Inova unity system

MRI studies were performed using a 4.7T horizontal bore magnet or a 9.4T vertical bore magnet equipped with a Varian INOVA Unity system (Palo Alto, CA, United States). T₁ and T₂ (or T₂^*) maps were acquired using a spin echo (or gradient echo) sequence with varying repetition times (TRs) or echo times (TEs), respectively. The raw data were acquired using a centric k-space reordering scheme, followed by the phase encoding steps with higher phase encoding gradient amplitudes. Data acquisition parameters of the FLASH readout were TR/TE/Flip angle = 10 ms/5 ms/10°. The standard multi-echo Carr–Purcell–Meiboom–Gill pulse sequence was used for measuring T₂ from a single echo train. The T₂ and T₂^* maps were obtained on a voxel-by-voxel basis using a nonlinear least-squares fit equation M = M₀e^−TE/T2 from the images taken at each echo time. Images were reconstructed and analyzed by using MatLab (MathWorks, Natick, MA).

BLI was initiated for monitoring intracranial tumor growth 7 days after tumor implantation using the IVIS Spectrum system (Caliper, Xenogen, Alameda, CA). The tumor bearing mice (n = 6) were anesthetized (isoflurane/O₂ in an induction chamber; isoflurane from Baxter International Inc., Deerfield, IL) and a solution of D-luciferin (120 mg/kg in PBS in a total volume of 80 ml; Biosynthesis, Naperville, IL) was administered s.c. in the neck region. Anesthesia was maintained with isoflurane (2%) in oxygen. Five minutes after luciferin injection, an array of various exposure times was applied for image acquisition. Data were quantified with the Living Imaging software by using absolute photon counts (photons/s) in an ROI, manually drawn to outline the BLI signal of the brain. Once a BLI signal was observed, MRI was performed to assess tumor volume and follow up its growth by using a 9.4 T horizontal bore magnet with a Varian INOVA Unity system (Palo Alto, CA). Each mouse was maintained under general anesthesia (2% isoflurane) during the scan. Fast spin echo multi-slice (FSEMS) sequence was applied (TR = 2500 ms, TE =100 ms, slice thickness = 1 mm, number of slice = 10, matrix = 256 × 256, field of view = 20 × 20 mm and average = 4) to acquire T₂-weighted images.