title: Introducing the Jacobian-volume-histogram of deforming organs: application to parotid shrinkage evaluation.
abstract: The Jacobian of the deformation field of elastic registration between images taken during radiotherapy is a measure of inter-fraction local deformation. The histogram of the Jacobian values (Jac) within an organ was introduced (JVH-Jacobian-volume-histogram) and first applied in quantifying parotid shrinkage. MVCTs of 32 patients previously treated with helical tomotherapy for head-neck cancers were collected. Parotid deformation was evaluated through elastic registration between MVCTs taken at the first and last fractions. Jac was calculated for each voxel of all parotids, and integral JVHs were calculated for each parotid; the correlation between the JVH and the planning dose-volume histogram (DVH) was investigated. On average, 82% (±17%) of the voxels shrinks (Jac < 1) and 14% (±17%) shows a local compression >50% (Jac < 0.5). The best correlation between the DVH and the JVH was found between V10 and V15, and Jac < 0.4-0.6 (p < 0.01). The best constraint predicting a higher number of largely compressing voxels (Jac0.5<7.5%, median value) was V15 ≥ 75% (OR: 7.6, p = 0.002). Jac and the JVH are promising tools for scoring/modelling toxicity and for evaluating organ/contour variations with potential applications in adaptive radiotherapy.
authors.affiliation: Medical Physics, San Raffaele Scientific Institute, Milano, Italy. fiorino.claudio@hsr.it
authors.forename: Claudio
authors.initials: C
authors.lastname: Fiorino
authors.forename: Eleonora
authors.initials: E
authors.lastname: Maggiulli
authors.forename: Sara
authors.initials: S
authors.lastname: Broggi
authors.forename: Simone
authors.initials: S
authors.lastname: Liberini
authors.forename: Giovanni Mauro
authors.initials: GM
authors.lastname: Cattaneo
authors.forename: Italo
authors.initials: I
authors.lastname: Dell'oca
authors.forename: Elena
authors.initials: E
authors.lastname: Faggiano
authors.forename: Nadia
authors.initials: N
authors.lastname: Di Muzio
authors.forename: Riccardo
authors.initials: R
authors.lastname: Calandrino
authors.forename: Giovanna
authors.initials: G
authors.lastname: Rizzo
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019583:Dose Fractionation, Radiation; D004548:Elasticity; D005260:Female; D006258:Head and Neck Neoplasms / Q000473:pathology / Q000532:radiotherapy; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010306:Parotid Gland / Q000473:pathology* / Q000528:radiation effects