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. 2). Also, contrast pressure and flow graphs obtained with the CTA often contain useful information regarding the etiology of a non-diagnostic scan (Table 1). In patients with small caliber access veins, a dual energy acquisition can be obtained. 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. PTT can be calculated by evaluating the time attenuation graph obtained from the test bolus (Fig. Here we do not consider the very first tube length ratio as no information is provided on the first duct length in Refs19,29. The flow resistance created in the case of a dendritic design is given by. J Thorac Imaging 22(2):125129, Ajlan AM, Binzaqr S, Jadkarim DA, Jamjoom LG, Leipsic J (2016) High-pitch Helical dual-source computed Tomographic pulmonary angiography: comparing image quality in inspiratory breath-hold and during free breathing. 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. 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. cannula mismatch the pressure may exceed the threshold, which may limit the flow rate. Copyright 2023 Merck & Co., Inc., Rahway, NJ, USA and its affiliates. Debbaut C, et al. Liver Exam #2. Privacy Contrast opacification on thoracic CT angiography: challenges and solutions . Configurations of trees matching canopy-to-canopy were already presented by our group in the context of engineering applications3739. The thinner channels form the canopy of the HA and PV trees and irrigate the lobules which behave like a porous system. 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]. 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. 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 inlet vasculature is made of the hepatic artery and the portal vein, the outlet vasculature is made of the hepatic vein. Considering Darcy flow through the porous elemental system (i.e. 8600 Rockville Pike See also Movie 1. In patients with pulmonary hypertension or congestive heart failure (CHF), pulmonary circulation can be slow and PTT will be prolonged, which may lead to delayed contrast arrival in the non target vessel, e.g. This is due to dilution of contrast within the blood pool of the post stenotic dilated aortic lumen. 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. Similarly, persistent enhancement of a proximal segment when most of the contrast has washed out from the distal segments is not normal. one lobule), the average velocity of the blood flowing to the central vein is. 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. o [teenager OR adolescent ], , MD, University of Colorado School of Medicine. The sinusoids tortuous network bathes the entire lobule, supplying the blood to the central vein from the 6 sources (hepatic artery+portal vein). What do you mean by hepatic veins and portal veins are patent? For a long time, such structures were considered as being the result of chance, i.e. Street network theory of organization in nature. The lobules which constitute the designed porous medium have a highly regular design. J Thorac Imaging 19(1):17, Wittram C, Yoo AJ (2007) Transient interruption of contrast on CT pulmonary angiography: proof of mechanism. Coil embolisation of the varices was performed. Building a 3D virtual liver: methods for simulating blood flow and hepatic clearance on 3D structures. No peripancreatic fluid. The microcirculation happens through lobules which hexagonal shape corresponds to minimum flow resistances. MUSCULOSKELETAL: No aggressive osseous lesion. 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. Graphs and tables from the power injector: pressure-time and flow rate-time graphs. The overall pressure loss from the hexagon rim to the central vein is the sum of the pressure losses along the branches of the flow dendritic pathway. Back in the mid twentieth century, Landes5 noticed in 1943 the analogy between blood flows and electrical currents transport. Findings could represent thrombus. WebThe hepatic artery (which is oxygen-rich) supplies the rest. Imaging pearl: Check the access vein and access cannula before initiating contrast injection. Such dependent contrast pooling in descending aorta can also be seen in patients with acute cardiac tamponade, likely due to decreased stroke volume (Fig. 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. Symptoms usually result from abdominal distention. The average values together with their standard deviation are also provided. No urolithiasis or hydronephrosis. Thoracic venous outlet obstruction of the left subclavian vein with the left arm raised for CTPA, which subsequently resolves upon positioning the arm down at the side. The canopy-to-canopy view of the liver vascular system. Accessibility White D, Coombe D, Rezania V, Tuszynski J. Referred to as the abdominal-thoracic pump, initial deep inspiration decreases intrathoracic pressure and increases intraabdominal pressure, acutely increasing venous return, favoring flow from the IVC over the superior vena cava (SVC), resulting in a bolus of nonopacified blood entering the right heart from the abdomen [19, 20]. Wechsatol W, Lorente