Unless the vessel is patent, additional studies should be performed with a contralateral upper extremity injection to permit adequate contrast opacification. 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. Notice the altered pattern of contrast flow. Axial CTA images from the same patient as in Fig. in cases of a pulmonary artery CTA, this implies delayed aortic opacification. We are interested in predicting the geometrical features leading to the smallest overall pressure difference possible. 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. Visceral arteries are patent. The distribution of contrast medium is now being determined by the push from the power injector and the viscosity of the contrast medium. Hepatic artery. 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. You can use Radiopaedia cases in a variety of ways to help you learn and teach. Learn more about the Merck Manuals and our commitment to Global Medical Knowledge. The likely explanation for these findings can be increased pulmonary transit time. In case of an access vein size and i.v. liver Note that the number of 6 branches is the limit for which the radial connections exhibited in Fig. 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. 15). Liver Exam #2. River basin in a liver lobule. VASCULATURE: Portal, splenic, and superior mesenteric veins are patent. Ann Emerg Med 58(5):452462, e453, Article Review of the axial images in the upper abdomen (b) reveal contrast reflux into IVC, dependent hepatic veins, and a blood-contrast level in the IVC. 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). Mas group22 managed to measure up to the 20th generation for the 3 different vascular networks, and reported the channels diameters. Ultrasound Assessment of the Hepatic Vasculature Causes include infection, arteriosclerosis, trauma, and vasculitis. Anatomically based simulation of hepatic perfusion in the human liver. Insights Imaging 5(4):493506, Article The IVCs job is to return blood to the heart from the lower half of the body, including the feet, legs, thighs, pelvis, and abdomen. Calculations of the diameter ratio, length ratio and splitting number of branches, data from Debbaut et al.19,29 and Ma et al.22. Pater L, Berg J. Here we do not consider the bile canal. Shah I, Wambaugh J. and transmitted securely. Acute pancreatitis is inflammation that resolves both clinically and histologically. Lobules of the liver paving the entire available domain. American College of Radiology Manual on Contrast Media V10.2, 2016. The work dealt with a surface with a round cross section. When a dual energy scanner is not available, we use a larger volume (1.5mL/kg) of contrast medium containing 350 mgI/mL iodine and use 80 or 100 kVp for image acquisition. Manage cookies/Do not sell my data we use in the preference centre. The modular microarchitecture of human liver. The latter is a three-dimensional network forming a lattice between rows cells, mainly hepatocytes, epithelial cells responsible for the metabolism taking place in the liver. When portal vein blood flow increases, hepatic artery flow AJR Am J Roentgenol 194(4):912919, Bae KT (2005) Test-bolus versus bolus-tracking techniques for CT angiographic timing. Murray CD. This way, what was initially a local fluid source becomes a distributed fluid source. If pain is the main symptom, we use cold compresses, and if the extravasation has occurred in a location where there is a higher likelihood of compartment syndrome, we use hot compresses. A delayed phase, 40s acquisition can help in identifying any thrombus, vegetation, or fibrin sheath attached to the catheter. 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. A test bolus is preferable to bolus tracking in patients with post-surgical repair of complex congenital heart diseases. Repeat injection with placement of ROI in true lumen resulted in adequate evaluation of dissection. 17 obtained after the ECMO circuit was put on minimal flow status for a short period (25s) to allow for near physiologic circulation. Radiology 256(1):3261. 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. 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. Repeat injection with the left arm downby the patients side (b) shows excellent opacification of the left subclavian vein and no filling of venous collaterals, permitting a diagnostic scan for evaluation of pulmonary embolus, Chronic left subclavian vein thrombus with venous collateral formation. 3. The pathophysiologic mechanism of this artifact is secondary to the normal variable inflow of blood to the right heart during inspiration. This is called the transit delay (Table 2) and varies from patient to patient and scanner to scanner. Eur Radiol 19(12):29412949, Sandler KL, Markham LW, Mah ML, Byrum EP, Williams JR (2014) Optimizing CT angiography in patients with Fontan physiology: single-center experience of dual-site power injection. The hepatic artery (which is oxygen-rich) supplies the rest. Contrast also opacifies the right portal vein secondary tobackflow from hepatic vein into the portal vein. No ductal dilation or masses. The iliac arteries branch off of the bottom of the aorta, the large artery coming out of the top of the heart. J Plast Reconstr Aesthet Surg 61(5):562565, discussion 565, Tonolini M, Campari A, Bianco R (2012) Extravasation of radiographic contrast media: prevention, diagnosis, and treatment. From one source, the blood not only invades the sinusoids network in the broad direction of the central vein, but it must also flow along the hexagon periphery at mid-distance from the two neighboring sources. The assembly of hexagonal shapes makes each hepatic artery