(PET-CT) and Magnetic Resonance Imaging (MRI) in Mice

Benefits and limitations of Positron Emission Tomography-Computed Tomography (PET-CT) and Magnetic Resonance Imaging (MRI) in mice

N. Hebert1, C. Brochu1, J. Rousseau2, A. Varela3. 1Charles River, Sherbrooke, 2CIMS-CRCHUS, Sherbrooke, Quebec, Canada, 3Charles River, Montreal

1 Introduction 3 Results 4 Conclusion Good correlation was seen between cardiac Imaging enables in vivo evaluation of a multitude of physiological and/or pathological processes and has Cardiac parameters measured were as follows: function parameters obtained by PET-CT and MRI Though both modalities can be used to assess cardiac function, depending on cardiac assessment the power to provide highly accurate data regarding organ/system structure and function, earlier than (R2 = 0.7366 and r = 0.86). objectives, PET-CT presents advantages in providing metabolic information whereas MRI provides better traditional methods such as biochemistry and histology. Longitudinal monitoring of a pathological structure/function diagnostic. These modalities were considered particularly useful to characterize condition in an individual animal may help to reduce the number of animals required on study and Methods EDV ESV 90 adverse effects of molecules in early stages of development or as tools to refine selection of lead EF(%) imaging permits evaluation of functional parameters (e.g. blood flow, oxygen and glucose consumption y = 1.7602x - 54.208 candidates. used (µL) (µL) R² = 0.7366 80 in a tissue) that cannot be measured non-invasively by any other methods. As there are various imaging r=0.86 modalities, we sought to assess which would be best for evaluation of cardiac function in mice: PET-CT or MRI? 70 PET Mean 32.13 14.05 59.00 60

2 Experimental Procedures 50

SDM 7.41 7.68 14.43 PET %EF 40 PET-CT and MRI images of the heart of nine female CD-1 mice were compared; parameters such as 5 Acknowledgements end diastolic volume (EDV), end systolic volume (ESV) and percent ejection fraction (%EF) were 30 recorded. All animals were experimentally naïve, healthy, 6-7 weeks of age and weighed between 23.8 The authors would like to acknowledged the contributions of the technical and scientific staff at CIMS- MRI Mean 60.75 22.25 64.31 20 and 29.1g. MRI and PET-CT scans were performed while under the same anesthesia. MRI was CRCHUS as well as technical and veterinary staff of Charles River Sherbrooke without who, this project performed using a 7 Tesla small-animal scanner equipped with 205/120 Magnex gradient coils and a 63 would not have been possible. mm volume coil (Varian, Palo Alto, CA, USA). ECG-gated images of the heart were acquired using a 10 pulse sequence; series of short-axis cine images covering the left ventricle were acquired. PET-CT was SDM 10.74 7.05 7.04 0 performed using a small-animal PET scanner with a 7.5 cm axial field of view, an isotropic spatial 50 55 60 65 70 75 80 resolution of 1.2 mm, and an energy window setting of 250-650 keV (LabPET/- Triumph; Gamma %EF MRI Medica, Northridge, CA, USA). The CT is integrated within the Triumph PET scanner and was conducted with a 60 kVp energy window, 1 frame 512 projections and a 2 minute acquisition time. A 45 minute dynamic acquisition was initiated immediately followed by the administration via the caudal vein catheter of approximately 20 MBq of 18F-FDG (18F-fluorodeoxyglucose) in 0.15 mL of 0.9% sodium chloride solution at a rate of 0.3 mL/minute.

3 Results

PET heart images MRI heart images (Left End diastolic) MRI heart images (Right End systolic)