Feasibility of Changing Intra-Arterial Flow Direction by Temporary Occlusion Using Retrievable Coils: Study with a Normal Pig Model.

PURPOSE: To evaluate feasibility of changing intra-arterial flow direction by temporary occlusion using retrievable coils. MATERIALS AND METHODS: In 2 healthy pig livers, injection of a lipiodol mixture (lipiodol:saline = 2:1) was performed at the segmental arteries after occluding 1 of the subsegmental arteries. This was accomplished using a retrievable coil in 5 different segmental arteries (3 in pig A and 2 in pig B). Injection of the lipiodol mixture was performed through a 3-way system using a hemostatic valve, whereas the retrievable coil delivery system was in the lumen of a microcatheter. Successful coil deployment, occlusion of the vessel, and coil retrieval were evaluated. Redistribution of flow after placement of the coil and vessel patency after coil removal were angiographically evaluated. The distribution of lipiodol mixture was evaluated using cone beam computed tomography. RESULTS: All 5 of the retrievable coils were successfully deployed and removed. Angiography revealed successful occlusion of subsegmental artery after coil placement with flow redistribution followed by restoration of flow after coil retrieval in all cases. On cone beam computed tomography, lipiodol tagging was abundant in hepatic parenchyma supplied by the hepatic artery without coils compared with that supplied by the branch with coils. CONCLUSIONS: Temporary arterial flow redistribution using a retrievable coil was feasible in the healthy pig model and could be applicable for endovascular procedures in which superselection is difficult or unavailable.

Quantitative 4D-Digital Subtraction Angiography to Assess Changes in Hepatic Arterial Flow during Transarterial Embolization: A Feasibility Study in a Swine Model.

PURPOSE: To determine the feasibility of using time-resolved 3D-digital subtraction angiography (4D-DSA) for quantifying changes in hepatic arterial blood flow and velocity during transarterial embolization. MATERIALS AND METHODS: Hepatic arteriography and selective transarterial embolization were performed in 4 female domestic swine (mean weight, 54 kg) using 100-300-µm microspheres. Conventional 2D and 4D-DSA were performed before, during, and after each embolization. From the 4D-DSA reconstructions, blood flow and velocity values were calculated for hepatic arterial branches using a pulsatility-based algorithm. 4D-DSA velocity values were compared to those measured using an intravascular Doppler wire with a linear regression analysis. Paired t-tests were used to compare data before and after embolization. RESULTS: There was a weak-to-moderate but statistically significant correlation of flow velocities measured with 4D-DSA and the Doppler wire (r = 0.35, n = 39, P = .012). For vessels with high pulsatility, the correlation was higher (r = 0.64, n = 11, P = .034), and the relationship between 4D-DSA and the Doppler wire fit a linear model with a positive bias toward the Doppler wire (failed to reject at 95% confidence level, P = .208). 4D-DSA performed after partial embolization showed a reduction in velocity in the embolized hepatic arteries compared to pre-embolization (mean, 3.96 ± 0.74 vs 11.8 2± 2.15 cm/s, P = .006). CONCLUSION: Quantitative 4D-DSA can depict changes in hepatic arterial blood velocity during transarterial embolization in a swine model. Further work is needed to optimize 4D-DSA acquisitions and to investigate its applicability in humans.

Arterioportal shunting, splanchnic capillary perfusion, and the effects of colloids during capnoperitoneum in neonatal and adolescent pigs.

