Visceral arteries are patent. Contrast-blood mixing artifacts are often seen in the right atrium, right ventricle and pulmonary artery during a pulmonary artery CTA due to unopacified blood returning from the IVC. Delayed phase CECT in the same patient (b) shows resolution of the mixing artifact. 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 results are gathered in Fig. Calculations of the diameter ratio, length ratio and splitting number of branches, data from Debbaut et al.19,29 and Ma et al.22. 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. 9) because the mass flow rate along the Ld ducts of diameter d (hepatic artery and portal vein) is half the one of a square assembly. 9). The pathophysiologic mechanism of this artifact is secondary to the normal variable inflow of blood to the right heart during inspiration. Note the differential enhancement in the right ventricle outflow tract vs. main pulmonary trunk. Shah I, Wambaugh J. Necrosis Similarly, persistent enhancement of a proximal segment when most of the contrast has washed out from the distal segments is not normal. 1). Normal bladder wall thickness and enhancement. The entire volume of the lobules is fixed because the blood volume is fixed. Contrast injection should be administered into the vein of the asymptomatic extremity to reduce beam hardening artifact [17, 18]. Below are links to the electronic supplementary material. In conclusion, p/mdendriticp/mradial. In patients with small caliber access veins, a dual energy acquisition can be obtained. 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. The mesenteric arteries may have variant anatomy in approximately 20% of the population, which may lead to misinterpretation of Doppler examination findings. The initial CTA ROI wasplaced in the false lumen (b). 6). Liver failure after major hepatic resection. Delayed phase acquisition is recommended for a more accurate estimation of true extent of false lumen thrombus vs. slow flow. We showed that the entire liver circulatory architecture is deterministic. Portal hypertension may be caused by intrinsic liver disease, obstruction, or structural changes that result in increased portal venous flow or increased hepatic resistance. 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. 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. The liver is one of the most important organ of the human body. WebFatty deposition in the liver is common and has many imaging manifestations. The lobule is considered to be the liver functional unit, the elemental system. A delayed phase, 40s acquisition can help in identifying any thrombus, vegetation, or fibrin sheath attached to the catheter. 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. 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. Murray CD. Mixing artifacts can be seen in large aortic aneurysms and should not be confused with a thrombus (Fig. True estimation of this false lumen thrombosis after aortic dissection is important as this can be important for prognosis [29]. At the time the case was submitted for publication Michael P Hartung had no recorded disclosures. 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. Virtual tissues in toxicology. 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. The liver is not only the largest organ in the body but also the one playing one of the most important role in the human metabolism as it is in charge of transforming toxic substances in the body. 18 gives a permeability K ranging between 3 1010 m2 and 9 1012 m2. The hepatic artery, portal vein and hepatic vein form a compact three-dimensional dendritic architecture within the liver. There is no solution to this artifact once acquired, but this can be avoided by using spiral instead of axial acquisitions. California Privacy Statement, The Physics of Life: The Evolution of Everything. You can use Radiopaedia cases in a variety of ways to help you learn and teach. Contrast pressure and flow graphs often contain useful information regarding the etiology of a non-diagnostic scan. 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. 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. Street network theory of organization in nature. Ma R, et al. The measured diameters (blue dots) and lengths (red squares) ratios inside the liver as a function of the splitting generation number, for the hepatic artery HA, the portal vein PV and the hepatic vein HV. Axial CTA images from the same patient as in Fig. statement and The hepatic veins drain the liver into the inferior vena cava. When portal vein blood flow increases, hepatic artery flow decreases and vice versa (the hepatic arterial buffer response). This dual, reciprocally compensatory blood supply provides some protection from hepatic ischemia in healthy people. On conventional angiography, the fistula is seen opacifying on the arterial phase (arrow). CTA shows contrast reflux into IVC and dependent hepatic veins and blood-contrast level in the IVC. Bejan A. Portal Venous System The average values together with their standard deviation are also provided. (AVI 5728 kb). For example, if the ROI is placed in the false lumen of a type B aortic dissection (Fig. (See also Overview of Vascular Disorders read more develop. Other severe Match. The most common cause is portal hypertension. The sinusoids tortuous network bathes the entire lobule, supplying the blood to the central vein from the 6 sources (hepatic artery+portal vein). In the absence of more precise data, Eq. Power injector is used to inject contrast medium and saline chaser at a constant flow rate for the entire duration of the injection. Although there are safety issues related to this such as the risk of catheter rupture, fragmentation, or thromboembolism, these devices can be safely used if appropriate precautions including manufacturer specifications are followed [34]. 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. Vasculature Measuring read more , blood-filled cystic spaces develop in the sinusoids (microvascular anastomoses between the portal and hepatic veins). 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. The term (g+1)3/3g is lower than 1 as soon as the generation number reaches a value of 5, while L1Adjacent to the Falciform Ligament on Contrast 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. Radiology 236(1):369370, author reply 370, Bae KT (2010) Intravenous contrast medium administration and scan timing at CT: considerations and approaches. The necessary pumping power is provided by the heart, and is proportional to mp. CAS Further downstream, the flow from the two inlet trees is reconstituted into a single stream through the outlet HV tree. Here we do not consider the bile canal. 