Evaluation of four-dimensional cone beam computed tomography ventilation images acquired with two different linear accelerators at various gantry speeds using a deformable lung phantom

We evaluated four-dimensional cone beam computed tomography (4D-CBCT) ventilation images (VI_CBCT) acquired with two different linear accelerator systems at various gantry speeds using a deformable lung phantom.The 4D-CT and 4D-CBCT scans were performed using a computed tomography (CT) scanner, an X-ray volume imaging system (Elekta XVI) mounted in Versa HD, and an On-Board Imager (OBI) system mounted in TrueBeam. Intensity-based deformable image registration (DIR) was performed between peak-exhale and peak-inhale images. VI_CBCT- and 4D-CT-based ventilation images (VI_CT) were derived by DIR using two metrics: one based on the Jacobian determinant and one on changes in the Hounsfield unit (HU). Three different DIR regularization values (λ) were used for VI_CBCT. Correlations between the VI_CBCT and VI_CT values were evaluated using voxel-wise Spearman’s rank correlation coefficient (r).In case of both metrics, the Jacobian-based VI_CBCT with a gantry speed of 0.6 deg/sec in Versa HD showed the highest correlation for all the gantry speeds (e.g., λ = 0.05 and r = 0.68). Thus, the r value of the Jacobian-based VI_CBCT was greater or equal to that of the HU-based VI_CBCT. In addition, the ventilation accuracy of VI_CBCT increased at low gantry speeds.Thus, the image quality of VI_CBCT was affected by the change in gantry speed in both the imaging systems. Additionally, DIR regularization considerably influenced VI_CBCT in both the imaging systems. Our results have the potential to assist in designing CBCT protocols, incorporating VI_CBCT imaging into the functional avoidance planning process.     

Functional lung imaging with synchrotron radiation: Methods and preclinical applications

Many lung disease processes are characterized by structural and functional heterogeneity that is not directly appreciable with traditional physiological measurements. Experimental methods and lung function modeling to study regional lung function are crucial for better understanding of disease mechanisms and for targeting treatment. Synchrotron radiation offers useful properties to this end: coherence, utilized in phase-contrast imaging, and high flux and a wide energy spectrum which allow the selection of very narrow energy bands of radiation, thus allowing imaging at very specific energies. K-edge subtraction imaging (KES) has thus been developed at synchrotrons for both human and small animal imaging. The unique properties of synchrotron radiation extend X-ray computed tomography (CT) capabilities to quantitatively assess lung morphology, and also to map regional lung ventilation, perfusion, inflammation and biomechanical properties, with microscopic spatial resolution. Four-dimensional imaging, allows the investigation of the dynamics of regional lung functional parameters simultaneously with structural deformation of the lung as a function of time. This review summarizes synchrotron radiation imaging methods and overviews examples of its application in the study of disease mechanisms in preclinical animal models, as well as the potential for clinical translation both through the knowledge gained using these techniques and transfer of imaging technology to laboratory X-ray sources.     

咽喉部高频喷射通气调节各参数对狗肺通气效率的影响

用相关和回归处理方法,研究了8条正常狗咽喉部高频喷射通气时,调节驱动压、呼吸比和频率对喷气量、吸入气氧浓度、动脉血气及气道内压的作用。结果显示,驱动压和呼吸此对各观察指标几乎有同等重要的作用,频率的影响很小,喷气量与吸入气氧浓度、动脉血气、气道内压间存在显著的正相关关系。说明调节参数的意义主要在于改变了喷气量。     

Evidence for ram suspension feeding by the piscivore, Seriola dumerili (Carangidae)

Synopsis We have quantitatively analyzed a videotape of Seriola dumerili (Carangidae) displaying ram suspension-feeding behavior and ram ventilation in the field. This is the first report of facultative suspension feeding by a piscivorous carangid. The intraoral morphology of S. dumerili is not typical of ram suspension-feeding fishes in that closely-spaced, long gill rakers are lacking. While the mechanism of particle retention is not known for any ram suspension-feeding fish species, scanning electron microscopy revealed denticles on the branchial surfaces of S. dumerili that could play a role in particle entrapment.     

Cardiovascular, ventilatory and total activity responses of brown trout to handling stress

Changes in total activity, heart and ventilation rates were observed in 2-year-old brown trout, following handling stress, using non-contact bioelectronic monitoring equipment. Experiments were carried out in laboratory conditions at water temperatures below 4° C, Transfer between tanks as well as 5 min restraint stress increased the total activity of fish for 24 to 48 h, after which it declined to near the pre-stress level. The transfer and struggle both elevated the heart rate for 3 to 4 days. Ventilation rate was elevated to a maximum of about 30% above the nominal level and recovered within 3 to 4 days. Both heart and ventilation rates were higher in feeding fish relative to fasting fish after stress and rates remained higher throughout a 7 day period of recovery. A diel rhythm of lower rates during the night appeared in both heart and ventilation rates within 3 to 4 days after handling stress.     

Otolith microstructure pattern in Oreochromis niloticus (L.)

