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Hi
Can anyone tell me whether High Pass Filter can be used for the analysis of surface features present on the soft materials such as live cells. Or such an application is only useful for analyzing the edge features of hard surfaces.
Any references on this topic would be highly appreciated.
I use very old version - Nanoscope 5.30r3sr3.
Thanks and regards
Shashikanth P.B.
Hi Shashikanth~
In some cases, high pass filtering does allow you to better observe features on the surface of cells in your height image. It is also comparable to looking at the error signal image (deflection, amplitude). This is why you will often see deflection or amplitude images shown in AFM cell studies - you do see 'edges' of the cells more clearly. This is perfectly fine to do, just be careful not to take height analysis measurements from either the high pass filtered height image or the error signal image.
I hope this helps to answer your question.
Best,
Andrea
Dear Shashikanth,
Using a high-pass filter will pass high high frequencies but will reduce frequencies which are lower that the cut-off frequencies of the used filter. In other words, this will lead to an unsharp effect on your image. It should not be restricted exclusively to hard surfaces but is usually more used on atomic-resolution samples and ultra-flat surfaces.
If you want to get a nice 3d-rending of your image, a low-pass filter is more recommanded.
Alex.
Dear Andrea and Alex
Thanks for your suggestions.
Andrea, I actually selected the height images and performed the off-line high pass filter analysis. This greatly enhanced the surface features, which were not so clear in the height or deflection images. Yep, I am not doing any height analysis on HPF images.
Alex, as you said, I performed the Low pass filter analysis, but I am afraid that did not bring in any considerable changes in the contrast of the image, similar to that of high pass filter (HPF). Does this mean that the features which were revealed by the HPF are some kind of artifacts. Or they can be, indeed considered as the features? Please let me know.
Could you suggest any specific reference(s) which dealt with the HPF/LPF in image analysis of cells.
Thanks and Regards
Shashikanth
Hello, Shashikanth
My personal preference for image processing is the less the better because sometimes I found it is difficult to know whether you are removing or adding artifacts. However, as Andrea and Alex have previously mentioned, image processing using low-pass or high-pass filters can be applied as a part of your imagining analysis regardless the sample is hard or soft. I found several papers useful regarding to image processing on AFM imaging of biological samples. I have listed them below. Hopefully, you will find it useful as well.
Best regards,
James
References:
--------------------
(1) Improving the contrast of topographical AFM images by a simple averaging filter.
Kienberger F, Pastushenko VP, Kada G, Puntheeranurak T, Chtcheglova L, Riethmueller C, Rankl C, Ebner A, Hinterdorfer P.
-----------------
(2) Imaging Single Virus Particles on the Surface of Cell Membranes by High-Resolution Scanning Surface Confocal Microscopy
Andrew I. Shevchuk,* Phil Hobson,† Max J. Lab,* David Klenerman,‡ Nina Krauzewicz,† and Yuri E. Korchev*
Lyubchenko Y, Shlyakhtenko L, Harrington R, Oden P, Lindsay S.
Hi James
Thanks very much for your comments and also citing some useful references.
Best regards