S, Bejan A. Optimal tree-shaped networks for fluid flow in a disc-shaped body. The two major venous plexuses that are Yet, about 20years ago, A. Bejan25 proved that dendritic configurations can be predicted, and that they exist for a very specific purpose. The outlet flow (hepatic vein) is located at the center of each lobule. The hepatic veins drain the liver into the inferior vena cava. Contrast opacification on thoracic CT angiography: challenges and solutions, https://doi.org/10.1007/s13244-016-0524-3. Somatostatin and the Small-For-Size Liver. Normal sequence of enhancement follows right atrium, right ventricle, pulmonary artery, pulmonary vein, left atrium, left ventricle, and aorta. There is insufficient opacification of the pulmonary circulation due to siphoning of contrast by ECMO. Visceral arteries are patent. Central veins of the thorax convey blood/contrast bolus to the right atrium. 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. Virtual tissues in toxicology. Demondion X, Herbinet P, Van Sint Jan S, Boutry N, Chantelot C, Cotten A (2006) Imaging assessment of thoracic outlet syndrome. Terms in this set (43) Blood flow away from the liver. The modular microarchitecture of human liver. This prompted initiation of cardiopulmonary resuscitation and calling the code team. PubMed No ductal dilation or masses. Mixing artifacts can be seen in large aortic aneurysms and should not be confused with a thrombus (Fig. In case of an access vein size and i.v. Transient interruption of contrast bolus results in suboptimal opacification of the pulmonary artery on initial contrast bolus, with subsequent diagnostic scan for pulmonary embolus after repeat injection using high pitch FLASH CTA. We do not control or have responsibility for the content of any third-party site. This has important implications for a diagnostic scan, especially pulmonary CTA as the injection may not occur at the peak rate planned thus leading to suboptimal opacification. Systems modeling of developmental vascular toxicity. WebLiver Vasculature. GI TRACT AND PERITONEUM: Normal morphology of the stomach and duodenum. The assembly of hexagonal shapes makes each hepatic artery and portal vein in contact with 3 lobules. Assume one main sinusoid of diameter dh connects a triad to the central vein. In this case we see an altered pattern of contrast flow: first SVC, followed by minimal opacification of the pulmonary artery and ascending aorta, dense opacification of the descending aorta followed by dense opacification of the ascending aorta. The narrowing of the left subclavian vein prevented adequate opacification of the pulmonary artery. The liver has a dual blood supply. Using contrast enhancement and flow patterns to identify the cause of a non-diagnostic CTA. Miguel AF. Kim S, Lorente S, Bejan A. Vascularized materials: tree-shaped flow architectures matched canopy to canopy. The mesenteric arteries may have variant anatomy in approximately 20% of the population, which may lead to misinterpretation of Doppler examination findings. Also note the differential enhancement in descending aorta. An optimal, diagnostic thoracic CTA study is never obtained by accident. No body wall masses. 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 Garcea G, Maddern GJ. In type B dissection, identification of false lumen thrombus can be overestimated by first pass CTA/MRA. Check for errors and try again. American College of Radiology Manual on Contrast Media V10.2, 2016. The hepatic artery provides oxygenated blood to the liver, while the portal vein brings deoxygenated blood; the two mix in the sinusoids. The initial CTA ROI wasplaced in the false lumen (b). The hepatic veins drain the liver into the inferior vena cava. Lower (4060KeV) monoenergetic reconstruction can be obtained to boost contrast opacification. Both sources of blood mix in the sinusoids. 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. In. Alalaimi M, Lorente S, Wechsatol W, Bejan A. 6). WebA patent paraumbilical vein (PUV) is a frequent finding in patients with cirrhosis when studied by duplex Doppler ultrasound. 2). 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]. This provides an excellent look at the large and small bowel enhancement and vasculature, and also the solid organs. 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. The pulmonary artery to ascending aorta transit time (PTT) is a key circulatory parameter that can affect target, as well as non-target vessel opacification on a thoracic CTA. 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. Despite its dual blood supply, the liver, a metabolically active organ, can be injured by. 16b). At such a small scale, it seems appropriate to use a porous medium analogy16,4143. Bejan A, Tondeur D. Equipartition, optimal allocation, and the constructal approach to predicting organization in nature. 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 test bolus technique, a small amount of contrast is injected followed by saline chaser at the predetermined flow rate to identify contrast arrival in target vessels.
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