BACKGROUND: Clinical and experimental data indicate that neonates are sensitive to the CO2 pneumoperitoneum. An impaired splanchnic perfusion during laparoscopy in adults has been reported. We recently confirmed that intravenous colloids improve macrocirculatory function in neonates. We aimed to determine the impact of CO2 pneumoperitoneum on the perfusion of splanchnic organs in the young including effects of colloid application. METHODS: Male piglets (n = 25) were divided into four groups: (1) neonatal controls, (2) neonates with crystalloid restitution, (3) neonates with colloidal restitution, and (4) adolescents with crystalloid restitution. Animals were ventilated and subjected to a 3-h, 10 mmHg CO2 pneumoperitoneum followed by 2 h resuscitation. Hepatic, splanchnic, and arteriovenous shunt perfusion was assessed via central and portal venous catheters. Capillary organ flow was detected by fluorescent microspheres. The rate of bile flow was measured. RESULTS: The neonatal crystalloid group showed a significant decrease in the intestinal capillary perfusion at the end of the recovery period. This was not detectable in the adolescent and colloid group. There was a significant increase in microcirculatory arterioportal shunt flow during the CO2 pneumoperitoneum in both neonatal groups but not in the sham and adolescent groups (p < 0.05). Hepatic arterial perfusion increased after insufflation in all groups and dropped during capnoperitoneum to levels of about 70% baseline. There was no significant impairment of splanchnic perfusion or bile flow as a result of the pneumoperitoneum in all groups. CONCLUSIONS: Capillary perfusion of the abdominal organs was stable during capnoperitoneum and recovery in adolescents and neonates with colloid restitution, but not with crystalloid restitution. Significant arterioportal shunting during capnoperitoneum could affect hepatic microcirculation in neonates. Our data confirm that moderate pressure capnoperitoneum has no major effect on the perfusion of abdominal organs in neonates with adequate substitution.

Liver Doppler Findings in Pediatric Patients After Total Pancreatectomy and Islet Autotransplantation.

OBJECTIVES: This study was intended to establish normal values for velocities in the hepatic artery and portal veins in pediatric patients after total pancreatectomy and islet autotransplantation (TPIAT). METHODS: A retrospective review was performed of liver Doppler studies in pediatric patients after TPIAT over 6 years at an academic children's hospital. Doppler velocities in the liver vasculature and the hepatic artery resistive index were recorded. RESULTS: Sixty-five pediatric patients were evaluated. There were no cases of portal vein thrombosis or other hepatic vascular complications. The mean hepatic artery peak systolic velocity was 157.6 cm/s (SE, 60.9 cm/s), with a mean resistive index of 0.57 (SE, 0.09). The mean main portal vein velocity was 31.9 cm/s (SE, 12.9 cm/s). CONCLUSIONS: Portal vein thrombosis is rare in pediatric patients after TPIAT. A wide range of hepatic artery and portal vein velocities are encountered in children immediately after TPIAT without hepatic vascular complications and can be considered normal.

Numerical investigation of the effect of vessel size and distance on the cryosurgery of an adjacent tumor.

Cryosurgery is an efficient cancer treatment which can be used for non-invasive ablation of some internal tumors such as liver and prostate. Tumors are usually located near the large blood vessels and the heat convection may affect the progression of the ice ball. Hence it is necessary to predict the surgery procedure and its consequences earlier. In spite of the recent studies it is still unclear that which arteries will significantly affect the freezing treatment of tumors and which can be ignored. Therefore a numerical model of a spherical 3 cm diameter liver tumor, subjected to cryosurgery was developed. The specific thermophysical properties were applied to the tumor and healthy tissues in frozen and unfrozen states. A simplified Hepatic artery with different anatomical diameters was placed in different positions relative to the tumor and energy and momentum equations were solved. The temperature distribution and the shape of the resultant ice ball were discussed. The results showed that a 4 mm diameter artery in the vicinity of a tumor will increase the minimum temperature achieved at the tumor boundary by 12.5 °C and therefore significantly affects the cryosurgery outcome. This may cause insufficient freezing which leads to incomplete death of tumor cells, failure of the surgery and tumor regenesis. Eventually it was shown that injection of gold and Fe3O4 nanoparticles to the surrounding tissue of the artery can enhance the heat transfer and progression of the ice ball, making temperature distribution similar to the no vessel state. Development of computational models can provide the physicians an applicable tool which helps them recognize how efficient a treatment method will be for a specific case and design a suitable cryosurgery plan.

