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Non-contrast-enhanced MR angiography of the foot with flow spoiled-fresh blood imaging (FS-FBI): feasibility study and comparison of different scanning parameters

  • Yuyang Zhang
  • Shuai Yu
  • Dejun She
  • Dehua Chen
  • Dairong CaoEmail author
Original Article
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Abstract

Objectives

To evaluate the feasibility of foot arteries using flow-spoiled-fresh blood imaging (FS-FBI) and to investigate how the FS-FBI scanning parameters affect the flow sensitivity and impact the depiction of pedal arteries.

Methods

The study included 46 young healthy volunteers examined by FS-FBI using 1.5T MRI scanner. Additional FS-FBI examination with different flip angles (FA) of the radiofrequency refocusing pulse and echo time (TE) was performed on 36 volunteers. Two radiologists separately analyzed and graded the venous contamination, image quality, displaying rate, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) values of foot arteries. Multi-sample Friedman test and paired two-sided Student’s t test were used for statistical analysis (P < 0.05).

Results

Average image quality and venous contamination score of all arteries was good. The demonstration rate of distal anterior and posterior tibial artery, and lateral plantar artery was 100%. Dorsalis pedis artery, first dorsal metatarsal artery, medial plantar artery, and plantar arch were demonstrated at a rate above 90%. The demonstration rate of medial tarsal artery was 73.9%, whereas arcuate artery was detected with a rate of only 5.4%. Significant differences in image quality, SNR, and CNR of distal arterial area were observed between different FA and TE.

Conclusion

Non-contrast-enhanced MR angiography of foot using FS-FBI enables clear separation of veins from arteries, and yields reliable depiction of the foot arterial tree in healthy volunteers. Distal arterial branches of foot can be better depicted by appropriate adjustment of the flow-sensitivity parameters.

Keywords

Non-contrast-enhanced magnetic resonance angiography Flow spoiled-fresh blood imaging Foot arteries Flip angle of the refocusing pulse Echo time 

Introduction

The dorsalis pedis artery and the first dorsal metatarsal artery are frequently chosen as the vascular pedicle for the thumb reconstruction through free transplantation of the second toe or the great nail skin flap [1, 2]. Therefore, accurate localization of the pedal artery and its branches is extremely important, and the ability of precise pre-transplantation planning will facilitate the surgery. In addition, for diabetic patients with severe limb ischemia, studies had proven that foot arterial reconstruction is a reproducible, safe, and highly effective procedure, and is also suitable for ischemic foot salvage in patients with atherosclerosis [3, 4].

Ultrasonography is a convenient and clinical commonly used examination method for FDMA and the deep plantar artery (DPA), especially for surface course arteries. However, if the arteries lie deep, the bones of the foot may interfere the imaging confidence of the arteries on sonograms [5]. Digital subtraction angiography (DSA) and computed tomography angiography (CTA) are valuable imaging modalities that provide precise morphological information of the diseased arteries for the purposes of determining revascularization and grafting or stent patency. However, substantial numbers of diabetic patients are excluded from DSA or CTA because of concerns over the high dose of ionizing radiation, contrast material allergy, and nephrotoxicity [6, 7]. Contrast-enhanced magnetic resonance angiography (CE-MRA) is a rapid and robust technique that facilitates assessment of the pedal arteries. Unfortunately, venous contamination is still problematic in pedal arteries. Moreover, with the use of gadolinium-based contrast material in CE-MRA, nephrogenic systemic fibrosis (NSF) may occur in patients with serious renal insufficiency [8]. Therefore, the development of non-contrast-enhanced magnetic resonance MRA (NCE-MRA) techniques becomes significant for pedal arteries imaging.

Recent studies showed that the state-of-the-art FS-FBI with electrocardiography (ECG) gated three-dimensional half-Fourier fast spin echo (FSE) is a promising NCE-MRA technique in the peripheral extremities MR angiography [9, 10]. However, how the parameters influence the flow sensitivity for foot arteries using FS-FBI have not been reported, and whether optimal FA or TE were similar for foot and popliteal arteries has also not been elaborated yet. Since the flow velocities vary among different individuals and different diameters of vessels, therefore, the aim of this study is to investigate the scanning parameters, the flip angle (FA) of the radiofrequency refocusing pulses, and the echo time (TE), affect the flow sensitivity, and impact the depiction of pedal arteries using the FS-FBI sequence.

