Feasibility of non-contrast-enhanced magnetic resonance angiography for imaging upper extremity vasculature prior to vascular access creation

Pediatric hemodialysis access

Pediatric hemodialysis access is a demanding field. Procedures are infrequent, technically challenging, and associated with high complication and failure rates. Each procedure affects subsequent access and transplants sites. The choice is made easier and outcomes improved when access decisions are made by a multidisciplinary, pediatric, hemodialysis access team. This manuscript reviews the current literature and offers technical suggestions to improve outcomes.

High-resolution, non-contrast-enhanced magnetic resonance angiography of the wrist, hand and digital arteries using optimized implementation of Cartesian quiescent interval slice selective (QISS) at 1.5 T

PURPOSE

Non-contrast-enhanced (CE) magnetic resonance angiography (MRA) techniques are of considerable interest for diagnosing vascular diseases in the upper extremities owing to the possibility of repeated examinations, sufficient coverage of the measurement volume, and because possible side effects of administering iodine- or gadolinium-based contrast agents and radiation exposure can be avoided. The aim of this study was to investigate the feasibility of an optimized electrocardiogram (ECG) triggered Cartesian quiescent interval slice selective (QISS) technique for MRA of hand arteries.

MATERIAL AND METHODS

Both hands of 20 healthy volunteers (HVs) were examined using an optimized QISS-MRA pulse sequence at 1.5 Tesla. The wrist and hand arterial trees were divided into 36 segments. Cross-sectional areas (CSA) of all arterial segments were measured. For the technical evaluation of the pulse sequence, the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were computed and six imaging artifacts were graded. Two experienced observers used an ordinal scoring system to assess the image quality of each arterial segment. Interobserver agreement was determined.

RESULTS

The median CSA was 7.3 mm2 in the ulnar and radial artery, 3.2 mm2 in the four common digital arteries, and 1.5 mm2 in five proper digital arteries. The median SNR and CNR of the third common proper arteries were 45.9 and 20.3, respectively. None of the arterial segments were contaminated by venous enhancement. The image quality of arterial segments for both hands was considered as diagnostic in 87.2% of all 1440 segments. An interobserver agreement of 0.67 for both hands was determined for image quality of arterial segments using a five-grade scoring system. Optimized QISS-MRA allows as the first MRA technique the classification of superficial palmar arch (SPA) and deep palmar arch (DPA) variants. 5 new SPA and 6 new DPA variants could be classified using QISS-MRA in comparison with previous studies using CE computed tomography angiography and using fixed cadaver hands.

CONCLUSIONS

By using this optimized 2D Cartesian QISS-MRA protocol, contrast agent-free angiography of the wrist and hand arteries provided a high in-plane spatial resolution and an excellent visualization of small digital arteries.

SCMR Position Paper (2020) on clinical indications for cardiovascular magnetic resonance

The Society for Cardiovascular Magnetic Resonance (SCMR) last published its comprehensive expert panel report of clinical indications for CMR in 2004. This new Consensus Panel report brings those indications up to date for 2020 and includes the very substantial increase in scanning techniques, clinical applicability and adoption of CMR worldwide. We have used a nearly identical grading system for indications as in 2004 to ensure comparability with the previous report but have added the presence of randomized controlled trials as evidence for level 1 indications. In addition to the text, tables of the consensus indication levels are included for rapid assimilation and illustrative figures of some key techniques are provided.

KDOQI Clinical Practice Guideline for Vascular Access: 2019 Update

The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) has provided evidence-based guidelines for hemodialysis vascular access since 1996. Since the last update in 2006, there has been a great accumulation of new evidence and sophistication in the guidelines process. The 2019 update to the KDOQI Clinical Practice Guideline for Vascular Access is a comprehensive document intended to assist multidisciplinary practitioners care for chronic kidney disease patients and their vascular access. New topics include the end-stage kidney disease "Life-Plan" and related concepts, guidance on vascular access choice, new targets for arteriovenous access (fistulas and grafts) and central venous catheters, management of specific complications, and renewed approaches to some older topics. Appraisal of the quality of the evidence was independently conducted by using a Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach, and interpretation and application followed the GRADE Evidence to Decision frameworks. As applicable, each guideline statement is accompanied by rationale/background information, a detailed justification, monitoring and evaluation guidance, implementation considerations, special discussions, and recommendations for future research.

