To Assess the Value of 3D Time-of-Flight Magnetic Resonance Angiography in Hemodialysis Patients With Occlusive Disease in Arteriovenous Fistula
Phase: NA
Conditions: Magnetic Resonance Angiography, Hemodialysis, Arteriovenous Fistula Stenosis
Sponsor: Shanghai Jiao Tong University Affiliated Sixth People's Hospital

3D Time-of-Flight Magnetic Resonance Angiography in Hemodialysis Patients With 
Arteriovenous Fistula 
Clinical trial No: NCT04312731 
Date:2022-1-4 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Study Design and Patient Population 
From June 2018 to March 2021, maintenance dialysis patients in the nephrology 
department at our hospital with suspected dysfunctional AVFs were considered 
candidates for this study. The inclusion criteria of the dysfunctional hemodialysis 
access patients were as follows. 1) Physical examination showed swelling of the 
extremities, a reduction of pulsation and a tremor at the anastomotic site, and reduction 
of the murmur. 2) The venous pressure and arterial negative pressure were increased, 
and the blood flow of the fistula was decreased (< 500 mL/min). 3) The hemodialysis 
site was difficult to puncture during dialysis; the cannulation coagulated easily; and the 
bleeding time was prolonged after needle extraction. The exclusion criteria were as 
follows: 1) a previous history of stent or artificial blood vessel implantation; 2) 
contraindications to magnetic resonance; 3) a platelet (PLT) level < 60 × 109/L or an 
international normalized ratio (INR) > 1.5; 4), pregnancy or lactation; and 5) a 
functional failure of other important organs or other serious diseases except for renal 
failure (Clinical trial No. NCT04312731). A detailed flowchart of the patient selection 
process is provided in Figure 1. 
Imaging protocol 
Color Doppler ultrasonography: Ultrasonography studies were independently 
performed in the Department of Ultrasonography by two sonographers (L.X.Y. and 
Y.J.X. with 12 and 8 years of experience, respectively). The entire hemodialysis access 
fistula was evaluated by means of 5- and 7-mHz linear array scanners (Aspen Advanced; 
Siemens, Erlangen, Germany), from the feeding artery from the level of the axillary 

artery and draining vein to the level of the subclavian vein. The examinations were 
performed in both longitudinal and transverse planes. Spectral waveforms were 
obtained at each examination level, and color Doppler interrogation was used 
throughout the studies. Peak systolic velocity (PSV) and the location of any narrowed 
areas were calculated and recorded. The PSV criteria were the same for the inflow, 
shunt proper (e.g., anastomotic sites), and outflow tract. All measurements were 
obtained from waveforms with an insonating angle of less than 60° when possible. The 
stenosis was considered significant if the PSV was greater than 375 cm/s or if there was 
narrowing of 50% or more on the grayscale imaging. All data were recorded on a form 
on which the localizations of the stenoses were drawn. 
Magnetic resonance angiography: MRIs were undertaken on a 3-T system (Skyra, 
Siemens Healthcare, Erlangen, Germany) using a superficial body array matrix coil. 
The imaging was performed with the patient lying supine, with the target arm 
containing the fistula as close to the midline of the examination bed as possible. A TOF-
MRA acquisition, covering a transverse slab from the elbow joint to 5 cm below the 
anastomosis, had acquisition parameters of a 23 ms/3.5 ms repetition time/echo time; a 
70
°flip angle; a 200*200 *200 mm3 volume of interest; a 2 mm section thickness; a 
1024*1024 acquisition matrix; 180 slices and an appropriately 5 minutes scan duration. 
Based on the TOF images, two radiologists, with extensive experience in AVF diagnosis, 
preliminarily determined the position of the stenosis. Finally, through an automatic 
subtraction method, maximum-intensity projection (MIP) images of each of the four 
stations were reconstructed in the coronal orientation and were fused to form a single 

