DICOM slice corrupted when saved as PNG

Question

I'm using SimpleITK to read a DICOM, and save a particular slice as a PNG file. I can write back a new DICOM file to disk fine, and it looks as expected. But whenever I try to save it in any other format, it's greatly corrupted. By that I mean it looks nothing like the input, it's completely garbled.

Here is the code:

        var imageReader = new ImageFileReader();
        imageReader.SetOutputPixelType(PixelIDValueEnum.sitkUInt8);
        var dicomFileNames = ImageSeriesReader.GetGDCMSeriesFileNames(@"D:\Study");
        imageReader.SetFileName(dicomFileNames[255]);
        var image = imageReader.Execute();
        var fileWriter = new ImageFileWriter();
        fileWriter.SetFileName("slice.png");
        fileWriter.Execute(image);

Getting the image's buffer and using it to create a BitMap suffers the same problem. Reading the DICOM series (my eventual goal) instead of one file, and using the 3D volume and extracting a slice in that manner also has the same issue.

What am I missing?

EDIT: Using PixelIDValueEnum.sitkUInt16 greatly improves the output of ImageFileWriter , although the contrast is off and loses some detail. I still cannot convert the buffer to a BitMap and save that as a PNG, this code still creates corrupted data:

        var size = image.GetSize();
        var length = (int)(size[0] * size[1]) * 2;
        var buffer = image.GetBufferAsUInt16();

        var rgbValues = new byte[length];

        Marshal.Copy(buffer, rgbValues, 0, length);

        var newBitmap = new Bitmap((int)image.GetWidth(), (int)image.GetHeight(), (int)image.GetWidth(), PixelFormat.Format16bppArgb1555, buffer);
        newBitmap.Save(@"C:\test.png", ImageFormat.Png);

I have tried every PixelFormat.16bpp* value without success, some data must be getting lost, because the output of the ImageFileWriter is more than 50% larger than when I save the bitmap.

Here is the bad BitMap:

Answer 1

Most medical images are 16 bit deep ( short or unsigned short ), not 8 bit ( sitkUInt8 ). Try a few other pixel formats. If that does not help, attach an extracted PNG slice - that will allow more/better advice.