Preoperative management of arteriovenous fistula (AVF) for hemodialysis

Native arteriovenous fistula (AVF) is the favorite access for hemodialysis (HD). The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) recommends its creation in most patients with renal failure. Unfortunately, intensive efforts to promote native AVF in patients with marginal vessels have increased the rate of primary fistula failure. A non-functioning fistula prompts the use of central venous catheter (CVC) that, unlike AVF, has been associated with an increased risk of morbidity and mortality among patients receiving HD. We believe that successful and timely AVF placement relies on the development of a multidisciplinary integrated preoperative program divided into five stages: (i) management of patients with advanced chronic kidney disease (CKD), (ii) management of preoperative risk factors for AVF failure, (iii) planning of native AVF, (iv) assessment of patient eligibility and (v) preoperative vascular mapping. Focusing specifically on native AVF, we review scientific evidence regarding preoperative management of this vascular access in order to favor construction of long-term functioning fistula minimizing development of severe complications.

Ultra-high field upper extremity peripheral nerve and non-contrast enhanced vascular imaging

OBJECTIVE

The purpose of this study was to explore the efficacy of Ultra-high field [UHF] 7 Tesla [T] MRI as compared to 3T MRI in non-contrast enhanced [nCE] imaging of structural anatomy in the elbow, forearm, and hand [upper extremity].

MATERIALS AND METHOD

A wide range of sequences including T1 weighted [T1] volumetric interpolate breath-hold exam [VIBE], T2 weighted [T2] double-echo steady state [DESS], susceptibility weighted imaging [SWI], time-of-flight [TOF], diffusion tensor imaging [DTI], and diffusion spectrum imaging [DSI] were optimized and incorporated with a radiofrequency [RF] coil system composed of a transverse electromagnetic [TEM] transmit coil combined with an 8-channel receive-only array for 7T upper extremity [UE] imaging. In addition, Siemens optimized protocol/sequences were used on a 3T scanner and the resulting images from T1 VIBE and T2 DESS were compared to that obtained at 7T qualitatively and quantitatively [SWI was only qualitatively compared]. DSI studio was utilized to identify nerves based on analysis of diffusion weighted derived fractional anisotropy images. Images of forearm vasculature were extracted using a paint grow manual segmentation method based on MIPAV [Medical Image Processing, Analysis, and Visualization].

RESULTS

High resolution and high quality signal-to-noise ratio [SNR] and contrast-to-noise ratio [CNR]-images of the hand, forearm, and elbow were acquired with nearly homogeneous 7T excitation. Measured [performed on the T1 VIBE and T2 DESS sequences] SNR and CNR values were almost doubled at 7T vs. 3T. Cartilage, synovial fluid and tendon structures could be seen with higher clarity in the 7T T1 and T2 weighted images. SWI allowed high resolution and better quality imaging of large and medium sized arteries and veins, capillary networks and arteriovenous anastomoses at 7T when compared to 3T. 7T diffusion weighted sequence [not performed at 3T] demonstrates that the forearm nerves are clearly delineated by fiber tractography. The proper digital palmar arteries and superficial palmar arch could also be clearly visualized using TOF nCE 7T MRI.

CONCLUSION

Ultra-high resolution neurovascular imaging in upper extremities is possible at 7T without use of renal toxic intravenous contrast. 7T MRI can provide superior peripheral nerve [based on fiber anisotropy and diffusion coefficient parameters derived from diffusion tensor/spectrum imaging] and vascular [nCE MRA and vessel segmentation] imaging.

Upper extremity non-contrast magnetic resonance venography (MRV) compared to contrast enhanced MRV and ultrasound

PURPOSE

To assess feasibility, image quality and measured venous caliber of non-contrast MRV (NC-MRV) of central and upper extremity veins, compared to contrast-enhanced MRV (CE-MRV) and ultrasound (US) in healthy volunteers.

MATERIALS AND METHODS

10 subjects underwent NC-MRV and CE-MRV at 1.5 T, with comparison to US. Two radiologists evaluated MRI for image quality (IQ) and venous caliber.

RESULTS AND CONCLUSIONS

NC-MRV is feasible, with inferior IQ but comparable venous caliber measurements CE-MRV (mean 7.9±4.58 mm vs. 7.83±4.62, p=0.13). Slightly larger upper limb caliber measurements were derived for NC-MRV and CE-MRV compared to US (NC-MRV 5.2±1.8 mm, CE-MRV 4.9±1.6 mm, US 4.5±1.8 mm, both p<0.001).

