Recognize life threatening causes of altered contrast dynamics such as cardiac asystole. As such, it is often described by a power-law model. WebUltrasound demonstrated a sonographically normal liver without nodularity or cirrhosis and patent hepatic vasculature ( Fig. In. 7c). official website and that any information you provide is encrypted We studied 50 patients with cirrhosis and portal hypertension as evidenced by the demonstration of esophageal varices on endoscopy. On the contrary, the blood flowing in reaches first the smallest liver units, the lobules, before flowing out through the hepatic veins and then the vena cava inferior. Insights Imaging 5(6):731742, Liu KL, Wang YF, Chang YC, Huang SC, Chen SJ, Tsang YM et al (2014) Multislice CT scans in patients on extracorporeal membrane oxygenation: emphasis on hemodynamic changes and imaging pitfalls. Wechsatol et al.26 showed that they happen because they are the most efficient way, i.e. WebA patent paraumbilical vein (PUV) is a frequent finding in patients with cirrhosis when studied by duplex Doppler ultrasound. Lower (4060KeV) monoenergetic reconstruction can be obtained to boost contrast opacification. Leading to the sinusoid pressure drop ratio between a square and a hexagonal lobule: Finally, we conclude that the overall pressure losses will be smaller in the case of the assembly of hexagonal lobules (Eq. The blood transport through the lobules behaves like a flow through a porous system which predicted overall permeability agrees with data available in the literature. Mitral valvular opening and left atrial contraction ensure onward flow of blood/contrast bolus into the left ventricle; systolic contraction of the left ventricle further propels blood/contrast bolus into the aorta and its branches. Note the complete nonopacification of false lumen. However, if the study is not salvageable or if no contrast went into the area of interest, the study will have to be repeated. Understanding the type of CT scanner used is important as scan parameters such as transit time, acquisition time, applied kVp and mAs may differ between scanners. Cardiomyopathy resulting in poor contrast opacification of the left atrium, left ventricle and aorta on a thoracic CTA being obtained to evaluate for pulmonary embolism on a 64 slice CT. CECT demonstrates excellent opacification of the right heart, but poor opacification in the left heart related to prolonged pulmonary circulation time in a patient with left ventricular systolic dysfunction. Clin Radiol 69(12):12641272, Article Khadir MM, Chaturvedi A, Nguyen MS, Wandtke JC, Hobbs S, Chaturvedi A (2014) Looking beyond the thrombus: essentials of pulmonary artery imaging on CT. The hepatic artery provides oxygenated blood to the liver, while the portal vein brings deoxygenated blood; the two mix in the sinusoids. Patent paraumbilical and abdominal subcutaneous veins are found frequently as collaterals in patients due to portal hypertension, mainly associated with liver The hexagonal cross section shows 6 portal triads made of the bile duct, the portal vein and the hepatic artery. Patient with cardiac arrest at the time of CTA for acute aortic syndrome. The patient is instructed to seek medical attention if new neurologic or circulatory symptoms or skin ulceration develop [9]. Ma R, et al. Chest pain is the second leading presenting symptom in ED patients (5.2%) [2], thus thoracic CT angiography (CTA) has become one of the most commonly ordered CTA in ED. large respiratory effort, cardiac motion, and/or the patient physically shifting on the table), leading to premature, delayed or even no bolus triggering. Segmentation methods and processes begin with the acquisition of 3-D image data such as from a high resolution CT scan of a patient's lungs Blood then enters the right ventricle across the tricuspid valve. LIVER AND BILIARY: Normal liver morphology and enhancement. 