and portal vein in contact with 3 lobules. PTT can be calculated by evaluating the time attenuation graph obtained from the test bolus (Fig. Detailed measurements of the geometrical features of the human liver blood network are scarce. The Liver failure after major hepatic resection. The physical components of a CTA include the CT scanner, intravenous cannula, access vein size, and power injector; the functional component is the patients cardiac status. Peak flow rate needed varies on the indication for the CTA: preferred flow rate for pulmonary artery CTA is 35cc/s [10], for aortic evaluation is > 3cc/s [11], and for coronary artery assessment is>5cc/s [12] (Table 3). In peliosis hepatis Peliosis Hepatis Peliosis hepatis is typically an asymptomatic disorder in which multiple blood-filled cystic spaces develop randomly in the liver. Part of The https:// ensures that you are connecting to the The initial CTA ROI wasplaced in the false lumen (b). As indicated by precise anatomy analysis of the liver architecture1922, the hepatic artery, portal vein and hepatic vein networks are three-dimensional, highly nested, forming an extremely compact structure. In conclusion, p/mdendriticp/mradial. Selection of the wrong target vessel, especially in the setting of complex vascular anatomy, and/or selection of an ROI which is too big or too small are common operator dependent errors. Imaging pearl: Check the access vein and access cannula before initiating contrast injection. 7c). Hepatic Vasculature: A Conceptual Review The microcirculation happens through lobules which hexagonal shape corresponds to minimum flow resistances. For a long time, such structures were considered as being the result of chance, i.e. WebPortal hypertension is a term used to describe elevated pressures in the portal venous system (a major vein that leads to the liver). Raising the affected limb above the level of the heart may reduce swelling and facilitate absorption of extravasated fluid. There is controversy regarding the clinical significance of this finding. Hepatic vascular bed. Bhattacharya S, Shoda LKM, Zhang Q, Woods CG, Howell BA, Siler SQ, Woodhead JL, Yang Y, McMullen P, Watkins PB, Andersen M. E modeling drug- and chemical-induced hepatotoxicity with systems biology approaches. Also note the differential enhancement in descending aorta. We showed that the global flow resistance decreases as the number of bathed elements connected to the trees increases. Imaging pearl: Know the transit delay and scan acquisition time of the CT scanner. 12b, Movie 2) [26]. Adjacent to the Falciform Ligament on Contrast WebA patent paraumbilical vein (PUV) is a frequent finding in patients with cirrhosis when studied by duplex Doppler ultrasound. Hepatic vascular shunts Further downstream, the flow from the two inlet trees is reconstituted into a single stream through the outlet HV tree. Patient with cardiac arrest at the time of CTA for acute aortic syndrome. These are, however, not commonly seen in left atrium or left ventricle, and whenever seen should be considered abnormal (Fig. provided the experimental data and figures, A.S.C. 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. Splenomegaly is almost always secondary to other disorders. Wechsatol W, Lorente S, Bejan A. Optimal tree-shaped networks for fluid flow in a disc-shaped body. In normal subjects, this is about 6.81.7s [6]. In addition, there are some life-threatening findings, which unless sought for, may remain hidden in plain sight. Quantitative radiology: automated CT liver volumetry compared with interactive volumetry and manual volumetry. This does not have impact in the theoretical approach presented here because the frequency domains relevant to biological flows, as in the case of the liver, correspond to a negligible imaginary contribution in the impedance expression of the fluid flow, leaving a direct proportionality between pressure difference and mass flow rates as provided by the real part of the impedance30. PubMed Central 4 would be to use squared shaped lobules of side LS with AS=LS2. Perfusion characteristics of the human hepatic microcirculation based on three-dimensional reconstructions and computational fluid dynamic analysis. Hepatic vein disorders can result in focal or diffuse venous obstruction. There is no solution to this artifact once acquired, but this can be avoided by using spiral instead of axial acquisitions. Careful interpretation of power injector graphs, location of region of interest to trigger the scan, and pattern of contrast flow can help determine the cause. 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 hemodynamics of flow in these patients, especially those on a venoarterial ECMO, are altered, with retrograde flow occurring in the access artery and in case of femoral artery access, in theaorta [32]. 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 kycurrier. with minimum work, to deliver a fixed volume of fluid from one point to an infinite number of points (a volume or a surface). 13), and when using prospective ECG triggered CTA (Fig. Blood is a non-Newtonian fluid. Federal government websites often end in .gov or .mil. 