Radiological Imaging Methods

History, overview, principles

3. LF UK Praha Department of Radiology 2012

D 3

This teaching file is an introduction to the study of radiology and medical imaging methods for medical students.

History of radiology, overview of different contemporary imaging methods, their physical principles and future trends of radiology are presented.

Redaction: Václav Janík, Jan Šprindrich

Discovery of X-rays

Wilhelm Conrad Röntgen

Professor of physics in Würzburg (Germany)

In 1895 he discovered, while experimenting with cathode tubes, a new penetrating radiation and called it X-rays

The historical first X-ray image of the hand of his wife (exposed 25 min!)

Nobel prize for physics in 1901

Note: In Czech and German these rays are called Röntgen rays – RTG rays

X - rays

electromagnetic radiation

short wavelength

- flux of photons -

• penetrating

• nonvisible

• ionizating

E = h. f

f = c / λ

electromagnetic radiation

History of radiology

1895 Röntgen X-rays (rtg) roentgenology

1896 Becquerel natural radioactivity (α, β, γ)

1898 Mme Curie Po, Ra radiology

20. century

1940 F.J.Curie arteficial radioactivity nuclear medicine

1941 technics of IR rays thermography

technics of US ultrasound - therapy

1950 electronics, semiconductors,TV image intensifier

1960 mikroprocessors, computers digital image

1970 ultrasonography

1972 Hounsfield, McCormack CT

1973 Lauterbur principle of MR imaging

1980 digitalisation digital methods, MRI

interventional radiology

1990 informatics PACS, teleradiology

X-ray laboratory in 1900

Rhumkorff´s inductor (high voltage generator), X-ray tube without any shielding, photographic plate

Biologic effects were not known, radioprotection did not exist.

Many pioneers of radiology died on radiation idnuced cancer.

Historical first X-ray tubes introduced by prof. Röntgen

Modified vaccum Crookes tube with cold cathode, anticathode and anode

+

-

Modern X-ray tube - Coolidge tube (since 1918)

Coolidge tube in a protective shield

Vacuum tube with heated cathode filament emitting electrons which collide with the metal of anode, giving rise to the primary beam of X-rays

More than 95% of cinetic energy of electrons is transformed to heat.

Contemporary X-ray radiographic room

Contemporary radiology - 21. century

Radiology and medical imaging is a recognized clinical discipline in all EU countries

Certification in radiology – 5 years

Radiology comprizes nowadays diagnostic as well as interventional procedures

Higher degree of specialisation in Czech Republic: pediatric radiology, interventional radiology, neuroradiology

Related clinical disciplines: nuclear medicine, radiation oncology ( radiotherapy )

Modern trends in radiology

analog imaging digital imaging

morfology function

qualitative evaluation quantitative evaluation

hybrid systems molecular imaging

interventional methods miniinvasivity

ionizing radiation methods without radiation burden

X-rays US IR MRI

radiography

fluoroscopy

CT

ultrasonography thermography MRI

Doppler MRS

Radiodiagnostic methods - overview

Basic principles of imaging methods1. Transmission

S P D

source pacient detector

(X-rays, CT)

μ ≈ λ3 . Zef4

Primary beam of X-rays traverse the patient. In the patient a part of X-rays is absorbed (photoeffect) and the attenuated beam continues to the detector and creates the image. Another part is scattered (Compton´s effect)

The degree of absorption depends on the wavelength and on the effective atomic number of the tissueThe scattered secondary radiation with longer wavelength is propagated in all directions around the patient.

2. Emission

S

P

D

(NM, thermography)

The source of radiation is situated in the patient and radiation is emerging out of the patient in all directions In nuclear medicine a radionuclide is administred in the body and radiations are registered by detectors outside of the body.In thermography, the infrared radiation is emitted from the patient and registered

3. Reflection

S

D

PP

(Ultrasound methods)

The ultrasound probe contains both the source and the detector. Sound waves arasing from the source (UZ probe) are reflected on impedance interfaces of patient´s body back to the detector (UZ probe).

4. Principle of resonance absorption and emission (MRI)

M

PS

D

Radiofrequency pulses are emitted from the source (coil) and irradiate the patient placed in a strong magnetic field. If the resonance condition is installed the atomic nuclei of the human body become excited, then the deexcitation signals are coming back to the detector coil.

Floral radiography

Soft

technique

Thank you for attention !