1). Causes are most often systemic: Impaired hepatic read more ; focal ischemia can cause hepatic infarction or ischemic cholangiopathy Ischemic Cholangiopathy Ischemic cholangiopathy is focal damage to the biliary tree due to disrupted flow from the hepatic artery via the peribiliary arterial plexus. The network that drives the flow of blood towards the central vein is not radial as the radial design does not allow minimum friction losses26. Using contrast enhancement and flow patterns to identify the cause of a non-diagnostic CTA. 12b, Movie 2) [26]. In accord with the constructal law of design32, fluid architectures evolve in time to facilitate access to the currents flowing through them, for minimum pumping power. In this article, wewill review several abnormal contrast enhancement and flow patterns that are encountered in thoracic CTA, including severe abnormalities such as right heart strain, cardiac asystole, and cardiac tamponade. To avoid this, the indication of the scan should be well known to the operating technologist. Normal bladder wall thickness and enhancement. The diameter ratio of each tree has a unique value and obeys the Hess-Murrays law. If g is the generation number (g may vary from one tree to another) than the total number of HA (or PV) outlets or HV inlets is ng=3g, with a splitting number n=3. Post-threshold delay needs to be increased when using a faster scanner to better opacify the non target vessels. We demonstrate that the dendritic nature of the hepatic artery, portal vein and hepatic vein can be predicted, together with their geometrical features (diameter ratio, duct length ratio) as the entire blood flow architectures follow the principle of equipartition of imperfections. Contrast extravasation rates during CT imaging range between 0.1 and 0.9%, with an average rate of 0.4% [13, 14]. 6) in order to spend less pumping power for the same fluid volume26. Axial CECT following the rapid bolus of intravenous contrast in the left upper extremity with the left arm raise (a) shows narrowing of the left subclavian vein at the thoracic inlet and contrast filling multiple small collateral veins in the left shoulder region. Manifestations read more ) or in the intrahepatic terminal hepatic venules and hepatic sinusoids (sinusoidal obstruction syndrome Sinusoidal Obstruction Syndrome Hepatic sinusoidal obstruction syndrome is caused by endothelial injury, leading to nonthrombotic occlusion of the terminal hepatic venules and hepatic sinusoids, rather than of the hepatic read more , previously called veno-occlusive disease) but often occurs in both. Aortic dissection with partial thrombosis of the false lumen has a significantly higher annual aortic growth rate when compared with those patients with complete thrombosis of the false lumen [30]. The hepatic artery brings oxygenated blood. Teutsch HF. The total number of squares is the same as the number of hexagons, namely 16. The three vascular architectures constitute the macro and meso circulation of the human liver. CECT shows marked left atrium enlargement (arrow) with mixing of opacified blood coming from pulmonary veins and non-opacificed blood from the left ventricle due to severe mitral regurgitation. We demonstrated previously that beyond the value of 6 connected branches, radial networks should be replaced by tree-shaped ones with optimized diameter ratios (Eq. The .gov means its official. Tree-shaped architectures are configurations that correspond to a point-to-volume flow. This way, what was initially a local fluid source becomes a distributed fluid source. Why the bigger live longer and travel farther: animals, vehicles, rivers and the winds. Imaging Pearl: Manufacturer recommendations for the central venous catheter that is being used should be adhered to for peak flow rate. Use of delayed images after 30s can help differentiate soft plaque/thrombus from slow flow when dependent pooling is seen. Radiology 256(1):3261. By using this website, you agree to our Patient movement between localizer slice selection/ROI placement and the start of contrast administration/imaging can also affect ROI placement (i.e. A 3D porous media liver lobule model: the importance of vascular septa and anisotropic permeability for homogeneous perfusion. Optimal functioning and seamless integration of every individual piece of this continuum is crucial to ensure optimal contrast opacification of the target vessel, and thus, a diagnostic study, since a chain is only as strong as its weakest link. The distribution of contrast medium is now being determined by the push from the power injector and the viscosity of the contrast medium. The channels length ratio of each tree is similar to the diameter ratio and follows the equipartition of thermodynamic imperfections principle. J Thorac Imaging 31(1):5662, Coulier B, Van den Broeck S (2013) A case of massive transient reduction of attenuation of iodine contrast bolus during computed tomography pulmonary angiography: why and how to avoid it. Match. In addition to target vessel opacification, evaluation of non-target vessels may also contain important clues to the underlying disease that brought the patient to the ED. 2). this patient has a good deal of intrabdominal fat, which separates and surrounds structures, helping to see/differentiate better than in a thinner patient. Terms in this set (43) Blood flow away from the liver. These parameters can be altered to reduce contrast volume in patients with diminished renal function or when a repeat injection becomes necessary in event of an initial, non-diagnostic scan. 15). In Eq. The entire volume of the lobules is fixed because the blood volume is fixed. 