{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"6b4840c515ae201064444e63bb4a91215dd09d98857daa92aef25398c5445341","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["8923634a80ac2c692e25b4672531dbb73514b1b18f2d33f0880b53eff3a4dcc5","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"d7013e31cb5209ec6110409b4dfb51f1ab38dddf9fd1d66e85b7a4bed7ac90af","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"classification","assisted_by":[],"external_id":"med.ion-therapy.optimal-ion","kind":"well-posed","literature_status":"open","n":"2","parents":[],"plain":"Beyond protons, beams of helium, carbon, oxygen and neon are possible, each with a different balance of sharpness, biological effect and unwanted fragments. Which one is best for which tumour is unsettled.","posed_since":"1975","precise":"Rank ion species by atomic number Z from 1 to 10 against the combined criteria of lateral and distal penumbra, dose-averaged LET in target versus normal tissue, fragmentation tail dose beyond the Bragg peak, and oxygen enhancement ratio in hypoxic targets. An answer is a classification of tumour and site classes to the preferred ion, with the physics criteria that decide each case.","problem_ref":"8923634a80ac2c692e25b4672531dbb73514b1b18f2d33f0880b53eff3a4dcc5","references":"","settled_by":"Comparative planning plus measured fragmentation yields and in vivo effectiveness for each species on a common endpoint set.","status_note":"Helium returned to clinical use at HIT Heidelberg in 2021, after the Berkeley helium programme of 1957 to 1992; oxygen and multi-ion schemes were under study in 2025 without a settled ranking.","title":"Which ion species is optimal for therapy?","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"fe65fc2259f18a935e02cf4587828dc992462af2a7696f5c933409700707ced8","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"98c006465d056c610f4796c375ef033cda9a4a61ea13ae47995bdf2babf25c16","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"JIUBsw-vrF3aqZlid_4dwsmzb4rrw9YP4cR30cTtgMTOIz7cFZYdmdiRIwQmP6oBBKCa_MQEcclXPZOVZoIFCQ"},"schema":"pubphys.envelope/1"},"record_hash":"fe65fc2259f18a935e02cf4587828dc992462af2a7696f5c933409700707ced8","leaf_index":3474}