{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"69d799fd20f25e0793e7bd6e5e489715e2da950da957e8bd68a94bbeaba4309d","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["b9ac9f44652a99795b9547ff2d404bfa7120d276ceb5cc641d745b4bcd729558","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"2053db9701fd1d85abca305e2bdb2c8b272af010a3cb97eb162bfed0ac800559","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"med.pet.timing-limit","kind":"well-posed","literature_status":"open","n":"2","parents":[],"plain":"Today the best clinical scanners time the two photons to about two hundred trillionths of a second (picoseconds). Getting to ten would place each emission directly, with no image reconstruction.","posed_since":"2017","precise":"Determine whether a coincidence time resolution of 10 ps full width at half maximum is attainable in a detector of sufficient stopping power for 511 keV photons, which corresponds to a position uncertainty of about 1.5 mm along the line of response. Required chain: photon production statistics and rise time, light transport, photodetector transit-time spread, and electronics jitter. An answer is a demonstrated detector pair or a proof that a chain element forbids it.","problem_ref":"b9ac9f44652a99795b9547ff2d404bfa7120d276ceb5cc641d745b4bcd729558","references":"","settled_by":"A bench measurement of 10 ps coincidence resolution between two detectors with 511 keV efficiency comparable to clinical crystals.","status_note":"Laboratory detector pairs reached the tens of ps range by the mid 2020s; clinical systems were at about 180 to 230 ps.","title":"Is 10 ps coincidence time resolution reachable?","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"cbba385a607ba810768a4d9df9eda3819f6a7106729db16075817aab7023bc2d","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"380b6fba1284c44e33b299c9356a0213743fc80d857c265f952f8c4f79e0b1ea","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"0hj8CxKd2VBHRSHyFb8OGTWuBaJ3ufHmnfMRaHeSp2aKE6BJakQXgtSLiG1BSga4c6_d8nPCwzsjF_u_JIbADw"},"schema":"pubphys.envelope/1"},"record_hash":"cbba385a607ba810768a4d9df9eda3819f6a7106729db16075817aab7023bc2d","leaf_index":3482}