Materials and methods

Subjects

Forty-six healthy volunteers (26 men and 20 women; age range, 21–48 years; mean age, 27.5 ± 5.3 years) were recruited into the study from May to October 2016. Institutional review board approval was obtained for this prospective study and written informed consent was obtained from all participants. They had no personal history of smoking, lower extremities arterial diseases, diabetes, and arrhythmia.

Imaging protocol

MR imaging was performed using a 1.5-T MR unit (Vantage, Atlas-X, Toshiba, Japan). Subjects were placed in the supine position, the knees were positioned in 30°–60° flexion, and feet were parallel to the horizontal plane of a 12-element phased-array head coil. Foam padding was immobilized around the feet and beneath the knee to prevent movement. Magnetic compatible electrocardiographic electrodes were attached to the chest to trigger data acquisition. The image of bilateral foot was simultaneously acquired.

After the localization sequence, a coronal single-slice multiple-phase half-Fourier FSE two-dimensional “ECG-prep” scan was used to determine the optimal diastolic and systolic ECG delay times with the following parameters: repetition time (TR) = 3 RR intervals; TE = 80 ms; echo spacing = 5 ms; flip angle = 90°; matrix = 128 × 256; section thickness = 100 mm; field of view (FOV) = 37 cm × 37 cm; 128 phase encoding lines with single shot, parallel factor = 2.0; the scan time was about 30–80 s which was depending upon the heart rate. This “ECG-prep” scan was performed on all volunteers, because the triggering delay times varied on an individual basis. FBI-Navi, an automated analysis software, was used to determine appropriate diastolic and systolic trigger delay times automatically by means of a readout curve which plotted the signal intensity versus delay time. Low-intensity readings are corresponding to systole phase and high-intensity readings represent the diastole phase.

In each volunteer, flip angles (FA) of 90° and effective TE (TEeff) of 80 ms were tested. In addition, 36 volunteers (22 men and 14 women) were also examined using a group of parameters as follows: (1) FA 60° and TEeff 80 ms; (2) FA 120° and TEeff 80 ms; (3) FA 90° and TEeff 40 ms; and (4) FA 90° and TEeff 120 ms. Other parameters were same as follows: TR = 3 RR intervals; inversion time (TI) = 190 ms; echo spacing = 5 ms; matrix = 256 × 256 (interpolated to 512 × 512); section thickness = 2.5 mm; about 25–35 slices, depending on individual; bandwidth = 651 Hz/pixel, FOV = 37–39 × 37–39 cm; 2 shots per 256-phase encode lines; parallel imaging factor = 2.0; readout direction coinciding with the principal arterial flow of the foot artery (i.e., dorsalis pedis artery); and an acquisition time of 3–4 min, depending upon the heart rate. Total acquisition time was about 25–30 min. After image acquisition, the system automatically subtracted the systolic source images from the diastolic source images.

Image analysis

Diastolic and systolic source data sets and the subtracted images of feet were evaluated using the post-processing workstation (Intransense Tethys, France). Two experienced radiologists were blinded to the scanning protocol. All image data were interpreted twice, once by the two observers independently and then by consensus of the two reviewers. The image quality of the angiograms was assessed by a four-point scale: score 1, poor diagnostic arterial display with inadequate vessel enhancement or severe artifacts of soft tissue and venous; score 2, fair diagnostic arterial display and delineation of the arterial structures with medium artifacts of soft tissue or venous contamination; score 3, good diagnostic arterial display with good delineation of the vessel structures and minor artifacts of soft tissue or venous contamination; and score 4, excellent diagnostic arterial display with sharp delineation of the arterial vasculature and without artifacts of soft tissue or venous contamination. In addition, venous contamination was assessed on a four-point scale: score 1, severe venous contamination (signal intensity of venous is higher than or equal to of the adjacent arterial, rendering one or more vessel segments not interpretable); score 2, moderate venous contamination (signal intensity of venous is equal to of the adjacent arterial, but not disturbing interpretation); score 3, minor venous contamination (signal intensity of venous is lower than the adjacent arterial, not disturbing interpretation); and score 4, no venous enhancement. The pedal arterial segments including distal anterior tibial artery (distal ATA), dorsalis pedis artery (DA), medial tarsal artery (MTA), lateral tarsal artery (LTA), arcuate artery (AA), deep perforating artery (DPA), distal posterior tibial artery (distal PTA), lateral plantar artery (LPA), medial plantar artery (MPA), pedal arch (PA), and first–fifth dorsal metatarsal arteries (1st–5th DMA) were assessed. We defined the foot arteries into two parts: the proximal vessel area (including ATA, DA, MTA, LTA, AA, PTA, LPA, MPA, DPA, and PA) and the distal vessel area (including 1st–5th DMA) (shown in Fig. 1). For quantitative assessment, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) values of dorsal artery (DA) and first dorsal metatarsal artery (FDMA) were calculated in the subtracted images. Following equations: SNR = SIart/SDair and CNR = (SIart − SImusc)/SDair were used, where SIart is the signal intensity of artery, SImusc is the signal intensity of muscle, and SDair is the standard deviation of a circular region of interest (10 mm2 area) in the extracorporeal air.
Fig. 1