Low-Tube Voltage Computed Tomography During Hepatic Arterial Phase: The Effect of Body Habitus on Image Quality.

PURPOSE: This study aimed to evaluate the impact of body habitus factors on image quality of low-tube voltage computed tomography (CT) during the hepatic arterial phase. MATERIALS AND METHODS: Ninety-seven patients (66 men, 31 women; age range, 26-78 years) who underwent clinically indicated liver dynamic CT examination were enrolled in the study. Analysis with 80-kVp CT and intermediate tube current (277-337 mA) was performed in the late hepatic arterial phase using a 320-detector row scanner with adaptive iterative dose reduction 3-dimensional reconstruction. Patient body habitus was measured using body weight (BW), body mass index (BMI), lateral width (LW) of the abdomen, and muscle volume (MV) of the abdominal wall. On hepatic arterial phase, the mean image noise and contrast-to-noise ratio (CNR) for the aorta and liver were assessed. The correlations between body habitus factors and image quality parameters were evaluated. RESULTS: In all patients, MV showed the strongest correlation with image noise, followed by BW and LW (r = 0.684, 0.570, and 0.555, respectively). The BMI showed the fourth strongest correlation with image noise among all body habitus factors (r = 0.377). With respect to CNR of the aorta, MV and BW showed the strongest inverse correlation (r = -0.590 and -0.600, respectively), followed by LW and BMI (r = -0.557 and -0.423, respectively). Regarding the CNR of the liver, MV showed the strongest inverse correlation (r = -0.279), although the correlation efficiency was weak compared with other correlations. CONCLUSIONS: Among various body habitus factors, MV showed the strongest association with image noise and CNR in the hepatic arterial phase using 80-kVp CT.

Non-contrast-enhanced MR hepatic arteriography with time-spatial labeling inversion pulses: comparison of imaging with flow-in and modified flow-out methods.

Background In non-contrast-enhanced magnetic resonance (MR) arteriography, the flow-out method using a selective tagging pulse with a long inversion time (TI) and a non-selective inversion recovery pulse with a short TI (the modified flow-out method) might further contribute to the suppression of background signal and facilitate improved visualization of the hepatic artery. However, no report has focused on the image quality of non-contrast-enhanced MR arteriography using the modified flow-out method. Purpose To compare the flow-in method with the modified flow-out method and to determine which method better visualizes the hepatic artery. Material and Methods Twenty-seven healthy volunteers were examined using respiratory-triggered three-dimensional true steady-state free-precession MR with two selective inversion recovery pulses (the flow-in method) or with one tagging pulse and one non-selective inversion recovery pulse (the modified flow-out method). Results Artery-to-liver contrast was significantly increased in the modified flow-out method relative to the flow-in method ( P < 0.05). In all analyses of vessel visibility, non-contrast-enhanced MR arteriography using the modified flow-out method exhibited higher scores than with the flow-in method. With respect to overall image quality, the modified flow-out method was significantly better than the flow-in method ( P < 0.01). Conclusion The modified flow-out method for non-contrast-enhanced MR angiography is a promising technique for visualizing the hepatic artery.

Hepatic Arterial Buffer Response Maintains the Homeostasis of Graft Hemodynamics in Patient Receiving Living Donor Liver Transplantation.

