title: Dosimetric impact of a CT metal artefact suppression algorithm for proton, electron and photon therapies.
abstract: Accurate dose calculation is essential to precision radiation treatment planning and this accuracy depends upon anatomic and tissue electron density information. Modern treatment planning inhomogeneity corrections use x-ray CT images and calibrated scales of tissue CT number to electron density to provide this information. The presence of metal in the volume scanned by an x-ray CT scanner causes metal induced image artefacts that influence CT numbers and thereby introduce errors in the radiation dose distribution calculated. This paper investigates the dosimetric improvement achieved by a previously proposed x-ray CT metal artefact suppression technique when the suppressed images of a patient with bilateral hip prostheses are used in commercial treatment planning systems for proton, electron or photon therapies. For all these beam types, this clinical image and treatment planning study reveals that the target may be severely underdosed if a metal artefact-contaminated image is used for dose calculations instead of the artefact suppressed one. Of the three beam types studied, the metal artefact suppression is most important for proton therapy dose calculations, intermediate for electron therapy and least important for x-ray therapy but still significant. The study of a water phantom having a metal rod simulating a hip prosthesis indicates that CT numbers generated after image processing for metal artefact suppression are accurate and thus dose calculations based on the metal artefact suppressed images will be of high fidelity.
authors.affiliation: School of Health Sciences, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47907, USA.
authors.forename: Jikun
authors.initials: J
authors.lastname: Wei
authors.forename: George A
authors.initials: GA
authors.lastname: Sandison
authors.forename: Wen-Chien
authors.initials: WC
authors.lastname: Hsi
authors.forename: Michael
authors.initials: M
authors.lastname: Ringor
authors.forename: Xiaoyi
authors.initials: X
authors.lastname: Lu
mesh_terms: D000465:Algorithms; D016477:Artifacts; D004583:Electrons / Q000627:therapeutic use; D006801:Humans; D008670:Metals; D017785:Photons / Q000627:therapeutic use; D019736:Prostheses and Implants; D061766:Proton Therapy; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D008670:Metals