Illustration of pedal artery anatomy (a, b, d) and MIP images of FS-FBI (c, e). a, b, d Front view. c, e Lateral view. 1, distal posterior tibial artery (distal PTA); 2, distal anterior tibial artery (distal ATA); 3, medial plantar artery (MPA); 4, lateral tarsal artery (LTA); 5, lateral plantar artery (LPA); 6, dorsal artery of foot (DA); 7, deep perforating artery (DPA); 8, pedal arch (PA) artery; 9, first dorsal metatarsal artery (1st DMA); 10, 2nd–5th dorsal metatarsal artery (2nd–5th DMAs)

Statistical analysis

The image quality of ipsilateral pedal arterial branch was analyzed among all the 46 volunteers. Multi-sample Friedman test was performed to evaluate the image-quality differentiation between distal and proximal vessel area under different FA and TE in 36 volunteers. Objective image analysis for different FA and TE in DA and 1st DMA was based on a paired, two-sided Student’s t test. A statistical software package (SPSS 21.0, Chicago, IL) was used for all statistical analyses in the study. Results were declared significant at a P value of less than 0.05.

Results

FS-FBI MR angiography was well tolerated, with successful completion in all cases. Image acquisition in knee-flexion position was comfortable for all volunteers.

Overall image quality and venous contamination

The image quality and displaying rate of foot arterial branches from 46 healthy volunteers are summarized in Table 1. The distal ATA, distal PTA, and LPA segments were visualized in all the feet with excellent image quality. In all the 92 feet, 90 DA, 90 1st DMA, 85 DPA, 91 MPA, 89 PA, and 83 2nd–5th DMA segments were also visualized with perfect or diagnostic image quality. 83 LTA and 68 MTA of 92 feet were visualized with fair diagnostic image quality (2.63 ± 0.85, 2.62 ± 0.72) (Fig. 2). For the AA, only 5.4% (5/92) feet were shown with fair diagnostic image quality. For the venous contamination, average score was 3.5 ± 0.65 with score 1 for none feet of any subjects, score 2 (6.52%) for six feet, score 3 for 20 feet (21.74%), and score 4 for 66 feet (71.74%),as shown in Table 2. In our study, DA was absent or obviously small in two feet, respectively (2.17%), with a compensated enlargement of plantar posterior circulation (especially the LPA) and the 1st DMA originated directly from the PA. Definite view of the AA was demonstrated in only five feet (5.43%). Of the remaining 87 feet, 2nd–5th DMA originated directly from the PA or the LTA in 35 feet (40.23%). PA was absent in three feet.
Table 1

Image quality and displaying rate of foot artery branches

Artery

Image quality

Displaying rate

Distal anterior tibial artery (ATA)

3.80 ± 0.40

100% (92/92)

Dorsalis pedis artery (DA)

3.74 ± 0.69

97.8% (90/92)

Medial tarsal arteries MTA

2.62 ± 0.72

73.9% (68/92)

Lateral tarsal arteries (LTA)

2.63 ± 0.85

90.2% (83/92)

Arcuate artery (AA)

2

5.4% (5/92)

First dorsal metatarsal artery (1st DMA)

3.64 ± 0.66

97.8% (90/92)

Deep perforating artery (DPA)

3.37 ± 1.09

92.3% (85/92)

Distal posterior tibial artery (PTA)

3.95 ± 0.23

100% (92/92)

Medial plantar artery (MPA)

3.07 ± 0.81

98.9% (91/92)

Lateral plantar artery (LPA)

3.77 ± 0.50

100% (92/92)

Pedal arch (PA)

3.48 ± 0.78

96.7% (89/92)

