New method of staging of Neuropathic foot due to Hansen's disease using foot pressure image signal processing and early detection of foot at risk of plantar ulcers Presented by Nizar Hussain. M Department of Mechanical Engineering T.K.M. College of Engineering Kollam – 5.

TOPICS INTRODUCTION OBJECTIVES METHODS RESULTS AND DISCUSSIONS SUMMARY OF WORKDONE CONCLUSIONS

Leprosy, a disease as old as mankind, has been a public health problem to many developing countries, including India. About 6,80,000 new cases were detected during 1999 and at the beginning of 2000, 6,41,091 cases were registred for treatment and 6,78,758 cases were newly detected in the world as reported by 91 countries as per WHO. INTRODUCTION

1 to 2 million people are permanently disabled due to Hansen’s disease world wide. It is estimated that about 2.5 million additional leprosy patients will be detected in the period (WHO, 2001)

Sites of deformities of Leprosy +++ SiteFaceHandsFeet Specific Paralytic Neuropa thic +++

Deformities due to Leprosy

The bones of the left foot (a) medial view and (b) lateral view

The muscles of the foot (a) dorsal view, (b) medial view and (c) lateral view

To analyse the spatial distribution of walking foot pressure images of leprotic feet using a new parameter, PR (ratio of power in higher spatial frequency components to the total power in the power spectrum of the foot pressure image) and to calculate the patterns of variation of this parameter in specified standard foot sole areas of leprosy subjects in different stages of progress of the leprosy disease. OBJECTIVES

To use the new parameter, PR to quantify the different stages of the progress of the leprosy disease. To use the new parameter in distinguishing and classifying leprosy subjects in different stages of progress of leprosy disease so as to help the Orthopaedic surgeons in detecting the early stages of leprosy and thereby in taking early corrective action to arrest the progress of the disease as well as the functional rehabilitation of the leprosy feet in time.

Classification of Subjects 1.Normal subjects 2.Normal leprosy 3.Insensitive 4.Insensitive and Claw toes 5.Insensitive, Claw toes and Foot drop 6.Insensitive, Claw toes and Early bone changes 7.Insensitive, Claw toes Foot drop and Early bone changes 8.Insensitive, Claw toes and Advanced bone changes

METHODS

Variations of maximum force, area of foot contact and foot pressures in each frame of walking for a leprosy subject (Left foot - normal leprosy, Right foot - insensitive, clawtoes and foot drop) for two consecutive footprints.

Combined image of the maximum foot pressures developed during walking cycle for the same leprosy subject for two consecutive footprints.

Discrete walking light intensity (pseudo-colour) patterns of a leprosy subject (Left foot - normal leprosy, Right foot - insensittive, clawtoes and foot drop) showing distinct phases of heel–strike, mid–stance and push–off.

The walking foot pressure images are converted to Bitmap files (BMP) for image processing The foot pressure images are divided into ten standard areas using Graphics Workshop software Analysis of Walking foot pressure images

Each foot area has a distribution of pressure in the image. The spatial frequencies and their distributions in the images are analysed by performing 2-D Discrete Fourier Transform (DFT) using MATLAB 5.1 The number of samples M and N in a particular foot sole area depend on the size of the particular area of the foot. The Fourier spectrum F(u,v) of an image f(x,y) corresponding to a foot area is given as where u and v are the spatial frequencies in cycles per distance or cycles per pixel.

The Fourier Spectrum, F(u,v) of an image showing the higher and lower spatial frequency regions.

The total power TP in each area of the foot image is obtained by squaring the magnitudes of the Fourier spectrum given as The low frequency power in the image is given by

The high frequency power is given as: The parameter PR is calculated as

RESULTS AND DISCUSSIONS

The walking foot pressure image intensity (spatial) distributions; the directions of x and y axes are from medial to lateral and posterior to anterior side respectively for a normal subject Distance y (in pixels) Image size = ( 14 x 13 ) pixel Pixel size = (0.196 cm x cm) Distance x (in pixels) f(x,y) (Volt)

The power spectrum after deleting the DC component, in area 8 for a normal subject Freq. v (cycles per pixel) Power Spectrum; LFP = 3.16e+003 HFP = 731 PR = 18.8 Freq. u (cycles per pixel)  F(u, v)  2 (Volt) 2

The walking foot pressure image intensity (spatial) distributions; the directions of x and y axes are from medial to lateral and posterior to anterior side respectively, in area 8 of the right foot of a leprotic subject with insensitive feet

