X-ray imaging is still one of the most important diagnostic methods used in medicine. It provides mainly morphological (anatomical) information - but may also provide some physiological (functional) information.

1. DR.VISHNU MOHAN

2. List of diagnostic imagingList of diagnostic imaging
studiesstudies
 Plain x-raysPlain x-rays
 CT scanCT scan
 MRIMRI
 Nuclear imagingNuclear imaging
 UltrasoundUltrasound
 MammographyMammography
 AngiographyAngiography
 FluoroscopyFluoroscopy

3. X-Ray Imaging
X-ray imaging is still one of the most
important diagnostic methods used in
medicine. It provides mainly morphological
(anatomical) information - but may also
provide some physiological (functional)
information.

4. What are x-rays?
 No massNo mass
 No chargeNo charge
 EnergyEnergy

5. Basic x-ray physicsBasic x-ray physics
 X-rays: a form of electromagnetic energyX-rays: a form of electromagnetic energy
 Travel at the speed of lightTravel at the speed of light
 Electromagnetic spectrumElectromagnetic spectrum
 Gamma RaysGamma Rays X-raysX-rays
 Visible lightVisible light Infrared lightInfrared light
 MicrowavesMicrowaves RadarRadar
 Radio wavesRadio waves

6.  An X-ray machine is basically
like a camera. It uses X-
rays to expose the film, instead
of visible light.
X-rays are similar to light in
that they are electromagnetic
waves, but they are more
energetic so they can penetrate
many materials to varying
degrees. When the X-rays hit
the film, they expose it just as
light would. Various structures
such as bone, fat, muscle,
tumors and all other masses
absorb X-rays at different
levels

7.  That X-ray light is very strong and is not visible to
human eyes
 X-rays can penetrate objects opaque. X-rays are
commonly used to look at something we cannot see
directly.
 X-rays or Roentgen rays are a form of electromagnetic
radiation
 X-rays are commonly used in the diagnosis of medical
images
 X-rays are a form of ionizing radiation and can be
dangerous.

8. Three things can happenThree things can happen
 X-rays can:X-rays can:
 PassPass all the wayall the way throughthrough the bodythe body
 Be deflected orBe deflected or scatteredscattered
 BeBe absorbedabsorbed

9. X-rays were discovered in 1895
when Wilhelm Conrad
Roentgen observed that a
screen coated with a barium
salt fluoresced when placed
near a cathode ray tube.
Roentgen concluded that a form
of penetrating radiation was
being emitted by the cathode
ray tube and called the
unknown rays, X-rays.

10. First ever X ray in historyFirst ever X ray in history

11. X-rays Passing Through TissueX-rays Passing Through Tissue
 Depends on the energy of the x-ray and theDepends on the energy of the x-ray and the
atomic number of the tissueatomic number of the tissue
 Higher energy x-ray - more likely to passHigher energy x-ray - more likely to pass
throughthrough
 Higher atomic number - more likely to absorbHigher atomic number - more likely to absorb
the x-raythe x-ray

12. How do x-rays passing through theHow do x-rays passing through the
body create an image?body create an image?
 X-rays that pass through the body to the filmX-rays that pass through the body to the film
render the film dark (black)render the film dark (black)
 X-rays that are totally blocked do not reach theX-rays that are totally blocked do not reach the
film and render the film light (white)film and render the film light (white)
 Air = low atomic # = x-rays get through =Air = low atomic # = x-rays get through =
image is darkimage is dark
 Metal = high atomic # = x-rays blocked =Metal = high atomic # = x-rays blocked =
image is light (white)image is light (white)

13. 5 Basic Radiographic Densities5 Basic Radiographic Densities
 AirAir
 FatFat
 Soft tissue/fluidSoft tissue/fluid
 MineralMineral
 MetalMetal

14. Different tissues in body absorbDifferent tissues in body absorb
X-rays at different extents:X-rays at different extents:
• Bone-Bone- high absorption (white)high absorption (white)
• Tissue-Tissue- somewhere in the middle absorptionsomewhere in the middle absorption
(grey)(grey)
• Air-Air- low absorption (black)low absorption (black)

