Compressed sensing and parallel imaging accelerated T2 FSE sequence for head and neck MR imaging: Comparison of its utility in routine clinical practice

https://doi.org/10.1016/j.ejrad.2020.109501Get rights and content

Highlights

  • Compressed sensing (CS) is a new method for head and neck MR image acquisition.

  • Parallel imaging (PI) with CS can reduce examination time as compared with PI.

  • The new sequence performed slightly better than the old sequence at reduced scan time.

Abstract

Purpose

To directly compare the capability of compressed sensing (CS) and parallel imaging (PI) accelerated T2 FSE (Fast Spin Echo) sequence with PI for head and neck MR imaging.

Methods

Thirty consecutive patients with various head and neck diseases (15 men and 15 women, mean age 53 ± 22 years) underwent MR imaging by PI with CS and by PI. Reduction factors were as follows: PI with CS, 3 and PI, 1.5. Examination times for PI with CS and PI were all recorded. For quantitative image quality assessment, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. For qualitative assessment, two investigators assessed overall image quality, artifacts and diagnostic confidence level using a 5-point scoring system, and final scores were determined by consensus of two readers. Mean examination time and all indexes were compared by means of paired t-test and Wilcoxon signed-rank test. Inter-observer agreement for each qualitative index was assessed in terms of kappa statistics.

Results

Mean examination time for PI with CS (83.5 ± 11.0 s) was significantly shorter than that for PI (173.0 ± 54.4 s, p < 0.0001). SNR and CNR of PI with CS were significantly better than those with PI (mean SNR; 11.2 ± 3.6 vs 8.9 ± 2.6, median of CNR; 7.4 vs. 6.1, p < 0.0001). All inter-observer agreements were assessed as significant and substantial (0.62 < κ < 0.81).

Conclusion

PI with CS accelerated T2 weighted sequence performs equally well or even slightly better than its PI accelerated, conventional counterpart at reduced scan times in the context of head and neck MR imaging.

Introduction

Head and neck cancers comprise a wide range of histological types since they arise from different tissues in this complex region. Magnetic resonance (MR) imaging is more useful than other imaging techniques for anatomical assessment of these head and neck cancers, especially for mapping the primary tumor’s extent and identifying scar tissue post treatment. This anatomical information is complementary to computed tomography (CT) and 2-[18 F]-fluoro-2-deoxy-D-glucose (FDG) positron-emission tomography (PET) for oncological imaging of the head and neck. Moreover, MR imaging is a versatile technique that has the advantage of providing not only anatomical information but also molecular, metabolic, and physiological information. Therefore, head and neck MR imaging has been frequently used for various clinical purposes in routine clinical practice, although the resultant increase in examination time is considered one of the drawbacks [1,2]. For routine clinical practice, therefore, reducing examination time for certain sequences, especially MR imaging for obtaining anatomical information, might be essential.

Since the beginning of the 2000s, improving temporal and spatial resolution for MR imaging have been tested, not only by using image domain-based parallel imaging (PI) techniques, but also the k-space domain-based parallel imaging technique for 1.5 and 3 Tesla(T) MR systems [3]. However, it has been suggested that the advantages of a reduction in examination time and improvements in temporal and spatial resolution by using PI are limited due to the increase in the number of coil elements. Compressed sensing (CS) has recently been introduced as a new method for reducing the number of k-space samples by exploiting compressibility or sparsity in an appropriate transform domain [4]. However, it has been found that one of the drawbacks of simply reducing k-space sampling for CS may be relatively lower signal-to-noise ratio (SNR) than PI. This situation led to the recent development of new CS methods by a few MR vendors. These methods were combined PI with CS and clinically tested for body MR imaging in various organs. In routine clinical practice, T2 weighted image is one of key sequences for head and neck MR imaging in clinical practice because it shows good contrast of multiple fine structures in head and neck. Although a few investigators had tested the utility of CS accelerated T2 weighted sequences in the internal auditory canal and brain [5,6], no major studies have been reported for assessing the utility of PI with CS for T2 weighted image of head and neck MR imaging.

We hypothesized that a newly developed PI with CS could improve the image quality and shorten examination time for head and neck MR imaging as compared with PI. The purpose of this study was to directly compare the capability of compressed sensing (CS) and parallel imaging (PI) accelerated T2 FSE (Fast Spin Echo) sequence with PI for head and neck MR imaging.

Section snippets

Protocol, support, and funding

This retrospective study was approved by the Institutional Review Board of Fujita Health University School of Medicine, and technically and financially supported by Canon Medical Systems Corporation. Written informed consents was provided to all subjects in this study. One of the authors is an employee of Canon Medical Systems (K.Y) but did not have control over any of the data used in this study.

Subjects

During June and August 2019, 30 consecutive patients with various head and neck diseases (15 men

Results

Representative cases are shown in Fig. 3, Fig. 4. Mean examination time for PI with CS (83.5 ± 11.0 s) was significantly shorter than that for PI (173.0 ± 54.4 s, p < 0.0001).

A comparison of quantitatively assessed image quality is shown in Fig. 5. Quantitative image indexes, SNR and CNR of PI with CS (SNR: mean ± standard deviation, 11.2 ± 3.6, CNR: median, 7.4 [interquartile range, 5.5–9.4]) were significantly better than those of PI (SNR: 8.9 ± 2.6, p < 0.0001; CNR: 6.1 [4.5–7.5],

Discussion

Our results demonstrate that PI with CS has the capability to reduce examination time while improving quantitative image quality indexes as compared with PI with CS and PI for head and neck MR examinations using a 3 T MR system. In addition, qualitative image quality indexes and diagnostic confidence level showed no significant differences between PI with CS and PI in this setting. Although a few investigators evaluated the utility of CS for T2-weighted imaging in different anatomical regions [5

CRediT authorship contribution statement

Hirotaka Ikeda: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Resources, Visualization, Writing - original draft, Writing - review & editing. Yoshiharu Ohno: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Visualization, Writing - original draft, Writing - review & editing. Kazuhiro Murayama: Data curation, Methodology, Project administration,

Declaration of Competing Interest

This study was technically and financially supported by Canon Medical Systems Corporation, Japan. Among the authors, Drs. Ohno, Murayama and Toyama got research grants from Canon Medical Systems Corporation, Japan. Ms. Yamamoto is an employee of Canon Medical System Corporation, but did not have control over any of the data and information submitted for publication or which data and information were to be included in this study. Mr. Iwase, Mr. Fukuba and I (i.e. Dr. Ikeda) have nothing to

Acknowledgements

The authors wish to thank Daiki Tabata, RT and Saki Takeda, RT (Department of Radiology, Fujita Health University Hospital), Yuichiro Sano, RT and Masato Ikedo, MEng (Canon Medical Systems Corporation) for their outstanding contributions to this work. This study was financially and technically supported by Canon Medical Systems Corporation.

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