Background/Aim. Development of imaging techniques, computed tomography (CT),
magnetic resonance imaging (MRI), and positron emission tomography (PET),
made great impact on radiotherapy treatment planning by improving the
localization of target volumes. Improved localization allows better local
control of tumor volumes, but also minimizes geographical misses. Mutual
information is obtained by registration and fusion of images achieved
manually or automatically. The aim of this study was to validate the CT-MRI
image fusion method and compare delineation obtained by CT versus CT-MRI
image fusion. Methods. The image fusion software (XIO CMS 4.50.0) was applied
to delineate 16 patients. The patients were scanned on CT and MRI in the
treatment position within an immobilization device before the initial
treatment. The gross tumor volume (GTV) and clinical target volume (CTV) were
delineated on CT alone and on CT+MRI images consecutively and image fusion
was obtained. Results. Image fusion showed that CTV delineated on a CT image
study set is mainly inadequate for treatment planning, in comparison with CTV
delineated on CT-MRI fused image study set. Fusion of different modalities
enables the most accurate target volume delineation. Conclusion. This study
shows that registration and image fusion allows precise target localization
in terms of GTV and CTV and local disease control.
FDG PET/CT for rectal carcinoma radiotherapy treatment planning: comparison of functional volume delineation algorithms and clinical challenges