Principles of diagnostic imaging methods

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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.
   For more information see Principle of Magnetic Resonance Tomography.

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.

Links

External links

• Images at atlas.mudr.org sorted by modality
• Lukáš Mikšík: Radiology

References

• Jaromír Šrámek: Unconventional alternatives to mammography (presentation, 2010)

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