16. Main Parts of the X-ray DeviceMain Parts of the X-ray Device
 X-ray tubeX-ray tube
 Voltage-Current GeneratorVoltage-Current Generator::
- High Voltage TransformerHigh Voltage Transformer – supplies high voltage– supplies high voltage
(up to 150kV)(up to 150kV)
- RectifierRectifier -- producesproduces unidirectionalunidirectional tube electrontube electron
currentcurrent

17.  Control panelControl panel – today most parameters of the– today most parameters of the
device (including voltage and current) aredevice (including voltage and current) are
controlled by means of a computer. It is locatedcontrolled by means of a computer. It is located
outside the examination room or behind a shieldoutside the examination room or behind a shield
made of glass containing lead (to protect themade of glass containing lead (to protect the
radiological assistantradiological assistant

18.  MainMain mechanical partsmechanical parts: tube stand,: tube stand,
examination table, grid for removing scatteredexamination table, grid for removing scattered
photons (‘Bucky’),photons (‘Bucky’),
 X-ray detectorX-ray detector: cassette with radiographic film: cassette with radiographic film
and adjacent fluorescent screens (and adjacent fluorescent screens (in radiographyin radiography))

20. Passage of X-rays throughPassage of X-rays through
PatientPatient's Body's Body
 X-rays emitted from a smallX-rays emitted from a small focal areafocal area of theof the
anode propagate in all directions. In the tubeanode propagate in all directions. In the tube
envelope, some low energy photons areenvelope, some low energy photons are
absorbed. Further absorption ofabsorbed. Further absorption of thesethese photonsphotons
occurs in theoccurs in the primary filterprimary filter, made of aluminium, made of aluminium
sheet.sheet. It absorbsIt absorbs low energy photons whichlow energy photons which
would be absorbed by surface tissues and do notwould be absorbed by surface tissues and do not
contribute to the image formation (unnecessarycontribute to the image formation (unnecessary
patient dose). X-ray beam is delimited bypatient dose). X-ray beam is delimited by
rectangularrectangular collimator platescollimator plates made of lead.made of lead.

21.  The rays then pass through the body whereThe rays then pass through the body where
transmission or absorption ortransmission or absorption or scattering mayscattering may
occur. After that they pass through theoccur. After that they pass through the gridgrid,,
which is in front of the detector to removewhich is in front of the detector to remove
scattered photons as these would degrade thescattered photons as these would degrade the
image.image.

22. WavelengthWavelength
 The wavelengthThe wavelength (( λλ )) of x-ray range 10of x-ray range 10
nanometers to 100 picometers (with frequencynanometers to 100 picometers (with frequency
10101616
Hz until 10Hz until 102020
HzHz).).
 These X-rays have a shape similar to that ofThese X-rays have a shape similar to that of
ordinary light rays, infrared and radio waves;ordinary light rays, infrared and radio waves;
differing only in terms of wavelength otherdiffering only in terms of wavelength other
features.features.

23. Electromagnetic SpectrumElectromagnetic Spectrum

24. Use of the Contrast AgentsUse of the Contrast Agents
 The soft tissueThe soft tissuess only slightly differ in theironly slightly differ in their
attenuation. Therefore they cannot beattenuation. Therefore they cannot be
distinguished in a common radiograph.distinguished in a common radiograph.
That is the reason for the use ofThat is the reason for the use of
pharmaceuticals calledpharmaceuticals called contrast agentscontrast agents..

25.  The attenuation of certain tissues can beThe attenuation of certain tissues can be
increased or lowered.increased or lowered. Positive contrastPositive contrast isis
achieved by substances having a high protonachieved by substances having a high proton
number as the probability of the photoelectricnumber as the probability of the photoelectric
effect is increased. A suspension of bariumeffect is increased. A suspension of barium
sulphate, “barium meal”, is used for imaging andsulphate, “barium meal”, is used for imaging and
functional examination of GIT. In examinationsfunctional examination of GIT. In examinations
of blood, biliary and urinary vessels etc.of blood, biliary and urinary vessels etc.
compounds with high content of iodine arecompounds with high content of iodine are
used.used.

