Compresor

Sample data has been presented as means (+/- standard deviation). Within the thermal imaging experiment, a comparison between temperature rise and temperature fall between all patient groups was performed by one way ANOVA method. If the normality test failed, then a Dunnett test was performed which is a one way ANOVA on ranks with a selected control. If the normality test passed, then analysis was performed using a Tukey test, which is a pairwise multiple comparison procedure. Analysis of potential correlation between depth o f hair shaft damage and depth of p53 expression was performed using the Spearman's rank correlation.

In the laser/skin penetration experiment, comparisons between the energy levels recorded for each fluence of exposure were made for each single skin sample using the one way ANOVA method. However as the thicknesses of the skin samples taken from each patient specimen using the dermatome or scissors varied, a comparison between the samples from each patient specimen was not performed as it was deemed to be too inaccurate. All analyses were performed using SigmaStat™ statistics software, version 1.0 (Jandel Corporation).

3.5 RESULTS

3.5.1 Thermal Imaging Experiment

Thermal Imaging

Thermal imaging of ex vivo, hair-bearing skin revealed heat production at the site of the follicles alone when the specimen was exposed to a single pulse o f 15 J/cm^ from the NMRL (Figure 3.1). Figure 3.1a shows a photograph o f the dermal aspect of a representative specimen of hair-bearing skin and Figure 3.1b is the thermal image taken of this specimen immediately upon irradiation (as demonstrated by the black edge visible at the top of the circular image showing that the camera was scanning at the moment of irradiation). Figure 3.1c is an image taken at approxiniately 0.75

Hair A 1 (probable site) Hair B 1 Hair B 2 Hair B3 Hair C l Hair C 2 Hair A 2 Hair A 3 C l= 43.23 0 C 2= 48.57 * A 3= 40.81 Figure 3.1:

a: Dermal aspect of a specimen from patient 3 after microdissection revealing the hair bulbs and lower hair shafts (xlO). The outlined areas have identified the groups of hairs shown in the thermal image in Figure b.

b: The first thermal image of the specimen in Figure a taken during ruby laser exposure at 15 J/cm^ and showing the peak temperatures in Centigrade obtained by the identified hairs in Figure a (x8.5).

c: A thermal image recorded at approximately 0.75 seconds after ruby laser exposure showing a reduction in temperature at the sites of the hair follicles but an increase in temperature within the intervening skin (x8.5).

Chapter 3 - The Interaction between a Laser Pulse and Human Skin

seconds after laser exposure. The temperatures of the hair follicles recorded by the camera immediately upon laser irradiation (Figure 3.1b) varied between 2T C and 52®C, which is a temperature rise o f between T C and 32®C above the background temperature of 20°C. This heterogeneous rise in temperature seen between hair follicles within the same treatment area was observed in all the samples tested. This phenomenon, from a representative skin specimen, is more clearly illustrated in Figure 3.2. Here, a line has been drawn across the thermal image which bisects a number of different hair follicles (Figure 3.2a). The temperature recorded at each pixel along the line is then plotted in Figure 3.2b over time. The range of temperature rises for all hairs (n=80) from all patient specimens was between 2°C and 32°C with the commonest being between 5°C and 10®C (Figure 3.3). When the temperature rises were grouped according to patient (Figure 3.4), four o f the five patients had a mean temperature rise of 9°C, whilst the remaining patient had a mean temperature rise of 18®C. Statistical analysis using a one way ANOVA method revealed that differences in the median values of the follicular temperature rises between the patients were significantly different (p<0.001).

Thermal imaging revealed that the high temperatures recorded in the hair follicles reduced over time (compare Figures 3.1b and c and see Figure 3.2b) so that most hairs had virtually lost the temperature gain by two seconds after exposure. In comparison, the temperatures recorded at the intervening skin between follicles rose over time so that the greatest temperatures measured at these sites was achieved when the heat had almost completely dissipated from the follicles. When the rate o f temperature change of a particular follicle and its surrounding skin was represented on the same graph (Figure 3.5), it showed that the respective temperature curves would converge and occasionally cross so that the skin could ultimately achieve a greater temperature than that individual follicle. This temperature was often then maintained for the remainder of the recording (approximately 45 seconds) and was noted to be higher than the original starting temperature by between 1°C and 5°C for all specimens examined.

The laser irradiated hair follicles showed a rate of heat dissipation that appeared to be different for each individual follicle within the same treatment site on each patient

55 n 0 sec 0.60 sec 0.75 sec 1.50 sec A2 0.15 sec 0.30 sec 50- — 0.45 se c 7.80 sec 45- A3 U 40- 3 2 35- 30- 25- Resting Temperature 20- 50 60 70 10 20 30 40 0 Pixel Number b.

Figure 3.2a: The first thermal image as shown in Figure 3.1h hut with an arrow across three hairs (Al, A2 and A3) depicting the pixels along which the tem perature changes were recorded over time.

3.2h: Graphical representation of the changes in tem perature over time recorded hy each of the pixels along the arrow shown in (a). Hairs A l, A2 and A3 have been identified and the increase in the pixel num ber follows the direction of the arrow.

Chapter 3 - The Interaction between a Laser Pulse and Human Skin X 35 30 25 20 15 10 5 0 4---1---1---1---1---1--- Oto 5 5.1 to 10 10.1 to 1 5 15.1 to 20 20.1 to 25 25.1 to 30 30.1 to 35 Temperature R ange (C)

Figure 3.3: G raph showing the distribution of maximum tem perature rise recorded for each hair (N=80) measured from all patients. The commonest tem perature rise occurred between 5.1 and 10“C.

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