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.
journal_name
Phys Med Bioljournal_title
Physics in medicine and biologyauthors
Fiorino C,Maggiulli E,Broggi S,Liberini S,Cattaneo GM,Dell'oca I,Faggiano E,Di Muzio N,Calandrino R,Rizzo Gdoi
10.1088/0031-9155/56/11/008subject
Has Abstractpub_date
2011-06-07 00:00:00pages
3301-12issue
11eissn
0031-9155issn
1361-6560pii
S0031-9155(11)79519-7journal_volume
56pub_type
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