Medical imaging
Because CT and MRI are sensitive to different tissue properties, the appearances of the images obtained with the two techniques differ markedly. In CT, X-rays must be blocked by some form of dense tissue to create an image, so the image quality when looking at soft tissues will be poor. In MRI, while any nucleus with a net nuclear spin can be used, the proton of the hydrogen atom remains the most widely used, especially in the clinical setting, because it is so ubiquitous and returns a large signal. This nucleus, present in water molecules, allows the excellent soft-tissue contrast achievable with MRI.
Marrow adipose tissue
To improve quantification of MAT, novel imaging techniques have been developed as a means to visualize and quantify MAT. Although proton magnetic resonance spectroscopy (1H-MRS) has been used with success to quantify vertebral MAT in humans, it is difficult to employ in laboratory animals. Magnetic resonance imaging (MRI) provides MAT assessment in the vertebral skeleton in conjunction with μCT-based marrow density measurements. A volumetric method to identify, quantify, and localize MAT in rodent bone has been recently developed, requiring osmium staining of bones and μCT imaging, followed by advanced image analysis of osmium-bound lipid volume (in mm) relative to bone volume. This technique provides reproducible quantification and visualization of MAT, enabling the ability to consistently quantify changes in MAT with diet, exercise, and agents that constrain precursor lineage allocation. Although the osmium method is quantitatively precise, osmium is toxic and cannot be compared across batched experiments. Recently, researchers developed and validated a 9.4T MRI scanner technique that allows localization and volumetric (3D) quantification that can be compared across experiments. 
Hematopoietic cells (also known as blood cells) reside in the bone marrow along with marrow adipocytes. These hematopoietic cells are derived from hematopoietic stem cells (HSC) which give rise to diverse cells: cells of the blood, immune system, as well as cells that break down bone (osteoclasts). HSC renewal occurs in the marrow stem cell niche, a microenvironment that contains cells and secreted factors that promote appropriate renewal and differentiation of HSC. The study of the stem cell niche is relevant to the field of oncology in order to improve therapy for multiple hematologic cancers. As such cancers are often treated with bone marrow transplantation, there is interest in improving the renewal of HSC. Recent work demonstrates that marrow adipocytes secrete factors that promote HSC renewal in most bones.