Alternate Cervical Venous Access Sites for Implantable Port Catheters: Experience at a Single Quaternary Care Institution.

INTRODUCTION: Clinical outcomes of implantable port catheters (IPCs) placed via alternative veins such as the external jugular and cervical collaterals have not been well established. This investigation evaluates the short- and long-term outcomes of IPCs inserted via alternate cervical veins (ACV) compared to traditionally inserted IPCs via the internal jugular vein (IJV). MATERIALS AND METHODS: A total of 24 patients who received an IPC between 2010 and 2020 via an ACV-defined as the external jugular vein, superficial cervical vein, or unnamed collateral veins-were identified. Based on power analysis, a matched control group of 72 patients who received IPCs via the IJV was identified. Non-inferiority analysis for port complications was performed between the two groups based on the selected non-inferiority margin of 20%. Secondary end points included complication-free survival and comparison of complications by the time at which they occurred. RESULTS: ACV access was non-inferior to traditional access for overall complications. Alternate access resulted in fewer complications than traditional access with an estimated reduction of - 7.0% [95% CI - 23.6%, 39.7%]. There was no significant difference in peri-procedural and post-procedural complications between the two groups. Complication-free survival was also equivalent between the two groups. CONCLUSION: IPC placement via ACVs was non-inferior to IPCs placed via traditional access through the IJV. When abnormal pathology obviates the use of IJV access, other cervical veins may be considered prior to seeking alternate locations such as femoral, translumbar, inferior vena cava, and hepatic veins.

The Impact of Injection Distance to Bifurcations on Yttrium-90 Distribution in Liver Cancer Radioembolization.

PURPOSE: To model the effect of the injection location on the distribution of yttrium-90 (90Y) microspheres in the liver during radioembolization using computational simulation and to determine the potential effects of radial movements of the catheter tip. MATERIALS AND METHODS: Numerical studies were conducted using images from a representative patient with hepatocellular carcinoma. The right hepatic artery (RHA) was segmented from contrast-enhanced cone-beam computed tomography scans. The blood flow was investigated in the trunk of the RHA using numerical simulations for 6 injection position scenarios at 2 sites located at a distance of approximately 5 and 20 mm upstream of the first bifurcation (RHA diameters of approximately 4.6 mm). The 90Y delivery to downstream vessels was calculated from the simulated hepatic artery hemodynamics. RESULTS: Varying the injection location along the RHA and across the vessel cross-section resulted in different simulated microsphere distributions in the downstream vascular bed. When the catheter tip was 5 mm upstream of the bifurcation, 90Y distribution in the downstream branches varied by as much as 53% with a 1.5-mm radial movement of the tip. However, the catheter radial movement had a weaker effect on the microsphere distribution when the injection plane was farther from the first bifurcation (20 mm), with a maximum delivery variation of 9% to a downstream branch. CONCLUSIONS: An injection location far from bifurcations is recommended to minimize the effect of radial movements of the catheter tip on the microsphere distribution.

Multiscale Computational Fluid Dynamics Modeling for Personalized Liver Cancer Radioembolization Dosimetry.

Yttrium-90 (90Y) radioembolization is a minimally invasive procedure increasingly used for advanced liver cancer treatment. In this method, radioactive microspheres are injected into the hepatic arterial bloodstream to target, irradiate, and kill cancer cells. Accurate and precise treatment planning can lead to more efficient and safer treatment by delivering a higher radiation dose to the tumor while minimizing the exposure of the surrounding liver parenchyma. Treatment planning primarily relies on the estimated radiation dose delivered to tissue. However, current methods used to estimate the dose are based on simplified assumptions that make the dosimetry results unreliable. In this work, we present a computational model to predict the radiation dose from the 90Y activity in different liver segments to provide a more realistic and personalized dosimetry. Computational fluid dynamics (CFD) simulations were performed in a 3D hepatic arterial tree model segmented from cone-beam CT angiographic data obtained from a patient with hepatocellular carcinoma (HCC). The microsphere trajectories were predicted from the velocity field. 90Y dose distribution was then calculated from the volumetric distribution of the microspheres. Two injection locations were considered for the microsphere administration, a lobar and a selective injection. Results showed that 22% and 82% of the microspheres were delivered to the tumor, after each injection, respectively, and the combination of both injections ultimately delivered 49% of the total administered 90Y microspheres to the tumor. Results also illustrated the nonhomogeneous distribution of microspheres between liver segments, indicating the importance of developing patient-specific dosimetry methods for effective radioembolization treatment.

Estimation of Yttrium-90 Distribution in Liver Radioembolization using Computational Fluid Dynamics and Deep Neural Networks.

