Human-scale navigation of magnetic microrobots in hepatic arteries.

Using external actuation sources to navigate untethered drug-eluting microrobots in the bloodstream offers great promise in improving the selectivity of drug delivery, especially in oncology, but the current field forces are difficult to maintain with enough strength inside the human body (>70-centimeter-diameter range) to achieve this operation. Here, we present an algorithm to predict the optimal patient position with respect to gravity during endovascular microrobot navigation. Magnetic resonance navigation, using magnetic field gradients in clinical magnetic resonance imaging (MRI), is combined with the algorithm to improve the targeting efficiency of magnetic microrobots (MMRs). Using a dedicated microparticle injector, a high-precision MRI-compatible balloon inflation system, and a clinical MRI, MMRs were successfully steered into targeted lobes via the hepatic arteries of living pigs. The distribution ratio of the microrobots (roughly 2000 MMRs per pig) in the right liver lobe increased from 47.7 to 86.4% and increased in the left lobe from 52.2 to 84.1%. After passing through multiple vascular bifurcations, the number of MMRs reaching four different target liver lobes had a 1.7- to 2.6-fold increase in the navigation groups compared with the control group. Performing simulations on 19 patients with hepatocellular carcinoma (HCC) demonstrated that the proposed technique can meet the need for hepatic embolization in patients with HCC. Our technology offers selectable direction for actuator-based navigation of microrobots at the human scale.

Risk Factors for Hospitalization Duration Longer Than 24 Hours Following Percutaneous Radiofrequency Ablation of Liver Tumours.

PURPOSE: Prior studies have described complications of radiofrequency ablation (RFA) of liver tumours. The aim of this study was to identify risk factors for hospitalization duration longer than 24 hours following RFA of liver tumours. METHODS: This retrospective, single-centre study included patients with liver tumours undergoing RFA between October 2017 and July 2020. Medical records were reviewed to collect patient, tumours, and procedure characteristics for each RFA session. The association between potential risk factors and duration of hospitalization (less than or more than 24 hours) was analyzed using univariate and multivariate logistic regressions. RESULTS: Our study included 291 patients (mean age: 65.2 ± 11.2 [standard deviation]; 201 men) undergoing 324 RFA sessions. Sixty-eight sessions (21.0%) resulted in hospitalization of more than 24 hours. Multivariate analysis identified each additional needle insertion per session (OR 1.4; 95% CI [1.1-1.9]; P = .02), RFA performed in segment V (OR 2.8; 95% CI [1.4-5.7]; P = .004), and use of artificial pneumothorax (OR 14.5; 95% CI [1.4-146.0]; P = .02) as potential risk factors. A history of hepatic encephalopathy (OR 2.6; 95% CI [1.1-6.0]; P = .03) was only significant in univariate analysis. Post-hoc, subgroup analysis of patients with hepatocellular carcinoma (69.8%) did not identify other risk factors. CONCLUSION: Risk factors for a hospitalization duration longer than 24 hours include a higher number of needle insertions per session, radiofrequency ablation in segment V, and use of an artificial pneumothorax.

Morphology of Abdominal Aortic Aneurysms and Correlation with Biomechanical Tests of Aneurysmal Wall Fragments.

