Esophageal cancer
Interfractional variability of respiration-induced esophageal tumor motion quantified using fiducial markers and four-dimensional cone-beam computed tomography

https://doi.org/10.1016/j.radonc.2017.05.015Get rights and content

Abstract

Purpose

To investigate the interfractional variability of respiration-induced esophageal tumor motion using fiducial markers and four-dimensional cone-beam computed tomography (4D-CBCT) and assess if a 4D-CT is sufficient for predicting the motion during the treatment.

Materials and methods

Twenty-four patients with 63 markers visible in the retrospectively reconstructed 4D-CBCTs were included. For each marker, we calculated the amplitude and trajectory of the respiration-induced motion. Possible time trends of the amplitude over the treatment course and the interfractional variability of amplitudes and trajectory shapes were assessed. Further, the amplitudes measured in the 4D-CT were compared to those in the 4D-CBCTs.

Results

The amplitude was largest in the cranial–caudal direction of the distal esophagus (mean: 7.1 mm) and proximal stomach (mean: 7.8 mm). No time trend was observed in the amplitude over the treatment course. The interfractional variability of amplitudes and trajectory shapes was limited (mean: ≤1.4 mm). Moreover, small and insignificant deviation was found between the amplitudes quantified in the 4D-CT and in the 4D-CBCT (mean absolute difference: ≤1.0 mm).

Conclusions

The limited interfractional variability of amplitudes and trajectory shapes and small amplitude difference between 4D-CT-based and 4D-CBCT-based measurements imply that a single 4D-CT would be sufficient for predicting the respiration-induced esophageal tumor motion during the treatment course.

Section snippets

Patients and markers

We included 24 esophageal cancer patients with implanted gold markers, who were also included in former studies [11], [12], [14]. Two different types of gold markers were implanted: a solid marker (Cook Medical, Limerick, Ireland; or in–house manufactured) and a flexible coil-shaped marker (Visicoil; IBA Dosimetry, Bartlett, TN, USA) [11]. For each patient, 2–5 markers were placed at the cranial and caudal border of the primary tumor and, preferably, in the center of the tumor. The details of

Results

For over 97% of the markers, the interfractional mean amplitude was <10.0 mm in all three directions. The average motion trajectory and its 95% confidence interval (CI) in the four regions of the esophagus illustrated in Supplementary Fig. A2 indicate a predominant respiration-induced tumor motion in the CC direction and in the distal esophagus and proximal stomach. For the three directions and four regions, Supplementary Fig. A3 illustrates the amplitudes for individual markers and Table 2

Discussion

This is the first study that applied retrospectively reconstructed 4D-CBCT with implanted gold markers to investigate the interfractional variability of the respiration-induced esophageal tumor motion. The mean interfractional variability of amplitudes and trajectory shapes was found to be ≤1.4 mm and the mean deviation between the amplitudes measured in the 4D-CT and in the 4D-CBCT was ≤1.0 mm. These findings suggest that the amplitudes and trajectory shapes of the respiration-induced esophageal

Conflicts of interest

Dr. T. Alderliesten and Dr. A. Bel are both involved in projects supported by Elekta. Elekta had no involvement in the study design, the data collection, analysis and interpretation, and the writing of the manuscript.

Acknowledgments

The authors thank Elekta for the financial support of this work and thank Mr. C.M. van Leeuwen (Department of Radiation Oncology, Academic Medical Center, the Netherlands) for advices on statistical analysis.

References (33)

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