Density calculation sometimes can be confusing

[Rev. Cheeseman]

"weight/mass and the size", just like you stated in what I quoted.

That's how those DEXA scan machines calculated the bone mineral density. You stated previously "Bone density as measured by clinical densitometry is different from the density understand as a physical property of matter. Names are similar but they mean different things." I agree with it.

 

[Rev. Cheeseman]

"weight/mass and the size", just like you stated in what I quoted.

I mean, the mass or weight and the two-dimensional surface or area which is basically two-dimensional representation of the bone size are already there before we divide them to get the surface/areal density.

 

[Borek]

That's how those DEXA scan machines calculated the bone mineral density.

Nope. They _measure_ optical density and bone cross section (these things are doable using xray image) and _estimate_ bone mass and bone volume from these numbers. You got it reversed.

 

[Rev. Cheeseman]

Nope. They _measure_ optical density and bone cross section (these things are doable using xray image) and _estimate_ bone mass and bone volume from these numbers. You got it reversed.

By dividing mass/weight with the surface/area. Correct?

 

[Orodruin]

By dividing mass/weight with the surface/area. Correct?

No. You do not have the mass or weight. That is why you need to estimate it from what you can infer.

 

[Rev. Cheeseman]

No. You do not have the mass or weight. That is why you need to estimate it from what you can infer.

So, the bone mineral weight or mass that is calculated from the DEXA scan machines are just estimations?

 

[chemisttree]

Yes. You actually measure mass with something like a mass scale which measures force due to mass. The machine you describe can measure the attenuation of the x-ray beam as it passes through the bone and that is correlated to mass.