Convert Pixels to mm/cm from DICOM Tags (Ultrasound)

Question

I am working on a custom PACS solution and I need to implement a measurement tool for multi-frame ultrasounds (each study has multiple motion and still-frame components). I have done this for X-rays using the "Pixel Spacing" tag, but that is not present in the ultrasound. How can I calculate the distance between two points using the data provided in the DICOM tags?

Answer 1

You're going to need some sense of scale, possibly derived from the frequency/wavelength the probe is using. This may also depend on the type of probe used, which should be in the data somewhere.

(My father and brother are ultrasound techs; I'm the programmer. I'd have to ask for details in to how they'd read an ultrasound data set and find out the scale.)

Answer 2

You need to take a look at the US Region Calibration Module in Part 3 of the DICOM standard. That will tell you how the images are captured and how to translate the stored pixel values into the real-world pixel values. Remember that US image consists of multiple regions with each region representing a different entity.