Omniscan

All MR angiography was performed with the 1.5 T MRI system (Sonata, Siemens HealthCare, Erlangen Germany) using a 8-channel neurovascular array coil (Siemens HealthCare, Erlangen Germany). The parameters were as follows: Field of view, 39 cm; TR/TE, 4.3/1.31 ms; flip angle, 30°; matrix, 202 x 384; number of average, 1; section thickness, 1mm; no interslice gap. A total of 72 slices were acquired and the acquisition time was 17 seconds. A bolus of 15 ml of gadodiamide at a concentration of 0.5 mmol/ml (Omniscan, Nycomed, Princeton, NJ) was injected at 2 ml/s with a flush of 15 ml of saline at the same rate, using a power injector (Medras, Medrad, Indianola, PA). Two phases of pre-contrast and arterial phase were obtained. And, only the arterial phase images were displayed on picture archiving and communication system (PACS), using 3D maximum-intensity-projection (MIP) reconstruction.

For more precise in vivo evaluation of intracranial metastases formation, cranial MRI (cMRI, 9.4 T, Bruker Topspin 9/20) after Gadolinium contrast administration was performed on day 26 after intracardial tumor cell injection. Mice were sedated with 3% isoflurane and kept under anesthesia at 0.5–1.5%. Constant body temperature was maintained at 37 °C by a heating plate. During imaging respiration was surveilled using an external breathing surface pad (in house development, LabVIEW program, National Instruments Corporation). A dose of 0.2 mmol/kg i.v. gadodiamide (Omniscan; Nycomed) was given to each animal and standard T1-w and T2-w images were acquired. For quantification of tumor volumes, tumors were manually segmented on T1-w images using the Fiji software (general public license) [28 (link)].

In our study, all subjects were recruited from The First Affiliated Hospital, Sun Yat-sen University. DCE-MRI was performed on a 3.0-T system (Magnetom Trio, Siemens) with field of view (FOV) of 22 × 22 × 6 cm (AP × RL × FH), a flip angle of 15°, and scanning time of 6 minute 47 seconds with 65 dynamic scans, 5.9 seconds per scan. The contrast agent gadodiamide Gd-DTPA (Omniscan; Nycomed, Oslo, Norway) was injected intravenously as a bolus into the blood at around the 8th dynamic acquisition using a power injector system (Spectris; Medrad, Indianola, Pennsylvania), immediately followed by a 25-mL saline flush at a rate of 3.5 mL per second. The dose of Gd-DTPA was 0.1 mmol/(kg body weight) for each patient. The reconstructed DCE-MRI images were a 4D matrix (144 × 144 × 20 × 65) with 20 slices.
One hundred and twenty samples of DCE-MRI images containing the HNC tumor lesions were used as our database. Each sample was the DCE-MRI time series of a slice and thus was a 144 × 144 × 65 matrix. Eighty samples were selected randomly as the training dataset while the remaining 40 samples were the testing dataset to verify the accuracy of segmentation.