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01.12.2019 | Research | Ausgabe 1/2019 Open Access

Radiation Oncology 1/2019

A novel amplitude binning strategy to handle irregular breathing during 4DMRI acquisition: improved imaging for radiotherapy purposes

Zeitschrift:
Radiation Oncology > Ausgabe 1/2019
Autoren:
Z. van Kesteren, A. van der Horst, O. J. Gurney-Champion, I. Bones, D. Tekelenburg, T. Alderliesten, G. van Tienhoven, R. Klaassen, H. W. M. van Laarhoven, A. Bel
Wichtige Hinweise

Electronic supplementary material

The online version of this article (https://​doi.​org/​10.​1186/​s13014-019-1279-z) contains supplementary material, which is available to authorized users.

Abstract

Background

For radiotherapy of abdominal cancer, four-dimensional magnetic resonance imaging (4DMRI) is desirable for tumor definition and the assessment of tumor and organ motion. However, irregular breathing gives rise to image artifacts. We developed a outlier rejection strategy resulting in a 4DMRI with reduced image artifacts in the presence of irregular breathing.

Methods

We obtained 2D T2-weighted single-shot turbo spin echo images, with an interleaved 1D navigator acquisition to obtain the respiratory signal during free breathing imaging in 2 patients and 12 healthy volunteers. Prior to binning, upper and lower inclusion thresholds were chosen such that 95% of the acquired images were included, while minimizing the distance between the thresholds (inclusion range (IR)). We compared our strategy (Min95) with three commonly applied strategies: phase binning with all images included (Phase), amplitude binning with all images included (MaxIE), and amplitude binning with the thresholds set as the mean end-inhale and mean end-exhale diaphragm positions (MeanIE). We compared 4DMRI quality based on:
  • Data included (DI); percentage of images remaining after outlier rejection.
  • Reconstruction completeness (RC); percentage of bin-slice combinations containing at least one image after binning.
  • Intra-bin variation (IBV); interquartile range of the diaphragm position within the bin-slice combination, averaged over three central slices and ten respiratory bins.
  • IR.
  • Image smoothness (S); quantified by fitting a parabola to the diaphragm profile in a sagittal plane of the reconstructed 4DMRI.
A two-sided Wilcoxon’s signed-rank test was used to test for significance in differences between the Min95 strategy and the Phase, MaxIE, and MeanIE strategies.

Results

Based on the fourteen subjects, the Min95 binning strategy outperformed the other strategies with a mean RC of 95.5%, mean IBV of 1.6 mm, mean IR of 15.1 mm and a mean S of 0.90. The Phase strategy showed a poor mean IBV of 6.2 mm and the MaxIE strategy showed a poor mean RC of 85.6%, resulting in image artifacts (mean S of 0.76). The MeanIE strategy demonstrated a mean DI of 85.6%.

Conclusions

Our Min95 reconstruction strategy resulted in a 4DMRI with less artifacts and more precise diaphragm position reconstruction compared to the other strategies.

Trial registration

Volunteers: protocol W15_373#16.007; patients: protocol NL47713.018.14
Zusatzmaterial
Additional file 1: Determination of the optimal percentage of outlier exclusion, pictures of the phantom measurements set-up, the calculation of the expected underestimation for a cos6 breathing pattern, the breathing patterns per subject, and the quality parameters values for each subject for each of the described outlier rejection and binning strategies. (PDF 1903 kb)
13014_2019_1279_MOESM1_ESM.pdf
Literatur
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