American College of Radiology Manual on Contrast Media V10.2, 2016. Calling Ah the area of the hexagon, we have Ah=332Lh2. 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. Missing is a theoretical approach, based on first principles, that would allow to predict the flow architecture of the hepatic circulation: liver transplant, or liver resection as a treatment for liver tumors, may end up to liver failure with disastrous consequences when the change in blood pressure is not controlled1416. Importantly, the scan delay and total acquisition time may vary depending on the scanner (Table 2). & Lorente, S. Analysis of thermochemical energy storage in an elemental configuration. This can lead to differential enhancement in different segments of the aorta, which merely indicates different contrast density at different time points. Inclusion in an NLM database does not imply endorsement of, or agreement with, Insights into Imaging Debbaut C, et al. Treatment read more due to a hypercoagulable state, a vessel wall lesion (eg, pylephlebitis, omphalitis), an adjacent lesion (eg, pancreatitis Overview of Pancreatitis Pancreatitis is classified as either acute or chronic. 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. Blood is then pushed out when reaching the center of the lobule through the central vein parallel to the portal triad. This way, what was initially a local fluid source becomes a distributed fluid source. Patent and flow direction. Differential enhancement of pulmonary arteries during a pulmonary artery CTA can be seen in patients with Fontan circulation (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. Teutsch HF. In the paper published by Miguel35 in 2016, the equipartition of thermodynamics imperfections concept translates into an equipartition of flow resistances. Coronal reformatted CECT images depicts extravasated contrast in the upper extremity soft tissues. CTA shows contrast reflux into IVC and dependent hepatic veins and blood-contrast level in the IVC. There are two significant imaging consequences of this artifact: missing a true pulmonary embolus due to decreased opacification of the pulmonary artery or misinterpreting the decreased vessel attenuation as an embolus when it is not present. Lucia U, Grisolia G. Time: a constructal viewpoint & its consequences. This can help in planning a reinjection and obtain a diagnostic scan. (2) Two-phase CT angiography, with both arterial and delayed venous phases (Fig. The initial CECT (a) shows poor opacification of the pulmonary artery despite high density contrast material within the aorta and SVC because deep inspiration resulted in increased venous return from the IVC and dilution of the contrast bolus in the right heart (b) at the time of scanning. Virtual liver networks combine biology to fluid mechanics and mass transfer as novel approaches to physiology models913. In a normal patient, contrast injected from the upper extremity first opacifies the SVC, followed by the right atrium, right ventricle, pulmonary artery, pulmonary vein, left atrium, left ventricle, ascending aorta, and finally the descending thoracic aorta. Contrast extravasation rates during CT imaging range between 0.1 and 0.9%, with an average rate of 0.4% [13, 14]. Mixing artifacts can be seen in large aortic aneurysms and should not be confused with a thrombus (Fig. It is performed with a higher radiation dose and larger dose of IV contrast, which helps to evaluate subtle areas of bowel inflammation. Studies have shown that vascular enhancement is superior with central venous catheter injections compared to peripheral route injections due to the short time to peak enhancement facilitated by shorter travel distance for contrast bolus. 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. Bolus tracking technique for identification of contrast arrival. Ricken, T., Waschinsky, N. & Werner, D. Simulation of steatosis zonation in liver lobuleA continuum mechanical bi-scale, tri-phasic, multi-component approach. 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. 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. Delayed phase CECT in the same patient (b) shows resolution of the mixing artifact. Obstruction can be, Extrahepatic portal vein thrombosis Portal Vein Thrombosis Portal vein thrombosis causes portal hypertension and consequent gastrointestinal bleeding from varices, usually in the lower esophagus or stomach. No body wall masses. The contrast opacification of the false lumen does not reach the thresholdrequired to trigger the scan as seen on on bolus tracker HU-time graph. 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. Once mixed the blood is pushed into the hepatic vein. Thoracic venous outlet obstruction should be considered when extensive collateral vessel filling is seen on the side of contrast administration when the patients arms are raised. https://doi.org/10.1007/s13244-016-0524-3, DOI: https://doi.org/10.1007/s13244-016-0524-3. Obstruction can occur in the intrahepatic or extrahepatic veins (Budd-Chiari syndrome Budd-Chiari Syndrome Budd-Chiari syndrome is obstruction of hepatic venous outflow that originates anywhere from the small hepatic veins inside the liver to the inferior vena cava and right atrium. By using low energy virtual monoenergetic images, the energy levels of which are closer to the K edge of iodine, the contrast signal is amplified which can potentially salvage some suboptimal studies. The lobule is considered to be the liver functional unit, the elemental system. Box no. Blood then enters the right ventricle across the tricuspid valve. We showed that the entire liver circulatory architecture is deterministic. Contrast opacifies the right portal vein secondary to backflow from hepatic vein into portal vein. Why a hexagon? Furthermore, due to the absence of pumping action of right ventricle, there is passive laminar flow of Fontan circulation, which causes inhomogeneous enhancement, particularly within the conduit [28]. 