26.  Hollow inner body organs can beHollow inner body organs can be
visualised byvisualised by negative contrastnegative contrast. Air or. Air or
better CObetter CO22 can be used. The cavities arecan be used. The cavities are
filled by gas, inflated, so that they can befilled by gas, inflated, so that they can be
visualised as structures of very lowvisualised as structures of very low
attenuation (pleural space, peritoneum,attenuation (pleural space, peritoneum,
brain chambers).brain chambers).

27. Positive and Negative ContrastPositive and Negative Contrast
Contrast image of the
appendix – diverticulosis –
combination with negative
contrast

28. Horseshoe kidney – positive contrast

29. Why is a lead shield/apron placed on youWhy is a lead shield/apron placed on you
when you get an x ray?when you get an x ray?
 X-rays emit radiation which cause mutationsX-rays emit radiation which cause mutations
to healthy cells. X-rays are only harmful ifto healthy cells. X-rays are only harmful if
you are exposed to them for a really LONGyou are exposed to them for a really LONG
time. X-rays you get at the doctors are okaytime. X-rays you get at the doctors are okay
because you don’t get them everyday. X raysbecause you don’t get them everyday. X rays
are more beneficial than they are harmfulare more beneficial than they are harmful
because they can detect problems that canbecause they can detect problems that can
be detrimental to your health.be detrimental to your health.

30. Different viewsDifferent views
 AP viewAP view
 PA viewPA view
 LateralLateral

31.  Can be obtained by changing the relativeCan be obtained by changing the relative
orientation of the body and the direction of theorientation of the body and the direction of the
X-ray beamX-ray beam

32. The PA (postero-anterior) viewThe PA (postero-anterior) view
 It is the mostIt is the most frequently requiredfrequently required radiologicalradiological
examination. Comparison of current film withexamination. Comparison of current film with
old films is valuableold films is valuable

33. Position:Position: Patient facing thePatient facing the
film, chin up with the shouldersfilm, chin up with the shoulders
rotated forwards to displacedrotated forwards to displaced
the scapulae from the lungs.the scapulae from the lungs.
Exposure is made on fullExposure is made on full
inspirationinspiration

34. AP viewAP view
 The X ray beam enters through anterior aspectThe X ray beam enters through anterior aspect
and exits through the posterior aspectand exits through the posterior aspect

35. Lateral view:Lateral view:
 The pt stands with bothThe pt stands with both
arms raised and the left sidearms raised and the left side
of the chest pressed againstof the chest pressed against
a flat surfacea flat surface

36. Lateral decubitus positionLateral decubitus position
 It is helpful to assess the volume of pleuralIt is helpful to assess the volume of pleural
effusion and demonstrate whether a pleuraleffusion and demonstrate whether a pleural
effusion is mobile or noteffusion is mobile or not
Lateral decubitus position film showing mobile
pleural effusion (arrows

37. CTCT
ScannerScanner Computed tomography or CT scan
works on the same principles as fixed
plate x rays, only with a CT scan, an x ray
tube rotates around the individual, taking
hundreds of images that are then compiled
by a computer to produce a two-
dimensional cross section of the body.
Although many images are taken to
produce a CT scan, the total dose of
radiation the individual is exposed to is
low.

38. Optimal ViewingOptimal Viewing
 Dedicated light sourceDedicated light source
 Darkened environment (like a movie theater)Darkened environment (like a movie theater)
 Limit distractionLimit distraction

39. X-ray viewing station

40. Medical ImagingMedical Imaging
 Primary purpose is to identify pathologicPrimary purpose is to identify pathologic
conditions.conditions.
 Requires recognition of normal anatomy.Requires recognition of normal anatomy.

41. Summary:Summary: How do x-rays create an image ofHow do x-rays create an image of
internal body structures?internal body structures?
 X-rays pass through the body to varying degreesX-rays pass through the body to varying degrees
 Higher atomic number structures block x-raysHigher atomic number structures block x-rays
better, example bone.better, example bone.
 Lower atomic number structures allow x-rays toLower atomic number structures allow x-rays to
pass through, example: air in the lungs.pass through, example: air in the lungs.