Objective To investigate the feasibility of acquiring the similar homogeneous enhancement using bolus-tracking techniques with shortened respiratory time in prospectively electrocardiogram-gated high-pitch spiral acqu...Objective To investigate the feasibility of acquiring the similar homogeneous enhancement using bolus-tracking techniques with shortened respiratory time in prospectively electrocardiogram-gated high-pitch spiral acquisition mode (Flash mode) coronary computed tomography angiography (CCTA) compared with test bolus technique. Methods One hundred and eighty-four consecutive patients with mean heart rate ≤65 beats per minute undergoing CCTA were prospectively included in this study. The patients were randomly divided into two groups. Patients in the group A (n=92) instructed to shorten respiratory time received CCTA using bolus-tracking technique with high-pitch spiral acquisition mode (Flash mode), while those in the group B (n=92) underwent CCTA with test bolus technique. The attenuation in the ascending aorta, image noise, contrast-to-noise ratio and radiation doses of the two groups were assessed. Results There were no significant differences in the mean attenuation values in the ascending aorta (483.18±59.07 HU vs. 498.7±83.51 HU, P=0.183), image noise (21.4±4.5 HU vs. 20.9±4.3 HU, P=0.414), contrast-to-noise ratio (12.1±4.2 vs. 13.8±5.1, P=0.31) between the groups A and B. There were no significant differences in the radiation dose of dynamic monitoring scans (0.056±0.026 mSv vs. 0.062±0.018 mSv, P=0.068) and radiation dose of angiography (0.94±0.07 mSv vs. 0.96±0.15 mSv,P=0.926) between the two groups, while 15 mL less contrast material volume was administered in the group A than the group B. Conclusion Bolus-tracking technique with shortened time of respiratory in Flash mode of dual-source CT yields the similar homogeneous enhancement with less contrast material in comparison to the test bolus technique.展开更多
Purpose: The main objective of the study was to evaluate the effect of air gaps of 0 - 5.0 cm between bolus and skin for 1.0 cm Superflab bolus on surface dose (DSurf) and depth of maximum dose (dmax) in solid water a...Purpose: The main objective of the study was to evaluate the effect of air gaps of 0 - 5.0 cm between bolus and skin for 1.0 cm Superflab bolus on surface dose (DSurf) and depth of maximum dose (dmax) in solid water and Rando? phantoms. Methods: In this work, the effects of bolus to surface distance on DSurf and variation in dmax were analyzed in a solid water phantom and in an anthropomorphic Rando? phantom for different field sizes, using Gafchromic? EBT films and farmer chamber. Results: For field sizes of 5 × 5 cm2 the DSurf is significantly affected by increasing air gaps greater than 5 mm. For field sizes larger than 10 × 10 cm2, DSurf is nearly the same for air gaps of 0 - 5.0 cm. For small fields and 6 MV photon beam, dmax increases with increasing air gap, while for 10 MV beam and smaller field sizes (i.e. 5 × 5 and 10 × 10 cm2) the dmax first decreases and then increases with the air gaps. For both 3DCRT and IMRT plans on Rando?, DSurf reduction is more prominent with increasing air gaps. Conclusion: For field sizes larger than 10 × 10 cm2 DSurf is largely unaffected by air gaps. However, smaller air gap results in shallower dmax for both 6 MV and 10 MV photon beams at all fields sizes. Special consideration should be taken to reduce air gaps between bolus and skin for field sizes smaller than 10 × 10 cm2 or when surface contour variations are greater or when the bolus covers small area and at the border of the field.展开更多
Fluid mechanical peristaltic transport through esophagus is studied in the paper. A mathematical model has been developed to study the peristaltic transport of a rheological fluid for arbitrary wave shapes and tube le...Fluid mechanical peristaltic transport through esophagus is studied in the paper. A mathematical model has been developed to study the peristaltic transport of a rheological fluid for arbitrary wave shapes and tube lengths. The Ostwald-de Waele power law of a viscous fluid is considered here to depict the non-Newtonian behaviour of the fluid. The model is formulated and analyzed specifically to explore some important information concerning the movement of food bolus through esophagus. The analysis is carried out by using the lubrication theory. The study is particularly suitable for the cases where the Reynolds number is small. The esophagus is treated as a circular tube through which the transport of food bolus takes place by periodic contraction of the esophageal wall. Variation of different variables concerned with the transport phenomena such as pressure, flow velocities, particle trajectory, and reflux is investigated for a single wave as well as a train of periodic peristaltic waves. The locally variable pressure is seen to be highly sensitive to the flow index ＂n＂. The study clearly shows that continuous fluid transport for Newtonian/rheological fluids by wave train propagation is more effective than widely spaced single wave propagation in the case of peristaltic movement of food bolus in the esophagus.展开更多
