Spectris solaris

After routine structural MRI acquisition, DCE-MRI of the nasopharynx and upper neck was performed on a 3.0-T MRI system (Achieva; Philips Healthcare). Four acquisitions were obtained in a chronological order with a field of view (FOV) of 22 × 22 × 6 cm (AP × RL × FH): precontrast T₁-weighted fast field echo (FFE) acquisition using a flip angle of 5° (“FA5” acquisition) in 1 minute 22 seconds; T₂-weighted imaging (“T2W” acquisition) in 50 seconds; B1 mapping measurement acquisition (“B1MAP” acquisition) in 1 minute 23 seconds; and DCE acquisition using a flip angle of 15° (“FA15” acquisition) in 6 minutes 47 seconds with 65 dynamic scans. The details of scanning protocols have been described in our previous paper [9 (link)]. All four acquisitions were performed in the same anatomical region and reconstructed to the same resolution. The contrast agent Gd-DOTA (Dotarem, Guerbet, France) was injected intravenously as a bolus into the blood at around the 8th dynamic acquisition using a power injector system (Spectris Solaris, MedRad, USA), immediately followed by a 25-mL saline flush at a rate of 3.5 mL per second. The dose of Gd-DOTA was 0.1 mmol/(kg body weight) for each patient.

MRI examinations were performed by a 3.0-T MR imaging system (Signa; GE Medical Systems, Milwaukee, WI) with a surface phased-array coil (gradient magnet strength of 23 mT/m). Patients were scanned in supine position. Morphologic evaluation of the tumors was performed with following MR sequences: T1-weighted dual-echo image (T1WI) (repetition time [TR] = 260 milliseconds; echo time [TE] = 2.2–2.5 milliseconds, 5.5–5.8 milliseconds; FOV = 36–44 cm; matrix 256 × 192; section thickness 5 mm; gap 1 mm), T2-weighted image (T2WI) (TR = infinite; TE = 90–105 milliseconds; FOV = 36–44 cm; matrix 320 × 224; section thickness 5 mm; gap 1 mm), and 3-dimensional fat-saturated T1-weighted dynamic contrast-enhanced (DCE) image (TR = 3.0–3.9 milliseconds; TE = 1.2–1.6 milliseconds; FOV = 34–40 cm; matrix 288 × 224; section thickness 5 mm; interpolated section thickness −2.5 mm). Gadobenate dimeglumine (Magnevist; Schering, Berlin, Germany) was intravenously injected with a dose of 0.1 mmol (per kilogram of body weight) at a flow rate of 2 mL/s by a power injector (Spectris Solaris; Medrad, Indianola, PA), followed by a 20-mL flush of normal saline. DCE-MRI was performed in transverse plane at arterial phase, venous phase, and delayed phase. Diffusion-weighted imaging (DWI) was performed before DCE-MRI with b values of 0.80 s/mm².

This study involved 4 runs with 80 swallows using the same technique previously published (Humbert et al. 2012). Five milliliters of room‐temperature liquid was infused directly onto the anterior‐mid region of the tongue via plastic tubing that was dispensed by a MR‐safe injector (Spectris Solaris^®, Medrad). Each run consisted of a single swallowing condition with 20 swallows. The four conditions were: distilled water, sour liquid, distilled water with cutaneous electrical stimulation (e‐stim), and distilled water with visual biofeedback of swallowing. The order of the four runs was randomized across participants. Sour water and distilled water were infused with separate tubing to avoid taste contamination. Participants were instructed to swallow once they felt that the liquid had completely entered their mouths and the interstimulus interval was 18 s for all swallows. Task compliance was monitored with an oral pressure system that consisted of a water‐filled tube that extended from the oral cavity to a transducer, which measured fluid displacement with each swallow. This pressure transducer only detects pressure differences in the oral cavity and no pressure changes could be detected by pushing directly on the small tubes in the mouth. To remove any residual sour taste on the tongue, a wash out period followed the taste run.

MR imaging was performed with a 1.5-MR unit at our institution (Signa Excite; GE Healthcare; Milwaukee, WI, USA or Magnetom Avanto; Siemens, Erlangen, Germany). MR imaging protocol comprised the following sequences: axial T2-weighted image with fat saturation, T1-weighted image, gradient echo image (GRE) or multiple-echo data image combination (MEDIC) sequence, and axial/coronal post-contrast T1-weighted image with fat saturation. Post-contrast T1-weigted imaging was performed after injection of a standard dose of 0.1 mmol/kg gadoterate meglumine (Dotarem; Guerbet) at a rate of 1–1.5 mL/sec using an MR imaging–compatible power injector (Spectris Solaris; Medrad). A bolus of contrast material was followed by a 5-mL bolus of saline that was administered at the same injection rate. Post-contrast T1-weighted images were obtained in 2 minutes after injection of contrast materials. Total imaging times were approximately 25 minutes. All infants were sedated using chloral hydrate (30–50 mg/kg body weight) for the MRI examination. Pulse oximetry was performed to continuously monitor arterial hemoglobin oxygen saturation (SpO2) and heart rate. Airway patency was monitored intermittently by specially trained pediatric nurses.