In the study, a total of 20 red-eared turtles （ half male and half female） were selected to conduct the measurement of liver size and intrahepatic blood flow of red-eared turtles by color Doppler ultrasound. The res...In the study, a total of 20 red-eared turtles （ half male and half female） were selected to conduct the measurement of liver size and intrahepatic blood flow of red-eared turtles by color Doppler ultrasound. The results showed that the fight hepatic lobe could be scanned through the right carotid anterior acoustic win- dow, and the left hepatic lobe could be scanned through the left carotid anterior acoustic window, but the vision would be obstructed by the air in trachea. The liver could also be scanned through the left femoral anterior acoustic window and the fight femoral anterior acoustic window when filling of bladder was good. The correla- tion regression analysis suggested that estimated values of liver showed no linear relationship with weight, the longest back curve and the widest back curve. Through the study, the normal indicators for ultrasound examination of red-eared turtle liver were established, in order to provide a reference for examination of turtle liver.展开更多
The interest in the liver dates back to ancient times when it was considered to be the seat of life processes. The liver is indeed essential to life,not only due to its complex functions in biosynthesis,metabolism and...The interest in the liver dates back to ancient times when it was considered to be the seat of life processes. The liver is indeed essential to life,not only due to its complex functions in biosynthesis,metabolism and clearance,but also its dramatic role as the blood volume reservoir. Among parenchymal organs,blood flow to the liver is unique due to the dual supply from the portal vein and the hepatic artery. Knowledge of the mutual communication of both the hepatic artery and the portal vein is essential to understand hepatic physiology and pathophysiology. To distinguish the individual importance of each of these inflows in normal and abnormal states is still a challenging task and the subject of on-going research. A central mechanism that controls and allows constancy of hepatic blood flow is the hepatic arterial buffer response. The current paper reviews the relevance of this intimate hepatic blood flow regulatory system in health and disease. We exclusively focus on the endogenous interrelationship between the hepatic arterial and portal venous inflow circuits in liver resection and transplantation,as well as inflammatory and chronic liver diseases. We do not consider the hepatic microvascular anatomy,as this has been the subject of another recent review.展开更多
AIM:To characterize the impact of the Pringle ma-neuver (PM) and ischemic preconditioning (IP) on total blood supply to the liver following hepatectomies. METHODS: Sixty one consecutive patients who un-derwent hepatic...AIM:To characterize the impact of the Pringle ma-neuver (PM) and ischemic preconditioning (IP) on total blood supply to the liver following hepatectomies. METHODS: Sixty one consecutive patients who un-derwent hepatic resection under in flow occlusion were randomized either to receive PM alone (n = 31) or IP (10 min of ischemia followed by 10 min of reperfusion) prior to PM (n = 30). Quantification of liver perfusion was measured by Doppler probes at the hepatic artery and portal vein at various time points after reperfusion of remnant livers. RESULTS: Occlusion times of 33 ± 12 min (mean ± SD) and 34 ± 14 min and the extent of resected liver tissue (2.7 segments) were similar in both groups. In controls (PM), on reperfusion of liver remnants for 15 min, portal perfusion markedly decreased by 29% while there was a slight increase of 8% in the arterial blood flow. In contrast, following IP + PM the portal vein flow remained unchanged during reperfusion and a significantly increased arterial blood flow (+56% vs baseline) was observed. In accordance with a better postischemic blood supply of the liver, hepatocellular injury, as measured by alanine aminotransferase (ALT) levels on day 1 was considerably lower in group B compared to group A (247 ± 210 U/I vs 550 ± 650 U/I, P < 0.05). Additionally, ALT levels were significantly correlated to the hepatic artery in flow.CONCLUSION: IP prevents postischemic flow reduction of the portal vein and simultaneously increases arterial perfusion, suggesting that improved hepatic macrocirculation is a protective mechanism following hepatectomy.展开更多
