{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"557b8bebe5c14c3340f9cbce8e84c48244e3d22f6fc597b4347cd7bda832a949","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":["ai:gpt-5.5"],"kind":"seed"},"parents":["930874c36a968325068f34df74a2c7b9308fb8335791479d0f0816a4a8ac6a4e","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"a88bc52677e3fc4e389866782d5e0ca105ebdb62c47898feee389f6e3948f464","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":["ai:gpt-5.5"],"external_id":"med.pcct.k-edge-sensitivity","kind":"well-posed","literature_status":"open","n":"2","parents":[],"plain":"Elements like iodine and gadolinium absorb x-rays sharply above one energy, which lets a spectral scanner tell them apart. How little of an element can be detected is not pinned down.","posed_since":"2008","precise":"Determine the minimum detectable concentration of K-edge elements (iodine at 33.2 keV, gadolinium at 50.2 keV, and higher-$Z$ labels such as tantalum, gold and bismuth) in a 30 cm diameter water phantom at clinical dose, as a function of detector energy resolution, bin count and photon flux. An answer is a detection-limit formula in mg per cm^3 with its dependence on these quantities.","problem_ref":"930874c36a968325068f34df74a2c7b9308fb8335791479d0f0816a4a8ac6a4e","references":"","settled_by":"Phantom measurements across concentration and dose compared against a task-based detectability calculation using the measured detector response.","status_note":"","title":"Detection limit for K-edge contrast agents","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"0ee4e89a336f0f573e027d4059ade52b253b1e774c9c4a86af6362d7979c8c8d","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"84e2099bca55c9c41eb5be5a9a48fdb4b2b6dd585f489838864f8694b1fa932c","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"gm6cueQ6BZbogqxKmcCGqybORy-E8Y5hLsWbhFIQq_Uel0yY8MhI2dSfbyT95L1aJT_VX14I5mHUFtK1MfXjCg"},"schema":"pubphys.envelope/1"},"record_hash":"0ee4e89a336f0f573e027d4059ade52b253b1e774c9c4a86af6362d7979c8c8d","leaf_index":3480}