Yttrium-90 (90Y) radioembolization is a liver cancer therapy based on 90Y microspheres injected into the hepatic artery. Current dosimetry methods used to estimate the absorbed dose in order to prescribe the 90Y activity to inject are not accurate, which can affect the treatment effectiveness. A new dosimetry based on the hemodynamics simulation of the hepatic arterial tree, CFDose, aimed at overcoming some of the limitations of the current methods. However, due to the expensive computational cost of computational fluid dynamics (CFD) simulations, this method needs to be accelerated before it can be used in real-time during treatment planning. In this paper, we introduce a convolutional neural network model trained with the CFD results of a patient with hepatocellular carcinoma to predict the 90Y distribution under different downstream vasculature resistance conditions. The model performance was evaluated using two metrics, the mean squared error and prediction accuracy. The prediction accuracy showed that the average difference between the actual and predicted data was less than 1%. The proposed model could estimate the 90Y distribution significantly faster than a CFD simulation.

Computational Modeling of the Liver Arterial Blood Flow for Microsphere Therapy: Effect of Boundary Conditions.

Transarterial embolization is a minimally invasive treatment for advanced liver cancer using microspheres loaded with a chemotherapeutic drug or radioactive yttrium-90 (90Y) that are injected into the hepatic arterial tree through a catheter. For personalized treatment, the microsphere distribution in the liver should be optimized through the injection volume and location. Computational fluid dynamics (CFD) simulations of the blood flow in the hepatic artery can help estimate this distribution if carefully parameterized. An important aspect is the choice of the boundary conditions imposed at the inlet and outlets of the computational domain. In this study, the effect of boundary conditions on the hepatic arterial tree hemodynamics was investigated. The outlet boundary conditions were modeled with three-element Windkessel circuits, representative of the downstream vasculature resistance. Results demonstrated that the downstream vasculature resistance affected the hepatic artery hemodynamics such as the velocity field, the pressure field and the blood flow streamline trajectories. Moreover, the number of microspheres received by the tumor significantly changed (more than 10% of the total injected microspheres) with downstream resistance variations. These findings suggest that patient-specific boundary conditions should be used in order to achieve a more accurate drug distribution estimation with CFD in transarterial embolization treatment planning.

Angioplasty vs stent in the treatment of transplant renal artery stenosis.

OBJECTIVE: To compare outcomes between percutaneous transluminal angioplasty and stent placement in the treatment of transplant renal artery stenosis (TRAS). METHODS: We retrospectively studied patients who underwent angiography for TRAS between 1/1/2008 and 9/20/2016 at 1 center. We compared the rates of restenosis in patients who were treated with angioplasty alone vs those who were treated with stenting. Secondary outcomes included serum creatinine and blood pressure after intervention and graft and patient survival. RESULTS: A total of 82 patients were identified as having TRAS after angiography. Restenosis occurred in 28% (16 of 58) of the angioplasty patients compared with 8% (2 of 24) of the stented patients (P = .04). Repeat angiography occurred in 14% (8 of 58) of angioplasty patients vs 13% (3 of 24) of stented patients (P = .9). The stented group had significantly higher pre-intervention stenosis (71% vs 64%, P = .01) and lower postintervention stenosis (4% vs 30%, P < .001). Serum creatinine and blood pressures were not significantly different between the 2 groups at 30, 90, or 360 days postintervention. There was no statistically significant difference in graft or patient survival between groups (P = .37). CONCLUSIONS: Stent placement resulted in fewer cases of restenosis compared with angioplasty alone, although no benefit in terms of serum creatinine, blood pressure, or patient and graft survival was shown.

Screening for Transplant Renal Artery Stenosis: Ultrasound-Based Stenosis Probability Stratification.

OBJECTIVE: The objective of our study was to evaluate which spectral Doppler ultrasound parameters are useful in patients with clinical concern for transplant renal artery stenosis (TRAS) and create mathematically derived prediction models that are based on these parameters. MATERIALS AND METHODS: The study subjects included 120 patients with clinical signs of renal dysfunction who had undergone ultrasound followed by angiography (either digital subtraction angiography or MR angiography) between January 2005 and December 2015. Five ultrasound variables were evaluated: ratio of highest renal artery velocity to iliac artery velocity, highest renal artery velocity, spectral broadening, resistive indexes, and acceleration time. Angiographic studies were categorized as either showing no stenosis or showing stenosis. Reviewers assessed the ultrasound examinations for TRAS using all five variables, which we refer to as the full model, and using a reduced number of variables, which we refer to as the reduced-variable model; sensitivities and specificities were generated. RESULTS: Ninety-seven patients had stenosis and 23 had no stenosis. The full model had a sensitivity and specificity of 97% and 91%, respectively. The reduced-variable model excluded the ratio and resistive index variables without affecting sensitivity and specificity. We applied cutoff values to the variables in the reduced-variable model, which we refer to as the simple model. Using these cutoff values, the simple model showed a sensitivity and specificity of 96% and 83%. The simple model was able to categorize patients into four risk categories for TRAS: low, intermediate, high, and very high risk. CONCLUSION: We propose a simple model that is based on highest renal artery velocity, distal spectral broadening, and acceleration time to classify patients into risk categories for TRAS.