AIM: To determine intra-hepatic blood flow and liver stiffness in patients with non-alcoholic fatty liver disease(NAFLD) and non-alcoholic steatohepatitis (NASH) using contrast-enhanced ultrasound and fibroscan.METHOD...AIM: To determine intra-hepatic blood flow and liver stiffness in patients with non-alcoholic fatty liver disease(NAFLD) and non-alcoholic steatohepatitis (NASH) using contrast-enhanced ultrasound and fibroscan.METHODS: This prospective study included 15 patients with NAFLD, 17 patients with NASH and 16 healthy controls.In each patient, real-time ultrasound was used to locate the portal vein (PV) and the right liver lobe, and 5 mL of SonoVue? was then injected intravenous in a peripheral vein of the left arm over a 4-s span. Digital recording was performed for 3 min thereafter. The recording was subsequently retrieved to identify an area of interest in the PV area and in the right liver parenchyma(LP) to assess the blood flow by processing the data using dedicated software (Qontrast?, Bracco, Italy).The following parameters were evaluated: percentage of maximal contrast activity (Peak%), time to peak (TTP, s), regional blood volume (RBV, cm3), regional blood flow (RBF, cm3/s) and mean transit time (MTT, s).At 24-48 h post-injection, liver stiffness was evaluated using Fibroscan and measured in kPa. The statistical evaluation was performed using Student’s t test.RESULTS: In the PV, the Peak%, RBV and RBF were significantly reduced in the NAFLD and NASH patientscompared with the controls (Peak%: NAFLD 26.3 ± 6.6,NASH 28.1 ± 7.3 vs controls 55.8 ± 9.9, P < 0.001;RBV: NAFLD 4202.3 ± 3519.7, NASH 3929.8 ± 1941.3vs controls 7473 ± 3281, P < 0.01; RBF: NAFLD 32.5± 10.8, NASH 32.7 ± 12.1 vs controls 73.1 ± 13.9, P< 0.001). The TTP in the PV was longer in both patient groups but reached statistical significance only in the NASH patients compared with the controls (NASH 79.5± 37.8 vs controls 43.2 ± 30, P < 0.01). In the LP,the Peak%, RBV and RBF were significantly reduced in the NAFLD and NASH patients compared with the controls (Peak%: NAFLD 43.2 ± 7.3, NASH 41.7 ± 7.7 vs controls 56.6 ± 6.3, P < 0.001; RBV: NAFLD 4851.5± 2009, NASH 5069.4 ± 2292.5 vs controls 6922.9 ±2461.5, P < 0.05; RBF: NAFLD 55.7 ± 10.1, NASH 54.5 ± 12.1 vs controls 75.9 ± 10.5, P < 0.001). The TTP was longer in both patient groups but did not reach statistical significance. The MTT in both the PV and LP in the NAFLD and NASH patients was not different from that in the controls. Liver stiffness was significantly increased relative to the controls only in the NASH patients(NASH: 6.4 ± 2.2 vs controls 4.6 ± 1.5, P < 0.05).CONCLUSION: Blood flow derangement within the liver present not only in NASH but also in NAFLD suggests that a vascular flow alteration precedes liver fibrosis development.展开更多
Splanchnic circulation is the primary mechanism thatregulates volumes of circulating blood and systemic blood pressure in patients with cirrhosis accompanied by portal hypertension. Recently, interest has been express...Splanchnic circulation is the primary mechanism thatregulates volumes of circulating blood and systemic blood pressure in patients with cirrhosis accompanied by portal hypertension. Recently, interest has been expressed in modulating splanchnic circulation in patients with liver cirrhosis, because this capability might produce beneficial effects in cirrhotic patients undergoing a liver transplant. Pharmacologic modulation of splanchnic circulation by use of vasoconstrictors might minimize venous congestion, replenish central blood flow, and thus optimize management of blood volume during a liver transplant operation. Moreover, splanchnic modulation minimizes any high portal blood flow that may occur following liver resection and the subsequent liver transplant. This effect is significant, because high portal flow impairs liver regeneration, and thus adversely affects the postoperative recovery of a transplant patient. An increase in portal blood flow can be minimized by either surgical methods(e.g., splenic artery ligation, splenectomy or portocaval shunting) or administration of splanchnic vasoconstrictor drugs such as Vasopressin or terlipressin. Finally, modulation of splanchnic circulation can help maintain perioperative renal function. Splanchnic vasoconstrictors such as terlipressin may help protect against acute kidney injury in patients undergoing liver transplantation by reducing portal pressure and the severity of a hyperdynamic state. These effects are especially important in patients who receive a too small for size graft. Terlipressin selectively stimulates V1 receptors, and thus causes arteriolar vasoconstriction in the splanchnic region, with a consequent shift of blood from splanchnic to systemic circulation. As a result, terlipressin enhances renal perfusion by increasing both effective blood volume and mean arterial pressure.展开更多
