Omniscan

Following the ultrasound procedure, all animals underwent scanning with the 9.4T MRI system (Bruker Medical, Boston, MA). The mice were placed in a birdcage coil (diameter 35 mm), while being anesthetized with 1 - 2% isoflurane and respiration rate was monitored throughout the imaging sessions. MR images were acquired using a contrast-enhanced T1-weighted 2D FLASH sequence (TR/TE 230/3.3 ms, flip angle: 70°, number of excitations: 6, field of view: 25.6 mm × 25.6 mm, resolution 100 μm x 100 μm x 400 μm), 30 min following the intraperitoneal bolus injection of 0.3 ml gadodiamide (GD-DTPA) (Omniscan^TM, GE Healthcare, Princeton, NJ). As previously reported, gadodiamide provides spatial information of the BBB opening by temporally enhancing the MR signal relative to the ultrasound parameters 48 (link). In addition, T2-weighted MRI was performed one day after the sonication to detect any potential damage using a 2D RARE sequence (TR/TE 2500/3.3 ms, echo train: 8, number of excitations: 8, field of view: 25.6 mm × 25.6 mm, resolution 100 μm x 100 μm x 400 μm). The sequences employed in this study have been previously optimized by our group 17 (link).

MR imaging of MDA-MB-435 tumor mice was conducted with a 3.0 T system (Philips, Netherlands) using an animal coil (Philips). During the MRI scans, all animals were anesthetized by inhaled isoflurane (1.5% in O2) at 2.0 LPM. A children’s scalp needle (size: 0.40; KDL Corp., China) was connected to a syringe to deliver gadoteridol (Omniscan^TM, GE Healthcare, Oslo, Norway). The protocol included anatomical MR imaging as follows: a T2-weighted spin echo sequence (RARE) was performed before contrast agent injection with a field of view = 160 × 116 matrix and 40 × 40 × 26 mm, repetition time (TR)/echo time (TE) = 4,000/100 ms. A slice thickness of 2 mm with a 0.2 mm gap was used to cover the tumor region of interest (ROI). A gradient-echo multiflip-angle T1 map was produced before contrast agent injection with a field of view = 200 × 160 matrix, a 40 × 40 × 26 mm, TR/TE = 651/20 ms, NEX = 3, and flip angles of 10, 20, 30, 40, 50, 60, and 70°. A slice thickness of 2 mm with a 0.2 mm gap was used to cover the tumor ROI. The parameters of DCE-MRI were the same as those above, except the fixed flip angle was 30°. After eight baseline image scans, 0.2 ml/kg of gadoteridol (total injection volume, 0.15 ml) was injected (over a period of 15 s), and then 40 images were acquired.

All MR imaging examinations were performed at our institution with the same 3.0-T MR imaging system Skyra (Siemens Healthcare, Erlangen, Germany) and two 8-channel surface radiofrequency receiving coils. The MR imaging protocol included transverse T1-weighted turbo spin echo and transverse T2-weighted turbo spin echo sequences. DW images were acquired prior to gadolinium chelate injection. Finally, a time-resolved MR angiography with Stochastic Trajectories (TWIST) T1-weighted perfusion weighted sequence was repeated 75 times during the whole process of contrast injection with 5 phases of blank scans before the injection of contrast agent. The total of 0.2 mL per kilogram of body weight gadoteric acid (Omniscan TM; General Electric healthcare, USA) had been injected both before and after RF Ablation treatment. The time interval of two injections was over 1 hour to eliminate the residual effects of contrast agent. Protocol details are shown in Table 1.

D1 ORL UVA cells were thawed and centrifuged at 125 × g for 5 min and supernatant was discarded. The cells were resuspended to 10⁵ cells/ml in the culture medium with different Gd-based solutions; Gd-BT-DO3A (Gadavist^®, Bayer), Gd-DTPA (Magnevist^®, Bayer), Gd-DTPA-BMA (Omniscan^TM, GE Healthcare), Gd-DOTA (Dotarem^®,Guerbet) and Gd-BOPTA (Multihance^®, Bracco) at variable concentrations of Gd³⁺ (0, 10, 25, 50, 100 and 200 mM), approximately 50 µl of cell suspension was loaded into the micro-capillary channel and the channel was sealed with Critoseal. The cells were levitated in the magnetic levitation device for 10 min and imaged every 1 min under the inverted microscope (Olympus IX-83). Levitation heights of cells (distance of cells from the bottom surface of micro-capillary channel) were measured with ImageJ Fiji software by performing threshold and particle analysis. In order to determine when cells reached to the equilibrium at a specific levitation height in different paramagnetic solutions, the time point that cells were approaching ±5% of the levitation height reached at 10 min was considered as equilibrium time. The levitation heights of D1 ORL UVA^eGFP and MDA-MB-231^dsRed cells in the medium containing 100 mM Gd-BT-DO3A were also measured by the same method.

Breast MRI images were obtained by a 3.0T scanner (Skyra, Siemens Healthcare, Erlangen, Germany) using a dedicated 16-channel phased-array breast coil in the prone position. T1-weighted DCE-MRI images were analyzed in this study, using a TWIST-VIBE sequence: repetition time (TR) 5.24 ms, echo time (TE) 2.46 ms, matrix size 182 x 320, slice thickness 1.5 mm, FOV 260 x 320 mm2, flip angle 10°, temporal resolution 5.94 sec/phase, and the total scan time 5min57sec. The contrast medium (Omniscan, GE Healthcare, Milwaukee, WI) was injected at the end of the third acquisition phase with a dose of 0.1 mmol/kg body weight, then followed by a 20 ml saline flush at a rate of 2.5 mL/s.

MRI examination was performed by using 3.0 T Philips Health care MRI scanners with 8-channel breast dedicated coils. Patients were maintained in the prone position, and the bilateral breasts naturally and symmetrically fell into the coil. All patients were asked to reduce their respiratory rate to avoid motion artifacts caused by breathing and the heart beating. The contrast agent (Gd-DTPA, 0.1 mmol/kg, Omniscan, GE Healthcare) was injected intravenously at a rate of 2.5 ml/s. Then, 20 ml saline was injected at the same rate to flush out the residual contrast agent. A total of 9 phases were scanned without intervals, and the first phase involved plain scanning. After intravenous injection, continuous noninterval scans were performed in 8 phases. The scan time for each phase was 58 s. The DCE-MRI sequences were acquired using a VIBRANT multiphase sequence as follows: TR/TE: 3.8/1.6 ms, FOV: 300 × 300 mm2, matrix size: 512 × 512, silence thickness: 1.5 mm. The second phase of dynamic contrast enhancement was selected as the object of image segmentation because the peak value of enhancement in the lesion area occurs within 60–120 s after injection of contrast agent [24 (link)].