Principles of diagnostic imaging methods

Basic principles

 * The transmission principle: a source of radiation from one side of the patient, on the other side a detector that detects the weakening of the radiation. Uses X-ray, CT.
 * Emission principle: the radiation source is inside the patient, the detector is outside the patient. Used by nuclear medicine, thermography.
 * The reflective principle: source outside the patient, reflected waves are detected. Uses UZ.
 * Principle of resonant absorption and emission. Uses MRI.

Static and dynamic methods

 * Static methods: emphasis on morphology, contrast and spatial resolution.
 * Dynamic methods: emphasis on function, time resolution.

Physical modalities
Diagnostic imaging methods use several different physical modalities to image organs and tissues. The basic methods used in diagnosis include:


 * ionizing radiation, especially X-rays: fluoroscopy, fluoroscopy, CT,
 * behavior of substances in a magnetic field (relaxation time T1, T2 and proton density − PD): MRI,
 * acoustic properties of tissues (acoustic impedance): ultrasonography,
 * radioactive decay of radionuclides with the emission of ionizing radiation (γ radiation): nuclear medicine methods - SPECT, PET,

Other physical modalities are also used at the experimental level. These include, for example:


 * tissue elasticity (Young's modulus of elasticity): elastography,
 * visible light: e.g. laser-CT – breast vascularisation examination, OCT (Optical Coherence Tomography) – eye examination,
 * infrared radiation: thermography, NIRS (Near InfraRed Spectroscopy) tomography,
 * microwaves: microwave tomography - breast examination,
 * electrical impedance: EIT (Electrical Impedance Tomography).

General principles

 * ALARA principle: As Low As Reasonably Achievable − the dose of ionizing radiation should be as low as reasonably achievable.

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