BACKGROUND: In living donor liver transplantation (LDLT), the hepatic hemodynamics plays important roles in graft regeneration, and the hepatic blood inflows are associated with graft size. However, the data of interplay between the hepatic arterial buffer response (HABR) and graft-to-recipient weight ratio (GRWR) in clinical LDLT are lacking. AIMS: To identify the effect of the HABR on the hepatic hemodynamics and recovery of graft function and to evaluate the safe lower limit of the GRWR in carefully selected recipients. METHODS: Portal venous and hepatic arterial blood flow was measured in recipients with ultrasonography, and the graft functional recovery, various complications, and survive states after LDLT were compared. RESULTS: In total, 246 consecutive patients underwent LDLT with right lobe grafts. In total, 26 had a GRWR < 0.7 % (A), 29 had a GRWR between 0.7 and 0.8 % (B), and 181 had a GRWR > 0.8 % (C). For small-for-size syndrome, there was no significant difference (P = 0.176). Graft survival rates at 1, 3, and 5 year were not different (P = 0.710). The portal vein flow and portal vein flow per 100 g graft weight peaks were significantly higher in the A. Hepatic arterial velocity and hepatic arterial flow decreased in all the three groups on postoperative day 1; however, the hepatic arterial flow per 100 g graft weight was close to healthy controls. CONCLUSIONS: HABR played important roles not only in the homeostasis of hepatic afferent blood supply but also in maintaining enough hepatic perfusion to the graft.

[STATE OF HEPATIC HEMODYNAMICS IN TRANSPLANTATION OF ITS RIGHT PART WITH MEDIAN HEPATIC VEIN].

Peculiarities of regional hemodynamics in transplantation of right hepatic part with median hepatic vein were studied. The blood flow parameters ­ the volume portal blood flow (VPBF), linear speed of blood flow (LSBF), the resistance index (RI) in hepatic artery; phasic structure of the blood flow along hepatic veins were determined in 31 patients in accordance to ultrasonographic flowmetry data. Maximal value of VPBF was observed on a second postoperative day, minimal one ­on the fourth day. Аrterial blood flow have had enhanced immediately after transplantation up to maximal one on the second day, and from second to the fourth day ­ have had reduced to minimal one. Phasic structure of blood flow along hepatic vein have had changed postoperatively in 12 (38%) patients. Changes in the hepatosplanchnic blood flow after transplantation constitutes a consequence of the vascular resistance reduction, the venous outflow and regenerative activity of the transplanted hepatic part improvement.

Quantification of hepatic blood flow using a high-resolution phase-contrast MRI sequence with compressed sensing acceleration.

OBJECTIVE. The objective of our study was to evaluate the performance of a high-spatial-resolution 2D phase-contrast (PC) MRI technique accelerated with compressed sensing for portal vein (PV) and hepatic artery (HA) flow quantification in comparison with a standard PC MRI sequence. SUBJECTS AND METHODS. In this prospective study, two PC MRI sequences were compared, one with parallel imaging acceleration and low spatial resolution (generalized autocalibrating partial parallel acquisition [GRAPPA]) and one with compressed sensing acceleration and high spatial resolution (sparse). Seventy-six patients were assessed, including 37 patients with cirrhosis. Two observers evaluated PC image quality. Quantitative analyses yielded a mean velocity, flow, and vessel area for the PV and HA and an arterial fraction. The PC techniques were compared using the paired Wilcoxon test and Bland-Altman statistics. The sensitivity of the flow parameters to the severity of cirrhosis was also assessed. RESULTS. Vessel delineation was significantly improved using the PC sparse sequence (p < 0.034). For both in vitro and in vivo measurements, PC sparse yielded lower estimates for vessel area and flow, and larger differences between PC GRAPPA and PC sparse were observed in the HA. PV velocity and flow were significantly lower in patients with cirrhosis on both PC sparse (p < 0.001 and p = 0.042, respectively) and PC GRAPPA (p < 0.001 and p = 0.005, respectively). PV velocity correlated negatively with Child-Pugh class (r = -0.50, p < 0.001), whereas the arterial fraction measured with PC sparse was higher in patients with Child-Pugh class B or C disease than in those with Child-Pugh class A disease, with a trend toward significance (p = 0.055). CONCLUSION. A high-spatial-resolution highly accelerated compressed sensing technique (PC sparse) allows total hepatic blood flow measurements obtained in 1 breath-hold, provides improved delineation of the hepatic vessels compared with a standard PC MRI sequence (GRAPPA), and can potentially be used for the noninvasive assessment of liver cirrhosis.

[Evaluation of the blood flow in common hepatic tumors by multi-slice spiral CT whole-liver perfusion imaging].

