Imaging Genetics of Brain Longevity and Mental Wellness: The Next Frontier?

Effect of APOE4 allele on glucose metabolism in young adults. Image illustrates regions of the brain with abnormally low glucose metabolism measured at FDG PET in young adult carriers of APOE4 allele in relation to those of patients with probable Alzheimer disease (AD). 3D surface-projection map of abnormally low glucose metabolism in young adult 4 carriers is superimposed on a map of abnormally low glucose metabolism in previously studied patients with probable AD. (Reprinted, with permission, from Reiman E.M., Chen K., Alexander G.E., et al. Functional brain abnormalities in young adults at genetic risk for late-onset Alzheimer’s dementia. Proc Natl Acad Sci USA 2004;101:284–289). (Radiology 2008;246:20–32) © RSNA, 2008. All rights reserved. Printed with permission.

Nearly two-thirds of the approximately 30,000 genes in the human genome are related to brain function and up to half the variance in age-related changes in cognition, brain volume and neuronal function appears to be genetically determined. As neuroimaging is employed to study the effects of genes, neurogenetics may affect future radiology research and practice.

In a review article in the January issue of Radiology (RSNA.org/radiology), Jeffrey R. Petrella, M.D., Venkata S. Mattay, M.D., and P. Murali Doraiswamy, M.D., of Duke University Medical Center review the basic principles of imaging genetics. They also summarize genetic polymorphisms that may potentially affect brain aging and use specific polymorphisms to illustrate how genetic-imaging findings are evolving and may affect radiology.

Specifically, the researchers address:

• Genomics, proteomics and metabolomics of brain function

• Genes and brain longevity

• Apolipoprotein E (APOE) gene

• Genes regulating neurotransmitter enzymes or receptors

• Genes regulating neuronal growth factors

As technology advances, public interest in genotyping will continue to grow, according to the researchers, who note the confidential genotyping services becoming available commercially via the Internet. The researchers add, however, that physicians should be wary of rushing to adopt new technology until appropriate sensitivity and specificity studies are conducted and genomics can be shown to improve patient outcomes above and beyond currently available clinical measures.

"Until then, imaging-genetics correlative studies will remain a useful research tool to enhance our knowledge of the aging and diseased brain," the researchers conclude.

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MR Urography: Techniques and Clinical Applications

MR urography is one of the newer technologies developed for imaging the urinary tract. An evolving group of techniques gives MR urography the potential to provide the most comprehensive and specific imaging test available for many urinary tract abnormalities, noninvasively and without the use of ionizing radiation. Formidable limitations and challenges remain, however, including relative insensitivity for renal calculi, relatively long imaging times, sensitivity to motion and lower spatial resolution compared with CT and radiography.

In an article in the January-February issue of RadioGraphics (RSNA.org/radiographics), John R. Leyendecker, M.D., Craig E. Barnes, M.D., and Ronald J. Zagoria, M.D., review the most common MR imaging techniques used to image the urinary tract and discuss special considerations for pediatric patients, pregnant patients and patients with renal insufficiency. The authors also:

• Illustrate potential clinical applications of MR urography with respect to urolithiasis, urinary tract obstruction unrelated to urolithiasis, hematuria and congenital anomalies

• Identify common MR urographic artifacts and pitfalls

"When properly performed, MR urography can be a valuable means of noninvasively assessing the urinary tract," the authors conclude. "The successful interpretation of MR urographic examinations requires familiarity with the numerous potential pitfalls and artifacts that may be encountered."

To access this RadioGraphics article now, click here.

Neobladder outlet obstruction in a 65-year-old man who had undergone cystectomy and ileal neobladder reconstruction for adenocarcinoma of the bladder. (a) Coronal maximum intensity projection (MIP) image from excretory MR urographic data obtained as part of routine follow-up demonstrates marked dilatation of both upper collecting systems (arrows) and the neobladder due to outlet obstruction. The patient was asymptomatic at the time of the examination. (b) Axial gadolinium-enhanced 3D fat-suppressed gradient-echo MR image (LAVA) through the urethral anastomosis shows that an enhancing recurrent tumor (arrow) is responsible for the outlet obstruction. (RadioGraphics 2008;28:23–48) © RSNA, 2008. All rights reserved. Printed with permission.

This article meets the criteria for 1.0 AMA PRA Category 1 Credit™. CME is available online only.