Proefschrift_vd_Beek

Parameter Manipulations in SOE (eCAP)

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Table 1. A: Patient demographics. B: The numbers of subjects per scanning measure are shown using the forward masking artefact rejection scheme and with the alternating polarity artefact rejection method. For selectivity measures the numbers of subjects are shown where the position of the masker or probe electrode was fixed, and which recording electrode was used relative to the probe electrode.

ng the array, er to investi- ts of the indi- in our study pare the two measure SOE the Advanced t group. More ters that limit xcitation area nd selectivity ording param- obe electrode f the stimulus. he position of probe position ition variable, or alternating or correlation ch perception , using linear

A Patient demographics

Age (years)

35 (average range 1–86) 9.8 (average range 0.1–47)

Duration of deafness (years)

Sex

16 male / 15 female

Child/Adult Implant type

12 C / 19 A

HiRes 90K HiFocus 1J

Aetiology

progressive/congenital (17), meningitis (8), rubella (2), trauma (2),

sudden idiopathic (1) and osteogenesis imperfecta (1)

B Measure

4

Modification

Subjects (n)

Scanning

Forward masking Alternating polarity

29

5

Selectivity

Masker position fixed, recording 2 contacts apical Masker position fixed, recording 2 contacts basal Probe position fixed, recording 2 contacts apical Probe position fixed, recording 2 contacts basal

28

subjects were ’ HiRes 90K ay, which has ics are shown

5

5

5

Raw wave forms are shown in Figure 1, D. The recording electrode contact was set two contacts apical to the fixed masker contact (as Abbas et al, 1999) and in five patients the recording contact was additionally set two contacts basal to the masker. In this subset of five subjects the measurements were repeated with the probe position fixed and the masker position varied. Subjects for all subsets were chosen on the basis of chronological order and included both children and adults. Both selectivity and scanning measures were performed at three points along the array. Measurements were obtained at an apical electrode (EA, electrode 3 or 4), a middle position (EM, electrode 7, 8, or 9), and a basal position (EB, electrode 13, 14, or 15). Additionally, for all methods and electrode contact positions, measurements were performed at three different current levels. The effect of masker and probe levels were compared between the current ranges: low (0.6–0.8 mA), medium (0.9–1.0 mA), and high (1.2 mA). Note that these measurements could only be performed in patients under general anesthesia, as even the “low” level used is in the upper range of the electrical dynamic range found in normal clinical practice M-levels. This is due to an inherent noise limitation of current eCAP recording systems, which do not allow SOE measures to be made at stimulus levels around subjective thresholds. Selectivity easures (Figure 1, B) were obtained by using a tra- ditional forward masking technique as described previously (Cohen et al, 2003). All subjects were tested with the masker contact fixed and eCAP amplitudes measured for different probe electrode posi- tions, which were stimulated after a 500 μ s interval. Raw wave forms are shown in Figure 1, D. The recording electrode contact was set two contacts apical to the fixed mask r contact (as Abb s et l, 1999) and in five patients the recording contact was additionally set two con- tacts basal to the masker. In this subset of five subjects the measure- ments were repeated with the probe position fixed and the masker pos tion varied. Subjects for all subsets we e chosen on the basis of chronological order and included both children and adults. Both selectivity and scanning measures were performed at three points along the array. Measurements were obtained at an apical electrode (EA, electrode 3 or 4), a middle position (EM, electrode 7, 8, or 9), and a basal position (EB, electrode 13, 14, or 15). Addi- tionally, for all m thods and electrode contact positions, m asure- ments were performed at three different current levels. The effect of masker and probe levels were compared between the current ranges: low (0.6–0.8 mA), m dium (0.9–1.0 mA), and high (1.2 mA). Note that these measurements could only be performed in patients under general anesthesia, as even the “low” level used is in the upper range of the electrical dynamic range found in normal clinical practice M-levels. This is due to an inherent noise limitation of current eCAP recording systems, which do not allow SOE measures to be made at stimulus levels around subjective thresholds.

AP measure- ry. Using the software, test for the record- rameters used ic first; pulse μ s, sampling d be observed measurement BEDCS intra- rtant to notice not essentially imulating one t) and record- ions along the d for artefact ating polarity mulating elec- ating polarity ested with the vity measure-

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