Crystalline Exposition During Pediatric Cranial CT Imaging

Eye's lens radiosensitivity represents an important subject of investigation in radiology. Indeed, eye's lens is recognised as one of the most radiosensitive organs in human body.[1,2] Radiation induced cataracts represent a determining effect of ionising radiations and has been widely studied. "International Commission for Radiological Protection" has evaluated cataract appearance threshold at 15 Gy in 1977 ",[3] then at 8 Gy [4] and 5 Gy in 2007.[5] Finally, in 2011 new studies gave rise to a new limit of appearance of 0.5 Gy. Eye's lens radiosensitivity seems to have been underestimated for several years and so there is a significant improvement to be made in radioprotection in order to protect to the best of the investigator's ability both patient and manipulator. This was also confirmed by the Directive EURATOM 2013/59 (which is in the process of being transposed in French legislation)[6] that reduces legal limit dose delivered to eye's lens from 150mSv to20mSv, for categories A workers.

This study is performed on 4 sequential groups, of ten patients, whereby one control group without ocular protection added. Other groups benefit either from a bismuth ocular protection, from a dose modulation applied to the eye's lens, or from both techniques associated. For each group, experiment is then focused on dose received by the eye's lens (measured using TLD detectors) as well as on Image quality obtained. Currently, there is no recommendation regarding lens protection for patient who benefit of a head tomodensitometry. Some practices are already used routinely but without a critical analysis of a comparison of their respective benefits.

Inclusion criteria

• Children between 5 and 16 yrs old
• Indication of cerebral CT with or without contrast regardless to indication or exam specificity
• Patients beneficiary or affiliated to health system security
• Oral consent for data processing from the child and his/her representative of parental authority

Exclusion criteria

• Children anxious or agitated
• Sedated patients or patients under general anaesthesia
• Impossibility to position the skull on the orbito-meatal plane (intubation for example)
• Patients under legal protection