If you want to use PET, you should use fluorine-18 isotope as a sodium fluoride injection. It may show the changes in time. Calcium ha no suitable isotopes for PET studies....

Thanks for your answer. How about radioactive calcium 45 and microCT scanners of post mortem tissues of rats (bone) ? 

Ca-45 emits negative  beta  particles and low energy X-rays, these are not suitable for imaging. Though you might use this Ca isotope for doing auto-radiography of slices of the animal.......

Thank you.

Is there any other way to measure the dietary calcium intake and its specific deposition using non-radioactive material? I would appreciate any suggestions, thanks :)

Are you wanting Dietary intake, of uptake?  Dietary intake would be determined by offering a known amount of feed, measuring what was not consumed and calculating the amount of Calcium in the amount eaten.  Dietary uptake requires that you subtract for the intake the Calcium that is excreted.

Depending on the experimental design, Dual Energy X-Ray (DEXA or DXA) might allow the measurements in changes in Bone Mineral Density (BMD) and Bone Mineral Composition (BMC) that you are looking for.  You can also make these measurements with microCT (although with a higher dose to the animal.

I want to measure specific calcification of the bones and arteries using radioactive calcium using beta-emission detector. Would that be possible ?

I am not optimistic.

In vivo or ex vivo??

Ex vivo

Isolate several bone compartments and measure Calcium radioactivity 

I would use autoradiography then.

Could you suggest any names/literature I can read about ? That sounds interesting!

I will have isolated organs from mice mostly bone tissue (containing radioactive calcium isotope)

Thanks

Br. J. Nutr. (1967), 21, 413

Interrelations of calcium, fluorine and vitamin D in bone metabolis

DEBORAH GASTER, E. HAVIVI, K. GUGGENHEIM

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/79562014D4D7FCE777AE1235C11E990D/S0007114567000431a.pdf/div-class-title-interrelations-of-calcium-fluorine-and-vitamin-d-in-bone-metabolism-div.pdf