BACKGROUND Split liver transplantation(SLT)is a complex procedure.The left-lateral and right tri-segment splits are the most common surgical approaches and are based on the Couinaud liver segmentation theory.Notably,t...BACKGROUND Split liver transplantation(SLT)is a complex procedure.The left-lateral and right tri-segment splits are the most common surgical approaches and are based on the Couinaud liver segmentation theory.Notably,the liver surface following right trisegment splits may exhibit different degrees of ischemic changes related to the destruction of the local portal vein blood flow topology.There is currently no consensus on preoperative evaluation and predictive strategy for hepatic segmental necrosis after SLT.AIM To investigate the application of the topological approach in liver segmentation based on 3D visualization technology in the surgical planning of SLT.METHODS Clinical data of 10 recipients and 5 donors who underwent SLT at Shenzhen Third People’s Hospital from January 2020 to January 2021 were retrospectively analyzed.Before surgery,all the donors were subjected to 3D modeling and evaluation.Based on the 3D-reconstructed models,the liver splitting procedure was simulated using the liver segmentation system described by Couinaud and a blood flow topology liver segmentation(BFTLS)method.In addition,the volume of the liver was also quantified.Statistical indexes mainly included the hepatic vasculature and expected volume of split grafts evaluated by 3D models,the actual liver volume,and the ischemia state of the hepatic segments during the actual surgery.RESULTS Among the 5 cases of split liver surgery,the liver was split into a left-lateral segment and right trisegment in 4 cases,while 1 case was split using the left and right half liver splitting.All operations were successfully implemented according to the preoperative plan.According to Couinaud liver segmentation system and BFTLS methods,the volume of the left lateral segment was 359.00±101.57 mL and 367.75±99.73 mL,respectively,while that measured during the actual surgery was 397.50±37.97 mL.The volume of segment IV(the portion of ischemic liver lobes)allocated to the right tri-segment was 136.31±86.10 mL,as determined using the topological approach to liver segmentation.However,during the actual surgical intervention,ischemia of the right tri-segment section was observed in 4 cases,including 1 case of necrosis and bile leakage,with an ischemic liver volume of 238.7 mL.CONCLUSION 3D visualization technology can guide the preoperative planning of SLT and improve accuracy during the intervention.The simulated operation based on 3D visualization of blood flow topology may be useful to predict the degree of ischemia in the liver segment and provide a reference for determining whether the ischemic liver tissue should be removed during the surgery.展开更多
Since its introduction in the 1970’s,magnetic resonance imaging(MRI)has become a standard imaging modality.With its broad and standardized application,it is firmly established in the clinical routine and an essential...Since its introduction in the 1970’s,magnetic resonance imaging(MRI)has become a standard imaging modality.With its broad and standardized application,it is firmly established in the clinical routine and an essential element in cardiovascular and abdominal imaging.In addition to sonography and computer tomography,MRI is a valuable tool for diagnosing cardiovascular and abdominal diseases,for determining disease severity,and for assessing therapeutic success.MRI techniques have improved over the last few decades,revealing not just morphologic information,but functional information about perfusion,diffusion and hemodynamics as well.Four-dimensional(4D)flow MRI,a time-resolved phase contrast-MRI with three-dimensional(3D)anatomic coverage and velocity encoding along all three flow directions has been used to comprehensively assess complex cardiovascular hemodynamics in multiple regions of the body.The technique enables visualization of 3D blood flow patterns and retrospective quantification of blood flow parameters in a region of interest.Over the last few years,4D flow MRI has been increasingly performed in the abdominal region.By applying different acceleration techniques,taking 4D flow MRI measurements has dropped to a reasonable scanning time of 8 to 12 min.These new developments have encouraged a growing number of patient studies in the literature validating the technique’s potential for enhanced evaluation of blood flow parameters within the liver’s complex vascular system.The purpose of this review article is to broaden our understanding of 4D flow MRI for the assessment of liver hemodynamics by providing insights into acquisition,data analysis,visualization and quantification.Furthermore,in this article we highlight its development,focussing on the clinical application of the technique.展开更多