2nd–5th DMAs

3.52 ± 0.60

90.2% (83/92)

Fig. 2

Dorsal artery in figure a (thick arrow) showed excellent diagnostic arterial display with sharp delineation of the arterial vasculature and without artifacts of soft tissue or venous contamination, which scored four. The dorsal metatarsal arteries in figure a (thin arrow) scored three, because good diagnostic arterial displays with good delineation of the vessel structures and minor artifacts of venous contamination. Most of pedal arteries in figure b scored two and appeared fair diagnostic arterial display and delineation of the arterial structures with medium artifacts of soft tissue and venous contamination; except for pedal arch artery (arrowhead)

Table 2

Venous contamination of foot vessels

Score

Venous contamination

Displaying rate

1

Severe

0% (0/92)

2

Moderate

6.52% (6/92)

3

Minor

21.74% (20/92)

4

No venous enhancement

71.74% (66/92)

Comparison of different FA of the refocusing pulses

When TE = 80 ms, different FA (60°, 90°, 120°) of the refocusing pulses were analyzed in 72 feet of 36 volunteers. In all subjects, the FA strongly affected the depiction of the distal arteries. As summarized in Tables 3 and 4, there was no statistically significant difference in the image quality between different FA in the proximal vessel area (P > 0.05). However, in the distal vessel area, the differences of image quality between different FA reached statistical significance (P < 0.05). As also shown in Fig. 3, proximal vessel areas were equally well depicted among different FA, whereas distal vessel area exhibited higher signal contrast and less signal loss in lower FA compared to higher FA without obvious soft tissue or venous contamination.
Table 3

Image quality comparison of different flip angles of refocusing pulses

 

Proximal vessel area

Distal vessel area

FA60

FA90

FA120

P

FA60

FA90

FA120

P

Mean ± SD

3.49 ± 0.53

3.56 ± 0.53

3.61 ± 0.52

> 0.05

3.38 ± 0.49

3.06 ± 0.44

2.79 ± 0.69

< 0.01

Median

3.5

4

4

 

3

3

3

 

Q1; Q3

3; 4

3; 4

3; 4

 

3; 4

3; 3

2; 3

 

Q1 first quartile, Q3 third quartile

Table 4

Image quality comparison of each different flip angles of refocusing pulses

 

Proximal vessel area (P value)

Distal vessel area (P value)

FA60:FA90

0.505

0.037

FA60:FA120

0.067

< 0.01

FA90:FA120

0.157

0.010

Fig. 3

FS-FBI MIP images of the foot in a 26-year-old healthy female volunteer (average heart rate of 70 beats per minute) were shown for flip angle of refocusing pulses of 60°, 90°, and 120°. TE = 80 ms in all cases. The next line (A2, B2, C2) is partial amplification of the previous line (A1, B1, C1). Note that the image quality of proximal vessel area was equivalent with scoring of four. However, in the distal vessel area, the small branch arteries were better visualized at low flip angle

Comparison of different TE

When FA = 90°, different TE (40 ms, 80 ms, 120 ms) were compared. A longer echo time may have a same feature. There was no statistical significance for image quality between different TE in the proximal vessel area (Table 5; P > 0.05), but was significant in the distal vessel area (Table 6; P < 0.05). The proximal vessel area was clearly depicted at different TE, while the distal vessel area was better visualized at the longer TE (120 ms), as shown in Fig. 4.
Table 5

Image quality comparison of different echo times

 

Proximal vessel area

Distal vessel area

TE40

TE80

TE120

P

TE40

TE80

TE120

P

Mean ± SD

3.61 ± 0.49

3.53 ± 0.53

3.49 ± 0.53

> 0.05

2.36 ± 0.88

2.79 ± 0.44

3.18 ± 0.72

< 0.01

Median

4

4

3.5

 

2

3

3

 

Q1; Q3

3; 4

3; 4

3; 4

 

2; 3

3; 3

3; 4

 

Q1 first quartile, Q3 third quartile

Table 6

Image quality comparison of each echo time

 

Proximal vessel area (P value)

Distal vessel area (P value)

TE40:TE80

0.121

0.02

TE40:TE120

0.081

< 0.01

TE80:TE120

0.315

0.014

Fig. 4

MIP images of feet were shown for TE of 40 ms, 80 ms, and 120 ms in a 29-year-old healthy volunteer, with average heart rate of 64 beats per minute. FA = 90° in all cases. The next line (A2, B2, C2) is partial amplification of the previous line (A1, B1, C1). The depiction of proximal vessel area was equivalent with excellent image quality. The small arteries, especially the plantar metatarsal digital arteries, were better visualized at high echo time with clearer visualization of peripheral branches