OBJECTIVE: To study the characteristics of blood flow in common hepatic tumors by 256-slice spiral CT whole-liver perfusion imaging. METHODS: Seventy-one patients with hepatic tumors were examined retrospectively by 256-slice spiral CT whole-liver perfusion. Among them, twenty-seven cases were of primary hepatic cancer, twenty-four cases of hepatic hemangioma, and twenty cases of hepatic metastases.Regions of interest (ROIs) were placed in the tumor parenchyma (Area A), peritumoral hepatic parenchyma (Area B), and normal hepatic parenchyma (Area C), respectively. The time density curves (TDC) were drawn, and perfusion parameters including hepatic arterial perfusion(HAP), portal venous perfusion(PVP), total liver perfusion(TLP) and hepatic erfusion index(HPI) were obtained. The values of ROIs were measured, and the perfusion parameters in the areas A, B, C of different hepatic tumors were statistically analyzed. RESULTS: The values of HAP, PVP, HPI in the tumor parenchyma of primary hepatic carcinoma were (20.00 ± 11.41)ml · min(-1) · 100 ml(-1,) (32.31 ± 21.06)ml · min(-1) · 100 ml(-1,) (52.31 ± 30.55)ml · min(-1) · 100 ml(-1,) and (39.67 ± 11.19)%, showing significant difference as compared with those in peritumoral hepatic parenchyma and in normal hepatic parenchyma(P<0.05). The values of HAP, TLP, and HPI in the tumor parenchyma of hepatic hemangioma were (40.39 ± 29.23)ml · min(-1) · 100 ml(-1,) (132.72 ± 132.65) ml · min(-1) · 100 ml(-1,) and (35.51 ± 15.12)%, were significantly different as compared with those in the peritumoral hepatic parenchyma and in normal hepatic parenchyma(P<0.05). The values of HAP, PVP, HPI in the tumor parenchyma of hepatic metastases were (17.43 ± 12.27)ml · min(-1) · 100 ml(-1,) (36.19 ± 34.99) ml · min(-1) · 100 ml(-1,) and (37.86 ± 14.49)%, significantly different as compared normal hepatic parenchyma (P<0.05). The HAP, PVP, and TLP of tumor tissue and the PVP and HPI of peritumoral tissue in different hepatic tumors were statistically significantly different (P<0.05). CONCLUSIONS: The multi-slice spiral CT whole-liver perfusion has certain value in the diagnosis of common hepatic tumors. Perfusion parameters in different areas of common hepatic tumors have their own hemodynamic characteristics.

[DYNAMICS OF HEPATIC BLOOD FLOW IN IMMEDIATE PERIOD AFTER PREOPERATIVE EMBOLIZATION OF A PORTAL VEIN].

The changes in intrahepatic blood flow, occuring after embolization of right branch (ERB) of portal vein (PV) in 42 patients, to whom a major hepatic resection was planned for focal hepatic diseases, were analyzed. Together with cessation of blood flow along the PV embolized branch, there was noted the enhancement of the volume blood flow along the PV left branch by 226% on the third day after embolization with its subsequent enhancement by 337% comparing with initial one. Enhancement of a volume blood flow along right hepatic artery (HA) by 282% was noted on the third day after ERB PV with subsequent nonsignificant reduction, and a blood flow along the left hepatic artery branch did not change essentially. The blood flow enhancement in left hepatic lobe have promoted her regeneration and increase of volume of the organ residual planned.

Reproducibility study of four-dimensional flow MRI of arterial and portal venous liver hemodynamics: influence of spatio-temporal resolution.

