  While spatial dose conformity delivered to a target volume has been pushed to
its practical limits with advanced treatment planning and delivery,
investigations in novel temporal dose delivery are unfolding new mechanisms.
Recent advances in ultra-high dose radiotherapy, abbreviated as FLASH, indicate
the potential for reduction in healthy tissue damage while preserving tumor
control. FLASH therapy relies on very high dose rate of > 40Gy/sec with
sub-second temporal beam modulation, taking a seemingly opposite direction from
the conventional paradigm of fractionated therapy. FLASH brings unique
challenges to dosimetry, beam control, and verification, as well as complexity
of radiobiological effective dose through altered tissue response. In this
review, we compare the dosimetric methods capable of operating under high dose
rate environments. Due to excellent dose-rate independence, superior spatial
(~<1 mm) and temporal (~ns) resolution achievable with Cherenkov and
scintillation-based detectors, we show that luminescent detectors have a key
role to play in the development of FLASH-RT, as the field rapidly progresses
towards clinical adaptation. Additionally, we show that the unique ability of
certain luminescence-based methods to provide tumor oxygenation maps in
real-time with submillimeter resolution can elucidate the radiobiological
mechanisms behind the FLASH effect. In particular, such techniques will be
crucial for understanding the role of oxygen in mediating the FLASH effect.
