General introduction- fundamental principles

X ray & CT

General introduction- fundamental principles

X ray & CT

Radiology Dept. 1st Hospi. of Peking University

唐光健

Radiology Dept. 1st Hospi. of Peking University

唐光健

Questions to think of with the lecture

What is X ray? What kinds of the features of it are useful or harmful?

What are the two steps of X ray imaging?

How is the grey scale of bone, muscle and air in the X ray film?

What is the main difference between the CT imaging and the image of X ray film?

What are same and what are different between the processes of CT imaging and imaging of X ray projection?

Is the meaning of a CT axial imaging and a section of a body specimen in same location identical?

What is X ray? What kinds of the features of it are useful or harmful?

What are the two steps of X ray imaging?

How is the grey scale of bone, muscle and air in the X ray film?

What is the main difference between the CT imaging and the image of X ray film?

What are same and what are different between the processes of CT imaging and imaging of X ray projection?

Is the meaning of a CT axial imaging and a section of a body specimen in same location identical?

Black box?

Wilhelm C RöntgenWilhelm C Röntgen

Black box?Black box?

Wilhelm C RöntgenWilhelm C Röntgen

Generation and features of X ray

High speeding electrons Anode target sudden slow down

special X ray – sequence spectrum narrow

consecutive X ray – sequence spectrum wide

High speeding electrons Anode target sudden slow down

special X ray – sequence spectrum narrow

consecutive X ray – sequence spectrum wide

X ray X ray

e

e

special X ray – sequence spectrum narrow

consecutive X ray – sequence spectrum wide

special X ray – sequence spectrum narrow

consecutive X ray – sequence spectrum wide

electromagnetic waves -ionizing radiation -wave length of medical use:

0.08 ~ 0.71Å -feature of wave; feature of particle

Features-Effects

electromagnetic waves -ionizing radiation -wave length of medical use:

0.08 ~ 0.71Å -feature of wave; feature of particle

Features-Effects

Physical effect

Chemical effect

Biotic effect

Physical effect

Chemical effect

Biotic effect

Generation and features of X ray

electromagnetic waves -ionizing radiation -wave length of medical use:

0.08 ~ 0.71Å -feature of wave; feature of particle

Features-Effects

electromagnetic waves -ionizing radiation -wave length of medical use:

0.08 ~ 0.71Å -feature of wave; feature of particle

Features-Effects

Physical effect

Chemical effect

Biotic effect

Physical effect

Chemical effect

Biotic effect

Generation and features of X ray

Penetrability Fluorescent effect Thermal effect Ionizing effect interference ， diffraction, reflection, refraction

Penetrability Fluorescent effect Thermal effect Ionizing effect interference ， diffraction, reflection, refraction

Features-EffectsFeatures-Effects Physical effect

Chemical effect

Biotic effect

Physical effect

Chemical effect

Biotic effect

Generation and features of X ray

Penetrability Fluorescent effect Thermal effect Ionizing effect interference ， diffraction, reflection, refraction

Penetrability Fluorescent effect Thermal effect Ionizing effect interference ， diffraction, reflection, refraction

-be able to penetrate ma. of dif. density while attenuated -be able to penetrate ma. of dif. density while attenuated

I0I0 IIµµ

ll

I = I0 · e- µlI = I0 · e- µl

Features-EffectsFeatures-Effects Physical effect

Chemical effect

Biotic effect

Physical effect

Chemical effect

Biotic effect

Generation and features of X ray

Penetrability Fluorescent effect Thermal effect Ionizing effect interference ， diffraction, reflection, refraction

Penetrability Fluorescent effect Thermal effect Ionizing effect interference ， diffraction, reflection, refraction

-making some compounds fluoresce -Fluoroscopy, image intensifier

-making some compounds fluoresce -Fluoroscopy, image intensifier

Features-EffectsFeatures-Effects Physical effect

Chemical effect

Biotic effect

Physical effect

Chemical effect

Biotic effect

Generation and features of X ray

Penetrability Fluorescent effect Thermal effect Ionizing effect interference ， diffraction, reflection, refraction

Penetrability Fluorescent effect Thermal effect Ionizing effect interference ， diffraction, reflection, refraction

