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The use of Diagnostic Imaging for Identifying Abnormal Gas Accumulations in Cetaceans and Pinnipeds.

Dennison S, Fahlman A, Moore M - Front Physiol (2012)

Bottom Line: Lung compression and alveolar collapse that terminate gas-exchange before a depth is reached where supersaturation is significant and bradycardia with peripheral vasoconstriction affecting the distribution, and dynamics of blood and tissue nitrogen levels.Published accounts of gas and fat emboli and dysbaric osteonecrosis in marine mammals and theoretical modeling have challenged this view-point, suggesting that decompression-like symptoms may occur under certain circumstances, contrary to common belief.The presence of gas may be asymptomatic and must be interpreted cautiously alongside all other available data including clinical examination, clinical laboratory testing, gas analysis, necropsy examination, and histology results.

View Article: PubMed Central - PubMed

Affiliation: Marine Mammal Radiology San Francisco, CA, USA.

ABSTRACT
Recent dogma suggested that marine mammals are not at risk of decompression sickness due to a number of evolutionary adaptations. Several proposed adaptations exist. Lung compression and alveolar collapse that terminate gas-exchange before a depth is reached where supersaturation is significant and bradycardia with peripheral vasoconstriction affecting the distribution, and dynamics of blood and tissue nitrogen levels. Published accounts of gas and fat emboli and dysbaric osteonecrosis in marine mammals and theoretical modeling have challenged this view-point, suggesting that decompression-like symptoms may occur under certain circumstances, contrary to common belief. Diagnostic imaging modalities are invaluable tools for the non-invasive examination of animals for evidence of gas and have been used to demonstrate the presence of incidental decompression-related renal gas accumulations in some stranded cetaceans. Diagnostic imaging has also contributed to the recognition of clinically significant gas accumulations in live and dead cetaceans and pinnipeds. Understanding the appropriate application and limitations of the available imaging modalities is important for accurate interpretation of results. The presence of gas may be asymptomatic and must be interpreted cautiously alongside all other available data including clinical examination, clinical laboratory testing, gas analysis, necropsy examination, and histology results.

No MeSH data available.


Related in: MedlinePlus

B-mode ultrasound image from a live-stranded common dolphin (Delphinus delphis). Reverberation artifact of normal lung. Some of the liver is seen on the left side of the images. The gas within the periphery of the lung causes near perfect reflection of the sound beam. The result is a repeated, equally spaced hyperechoic line (bright) being displayed on the image (arrows).
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Figure 1: B-mode ultrasound image from a live-stranded common dolphin (Delphinus delphis). Reverberation artifact of normal lung. Some of the liver is seen on the left side of the images. The gas within the periphery of the lung causes near perfect reflection of the sound beam. The result is a repeated, equally spaced hyperechoic line (bright) being displayed on the image (arrows).

Mentions: Diagnostic ultrasound utilizes sound in the realm of 2–20 MHz. The sound beam produced by the piezoelectric transducer penetrates the patient and is reflected at interfaces created by different structures or substances. The proportion of the sound beam reflected is relative to the differences in acoustic impedance of the substances at interfaces (Zagzebski, 1996; Drost, 2007). The greatest difference in acoustic impedance is created at gas-fluid and gas-tissue interfaces and results in near perfect reflection of the sound beam. This causes specific artifacts to be created and displayed on the gray-scale image (Zagzebski, 1996). In the case of large accumulations of gas, reverberation artifacts with equally spaced repetitive bright lines are observed, Figure 1. Furthermore, gas bubbles present as a foam produce a specific subtype of reverberation artifact referred to as ring-down artifact, Figure 2, where sound bounces between the small gas bubbles before finally being reflected back to the transducer. This artifact is identified by a lack of tapering toward the bottom of the image. Larger gas bubbles present as individuals or in small clusters are often observed as bright foci on the image and may or may not produce reverberation artifact (Kirberger, 1995; Feldman et al., 2009). B-mode ultrasound can be used to detect both stationary and moving gas bubbles.


