The primary objective of this study is to compare the irradiation between Cone Beam and CT of the petrous bone.

The primary endpoint is the measurement of equivalent doses per organ of interest (eyes, ears, thyroid and external genitalia).

The investigators have set up a prospective monocentric study. The investigators will measure irradiation of these different organs using nanodots placed on the patient during imaging.

The results of these measurements will be compared between Cone Beam (performed in the Besançon University Hospital ENT department for cochlear implant position checks) and CT (all indications combined).

Inclusion Criteria:

• Adult or child patients of any gender and any age, including the pediatric population, receiving a CT scan of the petrous bone performed at Besançon University Hospital and prescribed in the Besançon University Hospital ENT department, or receiving a CBCT as part of an intraoperative check of cochlear implant position.
• Women menopausal for at least 24 months, surgically sterilized, or, for women of childbearing age, using an effective contraceptive method (oral contraceptives, contraceptive injections, intra-uterine devices, double-barrier method, contraceptive patches).
• Subject's non-opposition to study participation
• Affiliation with a French social security scheme or beneficiary of such a scheme.

Exclusion criteria are :

• Legal incapacity or limited legal capacity
• Subject unlikely to cooperate with the study and/or poor cooperation anticipated by the investigator.

Patients are recruited during a consultation in the ENT department, either as part of a pre-cochlear implant assessment, or as part of a prescription for a CT scan of the petrous bone by the Besançon University Hospital ENT department department to be carried out at Besançon University Hospital.