-making some compounds fluoresce -Fluoroscopy, image intensifier

-making some compounds fluoresce -Fluoroscopy, image intensifier

Features-EffectsFeatures-Effects Physical effect

Chemical effect

Biotic effect

Physical effect

Chemical effect

Biotic effect

Generation and features of X ray

Penetrability Fluorescent effect Thermal effect Ionizing effect interference ， diffraction, reflection, refraction

Penetrability Fluorescent effect Thermal effect Ionizing effect interference ， diffraction, reflection, refraction

-Subject absorb the energy of X ray ionized ionized voltage -ionizing cell auto-exposure

X ray detector

-Subject absorb the energy of X ray ionized ionized voltage -ionizing cell auto-exposure

X ray detector

Features-EffectsFeatures-Effects Physical effect

Chemical effect

Biotic effect

Physical effect

Chemical effect

Biotic effect

Generation and features of X ray

Penetrability Fluorescent effect Thermal effect Ionizing effect interference ， diffraction, reflection, refraction

Penetrability Fluorescent effect Thermal effect Ionizing effect interference ， diffraction, reflection, refraction

- penumbra, interferential signal image blued- penumbra, interferential signal image blued

Features-EffectsFeatures-Effects Physical effect

Chemical effect

Biotic effect

Physical effect

Chemical effect

Biotic effect

Generation and features of X ray

sensitization effect

coloration effect

fundament of X ray filming

sensitization effect

coloration effect

fundament of X ray filming

Features-EffectsFeatures-Effects Physical effect

Chemical effect

Biotic effect

Physical effect

Chemical effect

Biotic effect

Generation and features of X ray

radiated tissue cells restrained, damaged, necrosingX ray protection

radiated tissue cells restrained, damaged, necrosingX ray protection

X ray Imaging

X ray penetrate the subject （ body) while attenuated

attenuate signal recorded by the accepting medium

X ray penetrate the subject （ body) while attenuated

attenuate signal recorded by the accepting medium

X ray Imaging

X ray penetrate the subject （ body) while attenuated

attenuate signal recorded by the accepting medium

X ray penetrate the subject （ body) while attenuated

attenuate signal recorded by the accepting medium

I0I0 IIµ1µ1

l1l1

I = I0 · e- µ1l1 · e- µ2l2 · e- µ3l3 · e- µ4l4 I = I0 · e- µ1l1 · e- µ2l2 · e- µ3l3 · e- µ4l4

µ2µ2

l2l2

µ3µ3

l3l3

µ4µ4

l4l4

X ray Imaging

X ray penetrate the subject （ body) while attenuated

attenuate signal recorded by the accepting medium

X ray penetrate the subject （ body) while attenuated

attenuate signal recorded by the accepting medium

getting special distribution o

f different density

overlapping of anterio-post

erior images

getting special distribution o

f different density

overlapping of anterio-post

erior images

X ray Imaging

X ray penetrate the subject （ body) while attenuated

attenuate signal recorded by the accepting medium

X ray penetrate the subject （ body) while attenuated

attenuate signal recorded by the accepting medium

film-silver bromide decomposed positive correlation with

dosage of X raynegative correlation

with degree of attenuation

film-silver bromide decomposed positive correlation with

dosage of X raynegative correlation

with degree of attenuation

flu. screen detectors flu. screen detectors

X ray Imaging

X ray penetrate the subject （ body) while attenuatedattenuate signal recorded by the accepting medium

X ray penetrate the subject （ body) while attenuatedattenuate signal recorded by the accepting medium

grey of spots thickness & density o∽f the mat. in the path way of X ray beam distribution of the spots anatomic ∽ form in the path way of X ray beam difference between the sports - contrastimage

natural contrastartificial contrast

grey of spots thickness & density o∽f the mat. in the path way of X ray beam distribution of the spots anatomic ∽ form in the path way of X ray beam difference between the sports - contrastimage

natural contrastartificial contrast

X ray Imaging

X ray penetrate the subject （ body) while attenuatedattenuate signal recorded by the accepting medium