Noncontrast Magnetic Resonance Angiography Using Inflow Sensitive Inversion Recovery Technique for Vascular Evaluation in Pre-liver Transplantation Recipients

OBJECTIVE

Vascular anatomy is essential in pretransplantation survey. The purpose of this study is to investigate the feasibility and diagnostic performance of inflow sensitive inversion recovery (IFIR) magnetic resonance angiography (MRA) to evaluate the recipient's hepatic vasculature before liver transplantation.

MATERIALS AND METHODS

Thirty-one pre-liver transplantation patients underwent both IFIR and conventional contrast-enhanced MRA using a 1.5T MR scanner from December 2012 to December 2014. The contrast-to-noise ratios (CNRs) between liver parenchyma and hepatic vasculature were calculated. The image sets of IFIR and contrast-enhanced MRA were assessed for subjective image quality and depiction of hepatic vasculature on vessel-to-vessel basis by two independent radiologists.

RESULTS

The quantitative results of CNR for hepatic arteries on IFIR were significantly lower than contrast-enhanced MRA, whereas CNR for portal veins and inferior vena cava on IFIR were significantly higher than contrast-enhanced MRA. For subjective assessment of image quality, the overall agreement of scores of IFIR and contrast-enhanced MRA was substantial (kappa values ranged from 0.650 to 0.767). There was no significant difference in the image quality for portal veins between IFIR and contrast-enhanced MRA. The quality scores of IFIR were significantly lower than contrast-enhanced MRA for hepatic arteries. For inferior vena cava evaluation, the scores of IFIR were significantly higher than contrast-enhanced MRA.

CONCLUSION

IFIR MRA is a reproducible and noninvasive tool to assess the hepatic vasculature that can provide adequate to good image quality. In pre-liver transplantation patients, IFIR MRA becomes even more useful if contrast medium is a contraindication due to impaired renal and liver functions.

Transitional Flow in the Venous Side of Patient-Specific Arteriovenous Fistulae for Hemodialysis

Arteriovenous fistula (AVF) is the first choice for providing vascular access for hemodialysis patients, but maintaining its patency is challenging. AVF failure is primarily due to development of neointimal hyperplasia (NH) and subsequent stenosis. Using idealized models of AVF we previously suggested that reciprocating hemodynamic wall shear is implicated in vessel stenosis. The aim of the present study was to investigate local hemodynamics in patient-specific side-to-end AVF. We reconstructed realistic geometrical models of four AVFs from magnetic resonance images acquired in a previous clinical study. High-resolution computational fluid dynamics simulations using patient-specific blood rheology and flow boundary conditions were performed. We then characterized the flow field and categorized disturbed flow areas by means of established hemodynamic wall parameters. In all AVF, either in upper or lower arm location, we consistently observed transitional laminar to turbulent-like flow developing in the juxta-anastomotic vein and damping towards the venous outflow, but not in the proximal artery. High-frequency fluctuations of the velocity vectors in these areas result in eddies that induce similar oscillations of wall shear stress vector. This condition may importantly impair the physiological response of endothelial cells to blood flow and be responsible for NH formation in newly created AVF.

Noncontrast magnetic resonance angiography: concepts and clinical applications

Many noncontrast magnetic resonance angiography techniques have recently been developed in response to concerns about gadolinium in patients with renal impairment. This article describes the theory behind established and recently described techniques and how and where they can be performed in clinical practice.

Current tools for prediction of arteriovenous fistula outcomes

It remains challenging to accurately predict whether an individual arteriovenous fistula (AVF) will mature and be useable for haemodialysis vascular access. Current best practice involves the use of routine clinical assessment and ultrasonography complemented by selective venography and magnetic resonance imaging. The purpose of this literature review is to describe current practices in relation to pre-operative assessment prior to AVF formation and highlight potential areas for future research to improve the clinical prediction of AVF outcomes.

Radiological Assessment of Vascular access in Haemodialysis Patients

Clinical examination is still the most important diagnostic tool and duplex ultrasonography is the imaging method of first choice. Radiological assessment of vascular access for haemodialysis includes preoperative analysis of vessel anatomy and postoperative surveillance for access maturation as well as diagnosis in vascular access insufficiency. Compared to ultrasonography digital subtraction angiography is superior for the evaluation of the central veins and allows diagnosis and treatment in one session. Computed tomography should only be used in patients with inconclusive ultrasonography results, for example, for the assessment of the central veins and visualization of the vascular tree. Gadolinium-enhanced magnetic resonance imaging is no longer recommended in dialysis patients, because it may trigger nephrogenic systemic fibrosis. In patients with a history of previous central venous catheters additional preoperative imaging of the central veins should be performed. In this article we review the different radiological imaging methods for preoperative assessment and suspected vascular access dysfunction.

