MRI reveals cardiac changes during free diving

Free diving – an extreme sport in which the diver descends hundreds of feet below the surface of the ocean whilst holding their breath – is becoming increasingly popular. But according to researchers at the University of Bonn, significant cardiovascular changes occur during such dives, posing potential dangers, particularly to inexperienced divers. The researchers used MRI to study the effects of simulated free diving on the cardiovascular systems of 17 elite free divers aged between 23 and 58. Subjects underwent cardiac MRI and phase-contrast MRI of the carotid arteries before, during and after a maximum breath hold. The mean breath hold duration was 297 s in the cardiac session and 276 s in the blood flow session; the maximum apnea was 483 s.

"These athletes train to be able to hold their breath for long periods," explained study author Jonas Dörner, now at the University Hospital of Cologne. "When they get into the water, they are able to hold their breath even longer due to the diving reflex." The diving reflex, triggered when the body is submerged underwater without oxygen, causes a decreased heart rate, reduced cardiac output and peripheral vasoconstriction. These effects occur to a lesser degree during prolonged breath hold without submersion. Flow measurements revealed that during apnea, the amount of blood flowing to the brain increased and then levelled off. Cardiac MRI showed that the heart pumped more strongly at first, but dilated and began to struggle over time. The changes in heart function were similar to those seen in patients with systolic heart failure, but were transient in the divers, with heart function recovering within minutes of breathing again.

Can gaming technology improve X-ray imaging?

New software for the Microsoft Kinect – a motion sensor device created for the Xbox gaming system – could improve the quality of X-ray imaging. The software automatically measures body part thickness, and checks for motion, positioning and beam adjustment immediately prior to imaging, reducing or eliminating common causes of unnecessary repeat examinations. "Patients, technologists and radiologists want the best quality X-rays at the lowest dose possible without repeating images," explained Steven Don, from Washington University School of Medicine in St. Louis. "This technology is a tool to help achieve that goal. Patients will benefit from reduced radiation exposure and higher quality images to ensure diagnostic accuracy."

The new Microsoft Kinect software is tested on a moving volunteer.

In a feasibility study, Don and colleagues combined Microsoft Kinect 1.0 technology with proprietary software to control radiation dose variation by measuring body-part thickness, without requiring traditional callipers. The system automatically displayed thickness measurements with a precision of 1 mm at the central ray, defined body part or a user-specified point. The software also provided valuable information regarding the patient's motion and positioning with respect to the automatic exposure control (AEC) sensors, image receptor and body part within the X-ray field. The software uses colour coding to alert the user, in real time, if any of these factors could compromise image quality. "This device can help technologists and radiologists achieve the radiation dose goal of ALARA, As Low As Reasonably Achievable, while enhancing the quality and consistency of X-ray images," said Don.

Link found between early brain and heart disease

A Dutch study of thousands of healthy adults has found a connection between very early stages of brain and heart disease. Hazel Zonneveld from Erasmus University Medical Center and colleagues analysed data from 2432 participants in the Rotterdam Study, a prospective, population-based study designed to investigate chronic diseases in an aging population. All participants (mean age 56.6 years) underwent diffusion tensor imaging-based brain MRI, and blood tests to measure levels of NT-proBNP, a peptide that provides information on early cardiac dysfunction. MRI data were evaluated for markers of early brain disease, including loss of brain volume, microstructural changes and white matter lesions. "Diffusion tensor imaging gives us information on the microstructural organization of the brain's white matter," Zonneveld explained. "It is thought that microstructural brain changes precede brain changes, such as white matter lesions."

The results showed that participants with higher NT-proBNP levels had worse microstructural organization within the white matter. Statistical analysis revealed that higher levels of this peptide were also associated with smaller total brain volume, predominantly driven by grey matter volume, and larger white matter lesion volume. Zonneveld says that the study is the first to demonstrate an association between NT-proBNP and the microstructure of the brain. The researchers concluded that subclinical cardiac dysfunction, as reflected by serum NT-proBNP levels, is associated with global and microstructural imaging markers of subclinical brain disease. "This implies that the heart and brain are intimately linked, even in presumably healthy individuals, and informs us importantly about development of disease as we age," said Zonneveld.

Breast density alone may not be cancer risk factor

Contrary to prior research, high breast density may not be a strong independent risk factor for breast cancer. That's the conclusion of a study presented by Natasa Katavic from the Health Center Osijek in Croatia. Katavic and colleagues studied data from 52,962 mammography exams performed in women aged 50 to 69, over five years at five different facilities. Two radiologists read the mammograms independently and determined the women's breast densities according to standard criteria. The majority of screened woman had low breast tissue density (less than 50% parenchyma).

Of the 230 detected breast cancers, almost half were from the group with the lowest ranked breast density, while slightly less than 3% came from women in the highest breast density category. When the researchers matched women with a detected cancer with control participants without cancer, they found no significant difference in mammographic density. Women with low mammographic density had 83% of patients in the breast cancer group, compared with 89% in the control group, while high mammographic density was found in 17% of breast cancer patients and 11% of controls.

"In our study, we found that there was no significant difference in breast density between breast cancer patients and the control group in the screening program," said Katavic, adding that the findings also support mammography as an efficient method for early detection of non-palpable breast cancer.

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