1) but failed to visualize the gallbladder (Fig. Inclusion in an NLM database does not imply endorsement of, or agreement with, The microcirculation happens through lobules which hexagonal shape corresponds to minimum flow resistances. 2). PTT can be calculated by evaluating the time attenuation graph obtained from the test bolus (Fig. In bolus tracking technique, only one injection is performed at the planned flow rate. Sequential axial CT images (af) from a test bolus obtained at the level of main pulmonary artery. An electrical analogue of the entire human circulatory system. The architecture was based on bifurcation patterns. 2). Debbaut C, et al. Bolus tracking technique for identification of contrast arrival. It assumes that the bolus geometry of this initial injection and the final injection for the diagnostic scan would remain the same (Fig. Coronal reformatted CECT images depicts extravasated contrast in the upper extremity soft tissues. California Privacy Statement, This resulted in peak pressure reaching 300psi with resultant disarming and decreased flow rate of 2.8mL/s with suboptimal pulmonary artery enhancement. Analyzing the human liver vascular architecture by combining vascular corrosion casting and micro-CT scanning: a feasibility study. JBR-BTR 96(5):304307, Tsai PP, Chen JH, Huang JL, Shen WC (2002) Dependent pooling: a contrast-enhanced sign of cardiac arrest during CT. AJR Am J Roentgenol 178(5):10951099, Roth C, Sneider M, Bogot N, Todd M, Cronin P (2006) Dependent venous contrast pooling and layering: a sign of imminent cardiogenic shock. Contrast arrival in the target vessel can be determined by using test bolus or bolus tracker technique [7, 8]. Regardless of the post-extravasation treatment method, patients should be evaluated by the radiologist. The average values together with their standard deviation are also provided. 9). Despite its dual blood supply, the liver, a metabolically active organ, can be injured by. Diffuse obstruction results in congestion of the sinusoids, hepatomegaly, portal hypertension Portal Hypertension Portal hypertension is elevated pressure in the portal vein. Revellin, R., Rousset, F., Baud, D. & Bonjour, J. The work relies on the fundamentals of fluid mechanics and allows to predict how the blood transport happens through a human liver. 4 with the definition of the fluid volume Vd12L1i=0g3i/3ki, we finally write: We demonstrated previously that the most efficient flow architectures are the ones featuring equipartition of thermodynamics imperfections32. This should not be confused with a thrombus. WebVASCULATURE: Portal, splenic, and superior mesenteric veins are patent. However, recent literature has suggested threshold measurements to identify left atrial enlargement (transverse diameter: 73mm, anteroposterior diameter: 43mm) [3] and left ventricle enlargement (56mm) [4] on a non-ECG gated CTA. Total cavopulmonary connection involves a Glenn shunt connecting SVC to the right PA and Fontan shunt connecting IVC to left PA. CT angiography in these patients to visualize the pulmonary arteries or the conduits themselves is challenging since the SVC flow is directed to the right lung and the IVC flow is directed to the lung (Fig. b: CT scout image after extravasation of intravenously administered contrast in the left upper extremity allows assessment of the extent of extravasation and permits evaluation of possible compartment syndrome. For each network to be fully determined, we also need to predict the tube lengths ratio, and prove the merit of a dendritic-based architecture as opposed to a radial fluid distribution. 