Cerebral oedema is a devastating consequence of acute liver failure(ALF)and may be associated with the development of intracranial hypertension and death.In ALF,some patients may develop cerebral oedema and increased ...Cerebral oedema is a devastating consequence of acute liver failure(ALF)and may be associated with the development of intracranial hypertension and death.In ALF,some patients may develop cerebral oedema and increased intracranial pressure but progression to lifethreatening intracranial hypertension is less frequent than previously described,complicating less than one third of cases who have proceeded to coma since the advent of improved clinical care.The rapid onset of encephalopathy may be dramatic with the development of asterixis,delirium,seizures and coma.Cytotoxic and vasogenic oedema mechanisms have been implicated with a preponderance of experimental data favouring a cytotoxic mechanism.Astrocyte swelling is the most consistent neuropathological finding in humans with ALF and ammonia plays a definitive role in the development of cytotoxic brain oedema.The mechanism(s)by which ammonia induces astrocyte swelling remains unclear but glutamine accumulation within astrocytes has led to the osmolyte hypothesis.Current evidence also supports an alternate‘Trojan horse’hypothesis,with glutamine as a carrier of ammonia into mitochondria,where its accumulation results in oxidative stress,energy failure and ultimately astrocyte swelling.Although a complete breakdown of the blood-brain barrier is not evident in human ALF,increased permeation to water and other small molecules such as ammonia has been demonstrated resulting from subtle alterations in the protein composition of paracellular tight junctions.At present,there is no fully efficacious therapy for cerebral oedema other than liver transplantation and this reflects our incomplete knowledge of the precise mechanisms underlying this process which remain largely unknown.展开更多
文摘In the study, a total of 20 red-eared turtles （ half male and half female） were selected to conduct the measurement of liver size and intrahepatic blood flow of red-eared turtles by color Doppler ultrasound. The results showed that the fight hepatic lobe could be scanned through the right carotid anterior acoustic win- dow, and the left hepatic lobe could be scanned through the left carotid anterior acoustic window, but the vision would be obstructed by the air in trachea. The liver could also be scanned through the left femoral anterior acoustic window and the fight femoral anterior acoustic window when filling of bladder was good. The correla- tion regression analysis suggested that estimated values of liver showed no linear relationship with weight, the longest back curve and the widest back curve. Through the study, the normal indicators for ultrasound examination of red-eared turtle liver were established, in order to provide a reference for examination of turtle liver.
文摘The interest in the liver dates back to ancient times when it was considered to be the seat of life processes. The liver is indeed essential to life,not only due to its complex functions in biosynthesis,metabolism and clearance,but also its dramatic role as the blood volume reservoir. Among parenchymal organs,blood flow to the liver is unique due to the dual supply from the portal vein and the hepatic artery. Knowledge of the mutual communication of both the hepatic artery and the portal vein is essential to understand hepatic physiology and pathophysiology. To distinguish the individual importance of each of these inflows in normal and abnormal states is still a challenging task and the subject of on-going research. A central mechanism that controls and allows constancy of hepatic blood flow is the hepatic arterial buffer response. The current paper reviews the relevance of this intimate hepatic blood flow regulatory system in health and disease. We exclusively focus on the endogenous interrelationship between the hepatic arterial and portal venous inflow circuits in liver resection and transplantation,as well as inflammatory and chronic liver diseases. We do not consider the hepatic microvascular anatomy,as this has been the subject of another recent review.