The use of Diagnostic Imaging for Identifying Abnormal Gas Accumulations in Cetaceans and Pinnipeds.

Dennison S, Fahlman A, Moore M - Front Physiol (2012)

B-mode ultrasound image from a live-stranded common dolphin (Delphinus delphis). Reverberation artifact of normal lung. Some of the liver is seen on the left side of the images. The gas within the periphery of the lung causes near perfect reflection of the sound beam. The result is a repeated, equally spaced hyperechoic line (bright) being displayed on the image (arrows).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3368393&req=5

Figure 1: B-mode ultrasound image from a live-stranded common dolphin (Delphinus delphis). Reverberation artifact of normal lung. Some of the liver is seen on the left side of the images. The gas within the periphery of the lung causes near perfect reflection of the sound beam. The result is a repeated, equally spaced hyperechoic line (bright) being displayed on the image (arrows).
Mentions: Diagnostic ultrasound utilizes sound in the realm of 2–20 MHz. The sound beam produced by the piezoelectric transducer penetrates the patient and is reflected at interfaces created by different structures or substances. The proportion of the sound beam reflected is relative to the differences in acoustic impedance of the substances at interfaces (Zagzebski, 1996; Drost, 2007). The greatest difference in acoustic impedance is created at gas-fluid and gas-tissue interfaces and results in near perfect reflection of the sound beam. This causes specific artifacts to be created and displayed on the gray-scale image (Zagzebski, 1996). In the case of large accumulations of gas, reverberation artifacts with equally spaced repetitive bright lines are observed, Figure 1. Furthermore, gas bubbles present as a foam produce a specific subtype of reverberation artifact referred to as ring-down artifact, Figure 2, where sound bounces between the small gas bubbles before finally being reflected back to the transducer. This artifact is identified by a lack of tapering toward the bottom of the image. Larger gas bubbles present as individuals or in small clusters are often observed as bright foci on the image and may or may not produce reverberation artifact (Kirberger, 1995; Feldman et al., 2009). B-mode ultrasound can be used to detect both stationary and moving gas bubbles.

Bottom Line: Lung compression and alveolar collapse that terminate gas-exchange before a depth is reached where supersaturation is significant and bradycardia with peripheral vasoconstriction affecting the distribution, and dynamics of blood and tissue nitrogen levels.Published accounts of gas and fat emboli and dysbaric osteonecrosis in marine mammals and theoretical modeling have challenged this view-point, suggesting that decompression-like symptoms may occur under certain circumstances, contrary to common belief.The presence of gas may be asymptomatic and must be interpreted cautiously alongside all other available data including clinical examination, clinical laboratory testing, gas analysis, necropsy examination, and histology results.

View Article: PubMed Central - PubMed

Affiliation: Marine Mammal Radiology San Francisco, CA, USA.

ABSTRACT
Recent dogma suggested that marine mammals are not at risk of decompression sickness due to a number of evolutionary adaptations. Several proposed adaptations exist. Lung compression and alveolar collapse that terminate gas-exchange before a depth is reached where supersaturation is significant and bradycardia with peripheral vasoconstriction affecting the distribution, and dynamics of blood and tissue nitrogen levels. Published accounts of gas and fat emboli and dysbaric osteonecrosis in marine mammals and theoretical modeling have challenged this view-point, suggesting that decompression-like symptoms may occur under certain circumstances, contrary to common belief. Diagnostic imaging modalities are invaluable tools for the non-invasive examination of animals for evidence of gas and have been used to demonstrate the presence of incidental decompression-related renal gas accumulations in some stranded cetaceans. Diagnostic imaging has also contributed to the recognition of clinically significant gas accumulations in live and dead cetaceans and pinnipeds. Understanding the appropriate application and limitations of the available imaging modalities is important for accurate interpretation of results. The presence of gas may be asymptomatic and must be interpreted cautiously alongside all other available data including clinical examination, clinical laboratory testing, gas analysis, necropsy examination, and histology results.

No MeSH data available.


Related in: MedlinePlus