Imagerie portale en radiotherapie: Localisation automatique de la prostate

Abstract

Cette etude, faite en collaboration avec le departement de radio-oncologie du CHUQ, Pavillon Hotel-Dieu de Quebec, a permis de developper un algorithme de localisation de la prostate lors des traitements de radiotherapie en utilisant l'imagerie portale. La localisation se fait a deux niveaux, soit la detection de marqueur radio-opaque implante a l'apex prostatique et au niveau des structures osseuses de la region pelvienne.

La methode de detection du marqueur est basee sur la recherche d'un minimum global dans le champ de traitement. Un critere a ete trouve pour ameliorer la robustesse au bruit et aux attenuations de contours osseux. Cet algorithme a ete valide avec des images cliniques. Pour les structures osseuses, la deviation de leurs positions par rapport a une image de reference est mesuree par correlation d'images de contours osseux apres avoir rehausses ces derniers dans les images originales. Les images doivent aussi etre restaurees pour eliminer les artefacts. Cet algorithme a ete valide avec des images de squelette.

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This study, carried out in collaboration with the radiation oncology department of the CHUQ, Pavillon Hotel-Dieu de Quebec, made it possible to develop an algorithm for locating the prostate during radiotherapy treatments using portal imaging. Localization is done at two levels, namely the detection of radiopaque marker implanted at the prostatic apex and at the level of the bony structures of the pelvic region.

The marker detection method is based on the search for a global minimum in the treatment field. A criterion was found to improve the robustness to noise and bone contour attenuations. This algorithm has been validated with clinical images. For the bony structures, the deviation of their positions with respect to a reference image is measured by correlation of bone contour images after having enhanced the latter in the original images. Images must also be restored to remove artifacts. This algorithm has been validated with skeleton images.