Medical and Radiation Physics
Physics applied to medicine: how radiation acts on living tissue, and how beams and fields image and treat the body.
arXiv: physics.med-ph
12 topics
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Boron neutron capture therapy physics
4 problemsA drug carrying boron is loaded into tumour cells, and the patient is then exposed to slow neutrons, which split boron nuclei into two short-range charged fragments that destroy only the cell they are in. The difficulty is knowing how much boron is where, and what dose the mixed radiation actually delivers.
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Diffusion MRI of tissue microstructure
4 problemsMagnetic resonance scanners can track how water molecules wander inside tissue, and the wandering is slowed by cell walls and fibres far smaller than an image pixel. The open question is how much of the hidden microscopic structure can actually be read back from that signal.
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Reference dosimetry in nonstandard beams
6 problemsKnowing the dose a patient receives rests on calibrating detectors in standard conditions. Modern beams are small, pulsed extremely hard, or operate inside strong magnets, and the standard calibration chain breaks down there.
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FLASH ultra-high dose-rate radiotherapy
6 problemsDelivering a whole radiation treatment in less than a tenth of a second appears to damage healthy tissue much less than the same dose given over minutes, while killing tumours just as well. No one knows why this happens.
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Sound waves can be focused deep inside the body to heat tissue, open the barrier protecting the brain, or change nerve activity, without any cut. How the sound actually acts on cells and how to aim it through bone are open questions.
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Proton and heavy-ion beam therapy physics
6 problemsCharged particles stop at a controllable depth, concentrating dose in the tumour and sparing tissue beyond it. Two things remain uncertain: exactly where they stop in a patient, and how much more biological damage they do than x-rays.
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Health risk of low-dose ionizing radiation
6 problemsLarge radiation doses clearly cause cancer, but the risk from doses comparable to a few CT scans is too small to measure directly. Whether risk stays proportional to dose all the way down is disputed.
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Radiation deposits energy in microscopic bursts along the path of each particle, and the pattern of those bursts, which heavy-element nanoparticles inside a cell can change locally, decides how much biological damage results. Predicting damage from the pattern is still not possible from first principles.
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Photon-counting and spectral x-ray imaging
5 problemsNew x-ray detectors count individual photons and measure the energy of each one, instead of adding up the total energy. This promises sharper images at lower dose, but the counting goes wrong when photons arrive quickly or share their charge between pixels.
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Time-of-flight positron emission tomography
5 problemsA PET scanner locates a radioactive tracer by catching the two photons it emits in opposite directions. Measuring the tiny difference in their arrival times narrows down where the emission happened; pushing that timing to a few trillionths of a second would let the scanner form an image directly.
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Radiopharmaceutical therapy dosimetry
6 problemsA radioactive drug is injected and carried by the bloodstream to tumour cells, where it irradiates them from inside. Unlike external beam treatment, nobody knows accurately what dose each organ and tumour receives.
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If radiation is delivered in a comb of narrow beams separated by unirradiated gaps, healthy tissue tolerates doses that would otherwise destroy it, while tumours still respond. The reason is not understood and the best comb spacing is unknown.