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a                                     b
          Figure 2: (a) A view of the three‑dimensional clusters in the hue, saturation, and intensity space, showing various tissue‑categories; (b) another view
          of the clusters in the hue, saturation, and intensity space from a different orientation. These two views show all the tissue categories, and that the
          clusters are fairly distinct

          Table 1: Values of inter-cluster MD in the HSI space  (15  in this case). The values of  %Match were computed
                HGT   UGT   WS    G     G    F    BNT   Ga    using both methods and Table 2 lists the values obtained.
                                    1    2                    The relatively poor performance with respect to UGT and
           HGT   0    2.69  3.73  3.7  3.95  3.43  3.54  3.88  Ga may be attributed to the absence of a tight cluster in
           UGT  2.69   0    3.26  3.71  3.95  3.03  3.67  3.94  the  first  case,  and a  large  spread  in  the  second. Indeed,
           WS   3.73  3.26   0    3.61  3.95  3.09  3.92  4.15  both are difficult to judge visually;  UGT is close to HGT
           G 1   3.7  3.71  3.61   0   3.3  3.69  3.84  3.93
           G    3.95  3.95  3.95  3.3   0   3.94  3.94  3.86  in color, and  Ga  is very dark  to allow  easy identification
            2                                                 of its hue. To understand the behavior quantitatively, the
           F    3.43  3.03  3.09  3.69  3.94  0   3.7   3.93
           BNT  3.54  3.67  3.92  3.84  3.94  3.7  0    3.01  inter‑cluster MDs were calculated as listed in Table 1. One
           Ga   3.88  3.94  4.15  3.93  3.86  3.93  3.01  0   may observe that the distances between HGT and UGT, Ga
                                                              and BNT, are relatively small.
           HIS: Hue, saturation, and intensity, MD: Mahalanobis distance,
           HGT: Healthy granulation tissue, UGT: Unhealthy granulation tissue,
           WS: Whitish slough, G : Yellowish green pigmentation, G : Bluish green   DISCUSSION
                                                2
                         1
           pigmentation, F: Fat, BNT: Brown necrotic tissue, Ga: Gangrene
                                                              In this paper, there was no attempt to refine the cluster
          individual clusters, as suggested by Hertzog period.  The   structure in the HSI space, by breaking apparently
                                                     [24]
          distances agree  with  the  visual  (geometric) separations.   disjointed clusters or joining those close to each other,
          The distance between  HGT and UGTs is  the smallest.   as reported by  Nayak  et  al.  Modifying  the  clusters is
                                                                                      [14]
          The  cluster  associated with  UGT  appears to  consist  of   not meaningful, as some color  spread is natural.  Such
                                                                                                         [2]
          two lobes, though over a narrow range of hue, because   variations  are  captured in  the  cluster shapes and are
          the  color associated with  the unhealthy bed can vary   incorporated in  the  algorithms proposed in  this  paper.
          slightly  due to poor vascularity,  infections,  etc. Clinically,   Although we  experimented  with the  inter‑quartile  range,
          considering UGT to consist of two clusters is  therefore   retaining central tendencies, and the improvement in the
          unnecessary. Instead, this is addressed mathematically   accuracy of classification was not significant. [20]
          through an algorithm that exploits cluster shape.
                                                              There are some limitations  in the presented study.
          To test the efficacy of the proposed algorithms,  a set of   As  reported,  a  modified  HSI  space was  used,  which
          15 test images were used to perform 120 experiments   involves a shift of the origin. This approach suggested by
          (15/category).  Each experiment  began  with  the  selection   Hoppe  et  al.   ensures  a  continuous  value  for hue,  which
                                                                         [8]
          of a relatively homogenous  region  of interest  (ROI),   is used as a parameter. The choice of the origin and the
          selected randomly from the test images. A visual estimate   minimal range of hues was based on empirical observations
          of the composition  (in terms of the percentage of the   of  data  involving  nearly  9,000  pixels.  While  there  could
          main tissue/pigmentation)  was declared by one author   be  some  change in  the precise  values attributed  to the
          who was blinded to the  selection  of the  ROI.  The ROI   camera and ambience,  color calibration can account for
          was subjected to estimation  of its composition by the   such variations.  Indeed,  variation  associated with  the
          algorithms described in this paper. The performance of   range  of hues  is  minimal  in  comparison with  the  other
          the  algorithm  in  terms  of accuracy of the  estimates  is   parameters.  However, it would be interesting to find an
                                                                        [8]
          defined by:                                         approach  to determine the values of the parameters to
                         1  N exp                             facilitate a shift of the origin.  Further, simulated images
          %Match  =  [ 1 −   ∑ |E v  −  E c  | ] ×100    (5)  and varying  ambience  could be  used to test  the  efficacy
                       N exp  i =1  i   i                     of the values derived by such a method.

          where  E   and  E   are  the  fractional estimates  (visual   To validate the algorithms, randomly selected and
                         Ci
                 Vi
          and computer‑assisted) of the tissue  and pigmentation   blinded ROIs  were used to mitigate  bias.  Nevertheless,
          composition, and  Nexp is the number  of experiments   the  approach presented  has limitations;  specifically,  it
           264                                                           Plast Aesthet Res || Vol 2 || Issue 5 || Sep 15, 2015
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