with minimum work, to deliver a fixed volume of fluid from one point to an infinite number of points (a volume or a surface). The channels length ratio of each tree is similar to the diameter ratio and follows the equipartition of thermodynamic imperfections principle. Sketch of hexagonal (left side) and square configurations (right side). Assume one main sinusoid of diameter dh connects a triad to the central vein. No ascites. Before discharge, a radiologist discusses the findings that would suggest a developing compartment syndrome with the patient. However, the arrival of contrast media may not always be simultaneous due to different resistance, collaterals, and flow velocities. The patient is instructed to seek medical attention if new neurologic or circulatory symptoms or skin ulceration develop [9]. As such, it is often described by a power-law model. Normal hepatic anatomy occurs in approximately 80% of cases, for the remaining 20% multiple variations have been described. The network was completely determined thanks to (i) the radius ratio between a daughter branch and a mother branch in accord with the Hess-Murrays law (di+1/di=2-1/3, where 2 was the number of daughter branches), and (ii) the connection angles between ducts at each bifurcation level. Therefore, because the total mass flow rate is a constant, the mass flow rate per element must continue to be mh. Google Scholar, Department of Imaging Sciences, University of Rochester Medical Center, 601 Elmwood Ave, P.O. We wrote in Table Table11 the diameter ratios at each generation level, their average value and standard deviation for the 3 flow configurations, calculated from the data provided in Refs. According to the literature15,44,45, the average human liver has a volume of 1500 cm3, and contains 1020% of blood, while it possesses about 106 lobules. Cavopulmonary shunts that connect the caval and pulmonary circulation are performed in patients with single ventricle physiology. If this location is incorrect, such as a false lumen of an aortic dissection, the attenuation may not reach the threshold and the scan may not be initiated (Fig. ADVERTISEMENT: Supporters see fewer/no ads. Relying on these findings, we write Li+1=kLi, where k is to be discovered. 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. Learn. The mass flow rate is related to the average velocity through mh=6ULht, with t the lobule thickness. PubMed Central 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. 10). Similarly, persistent enhancement of a proximal segment when most of the contrast has washed out from the distal segments is not normal. Numerical modeling of oxygen availability in the AMC bioartificial liver. Glenn shunt is performed as the second stage of surgical repair and involves anastomosis between the SVC and the right pulmonary artery, which can either be unidirectional or bidirectional. Unable to process the form. Alternatively, new access from the contralateral extremity vein can be obtained. 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]. 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. WebA patent paraumbilical vein (PUV) is a frequent finding in patients with cirrhosis when studied by duplex Doppler ultrasound. Based on the previous assumptions, the friction losses and total volume vary as. In patients unable to hold breath, alternatively a free breathing high pitch flash CTA may be obtained [21] (Fig. Bejan A. The Anatomically based simulation of hepatic perfusion in the human liver. J Comput Assist Tomogr 34(1):7581, Clough RE, Hussain T, Uribe S, Greil GF, Razavi R, Taylor PR et al (2011) A new method for quantification of false lumen thrombosis in aortic dissection using magnetic resonance imaging and a blood pool contrast agent. In. Therefore we write. The proximal end of the stent extends into the right atrium in this patient, who was not a suitable candidate for liver transplantation. Their complexity often forces to reduce the hydrodynamic studies of the liver to its morphofunctional unit, the lobule23,24. It is performed with a higher radiation dose and larger dose of IV contrast, which helps to evaluate subtle areas of bowel inflammation. Cookies policy. Inclusion in an NLM database does not imply endorsement of, or agreement with, 4b) [15]. Graphs and tables from the power injector: pressure-time and flow rate-time graphs. 3b) with abrupt cessation of flow, or contrast medium extravasation. 