Is it possible to rescale intensity of a volume?

Support
1

I want to rescale a Volume created reading a wrongly calibrated dicom file. Is this possible?

Usually this is automatically done with the RescaleIntercept and RescaleSlope from the dicom header but when those values are wrong or missing then I need to do this manually.

2

You can modify the pixel values directly:

https://www.slicer.org/wiki/Documentation/Nightly/Developers/Python_scripting#Accessing_Volume_data_as_numpy_array

3

Hi Alex,

I have one idea how to do this. Download the “ImageMaker” module. Create two images: one with the desired offset, and one with the desired scale. Then use the “Add Volume” and “Multiply Volume” modules in the “Filter” menu to adjust your image.

Of course, any better idea is welcome J

Greg

4

The easiest way to do this IMO is use the “ShiftScaleImageFilter” from the Simple Filters module. Just enter your correction factor as the scale factor.

5

Does this also apply for the calibration of CBCT to MDCT?

I have a CBCT and MDCT of the same specimen and I want to “convert” the grey values in CBCT accordingly the ones in MDCT and consequently be able to measure “HU” values in the CBCT volume?

How can I calculate the correction factor?

6

Grey values (GV) to HU units conversion asked a similar question since your post.

Additionally, I’ve found literature that states that calibrating CBCT values based on correlation with Multi-slice CT (MSCT) will not provide accurate density measurements (Pauwels et al., 2013).

I’m assuming that MSCT and MDCT are similar enough, in contrast to CBCT, that the challenge between MSCT and CBCT is translatable to MDCT and CBCT.

Reference:
Pauwels, R., Nackaerts, O., Bellaiche, N., Stamatakis, H., Tsiklakis, K., Walker, A., Bosmans, H., Bogaerts, R., Jacobs, R., Horner, K., & The SEDENTEXCT Project Consortium. (2013). Variability of dental cone beam CT grey values for density estimations. British Journal of Radiology, 86(1021), 20120135. https://doi.org/10.1259/bjr.20120135