title: Estimation of urinary stone composition by automated processing of CT images.
abstract: The objective of this article was developing an automated tool for routine clinical practice to estimate urinary stone composition from CT images based on the density of all constituent voxels. A total of 118 stones for which the composition had been determined by infrared spectroscopy were placed in a helical CT scanner. A standard acquisition, low-dose and high-dose acquisitions were performed. All voxels constituting each stone were automatically selected. A dissimilarity index evaluating variations of density around each voxel was created in order to minimize partial volume effects: stone composition was established on the basis of voxel density of homogeneous zones. Stone composition was determined in 52% of cases. Sensitivities for each compound were: uric acid: 65%, struvite: 19%, cystine: 78%, carbapatite: 33.5%, calcium oxalate dihydrate: 57%, calcium oxalate monohydrate: 66.5%, brushite: 75%. Low-dose acquisition did not lower the performances (P < 0.05). This entirely automated approach eliminates manual intervention on the images by the radiologist while providing identical performances including for low-dose protocols.
authors.affiliation: Department of Urology, Pitié-Salpêtrière Hospital, Paris, France. Gregoire.Chevreau@imag.fr
authors.forename: Grégoire
authors.initials: G
authors.lastname: Chevreau
authors.forename: Jocelyne
authors.initials: J
authors.lastname: Troccaz
authors.forename: Pierre
authors.initials: P
authors.lastname: Conort
authors.forename: Raphaëlle
authors.initials: R
authors.lastname: Renard-Penna
authors.forename: Alain
authors.initials: A
authors.lastname: Mallet
authors.forename: Michel
authors.initials: M
authors.lastname: Daudon
authors.forename: Pierre
authors.initials: P
authors.lastname: Mozer
mesh_terms: D002129:Calcium Oxalate / Q000032:analysis; D002130:Calcium Phosphates / Q000032:analysis; D003553:Cystine / Q000032:analysis; D006801:Humans; D012680:Sensitivity and Specificity; D036542:Tomography, Spiral Computed / Q000379:methods*; D014527:Uric Acid / Q000032:analysis; D014545:Urinary Calculi / Q000737:chemistry* / Q000000981:diagnostic imaging*
chemical_list: D002130:Calcium Phosphates; D002129:Calcium Oxalate; D014527:Uric Acid; D003553:Cystine; C494366:calcium phosphate, dibasic, dihydrate