Spleen Microcirculation
John H. Barker, Gary L. Anderson, Michael D. Menger in Clinically Applied Microcirculation Research, 2019
Microvascular corrosion casting may be applied to spleens of humans as well as laboratory animals. Normal human spleens are available from transplant donors, but a large portion of the organ is used for tissue typing; with surgically removed spleens from various disease states, samples are first taken by the pathologist. In either case, it is possible to obtain a cast from a portion of the organ. In brief, the procedure is as follows. A major arterial branch, distant from any incision, is cannulated and the spleen is perfused with ~1 liter of heparinized Ringer solution at 100 cm H2O pressure, resulting in washout of most of the RBCs from the perfused segment. A low-viscosity methacrylate resin, e.g., modified Batson’s compound35 or Mercox (Dainippon Ink and Chemicals, Tokyo), is then injected at a rate of 2 to 4 ml/min. The volume of compound used varies according to the amount of tissue perfused, but is generally 1 to 5 ml for a “minimal-injection” cast. The organ is then left undisturbed for several hours for polymerization of the resin to occur. Pieces of tissue ~1 cm2 are cut from the filled segment and the tissue is corroded away from these samples with 40% KOH at 60°C for 5 to 6 days. The vascular casts are then carefully rinsed in distilled water, air-dried, mounted on SEM stubs, and sputter-coated with gold for examination by SEM. (For full details, see Reference 4.)
Regional Therapy of Liver Metastases: A Surgeon’s View
Neville Willmott, John Daly in Microspheres and Regional Cancer Therapy, 2020
The vascular morphology of xenotransplanted human tumors has been described in some detail in a series of studies by Konerding et al.,93–95 in which the tumor vasculature was examined by corrosion casting and both transmission and scanning electron microscopy. They found disorganized heterogeneous structures, immature endothelial cells with abnormal cell contacts, and even tumor cells incorporated into the vessel wall. Most studies agree that the heterogeneous nature of the tumor vascularity does not correlate with histology,96,97 that is, tumors with similar histology often do not have a comparable vascular pattern.
Endovascular Implants
Wilmer W Nichols, Michael F O'Rourke, Elazer R Edelman, Charalambos Vlachopoulos in McDonald's Blood Flow in Arteries, 2022
The most critical component in CFD is resolution of the deformed artery and stent geometry, with feature sizes in tens of microns. To circumvent the difficulties of resolving stents with clinical imaging modalities, flow simulations initiated modeling a two-dimensional array of struts and later extended to three-dimensional idealized arteries (straight tubes) (Berry et al., 2000; LaDisa et al., 2003, 2004, 2005a, 2005b; Murphy et al., 2010; Duraiswamy et al., 2009). In general, stents were constructed using computer-aided design (CAD) software and embedded within straight (or bent) tubes in order to study the flow patterns and wall shear stress distribution for different stent configu-rations. These simulations, although simplified, revealed invaluable wealth of knowledge on effects of postintervention axial and circumferential deformation of stented artery, stent design and configuration, arterial size and curvature, flow pulsatility and blood viscosity on wall shear stress distribution (LaDisa et al., 2006; Rouhi et al., 2013; Rajamohan et al., 2006; Seo et al., 2005; Lewis, 2008; Gundert et al., 2011; Bedoya et al., 2006). Researchers later reconstructed patient-specific arterial geometries by segmenting clinical images from MRI and computer tomography (CT) and virtually adjoined the stent by geometrical methods or finite element structural simulations (Figure 23.2) (Morlacchi et al., 2011a; Gundert et al., 2011; Ellwein et al., 2011; Timmins et al., 2007; Balossino et al., 2008; Pant et al., 2012; Mortier et al., 2010). Stents were also imaged in explanted/artificial arteries using microcomputed tomography (µCT) to extract their geometry with highest resolution for CFD (Morlacchi et al., 2011b; Benndorf et al., 2010; Wang et al., 2011). Postmortem stented arteries or ex vivo hearts have also been used combining the destructive process of vascular corrosion casting (VCC) with µCT to yield detailed reconstruction of wall shear stress distribution (LaDisa et al., 2005c; Morlacchi et al., 2011b; Rikhtegar et al., 2013). These updated methods allow researchers to model more complicated scenarios including stent overlap and bifurcations (Rikhtegar et al., 2014; Chiastra et al., 2012; Foin et al., 2012; Morlacchi et al., 2011a). More recently image-processing techniques have been introduced that fuse the angiography with intravascular ultrasound (IVUS) or optical coherence tomography (OCT) to acquire the high-resolution geometry and that could serve CFD to provide a wall shear stress map with utmost geometrical fidelity (Slager et al., 2000; Chiastra et al., 2019; O’Brien et al., 2016).
