{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"13bd1f3e6f66e0ce3adc9bac45bee97f7800cfc1be3165cf5fde9364c6e2dc8a","created":"2026-10-03T07:18:06Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"cdddf5568f170d8a1b6c5d160d1bcd312ca41d678f8d906b04b4c6bb513505a7","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"med.ion-therapy.in-vivo-range","kind":"well-posed","literature_status":"partially-resolved","n":"1","parents":[],"plain":"Doctors cannot see where the particles actually stop inside the patient, so they treat with extra margin. A reliable way to measure the stopping point during treatment is missing.","posed_since":"2003","precise":"Achieve in vivo verification of the distal beam range to a standard deviation of 1 mm or better, per treatment field, in soft tissue and across tissue interfaces, at clinical dose levels. Candidate signals: prompt gamma emission at 3 to 7 MeV, positron-emitter activation (C-11, O-15, N-13), ionoacoustic pressure pulses, and charged secondary tracking. An answer is a demonstrated method with measured accuracy and precision in patients.","problem_ref":null,"references":"","settled_by":"A patient series in which a verification method and an independent ground truth agree to within 1 mm on the distal range.","status_note":"Prompt-gamma timing and slit cameras reached a few mm in patients by 2024; $1\\,\\mathrm{mm}$ per field remained out of reach.","title":"Millimetre in vivo verification of particle range","topic_ref":"783c95cea555c72f61498fd08fa3ced7be4a4b07d67abcd2e5bc27204e6bdab5"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"7f80c6d4742d104552034338b19dd043d8f073a4b8c7927f38587ab33b38b074","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"6cece6f6e323c86fd52aa710945ccb25b3e398a34f1621fb433067dbbf90d346","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"FciFFRqojEt5KeJeuZWnPIAVl67rNl3_ULwgAslAPv1s7KR2euqxq9vWfhJ6Sz68H9lmYRwAgSn7u5URRK3IBg"},"schema":"pubphys.envelope/1"},"record_hash":"7f80c6d4742d104552034338b19dd043d8f073a4b8c7927f38587ab33b38b074","leaf_index":1690}