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Ultrasonic mirror image from ruthenium plaque facilitates calculation of uveal melanoma treatment dose
  1. Charlotte Alfast Espensen1,2,
  2. Peter Koch Jensen3,
  3. Lotte Stubkjær Fog1,
  4. Ane Lindegaard Appelt4,1,
  5. Kristian Klemp2,
  6. Hans Callø Fledelius2,
  7. Lena Specht1,
  8. Jens Folke Kiilgaard2
  1. 1Department of Oncology, Section of Radiotherapy, Rigshospitalet, Copenhagen Ø, Denmark
  2. 2Department of Ophthalmology, Rigshospitalet, Copenhagen Ø, Denmark
  3. 3Department of Ophthalmology, Roskilde Hospital, Roskilde, Denmark
  4. 4Leeds Institute of Cancer & Pathology, University of Leeds and St. James's University Hospital, Leeds, UK
  1. Correspondence to Charlotte Alfast Espensen, Copenhagen University Hospital, Rigshospitalet, Department of Ophthalmology, Department of Oncology, Section of Radiotherapy, Blegdamsvej 9, Copenhagen Ø 2100, Denmark; charlotte.alfast.espensen{at}regionh.dk

Abstract

Background/aims To present a new method to determine dose depth and the distance from the concave side of the plaque to the tumour base in patients with uveal melanoma treated with ruthenium-106 based on ultrasonic mirror image.

Methods We used the mirror image associated with ultrasound during plaque brachytherapy to determine intraobserver reproducibility and interobserver agreement between two surgeons. 230 eyes with primary uveal melanoma were included in a retrospective analysis to determine the distance from the plaque to the tumour base using ultrasound. A phantom study was used to illustrate the effects on radiation dose to apex of the tumour when the dose depth was incorrectly determined. Doses to apex of the tumour were determined using Plaque Simulator.

Results The intraobserver variation in dose depth measurement with plaque was significantly lower than for measures without plaque (p<0.001). Agreement between the surgeons was better with a plaque in place. Distances from the plaque to the tumour base were distributed with mean=0.99 (median: 1, range: 0.1–2.9 mm). From the phantom study, it was clear that the tumour did not receive the prescribed 100 Gy if the dose depth was incorrectly determined.

Conclusions The dose depth in patients with uveal melanoma must be measured accurately for correct calculation of the radiation dose to the apex of the tumour. Repeated in vivo and in vitro ultrasound measurements of dose depth showed higher variance than measurements using the mirror image produced from a ruthenium plaque. Using the mirror image thus help to improve the dose calculation.

  • Treatment other
  • Diagnostic tests/Investigation
  • Imaging
  • Neoplasia
  • Sclera and Episclera

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Footnotes

  • Contributors CAE collected the data, cleaned the data, wrote the statistical analysis plan, did the data analysis and interpretation, drafted the manuscript and did critical revision of the final paper. She is guarantor. JFK helped collecting the data, helped in the data analysis and interpretation, contributed to drafting the manuscript and did critical revision of the paper. Furthermore, he approved the final version to be submitted. PKJ helped collecting the data, contributed to drafting the manuscript and did critical revision of the paper. Furthermore, he approved the final version to be submitted. LSF helped with data analysis and interpretation and did critical revision of the final paper. Furthermore, she approved the final version to be submitted. ALA wrote the statistical analysis plan, did the data analysis and interpretation, and did critical revision of the final paper. Furthermore, she approved the final version to be submitted. KK helped collecting the data and did critical revision of the final paper. Furthermore, he approved the final version to be submitted. HCF helped collecting the data, contributed to drafting the manuscript and did critical revision of the final paper. Furthermore, he approved the final version to be submitted. LS did critical revision of the final paper. Furthermore, she approved the final version to be submitted.

  • Funding The work was supported by research grants Synoptik-Foundation, The Danish Eye Research Foundation (Øjenfonden), the Danish Cancer Research Foundation (Dansk Kræftforsknings Fond) and Arvid Nilssons Foundation.

  • Competing interests None declared.

  • Ethics approval Danish Data Protection Agency (RH-2015-205 I-Suite 04140), The Danish Healthcare System (3-3013-980/1/).

  • Provenance and peer review Not commissioned; externally peer reviewed.

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