1) but failed to visualize the gallbladder (Fig. It may be diffuse and is often related to alcohol, diabetes, certain drugs and medications, or obesity [16].Occasionally, there may be diffuse fatty infiltration in the liver with focal areas of sparing or focal areas of fatty deposition in an otherwise normal liver [46]. Pattern of opacification of non target vessels can be useful in understanding the hemodynamic status of the patient and correctly identifying life threatening conditions such as tamponade, heart failure, and asystole. On another hand, Debbaut et al.46 reported a value of 0.134 mm3 for 3 human liver lobules. Anatomical variations of the hepatic artery are important in the planning and performance of abdominal surgical procedures. Axial (a) and coronal reformatted pulmonary CTA (b) subsequently demonstrates a large central pulmonary embolism. Size of the cannula used for delivery of contrast medium is important to achieve the desired flow rate for the duration of the injection [9]. The lobules dimensions are also difficult to find in the literature. In the case of the tree networks that compose the liver vascular system, the generation number is about 20. (See also Overview of Vascular Disorders of the read more . This result is in good agreement with the anatomical data. J Thorac Cardiovasc Surg 145(3 Suppl):S208S212, Lee S, Chaturvedi A (2014) Imaging adults on extracorporeal membrane oxygenation (ECMO). The shape of the liver is assumed to be a hemisphere with a radius R, the center of which being located at the level of the blood inlet (Fig. Radiograph or CT topogram imaging of the affected limb following an extravasation event may be useful to determine the magnitude of infiltration and verify if compartmentation is present (Fig. Clin Radiol 69(12):e562e567, Park EA, Lee W, Chung SY, Yin YH, Chung JW, Park JH (2010) Optimal scan timing and intravenous route for contrast-enhanced computed tomography in patients after Fontan operation. No abdominal aortic aneurysm. Normal caliber intrahepatic and common bile ducts. The result is a systemic to pulmonary artery shunt. Delayed phase acquisition is recommended for a more accurate estimation of true extent of false lumen thrombus vs. slow flow. Location The IVC starts Considered a physiologic artifact, transient attenuation or interruption of the contrast bolus refers to disruption of the normal opacified contrast column secondary to return of unopacified venous blood via the inferior vena cava (IVC) in the setting of deep inspiration (Fig. True estimation of this false lumen thrombosis after aortic dissection is important as this can be important for prognosis [29]. Contrast opacifies the right portal vein secondary to backflow from hepatic vein into portal vein. J Comput Assist Tomogr 39(5):794796, Rudski LG, Lai WW, Afilalo J, Hua L, Handschumacher MD, Chandrasekaran K et al (2010) Guidelines for the echocardiographic assessment of the right heart in adults: a report from the American Society of Echocardiography endorsed by the European Association of Echocardiography, a registered branch of the European Society of Cardiology, and the Canadian Society of Echocardiography. REPRODUCTIVE ORGANS: Normal size and contours of the prostate and seminal vesicles. Portal vein. Box no. Unable to process the form. The objective was to connect one inlet at the center of the disc to a large number of points distributed on the disk perimeter. 6. 3a), leak at the level of the hub (Fig. Test. Diagnosis is based on physical examination and read more , and splenomegaly Splenomegaly Splenomegaly is abnormal enlargement of the spleen. 8600 Rockville Pike The authors declare no competing interests. All the cells of the porous lobule-system fulfill the metabolic and filtering functions. WebAnswer (1 of 1): The portal vein and hepatic artery provide blood flow to the liver. When present, these findings should raise the suspicion of altered flow dynamics including underlying intra- or extra-cardiac shunt. Federal government websites often end in .gov or .mil. Imaging pearl: In patients with known aortic aneurysm, ROI for test bolus or bolus tracking should be placed in that portion of the aorta which has the largest diameter. Lobules of the liver paving the entire available domain. AJR Am J Roentgenol 193(4):928940, Shuman WP, Branch KR, May JM, Mitsumori LM, Strote JN, Warren BH et al (2009) Whole-chest 64-MDCT of emergency department patients with nonspecific chest pain: Radiation dose and coronary artery image quality with prospective ECG triggering versus retrospective ECG gating. WebIntrahepatic congenital PSSs occur predominantly in large-breed dogs and are often attributable to a patent ductus venosus, originating from the intrahepatic left division of the portal vein and connecting to the left hepatic vein. No ascites. Delayed phasescan at 3min has been shown to be good in visualizing entire vasculature during recirculation, regardless of the intravenous route or surgical technique [28]. The