X ray penetrate the subject （ body) while attenuatedattenuate signal recorded by the accepting medium

grey of spots thickness & density o∽f the mat. in the path way of X ray beam distribution of the spots anatomic ∽ form in the path way of X ray beam difference between the sports - contrastimage

natural contrastartificial contrast

grey of spots thickness & density o∽f the mat. in the path way of X ray beam distribution of the spots anatomic ∽ form in the path way of X ray beam difference between the sports - contrastimage

natural contrastartificial contrast

X ray Imaging

X ray penetrate the subject （ body) while attenuatedattenuate signal recorded by the accepting medium

X ray penetrate the subject （ body) while attenuatedattenuate signal recorded by the accepting medium

grey of spots thickness & density o∽f the mat. in the path way of X ray beam distribution of the spots anatomic ∽ form in the path way of X ray beam difference between the sports - contrastimage

natural contrastartificial contrast

grey of spots thickness & density o∽f the mat. in the path way of X ray beam distribution of the spots anatomic ∽ form in the path way of X ray beam difference between the sports - contrastimage

natural contrastartificial contrast

X ray Imaging

X ray equipment

X ray source X ray tube High voltage generator

X ray imaging devices X ray film / image intensifier / plate detector

X ray mechanical device

exam table frame……

X ray source X ray tube High voltage generator

X ray imaging devices X ray film / image intensifier / plate detector

X ray mechanical device

exam table frame……

X ray tube filament - cathode anode target tube shell

X ray tube filament - cathode anode target tube shell

X ray equipment

X ray equipment

X ray tube filament - cathode anode target tube shell

X ray tube filament - cathode anode target tube shell

Protection from X ray

X ray protectionCancel X ray exam unnecessary

Reduce radiation dosage

Distance from X ray source

Protective device

X ray protectionCancel X ray exam unnecessary

Reduce radiation dosage

Distance from X ray source

Protective device

Principles of imaging diagnosis

familiar with imaging methods and body position

familiar with the normal imaging anatomy and variations

sequential observation

imaging manifestations and relationship with neighboring structures of the lesion

clinical and laboratory materials

understanding the meaning and limitations of the imaging methods

familiar with imaging methods and body position

familiar with the normal imaging anatomy and variations

sequential observation

imaging manifestations and relationship with neighboring structures of the lesion

clinical and laboratory materials

understanding the meaning and limitations of the imaging methods

fundamental principlesof CT

fundamental principlesof CT

CT-Computerized Tomography

real tomography ， without any overlapping

CT-Computerized Tomography

real tomography ， without any overlapping

fundamental principles of CT

I0 Iµ1µ1

l1l1

I = I0 · e- µ1l1 · e- µ2l2 · e- µ3l3 · e- µ4l4 I = I0 · e- µ1l1 · e- µ2l2 · e- µ3l3 · e- µ4l4

µ2µ2

l2l2

µ3µ3

l3l3

µ4µ4

l4l4

I0 Iµ1µ1

l1l1

I = I0 · e- µ1l1 · e- µ2l2 · e- µ3l3 · e- µ4l4 I = I0 · e- µ1l1 · e- µ2l2 · e- µ3l3 · e- µ4l4

µ2µ2

l2l2

µ3µ3

l3l3

µ4µ4

l4l4

l1 = l1 = l1 = l1 = 1l1 = l1 = l1 = l1 = 1

I = I0 · e- (µ1+ µ2 + µ3 + µ 4) · 1I = I0 · e- (µ1+ µ2 + µ3 + µ 4) · 1

fundamental principles of CT

Godfrey HounsfieldGodfrey Hounsfield First laboratory CT scan

ner 1968First laboratory CT scan

ner 1968

fundamental princ. of CT

fundamental princ. of CT

First clinical head CT scanner

Atkinson Morley‘hosp.， London

First clinical head CT scanner

Atkinson Morley‘hosp.， London

fundamental principles of CT

measurement measurement

fundamental principles of CT

DAS － data acquisition system -detector -bumper

-integrator -amplifier -A/D converter

DAS － data acquisition system -detector -bumper

-integrator -amplifier -A/D converter

detector detector

fundamental principles of CT

measurement measurement

Reconstruction Reconstruction

fundamental principles of CT

backprojective method Iterative method Factorial method

Fourier methodFilt. backprojective method

backprojective method Iterative method Factorial method

Fourier methodFilt. backprojective method

fundamental principles of CT

Reconstruction Reconstruction

Filt. function(Kernol)

