Page 155 - Functional impairment and cues for rehabilitation of head and neck cancer patients -

All scans were performed on a 3T Ingenia scanner (Philips Healthcare, Best, The Netherlands) using a dStream head-spine coil for optimal signal to noise ratio and allowing sufficient space to perform the exercises with the SEA. T2-mapping requires in general a time-consuming multi-echo T2W acquisition. Given the direct decrease in T2-value after exercise, we used a k-t-T2 accelerated research software patch (38) to speed-up the acquisition to a little over 4 minutes per scan. The field of view of the multi-slice multi-echo T2-weighted turbo spin-echo sequence was 170 mm in the AP and RL direction and 129 mm in the FH direction. Acquired voxel size was 1.2 x 1.2 mm inplane with a reconstructed voxel size of 0.6 x 0.6 mm, using contiguous slices with a thickness of 3 mm. The 12 echo-times ranged between 16 ms up to 104 ms with increments of 8 ms. The repetition time was 4211 ms. Halfscan is 0.613 and SENSE acceleration factor is 2 in the LR direction. A voxel-wise fit to the T2-decay curve was based on those 12 echo-times, generating a quantitative 3D T2-map over the field of view.
T2-value measurements
The following muscles were included in the field of view: masseter muscles, lateral pterygoid muscles, medial pterygoid muscles, intrinsic tongue muscles, extrinsic tongue muscles (genioglossus muscle), suprahyoid muscles, infrahyoid muscles (thyrohyoid muscle), sternocleidomastoid muscles and superior pharyngeal constrictor muscle. The mean T2- values of these muscles were measured in PACS viewer by means of selecting one region of interest (ROI) per muscle (> 10 mm2), on an axial image at a predetermined height where the muscle is the largest, blinded for exercise type and whether it concerned a scan before or after exercise (Figure 3). Homogeneous T2-values along the entire muscle were assumed, based on published results and our own measurement on a sample of the muscles in this study (39). Larger non-muscular tissues (e.g., blood vessels and fat) were excluded from the ROI as much as possible, although inclusion of non-muscular tissue within the ROI was inevitable since these are embedded within the muscle. Per subject, both the muscles on left and right side were measured. The measurements of the MRI scans before and after all exercise of all subjects were performed by two researchers (one medical doctor and one technical physician) independently. Both researchers received an example MRI scan indicating the anatomical height on which the measurements should be done for each muscle (see Figure 3). The average of the two measurements were used for analyses. Also, in order to compare T2-values in a (control) muscle not used during the exercises, the T2-values in the splenius capitis muscles before and after the cES exercise were measured. This exercise was selected because we expected only after the cES the field of view would contain non-activated muscles.
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Muscle activation during swallowing exercises
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