BACKGROUND: Evaluate how specific morphologic aspects of abdominal aortic aneurysms (AAAs), including asymmetries, curvatures, tortuosities, and angulations, among others can influence the intrinsic biomechanical properties of the AAA's wall. This study analyzed the correlation of geometric measurements (1-dimensional, 2-dimensional, and 3-dimensional) of preoperative tomographic images of AAA with uniaxial biomechanical tests of the arterial wall fragments of these AAA obtained in open surgical repair of aneurysms. METHODS: It was a multicenter, experimental, and observational study, and initially 54 individuals were selected who underwent open surgical of AAA, with valid biomechanical tests of the anterior wall of the AAA. Seven individuals were excluded because they had poor preoperative quality computed tomography scans and/or artifacts that impeded image segmentation and extraction of AAA geometric indices. The aortic fragments were subjected to uniaxial biomechanical destructive tests to obtain the following data: maximum load, failure stress, failure tension, failure strain energy, strain, and fragment thickness. In the same patients, preoperative computed tomography scans were performed with the extraction of 26 geometric indices, subdivided into 9 1-dimensional indices, 6 2-dimensional indices, and 11 3-dimensional indices. Data were subjected to statistical analysis using SPSS version 28. RESULTS: Comparing ruptured and unruptured AAA, no statistical difference was observed between the biomechanical and geometric parameters. The fragment thickness of the ruptured AAA was lower than that of the unruptured AAA (P < 0.05). By comparing tomographic geometric indices and biomechanical parameters of the aortic fragments using Pearson's coefficient, positive and linear correlations (P < 0.05) were observed between the geometric variable maximum diameter (Dmax) of the AAA with maximum load (r = 0.408), failure tension (r = 0.372), and failure stress (r = 0.360). Positive and linear correlations were also observed between the variable diameter/height ratio (DHr) and the maximum load (r = 0.360), failure tension (r = 0.354), and failure stress (r = 0.289). The geometric variable DHr was dependent and correlated with Dmax. Simple regression analysis showed that R2 varied between 8.3% and 16.7%, and all models were significant (P < 0.05). CONCLUSIONS: Dmax and DHr were linearly and positively correlated with the resistance parameters (maximum load, failure tension, and failure stress) of the AAA fragments. The DHr variable is dependent and correlated with Dmax. There was no correlation between the other geometric indices and the biomechanical parameters of the AAA wall. The asymmetries did not globally influence the biomechanics of AAA wall; however, they may influence regionally. Larger AAAs were stronger than smaller ones. Therefore, such findings may point toward Dmax is still the main geometric parameter, which influences the anterior wall, and possibly globally in the AAA.

Anterolateral territory coronary artery bypass grafting strategies: a non-inferiority randomized clinical trial: the AMI-PONT trial.

OBJECTIVES: The main objective was to assess whether a composite coronary artery bypass grafting strategy including a saphenous vein graft bridge to distribute left internal mammary artery outflow provides non-inferior patency rates compared to conventional grafting surgery with separated left internal mammary artery to left anterior descending coronary graft and aorto-coronary saphenous vein grafts to other anterolateral targets. METHODS: All patients underwent isolated grafting surgery with cardiopulmonary bypass and received ≥2 grafts/patients on the anterolateral territory. The graft patency (i.e. non-occluded) was assessed using multislice spiral computed tomography at 1 year. RESULTS: From 2012 to 2021, 208 patients were randomized to a bridge (n = 105) or conventional grafting strategy (n = 103). Patient characteristics were comparable between groups. The anterolateral graft patency was non-inferior in the composite bridge compared to conventional grafting strategy at 1 year [risk difference 0.7% (90% confidence interval -4.8 to 6.2%)]. The graft patency to the left anterior descending coronary was no different between groups (P = 0.175). Intraoperatively, the bridge group required shorter vein length for anterolateral targets (P < 0.001) and exhibited greater Doppler flow in the mammary artery pedicle (P = 0.004). The composite outcome of death, myocardial infarction or target vessel reintervention at 30 days was no different (P = 0.164). CONCLUSIONS: Anterolateral graft patency of the composite bridge grafting strategy is non-inferior to the conventional grafting strategy at 1 year. This novel grafting strategy is safe, efficient, associated with several advantages including better mammary artery flow and shorter vein requirement, and could be a valuable alternative to conventional grafting strategies. Ten-year clinical follow-up is underway. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01585285.

Transcatheter occlusion of a left ventricular outflow tract pseudoaneurysm using a "plug and coil" strategy.

Left ventricular outflow tract pseudoaneurysm is a rare and potentially fatal complication of aortic valve replacement. Surgical repair is the most common treatment and is particularly suitable for large pseudoaneurysms. Recently, there has been significant breakthroughs in the management of postoperative pseudoaneurysms via endovascular techniques. We report a case of a large postoperative pseudoaneurysm of the left ventricular outflow tract that occurred 1 year following a redo mechanical aortic valve replacement in a patient with previous valve sparing procedure performed 5 years earlier. The pseudoaneurysm was anatomically located antero-laterally between the right atrium and the ascending aorta. Successful occlusion was achieved with an Amplatzer Vascular Plug 2 (Abbott) and several coils (Terumo) via a transapical approach.