High filt.(bone algorithm)low filt.(soft tissue algorithm)

Filt. function(Kernol)

High filt.(bone algorithm)low filt.(soft tissue algorithm)

fundamental principles of CT

Reconstruction Reconstruction

Filt. function(Kernol)

High filt.(bone algorithm)low filt.(soft tissue algorithm)

Filt. function(Kernol)

High filt.(bone algorithm)low filt.(soft tissue algorithm)

fundamental principles of CT

Reconstruction Reconstruction

[(μobj.- μwater)/μwater]×1000 [(μobj.- μwater)/μwater]×1000

CT value -relative magnitude to watermay be used qualitatively

but not quantitively

CT value -relative magnitude to watermay be used qualitatively

but not quantitively

fundamental principles of CT

Reconstruction Reconstruction

image display image display

fundamental principles of CT

200/30=7HU

muscle 50HU- fat -50HU=100 ~13 grey scale

200/30=7HU

muscle 50HU- fat -50HU=100 ~13 grey scale

1000/30=33HU

muscle 50HU- fat -50HU=100 ~3 gray scale

1000/30=33HU

muscle 50HU- fat -50HU=100 ~3 gray scale

image display image display

ability of identify grey scale

eyes： 24~30 CT： 2000

ability of identify grey scale

eyes： 24~30 CT： 2000

fundamental principles of CT

Voxel and pixel

voxel – 3D, pixel – 2D

CT value of a voxel represent all messages of the elements in the voxel

Voxel and pixel

voxel – 3D, pixel – 2D

CT value of a voxel represent all messages of the elements in the voxel

fundamental principles of CT

image display image display

partial volume effectpartial volume effect

fundamental principles of CT

image display image display

enhancement CT high density contrast agent injected into veinintro-vascular/-tissue （ extracellular space) CT scan density contrast

hypersensitivenessnephrotoxitity

enhancement CT high density contrast agent injected into veinintro-vascular/-tissue （ extracellular space) CT scan density contrast

hypersensitivenessnephrotoxitity

fundamental principles of CT

enhancement CT high density contrast agent injected into veinintro-vascular/-tissue （ extracellular space) CT scan density contrast

hypersensitivenessnephrotoxitity

enhancement CT high density contrast agent injected into veinintro-vascular/-tissue （ extracellular space) CT scan density contrast

hypersensitivenessnephrotoxitity

fundamental principles of CT

enhancement CT high density contrast agent injected into veinintro-vascular/-tissue （ extracellular space) CT scan density contrast

hypersensitivenessnephrotoxitity

enhancement CT high density contrast agent injected into veinintro-vascular/-tissue （ extracellular space) CT scan density contrast

hypersensitivenessnephrotoxitity

fundamental principles of CT

IndicationsNo absolute contraindication, suitable for emergency and serious cases exam

Single imaging factor ， image interpretation easily ，anatomy clear and detailed

deformation 、 infection 、 trauma 、 neoplasm…

LimitationsLow soft tissue resolution ， difficult to detect lesion with small density difference from neighbor structure

Low sensitivity for the lesion with slight gross change

Contrast agent using

IndicationsNo absolute contraindication, suitable for emergency and serious cases exam

Single imaging factor ， image interpretation easily ，anatomy clear and detailed

deformation 、 infection 、 trauma 、 neoplasm…

LimitationsLow soft tissue resolution ， difficult to detect lesion with small density difference from neighbor structure

Low sensitivity for the lesion with slight gross change

Contrast agent using

fundamental principles of CT

Questions to think of with the lecture

What is X ray? What kinds of the features of it are useful or harmful?

What are the two steps of X ray imaging?

How is the grey scale of bone, muscle and air in the X ray film?

What is the main difference between the CT imaging and the image of X ray film?

What are same and what are different between the processes of CT imaging and imaging of X ray projection?

Is the meaning of a CT axial imaging and a section of a body specimen in same location identical?

What is X ray? What kinds of the features of it are useful or harmful?

What are the two steps of X ray imaging?

How is the grey scale of bone, muscle and air in the X ray film?

What is the main difference between the CT imaging and the image of X ray film?

What are same and what are different between the processes of CT imaging and imaging of X ray projection?

Is the meaning of a CT axial imaging and a section of a body specimen in same location identical?