Quantitative assessment among different FA and TE

For the quantitative measurements, the SNR and CNR were significantly higher in 1st DMA using lower FA or higher TE (both SNR and CNR: P < 0.05). However, there were no significant differences in SNR and CNR of DA among the images acquired with different FA and TE (P values all > 0.05). The details of the SNR and CNR for DA and 1st DMA are shown in Fig. 5.
Fig. 5

Mean signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) values of different flip angle (FA) and echo time (TE) in all 36 volunteers. a, b Bar graph shows the comparison of mean SNR ± SD and CNR ± SD between different FA. c, d Bar graph shows the comparison of mean SNR ± SD and CNR ± SD between different TE. DA dorsalis pedis artery, 1st DMA first dorsal metatarsal artery

Discussion

This study demonstrated that the FS-FBI achieved high diagnostic depiction of foot arteries in health volunteers, and flow sensitivity depended on the appropriate FA and TE in 1.5T MRI scanner.

According to a different mechanism, NCE-MRA can be categorized into three groups: inflow-based (time of flight, TOF; quiescent interval single shot, QISS), cardiac-phase dependent (flow-spoiled-fresh blood imaging, FS-FBI), and flow-encoded (flow-sensitive dephasing, FSD) for the displaying of peripheral arteries. The TOF is mostly widely used, but it is sensitive to patient motion, easy to cause systematic overestimation of the grade of the stenosis and prone to artifacts from in-plane flow [11, 12]. Therefore, it is rarely used in pedal arteries. The QISS is composed of a slice-selective pulse which suppressing the stationary tissue signal, a traveling pulse suppressing the venous signal, and a 2D steady-state-free precession (SSFP) with chemical shift-selective fat saturation pulse. However, the technique is limited in resolution in the slice direction [13]. Therefore, it may not be suited for imaging tortuous and small arteries with substantially slow flow. Compared to FS-FBI, the FSD technique relies on segmented SSFP and flow dependency of cardiac phase, which enables excellent contrast between arteries and surrounding veins and tissues. Storey had described the feasibility and flow-sensitivity tailoring of peripheral arteries using the FSD, but except for the pedal arteries evaluation and lack of objective measurements [14]. Because diffusion preparation module decided flow sensitivity singly depends on peak systolic velocities rather than the late-phase diastolic velocities, FSD has been demonstrated to be less sensitive to velocities in late-phase diastole. As a result, insufficient subtraction from systolic–diastolic phase may be lead to inferior image quality [15]. Schubert et al. demonstrated that if technically successful, the diagnostic performance of cardiac-phase-dependent NCE-MRA is comparable to the CE-MRA even in distal pedal arteries [16].

In our study, most of the foot arterial segments, especially the two main foot arteries (the dorsalis pedis artery and lateral plantar artery), had good or excellent diagnostic image quality. Compared to few studies using other methods of foot angiography, our study showed that the displaying rate of the dorsalis pedis artery was 97.8% with average image quality over three points, which is similar to what had been reported in those previous studies [17, 18]. Pedal arch, an important anastomosis between the dorsalis pedis artery and lateral plantar artery, was displayed in 89 out of 92 with the images scored as good. The distal artery branches, such as the first dorsal metatarsal artery and plantar metatarsal digital arteries, also received excellent conspicuity scores in most of the feet (97.8% and 90.2%, respectively). Anatomic variation of foot artery could be divided into several patterns, especially for the dorsalis pedis artery and metatarsal artery [19]. In our study, dorsalis pedis artery was obviously small or absent in two feet, respectively, with untouchable artery impulse in the physical examination. However, plantar circulation was compensatively enlarged, especially the lateral plantar arteries, and the dorsal metatarsal artery for hallux and plantar metatarsal digital arteries originated directly from or shared with a common trunk of the pedal arch in these cases. At the level of tarsometatarsal joint, arcuate artery originates from the dorsalis pedis artery, then tending laterally across the bases of 2nd–5th metatarsals. Second–fifth DMA are the branching off arcuate artery. Studies suggest that the dorsal metatarsal arteries are not primarily supplying from the arcuate artery, with the presenting rate ranging from 16.7 to 25% [20, 21]. In our study, arcuate artery was displayed in 5.4% of 92 feet, which was lower than the previous studies. Possible reasons may be the anatomy variation and weak signal intensity within the caliber. When reviewing the source images of the systolic and diastolic phase, five of 87 arcuate arteries were mildly developing in both phases, resulting in the signal loss in substraction images. It may underestimate the displaying rate to some extent. Plantar arch was an important anastomosis between the dorsalis pedis artery and lateral plantar artery, and almost well developed and complete. Eighty-nine of 92 plantar arches were displayed with average image quality of 3.48 ± 0.78 in our study. When the plantar arch was absent, the blood supply of forefoot was originated from the dorsal circulation.

