Dear Shreshtha, There are numerous methods available. You can simple google on Image Denoising Methods for Medical images or any types of images you are interested to work with. You will get lot of methods. Only concern is how to select better one, that could be decided by different image quality measures.

In fact, you may type my name (G R Sinha) in Google and get few  papers. You may also see few of my papers from Research Gate, Google Scholar or from my Website (www.drgrsinha.com)

Average filter, median filter and some frequency domain filters can be used to denoise.There are many algorithms and methods are available in the internet.

i think 

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.lri.fr/~kegl/research/PDFs/ChKe05P.pdf&ved=0ahUKEwi9o-SYre_JAhVHqQ4KHR5XDS0QFggvMAQ&usg=AFQjCNH99WgIWoQeV3DaJMPPDDxJ8AybIA&sig2=QA5qEgoOzDdbRXWUAY4ZmA

I promise to use Wavelet. This technics really reduce different type of noises. You can read about it in my publications.

Dear Mr. Shrestha Ranjit ,

there are some filters used in the MATLAB to denoise the image. You can use these functions, e.g.,  fspecial or filter2, to achieve your target. The command in MATLAB "help fspecial" or "help filter2" can show details of these two functions. A simple code is as follows:

I = imread('cameraman.tif');

subplot(1,2,1);imshow(I);title('Original Image');

H = fspecial('gaussian');

K1=filter2(H,I)/255;

subplot(1,2,2);imshow(K1);title('Filtered Image');

the function : 

h = fspecial(type)

h = fspecial(type,parameters)

can set different filters and the parameters, e.g., median filter, gaussian filter, laplacian, log, prewitt, sobel and so on.

other functions, such as wiener2, wpdencmp  (de-noising or compression using wavelet packets.) can also be found on Matlab.

I hope this message can help you.

Good luck!

Thanks everyone for your suggestions...

Dear Mr. Zhan,

Thank you very much for your valuable suggestion. It really works. Can you please guide me on how to determine the neighborhood while using the filter for image denoising?

The neighborhood is 4 or 8 neighbors to every pixel in an image. If you consider one pixel say at (x,y) location to which you wish to find neighborhood, then (x-1,y), (x+1,y), (x,y-1) and (x,y+1) are the four neighbors . Like wise your pixel of interest at (x,y) is the centre pixel. Then you can consider the next pixel as the center pixel and you can find neighbors to the new central pixel as mentioned above.