Digital correction of computed X-radiographs for coral densitometry

• Published in: Journal of Experimental Marine Biology and Ecology
• Main Authors: Duprey, Nicolas, Boucher, Hugues, Jiménez, Carlos
• Other Authors: Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centro de Investigación en Ciencias del Mar y Limnología (CIMAR), Universidad Nacional de Costa Rica
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2012
• Subjects: Calcification rate Coral densitometry Coral skeleton Density Porites sp. Siderastrea siderea; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; [SDE.MCG]Environmental Sciences/Global Changes; [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph]; Ocean acidification
• Online Access: https://hal.sorbonne-universite.fr/hal-00794477; https://hal.sorbonne-universite.fr/hal-00794477/document; https://hal.sorbonne-universite.fr/hal-00794477/file/Duprey_et_al_2012_JEMBE_author_edit.pdf; https://doi.org/10.1016/j.jembe.2012.09.007

International audience The recent increase in sea surface temperature and ocean acidification raises major concerns about the evolution of the coral calcification rate. Digitized X-radiographs have been used for coral skeleton density measurements since the 1980s. The main limitation of coral densitometry from digitized X-radiographs is the X-ray intensity heterogeneity due to spherical spreading (inverse square law) and heel effect. Until now, extra X-ray images or aluminium standards have been used to correct X-radiographs. However, such corrective methods may be constraining when working with a high number of coral samples. Here, we present an inexpensive, straightforward, and accurate digital detrending (DD) method to correct the heterogeneities of the X-ray irradiation that affect X-radiographs. The X-radiograph is corrected against the irradiation imprint recorded by its own background using a kriging interpolation method, thus allowing reliable optical density measurements directly on the corrected X-ray image. This digital detrending (DD) method was validated using skeletal bulk density measurements and computerized tomography (CT). Coral densitometry using DD corrected X-radiographs does not require the destruction of the coral sample and provides high-resolution measurements. Since DD does not require extra aluminium standards to correct X-radiographs, this method optimizes the working space available on the X-ray image. Moreover, it corrects the entire X-radiograph, thus larger samples or numerous samples can be X-rayed at the same time.