Improving coronary ultrafast Doppler angiography using fractional moving blood volume and motion-adaptive ensemble length.

Coronary microperfusion assessment is a key parameter for understanding cardiac function. Currently, coronary ultrafast Doppler angiography is the only non-invasive clinical imaging technique able to assess coronary microcirculation quantitatively in humans. In this study, we propose to use fractional moving blood volume (FMBV), proportional to the red blood cell concentration, as a metric for perfusion. FMBV compares the power Doppler in a region of interest (ROI) inside the myocardium to the power Doppler of a reference area in the heart chamber, fully filled with blood. This normalization gives then relative values of the ROI blood filling. However, due to the impact of ultrasound attenuation and elevation focus on power Doppler values, the reference area and the ROI need to be at the same depth to allow this normalization. This condition is rarely satisfiedin vivodue to the cardiac anatomy. Hereby, we propose to locally compensate the attenuation between the ROI and the reference, by measuring the attenuation law on a phantom. We quantified the efficiency of this approach by comparing FMBV with and without compensation on a flow phantom. Compensated FMBV was able to estimate the ground-truth FMBV with less than 5% variation. This method was then adapted to thein vivocase of myocardial perfusion imaging during heart surgery on human neonates. The translation fromin vitrotoin vivorequired an additional clutter filtering step to ensure that blood signals could be correctly identified in the fast-moving myocardium. We applied the singular value decomposition filter on temporal sliding windows whose lengths were a function of myocardium motion. This motion-adaptive temporal sliding window approach was able to improve blood and tissue separation in terms of contrast-to-noise ratio, as compared to well-established constant-length sliding window approaches. Therefore, compensated FMBV and singular value decomposition assisted with motion-adaptive temporal sliding windows improves the quantification of blood volume in coronary ultrafast Doppler angiography.

In vivo real-time cavitation imaging in moving organs.

The stochastic nature of cavitation implies visualization of the cavitation cloud in real-time and in a discriminative manner for the safe use of focused ultrasound therapy. This visualization is sometimes possible with standard echography, but it strongly depends on the quality of the scanner, and is hindered by difficulty in discriminating from highly reflecting tissue signals in different organs. A specific approach would then permit clear validation of the cavitation position and activity. Detecting signals from a specific source with high sensitivity is a major problem in ultrasound imaging. Based on plane or diverging wave sonications, ultrafast ultrasonic imaging dramatically increases temporal resolution, and the larger amount of acquired data permits increased sensitivity in Doppler imaging. Here, we investigate a spatiotemporal singular value decomposition of ultrafast radiofrequency data to discriminate bubble clouds from tissue based on their different spatiotemporal motion and echogenicity during histotripsy. We introduce an automation to determine the parameters of this filtering. This method clearly outperforms standard temporal filtering techniques with a bubble to tissue contrast of at least 20 dB in vitro in a moving phantom and in vivo in porcine liver.

["Sunshine at school": a network for training on sun exposure. Assessment of knowledge among 683 children]. / Le soleil à l'école: réseau d'éducation à l'exposition solaire. Evaluation des connaissances chez 683 enfants de CM1 et CM2.

INTRODUCTION: The protection of children from sun exposure appears inadequate. We assessed the knowledge of pre-teenagers, before and after they attended a training session on sun exposure. This investigation was carried out in Orléans and in 5 surrounding cities, from September 2000 to April 2002. MATERIAL AND METHODS: A didactic slide show on sun exposure and photoprotection was presented to 683 children in grade 4 and 5 by a nurse and a dermatologist during 30 informative sessions. The children filled in questionnaires at each training session and then one month later. The questionnaires contained 10 closed questions involving 32 cognitive and behavioral items. RESULTS: Forty-five percent of the children claimed that they were exposed to the sun more than one hour a day during holidays, 14 p. 100 more than 3 hours a day; 26 p. 100 declared they had never been sunburnt; 46 p. 100 said they had been less than 5 times, 15 p. 100 from 5 to 10 times and 12 p. 100 more than 10 times; 74 p. 100 of the children claimed they enjoyed getting sun-tanned; 80 p. 100 knew that sun exposure could lead to serious diseases, while 73 p. 100 realized that contracting sunburns during childhood increases the risk of subsequent skin cancers; 89 p. 100 knew of the necessity of sun-screen use prior to exposure, 94 p. 100 knew that they help to protect the skin whereas 78 p. 100 knew it must be applied on a regular basis; 77 p. 100 of the children had been informed of the importance of sun protection factor; 92 p. 100 of them were aware of the relevance of a cap and sunglasses for protection from the sun, whereas only 45 p. 100 knew of the need for a tee-shirt. DISCUSSION: Our study showed that children are generally aware of the dangers of sun exposure. This might be the result of previously initiated information and prevention campaigns on skin cancers. This study suggests the efficiency of such projects, and the lasting effects of the information received within one month. However, large numbers of children are still overexposed and subsequently suffer from traumas. The appeal of sun embellishment appears to go back to childhood, and should be taken into account from the early stages of childhood in future preventive actions. An efficient policy of education on sun exposure - including teaching tools relevant to each age--still has to be developed.