Associative Prediction of Carotid Artery Plaques Based on Ultrasound Strain Imaging and Cardiovascular Risk Factors in People Living With HIV and Age-Matched Control Subjects of the CHACS Cohort.

BACKGROUND: There is a need for a specific atherosclerotic risk assessment for people living with HIV (PLWH). SETTING: A machine learning classification model was applied to PLWH and control subjects with low-to-intermediate cardiovascular risks to identify associative predictors of diagnosed carotid artery plaques. Associations with plaques were made using strain elastography in normal sections of the common carotid artery and traditional cardiovascular risk factors. METHODS: One hundred two PLWH and 84 control subjects were recruited from the prospective Canadian HIV and Aging Cohort Study (57 ± 8 years; 159 men). Plaque presence was based on clinical ultrasound scans of left and right common carotid arteries and internal carotid arteries. A classification task for identifying subjects with plaque was defined using random forest (RF) and logistic regression models. Areas under the receiver operating characteristic curves (AUC-ROCs) were applied to select 5 among 50 combinations of 4 or less features yielding the highest AUC-ROCs. RESULTS: To retrospectively classify individuals with and without plaques, the 5 most discriminant combinations of features had AUC-ROCs between 0.76 and 0.79. AUC-ROCs from RF were statistically significantly higher than those obtained with logistic regressions ( P = 0.0001). The most discriminant features of RF classifications in PLWH were age, smoking status, maximum axial strain and pulse pressure (equal weights), and sex and antiretroviral therapy exposure (equal weights). When considering the whole population, the HIV status was identified as a cofactor associated with carotid artery plaques. CONCLUSIONS: Strain elastography adds to traditional cardiovascular risk factors for identifying individuals with carotid artery plaques.

Quantification and 3D Localization of Magnetically Navigated Superparamagnetic Particles Using MRI in Phantom and Swine Chemoembolization Models.

OBJECTIVE: Superparamagnetic nanoparticles (SPIONs) can be combined with tumor chemoembolization agents to form magnetic drug-eluting beads (MDEBs), which are navigated magnetically in the MRI scanner through the vascular system. We aim to develop a method to accurately quantify and localize these particles and to validate the method in phantoms and swine models. METHODS: MDEBs were made of Fe3O4 SPIONs. After injected known numbers of MDEBs, susceptibility artifacts in three-dimensional (3D) volumetric interpolated breath-hold examination (VIBE) sequences were acquired in glass and Polyvinyl alcohol (PVA) phantoms, and two living swine. Image processing of VIBE images provided the volume relationship between MDEBs and their artifact at different VIBE acquisitions and post-processing parameters. Simulated hepatic-artery embolization was performed in vivo with an MRI-conditional magnetic-injection system, using the volume relationship to locate and quantify MDEB distribution. RESULTS: Individual MDEBs were spatially identified, and their artifacts quantified, showing no correlation with magnetic-field orientation or sequence bandwidth, but exhibiting a relationship with echo time and providing a linear volume relationship. Two MDEB aggregates were magnetically steered into desired liver regions while the other 19 had no steering, and 25 aggregates were injected into another swine without steering. The MDEBs were spatially identified and the volume relationship showed accuracy in assessing the number of the MDEBs, with small errors (≤ 8.8%). CONCLUSION AND SIGNIFICANCE: MDEBs were able to be steered into desired body regions and then localized using 3D VIBE sequences. The resulting volume relationship was linear, robust, and allowed for quantitative analysis of the MDEB distribution.

Management of Pancreatico-duodenal arterio-venous malformation.

