Millimetre in vivo verification of particle range
In plain words
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.
Precise statement
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.
What would settle it
A patient series in which a verification method and an independent ground truth agree to within 1 mm on the distal range.
Status in the literature
Unverified note
Prompt-gamma timing and slit cameras reached a few mm in patients by 2024; $1\,\mathrm{mm}$ per field remained out of reach.