Since the development of the new Austrian tunnelling method(NATM)in the 1960s,this technique has been applied successfully in many tunnels.However,opinions of NATM principles emerged till 2000,i.e.NATM is not a tunnel...Since the development of the new Austrian tunnelling method(NATM)in the 1960s,this technique has been applied successfully in many tunnels.However,opinions of NATM principles emerged till 2000,i.e.NATM is not a tunnelling method,but an approach covering all general principles of tunnelling.To investigate the general principles of the NATM,this study focused on tunnelling practises in the Bolu tunnel,and evaluated the conditions under which the NATM practises could be effective.The Bolu tunnel project was designed following the NATM principles.It is evident that practises adopted in this tunnel are important with respect to the NATM.In addition,it shows that the solutions to the problems encountered in this tunnel are consistent with the NATM principles.Finally,the study determines the ground types of the NATM principles and proposes associated updates.展开更多
Chief ComponentsPenis and testes of the ursine seal(Penis etTestes Callorhini)Penis of the deer(Penis Cervi)Penis and testes of the dog(Penis et TestesCanis)
AIM: To assess the impact of bolus volume on the characteristics of small intestinal (SI) impedance signals.METHODS: Concurrent SI manometry-impedance measurements were performed on 12 healthy volunteers to assess the...AIM: To assess the impact of bolus volume on the characteristics of small intestinal (SI) impedance signals.METHODS: Concurrent SI manometry-impedance measurements were performed on 12 healthy volunteers to assess the pattern of proximal jejunal fluid bolus movement over a 14 cm-segment.Each subject was given 34 boluses of normal saline (volume from 1 to 30 mL) via the feeding tube placed immediately above the proximal margin of the studied segment.A bolus-induced impedance event occurred if there was > 12% impedance drop from baseline,over ≥ 3 consecutive segments within 10 s of bolus injection.A minor or major imped-ance event was defined as a duration of impedance drop < 60 s or ≥ 60 s,respectively.RESULTS: The minimum volume required for a detectable SI impedance event was 2 mL.A direct linear relationship between the SI bolus volume and the occurrence of impedance events was noted until SI bolus volume reached 10 mL,a volume which always produced an impedance flow event.There was a moderate correlation between the bolus volume and the duration of impedance drop (r = 0.63,P < 0.0001) and the number of propagated channels (r = 0.50,P < 0.0001).High volume boluses were associated with more major impedance events (≥ 10 mL boluses = 63%,3 mL boluses = 17%,and < 3 mL boluses = 0%,P = 0.02).CONCLUSION: Bolus volume had an impact on the type and length of propagation of SI impedance events and a threshold of 2 mL is required to produce an event.展开更多
基金Supported by the Ministry of Science and Technology of Inner Mongolia, China (20110504)
文摘Objective To investigate the feasibility of acquiring the similar homogeneous enhancement using bolus-tracking techniques with shortened respiratory time in prospectively electrocardiogram-gated high-pitch spiral acquisition mode (Flash mode) coronary computed tomography angiography (CCTA) compared with test bolus technique. Methods One hundred and eighty-four consecutive patients with mean heart rate ≤65 beats per minute undergoing CCTA were prospectively included in this study. The patients were randomly divided into two groups. Patients in the group A (n=92) instructed to shorten respiratory time received CCTA using bolus-tracking technique with high-pitch spiral acquisition mode (Flash mode), while those in the group B (n=92) underwent CCTA with test bolus technique. The attenuation in the ascending aorta, image noise, contrast-to-noise ratio and radiation doses of the two groups were assessed. Results There were no significant differences in the mean attenuation values in the ascending aorta (483.18±59.07 HU vs. 498.7±83.51 HU, P=0.183), image noise (21.4±4.5 HU vs. 20.9±4.3 HU, P=0.414), contrast-to-noise ratio (12.1±4.2 vs. 13.8±5.1, P=0.31) between the groups A and B. There were no significant differences in the radiation dose of dynamic monitoring scans (0.056±0.026 mSv vs. 0.062±0.018 mSv, P=0.068) and radiation dose of angiography (0.94±0.07 mSv vs. 0.96±0.15 mSv,P=0.926) between the two groups, while 15 mL less contrast material volume was administered in the group A than the group B. Conclusion Bolus-tracking technique with shortened time of respiratory in Flash mode of dual-source CT yields the similar homogeneous enhancement with less contrast material in comparison to the test bolus technique.
