basic experimental design:
started with 60 mice at 6 weeks of age, using MRI and PET imaging, I defined the volume of a particular organ that changes as the animal ages- I also determined mean glucose uptake within that organ.
20 animals were sacrificed immediately after imaging- the organ was removed and weighed, and several other cell based function measurements were performed.
remaining 40 animals were aged to 24 weeks- all animals imaged (MRI & PET)- 20 animals sacrificed, organ removed- same assays performed as above.
Remaining 20 animals were aged to 52 weeks- all animals were imaged (MRI & PET)- animals were sacrificed, organ removed- same assays performed as above.
what I am trying to do is establish a correlation between the imaging data and the cellular measurements data- I have done a regression analysis- x axis is total number of cells in the organ for 60 animals (20 at 6 weeks, 20 at 25 weeks and 20 at 52 weeks); y axis is the PET/MRI measured glucose metabolism for that organ at that timepoint just prior to sacrifice (20 at 6 weeks, 20 at 25 weeks and 20 at 52 weeks). I have then done a Pearson correlation and am showing p value and r^2.
Cell numbers within this organ are known to decline with age, I am simply trying to establish an imaging approach as a viable method for non-invasively assessing the organ. I have done the same regression to correlate glucose uptake with other parameters of organ function.
Is this a valid approach. Someone told me I need to also do an ANOVA- but I am not sure if I need to.... PLEASE HELP!!??