PURPOSE: To describe the interventional management and clinical outcome of pancreatico-duodenal arterio-venous malformations (PDAVMs). MATERIAL AND METHODS: Seven patients presenting a PDAVM (6 women, 1 male; mean age: 61) were retrospectively reviewed. Technical, clinical success and complications of embolization and surgical management of symptomatic PDAVMs were assessed. Technical success was defined as a complete occlusion of the PDAVM and clinical success as no clinical symptom or recurrence during follow-up. Patients with asymptomatic PDAVMs were followed clinically, by Doppler ultrasound and CT-angiography. RESULTS: Mean follow-up time was 69 months (15-180). Five symptomatic patients presented with upper gastrointestinal bleeding (n=3), ascites (n=1), and abdominal pain (n=1). Two patients were asymptomatic. The PDAVMs were classified as follow: Yakes I (1), IIIa (2), IIIb (3) and IV (1). Five symptomatic patients were treated with 9 embolization sessions with arterial approach (onyx®, glue, coils) in 7 and venous approach in 2 (plugs, coils, covered stents, STS foam and onyx®). Technical success of embolization was 60% (3/5). Devascularization was incomplete for 2 Yakes IIIB patients. Clinical success of embolization was estimated at 80% (4/5) as one patient required additional surgery (Whipple) because of persistent bleeding. One splenic vein thrombosis was treated successfully by mechanical thrombectomy and heparin. No recurrence occurred during follow-up. No progression was documented in asymptomatic patients. CONCLUSION: Embolization of symptomatic PDAVMs is effective and surgery should be performed in second intention. Complete devascularization is more difficult to obtain in Yakes III PDAVM.

Impact of calcification modeling to improve image fusion accuracy for endovascular aortic aneurysm repair.

Since the 1990s, endovascular aortic aneurysm repair (EVAR) has become a common alternative to open surgery for the treatment of abdominal aortic aneurysms (AAAs). To aid the deployment of stent-grafts, fluoroscopic image guidance can be enhanced using preoperative simulation and intraoperative image fusion techniques. However, the impact of calcification (Ca) presence on the guidance accuracy of such techniques is yet to be considered. In the present work, we introduce a guidance tool that accounts for patient-specific Ca presence. Numerical simulations of EVAR were developed for 12 elective AAA patients, both with (With-Ca) and without (No-Ca) Ca consideration. To assess the accuracy of the simulations, the image results were overlaid on corresponding intraoperative images and the overlay error was measured at selected anatomical landmarks. With this approach we gained insight into the impact of Ca presence on image fusion accuracy. Inclusion of Ca improved mean image fusion accuracy by 8.68 ± 4.59%. In addition, a positive correlation between the relative Ca presence and the image fusion accuracy was found (R = .753, p < .005). Our results suggest that considering Ca presence in patient-specific EVAR simulations increases the reliability of EVAR image guidance techniques that utilize numerical simulation, especially for patients with severe aortic Ca presence.

Systemic, local, and sclerotherapy drugs: What do we know about drug prescribing in vascular anomalies?

Off-label drug prescribing, frequent in the treatment of vascular anomalies (VA), relies on the quality of the literature reporting drug efficacy and safety. Our objective is to review the level of evidence (LOE) surrounding drug use in VA, which is more prevalent in pediatric care. A list of drugs used in VA was created with a literature review in July 2020. For each drug listed, the article displaying the highest LOE was determined and then compared between efficacy/safety data, routes of administration, pharmacological categories and a subset of VA. The influence of research quality on study results was also explored. The median LOE for the 74 drugs identified poor methodological quality, with a predominance of retrospective studies or case reports. Drug safety is currently inadequately reported. This is alarming as many treatments display significant safety concerns. Also, current literature displays major publication bias that probably leads to overestimation of drug efficacy in VA.

Off-Label Use and Safety of Drug Use in Vascular Anomalies.

BACKGROUND: Off-label drug use is associated with an increased risk of adverse drug reactions. It is common in pediatrics and in rare diseases, which are two characteristics applying to vascular anomalies (VA). OBJECTIVES: The aim of this work was to quantify off-label drug use in VA and assess its safety. METHODS: A review was conducted to extract a list of drugs used in VA management. A drug was considered to have significant safety concerns if a black box warning was present or if a serious adverse drug reaction (SADR) was reported in at least 1% of the patients (SADR is defined as a noxious and unintended response to a drug that occurs at any dose and results in hospitalization, prolongation of existing hospitalization, congenital malformation, persistent or significant disability or incapacity, life-threatening condition, or death). The labelling status and safety of each drug was assessed based on the product monograph, Micromedex, and the FDA data. RESULTS: We found that 98.9% of the inventoried drugs were used off-label or unlicensed for VA management. Only the oral solution of propranolol hydrochloride (Hemangeol®) for the treatment of infantile hemangiomas is approved. Significant safety issues concerned 73% of the drugs and were more frequent among systemic than locally delivered drugs. CONCLUSIONS: Off-label drug use in VA is the rule and not the exception. Significant safety concerns are common. It is necessary to carefully weigh risk and benefits for every patient when using systemic and local treatments carrying safety concerns. Patients should be openly informed and involved in the decision-making process.

