{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"bdd015ae848893c89bf7da7883f5818614bafb96bc1165a1900cdb78e9e1897a","created":"2026-10-03T07:18:07Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"918f29b9b12fd64bc5317ccd6cd5f23fc2596343927e7dd9e73b815872a4d3de","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"med.spatial-fractionation.beam-geometry-scaling","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"Choosing stripe width and gap is currently trial and error. A rule connecting them to tissue type and depth is missing.","posed_since":"2010","precise":"Derive a scaling relation for the therapeutic ratio as a function of beam width w, centre-to-centre spacing s, and depth, including beam broadening by multiple scattering for protons and by scattered photons for x-rays, so that the pattern merges into a uniform field at the target while staying fractionated in normal tissue. An answer is a design rule for w and s with the physical quantities that set them.","problem_ref":null,"references":"","settled_by":"Measured dose profiles at depth combined with tolerance data across several geometries, showing a single relation that predicts the optimum.","status_note":"","title":"Optimal beam width and spacing scaling law","topic_ref":"309568a913eeab83fa370b104ac678cba3936514b3451a97889575e821f58ffd"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"e897061762472116fa177bf27f6d595a8cf47a2614af260e2aca5c295f29f479","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"7090cc4c84aa734de33543c83011a2c2499a87d85ecfbc251646ddf35e517e63","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"8nkhxycc185oVlBeAY2zE78OdGWHv0diaQX4PsV568MKlckvqJ5HcK6CeLJpJhVMI5F1aIZR49C9LEE3l0bfCg"},"schema":"pubphys.envelope/1"},"record_hash":"e897061762472116fa177bf27f6d595a8cf47a2614af260e2aca5c295f29f479","leaf_index":1725}