基金Supported by The Deutsche Forschungsgemeinschaft, No. DFG SCHA 857/1-1
文摘AIM:To characterize the impact of the Pringle ma-neuver (PM) and ischemic preconditioning (IP) on total blood supply to the liver following hepatectomies. METHODS: Sixty one consecutive patients who un-derwent hepatic resection under in flow occlusion were randomized either to receive PM alone (n = 31) or IP (10 min of ischemia followed by 10 min of reperfusion) prior to PM (n = 30). Quantification of liver perfusion was measured by Doppler probes at the hepatic artery and portal vein at various time points after reperfusion of remnant livers. RESULTS: Occlusion times of 33 ± 12 min (mean ± SD) and 34 ± 14 min and the extent of resected liver tissue (2.7 segments) were similar in both groups. In controls (PM), on reperfusion of liver remnants for 15 min, portal perfusion markedly decreased by 29% while there was a slight increase of 8% in the arterial blood flow. In contrast, following IP + PM the portal vein flow remained unchanged during reperfusion and a significantly increased arterial blood flow (+56% vs baseline) was observed. In accordance with a better postischemic blood supply of the liver, hepatocellular injury, as measured by alanine aminotransferase (ALT) levels on day 1 was considerably lower in group B compared to group A (247 ± 210 U/I vs 550 ± 650 U/I, P < 0.05). Additionally, ALT levels were significantly correlated to the hepatic artery in flow.CONCLUSION: IP prevents postischemic flow reduction of the portal vein and simultaneously increases arterial perfusion, suggesting that improved hepatic macrocirculation is a protective mechanism following hepatectomy.
文摘AIM: To determine intra-hepatic blood flow and liver stiffness in patients with non-alcoholic fatty liver disease(NAFLD) and non-alcoholic steatohepatitis (NASH) using contrast-enhanced ultrasound and fibroscan.METHODS: This prospective study included 15 patients with NAFLD, 17 patients with NASH and 16 healthy controls.In each patient, real-time ultrasound was used to locate the portal vein (PV) and the right liver lobe, and 5 mL of SonoVue? was then injected intravenous in a peripheral vein of the left arm over a 4-s span. Digital recording was performed for 3 min thereafter. The recording was subsequently retrieved to identify an area of interest in the PV area and in the right liver parenchyma(LP) to assess the blood flow by processing the data using dedicated software (Qontrast?, Bracco, Italy).The following parameters were evaluated: percentage of maximal contrast activity (Peak%), time to peak (TTP, s), regional blood volume (RBV, cm3), regional blood flow (RBF, cm3/s) and mean transit time (MTT, s).At 24-48 h post-injection, liver stiffness was evaluated using Fibroscan and measured in kPa. The statistical evaluation was performed using Student’s t test.RESULTS: In the PV, the Peak%, RBV and RBF were significantly reduced in the NAFLD and NASH patientscompared with the controls (Peak%: NAFLD 26.3 ± 6.6,NASH 28.1 ± 7.3 vs controls 55.8 ± 9.9, P < 0.001;RBV: NAFLD 4202.3 ± 3519.7, NASH 3929.8 ± 1941.3vs controls 7473 ± 3281, P < 0.01; RBF: NAFLD 32.5± 10.8, NASH 32.7 ± 12.1 vs controls 73.1 ± 13.9, P< 0.001). The TTP in the PV was longer in both patient groups but reached statistical significance only in the NASH patients compared with the controls (NASH 79.5± 37.8 vs controls 43.2 ± 30, P < 0.01). In the LP,the Peak%, RBV and RBF were significantly reduced in the NAFLD and NASH patients compared with the controls (Peak%: NAFLD 43.2 ± 7.3, NASH 41.7 ± 7.7 vs controls 56.6 ± 6.3, P < 0.001; RBV: NAFLD 4851.5± 2009, NASH 5069.4 ± 2292.5 vs controls 6922.9 ±2461.5, P < 0.05; RBF: NAFLD 55.7 ± 10.1, NASH 54.5 ± 12.1 vs controls 75.9 ± 10.5, P < 0.001). The TTP was longer in both patient groups but did not reach statistical significance. The MTT in both the PV and LP in the NAFLD and NASH patients was not different from that in the controls. Liver stiffness was significantly increased relative to the controls only in the NASH patients(NASH: 6.4 ± 2.2 vs controls 4.6 ± 1.5, P < 0.05).CONCLUSION: Blood flow derangement within the liver present not only in NASH but also in NAFLD suggests that a vascular flow alteration precedes liver fibrosis development.