The feasibility of degradable glass microspheres as transient embolic medical devices.

The deliberate occlusion of blood flow through transarterial embolization is currently being used to treat conditions ranging from hemorrhages to hypervascular tumors. Degradable, imageable high borate glass microspheres (BRS2) were developed and tested to improve lesion targeting and promote a temporary vascular occlusion which is sufficient for most embolization procedure. A 48 hour pilot study, in a swine renal model, was conducted to assess the embolization effectiveness and potential risks of this new embolic agent. Bilateral embolization of the caudal branch of the renal arteries using test and control particles were performed in 4 pigs. Embolization efficacy, recanalization and resulting ischemia were evaluated at different time frame (0, 24 and 48 hours). The primary outcomes for this study were the assessment of: (i) embolization effectiveness, and (ii) vessel recanalization. The test article was found to occlude vessels as effectively as the control microspheres, with the use of a smaller volume of microspheres. At the 24 hour time point, over 95% of the material was found to be completely degraded, although little to no recanalization was observed. This data suggests that BRS2 is an effective embolic agent, however further investigations into the method of delivery are required prior to clinical implementation.

FairEmbo Concept for Arterial Embolizations: In Vivo Feasibility and Safety Study with Suture-Based Microparticles Compared with Microspheres.

PURPOSE: Microspheres are effective embolic agents, especially for the management of bleeding and oncologic lesions. The first FairEmbo study reported the effectiveness of embolization using suture fragments. The effectiveness and safety of arterial embolization with suture-based microparticles (SBM) were assessed in a swine model. MATERIALS AND METHODS: In this ethical-approved animal study, a polar artery in each kidney was embolized in four swine: one side with hand-cut non-absorbable SBM (Flexocrin 2®) and the contralateral side with Embozene® 900 for comparison. Swine were followed for 3 months (M3) to evaluate the effectiveness and the safety of SBM. Follow-up protocol included clinical monitoring, computed tomography (CT) control and digital subtraction angiography (DSA), followed by histological analyses. The SBM confection parameters were evaluated by automatic microscopic sizer. RStudio software and Mann-Whitney test (significance at P < 0.05) were used for statistics. RESULTS: The average size of SBM was 1002 µm (SD = 258). All targets were effectively embolized by SBM with an angiogram defect estimated at 45.6% (95% CI [35.9-55.2]), compared to 40.5% (95% CI [30.6-55.5]) for Embozene® group (P = 0.342). The average duration of SBM embolization procedure was significantly increased compared to Embozene® embolization (1202 s versus 222 s, P = 0.029). There were no statistical differences in M3 DSA and CT for SBM and Embozene®, with persistence of partial arterial occlusion and atrophic embolized area. No postoperative complications were observed on clinical and CT controls. CONCLUSION: This experimental study suggests that embolization with SBM is feasible, safe and effective in short- and medium-term follow-up as compared to microspheres.

The Canadian Association for Interventional Radiology (CAIR) and Canadian Association of Radiologists (CAR) Guidelines for Interventional Radiology Procedures for Patients With Suspected or Confirmed COVID-19.

The current coronavirus disease 2019 (COVID-19) pandemic is creating significant challenges to the Canadian health system, including the practice of interventional radiology (IR). Interventional radiology will continue to play an important role in patient care, during this crisis. This document serves to guide interventional and general radiologists in safely performing IR procedures on patients with suspected or confirmed COVID-19, using the best evidence, guidelines and expert recommendations available. These strategies include reviewing procedural indications, development of tactics to minimize cross contamination prior to the intervention, appropriate usage of personal protection equipment according to the type of procedure (along with defining aerosol-generating procedures in IR), along with developing the appropriate work environment during the COVID-19 pandemic. By adopting the policies described, hospitals will protect the interventional radiologists, medical radiation technologists, nurses, ancillary staff, along with patients who benefit from their care.

