The utility of multimodality imaging with CT and MRI in defining rectal tumour volumes for radiotherapy treatment planning: A pilot study

J. Tan, D. Lim Joon, G. Fitt, M. Wada, M. Lim Joon, A. Mercuri, M. Marr, M. Chao, V. Khoo

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Abstract

Aims: This study compares the volumetric and spatial relationships of gross tumour volume (GTV) derived from CT (CT-GTV) and GTV derived from MRI (-) to determine the utility of multi-modality imaging for radiotherapy treatment planning in rectal cancer.Methods and Materials: Fifteen patients with T3 rectal cancer were accrued over 18 months. The male-:-female ratio was 2:1. The average age was 60.3 years (range 38-79). All patients underwent a diagnostic MRI and CT and MRI simulation. Data sets were co-registered. A site specialised diagnostic radiologist contoured all volumes in consultation with a radiation oncologist. CT-GTV was contoured while blinded to MR data sets. - was contoured independently 2-4 weeks later whilst blinded to its respective CT-GTV data. Tumour volumes were analysed for three anatomical subregions (sigmoid, rectal and anal). Reference points on tumour volumes were used for spatial comparison and analysis.Results: The mean CT-GTV/- ratio was 1.2 (range 0.5-2.9). The tumour volume ratios for the rectal subregion were well correlated. CT-GTV provided adequate spatial coverage of tumour in reference to - with the average mean discrepancy of 0.12 (range -0.08-0.38) or a maximum discrepancy of <0.4-cm (1.54 standard deviation). CT-GTV coverage was inadequate for tumours with MRI evidence of anal and sigmoid invasion.Conclusions: Conventional simulation CT imaging provided a reasonable estimate of the GTV. - imaging with staging MRI can assist target volume definition where there is involvement of the sigmoid and anorectal region and avoid geographic misses. The role of a simulation MRI may aid in this process but remains investigational.

Original languageEnglish
Pages (from-to)562-568
Number of pages7
JournalJournal of Medical Imaging and Radiation Oncology
Volume54
Issue number6
DOIs
Publication statusPublished - Dec 2010
Externally publishedYes

Keywords

  • CT
  • GTV
  • MRI
  • Radiotherapy
  • Rectal cancer
  • Target volume
  • Treatment planning

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