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. Through the following text, we will address the important pieces of this fine-tuned sequence and how malfunction of any individual component can limit attempts to obtain a diagnostic study. Contrast Use for phrases o [teenager OR adolescent ], , MD, University of Colorado School of Medicine. Test bolus technique for identification of contrast arrival in target vessel. Patient movement between localizer slice selection/ROI placement and the start of contrast administration/imaging can also affect ROI placement (i.e. reports a lobule permeability of 4.8 109 m2. The work unveils the structure of the liver blood flow architecture as a combination of superimposed tree-shaped networks and porous system. Please confirm that you are a health care professional. (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. Urgent states, "How to Read an Abdominal CT" Chapter 1 Supplement, Normal gastrointestinal tract imaging examples, this is a CT of the Abdomen and Pelvis, Enterography protocol. 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 blood transport through the lobules behaves like a flow through a porous system which predicted overall permeability agrees with data available in the literature. Fontan shunt is performed as the third stage of ventricular repair and involves anastomosis between the IVC and the left pulmonary artery. 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. Portal, splenic, superior mesenteric veins, Visceral arteries (celiac, splenic, common hepatic, renal, SMA, IMA), Iliac, pelvic, and femoral arteries and veins, Upper abdomen (gastrohepatic ligament, celiac, portocaval, porta hepatis). When using a scanner with shorter acquisition time, non target vessel enhancement may be less than expected, and these vessels should be interpreted with caution. Consequences read more . WebPortal Circulation. Such dependent contrast pooling in descending aorta can also be seen in patients with acute cardiac tamponade, likely due to decreased stroke volume (Fig. this is a higher quality study than a standard CT. No body wall masses. The objective of this work is to lay the theoretical foundations of the deterministic behavior of the human liver vasculature, as a hierarchical fluid mechanics system. The central veins, or hepatic veins (HV) collect the blood and lead it to the vena cava inferior. The modeling of the hepatic circulation has been a challenge for several decades. Our approach is based on the constructal law of design 1, 2, 3, 4. At the smallest scale, the shape of the liver elemental systemsthe lobulesis discovered, while their permeability is also predicted. Normal caliber small and large bowel. Received 2019 Dec 23; Accepted 2020 Sep 10. Power injector pressure-time and flow rate-time graphs in a different patient with IV infiltration during the injection (b) shows rapid drop in pressure and cessation of flow at the time of contrast extravasation. The resistance factor fn is obtained from the search of minimum overall flow resistance in a laminar dendritic structure: the diameter ratio (which follows the Hess-Murays law27,28), the branches lengths and bifurcation angles correspond to minimum pressure losses. In addition, there are some life-threatening findings, which unless sought for, may remain hidden in plain sight. Portal Venous System Cavopulmonary shunts that connect the caval and pulmonary circulation are performed in patients with single ventricle physiology. In the case of the tree networks that compose the liver vascular system, the generation number is about 20. Diagnosis is based on ultrasonography. Earlier opacification of a distal chamber may be an indicator of intra or extra-cardiac shunt. Correspondence to Alternatively, new access from the contralateral extremity vein can be obtained. The hepatic artery provides oxygenated blood to the liver, while the portal vein brings deoxygenated blood; the two mix in the sinusoids. 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 hand or foot), use of power injection, use of a vessel with multiple puncture attempts, and use of a peripheral IV that has been in place >24h can also increase the risk of extravasation [1315]. Google Scholar, Schaverien MV, Evison D, McCulley SJ (2008) Management of large volume CT contrast medium extravasation injury: technical refinement and literature review. Cirrhosis Cirrhosis Cirrhosis is a late stage of hepatic fibrosis that has resulted in widespread distortion of normal hepatic architecture. The liver vasculature makes its unique among the other organs as it is made of the superimposition of three main networks, two inlets and one outlet. As such, it is often described by a power-law model. Ma R, et al. The blood distribution within the lobule is similar to a reverse river basin connecting rivulets to a central sink. Human error is a common source of inappropriate placement. 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. The latter led to the duct length ratio. 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]. Chaturvedi, A., Oppenheimer, D., Rajiah, P. et al. Each tree architecture is composed of a main trunk subdivided into smaller and smaller braches. Greenway CV, Stark RD. Finally the overall pressure loss is, The pressure loss along the sinusoids is phmh/6Lh/dh4 in the case of the hexagonal shape, and pcmh/4Lh/dc4 in the case of the square shape. Numerical modeling of oxygen availability in the AMC bioartificial liver. Specific vascular lesions may occur in the hepatic artery, hepatic vein, or portal vein. The hepatic artery, portal vein and hepatic vein form a compact three-dimensional dendritic architecture within the liver. The two inlet networks, namely the hepatic artery (HA) and the portal vein (PV), run in parallel. (2) Two-phase CT angiography, with both arterial and delayed venous phases (Fig. The sinusoids together with the hepatocyte cords form the smallest units of the liver: the lobules. Mathematical modeling of the circulation in the liver lobule. developed the theory, M.H. 4, we see that the square image is made of about 16 hexagonal shapes of side Lh.
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