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Volume 18 Supplement 1

19th Annual SCMR Scientific Sessions

  • Poster presentation
  • Open Access

Prospective Heart Tracking for Respiratory Motion Compensation in Whole-heart Magnetic Resonance Angiography

  • 1, 2,
  • 1, 2 and
  • 1, 2
Journal of Cardiovascular Magnetic Resonance201618 (Suppl 1) :P12

https://doi.org/10.1186/1532-429X-18-S1-P12

  • Published:

Keywords

  • Magnetic Resonance Angiography
  • Inversion Recovery Pulse
  • Gadofosveset Trisodium
  • Compromise Image Quality
  • Respiratory Navigator

Background

Electrocardiogram and respiratory navigator (NAV)-gated 3D whole-heart magnetic resonance angiography (MRA) acquired with an intravascular gadolinium-based contrast agent and a non-selective inversion recovery (IR) pulse to null the myocardial signal generates a high-resolution anatomic dataset allowing for a comprehensive evaluation of intra-cardiac, coronary, and vascular abnormalities [1]. In this technique, an additional IR pulse is also included to selectively restore the signal in the liver, and thus allow NAV tracking of the diaphragm (liver-lung interface). This selective IR pulse, however, excites the blood flowing from veins into the heart creating a bright inflow artifact that hinders image interpretation [2]. Therefore, we sought to develop a prospective respiratory-gating technique (Heart-NAV) that tracks the heart rather than the diaphragm position and eliminates the inflow artifact without compromising image quality.

Methods

Schematics of the proposed Heart-NAV technique for non-contrast and contrast-enhanced MRA sequences are shown in Fig. 1A&1B. One of the startup pulses for MRA sequence is used to collect the centerline of k-space, and its 1-dimensional reconstruction is fed into the conventional-NAV signal analysis process to prospectively gate and track respiratory-induced heart displacement. To assess the efficacy of Heart-NAV in the correction of respiratory motion, 10 volunteers (7 females; age 31 ± 6 years) underwent MRA acquisitions with conventional-NAV and Heart-NAV. For both acquisitions, imaging parameters were FOV ~386 × 230 × 120 mm3, spatial resolution 1.5 mm3; α/TE/TR 90°/2.4/4.7 ms, bandwidth 0.54 kHz, SENSE factor of 2, acceptance window of 5 mm, and a 32-element phased-array coil. To compare their image quality, sharpness of the coronary arteries was subjectively graded by 2 clinicians and objectively measured (Soap Bubble tool). Subjective and objective measures were compared using a signed-rank test and paired student t-test, respectively. To evaluate the effect on image inflow artifact, 6 patients (4 males; ages 0.3-6 years) each underwent contrast-enhanced (0.03 mmol/kg of gadofosveset trisodium) IR MRA acquisitions with a conventional-NAV and with Heart-NAV.
Figure 1
Figure 1

(A) Schematic diagram of the proposed non-contrast whole-heart MRA acquisition with Heart-NAV. (B) Schematic diagram of the proposed contrast-enhanced whole-heart MRA with Heart-NAV. (C) Images of non-contrast whole-heart MRA acquisitions with a conventional-NAV and with Heart-NAV from 2 healthy volunteers. (D) Coronal images of contrast-enhanced whole-heart MRA acquisitions with a conventional-NAV and Heart-NAV from 2 patients. Fat sup, fat suppression pulse; FOS, fold-over suppression pulse; IR pulse, inversion recovery pulse; SP, startup pulses; SSFP, steady-state free precession pulse; T2-prep, T2-preparation pulse; TR, repetition time.

Results

All acquisitions were successfully completed. Images from 2 healthy subjects with the non-contrast MRA sequences are shown in Fig. 1C. The vessel sharpness and image quality were equivalent for conventional-NAV and Heart-NAV acquisitions but the imaging time of Heart-NAV was 10% shorter (Table 1). Fig. 1D displays images with contrast-enhanced MRA acquisitions from 2 patients. Inflow artifact was present with the conventional-NAV but not with Heart-NAV.
Table 1

Comparison of conventional-NAV and Heart-NAV for non-contrast whole-heart MRA (n = 10).

 

Conventional-NAV

Heart-NAV

p-value

Scan time (min)

8.4 ± 2.2

7.5 ± 1.7

<0.01

RCA subjective sharpness

3.67 ± 0.49

3.77 ± 0.37

0.42

RCA objective sharpness

0.64 ± 0.04

0.67 ± 0.04

0.18

LAD subjective sharpness

3.55 ± 0.51

3.53 ± 0.46

0.91

LAD objective sharpness

0.61 ± 0.07

0.60 ± 0.07

0.62

LCX subjective sharpness

3.47 ± 0.55

3.43 ± 0.53

0.83

LCX objective sharpness

0.56 ± 0.07

0.56 ± 0.09

0.85

Values are mean ± standard deviation. Subjective sharpness: 1-poor to 4-excellent. Objective sharpness: 0-blurred to 1-sharp. LAD, left anterior descending coronary artery; LCX, left circumflex coronary artery; RCA, right coronary artery.

Conclusions

Compared to a conventional-NAV, Heart-NAV achieved similar image quality for non-contrast whole-heart MRA, and eliminated inflow artifact in contrast-enhanced whole-heart MRA.

Authors’ Affiliations

(1)
Cardiology, Boston Children's Hospital, Boston, MA, USA
(2)
Pediatrics, Harvard Medical School, Boston, MA, USA

References

  1. Makowski MR, et al: Radiology. 2011, 260 (3):Google Scholar
  2. Peters DC, et al: Radiology. 2007, 243 (3): 690-695.View ArticlePubMedGoogle Scholar

Copyright

© Moghari et al. 2016

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

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