PURPOSE: To evaluate influence of variation in spatio-temporal resolution and scan-rescan reproducibility on three-dimensional (3D) visualization and quantification of arterial and portal venous (PV) liver hemodynamics at four-dimensional (4D) flow MRI. METHODS: Scan-rescan reproducibility of 3D hemodynamic analysis of the liver was evaluated in 10 healthy volunteers using 4D flow MRI at 3T with three different spatio-temporal resolutions (2.4 × 2.0 × 2.4 mm(3), 61.2 ms; 2.5 × 2.0 × 2.4 mm(3), 81.6 ms; 2.6 × 2.5 × 2.6 mm(3), 80 ms) and thus different total scan times. Qualitative flow analysis used 3D streamlines and time-resolved particle traces. Quantitative evaluation was based on maximum and mean velocities, flow volume, and vessel lumen area in the hepatic arterial and PV systems. RESULTS: 4D flow MRI showed good interobserver variability for assessment of arterial and PV liver hemodynamics. 3D flow visualization revealed limitations for the left intrahepatic PV branch. Lower spatio-temporal resolution resulted in underestimation of arterial velocities (mean 15%, P < 0.05). For the PV system, hemodynamic analyses showed significant differences in the velocities for intrahepatic portal vein vessels (P < 0.05). Scan-rescan reproducibility was good except for flow volumes in the arterial system. CONCLUSION: 4D flow MRI for assessment of liver hemodynamics can be performed with low interobserver variability and good reproducibility. Higher spatio-temporal resolution is necessary for complete assessment of the hepatic blood flow required for clinical applications.

A novel in situ model of liver cold ischemia-reperfusion in rats.

BACKGROUND: Orthotopic liver transplantation (OLT) is being used for studying cold ischemia reperfusion (I/R)-induced injury in experimental animals, but the technique is complicated and it does not accurately reflect the pathophysiology. Here, we report a novel model, termed "in situ liver cold ischemia (ISLCI)", in Wistar rats. METHODS: ISLCI was achieved in rats by establishing a portal-jugular shunt and a cannula shunt in inferior vena cava, and the liver was continuously perfused with lactate Ringer's solution at a speed of 150 mL/h through the portal vein for 60 min. Portal venous pressure, serum levels of total bilirubin, alkaline phosphatase, alanine aminotransferase and γ-glutamyl transpeptidase (GGT), and hepatic histopathology were examined, and compared with rats undergoing OLT, in which the donor liver was subjected to a 60 min cold ischemia. RESULTS: Livers from ISLCI and OLT rats showed histopathologic changes characteristic of I/R-induced injury when examined on days 1 and 7, with complete recovery 14 d after reperfusion. Compared with OLT rats, ISLCI rats had significantly lower levels of portal venous pressure 1 and 10 min after porta hepatis clamping. They suffered a milder degree of I/R-induced hepatic injury, reflected by significantly lower levels of GGT, alanine aminotransferase, and alkaline phosphatase on day 1, and a significant lower level of GGT and a lower histopathologic score on day 7 after reperfusion. CONCLUSIONS: Our preliminary results indicate that the ISLCI model is reliable and technically easier, and is superior to OLT for studying cold I/R injury.

Computationally efficient particle release map determination for direct tumor-targeting in a representative hepatic artery system.

Implementation of a novel direct tumor-targeting technique requires a computer modeling stage to generate particle release maps (PRMs) which allow for optimal catheter positioning and selection of best injection intervals for drug-particles. This simulation task for a patient-specific PRM may require excessive computational resources and a relatively long turn-around time for a fully transient analysis. Hence, steady-state conditions were sought which generates PRMs equivalent to the pulsatile arterial flow environment. Fluid-particle transport in a representative hepatic artery system was simulated under fully transient and steady-state flow conditions and their corresponding PRMs were analyzed and compared. Comparisons of the transient PRMs from ten equal intervals of the cardiac pulse revealed that the diastolic phase produced relatively constant PRMs due to its semisteady flow conditions. Furthermore, steady-state PRMs, which best matched the transient particle release maps, were found for each interval and over the entire cardiac pulse. From these comparisons, the flow rate and outlet pressure differences proved to be important parameters for estimating the PRMs. The computational times of the fully transient and steady simulations differed greatly, i.e., about 10 days versus 0.5 to 1 h, respectively. The time-averaged scenario may provide the best steady conditions for estimating the transient particle release maps. However, given the considerable changes in the PRMs due to the accelerating and decelerating phases of the cardiac cycle, it may be better to model several steady scenarios, which encompass the wide range of flows and pressures experienced by the arterial system in order to observe how the PRMs may change throughout the pulse. While adding more computation time, this method is still significantly faster than running the full transient case. Finally, while the best steady PRMs provide a qualitative guide for best catheter placement, the final injection position could be adjusted in vivo using biodegradable mock-spheres to ensure that patient-specific optimal tumor-targeting is achieved. In general, the methodology described could generate computationally very efficient and sufficiently accurate solutions for the transient fluid-particle dynamics problem. However, future work should test this methodology in patient-specific geometries subject to various flow waveforms.

