Directdrive console

MR thermometry was performed to noninvasively image FUS-induced temperature rise in the mouse brain in vivo. The FUS transducer used in the above experiment was integrated with a 4.7 T small animal MRI scanner (Agilent/Varian DirectDrive Console). Eight mice were used for measuring the temperature rise associated with the FUS sonication: n=4 for the mechanical group (a total of 20 repeated temperature measurements for each FUS intensity level) and n=4 for the mechanothermal group (a total of 10 repeated temperature measurements for each FUS intensity level). MR thermometry images were acquired in synchronization with FUS stimulation using a continuously applied gradient-echo imaging sequence with a flip angle of 20 degrees, repetition time of 10 ms, echo time of 4 ms, slice thickness of 1.5 mm, and matrix size of 128×128 for 60×60 mm² field of view. Acquired images were processed using ThermoGuide software (Image Guided Therapy, Pessac, France) to obtain the temperature maps. A circle of 1.7 mm in diameter, which matched the lateral FWHM dimension of the FUS, was drawn on the MR thermometry image. The mean temperature within the circle was calculated at each time point for each FUS sonication.

MRI was performed using a 4.7 T 50 cm horizontal bore MR Spectrometer equipped with a 30 cm ID gauss/cm and a 12 cm ID gauss/cm gradient tube and interfaced to a Varian DirectDrive console. T₂*-weighted MR images were acquired using a multi-gradient echo multi-slice sequence with a 35 mm coil under the following parameters: TR = 1000 ms, TI = 60 ms, NA = 3, FA = 90 degrees, number of echoes = 8, slice thickness = 1 mm, imaging matrix = 128 × 128 and FOV = 30 × 30 mm. TE values were chosen between 3.3 and 26.4 ms (with an interval of 3.3 ms). Post-contrast images of the tumor-bearing mice were acquired 24 hours after injection using the same imaging parameters as the pre-contrast images. Throughout the experiment, the respiratory rate of the mice was monitored and their body temperature was maintained at 37°C. Color coded R₂ maps were generated from the MR images acquired with the above sequence using a custom written MATLAB program for pixel-wise curve fitting of the T₂ relaxation times. The first four echo times from 3.3 ms to 13.2 ms were chosen to construct the maps. Mean R₂ values were computed by averaging pixels within the tumor ROI for each mouse (three tumor slices per mouse). Squared correlation coefficient was also calculated to examine the quality of curve fitting for each pixel across the tumor regions. Results at each time point are presented as mean ± SD.

Both before and 48 hours after intravenous administration of GSMs to mice with sufficiently large GBM brain tumors, CT and MRI imaging were performed to visualize the tumor and assess whether enough GSMs had accumulated to serve as an effective contrast agent for both imaging modalities. The Small Animal Radiation Research Platform was used for CT imaging. Mice anesthetized with a mixture of ketamine and xylazine (140 and 10 mg/kg, respectively) were imaged using a 50 kVp potential (0.5 mA).
MRI was performed using the Small Animal Imaging Facility at the University of Pennsylvania, on a 9.4 T 31 cm horizontal bore MR Spectrometer equipped with a 21 cm ID gauss/cm and a 12 cm ID gauss/cm gradient tube and interfaced to a Varian DirectDrive console. T2 weighted imaging was conducted using a 25 mm coil, with TE and TR times of 2 s and 80 ms, respectively. Throughout the experiment, anesthesia was maintained on 100% oxygen and 1–2% isoflurane while monitoring respiratory rate and maintaining 37 °C body temperature.