Subjective and quantitative assessment reveals that FS-FBI provides significant improvements in both SNR and CNR values for the distal arteries area using lower FA or longer TE. Parameters that influence the flow sensitivity must be adjusted to obtain preferable visualization of vessels with different calibers. The signal intensity within the fast flowing artery is reduced due to flow void effects in FSE T2WI images. Venous flow is relatively slow and non-pulsation, which always generates high signals in both diastole and systole gated images. Thus, arterial and venous flow velocities can be differentiated in the systolic and diastolic phases of the cardiac cycle [22]. The major impact factors of the flow sensitivity of FSE sequences include the flip angle of the RF refocusing pulses and the echo time. The flip angle relates to the spin-echo contribution and echoes stimulation, and the echo time affects the motional dephasing. Our results showed that the distal branches of foot arteries were better depicted with more sensitively flow property. This can be explained as below. Intravoxel dephasing from isochromats with variable velocities, and mixing among pathways involving different combinations of spin echoes and stimulated echoes affect the signal loss from moving protons arises in fast spin-echo images. Flip angle less than 180° is generally used to reduce specific absorption rate and to delay the signal decay of stationary tissues. As a result of repeated magnetization exchanging in the transverse plane and the longitudinal axis, pathways that combine spin echoes and stimulated echoes demonstrate a complex phase evolution. When these pathways mingle during the echo emergence, the disparity of motion-induced phases can motivate signal loss. As the flip angle of the refocusing pulses correlates to spin echoes and stimulated echoes contributions, it mightily affects the flow-sensitive property of the sequence [23, 24, 25]. The small lumen arteries are superior depicted at lower flip angle, indicating that the max velocity of small lumen arteries is adequate to induce dephasing at small flip angles. Because a great quantity of pathways that conduce to later echoes can cause superior motional dephasing, the flow sensitivity of the sequence is supposed to increase with the echo time at low flip angles [14]. Thus, distal vessel area was better visualized at the smaller FA and longer TE, thereby provided adequate depiction small arteries in the pedal without influence of proximal arteries. FA of 90° and TE of 80 ms were chosen as the middle values in this study, because these parameters were routine protocol used at peripheral arteries stations in the previous reports. Based on our results, in the further research for smaller pedal arteries in patients, appropriated FS-FBI scanning parameters can be explored at the range FA lower than 90° or TE longer than 80 ms.

Our results are preliminary, but illustrate the promising nature of this unenhanced MR angiography method for imaging foot vessels. There were several limitations to this study. The main limitation of our work was lack of an imaging standard for comparison. Second, only healthy subjects were examined. Third, a wider range of parameters has not been explored in this study. However, by investigating whether and how the FA and TE influence the flow sensitivity for pedal arteries in healthy volunteers, small ranges of FA and TE can be time saving and more precision in a further patients study with comparison by standard imaging strategies.

In conclusion, non-contrast-enhanced MR angiography of foot using FS-FBI enables clear separation of veins from arteries, and yields reliable depiction of the foot arterial tree in healthy volunteers. Distal arterial branches of foot can be better depicted by appropriate adjustment of the flow-sensitivity parameters.

Notes

Acknowledgements

This project supported by the Foundation for Young Scholars of Fujian Provincial Health Commission, China (Grant No. 2017-1-49).

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Copyright information

© Springer Nature Singapore Pte Ltd. 2019

Authors and Affiliations

  • Yuyang Zhang
    • 1
  • Shuai Yu
    • 1
  • Dejun She
    • 1
  • Dehua Chen
    • 1
  • Dairong Cao
    • 1
    Email author
  1. 1.Department of RadiologyFirst Affiliated Hospital of Fujian Medical UniversityFuzhouPeople’s Republic of China

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