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. Axial CECT (a) shows a type B dissection with mixing of contrast in the true lumen (arrow). CT image during test bolus injection (a) with regions of interest over the ascending aorta (1), descending aorta (2) and pulmonary artery (3). Acad Radiol 12(3):276285, Plumb AA, Murphy G (2011) The use of central venous catheters for intravenous contrast injection for CT examinations. Demondion X, Herbinet P, Van Sint Jan S, Boutry N, Chantelot C, Cotten A (2006) Imaging assessment of thoracic outlet syndrome. 12b, Movie 2) [26]. AJR Am J Roentgenol 186(4):11161119, Jana M, Gamanagatti SR, Kumar A (2010) Case series: CT scan in cardiac arrest and imminent cardiogenic shock. Hepatic portal vein. This provides an excellent look at the large and small bowel enhancement and vasculature, and also the solid organs. Tree-shaped architectures are configurations that correspond to a point-to-volume flow. 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. The authors published the radii, lengths and number of branches of the hepatic artery, the portal vein and the hepatic vein. The most common cause is portal hypertension. Bethesda, MD 20894, Web Policies 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. Check for errors and try again. Normal caliber intrahepatic and common bile ducts. 1 doctor answer 1 doctor weighed in Dr. Lisa Roazenanswered Emergency Medicine 20 years experience Talk now Patent = open: It sounds like you've gotten a report from an Configurations of trees matching canopy-to-canopy were already presented by our group in the context of engineering applications3739. In case of an access vein size and i.v. Indeed, Fisher17 in 1954 showed experimentally that the volume of blood reaching the liver and somehow the "delivered pressure", have an evident impact on the regenerative stimulus of liver regeneration with 3 surgical variants of restitution of portal flow plus hepatectomy. 18 gives a permeability K ranging between 3 1010 m2 and 9 1012 m2. Using contrast enhancement and flow patterns to identify the cause of a non-diagnostic CTA. This canopy-to-canopy feature is complemented by a porous medium, the lobules. If the patient is not being monitored, and when such a finding is seen on a nondiagnostic CTA, it is imperative to call the code team and immediately begin cardiopulmonary resuscitation rather than planning for a reinjection. this patient does have hepatic steatosis and a tiny gallstone or cholesterol polyp. (MOV 563 kb), Delayed phase axial CT from a CTPE study obtained in a patient with tricuspid atresia and bidirectional cavopulmonary connection demonstrate complete opacification of both pulmonary arteries and the intracardiac Fontan. 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. There may be retrograde opacification of IVC, hepatic veins, and even portal vein with dependent pooling of the contrast forming a blood-contrast level (Movie 1) [24]. In a patient with contrast flow rate above the recommended maximum (a). 1/2. In the case of fluid flow networks it means that the minimum pumping power is found when the pressure losses are equally distributed over the flow architecture. It has been shown that 13% of these patients have mural thrombus in the extracardiac conduit [27], even without symptoms, which may be missed with suboptimal studies [27] Solutions for this are (1) Simultaneous upper and lower extremity (femoral vein/foot vein) injections at 45mL/s, so that both the SVC and IVC are opacified simultaneously [27]. The physiological principle of minimum work: I. From vascular corrosion cast to electrical analog model for the study of human liver hemodynamics and perfusion. 17af) of aorta, poor opacification of cardiac chambers, and suboptimal enhancement of the pulmonary vessels. Mixing artifacts can be seen in large aortic aneurysms and should not be confused with a thrombus (Fig. On another hand, Debbaut et al.46 reported a value of 0.134 mm3 for 3 human liver lobules. The initial CTA ROI wasplaced in the false lumen (b). Clin Radiol 69(12):12641272, Article Greenway CV, Stark RD. This is similar to contrast attenuation in SVC. Thanks to the constructal law we could predict the main geometrical features of the liver: This work establishes the theoretical bases that help to complete the understanding of the results of experimental work carried out since the last century on animal models, as well as the most recent ones on experimental models on silicon scaffolds, organs on chips, and scaffolds of decellularized organs. No masses. 