文摘Purpose: The main objective of the study was to evaluate the effect of air gaps of 0 - 5.0 cm between bolus and skin for 1.0 cm Superflab bolus on surface dose (DSurf) and depth of maximum dose (dmax) in solid water and Rando? phantoms. Methods: In this work, the effects of bolus to surface distance on DSurf and variation in dmax were analyzed in a solid water phantom and in an anthropomorphic Rando? phantom for different field sizes, using Gafchromic? EBT films and farmer chamber. Results: For field sizes of 5 × 5 cm2 the DSurf is significantly affected by increasing air gaps greater than 5 mm. For field sizes larger than 10 × 10 cm2, DSurf is nearly the same for air gaps of 0 - 5.0 cm. For small fields and 6 MV photon beam, dmax increases with increasing air gap, while for 10 MV beam and smaller field sizes (i.e. 5 × 5 and 10 × 10 cm2) the dmax first decreases and then increases with the air gaps. For both 3DCRT and IMRT plans on Rando?, DSurf reduction is more prominent with increasing air gaps. Conclusion: For field sizes larger than 10 × 10 cm2 DSurf is largely unaffected by air gaps. However, smaller air gap results in shallower dmax for both 6 MV and 10 MV photon beams at all fields sizes. Special consideration should be taken to reduce air gaps between bolus and skin for field sizes smaller than 10 × 10 cm2 or when surface contour variations are greater or when the bolus covers small area and at the border of the field.
基金the Council of Scientific and Industrial Research (CSIR) of New Delhi for awarding him a scientific research fund
文摘Fluid mechanical peristaltic transport through esophagus is studied in the paper. A mathematical model has been developed to study the peristaltic transport of a rheological fluid for arbitrary wave shapes and tube lengths. The Ostwald-de Waele power law of a viscous fluid is considered here to depict the non-Newtonian behaviour of the fluid. The model is formulated and analyzed specifically to explore some important information concerning the movement of food bolus through esophagus. The analysis is carried out by using the lubrication theory. The study is particularly suitable for the cases where the Reynolds number is small. The esophagus is treated as a circular tube through which the transport of food bolus takes place by periodic contraction of the esophageal wall. Variation of different variables concerned with the transport phenomena such as pressure, flow velocities, particle trajectory, and reflux is investigated for a single wave as well as a train of periodic peristaltic waves. The locally variable pressure is seen to be highly sensitive to the flow index ＂n＂. The study clearly shows that continuous fluid transport for Newtonian/rheological fluids by wave train propagation is more effective than widely spaced single wave propagation in the case of peristaltic movement of food bolus in the esophagus.
基金General Directorate of Highways(KGM)for their supports。
文摘Since the development of the new Austrian tunnelling method(NATM)in the 1960s,this technique has been applied successfully in many tunnels.However,opinions of NATM principles emerged till 2000,i.e.NATM is not a tunnelling method,but an approach covering all general principles of tunnelling.To investigate the general principles of the NATM,this study focused on tunnelling practises in the Bolu tunnel,and evaluated the conditions under which the NATM practises could be effective.The Bolu tunnel project was designed following the NATM principles.It is evident that practises adopted in this tunnel are important with respect to the NATM.In addition,it shows that the solutions to the problems encountered in this tunnel are consistent with the NATM principles.Finally,the study determines the ground types of the NATM principles and proposes associated updates.
文摘Chief ComponentsPenis and testes of the ursine seal(Penis etTestes Callorhini)Penis of the deer(Penis Cervi)Penis and testes of the dog(Penis et TestesCanis)
基金Supported by The National Health and Medical Research Council of Australia
文摘AIM: To assess the impact of bolus volume on the characteristics of small intestinal (SI) impedance signals.METHODS: Concurrent SI manometry-impedance measurements were performed on 12 healthy volunteers to assess the pattern of proximal jejunal fluid bolus movement over a 14 cm-segment.Each subject was given 34 boluses of normal saline (volume from 1 to 30 mL) via the feeding tube placed immediately above the proximal margin of the studied segment.A bolus-induced impedance event occurred if there was > 12% impedance drop from baseline,over ≥ 3 consecutive segments within 10 s of bolus injection.A minor or major imped-ance event was defined as a duration of impedance drop < 60 s or ≥ 60 s,respectively.RESULTS: The minimum volume required for a detectable SI impedance event was 2 mL.A direct linear relationship between the SI bolus volume and the occurrence of impedance events was noted until SI bolus volume reached 10 mL,a volume which always produced an impedance flow event.There was a moderate correlation between the bolus volume and the duration of impedance drop (r = 0.63,P < 0.0001) and the number of propagated channels (r = 0.50,P < 0.0001).High volume boluses were associated with more major impedance events (≥ 10 mL boluses = 63%,3 mL boluses = 17%,and < 3 mL boluses = 0%,P = 0.02).CONCLUSION: Bolus volume had an impact on the type and length of propagation of SI impedance events and a threshold of 2 mL is required to produce an event.