The microstructure of otoliths from young and old Oreochromis niloticus (L.) were studied. Otoliths were prepared histologically except for those from newly hatched fish. Hatching results in the formation of a check in the otoliths, which appeared 1 day later. Other checks are rare in juvenile otoliths but common in adult otoliths. Faint and non-daily increments were observed within the hatching check. After hatching, increments were deposited daily. Sub-daily increments were faint and narrow, they were present in the area along the dorso-ventral axis of the otolith but did not continue into the lateral region. Discontinuous zones in the medial area appeared different from those in the lateral area. New growth centres were not only found in the juvenile fish otoliths, but also in adult fish otoliths.     

Responses of the teleost Hoplias malabaricus to hypoxia

Synopsis Oxygen uptake (VO₂) during graded hypoxia, rate of hypoxia acclimation, breathing frequency (f_R), breath volume (V_{S, R}) and gill ventilation (V_G) were measured in Hoplias malabaricus. Normoxia and hypoxia acclimated fish had similar and constant VO₂ and V_G in a range of water PO₂ from 150 to 25 mmHg. Hypoxia acclimated fish showed significantly higher VO₂ in severe hypoxia (PO₂ <15 mmHg). Normoxia acclimated fish showed symptoms similar to hypoxic coma after 1 h of exposure to water PO₂ of 10 mmHg whereas the same symptoms were observed only at PO₂ of 5 mmHg for fish acclimated to hypoxia. Fish required 14 days to achieve full acclimation to hypoxia (PO₂ ≥25 mmHg). Lowering of water PO₂ from 150 to 25 mmHg resulted in normoxic fish showing a 3–2 fold increase in V_G. The increase was the result of an elevation in V_{S, R} rather than f_R. Among normoxia acclimated specimens, small fish showed a higher V_G per unit weight than the large ones in both normoxia (PO₂ =150 mmHg) and hypoxia (PO₂ = 15 mmHg). A decrease in the ventilatory requirement (V_G/VO₂) with increased body weight was recorded in hypoxia (PO₂ = 15 mmHg).     

On the conservative nature of the gill filaments of sharks

Synopsis Gill filaments of one highly active and two less active shark species exhibit a conservative morphological scheme including such features as branchial canopies, marginal lamellar projections, and enlarged, discrete outer marginal lamellar channels and lateral lamellar sinuses. The specific spatial orientation of the secondary lamellae respective to one another, the gill filaments, and the interbranchial septa create what appears as one-way interfilament water channels, suggesting the presence of an efficient branchial countercurrent system. It is proposed that the fortified structure of shark gills allows many shark species to ventilate passively without having evolved gill filament modifications as apparently did some highly active teleosts. This in turn may have expedited the evolution of lamnid shark species through pre-adaptation to a swift oceanic lifestyle.     

Carapace movements associated with ventilation and irrigation of the branchial chambers in the semaphore crab,Heloecius cordiformis (Decapoda: Brachyura: Ocypodidae)

Summary Carapace movements in crabs are briefly reviewed. While on land and recirculating branchial water, the Australian semaphore crab Heloecius cordiformis (Decapoda: Ocypodidae), a semi-terrestrial air-breathing mangrove crab, sequentially depresses and elevates its carapace relative to its thorax (0.5–1 mm excursion) in a regular pump-like manner. In quiescent crabs each carapace-pumping cycle lasts about 4 s; carapace depression takes 3 s and elevation 1 s. Carapace movements are brought about by pressures generated within the branchial chambers by the scaphognathites, probably in combination with carapace muscles. Carapace movements are associated with bilaterally synchronised scaphognathite activity. Unilateral scaphognathite activity was not observed. During normal forward recirculation of branchial water the scaphognathites beat at about 1.5 Hz (slow-forward pumping) and the lungs (epibranchial chambers) are not ventilated. In Heloecius, the lungs are not physically separated from the gills below by an anatomical barrier. Lung ventilation is accomplished during the following sequence of events: the carapace is lowered and the scaphognathites pump in a fast-forward mode at about 2.8 Hz. This activity preferentially pumps air out of the lungs and generates suction within the branchial chambers (4–10 cm H₂O below ambient) which draws water from external body surfaces into the hypobranchial space below and around the gills. At the end of the carapace's downward travel the scaphognathites switch from fast-forward to fastreverse beating at about 4 Hz. This pumps air into the lungs and the carapace elevates. As a result, during carapace elevation the water which had previously been drawn into the branchial chambers by fast-forward pumping activity is released and flows out between the legs and into the abdominosternal cavity. When the carapace reaches its original resting or up position the scaphognathites switch from fast-reverse to slowforward beating to re-establish water recirculation through the branchial chambers. This cycle is subsequently repeated. In stationary crabs, there are 2 carapace-pumping cycles per minute, increasing to 14 per minute in active crabs (walking). When water is absent, the lungs are preferentially ventilated by slow-reverse scaphognathite pumping activity. Carapace movements do not occur in the absence of branchial water. Carapace pumping is thought to provide a mechanism which permits the scaphognathites to ventilate the lungs in the presence of recirculating branchial water, without this water interfering with lung ventilation or being lost to the environment.Abbreviations FF, FR, SF, SR fast-forward, fast-reverse, slowforward, slow-reverse scaphognathite pumping - MEA Milne Edwards aperture