Medical Physics

Medical physics applies the principles and methods of physics to understand, diagnose and treat human disease. It spans the use of ionising radiation in radiotherapy and nuclear medicine, non-ionising modalities such as ultrasound and magnetic resonance, optical techniques from microscopy to optical coherence tomography, and emerging fields including molecular hyperpolarisation and optical electrophysiology. Key activities include the design and calibration of imaging and treatment equipment, quantitative dosimetry to ensure safe and accurate dose delivery, physics-based modelling for treatment planning and image reconstruction, quality assurance to maintain performance standards, and the integration of advanced computational methods such as machine learning for data analysis. Medical physicists collaborate with clinicians, engineers and biologists to translate fundamental discoveries—ranging from quantum phenomena and wave mechanics to thermodynamics and fluid dynamics—into practical tools that enable precise targeting of tumours, high-contrast visualization of anatomy and function, and minimally invasive therapeutic interventions.

Research from Nature Portfolio

Online in-beam PET has been demonstrated during clinical proton therapy to reconstruct three-dimensional β⁺ activity distributions on the fly. A silicon-photodetector-based system achieved sub-second image updates and verified range accuracy within millimetre thresholds under realistic treatment conditions. An ultra-compact Compton camera has enabled the first multi-colour, volumetric gamma-ray imaging in live mice, resolving distinct radionuclides in three dimensions and opening avenues for novel tracers and quantitative nuclear imaging. Parahydrogen-induced polarisation of ¹³C-labelled metabolites, notably acetate and pyruvate, has reached clinically relevant concentrations and polarisation levels without cryogenic infrastructure. This method produces hyperpolarised substrates within seconds and has been used in preclinical heart studies to measure metabolic flux, demonstrating altered pyruvate-to-lactate exchange rates in disease models.

Medical Physics publication trend

The graph below shows the total number of articles in medical physics across all publications each year (not limited to Nature Index journals).

Technical terms

Dosimetry: The measurement and calculation of absorbed radiation dose in tissue, essential for treatment planning and verification.

Bragg peak: The pronounced maximum in energy deposition by charged particles at a specific depth, exploited in proton and ion therapy.

Gel dosimeter: A polymer or Fricke hydrogel that undergoes a measurable change upon irradiation, allowing three-dimensional dose mapping via MRI or optical CT.

Hyperpolarisation: Techniques that increase nuclear spin population differences by several orders of magnitude to amplify NMR/MRI signals.

Compton camera: An uncollimated gamma-ray imager that reconstructs source distributions by measuring successive Compton scatter events.

Prospective motion correction: Real-time tracking of patient movement during imaging or treatment to adjust system parameters and maintain alignment.

References

1. What Is Medical Physics? And Other Related Questions.
2. Online proton therapy monitoring: clinical test of a Silicon-photodetector-based in-beam PET. Scientific Reports (2018).
3. First demonstration of multi-color 3-D in vivo imaging using ultra-compact Compton camera. Scientific Reports (2017).
4. ParaHydrogen Induced Polarization of 13C carboxylate resonance in acetate and pyruvate. Nature Communications (2015).
5. The 13C hyperpolarized pyruvate generated by ParaHydrogen detects the response of the heart to altered metabolism in real time. Scientific Reports (2018).
6. Spin Hyperpolarization in Modern Magnetic Resonance. Chemical Reviews (2023).
7. Hydrogels for Three-Dimensional Ionizing-Radiation Dosimetry. Gels (2021).
8. Basic Properties of a New Polymer Gel for 3D-Dosimetry at High Dose-Rates Typical for FFF Irradiation Based on Dithiothreitol and Methacrylic Acid (MAGADIT): Sensitivity, Range, Reproducibility, Accuracy, Dose Rate Effect and Impact of Oxygen Scavenger. Polymers (2019).
9. Radiation Dosimetry by Use of Radiosensitive Hydrogels and Polymers: Mechanisms, State-of-the-Art and Perspective from 3D to 4D. Gels (2022).
10. Continuous evaluation of denoising strategies in resting-state fMRI connectivity using fMRIPrep and Nilearn. PLOS Computational Biology (2024).