Feasibility of shear wave sonoelastography to detect endoleak and evaluate thrombus organization after endovascular repair of abdominal aortic aneurysm.

PURPOSE: To investigate the feasibility of shear wave sonoelastography (SWS) for endoleak detection and thrombus characterization of abdominal aortic aneurysm (AAA) after endovascular repair (EVAR). MATERIALS AND METHODS: Participants who underwent EVAR were prospectively recruited between November 2014 and March 2016 and followed until March 2019. Elasticity maps of AAA were computed using SWS and compared to computed tomography angiography (CTA) and color Doppler ultrasound (CDUS). Two readers, blinded to the CTA and CDUS results, reviewed elasticity maps and B-mode images to detect endoleaks. Three or more CTAs per participant were analyzed: pre-EVAR, baseline post-EVAR, and follow-ups. The primary endpoint was endoleak detection. Secondary endpoints included correlation between total thrombus elasticity, proportion of fresh thrombus, and aneurysm growth between baseline and reference CTAs. A 3-year follow-up was made to detect missed endoleaks, EVAR complication, and mortality. Data analyses included Cohen's kappa; sensitivity, specificity, and positive predictive value (PPV); Pearson coefficient; and Student's t tests. RESULTS: Seven endoleaks in 28 participants were detected by the two SWS readers (k = 0.858). Sensitivity of endoleak detection with SWS was 100%; specificity and PPV averaged 67% and 50%, respectively. CDUS sensitivity was estimated at 43%. Aneurysm growth was significantly greater in the endoleak group compared to sealed AAAs. No correlation between growth and thrombus elasticity or proportion of fresh thrombus in AAAs was found. No new endoleaks were observed in participants with SWS negative studies. CONCLUSION: SWS has the potential to detect endoleaks in AAA after EVAR with comparable sensitivity to CTA and superior sensitivity to CDUS. KEY POINTS: • Dynamic elastography with shear wave sonoelastography (SWS) detected 100% of endoleaks in abdominal aortic aneurysm (AAA) follow-up that were identified by a combination of CT angiography (CTA) and color Doppler ultrasound (CDUS). • Based on elasticity maps, SWS differentiated endoleaks from thrombi within the aneurysm sac (p < 0.001). • After 3-year follow-up, no new endoleaks were observed in SWS negative examinations.

Interventional Management of Arteriovenous Malformations.

Arteriovenous malformations (AVMs) are fast flow malformations characterized by the presence of arteriovenous shunting. These congenital lesions can be evolutive, leading to serious complications such as bleeding, skin ulceration, and cardiac failure. The interventional radiologist plays an important role in the management of these patients. He should be involved in the clinical evaluation to make the proper diagnosis, evaluate the symptoms and potential indication for endovascular treatment. This evaluation should be done in a multidisciplinary clinic with access to plastic surgeons, internal medicine and dermatologist, as well as specific specialists that might need to be implicated (ENT surgeon in the face and neck area, for example). The Schobinger clinical classification is important to assess patient evolution and indicate intervention. We recommend to treat symptomatic or evolutive AVMs. Doppler ultrasound is the first imaging examination that should be performed. Then, MR angiography or computed tomography angiography (CTA) can be proposed depending on the anatomic area involved. Embolization is currently the first line of treatment for these patients. There is currently promising research in the identification of genetic markers and molecular target(s) but there is no recognized pharmacologic treatment for AVM available yet. Digital substraction angiography (DSA) is usually performed for guidance during the embolization session but is also essential to properly classify a specific lesion, according to its anatomy. The anatomic classifications proposed by Cho and Yakes are both useful to choose the best therapeutic approach: Endovascular, direct puncture, retrograde venous approach or a combination of these techniques. Ethanol is the most efficient agent but is at higher risk of skin necrosis and nerve injury and should therefore be used with caution in dangerous territories. Glue and Onyx are liquid agents that are also well suited to occlude the nidus; they can be used in association with ethanol. On the venous side, mechanical occlusion with coils or Amplatzer plugs is mostly used. Again, they can be used in association with a liquid agent (Ethanol, glue or Onyx) to reflux in the nidus. Surgery can be indicated to resect residual AVM following embolization if residual symptoms are present and the planned surgery is feasible, with relative safety.