文摘Splanchnic circulation is the primary mechanism thatregulates volumes of circulating blood and systemic blood pressure in patients with cirrhosis accompanied by portal hypertension. Recently, interest has been expressed in modulating splanchnic circulation in patients with liver cirrhosis, because this capability might produce beneficial effects in cirrhotic patients undergoing a liver transplant. Pharmacologic modulation of splanchnic circulation by use of vasoconstrictors might minimize venous congestion, replenish central blood flow, and thus optimize management of blood volume during a liver transplant operation. Moreover, splanchnic modulation minimizes any high portal blood flow that may occur following liver resection and the subsequent liver transplant. This effect is significant, because high portal flow impairs liver regeneration, and thus adversely affects the postoperative recovery of a transplant patient. An increase in portal blood flow can be minimized by either surgical methods(e.g., splenic artery ligation, splenectomy or portocaval shunting) or administration of splanchnic vasoconstrictor drugs such as Vasopressin or terlipressin. Finally, modulation of splanchnic circulation can help maintain perioperative renal function. Splanchnic vasoconstrictors such as terlipressin may help protect against acute kidney injury in patients undergoing liver transplantation by reducing portal pressure and the severity of a hyperdynamic state. These effects are especially important in patients who receive a too small for size graft. Terlipressin selectively stimulates V1 receptors, and thus causes arteriolar vasoconstriction in the splanchnic region, with a consequent shift of blood from splanchnic to systemic circulation. As a result, terlipressin enhances renal perfusion by increasing both effective blood volume and mean arterial pressure.
基金The Third People's Hospital of Shenzhen Scientific Research Project,No.G2021008 and No.G2022008Shenzhen Key Medical Discipline Construction Fund,No.SZXK079Shenzhen Science and Technology Research and Development Fund,No.JCYJ20190809165813331 and No.JCYJ20210324131809027。
文摘BACKGROUND Split liver transplantation(SLT)is a complex procedure.The left-lateral and right tri-segment splits are the most common surgical approaches and are based on the Couinaud liver segmentation theory.Notably,the liver surface following right trisegment splits may exhibit different degrees of ischemic changes related to the destruction of the local portal vein blood flow topology.There is currently no consensus on preoperative evaluation and predictive strategy for hepatic segmental necrosis after SLT.AIM To investigate the application of the topological approach in liver segmentation based on 3D visualization technology in the surgical planning of SLT.METHODS Clinical data of 10 recipients and 5 donors who underwent SLT at Shenzhen Third People’s Hospital from January 2020 to January 2021 were retrospectively analyzed.Before surgery,all the donors were subjected to 3D modeling and evaluation.Based on the 3D-reconstructed models,the liver splitting procedure was simulated using the liver segmentation system described by Couinaud and a blood flow topology liver segmentation(BFTLS)method.In addition,the volume of the liver was also quantified.Statistical indexes mainly included the hepatic vasculature and expected volume of split grafts evaluated by 3D models,the actual liver volume,and the ischemia state of the hepatic segments during the actual surgery.RESULTS Among the 5 cases of split liver surgery,the liver was split into a left-lateral segment and right trisegment in 4 cases,while 1 case was split using the left and right half liver splitting.All operations were successfully implemented according to the preoperative plan.According to Couinaud liver segmentation system and BFTLS methods,the volume of the left lateral segment was 359.00±101.57 mL and 367.75±99.73 mL,respectively,while that measured during the actual surgery was 397.50±37.97 mL.The volume of segment IV(the portion of ischemic liver lobes)allocated to the right tri-segment was 136.31±86.10 mL,as determined using the topological approach to liver segmentation.However,during the actual surgical intervention,ischemia of the right tri-segment section was observed in 4 cases,including 1 case of necrosis and bile leakage,with an ischemic liver volume of 238.7 mL.CONCLUSION 3D visualization technology can guide the preoperative planning of SLT and improve accuracy during the intervention.The simulated operation based on 3D visualization of blood flow topology may be useful to predict the degree of ischemia in the liver segment and provide a reference for determining whether the ischemic liver tissue should be removed during the surgery.
