King's College London

Research portal

Evaluation of a multi-atlas CT synthesis approach for MRI-only radiotherapy treatment planning

Research output: Contribution to journalArticle

F. Guerreiro, N. Burgos, A. Dunlop, K. Wong, I. Petkar, C. Nutting, K. Harrington, S. Bhide, K. Newbold, D. Dearnaley, N. M. deSouza, V. A. Morgan, J. McClelland, S. Nill, M. J. Cardoso, S. Ourselin, U. Oelfke, A. C. Knopf

Original languageEnglish
Pages (from-to)7-17
Number of pages11
JournalPhysica Medica
Early online date24 Feb 2017
Publication statusPublished - 1 Mar 2017

King's Authors


Background and purpose Computed tomography (CT) imaging is the current gold standard for radiotherapy treatment planning (RTP). The establishment of a magnetic resonance imaging (MRI) only RTP workflow requires the generation of a synthetic CT (sCT) for dose calculation. This study evaluates the feasibility of using a multi-atlas sCT synthesis approach (sCTa) for head and neck and prostate patients. Material and methods The multi-atlas method was based on pairs of non-rigidly aligned MR and CT images. The sCTa was obtained by registering the MRI atlases to the patient's MRI and by fusing the mapped atlases according to morphological similarity to the patient. For comparison, a bulk density assignment approach (sCTbda) was also evaluated. The sCTbda was obtained by assigning density values to MRI tissue classes (air, bone and soft-tissue). After evaluating the synthesis accuracy of the sCTs (mean absolute error), sCT-based delineations were geometrically compared to the CT-based delineations. Clinical plans were re-calculated on both sCTs and a dose-volume histogram and a gamma analysis was performed using the CT dose as ground truth. Results Results showed that both sCTs were suitable to perform clinical dose calculations with mean dose differences less than 1% for both the planning target volume and the organs at risk. However, only the sCTa provided an accurate and automatic delineation of bone. Conclusions Combining MR delineations with our multi-atlas CT synthesis method could enable MRI-only treatment planning and thus improve the dosimetric and geometric accuracy of the treatment, and reduce the number of imaging procedures.

View graph of relations

© 2018 King's College London | Strand | London WC2R 2LS | England | United Kingdom | Tel +44 (0)20 7836 5454