Clinical Investigation
Comparison of Measurements of the Uterus and Cervix Obtained by Magnetic Resonance and Transabdominal Ultrasound Imaging to Identify the Brachytherapy Target in Patients With Cervix Cancer

https://doi.org/10.1016/j.ijrobp.2013.12.004Get rights and content

Purpose

To compare measurements of the uterus and cervix obtained with magnetic resonance imaging (MRI) and transabdominal ultrasound to determine whether ultrasound can identify the brachytherapy target and be used to guide conformal brachytherapy planning and treatment for cervix cancer.

Methods and Materials

Consecutive patients undergoing curative treatment with radiation therapy between January 2007 and March 2012 were included in the study. Intrauterine applicators were inserted into the uterine canal while patients were anesthetized. Images were obtained by MRI and transabdominal ultrasound in the longitudinal axis of the uterus with the applicator in treatment position. Measurements were taken at the anterior and posterior surface of the uterus at 2.0-cm intervals along the applicator, from the external os to the tip of the applicator. Data were analyzed using Bland Altman plots examining bias and 95% limits of agreement.

Results

A total of 192 patients contributed 1668 measurements of the cervix and uterus. Mean (±SD) differences of measurements between imaging modalities at the anterior and posterior uterine surface ranged from 1.5 (±3.353) mm to 3.7 (±3.856) mm, and −1.46 (±3.308) mm to 0.47 (±3.502) mm, respectively. The mean differences were less than 3 mm in the cervix. The mean differences were less than 1.5 mm at all measurement points on the posterior surface.

Conclusion

Differences in the measurements of the cervix and uterus obtained by MRI and ultrasound were within clinically acceptable limits. Transabdominal ultrasound can be substituted for MRI in defining the target volume for conformal brachytherapy treatment of cervix cancer.

Introduction

Brachytherapy for cervix cancer is essential for controlling local disease by allowing high doses of radiation to be delivered to the residual disease from within the cervix and tumor (1). The success of brachytherapy rests on accurate identification of the uterus, cervix, and residual disease; accurate placement of the intrauterine applicator within the uterine canal; and sparing of surrounding normal tissue (2). Historically, brachytherapy applicators were placed under direct vision, and implant quality was assessed with x-rays. These traditional methods, however, do not enable evaluation of the uterine and cervical anatomy, the residual tumor, or the correct placement of the applicators within the cervical canal (2). Although considered outdated in some parts of the world, traditional methods continue in many countries, particularly in those with a high incidence of cervix cancer (3). The use of soft tissue imaging for cervix brachytherapy is increasing in some advanced economies and well-resourced departments (4). The Groupe Européen de Curiethérapie and European Society for Radiotherapy and Oncology (GEC-ESTRO) have been instrumental in advancing the use of soft tissue imaging with a particular emphasis on the use of MRI (5). MRI has superior anatomy and tumor recognition when used in brachytherapy (6). Unfortunately, MRI is expensive and difficult to access for many clinical centers. It is also not suitable for patients with implanted devices, those with claustrophobia, and those with large body habitus. These drawbacks make it necessary to find alternative imaging modalities that provide information of similar quality to MRI but are more readily accessible and affordable 7, 8. Ultrasound is an inexpensive imaging modality that offers good soft tissue information and is widely available. The aims of this study were to compare measurements of the uterus and cervix obtained with transabdominal ultrasound to those obtained using MRI to determine the level of agreement between the imaging modalities. The purpose was to determine whether transabdominal ultrasound can be substituted for MRI in the application of conformal brachytherapy in cervix cancer.

Section snippets

Methods and Materials

This study was approved by the Divisional Review Panel for Retrospective studies at the Peter MacCallum Cancer Centre and by the Monash University Human Research Ethics Committee (MUHREC).

Results

Data from 198 patients was included in this study. Six patients were excluded because of insufficient data; 4 of these had missing information for 1 or more measurements and 2 were excluded because of data fluctuations caused by large fibroids that were unable to be visualized in the ultrasound field of view. Measurements from the external os to 4 cm along the applicator were available for 192 patients. Measurements around the tip of the applicator were available for 172 of these patients.

Discussion

Improving brachytherapy practices for patients with cervix cancer requires new avenues to make it possible for all treating clinicians to identify the brachytherapy target. This study has shown that ultrasound can be used to delineate the cervix and uterus to determine the target for use in planning conformal brachytherapy treatments for cervix cancer. The greatest potential of incorporating ultrasound into the brachytherapy program is the ability to improve accuracy of applicator placement and

References (23)

Cited by (41)

  • Ultrasound-guided Brachytherapy for Cervix Cancer

    2021, Clinical Oncology
    Citation Excerpt :

    Another important reason to include ultrasound to guide applicator placement is to avoid abandonment of the brachytherapy procedure. Patients are more likely to experience recurrences and failure when treatment has been abandoned due to inability to deliver brachytherapy because of persistent disease, canal stenosis, uterine pathologies and anatomical variations [9–11]. The use of ultrasound can assist with safe and accurate applicator placement in these difficult circumstances and reduce the likelihood of abandoning the procedure.

  • Intermediate-term results of trans-abdominal ultrasound (TAUS)-guided brachytherapy in cervical cancer

    2018, Gynecologic Oncology
    Citation Excerpt :

    The largest study, by Van Dyk et al., reported very promising first results and treatment-related toxicities [12]. A recently published study by Van Dyk et al. measured TAUS versus MRI, and showed the correlations between the two imaging modalities [13]. Our preliminary study reported the successful use of TAUS-guided brachytherapy in 29 patients, with good treatment results while limiting toxicity.

  • Use of 3D transabdominal ultrasound imaging for treatment planning in cervical cancer brachytherapy: Comparison to magnetic resonance and computed tomography

    2017, Brachytherapy
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    Although the addition of 3DTAUS to CT seems to lead to improved treatment plans, the cohort size is too small to draw definitive conclusions. Nonetheless, we believe that our work is in line with previously reported clinical data confirming the clinical usefulness of ultrasound, in particular this state-of-the-art 3D transabdominal technology, for treatment planning in cervical cancer brachytherapy (10, 11). Further investigation is needed to confirm the usefulness of 3DUS in GYN brachytherapy, not only for real-time guidance, but also as an additional imaging modality to supplement MRI and/or CT imaging in an effort to improve volumetric treatment planning.

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Conflict of interest: none.

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