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. Two images from a CTPE study obtained in a patient with tricuspid atresia and bidirectional cavopulmonary connection demonstrate poor opacification of right pulmonary artery and non-enhancement of left pulmonary artery (a). Debbaut C, et al. Patients at risk for contrast extravasation include infants and small children, elderly, uncooperative, and unconscious patients, as they may not be able to communicate or complain of pain reliably during injection. 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 We are interested in predicting the geometrical features leading to the smallest overall pressure difference possible. Bejan A. 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. 12b, Movie 2) [26]. Its role is fundamentally important, particularly in the transformation of toxic substances to elements that the body can eliminated. 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 In conclusion, p/mdendriticp/mradial. Please confirm that you are a health care professional. Wambaugh J, Shah I. Simulating microdosimetry in a virtual hepatic lobule. 16b). http://creativecommons.org/licenses/by/4.0/. 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). All rights reserved. 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. The inlet vasculature is made of the hepatic artery and the portal vein, the outlet vasculature is made of the hepatic vein. In case of an access vein size and i.v. WebThe Hepatic circulation is unique among vascular beds. 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. Conceptually, the liver vascularization can be seen as 2 trees matching canopy-to-canopy bathing a porous architecture made of lobules, as presented in Fig. The architecture was based on bifurcation patterns. Yet, about 20years ago, A. Bejan25 proved that dendritic configurations can be predicted, and that they exist for a very specific purpose. 17 obtained after the ECMO circuit was put on minimal flow status for a short period (25s) to allow for near physiologic circulation. 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. 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. REPRODUCTIVE ORGANS: Normal size and contours of the prostate and seminal vesicles. The liver has a dual blood supply. Note that the number of 6 branches is the limit for which the radial connections exhibited in Fig. Unable to process the form. In the absence of more precise data, Eq. 5 is a good pattern. 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 veins drain the liver into the inferior vena cava. An optimal, diagnostic thoracic CTA study is never obtained by accident. The .gov means its official. in cases of a pulmonary artery CTA, this implies delayed aortic opacification. The flow path is represented on the left hand side of Fig. Understanding the way its blood vasculature works is key. Axial CTA images being obtained in a patient suspected for acute aortic syndrome and found to be in asystole with no cardiac output. It assumes that the bolus geometry of this initial injection and the final injection for the diagnostic scan would remain the same (Fig. A delayed phase, 40s acquisition can help in identifying any thrombus, vegetation, or fibrin sheath attached to the catheter. The theory is compared with good agreement to anatomical data from the literature. The hepatic artery (which is oxygen-rich) supplies the rest. Nevertheless, and following the work of Revellin et al.31, Hess-Murrays law remains valid even with a power-law model. This phase allows more accurate estimation of the extent of the false lumen thrombus and slow flow. We consider that Ah=AS, which means that the hexagon is reshaped to become a square, and LS=33/42Lh1.6Lh. If we look into Fig. 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. The latter led to the duct length ratio. 8a and b). The current review article outlines normal and abnormal intravenous contrast dynamics, discusses how to recognize etiologies of non-diagnostic scans, and ultimately addresses techniques to overcome obstacles towards obtaining normal contrast opacification of the target vessel. 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. Method and processes for segmentation of lungs lobes from CT image data are disclosed. 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 This is similar to contrast attenuation in SVC. Some favor cold compresses to decrease pain at the extravasation site and others prefer warm compresses to improve blood flow to the extravasation site and increase absorption of the contrast from the tissues into the vasculature and lymphatics. Splenomegaly is almost always secondary to other disorders. Somatostatin and the Small-For-Size Liver. 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. No ductal dilation or masses. Mathematical modeling of the circulation in the liver lobule. If suboptimal contrast opacification of the target vessel is present, reimaging the patient with the arm in the neutral or adducted position should relieve the dynamic narrowing of the thoracic outlet, thereby improving opacification of the vessel (Fig. There is progressively increasing use of CT scans in the emergency department (ED) in recent years [1]. government site. A physiologically-based flow network model for hepatic drug elimination I: regular lattice lobule model. this is a higher quality study than a standard CT. 1) but failed to visualize the gallbladder (Fig. The average values together with their standard deviation are also provided. Moreno, R., Segers, P. & Debbaut, C. Estimation of the permeability tensor of the microvasculature of the liver through fabric tensors. 