Editorial[Advanced MRI, MR as well as Optical Spectroscopy]

The last quarter century has witnessed the introduction of a variety of powerful techniques that have allowed visualization of organ structure and function with exquisite detail. This in turn has brought about a true revolution in the day-to-day practice of medicine. There are six articles in this issue, related to the MRI for cartilage and disc, oncology, brain function and dementia, the MR spectroscopy for breast and ovary cancer, and the optical spectroscopy for cerebral blood flow. Although MRI has become the most accurate test for depicting abnormal anatomy, there is no agreement on the diagnostic value of morphology alone. If the natural history of a disease is not clearly understood, and if there is little consensus regarding the use of diagnostic tests, the risk of misdiagnosis is high. Degenerative disc disease is debilitating, costly, and one of the most complex conditions to manage. MRI has demonstrated alterations in material properties (mainly glycosamineoglycans, water and collagen) of hydrated cartilages and also intervertebral disc tissues during the disease developments. The long term goal would develop techniques to detect changes of early degeneration of cartilages and discs. It was found that contrast-enhanced MRI improved lesion detection, delineation, and specificity. The major factors influencing lesion detection include lesion contrast, size, location, and type. Dynamic contrast enhanced MRI (DCE-MRI) enables the quantitative assessment of tumor status using blood flow, vessel permeability, and tissue volume fractions extracted from each voxel or region of interest. Functional MRI has been widely used to evaluate brain response for extensive number of different tasks, and primarily intended for the assessment of physiologic phenomena, such as changes in blood flow and perfusion to an organ or diseased tissue. I remains unclear which brain region is relevant for the principal cognitive/behavioral function and which areas are activated either ws a result of the additional cognitive function or as consequence of brainconnectivity. The recent conbination of transcranial magnetic stimulation and functional MRI has shown to be a promising tool to clarify this dilemma. With the current trend towards increasing longevity of life, the prevalence of dementia will become higher during the next few decades. Dementic illness imposes significant burdens on the society, health care and economy. Neurochemical imaging is one of the most established molecular imaging technique. There have been tremendous efforts to develop radioligands specific to each neurochemical system. Investigational applications of neurochemical imaging indementing disorders are extensive. These investigations have provided important insights into disease processes inliving human patients. Frontotemporal decrease of the activity on functional imaging is an independent marker of the frontal variant of frontotemporal dementia. MR spectroscopy (MRS) is increasingly receiving more attention from oncologists, neuropsychiatrists, radiologists, and other clinicians. The choline peak from proton spectra is a constitution of the phospholipids metabolism of cell membrane and thus reflects a membrane turnover. It is a precursor of acetylcholine and phosphatidylcholine and therefore increased choline probably suggests increased membrane synthesis or an increased number of cells such as seen in active tumors. Efforts are addressed to evaluate effectiveness and potential use of MRS and choline-based PET in cancer diagnosis. Optical imaging is a very powerful molecular imaging probe, but it does not lend itself well to examining biologic processes. Tradionally it has had physiological limitations in visualizing deel structures or lesions. However, new-generation near infrared spectroscopy (NIRS) instrumentation with depth-resolved technologies and invasive NIRS probes will provide unique physiologic informations including cerebral blood flow.