Diagnostic accuracy of computer tomography angiography and magnetic resonance angiography in the stenosis detection of autologuous hemodialysis access: a meta-analysis

Purpose

To compare the diagnostic performances of computer tomography angiography (CTA) and magnetic resonance angiography (MRA) for detection and assessment of stenosis in patients with autologuous hemodialysis access.

Materials and Methods

Search of PubMed, MEDLINE, EMBASE and Cochrane Library database from January 1984 to May 2013 for studies comparing CTA or MRA with DSA or surgery for autologuous hemodialysis access. Eligible studies were in English language, aimed to detect more than 50% stenosis or occlusion of autologuous vascular access in hemodialysis patients with CTA and MRA technology and provided sufficient data about diagnosis performance. Methodological quality was assessed by the Quality Assessment of Diagnostic Studies (QUADAS) instrument. Sensitivities (SEN), specificities (SPE), positive likelihood ratio (PLR), negative likelihood values (NLR), diagnostic odds ratio (DOR) and areas under the receiver operator characteristic curve (AUC) were pooled statistically. Potential threshold effect, heterogeneity and publication bias was evaluated. The clinical utility of CTA and MRA in detection of stenosis was also investigated.

Result

Sixteen eligible studies were included, with a total of 500 patients. Both CTA and MRA were accurate modality (sensitivity, 96.2% and 95.4%, respectively; specificity, 97.1 and 96.1%, respectively; DOR [diagnostic odds ratio], 393.69 and 211.47, respectively) for hemodialysis vascular access. No significant difference was detected between the diagnostic performance of CTA (AUC, 0.988) and MRA (AUC, 0.982). Meta-regression analyses and subgroup analyses revealed no statistical difference. The Deek’s funnel plots suggested a publication bias.

Conclusion

Diagnostic performance of CTA and MRA for detecting stenosis of hemodialysis vascular access had no statistical difference. Both techniques may function as an alternative or an important complement to conventional digital subtraction angiography (DSA) and may be able to help guide medical management.

Non Contrast-Enhanced MRA versus Ultrasound Blood Vessel Assessment to determine the Choice of Hemodialysis Vascular Access

Purpose

The aim of this work was to establish the relationship between traditional blood vessel mapping for vascular access (VA) creation by B-mode ultrasound (US) and novel non contrast-enhanced magnetic resonance angiography (NCE-MRA), and to study the potential influence of the diameter assessment technique on the choice of hemodialysis vascular access.

Methods

A total of 27 end-stage renal-disease patients were included. They received routine US and a NCE-MRA examination of the upper extremity. Diameters were measured manually on US and semi-automatically on NCE-MRA. These measurements were statistically compared for the arteries and veins and for each measurement location. Furthermore, sensitivity and specificity of both modalities to predict VA location was investigated by comparison with an experienced surgeon. This analysis gave insight into the potential influence of vessel mapping modality on decision-making.

Results

Comparison of NCE-MRA with US for the arteries and veins, demonstrated a bias of 9% (limits −33%-78%) and 38% (limits −36%-198%), respectively. Statistically significant differences between the modalities on the individual locations were mainly found for the venous locations. The sensitivity and specificity for US to predict VA location was 1.0 and 0.74, respectively, while for NCE-MRA this was 0.88 and 0.39, respectively.

Conclusions

The results obtained indicate that extreme caution should be exercised when replacing one diameter measurement modality with the other. A further need exists to improve both vessel mapping protocols to obtain a geometric description of the upper extremity vasculature regardless of acquisition modality.

The benefit of non contrast-enhanced magnetic resonance angiography for predicting vascular access surgery outcome: a computer model perspective

INTRODUCTION

Vascular access (VA) surgery, a prerequisite for hemodialysis treatment of end-stage renal-disease (ESRD) patients, is hampered by complication rates, which are frequently related to flow enhancement. To assist in VA surgery planning, a patient-specific computer model for postoperative flow enhancement was developed. The purpose of this study is to assess the benefit of non contrast-enhanced magnetic resonance angiography (NCE-MRA) data as patient-specific geometrical input for the model-based prediction of surgery outcome.

