Advantage windows

All MR imaging examinations were performed by using the same 1.5 T MR scanners (Avanto and Aera, Siemens Medical Systems, Erlangen, Germany), with a 12-channel-array head coil. Along with a number of conventional T2- and T1-sequences before and after contrast agent, 3D isotropic T1-weighted image datasets (TR/TE 1300/2.6 ms, voxel size 1 mm³) were acquired after intravenous administration of gadobutrol. Apart from the head and neck MRI studies, patients received whole-body CT imaging with iodinated contrast agent in order to exclude distant disease. Radiological tumour volumetry in the contrast-enhanced 3D T1-weighted images was performed offline by two radiologists in consensus using a dedicated workstation and commercially available software (Advantage Windows, GE Medical Systems, Milwaukee, WI).

The size of CC was determined using the midline sagittal MRI scans. Anterior/genu, posterior/tail, and medium/tail portions of the CC were measured (Figure 1(a)). The CC area was measured manually by drawing a line at the maximal anteroposterior dimension of the CC and another line is drawn perpendicularly at its midpoint (Figure 1(b)) [25 ]. The measurements have been performed on a picture storing system on the workstation Advantage Windows (GE Healthcare) (Figures 1(a) and 1(b)). The CC index was calculated as (1 + 2 + 3)/4 following the method presented by Figueira et al. [26 (link)].

The DWI data were transferred to a workstation (Advantage Windows, software version 2.0, GE Medical Systems). Radiological analysis was performed by the same radiologist. A large circular region of interest (ROI) was placed at the corticomedullary junction for the measurement of ADC values (Figure 1). For each kidney, three ROIs were placed in the middle portion of the kidneys, which are less influenced by the perfusion effect. The mean ADC values for b100, b600, and b1000, with standard deviations, were calculated. ADC maps were calculated automatically with the MR system.

The dual-energy data thus obtained were sent to a computer workstation (Advantage Windows; GE healthcare) and the 5 mm-thick VM image of each phase was reconstructed on the workstation with analytical software for dual-energy data (GSI viewer; GE healthcare). The paired-projection data collected by dual-energy scan were analyzed in terms of the material decomposition process to determine the material density projection after a series of calibrations and corrective steps. A monochromatic energy image could be generated from the weighted sum of material density projections with their corresponding mass attenuation coefficients at a given energy. For any virtual keV between 40 and 140 keV, the object is depicted on the workstation as if imaged with a monochromatic X-ray beam that simulated keV (Wu et al.
2009 (link)). VM images of two different energies (50 keV and 65 keV) were generated as the images that had attenuation properties similar to conventional CT images at 80 kVp and 120 kVp, and conventional CT images at 140kVp were also transferred to the workstation as reference images. As a result, a set of nine images was obtained per patient for one examination: 5-mm thick 140-kVp conventional CT, 65-keV VM and 50-keV VM images for each of the early arterial, late arterial and portal venous phase.

The DW-MRI data were transferred to a workstation (Advantage Windows, software version 2.0, General Electric Medical Systems, Milwaukee, WI, USA). Monoexponential fitting of the diffusion decay curves were utilized. A circular region of interests (ROI) was placed at the corticomedullary junction for the measurement of ADC values in normal and obstructed kidneys. For each kidney, three ROIs were placed in the middle portion (Fig. 1). For each ROI, the mean ADC-values and standard deviations were calculated. All measurements were repeated using different b values (100, 600 and1000 s/mm²). The ADC maps were calculated automatically with the MR-system, and ADC values were expressed in square millimetres per second (mm²/s).