image using MR MobiView software (Philips Medical Systems). 
The DSAs were carried out by interventional radiologists (Y.Q.Z. and H.T.L., who 
have 17 and 15 years of experience in vascular imaging, respectively) on the digital 
angiography unit (Artis zee; Siemens Medical Solutions), within a mean of 10 (range: 
1-14) days after the ultrasonography and MRA. An access approach on the brachial 
artery was used. An iodine-based contrast agent (Imeron 350; Bracco Imaging, 
Shanghai, China) was injected through a 5-French catheter positioned in the feeding 
artery. The anteroposterior views were chosen at the discretion of the interventional 
radiologist. Images of the feeding artery, fistula and distal venous outflow were 
obtained. After the angiogram, percutaneous transluminal angioplasty (PTA) was 
performed for the areas that had >50% stenoses or that had a total occlusion. 
Image analysis 
Two radiologists (L.M.W. and Y.Q.Z. with 10 and 15 years of experience in evaluating 
vascular images, respectively) independently evaluated the MRA and DSA images 
while blinded to the patient’s identity, medical history, and symptoms. In case of 
disagreement, consensus was reached after mutual consultation. The MRA datasets 
were evaluated on dedicated workstations (Syngo® MR B17, Siemens), and the DSA 
images were also analyzed on a workstation (SyngoXWP; Siemens Healthcare). 
The image quality and diagnostic performance of TOF-MRA were evaluated in all 
regions. For all participants, the architecture of the AVF was divided into three regions: 
arterial inflow, anastomosis (including 1 cm of vessel length on both sides of the 
anastomosis), and venous outflow. The most central part of the venous outflow, 

comprising the proximal half of the brachiocephalic vein and superior caval vein, was 
excluded from the analysis because these venous structures were not depicted by the 
TOF-MRA in this study. 
The diagnostic quality of the images obtained at each of the three regions was graded 
(0-4) using the Likert scale: 0 for a “nondiagnostic” image; 1 for a “poor” quality, with 
the observer not confident due to severe image artifacts, significant venous 
contamination and/or poor vascular signals; 2 for a “fair” quality, with the observer 
marginally confident due to minor artifacts, mild-to-moderate venous contamination 
and/or a moderately homogenous vascular signal; 3 for a “good” quality, with the 
observer being confident; or 4 for an “excellent” quality, with no or minimal venous 
contamination, without artifacts and homogenous vascular signals, thereby enabling the 
observer to be highly confident. 
The grading of lesion stenosis on CDUS, MRA, and DSA was performed by using an 
electronic caliper. The sonographer or radiologist determined whether stenosis or 
occlusion was present in all regions (Figure 2-4). The degree of stenosis was assessed 
according to a visual grading system: 0 = a completely smooth vessel wall; 1 = < 50% 
stenosis; 2 = 50–75% stenosis; 3 = 75–99% stenosis; 4 = occlusion (segmental and 
complete). For analysis purposes, only the most severe stenosis per region was 
evaluated. Stenoses with a luminal narrowing exceeding 50% were considered to be 
hemodynamically significant. The stenosis severity of TOF-MRA and CDUS was 
considered overestimated if the score of stenosis was higher than that found on DSA; 
otherwise, it was considered underestimated. 

Statistical analysis 
The Likert scores for the diagnostic image quality are reported as the mean ± standard 
deviation and were compared using the paired t test. DSA was considered to be the 
standard of reference. The whole-region and per-region sensitivities, specificities, 
positive predictive values (PPVs) and negative predictive values (NPVs) for the 
detection of significant (50–100%) stenosis are shown as proportions, with 
corresponding 95% confidence intervals (CIs) and were provided for each estimate. 
The interobserver agreement with regard to the determination of significant stenosis 
was evaluated by calculating the k statistic. Cohen’s kappa coefficient (κ) was 
calculated, with κ >0.80 regarded as “almost perfect”, between 0.61 and 0.80 regarded 
as “substantial”, and between 0.41 and 0.60 regarded as “moderate”. P < 0.05 (two-
sided) were regarded significant. The statistical analyses were undertaken using SPSS 
v19.0 (IBM, Armonk, NY, USA).