文摘Since its introduction in the 1970’s,magnetic resonance imaging(MRI)has become a standard imaging modality.With its broad and standardized application,it is firmly established in the clinical routine and an essential element in cardiovascular and abdominal imaging.In addition to sonography and computer tomography,MRI is a valuable tool for diagnosing cardiovascular and abdominal diseases,for determining disease severity,and for assessing therapeutic success.MRI techniques have improved over the last few decades,revealing not just morphologic information,but functional information about perfusion,diffusion and hemodynamics as well.Four-dimensional(4D)flow MRI,a time-resolved phase contrast-MRI with three-dimensional(3D)anatomic coverage and velocity encoding along all three flow directions has been used to comprehensively assess complex cardiovascular hemodynamics in multiple regions of the body.The technique enables visualization of 3D blood flow patterns and retrospective quantification of blood flow parameters in a region of interest.Over the last few years,4D flow MRI has been increasingly performed in the abdominal region.By applying different acceleration techniques,taking 4D flow MRI measurements has dropped to a reasonable scanning time of 8 to 12 min.These new developments have encouraged a growing number of patient studies in the literature validating the technique’s potential for enhanced evaluation of blood flow parameters within the liver’s complex vascular system.The purpose of this review article is to broaden our understanding of 4D flow MRI for the assessment of liver hemodynamics by providing insights into acquisition,data analysis,visualization and quantification.Furthermore,in this article we highlight its development,focussing on the clinical application of the technique.
基金Supported by Medical Research Council(MRC)Centre for Transplantation,King’s College London,United Kingdom-MRC grant No.MR/J006742/1The National Institute for Health Research(NIHR)Biomedical Research Centre based at Guy’s and St Thomas’NHS Foundation Trust and King’s College London
文摘Cerebral oedema is a devastating consequence of acute liver failure(ALF)and may be associated with the development of intracranial hypertension and death.In ALF,some patients may develop cerebral oedema and increased intracranial pressure but progression to lifethreatening intracranial hypertension is less frequent than previously described,complicating less than one third of cases who have proceeded to coma since the advent of improved clinical care.The rapid onset of encephalopathy may be dramatic with the development of asterixis,delirium,seizures and coma.Cytotoxic and vasogenic oedema mechanisms have been implicated with a preponderance of experimental data favouring a cytotoxic mechanism.Astrocyte swelling is the most consistent neuropathological finding in humans with ALF and ammonia plays a definitive role in the development of cytotoxic brain oedema.The mechanism(s)by which ammonia induces astrocyte swelling remains unclear but glutamine accumulation within astrocytes has led to the osmolyte hypothesis.Current evidence also supports an alternate‘Trojan horse’hypothesis,with glutamine as a carrier of ammonia into mitochondria,where its accumulation results in oxidative stress,energy failure and ultimately astrocyte swelling.Although a complete breakdown of the blood-brain barrier is not evident in human ALF,increased permeation to water and other small molecules such as ammonia has been demonstrated resulting from subtle alterations in the protein composition of paracellular tight junctions.At present,there is no fully efficacious therapy for cerebral oedema other than liver transplantation and this reflects our incomplete knowledge of the precise mechanisms underlying this process which remain largely unknown.