Successful treatment of a common hepatic artery pseudoaneurysm using a coronary covered stent following pancreatoduodenectomy: report of a case.

This report presents the case of a common hepatic artery (CHA) pseudoaneurysm secondary to postoperative pancreatic fistula (POPF) after pancreatoduodenectomy (PD), which was successfully treated using a coronary covered stent. A 70-year-old female underwent subtotal stomach-preserving PD for middle cholangiocarcinoma. POPF was identified on postoperative day (POD) 7, and the patient suddenly lost 500 ml of blood via the abdominal drain on POD 19. Urgent celiac arteriography revealed a CHA pseudoaneurysm. A coronary covered stent was placed to prevent rupture of the pseudoaneurysm and to maintain hepatic arterial flow, instead of performing transarterial embolization. No vascular adverse events were encountered during or after the procedure. Computed tomography and angiography showed a patent stent graft and good hepatic arterial flow 9 months after placement of the stent. Endovascular stent-graft placement not only treated the pseudoaneurysm, but also preserved the arterial blood flow. This report describes the placement of a covered stent graft for delayed hemorrhage after PD.

[Fetal hepatic artery flow assessment in prenatal diagnostics--a review of the literature]. / Ocena przeplywów w tetnicy watrobowej plodu w diagnostyce prenatalnej. Przeglad literatury.

Standards of screening tests for the most frequent fetal chromosomal defects in modern non-invasive prenatal diagnostics provide sensitivity of about 93-96%, with the false positive rate of 2.5%. During the first trimester scan, routinely performed between 11 and 13+6 week of pregnancy the calculation of the risk for chromosomal aberrations is based on maternal age (MA), nuchal translucency (NT), levels of free beta human chorionic gonadotropin (free beta-hCG), pregnancy associated plasma protein A (PAPP-A) in maternal blood, as well as the parameters from extended ultrasound examination like evaluation of the nasal bone (NB), blood flow in ductus venosus (DV), visualization of the tricuspid valve with potential regurgitation (TR) or measurement of the frontomaxillary facial angle (FMFA). The 100% detection rate remains unachievable at present, despite constantly improving guidelines for specialists, quality of imaging, and advancement in ultrasound technology Therefore, several studies have been undertaken to establish the group of 'additional markers' of chromosomal defects which, when combined with basic markers of routine screening tests, might increase the detection rate and approach it to 100%. Results of recent studies imply that evaluation of blood flow in fetal hepatic artery performed during the first trimester scan may become a new additional marker for chromosomal defects.

Decreasing the blood flow of non-compressible intra-abdominal organs with non-invasive transcutaneous electrical stimulation.