lungs and lymphatic system are most often affected, but read more , and noncirrhotic portal hypertension Portal Hypertension Portal hypertension is elevated pressure in the portal vein. From vascular corrosion cast to electrical analog model for the study of human liver hemodynamics and perfusion. Contrast opacification is of the dependent vasculature only. This dual, reciprocally compensatory blood supply provides some protection from hepatic ischemia in healthy people. Privacy The Physics of Life: The Evolution of Everything. Axial CT image in 46-year-old patient with 20-year H/O essential hypertension presenting with chest pain being evaluated for aortic dissection demonstrates differential enhancement of the ascending and descending aorta due to severe stenosis from coarctation. Learn. Should the objective be to flow from the gastrointestinal tract to the inferior vena cava and the heart, then the straight channel would be the configuration that we should see. WebHepatic vasculature: a conceptual review Author Abstract The hepatic circulation is reviewed with emphasis on the role of hepatic blood vessels in hepatic and homeostatic 5. (See also Overview of Vascular Disorders read more develop. In addition, wewill also revisit key components of intravenous contrast delivery including, but not limited to power injector, intravenous cannula size, flow rate, and access vein size. On an average, the measured splitting number is 2.76 for the hepatic artery, 2.80 for the portal vein, and 3.22 for the hepatic vein, which translated into the integer n = 3. Contrast opacifies the right portal vein secondary to backflow from hepatic vein into portal vein. The total pressure difference between the inlet and the outlet of a lobule is given by, Another way to pave entirely the square domain represented in Fig. We deconstructed the liver as a canopy-to-canopy architecture of trees made of 2 trees running in parallel (the hepatic artery and the portal vein) combined with the hepatic vein tree. Bejan A. Unless the vessel is patent, additional studies should be performed with a contralateral upper extremity injection to permit adequate contrast opacification. Its generic expression is. This can be done immediately if there is another venous access or later after obtaining appropriate venous access. Building a 3D virtual liver: methods for simulating blood flow and hepatic clearance on 3D structures. For example, contrast enhancement of a distal chamber before adequate opacification of a proximal vessel/chamber is never normal. This can help in planning a reinjection and obtain a diagnostic scan. ADVERTISEMENT: Radiopaedia is free thanks to our supporters and advertisers. WebPortal hypertension is a term used to describe elevated pressures in the portal venous system (a major vein that leads to the liver). Hence, if venous visualization is the primary clinical objective, a delayed phase should be obtained in addition to the arterial phase. The lobules which constitute the designed porous medium have a highly regular design. This should be reviewed by the radiologist. Debbaut C, et al. Bejan A. It is caused most often by cirrhosis (in North America), schistosomiasis (in endemic areas), or hepatic vascular abnormalities. In the absence of more precise data, Eq. There is progressively increasing use of CT scans in the emergency department (ED) in recent years [1]. There is no solution to this artifact once acquired, but this can be avoided by using spiral instead of axial acquisitions. Causes of splenomegaly are myriad, as are the read more . A physiologically-based flow network model for hepatic drug elimination II: variable lattice lobule models. In conclusion, each blood architecture corresponds to a system allowing a point-to-volume (or volume-to-point) fluid distribution for minimum pumping work. For a long time, such structures were considered as being the result of chance, i.e. Calculations of the diameter ratio, length ratio and splitting number of branches, data from Debbaut et al.19,29 and Ma et al.22. Repeat injection with placement of ROI in true lumen resulted in adequate evaluation of dissection. Suzuki K, et al. This can lead to variable enhancement pattern (Fig. Google Scholar, Remy-Jardin M, Doyen J, Remy J, Artaud D, Fribourg M, Duhamel A (1997) Functional anatomy of the thoracic outlet: evaluation with spiral CT. Radiology 205(3):843851. 