Elsevier

Radiotherapy and Oncology

Volume 50, Issue 3, 1 March 1999, Pages 367-370
Radiotherapy and Oncology

Three-dimensional movement of a liver tumor detected by high-speed magnetic resonance imaging

https://doi.org/10.1016/S0167-8140(98)00140-6Get rights and content

Abstract

Objective: Three-dimensional (3D) movement of a spherical liver tumor during respiration was investigated with magnetic resonance imaging (MRI) using a high-speed sequence.

Methods: A marker was placed on the surface of the patient as a reference of distance. Repetition time (TR) was 7.7 ms, echo time (TE) was 4.2 ms, flip angle was 20°, section thickness was 8 mm, and a 256×128 matrix was used. The acquisition time was 1.0 s followed by an interval of 0.5 s. The 20 tumor contours extracted during 30 s were superimposed on sagittal and coronal MR images.

Results: The maximum value of tumor edge location was 3.9 cm in the cranio–caudal direction, 2.3 cm in the ventro–dorsal direction, and 3.1 cm in the lateral direction. The mean length of tumor displacement observed was 2.1 cm in the cranio–caudal direction, 0.8 cm in the ventro–dorsal and 0.9 cm in the left–right direction, respectively. The locus of the center of the tumor contour in the sagittal cross section was inclined at 23° and in the coronal cross section was inclined at 18° to the cranio–caudal axis of body.

Conclusion: In conclusion, 3D movement of a spherical liver tumor was detected using rapid MRI sequential examinations. Magnetic resonance imaging has a potential to improve the accuracy of the planning target volume of a liver tumor.

Introduction

Small field, high dose radiotherapy was reported to be useful for solitary liver tumors using convergent X-ray beams and sophisticated localization techniques [1], [2].

Three-dimensional conferral radiotherapy (3D CRT) is expected to be a new strategy to give higher dose to the target volume and reduced dose to normal tissues compared to conventional radiotherapy [3], [4]. Computed topographic (CT) images are used for the treatment planning and dose calculation of these treatments. Liver tumors are expected to be a good candidate for 3D CRT because they can be visualized well by computed tomography (CT). However, since the tumor may change location due to respiratory movement, uncertainty of CT planning is recognized as a major obstacle for 3D CRT of liver tumor [5].

It is desirable to determine the target volume taking into account the 3D respiratory movements of the clinical target volume. However, there has been little information about 3D movement of liver tumors. In this study, movement of a solitary liver tumour during respiration was investigated with MRI using a high-speed sequence.

Section snippets

Methods

The MRI study was performed in a patient with a solitary spherical metastatic liver tumor of nasopharyngeal carcinoma using a Magnetom Vision 1.5T MRI scanner (Siemens AG, Erlangen, Germany) and its whole-body coil. The patient was scanned in the supine position. A marker, which has five parallel bars in every 2 cm, was placed on the surface of the patient as a ruler for measuring purpose. Each bar can be seen as a dot on a MR image, when they are scanned vertically to their axis. A phased

Results

The tumor was well visualized with high speed MR imaging. Movements of tumor and liver contour in sagittal and coronal planes were visualized at a real-time rate (one image in 1.5 s) on the image viewer. It was apparent that the liver and the tumor contour moved not only in the cranio–caudal direction but also in the ventro–dorsal direction.

The 20 tumor contours extracted during the 30 seconds free-breathing period were superimposed on sagittal and coronal MR images and are shown in Fig. 1a,b,

Discussion

Three-dimensional conformal radiotherapy requires CT simulation and 3D treatment planning. Tumor location in the liver is usually calculated from CT images taken in a single session. There have been reports about movement of liver surface due to respiratory movement [6], [7], [8] but little has been known about the movement of tumor itself in the liver. Rapid CT scanning may be useful to detect the movement of liver tumors in a trans–axial plane as we have seen for lung tumor in a previous

References (10)

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