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3.3.5 PpIX fluorescence patterns in different diagnoses
The fluorescence patterns of the lesions were analysed with respect to the skin structure. The findings agree with the previous reports27,24,32,39,18 that in some patients the fluorescence develops over an area of the visible tumours forming a rim at the margins (
Figure 3.9
). Sometimes it spreads outside the visible tumour or develops in areas without any evidence of the diseased skin to the naked eye which may be an indication of early stages malignant changes. There findings support the studies showing that PpIX fluorescence is an effective method for detecting pre-clinical diseased skin and assisting with identifying tumours’ margins for the surgery27,24,32.3.3.5 PpIX fluorescence patterns in different diagnoses
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Figure 3.9:
Biopsy confirmed BCC lesion of P010 patient administered Metvix® PDT.a
–
a white light image of the tumour taken by a medical photographer.b –
a monochromatic image of the tumour taken by the camera under 405 nm illumination. A half of the image is overlapped with a semi-transparent fluorescence image on a false colour scale taken at 180 min from the application of the cream. It shows that the shape of the lesion is similar to the developed fluorescence pattern. Although, the fluorescence area is larger than the visible tumour; and there is a rim at the margins which may be an indicator of early stages malignancies.c, e –
a monochromatic image and a false colour image of PpIX fluorescence at 180 min from the application of the cream. The red dashed rectangle shows an area on the tumour with the highest PpIX metabolism. This area was used in the time course calculations of peak fluorescence.d –
a false colour fluorescence image taken at 60 min from the application of the cream. The fluorescence starts to develop over the area within the visible tumour and then spreads to the area outwith the tumour.The fluorescence time course was analysed by integrating regions of interest (ROIs) which developed the strongest fluorescence. The red dashed line in
Figure 3.9
(e) shows such a ROI. The size of the ROIs varied depending on the size of the uniform peak fluorescence region. The smallest ROI was 25 x 38 pixels for P004 subject and the largest was 73 x 86 pixels for P013.Another example was patient P005 who had two AK lesions treated with Metvix® PDT. The lesions were located on the same foot close to each other; they were similar in shape and size and threated on the same day. Lesion #1 developed almost twice as much PpIX fluorescence over the area corresponding to the lesion compared to only partial fluorescence at the lesion #4 (
Figure 3.10
). The intensity of the fluorescence was also lower in lesion #1. The fluorescence distribution in lesion #4 showed the formation of two halves which may suggest that there were two centres of the malignant growth which merged together in one lesion.3.3.5 PpIX fluorescence patterns in different diagnoses
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Figure 3.10:
Two AK lesions of subject P005 subject who was administered Metvix® PDT. The lesions were located on the same foot; they were similar in shape and size and treated on the same day. However, the fluorescence from the left lesion (marked as #4 on the image) is almost twice as high and larger in area than the fluorescence from the lesion on the right, marked as #1 on the image.a, b –
a monochromatic and a false colour fluorescence image of lesion #4 taken at 180 min after the application of the cream.c –
a white light image taken by a medical photographer.d, e –
a monochromatic and a false colour fluorescence image of lesion #1 taken at 180 min after the application of the cream. Although the fluorescence was much higher in one lesion than in the other the pain after the treatment was evaluated as the same.Surprisingly the pain experienced during PDT was the same for both lesions. Another interesting finding was that both lesions were clear at 3 month follow up. This supports the reports that PpIX fluorescence does not always correlate with PDT outcomes, the fluorescence can be poor yet there is a response to PDT or vice versa22,25.
Fluorescence imaging becomes more challenging in the cases of crusted and eroded lesions, and when there is any bleeding after the curettage.
Figure 3.11
shows the fluorescence of a crusted AK lesion treated with Ameluz gel which was bleeding after the preparation. Crust and blood blocked some of the fluorescence signal. However, it was still possible to select areas with a clear surface for the analysis. In this case the fluorescence spreads beyond the visible lesion (Figure 3.11
, c) and it grows with different speeds over different regions (Figure 3.11
, d).3.3.5 PpIX fluorescence patterns in different diagnoses
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Figure 3.11:
AK lesion of P011 subject administered Ameluz PDT. The surface of thelesion was crusted and there was some bleeding after the curettage. The crust, erosion and bleeding can block some of the fluorescence signal and make the imaging mode difficult. However, it was still possible to analyse the fluorescence in the clear surface around the crusted and bleeding part.
a –
a white light medical image of the lesion.b –
a monochromatic image of the lesion taken with the camera under 405 nm illumination. The size of the images taken with the camera were cropped from 640x480 pixels (3.1 mm x 2.4 mm) to 540x380 pixels corresponding to 2.6 mm x 1.9 mm to remove the reference contour used for the alignment.c –
a false colour fluorescence image taken with the camera at 180 min after the application of the gel.d –
PpIX fluorescence time course was integrated over different regions on the image. The black line shows fluorescence integrated over the whole image, three different areas correspond to the areas on the fluorescent image (c).The fluorescence develops with different speeds over different areas.There was a case with a blurred fluorescence pattern in a BCC tumour treated with Metvix® PDT (
Figure 3.12
). The margins of the tumour were not clear and it developed a random spotted pattern which did not correlate to the lesion or the skin. Dense sebaceous glands on the neck could be one of the explanations of such patterns. Treating this tumour with PDT would be the best choice as surgery would be quite challenging.3.3.5 PpIX fluorescence patterns in different diagnoses
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Figure 3.12:
Biopsy confirmed BCC tumour of P008 patient administered Metvix® PDT.a –
a white light medical image of the tumour.b –
a fluorescence image taken with a colour digital camera under Wood’s lamp.c –
a monochromatic image of the tumour taken with the camera under 405 nm illumination.d –
a monochromatic fluorescence images taken with the camera at 180 min after the application of the cream. The margins of the tumour are not very clear to the naked eye; the fluorescence has blurred random spotted pattern which may be caused by the activity of sebaceous glands which are quite dense on the neck.Fluorescence homogeneity was calculated in the ROIs and over the whole image at 180 min from the application of the creams. The fluorescence value and pixel indices for local minimum and local maximum for ROI and global minimum and global maximum for the whole image were identified. In order to reduce numerical noise 5 pixel values were averaged at the minima and maximuma. The homogeneity was calculated as 1-({global, local} max- {global, local} min) / local_mean, %.
On average for 12 patients the fluorescence of the lesion was homogeneous with more than 75 % homogeneity in the ROIs; and for one patient it was heterogeneous with homogeneity equal to 25 %. Over the whole image the fluorescence was heterogeneous with homogeneity less than 21 % on average for 12 patients which indicated the contrast between the peak fluorescence in ROI and the rest of the image including healthy parts of the skin in cases for well-defined fluorescence patterns; the fluorescence was 54 % homogeneous for one patient with poorly defined weak fluorescence.
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