CSF plays key role in space-induced visual impairment

Astronauts on lengthy space missions often suffer afterwards from blurry vision and structural changes in their eyes, a syndrome known as visual impairment intracranial pressure (VIIP). Nearly two-thirds of astronauts on long-duration missions aboard the International Space Station (ISS) have reported such problems. VIIP was previously attributed to a shift of vascular fluid toward the upper body due to the microgravity of space. Now, a team led by Noam Alperin from the University of Miami Miller School of Medicine has revealed another possible cause: cerebrospinal fluid (CSF). The CSF system is designed to accommodate significant changes in hydrostatic pressures, such as those that occur when a person moves from lying down to standing up. In microgravity, however, the system is confused by the lack of posture-related pressure changes.

Alperin and colleagues performed high-resolution orbit and brain MRI scans before and shortly after spaceflights for seven long-duration ISS astronauts and nine Space Shuttle astronauts. They found that, compared with short-duration astronauts, ISS crew members had significantly increased post-flight flattening of their eyeballs and increased optic nerve protrusion. These large post-spaceflight ocular changes were associated with greater post-flight increases in intra-orbital and intra-cranial CSF volume. "By 2010, there was growing concern as it became apparent that some astronauts had severe structural changes that were not fully reversible upon return to earth," explained Alperin. "The research provides, for the first time, quantitative evidence pointing to the primary and direct role of the CSF in the globe deformations seen in astronauts with visual impairment syndrome." Identifying the origin of space-induced ocular changes is necessary to develop countermeasures to protect the crew from the ill effects of long exposure to microgravity, he added.

Virtual reality models visualize foetus in 3D

MRI provides high-resolution foetal images with excellent contrast, and is used in cases where ultrasound cannot provide sufficiently high-quality images. Now, researchers in Brazil have developed a technology that transforms MRI and ultrasound data into a 3D virtual reality model of a foetus. The generated models were remarkably similar to the appearance of the newborn baby. "The 3D foetal models combined with virtual reality immersive technologies may improve our understanding of foetal anatomical characteristics," explained Heron Werner Jr from the Clínica de Diagnóstico por Imagem. "Physicians can access an immersive experience on the clinical case that they are working on, having the whole internal structure of the foetus in 3D in order to better visualize and share the morphological information. We believe that these images will help facilitate a multidisciplinary discussion about some pathologies in addition to bringing a new experience for parents when following the development of their unborn child."

3D model of a 26-week foetus generated from MRI files

Model construction starts with sequentially-mounted MRI slices, followed by a segmentation process where the physician selects the body parts to be reconstructed in 3D. Once an accurate 3D model has been created – including the womb, umbilical cord, placenta and foetus – the virtual reality device (in this work, an Oculus Rift 2 headset) is programmed to incorporate the model. Oculus Rift 2 provides sharper foetal images than those viewed on a traditional display, and allows users to hear the baby's heartbeat and, by moving their head, study the foetal anatomy. One potential application is assessment of airway opening, an important issue for a developing foetus. The team has already used the technique on patients, including cases where the foetus had evidence of an abnormality that required postnatal surgery, and they hope to expand its use over the next year.

No evidence for age-based mammography cut-off

Mammography is the standard imaging exam for breast cancer screening, but guidelines regarding the age at which to stop screening are a source of controversy. "All prior randomized, controlled trials excluded women older than 75, limiting available data to small observational studies," said Cindy S Lee, from the University of California, San Francisco. "There has been a lot of controversy, debate and conversation regarding the different breast cancer screening guidelines, even among major national organizations, over the past few years." To address this knowledge gap, Lee and her team used data from the National Mammography Database to analyse nearly 5.6 million screening mammograms performed between January 2008 and December 2014 in 150 US facilities.

The researchers grouped data from 2.5 million women by age in five-year intervals, and calculated four performance metrics for each age group: cancer detection rate, recall rate, and positive predictive values for biopsy recommended (PPV2) and biopsy performed (PPV3). An ideal screening performance would be a high detection rate, PPV2 and PPV3, and a low recall rate. Overall, they found mean cancer detection rate of 3.74 per 1000 patients, recall rate of 10%, PPV2 of 20% and PPV3 of 29%. As age increased from 40 to 90, cancer detection rate and positive predictive values increased and recall rate decreased. The findings do not provide evidence for age-based mammography cessation but support the argument that the decision whether or not to stop screening should be informed by an individual's personal health history and preferences.

Depression in soldiers linked to brain injury

A large number of soldiers return from war with mild traumatic brain injury (mTBI). In addition, psychiatric disorders such as anxiety and major depressive disorders are becoming common in military personnel with brain injuries. Now, researchers have used MRI brain imaging techniques to reveal a possible physical foundation for depression symptoms in soldiers who suffered mTBI in combat. "We can link these connectivity changes in the brain to poor top-down emotional processing and greater maladaptive rumination, or worrying, in symptomatic depressed soldiers after mTBI," explained Ping-Hong Yeh, from the National Intrepid Center of Excellence, Walter Reed National Military Medical Center.

MRI reveals changes in the brains of soldiers with depression

For the study, the researchers used diffusion-weighted imaging (DWI) and resting-state functional MRI (fMRI) to examine 130 male active military service members diagnosed with mTBI plus a control group of 52 men without mTBI. Using the Beck Depression Inventory (BDI) to rate depression showed that 75 of the mTBI patients had moderate to severe depression symptoms (BDI scores greater than 20). The imaging exams revealed that white matter tracts were disrupted in this group of patients; these patients also exhibited changes in their grey matter cognitive-emotional networks. "We found consistencies in the locations of disrupted neurocircuitry as revealed by DWI and resting-state fMRI that are unique to the clinical symptoms of mTBI patients," said Yeh. "We have related the brain structural and functional changes in cognitive-emotional networks to depressive symptoms in mTBI patients." He noted that this research could lead to treatment strategies in the future.

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