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

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 (MR-GTV) 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. MR-GTV 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/MR-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 MR-GTV 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. Multi-modality 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.

• Authors: J Tan, D Lim Joon, G Fitt, M Wada, M Lim Joon, A Mercuri, M Marr, M Chao, V Khoo
• Journal: Journal of medical imaging and radiation oncology (J Med Imaging Radiat Oncol) Vol. 54 Issue 6 Pg. 562-8 (Dec 2010) ISSN: 1754-9485 [Electronic] Australia
• PMID: 21199435 (Publication Type: Journal Article)
• Copyright: © 2010 The Authors. Journal of Medical Imaging and Radiation Oncology © 2010 The Royal Australian and New Zealand College of Radiologists.

Chemical References

• Contrast Media

Topics

• Adult
• Aged
• Contrast Media
• Female
• Humans
• Image Enhancement (methods)
• Magnetic Resonance Imaging (methods)
• Male
• Middle Aged
• Pilot Projects
• Prospective Studies
• Radiotherapy Planning, Computer-Assisted (methods)
• Radiotherapy, Conformal (methods)
• Rectal Neoplasms (diagnostic imaging, pathology)
• Rectum (diagnostic imaging, pathology)
• Tomography, X-Ray Computed (methods)
• Tumor Burden