Deficiency of the Wnt receptor Ryk causes multiple cardiac and outflow tract defects
Published in Growth Factors, 2018
Kumudhini Kugathasan, Michael M. Halford, Peter G. Farlie, Damien Bates, Darrin P. Smith, You Fang Zhang, James P. Roy, Maria L. Macheda, Dong Zhang, James L. Wilkinson, Margaret L. Kirby, Donald F. Newgreen, Steven A. Stacker
Vascular corrosion casting of E18.5 embryos revealed the morphology of the great arteries and heart. Over 90% of Ryk−/− mice had defects in the aortic arch (Figure 2 and Table 1). Aortic arch stenosis (AAS; Figure 2(D,E,I–L)) or interruption of the aortic arch (IAA type-B, between the left common carotid (LCC) artery and the left subclavian artery (LSA); Figure 2(M–P)), were the most serious aortic arch defects observed. AAS and IAA were present in 53% and 13% of Ryk−/− mice, respectively (Table 1). Right-sided aortic arch (RSAA) occurred in 5% of Ryk−/− mice (Table 1; Figure 2(F–H)).
Transarterial drug delivery for liver cancer: numerical simulations and experimental validation of particle distribution in patient-specific livers
Published in Expert Opinion on Drug Delivery, 2021
Tim Bomberna, Ghazal Adeli Koudehi, Charlotte Claerebout, Chris Verslype, Geert Maleux, Charlotte Debbaut
There are several limitations to the research, which – at the same time – inspire future work. First, two types of outlet BCs were used: (i) Murray’s law, and (i) the perfusion methodology [20], while neither has been validated in vivo yet. Note that in Table 2 two sets of outlet BCs were reported for a cancer-free scenario in the CL (according to the 2 types of BCs). This discrepancy stresses that, moving forward, more appropriate BCs should ideally be used, preferably validated by or based on patient-specific in vivo measurements. Second, from a modeling perspective, the effect of transient cardiac pulses should ideally be included to more accurately describe the PD in physiological conditions (i.e. for particle release during a specified, clinically achievable time window) [15,16]. Importantly, more attention should be paid to the clinical interpretation of the non-exit particles in these transient conditions. Third, it should be noted that geometries generated from vascular corrosion casting can be slightly expanded compared to in vivo conditions, but that shrinkage of the resin can also occur [39,40,41]. In the future, the use of patient-specific anatomical imaging resulting from CT or MRI scans should be prioritized. Fourth, the scope of this study was limited to studying uncontrolled particle injection in the PHA in two patient-specific geometries. In addition to the parameters studied in this work, other clinically relevant parameters (such as injection velocity, catheter type, catheter tip orientation, etc.) should also be studied to fully estimate the possibilities offered by parameter optimization [16–19,21]. Future work also should focus on modeling axial injection locations beyond the first bifurcation, up to the point where the vasculature becomes inaccessible for catheters. As such, the workflow proposed in this study can be repeated for this larger range of axial locations to investigate the impact of parameter optimization for injection further downstream. Similarly, injections with more precise control of in-plane catheter tip location should be studied. Overall, more patient-specific liver geometries should be studied to verify the observations made. Last but not least, the scope of the experimental study was currently limited to a proof-of-concept, but should be expanded to investigate the sensitivity of the experimental PDs toward varying injection conditions and particle parameters.
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