Previous measurements of the hydroxyl (OH-) ion content of the calcium phosphate crystals of bone mineral have indicated a substantial depletion or near-absence of OH-, despite its presumed status as a constituent of the hydroxyapatite lattice. Analytical methods for determining bone crystal OH- content have depended on procedures or assumptions that may have biased the results, such as chemical pretreatment to eliminate interference from the organic matrix. We demonstrate a two-dimensional solid-state nuclear magnetic resonance (NMR) spectroscopy technique that detects the proton spectrum of bone crystals while suppressing the interfering matrix signals, eliminating the need for specimen pretreatment other than cryogenic grinding. Results on fresh-frozen and ground whole bone of several mammalian species show that the bone crystal OH- is readily detectable; a rough estimate yields an OH- content of human cortical bone of about 20% of the amount expected in stoichiometric hydroxyapatite. This finding sheds light on the biochemical processes underlying normal and abnormal bone mineral metabolism.

P22 viral capsids and ferritin protein cages are utilized as templating macromolecules to conjugate Gd(III)-chelating agent complexes, and we systematically investigates the effects of the macromolecules' size and the conjugation positions of Gd(III)-chelating agents on the magnetic resonance (MR) relaxivities and the resulting image contrasts. The relaxivity values of the Gd(III)-chelating agent-conjugated P22 viral capsids (outer diameter: 64 nm) are dramatically increased as compared to both free Gd(III)-chelating agents and Gd(III)-chelating agent-conjugated ferritins (outer diameter: 12 nm), suggesting that the large sized P22 viral capsids exhibit a much slower tumbling rate, which results in a faster T1 relaxation rate. Gd(III)-chelating agents are attached to either the interior or exterior surface of P22 viral capsids and the conjugation positions of Gd(III)-chelating agents, however, do not have a significant effect on the relaxivity values of the macromolecular conjugates. The contrast enhancement of Gd(III)-chelating agent-conjugated P22 viral capsids is confirmed by in vitro phantom imaging at a short repetition times (TR) and the potential usage of Gd(III)-chelating agent-conjugated P22 viral capsids for in vivo MR imaging is validated by visualizing a mouse's intravascular system, including the carotid, mammary arteries, the jugular vein, and the superficial vessels of the head at an isotropic resolution of 250 μm.

Various functional magnetic resonance (MR) imaging techniques are used for evaluating prostate cancer including diffusion-weighted imaging, dynamic contrast-enhanced MR imaging, and MR spectroscopy. These techniques provide unique information that is helpful to differentiate prostate cancer from non-cancerous tissue and have been proven to improve the diagnostic performance of MRI not only for cancer detection, but also for staging, post-treatment monitoring, and guiding prostate biopsies. However, each functional MR imaging technique also has inherent challenges. Therefore, in order to make accurate diagnoses, it is important to comprehensively understand their advantages and limitations, histologic background related with image findings, and their clinical relevance for evaluating prostate cancer. This article will review the basic principles and clinical significance of functional MR imaging for evaluating prostate cancer.