Non-invasive neuromodulation of non-compressible internal organs has significant potential for internal organ bleeding and blood-shift in aero/space medicine. The present study aims to investigate the potential influences of the non-invasive transcutaneous electrical nerve stimulation (TENS) on multiple non-compressible internal organs' blood flow. Porcine animal model (n = 8) was randomized for a total of 48 neuromodulation sessions with two different TENS stimulation frequencies (80 Hz, 10 Hz) and a placebo stimulation. A combination of two different electrode configurations (Abdominal-only or Abdominal and hind limb) were also performed. Intraarterial blood flow measurements were taken during pre and post-stimulation periods at the left renal artery, common hepatic artery, and left coronary artery. Intracranial, and extracranial arterial blood flows were also assessed with digital subtraction angiography. TENS with abdominal-only electrode configurations at 10 Hz demonstrated significant reductions in average peak blood flow velocity (APV) of the common hepatic artery (p = 0.0233) and renal arteries (p = 0.0493). Arterial pressures (p = 0.0221) were also significantly lower when renal APV was reduced. The outcome of the present study emphasises the potential use of TENS in decreasing the blood flow of non-compressible internal organs when the correct combination of electrodes configuration and frequency is used.

Effect of high blood flow on heat distribution and ablation zone during microwave ablation-numerical approach.

Microwave ablation has become a viable alternative for cancer treatment for patients who cannot undergo surgery. During this procedure, a single-slot coaxial antenna is employed to effectively deliver microwave energy to the targeted tissue. The success of the treatment was measured by the amount of ablation zone created during the ablation procedure. The significantly large blood vessel placed near the antenna causes heat dissipation by convection around the blood vessel. The heat sink effect could result in insufficient ablation, raising the risk of local tumor recurrence. In this study, we investigated the heat loss due to large blood vessels and the relationship between blood velocity and temperature distribution. The hepatic artery, with a diameter of 4 mm and a height of 50 mm and two branches, is considered in the computational domain. The temperature profile, localized tissue contraction, and ablation zones were simulated for initial blood velocities 0.05, 0.1, and 0.16 m/s using the 3D Pennes bio-heat equation, temperature-time dependent model, and cell death model, respectively. Temperature-dependent blood velocity is modeled using the Navier-Stokes equation, and the fluid-solid interaction boundary is treated as a convective boundary. For discretization, we utilized H curl Ω elements for the wave propagation model, H 1 Ω elements for the Pennes bio-heat model, and H 1 Ω 3 × L 0 2 Ω elements for the Navier-Stokes equation, where Ω represents the computational domain. The simulated results show that blood vessels and blood velocity have a significant impact on temperature distribution, tissue contraction, and the volume of the ablation zone.

Laser speckle contrast imaging for assessment of liver microcirculation.

OBJECTIVE: Laser speckle contrast imaging (LSCI) is a novel technique for microcirculation imaging not previously used in the liver. The aim of the present experimental study was to evaluate the use of LSCI for assessing liver microcirculation. MATERIALS AND METHODS: In six male Wistar rats, the median liver lobe was exposed through a midline laparotomy. Liver blood perfusion was measured simultaneously with LSCI and sidestream dark-field (SDF) imaging at baseline and during sequential temporary occlusions of the portal vein, hepatic artery, and total blood inflow occlusion. Both the inter-individual variability associated with perfusion sampling area and comparisons in perfusion measurements between both imaging techniques were investigated and validated for the application of LSCI in the liver. RESULTS: Occlusion of the hepatic artery, portal vein, and total inflow occlusion resulted in a significant decrease in LSCI signal to 74.7±6.4%, 15.0±2.3%, and 10.4±0.5% respectively (p<0.005 vs. baseline). The LSCI perfusion units correlated with sinusoidal blood flow velocity as measured with SDF imaging (Pearson's r=0.94, p<0.001). In a 10 mm diameter region of interest, as measured with LSCI, baseline inter-individual variability measured by the coefficient of variability was 13%. CONCLUSION: Alterations in LSCI signal during sequential inflow occlusions were in accordance with previously published results on hepatic hemodynamics in the rat and correlated well with our SDF imaging-derived sinusoidal blood flow velocity measurements. We found that LSCI was able to produce reproducible real-time blood perfusion measurements of hepatic microcirculation. Compared to established techniques for liver blood perfusion measurements LSCI holds the advantages of non-contact measurements over large surfaces with a high speed of data acquisition.