Exploratory Study Evaluating the Relevance of [68Ga]Ga-FAPI-46 for Staging and Identifying Progressing Patients With Transthyretin Cardiac Amyloidosis

Inclusion Criteria: * Men or women ≥ 18 years * Definite ATTR-CM diagnosis based on the 2021 ESC expert consensus * Written and signed informed consent (obtained on the screening day at the latest and before any investigation) * Affiliation with French social security system or beneficiary from such system * Women must meet one of the following criteria at the time of inclusion: * present a negative pregnancy test (blood test) before the injection of \[68Ga\]Ga-FAPI-46 and use highly1 effective contraceptive measures for a duration of 6 months after the PET with \[68Ga\]Ga-FAPI-46; * or be post-menopausal (aged over 50 with amenorrhea for at least 12 months after stopping all exogenous hormone treatments); * or (if under 50 years of age) have been in amenorrhea for at least 12 months after stopping exogenous hormone treatments and with luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels corresponding to post-menopausal levels; * or have undergone irreversible surgical sterilization by hysterectomy, bilateral oophorectomy or bilateral salpingectomy (this operation must be documented); * Male patients will be required to use male contraception (condoms) for a duration of 3 months after the PET; * Women partners will be required to use an acceptable2 contraceptive measure (as they will not receive the trial drug) for a duration of 3 months after the PET; * Male partners will be required to use male contraception (condoms) for a duration of 6 months after the PET. Exclusion Criteria: * History of Myocardial infarction or myocarditis * Severe aortic stenosis * Current or prior participation in a clinical trial evaluating a TTR-targeted gene-silencing therapy (TTR= transthyretin) or an amyloid-depleting treatment for cardiac transthyretin amyloidosis (ATTR-CM). * Any psychological, familial, sociological or geographical condition potentially hampering compliance with the study protocol and follow-up schedule * Women who are pregnant or breastfeeding. A serum pregnancy test will be performed at the start of the study and within 48 hours prior to PET for all female subjects of childbearing potential. * Patient under guardianship or trusteeship. * Patient under judicial protection. * Patient unable to understand spoken or written French * Known hypersensitivity to gallium-68, to any excipient or derivative