We observed no significant difference between the average two-point threshold values before and after iFU testing or between the first and second sessions. Also, we did not observe any statistically significant differences for the 50% and 90% threshold intensity value of iFU between the first and the second sessions; we therefore combined the two sessions’ worth of results for subsequent analysis. Moreover, the pre- and post-test questionnaire showed no psychological or physiological changes associated with the testing process. Out of 34 test subjects, five of them reported transient pain, generally once per testing period. The vast majority of sensations (>99%) were pain free, however, with the median pain score measuring NRS 1/10. None of the subjects complained about any longlasting effects.
Due to time constraints, 25 of 34 tests were able to reach the 90% threshold intensity value of iFU. The average intensity for the attainment of the 90% threshold value for those members who did attain a threshold was 106.4 +/− 58.7 W/cm2. All subjects reached a sensitivity value of 50% within the time provided. The average value of iFU intensity at 50% sensitivity was 95 +/− 69.7 W/cm2. shows the graph of the entire population’s sensitivity data related to iFU intensity. The dip in sensitivity in the range of 170–230 W/cm2 arose due to data dropout, as we stopped collecting data from test subjects when the criteria described above were met. Therefore, successive data points on the graph contain contributions from fewer and fewer subjects, with the first data points coming from the entire test cohort and the final data point at 410 W/cm2 contributed from one test subject. shows an example of the sensitivity versus intensity from two separate subjects, where one test subject reached their 90% sensitivity value at a smaller value of iFU intensity than the other test subject. The specificity of subjects’ response to iFU testing remained high throughout the entire process with an average value of 94% (a 6% false positive rate).
Figure 4 A plot of the test subjects’ sensitivity as a function of intense focused ultrasound (iFU) intensity value. The drop in sensitivity at 170 W/cm2 is due to a reduction in available data for plotting, itself caused by our cessation of data collection (more ...)
Figure 5 A plot showing the sensitivity versus the intensity values of our stimulating intense focused ultrasound (iFU), here for two of our test subjects. The first reached the 90% threshold for sensitivity at relatively low values of iFU intensity. The second (more ...)
shows the subject population’s attainment of sensitivity threshold values versus iFU intensity, for 50% and 90% sensitivity, in the format of a Kaplan-Meyer curve (Sheean et al., 2011
). In both cases, the majority of test subjects reached a given sensitivity threshold value below 100 W/cm2
Figure 6 A curve plotting how a given population reaches both a 90% as well as a 50% threshold as a function of intense focused ultrasound (iFU) intensity. All test subjects reached a value of 50% sensitivity while seventy percent of our test subjects reached (more ...)
Our group of 17 subjects and 34 tests achieved an average two-point discriminant value of 2.83mm +/− 0.79, meaning that on average, the test subjects could identify a set of two prongs as actually consisting of two prongs when the average distance between the prongs was 2.83mm. demonstrates that there exists a statistically significant relationship between iFU threshold and twopoint discriminant value for each of 50% and 90% sensitivity threshold values. In essence, those with a low density of mechanoreceptors (therefore a relatively large distance between the prongs on the two-point DISK-CRIMINATOR™) required a relatively large amount of stimulation by iFU to reliably discern that stimulation. In contrast, those with a high density of mechanoreceptors (a relatively small distance between the prongs) required a relatively small amount of stimulation by iFU to reliably discern that stimulation.
Figure 7 A statistically significant correlation exists between the intense focused ultrasound (iFU) intensity required for our test subjects to achieve each of a 90% and 50% sensitivity threshold value and the two-point assay of their density of peripheral nerve (more ...)