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. Kim S, Lorente S, Bejan A. Vascularized materials: tree-shaped flow architectures matched canopy to canopy. 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. Patient with cardiac arrest at the time of CTA for acute aortic syndrome. Bonfiglio A, Leungchavaphongse K, Repetto R, Siggers JH. In addition, use of distal access sites (i.e. 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 sinusoids are Therefore, because the total mass flow rate is a constant, the mass flow rate per element must continue to be mh. River basin in a liver lobule. See also Movie 1. Before Here, Lh is the distance between the lobule center and its perimeter. In normal subjects, this is about 6.81.7s [6]. 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. This would give a lobule volume of 1.5 mm3. Flashcards. 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. MUSCULOSKELETAL: No aggressive osseous lesion. 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. 13a). (See also Overview of Vascular Disorders of the Liver.) 14), there may be a delay between consecutive axial acquisitions which is exaggerated in the presence of irregular heart rate. Differential enhancement of false lumen of an aortic dissection can also be due to delayed opacification due to higher inherent luminal pressures. 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. The link you have selected will take you to a third-party website. Using contrast enhancement and flow patterns to identify the cause of a non-diagnostic CTA. These patients are likely hemodynamically unstable at the time of presentation and may be on cardiopulmonary monitoring which should be evaluated by the attending radiologist. 3b) with abrupt cessation of flow, or contrast medium extravasation. PTT can be calculated by evaluating the time attenuation graph obtained from the test bolus (Fig. volume8,pages 127140 (2017)Cite this article. Careers, Unable to load your collection due to an error. Any disruption of the above-described normal sequence of events should be treated with suspicion. Acute findings (SBO, appy, diverticulitis, enteritis, colitis, appendagitis, etc), Distal esophagus and gastroesophageal junction, Small and large bowel caliber, wall thickness, enhancement, Hernias (ventral, umbilical, spigellian, parastomal, lumbar, inguinal, femoral, obturator, sciatic). 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. 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. 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 . 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]. The scan is initiated as soon as the contrast enhancement threshold (predetermined threshold HU) is reached within the region of interest. The hepatic artery waveform has a low-resistance profile with broad systolic peaks, gradual deceleration from systole to diastole, and well-maintained 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]. Repeat injection using high pitch FLASH technique with free breathing (c) shows excellent opacification of the pulmonary artery. 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. The sinusoids are uniformly distributed throughout the entire liver volume, and constitute the hepatic microcirculation. 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. 15). When prospective ECG gating is used (Fig. 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. 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 . Findings could represent thrombus. Numerical modeling of oxygen availability in the AMC bioartificial liver. 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). In the paper published by Miguel35 in 2016, the equipartition of thermodynamics imperfections concept translates into an equipartition of flow resistances. 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 ACR Manual on Contrast Media discusses the treatment of contrast extravasation [9]. The liver, a functionalized vascular structure | Scientific Reports Manifestations of focal venous obstruction depend on the location. We are interested in predicting the geometrical features leading to the smallest overall pressure difference possible. 12b, Movie 2) [26]. Consequences read more , reduced portal blood flow, ascites Ascites Ascites is free fluid in the peritoneal cavity. official website and that any information you provide is encrypted This can lead to differential enhancement in different segments of the aorta, which merely indicates different contrast density at different time points. 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. The latter led to the duct length ratio. (See also Overview of the Spleen.) Revellin, R., Rousset, F., Baud, D. & Bonjour, J. Nevertheless, and following the work of Revellin et al.31, Hess-Murrays law remains valid even with a power-law model. All rights reserved. Vena portae hepatis. Greenway CV, Stark RD. Yet, about 20years ago, A. Bejan25 proved that dendritic configurations can be predicted, and that they exist for a very specific purpose. The hexagonal cross section shows 6 portal triads made of the bile duct, the portal vein and the hepatic artery. Check for errors and try again. PubMed Central and transmitted securely. Inappropriate placement of ROI for bolus tracking scan is a common cause of non-diagnostic CT scan. The peak flow rate that can be achieved also depends on the size of the access vein [9] (Table 4). This can be done immediately if there is another venous access or later after obtaining appropriate venous access. Graphs and tables from the power injector: pressure-time and flow rate-time graphs. No abdominal aortic aneurysm. Radiology 256(1):3261. The Numerical simulation of the hepatic circulation. Detailed examples can be found in Refs3436. 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 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. Also note the differential enhancement in descending aorta. How to read a CT of the abdomen and pelvis | Radiology 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. At the smallest scale, the shape of the liver elemental systemsthe lobulesis discovered, while their permeability is also predicted. Vasculature 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. Wambaugh J, Shah I. Simulating microdosimetry in a virtual hepatic lobule. If we look into Fig. The hepatic veins drain the liver into the inferior vena cava. Two graphs are generated by the power injector, which plot the change in pressure over time and flow rate of the injection over time (3 A, B). WebThe Hepatic circulation is unique among vascular beds. Patient with descending aortic dissection with suboptimal increase in contrast opacification within the region of interest (ROI) and failure to trigger the scan (a).
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