A phantom study of the accuracy of CT, MR and PET image registrations with a block matching-based algorithm.
OBJECTIVE
The aim of the present study was to quantitatively assess the performance of a block matching-based automatic registration algorithm integrated within the commercial treatment planning system designated ISOgray from Dosisoft. The accuracy of the process was evaluated by a phantom study on computed tomography (CT), magnetic resonance (MR) and positron emission tomography (PET) images.


METHODS
Two phantoms were used to carry out this study: the cylindrical Jaszczak phantom and the anthropomorphic Liqui-Phil Head Phantom (the Phantom Laboratory), containing fillable spheres. External fiducial markers were used to quantify the accuracy of 41 CT/CT, MR/CT and PET/CT automatic registrations with images of the rotated and tilted phantoms.


RESULTS
The study first showed that a cylindrical phantom was not adapted for the evaluation of the performance of a block matching-based registration software. Secondly, the Liqui-Phil Head Phantom study showed that the algorithm was able to perform automatic registrations of CT/CT and MR/CT images with differences of up to 40 degrees in phantom rotation and of up to 20-30 degrees for PET/CT with accuracy below the image voxel size.


CONCLUSIONS
The study showed that the block matching-based automatic registration software under investigation was robust, reliable and yielded very satisfactory results. This phantom-based test can be integrated into a periodical quality assurance process and used for any commissioning of image registration software for radiation therapy.
Isambert
A
A
Service de physique médicale, institut Gustave-Roussy, 39, rue Camille-Desmoulins, 94805 Villejuif, France. aurelie.isambert@igr.fr
Bonniaud
G
G
Lavielle
F
F
Malandain
G
G
Lefkopoulos
D
D
D000465:Algorithms; D001331:Automation; D001921:Brain / Q000000981:diagnostic imaging / Q000473:pathology; D006257:Head; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods / Q000592:standards; D012984:Software; D014057:Tomography, X-Ray Computed / Q000379:methods*