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. The hepatic artery provides oxygenated blood to the liver, while the portal vein brings deoxygenated blood; the two mix in the sinusoids. Detailed examples can be found in Refs3436. J Vasc Surg 54(5):12511258, Trimarchi S, Tolenaar JL, Jonker FH, Murray B, Tsai TT, Eagle KA et al (2013) Importance of false lumen thrombosis in type B aortic dissection prognosis. Mixing artifacts in the true lumen of the descending aortic aneurysm with Type B aortic dissection which resolve on delayed phase acquisition. (See also Overview of the Spleen.) A physiologically-based flow network model for hepatic drug elimination II: variable lattice lobule models. PubMed The peak flow rate that can be achieved also depends on the size of the access vein [9] (Table 4). Contrast flow and enhancement patterns seen on CTA can often be challenging and may often reveal more than is immediately apparent. Finally, the permeability of a lobule of volume V is, which, in view of the asymptotic value of fn, gives. River basin in a liver lobule. The objective was to connect one inlet at the center of the disc to a large number of points distributed on the disk perimeter. Wechsatol et al.26 showed that they happen because they are the most efficient way, i.e. The assembly of lobules constitutes a functionalized porous medium which must allow the mixing of the oxygenated blood from the hepatic artery and the deoxygenated blood from the portal vein. Findings could represent thrombus. Manifestations of focal venous obstruction depend on the location. Contrast injection should be administered into the vein of the asymptomatic extremity to reduce beam hardening artifact [17, 18]. 1Department of Mechanical Engineering, Villanova University, Villanova, PA 19085 USA, 2Departamento de Fsica, Facultad de Ciencias, Universidad Nacional Autnoma de Mxico, Circuito Exterior S/N, Ciudad Universitaria, CP04510 Coyoacn, Ciudad de Mxico, Mexico, 3Centro Mdico 20 de Noviembre, ISSSTE,, Flix Cuevas 540, Del Valle Sur, Benito Jurez, CP03100 Ciudad de Mxico, Mexico. Provides 20% of blood to the 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. 648, Rochester, NY, 14642, USA, Abhishek Chaturvedi,Daniel Oppenheimer,Katherine A. Kaproth-Joslin&Apeksha Chaturvedi, Department of Radiology, University of Texas Southwestern, Dallas, TX, USA, You can also search for this author in The term (g+1)3/3g is lower than 1 as soon as the generation number reaches a value of 5, while L1 3cc/s [11], and for coronary artery assessment is>5cc/s [12] (Table 3). The outlet flow (hepatic vein) is located at the center of each lobule. 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. A 3D porous media liver lobule model: the importance of vascular septa and anisotropic permeability for homogeneous perfusion. Understanding these graphs will help the radiologist plan a repeat contrast injection to overcome the deficiencies of the first injection and thus obtain a diagnostic scan. The portal vein and hepatic arteries form the liver's dual blood supply. Approximately 75% of hepatic blood flow is derived from the portal vein, while the remainder is from the hepatic arteries. [4] Unlike most veins, the portal vein does not drain into the heart. The hepatic artery waveform has a low-resistance profile with broad systolic peaks, gradual deceleration from systole to diastole, and well-maintained The likely explanation for these findings can be increased pulmonary transit time. Rezania V, Marsh R, Coombe D, Tuszynski J. Differential enhancement of pulmonary arteries during a pulmonary artery CTA can be seen in patients with Fontan circulation (Fig. & Lorente, S. Analysis of thermochemical energy storage in an elemental configuration. kycurrier. where n0 is the number of sectors connected to the source (n0= 6 here), Li^=Li/Lh the non-dimensional branch length, and n is the bifurcation level. Patient with cardiac arrest at the time of CTA for acute aortic syndrome. Since the contrast media will directly opacify the lower SVC or the right atrium and the subsequent cardiovascular structures, the upper SVC and other veins will not be adequately opacified in the first pass as with a peripheral route injection. Imaging Pearl: Manufacturer recommendations for the central venous catheter that is being used should be adhered to for peak flow rate. Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Learn more about the Merck Manuals and our commitment to Global Medical Knowledge. Therefore, from the measurements of 4 representative portions of the liver, they considered that the total number of branches could be estimated in proportion of the total liver volume. The hexagonal cross section shows 6 portal triads made of the bile duct, the portal vein and the hepatic artery. AJR Am J Roentgenol 192(6):16621667, Shaqdan K, Aran S, Thrall J, Abujudeh H (2014) Incidence of contrast medium extravasation for CT and MRI in a large academic medical centre: a report on 502,391 injections. Raising the affected limb above the level of the heart may reduce swelling and facilitate absorption of extravasated fluid. 