The power spectrum after deleting the DC component, in area 8 of the right foot for a leprotic subject with insensitive feet

The walking foot pressure image intensity (spatial) distributions; the directions of x and y axes are from medial to lateral and posterior to anterior side, respectively in area 8 for a leprosy subject with insensitive and claw toes f(x,y) Volt Distance y (in pixels) Image size = ( 9 x 9 ) pixel Pixel size = (0.308 cm x cm) Distance x (in pixels)

The power spectrum after deleting the DC component, in area 8 of the right foot for a leprotic subject with insensitive and claw toes Freq. v (cycles per pixel) Power Spectrum; LFP = 208 HFP = 167 PR = 44.5 Freq. u (cycles per pixel)  F(u,v)  2 (Volt) 2

The walking foot pressure image intensity (spatial) distributions; the directions of x and y axes are from medial to lateral and posterior to anterior side, respectively in area 8 of the right foot for a leprotic subject (insensitive, claw toes, foot drop and early bone changes) Distance y (in pixels) Image size = ( 8 x 10 ) pixel Pixel size = (0.308 cmx cm) Distance x (in pixels) f(x,y) Volt

The power spectrum after deleting the DC component, in area 8 of the right foot for a leprotic subject (insensitive, claw toes, foot drop and early bone changes) Freq. v (cycles per pixel) Power Spectrum; LFP = 294 HFP = 499 PR = 62.9 Freq. u (cycles per pixel)  F(u,v)  2 (Volt) 2

Comparison of mean values of PR between Normal and Leprotic subjects from Walking foot pressure images

Foot type Foot area Normal n= (1.1) [22] 17.6 (1.5) [22] 17.3 (2.3) [22] 17.4 (1.1) [22] 16.5 (2.1) [22] 16.6 (1.8) [22] 17.3 (1.89) [22] 17.6 (1.9) [22] 17.5 (2.2) [22] Normal leprosy n= (2.21) [12] (2.60) [14] (2.24) [12] (5.3) [13] (4.57) [15] 26.6 (4.90) [15] (2.54) [11] (2.56) [10] (2.92) [11] Insensitive n= (6.6) [9] (4.96) [9] (7.00) [8] (6.77) [9] (8.27) [10] (6.86) [10] (9.39) [7] (9.53) [6] (3.32) [6] Insensitive and Claw toes n= (6.69) [15] (6.45) [15] (7.6) [11] (5.97) [14] (3.43) [14] (4.96) [14] (8.51) [13] (7.94) [10] (9.39) [10] Comparison of mean values of PR between Normal and Leprotic subjects

Contd……. Comparison of mean values of PR between Normal and Leprotic subjects Insensitive, Claw toes and Foot drop n= (6.36) [10] (7.41) [10] (6.4) [9] (7.93) [10] (6.17) [9] (5.67) [8] (1.96) [7] (2.63) [7] (3.04) [7] Insensitive, Claw toes and Early bone changes n= (7.31) [4] (5.13) [4] (5.68) [4] (3.05) [5] (2.09) [5] (4.50) [5] (0.14) [2] (0.21) [3] (0.82) [4] Insensitive, Claw toes, Foot drop and Early bone changes n= (3.03) [3] (0.58) [3] (0.00) [1] (1.77) [3] (0.39) [2] (2.9) [3] (0.90) [3] (1.56) [2] (1.63) [2] Insensitive, Claw toes and Advanced bone changes n= (0.88) [2] (3.52) [3] (1.78) [3] (3.31) [3] (1.55) [3] (3.58) [3] (0.00) [1] (1.03) [2] (3.61) [2] Foot type Foot area Normal n= (1.1) [22] 17.6 (1.5) [22] 17.3 (2.3) [22] 17.4 (1.1) [22] 16.5 (2.1) [22] 16.6 (1.8) [22] 17.3 (1.89) [22] 17.6 (1.9) [22] 17.5 (2.2) [22] 1. The Student’s t - test ‘p’ values are found to be p < for all the areas.

Variation of mean values of PR in different areas of the foot with levels of leprosy for normal and leprotic subjects from walking foot pressure image analysis.

Bar chart showing the percentage increase in mean values of PR with respect to normal for leprotic feet in different levels of leprosy in different areas of the foot from walking foot pressure image analysis.