METHODS

25 ESRD patients were included in this study. All patients received a NCE-MRA examination of the upper extremity blood vessels in addition to routine ultrasound (US). Local arterial radii were assessed from NCE-MRA and converted to model input using a linear fit per artery. Venous radii were determined with US. The effect of radius measurement uncertainty on model predictions was accounted for by performing Monte-Carlo simulations. The resulting flow prediction interval of the computer model was compared with the postoperative flow obtained from US. Patients with no overlap between model-based prediction and postoperative measurement were further analyzed to determine whether an increase in geometrical detail improved computer model prediction.

RESULTS

Overlap between postoperative flows and model-based predictions was obtained for 71% of patients. Detailed inspection of non-overlapping cases revealed that the geometrical details that could be assessed from NCE-MRA explained most of the differences, and moreover, upon addition of these details in the computer model the flow predictions improved.

CONCLUSIONS

The results demonstrate clearly that NCE-MRA does provide valuable geometrical information for VA surgery planning. Therefore, it is recommended to use this modality, at least for patients at risk for local or global narrowing of the blood vessels as well as for patients for whom an US-based model prediction would not overlap with surgical choice, as the geometrical details are crucial for obtaining accurate flow predictions.

Vascular access today

The number of patients with chronic kidney disease requiring renal replacement therapy has increased worldwide. The most common replacement therapy is hemodialysis (HD). Vascular access (VA) has a key role for successful treatment. Despite the advances that have taken place in the field of the HD procedure, few things have changed with regards to VA in recent years. Arteriovenous fistula (AVF), polytetrafluoroethylene graft and the cuffed double lumen silicone catheter are the most common used for VA. In the long term, a number of complications may present and more than one VA is needed during the HD life. The most common complications for all of VA types are thrombosis, bleeding and infection, the most common cause of morbidity in these patients. It has been estimated that VA dysfunction is responsible for 20% of all hospitalizations. The annual cost of placing and looking after dialysis VA in the United States exceeds 1 billion dollars per year. A good functional access is also vital in order to deliver adequate HD therapy. It seems that the native AVF that Brescia and Cimino described in 1966 still remains the first choice for VA. The native forearm AVFs have the longest survival and require the fewest interventions. For this reason, the forearm AVF is the first choice, followed by the upper-arm AVF, the arteriovenous graft and the cuffed central venous catheter is the final choice. In conclusion, VA remains the most important issue for patients on HD and despite the technical improvements, a number of problems and complications have to be resolved.

Patient-specific computational modeling of upper extremity arteriovenous fistula creation: its feasibility to support clinical decision-making

Introduction

Inadequate flow enhancement on the one hand, and excessive flow enhancement on the other hand, remain frequent complications of arteriovenous fistula (AVF) creation, and hamper hemodialysis therapy in patients with end-stage renal disease. In an effort to reduce these, a patient-specific computational model, capable of predicting postoperative flow, has been developed. The purpose of this study was to determine the accuracy of the patient-specific model and to investigate its feasibility to support decision-making in AVF surgery.

Methods

Patient-specific pulse wave propagation models were created for 25 patients awaiting AVF creation. Model input parameters were obtained from clinical measurements and literature. For every patient, a radiocephalic AVF, a brachiocephalic AVF, and a brachiobasilic AVF configuration were simulated and analyzed for their postoperative flow. The most distal configuration with a predicted flow between 400 and 1500 ml/min was considered the preferred location for AVF surgery. The suggestion of the model was compared to the choice of an experienced vascular surgeon. Furthermore, predicted flows were compared to measured postoperative flows.

Results

Taken into account the confidence interval (25^th and 75^th percentile interval), overlap between predicted and measured postoperative flows was observed in 70% of the patients. Differentiation between upper and lower arm configuration was similar in 76% of the patients, whereas discrimination between two upper arm AVF configurations was more difficult. In 3 patients the surgeon created an upper arm AVF, while model based predictions allowed for lower arm AVF creation, thereby preserving proximal vessels. In one patient early thrombosis in a radiocephalic AVF was observed which might have been indicated by the low predicted postoperative flow.

Conclusions

Postoperative flow can be predicted relatively accurately for multiple AVF configurations by using computational modeling. This model may therefore be considered a valuable additional tool in the preoperative work-up of patients awaiting AVF creation.