratte
authors: Paul
authors: P
authors: Vaska
authors: Craig L
authors: CL
authors: Woody
authors: David J
authors: DJ
authors: Schlyer
mesh_terms: D000818:Animals; D001921:Brain / Q000000981:diagnostic imaging / Q000473:pathology; D002138:Calibration; D005260:Female; D019788:Fluorodeoxyglucose F18; D006321:Heart / Q000000981:diagnostic imaging / Q000502:physiology; D008187:Lutetium; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D008297:Male; D051379:Mice; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000295:instrumentation / Q000379:methods*; D020891:Raclopride; D011868:Radioisotopes; D019275:Radiopharmaceuticals; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D017640:Silicates
chemical_list: D011868:Radioisotopes; D019275:Radiopharmaceuticals; D017640:Silicates; D019788:Fluorodeoxyglucose F18; D020891:Raclopride; D008187:Lutetium