While other methods image anatomy, nuclear medicine images . In Positron Emission Tomography (PET) , a radioactive tracer is injected into the patient. As the tracer decays, it emits a positron, which quickly meets an electron. This results in an annihilation event , producing two gamma rays traveling in opposite directions. Sensors detect these coincident photons to pinpoint metabolic "hotspots," such as tumors or brain activity. Conclusion
Unlike X-ray or MRI, uses mechanical energy rather than electromagnetic radiation. It relies on the piezoelectric effect , where crystals in a transducer convert electrical energy into high-frequency sound waves. These waves reflect off internal boundaries (acoustic impedance). By measuring the time-of-flight of the echoes and applying the Doppler Effect , physics allows us to visualize not just static anatomy, but the real-time velocity of blood flow. Nuclear Medicine: PET and SPECT The Essential Physics of Medical Imaging
evolves this concept by rotating the X-ray source around the patient. This uses the Radon transform , a mathematical principle that reconstructs 2D projections into 3D cross-sectional slices, allowing for much higher spatial resolution and the ability to distinguish between varying densities of soft tissue. Nuclear Magnetic Resonance: MRI While other methods image anatomy, nuclear medicine images
Medical imaging is a cornerstone of modern healthcare, transforming the human body from an opaque mystery into a transparent landscape for diagnosis. At its core, every imaging modality—whether X-ray, MRI, or Ultrasound—is an application of fundamental physics. By manipulating the interactions between matter and energy, clinicians can visualize internal structures without invasive surgery. Ionizing Radiation: X-ray and CT This results in an annihilation event , producing
The oldest and most common form of imaging relies on the and Compton scattering . In traditional X-rays, high-energy photons are fired through the body; dense structures like bone absorb more photons (attenuation), while soft tissues allow more to pass through to the detector.