Principles of diagnostic imaging methods

Basic principles
For more detailed information, see Principle of Magnetic Resonance Tomography .
 * 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.