Common (Cystic) Lymphatic Malformations: Current Knowledge and Management.

The approach to treating common (cystic) lymphatic malformations (LMs) has evolved significantly over the last decade due to clinical research and recent developments in molecular biology. Surgery, sclerosing agents, and medical drugs with specific targets for biological therapy have been reported for the management of LMs. We will discuss the importance to standardize the location and imaging characterization of LMs to improve the knowledge about the outcome of the different therapeutic options. Our goal is to help the reader understand the different options for the management of LMs with the balance between risk and benefit for the patients.

Magnetic Resonance Navigation for Targeted Embolization in a Two-Level Bifurcation Phantom.

This work combines a particle injection system with our proposed magnetic resonance navigation (MRN) sequence with the intention of validating MRN in a two-bifurcation phantom for endovascular treatment of hepatocellular carcinoma (HCC). A theoretical physical model used to calculate the most appropriate size of the magnetic drug-eluting bead (MDEB, 200 µm) aggregates was proposed. The aggregates were injected into the phantom by a dedicated particle injector while a trigger signal was automatically sent to the MRI to start MRN which consists of interleaved tracking and steering sequences. When the main branch of the phantom was parallel to B0, the aggregate distribution ratio in the (left-left, left-right, right-left and right-right divisions was obtained with results of 8, 68, 24 and 0% respectively at baseline (no MRN) and increased to 84%, 100, 84 and 92% (p < 0.001, p = 0.004, p < 0.001, p < 0.001) after implementing our MRN protocol. When the main branch was perpendicular to B0, the right-left branch, having the smallest baseline distribution rate of 0%, reached 80% (p < 0.001) after applying MRN. Moreover, the success rate of MRN was always more than 92% at the 1st bifurcation in the experiments above.

Dynamic contrast-enhanced MRI to assess hepatocellular carcinoma response to Transarterial chemoembolization using LI-RADS criteria: A pilot study.

PURPOSE: To identify quantitative dynamic contrast-enhanced (DCE)-MRI perfusion parameters indicating tumor response of hepatocellular carcinoma (HCC) to transarterial chemoembolization (TACE). MATERIALS AND METHODS: This prospective pilot study was approved by our institutional review board; written and informed consent was obtained for each participant. Patients underwent DCE-MRI examinations before and after TACE. A variable flip-angle unenhanced 3D mDixon sequence was performed for T1 mapping. A dynamic 4D mDixon sequence was performed after contrast injection for assessing dynamic signal enhancement. Nonparametric analysis was conducted on the time-intensity curves. Parametric analysis was performed on the time-concentration curves using a dual-input single-compartment model. Treatment response according to Liver Reporting and Data System (LI-RADS) v2018 was used as the reference standard. The comparisons within groups (before vs. after treatment) and between groups (nonviable vs. equivocal or viable tumor) were performed using nonparametric bootstrap taking into account the clustering effect of lesions in patients. RESULTS: Twenty-eight patients with 52 HCCs (size: 10-104 mm) were evaluated. For nonviable tumors (n = 27), time to peak increased from 62.5 ±â€¯18.2 s before to 83.3 ±â€¯12.8 s after treatment (P< 0.01). For equivocal or viable tumors (n = 25), time to peak and mean transit time significantly increased (from 54.4 ±â€¯24.1 s to 69.5 ±â€¯18.9 s, P < 0.01 and from 14.2 ±â€¯11.8 s to 33.9 ±â€¯36.8 s, P= 0.01, respectively) and the transfer constant from the extracellular and extravascular space to the central vein significantly decreased from 14.8 ±â€¯14.1 to 8.1 ±â€¯9.1 s-1 after treatment (P= 0.01). CONCLUSION: This prospective pilot DCE-MRI study showed that time to peak significantly changed after TACE treatment for both groups (nonviable tumors and equivocal or viable tumors). In our cohort, several perfusion parameters may provide an objective marker for differentiation of treatment response after TACE in HCC patients.