1/2. Differential enhancement of ascending and descending aorta during a thoracic aortic CTA can be seen by using a prospectively triggered acquisition, coarctation, large aneurysms, and dissections. Visceral arteries are patent. Insufficient venous drainage may result from focal or diffuse obstruction or from right-sided heart failure, as in congestive hepatopathy Congestive Hepatopathy Congestive hepatopathy is diffuse venous congestion within the liver that results from right-sided heart failure (usually due to a cardiomyopathy, tricuspid regurgitation, mitral insufficiency read more . Indications for thoracic CTA include pulmonary embolus, acute aortic syndrome, or coronary artery disease. The The theory is compared with good agreement to anatomical data from the literature. Our approach is based on the constructal law of design14. Axial CECT after injection of intravenous contrast in the left upper extremity shows a large filling defect in the left subclavian vein (arrows) and multiple venous collaterals in the left shoulder region. Careful attention demonstrates mediastinal venous collaterals draining directly into the pulmonary veins forming an extra-cardiac right to left shunt, Axial CT images from a patient with coronary artery to pulmonary artery fistula, which results in partial opacification of the main pulmonary artery while contrast is maximally opacifying the aorta, seen on axial CTA (a, b) and conventional angiography (c). Each square element receives the blood from each of its 4 corners. The modular microarchitecture of human liver. 18). Mas group22 managed to measure up to the 20th generation for the 3 different vascular networks, and reported the channels diameters. As the majority of thoracic CTAsare performed with the patients arms raised, compression of the subclavian vein (asymptomatic or symptomatic) can lead to compromises in IV contrast delivery to the central vascular structures, affecting bolus timing and leading to suboptimal opacification due to reductions in flow rate (Fig. Evaluation of these graphs is important in identifying the planned flow rate and any changes to that. (See also Overview of Vascular Disorders of the Liver.) The results are di+1/di= 0.74, 0.70, and 0.59 for the hepatic arteria, the portal vein and the hepatic vein respectively according to Debbaut et al.19,29, while a ratio of 0.79 is obtained from the measurements provided by Ma et al.22. Google Scholar, Schaverien MV, Evison D, McCulley SJ (2008) Management of large volume CT contrast medium extravasation injury: technical refinement and literature review. Axial CTA shows moderate pericardial effusion and heterogeneous enhancement of descending aorta with blood contrast layering. 6). Fontan shunt is performed as the third stage of ventricular repair and involves anastomosis between the IVC and the left pulmonary artery. Delayed images (90s) demonstrate complete opacification of both pulmonary arteries and the intracardiac Fontan (b, also see Movie 2). Chronic pancreatitis is characterized by histologic read more , tumor), or congenital atresia of the portal vein, Intrahepaticeg, microvascular portal vein obstruction as occurs in schistosomiasis Schistosomiasis Schistosomiasis is infection with blood flukes of the genus Schistosoma, which are acquired transcutaneously by swimming or wading in contaminated freshwater. Ann Emerg Med 58(5):452462, e453, Article The results are gathered in Fig. Some authors use a 1-min delay provided the injection is antecubital due to shorter distance to pulmonary artery and in patients with cavopulmonary connections than atriopulmonary connections [28]. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. 16a). In our experience, slowing the flow of the circuit to the minimal flow rate that would prevent thrombus formation for the duration of the scan (1520s) has worked well in cases of suspected pulmonary embolism (Fig. Imaging Pearl: In patients with known heart failure, test bolus can be more useful in identifying time to peak enhancement, which can be delayed compared to contrast arrival time. Received 2019 Dec 23; Accepted 2020 Sep 10. Debbaut C, et al. The fluid enters a mother tube (diameter di and length Li) and splits through n daughter tubes of constant geometrical features (diameter di+1 and length Li+1). brought the medical vision to the work. Br J Radiol 84(999):197203, Article PANCREAS: Normal morphology and enhancement. Korean J Radiol: Off J Korean Radiol Soc 15(3):322329, Lidegran MK, Ringertz HG, Frenckner BP, Linden VB (2005) Chest and abdominal CT during extracorporeal membrane oxygenation: Clinical benefits in diagnosis and treatment.
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