<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
<HTML>
<HEAD>
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
<META NAME="Generator" CONTENT="MS Exchange Server version 6.5.7654.12">
<TITLE>Sparse vs Dense ChanAndVeseLevelSetImageFilter</TITLE>
</HEAD>
<BODY>
<!-- Converted from text/plain format -->
<P><FONT SIZE=2>Hello Kishore,<BR>
<BR>
I have some questions on the sparse and dense chan&vese level set filters.<BR>
<BR>
1. I would expect getting the same segmentation result for a given volume using sparse and dense filters with the same parameters. However the result using the sparse filter is "bigger" (the level set evolved more) and non-smooth compared with the one using the dense. Is this acceptable?<BR>
<BR>
2. Debugging the sparse filter code in the place where is the CalculateUpdateValue function, we compute for the level set update:<BR>
ValueType new_value = old_value + dt * change;<BR>
In this place the old value is always 0 in the first iteration and 1e-06 in the next iterations. Is this correct? I would expect as old_values positive and negative values near zero depending on the distance from the zero level set.<BR>
I tried increasing the number of layers used in the narrow band, but it is still the same.<BR>
<BR>
3. Could it be possible in the future to have this function<BR>
virtual ValueType CalculateUpdateValue (const IndexType &, const TimeStepType &dt, const ValueType &value, const ValueType &change)<BR>
in the protected members of the dense filter as it is in the sparse right now?<BR>
( Currently, for the dense filter this calculation is embedded in the ApplyUpdate function )<BR>
<BR>
Thank you very much,<BR>
Eleni</FONT>
</P>
</BODY>
</HTML>