Comparison of ferumoxytol-enhanced MRA with conventional angiography for assessment of severity of transplant renal artery stenosis.

PURPOSE: To determine the accuracy of ferumoxytol-enhanced magnetic resonance angiography (MRA) in assessing the severity of transplant renal artery stenosis (TRAS), using digital subtraction angiography (DSA) as the reference standard. MATERIALS AND METHODS: Our Institutional Review Board approved this retrospective, Health Insurance Portability and Accountability Act-compliant study. Thirty-three patients with documented clinical suspicion for TRAS (elevated serum creatinine, refractory hypertension, edema, and/or audible bruit) and/or concerning sonographic findings (elevated renal artery velocity and/or intraparenchymal parvus tardus waveforms) underwent a 1.5T MRA with ferumoxytol prior to DSA. All DSAs were independently reviewed by an interventional radiologist and served as the reference standard. The MRAs were reviewed by three readers who were blinded to the ultrasound and DSA findings for the presence and severity of TRAS. Sensitivity, specificity, and accuracy for identifying substantial stenoses (>50%) were determined. Intraclass correlation coefficients (ICCs) were calculated among readers. Mean differences between the percent stenosis from each MRA reader and DSA were calculated. RESULTS: On DSA, a total of 42 stenoses were identified in the 33 patients. The sensitivity, specificity, and accuracy of MRA in detecting substantial stenoses were 100%, 75-87.5%, and 95.2-97.6%, respectively, among the readers. There was excellent agreement among readers as to the percent stenosis (ICC = 0.82). MRA overestimated the degree of stenosis by 3.9-9.6% compared to DSA. CONCLUSION: Ferumoxytol-enhanced MRA provides high sensitivity, specificity, and accuracy for determining the severity of TRAS. Our results suggest that it can potentially be used as a noninvasive examination following ultrasound to reduce the number of unnecessary conventional angiograms. LEVEL OF EVIDENCE: 3 J. Magn. Reson. Imaging 2017;45:779-785.

Incidence of Contrast-Induced Nephropathy After Renal Graft Catheter Arteriography Using Iodine-Based Contrast Medium.

OBJECTIVE: The objective of our study was to assess the incidence of contrast-induced nephropathy (CIN), dialysis, and graft loss after direct intraarterial infusion of iodine-based contrast medium (CM) in renal allograft recipients. MATERIALS AND METHODS: One hundred patients underwent renal graft catheter arteriography between 2006 and 2014. CIN was defined as an increase in serum creatinine value of 0.5 mg/dL or more above the creatinine value before arteriography. CIN could be assessed in 37 patients with creatinine levels obtained before arteriography and 24-72 hours after arteriography. Dialysis requirement and renal allograft loss at 30 days after the procedure were recorded in all 100 patients. RESULTS: In the 37 patients who could be assessed for CIN, three patients (8%) met the criteria for CIN. In a subgroup analysis, there was an increased incidence of CIN in patients undergoing angiography alone (25%) compared with those in the angioplasty and stenting group (0%) (p = 0.028). At 30 days after the procedure, none (0/100) of the patients required dialysis or had graft failure. CONCLUSION: In a cohort of patients with a single renal allograft undergoing renal graft catheter arteriography using iodine-based CM, the overall incidence of CIN was low and no major adverse outcomes were noted at 30 days after the procedure. However, in a subgroup analysis, the patients who underwent arteriography alone-that is, without angioplasty or stenting-had a statistically significant higher rate of CIN.

Pregnancy and the working interventional radiologist.

The prevalence of women radiologists has risen in the past decade, but this rise is not reflected in interventional radiology. Women are grossly underrepresented, and this may be partly due to fear of radiation exposure, particularly during pregnancy. The simple fact is radiation exposure is minimal and the concern regarding the health of the developing fetus is unjustly aggrandized. Fully understanding the risks may help women to choose interventional radiology and practicing women interventionalists to stay productive during their child-bearing years. To date, little has been published to guide women who may become pregnant during their training and career.