BMD computation

[Mahmoudi Sidi Ahmed]

Dear all,

I would like to computer the Bone Mineral Density (BMD) using DICOM CT scans. However, I don't find this functionnality within BoneJ.

I found the pQCT Density Distribtion but the latter requires pQCT snacs.

Do you have any idea for computing BMD in my case ?

Best regards,

Sidi, 

[Michael Doube]

Dear Sidi,

This is usually achieved by scanning some phantoms of known 'BMD' then applying a calibration function to your image using ImageJ's Analyze > Calibrate... command. Be aware that the relation between CT pixel value and BMD may be a non-linear, and maybe even piecewise, function.

Then, the pixel values will be converted to BMD values for your measurements.

'BMD' measurements are highly scale dependent: low resolution techniques such as CT, pQCT and DXA are strongly influenced by BV/TV, i.e. how much marrow space there is & the size of the mineralised features in relation to the sample spacing (~= pixel 'size'). Meanwhile, high resolution techniques like qBSE SEM measure mineralisation of the bone extracellular matrix alone, unconfounded by unmineralised cell and marrow spaces because the sample spacing is on the order of 10s of nm (at least, submicron).

Michael

[Michael Doube]

And I forgot to mention: ordinary CT images are typically full of all sorts of artefacts relating to X-ray physics (e.g. beam hardening) and reconstruction technique (e.g. edge sharpening filters), further reducing the linearity between pixel value and BMD. Be careful!

Michael

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[Ali Ghasem Zadeh]

Dear Sidi,

If you are using CTScaner , most of them have  got a specific phantom which called QC reference phantom  (with known volumetric density).

You can plot HU and real density on X and Y axis and then you will be able to calculate the function of HU and volumetric density.

Cheers

Ali

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[Mahmoudi Sidi Ahmed]

Thank you Michael for your answer,

I would like to know if Image J allows to calculate BMD for one image only ? In fact, I want to calculate BMD for the whole image sequence (DICOM files). Is it mandatory to select a ROI ?

Finally, I don't see how to include the phantom values within Image J.

Thanks in advance,

Sidi,

[Michael Doube]

Dear Sidi,

Please take the time to read the ImageJ manual, which will help to answer these questions.

http://rsbweb.nih.gov/ij/docs/guide/

Michael

[Mahmoudi Sidi Ahmed]

Thank you Ali for your answer,

I would like to know if Image J allows to calculate BMD for one image only ? In fact, I want to calculate BMD for the whole image sequence (DICOM files). Is it mandatory to select a ROI ?

Finally, I don't see how to include the phantom values within Image J.

Thanks in advance,

Sidi,

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[Mahmoudi Sidi Ahmed]

Dear all,

A suggested, I'm using The Image j calibration to compute BMD. In fact, after selecting the pjhantom values and launching "calibrate" I obtain a graph showing different pixel values with the corresponding densities.

 However, I would like to obtain the BMD values that corespond the input image sequence. 

Any idea ?

Best regards, 

Sidi,