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. A 3D porous media liver lobule model: the importance of vascular septa and anisotropic permeability for homogeneous perfusion. Decreased systolic function of left ventricle can result in dependent contrast pooling and layering in the aorta [25]. Axial (a) and coronal reformatted pulmonary CTA (b) subsequently demonstrates a large central pulmonary embolism. WebSPH is commonly secondary to acute or chronic pancreatitis and pancreatic cancer and rarely secondary to peritoneal inflammatory disease, abdominal tumors or diseases of the Privacy Consequences read more , reduced portal blood flow, ascites Ascites Ascites is free fluid in the peritoneal cavity. The sector covered has an angle of /6 from the central vein, see Fig. Sagittal CECT MIP image demonstrates differential opacification of the aorta proximal and distal to the aortic coarctation with post-stenotic dilatation. WebPortal Circulation. The sinusoids tortuous network bathes the entire lobule, supplying the blood to the central vein from the 6 sources (hepatic artery+portal vein). Wechsatol W, Bejan A, Lorente S. Tree-shaped flow architectures: strategies for increasing optimization speed and accuracy. 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). To confront the theoretical approach developed in this paper to experimental data, we rely on anatomic results provided by two different groups19,22,29. 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. AJR Am J Roentgenol 194(4):912919, Bae KT (2005) Test-bolus versus bolus-tracking techniques for CT angiographic timing. Patent mesenteric vasculature and an antimesenteric pattern of involvement, along with reports of hypercoagulability in patients with COVID-19, suggest the necrosis occurred as a result of microvascular thrombosis and associated inflammation. Other severe For a long time, such structures were considered as being the result of chance, i.e. This is consistent with the results provided by Siggers et al.40 whose finite elements modeling in 2D indicates a reduction in blood flow rate in a square lattice as opposed to a hexagonal one. The inlet flow comes from the hepatic artery and the portal vein constituting the triad (the third element being the bile canal). The term (g+1)3/3g is lower than 1 as soon as the generation number reaches a value of 5, while L124h can also increase the risk of extravasation [1315]. The lobules are represented classically by prismatic volumes of hexagonal cross section with one triad made of the hepatic artery, the portal vein and the bile duct at each of the 6 hexagon corners, and a central vein along the axis of the lobule. The link you have selected will take you to a third-party website. The hexagonal cross section shows 6 portal triads made of the bile duct, the portal vein and the hepatic artery. Brought to you by Merck & Co, Inc., Rahway, NJ, USA (known as MSD outside the US and Canada) dedicated to using leading-edge science to save and improve lives around the world. Acute pancreatitis is inflammation that resolves both clinically and histologically. Cirrhosis is characterized by regenerative nodules surrounded by dense read more is the most common cause of diffuse intrahepatic venous outflow obstruction. 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. Lucia U, Grisolia G, Astori MR. Constructal law analysis of Cl transport in eyes aqueous humor. 16,17 If originating from the right branch of the portal vein, these shunts drain directly into the caudal vena cava. Attenuation-time graph corresponding to the regions of interest (b) shows prolonged pulmonary circulation time of 16s in this patient due to aortic stenosis (normal pulmonary transit time is approximately 79s). The hepatic artery originates from the common hepatic artery and divides into the right and left hepatic arteries. Notice the large thrombus in the A-V malformation abutting the main pulmonary artery, Coronal reformat from a thoracic CTA in a 13-year-old patient with mid aortic syndrome demonstrates step ladder artifact in the pulmonary artery as well as descending aorta. Use OR to account for alternate terms If false lumen dose not opacify at all on the bolus timing scan, a limited Z axis 60s delayed image can be obtained to confirm slow flow/ thrombus or for follow-up, contrast-enhanced MRA may be obtained. Non-diagnostic thoracic CTAs are frequently encountered in clinical practice. 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. 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. Received 2019 Dec 23; Accepted 2020 Sep 10. Any disruption of the above-described normal sequence of events should be treated with suspicion. When prospective ECG gating is used (Fig. WebLiver Vasculature. 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. 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. What Is A Patent Portal Vein And What Is Patent Hepatic Artery And A Patent Hepatic Vein ? The portal vein and hepatic artery provide blood flow to the liver. The hepatic veins (there are three) carry blood out of the liver and empty into the vena cava. When they are "patent" it means that they are open and flowing normally. Lobe segmentation relies on other segmentations, including the lungs, the lung airways and vasculature. 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. 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. 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. 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. All the cells of the porous lobule-system fulfill the metabolic and filtering functions. 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. Such dependent contrast pooling in descending aorta can also be seen in patients with acute cardiac tamponade, likely due to decreased stroke volume (Fig. Google Scholar, Department of Imaging Sciences, University of Rochester Medical Center, 601 Elmwood Ave, P.O. Scanning Electron Microscope images of human liver reveal that the elemental system, the lobule, is entirely vascularized19. 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]. Garcea G, Maddern GJ. Differential aortic enhancement can also be seen in patients with coarctation of aorta (Fig. 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]. We observe the patient in the radiology department for at least 1h to ensure that there are no new symptoms, such as pain or numbness to suggest development of compartment syndrome. 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.