4 channel array head coil

fMRI was performed using a 9.4T Agilent horizontal bore scanner (Agilent) as described in detail previously (Wells et al., 2015 (link)). Briefly, a 72 mm inner diameter volume coil was used for transmission and signal was received using a 4-channel array head coil (Rapid Biomedical). To assess T2* weighted BOLD signals the following sequence parameters were used: TR = 5s, TI = 2s, matrix size = 64 × 64, FOV = 35  mm × 35  mm, TE = 10 ms, single slice (slice thickness = 2 mm), inversion pulse bandwidth = 20,000 Hz (Hosford et al., 2018 (link)). BOLD responses in the S1FL region were triggered by electrical stimulation of the contralateral forelimb.

To determine the location and fate of the magnetic particles once they were injected into the brainstem of rats, MRI was performed on the 9.4 T MRI scanner with a 72 mm inner diameter volume coil (RAPID Biomedical) for radiofrequency transmission and a 4‐channel array head coil (RAPID Biomedical) for signal reception. Anesthesia was induced with 4% isoflurane and maintained with 1.5% isoflurane. Body temperature was maintained with a heated waterbed. Respiratory rate and body temperature were monitored with a pneumatic pillow sensor and a rectal thermister probe respectively, both connected to a MR‐compatible monitoring and gating system (SA Instruments). A T₂*‐weighted gradient‐echo sequence was used: TE = 6.5 ms, TR = 2230 ms, flip angle = 56°, number of averages = 5, FOV = 28.8 mm × 28.8 mm, matrix = 192 × 192, slice thickness = 0.15 mm, interslice distance = 0 mm. The images have an isotropic resolution of 150 µm.
Affine registration of the MR images was performed using the NifTK software.^[71]