Comparison of mean values of PR between normal leprosy Vs other higher stages of progress of leprosy insensitive and claw toes Vs other higher stages of progress of leprosy insensitive, claw toes and foot drop Vs other higher stages of progress of leprosy insensitive, claw toes and early bone changes Vs other higher stages of progress of leprosy

It is observed that the mean values of parameter, PR are able to clearly distinguish Normal subjects from Leprosy subjects (p < ). Normal leprosy from higher stages of progress of disease. (p < 0.05 – ) Leprosy with insensitive feet from higher stages of progress of disease. (p < 0.05 – ) Leprosy with insensitive feet and claw toes from higher stages of progress of disease. (p < 0.05 – ) Leprosy with insensitive feet, claw toes and foot drop from higher stages of progress of disease. (p < 0.05 – )

Except in all toes, it is difficult to distinguish the leprosy subjects with insensitive feet, claw toes and early bone changes from leprosy subjects with insensitive feet, claw toes, foot drop and advanced bone changes by using the parameter, PR. (small sample size ‘n’)

Comparison of PR values with standard deviation between Normal and Leprotic subjects

Variation of PR (with standard deviation) in different areas of the foot with four levels of leprosy for normal and leprotic subjects from walking foot pressure image analysis.

Variation of PR (with standard deviation) in different areas of the foot with three levels of leprosy for normal and leprotic subjects from walking foot pressure image analysis.

Correlation between PR and Levels of leprosy

Coefficients of correlation (r) between PR values and different levels of leprosy (C i ) and the corresponding regression equations in different areas of the foot sole of leprosy subjects from walking foot pressure image analysis Foot areas Correlation coefficient (r) Regression equations 10.99PR 1 = 6.86 x C PR 2 = 7.04 x C PR 4 = 6.92 x C PR 5 = 6.98 x C PR 6 = 6.78 x C PR 7 = 7.21 x C PR 8 = 7.55 x C PR 9 = 7.46 x C PR 10 = 7.59 x C

SUMMARY OF THE WORKDONE The data collected (Clinical and Radiological) from the leprosy subjects in the different stages of progress of disease is arranged into seven different categories based on the changes taking place in sensation, muscle paralysis and different degrees of bone deformities. Walking foot pressure image distributions of 61 leprotic feet in different stages of leprosy are analysed in frequency domain. A new parameter, power ratio is used to distinguish between the foot pressure image patterns of leprotic subjects (in different levels of leprosy) and those of normal foot.

Statistical study involving calculation of student ’t’ test ‘p’ values has been carried out on mean PR values to distinguish (i) normal from higher stages of leprosy, (ii) normal leprosy from higher stages of leprosy, (iii) insensitive feet from higher stages of leprosy, (iv) insensitive feet and claw toes from higher stages of leprosy, (v) insensitive feet, claw toes and foot drop from higher stages of leprosy and (vi) insensitive, claw toes and early bone changes from higher stages of leprosy. PR values, with srandard deviations, are considered to check classification of different levels of leprosy subjects in three and four stages of leprosy. The statistical study has also been made for the calculation of coefficients of correlations ‘r’ to relate levels of leprosy to the mean values of parameter PR.

CONCLUSIONS The relative value of higher spatial frequency power in the total power spectrum is more in the images corresponding to higher levels of leprosy for the leprotic feet than those of the images of the normal feet in all the areas. The mean values of parameter, PR are able to distinguish clearly the (i) normal, (ii) normal leprosy, (iii) insensitive feet, (iv) insensitive feet and claw toes and (v) insensitive feet, claw toes and foot drop from the leprotic feet in higher levels of leprosy in all the areas

The parameter PR, with standard deviation values, (in four stages of classification) is able to clearly distinguish the normal from the leprotic feet and also makes a clear distinctions between the different levels of leprosy, namely (i) normal leprosy, (ii) insensitive and claw toes, (iii) insensitive, claw toes and early bone changes without any overlap in all the specified areas of the plantar surface Very good correlations of the order of 0.96 are found between levels of leprosy and PR values in all the areas of the plantar surface of the foot, which is a good measure of higher leprosy level giving rise to higher value of PR.

Considering the clinical data on scar tissue of the leprosy subjects and increase in PR values (from the corresponding normal values), it is observed that the early stage of leprosy is the one with insensitive feet and claw toes. This result could help in early detection of early levels of leprosy (based on PR values)and thereby help Orthopaedic surgeons to take early corrective action for preserving or restoring normal foot function.

Thank you Nizar Hussain. M