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. As each square element is in contact with 3 other ones, the mass flow rate through the duct of diameter d and length Ld must be mh. The flow resistance created in the case of a dendritic design is given by. where K is the intrinsic permeability of the lobule. 17 obtained after the ECMO circuit was put on minimal flow status for a short period (25s) to allow for near physiologic circulation. Indian J Radiol Imaging 20(2):150153, Tomasian A, Malik S, Shamsa K, Krishnam MS (2009) Congenital heart diseases: post-operative appearance on multi-detector CT-a pictorial essay. Indications for thoracic CTA include pulmonary embolus, acute aortic syndrome, or coronary artery disease. 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. In the simplest case we assume that the ducts have a round cross section of diameter d and length L. The pulsatile nature of blood flow in the hepatic artery network is classically expressed through an electrical impedance analogy. They tend to be saccular and multiple. Wambaugh J, Shah I. Simulating microdosimetry in a virtual hepatic lobule. 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. No body wall masses. The radial distribution of the fluid would generate a flow resistance P/mradial which order of magnitude is R/3gdradial4. The theory is compared with good agreement to anatomical data from the literature. Contrast opacification on thoracic CT angiography: challenges and solutions, https://doi.org/10.1007/s13244-016-0524-3. 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. Diffuse obstruction results in congestion of the sinusoids, hepatomegaly, portal hypertension Portal Hypertension Portal hypertension is elevated pressure in the portal vein. Blood is then pushed out when reaching the center of the lobule through the central vein parallel to the portal triad. Numerical simulation of the hepatic circulation. Anyone you share the following link with will be able to read this content: Sorry, a shareable link is not currently available for this article. No pleural or pericardial effusion. Bolus tracking technique for identification of contrast arrival. Contrast flow and enhancement patterns seen on thoracic CT angiography (CTA) can often be challenging and may often reveal more than is immediately apparent. Bejan A, Tondeur D. Equipartition, optimal allocation, and the constructal approach to predicting organization in nature. Acute pancreatitis is inflammation that resolves both clinically and histologically. Inappropriate placement of ROI for bolus tracking scan is a common cause of non-diagnostic CT scan. Nevertheless considering that the hexagonal shape is close to the circle shape, the same expression was used in this work to predict the order of magnitude of the lobule permeability. This artifact should be considered when there is decreased opacification of multiple bilateral pulmonary arteries at the same level without vessel lumen distention: true pulmonary emboli typically present at various levels and normally expand the vessel lumen acutely [19]. Specific vascular lesions may occur in the hepatic artery, hepatic vein, or portal vein. This is important since there is a higher risk of pulmonary thromboembolism (319%) in these patients [27]. 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. Optimal time for acquisition would be when both lumens are opacified. The hepatic veins (there are three) carry blood out of the liver and empty into the vena cava. 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. 1). The site is secure. Terms and Conditions, Part of Dynamic CTA, with the arm in neutral position and then in elevated positions (130 of hyperabduction with external rotation), can be used to evaluate TOS [17, 18]. The entire network is similar to a river delta, except that in the case of the lobule the fluid flows in the reverse direction as in the river basin. Lobules of the liver paving the entire available domain. CAS The sinusoids are The hepatic artery may be occluded Hepatic Artery Occlusion Causes of hepatic artery occlusion include thrombosis (eg, due to hypercoagulability disorders, severe arteriosclerosis, or vasculitis), emboli (eg, due to endocarditis, tumors, therapeutic read more .