it includes generations and advancement in CT. In generations fifth generation CT is described in detail. UFC detector, stellar detectors and gemstone detector is also described straton x-ray tube, MRC, LIMAX and aquillion one xray tube different techniques used in CT dual energy CT is also described

1. GENERATIONS AND ADVANCEMENT IN CT
SUMAN DUWAL
NAMS, Bir Hospital

2. overview
 Generations
 Advancement in CT
Advancement is focused more than generations in this presentation

3. Generations
 First generation
 Second generation
 Third generation
 Fourth generation
 Fifth generation
 Sixth generation
 Seventh generation
Among the generations, 5th generation is discussed more than other generations

4. First generation
 Pencil beam geometry
 Rotate/translate
 5 min required for a single
image.

5. Second generation
 Narrow fan beam geometry
 Translation/rotation
 Linear array of 30 detectors
 18 sec per slice

6. Third generation
 Rotate/rotate
 No of detectors increased to
more than 800
 Wide angle fan beam geometry
 Less than 5 sec to complete a
single slice

7. Fourth generation
•Rotate/stationary
•Incorporated with a large stationary
360 degrees ring of detectors with
the x-ray tube alone rotating around
the patient.
•Use of 4800 detectors

8. Fifth generation
 EBCT/EBT/UFCT/Cine CT
 Used for cardiac imaging which requires ultra fast scan time(<50ms)
 First introduced by the group of researchers in Douglas Boyd at the
university of San fransisco
 The company Imatron Inc. started commercial production and
distribution of EBCT system in 1984
 The sole manufacture of EBCT systems developed several scanner
generation( C-100, C-150, C-300)

9. Principle of EBCT

10. Fig: Imatron C 150 scanner

11. Fig: coronary angio performed in C 150

12. Fig: Imatron 300 scanner

13.  Imatron Inc. had a partnership with Siemens medical system which
results in several technical improvements of the scanner.
 In 2001, GEMS acquired Imatron Inc. and created daughter company
named ‘GE Imatron Inc’ for manufacturing, servicing and sales of
EBCT
 In Nov 2002 GEMS launched a new model EBCT called “e-speed” first
completely new EBCT scanner since company bought Imatron

14. e-speed
 Significant improvement over previous model C-300
 Has completely new power source(140 KW) for smoother and higher resolution.
 Enables scan time of 50 and even 33 ms(2-3 times faster then previous EBCT
scanners).
 e-speed is suitable for both cardiac and non cardiac applications.
 10 times faster than true scan speed of 256 slice CT(500 ms)
5 times faster than dual source CT(166ms)
 In terms of radiation dose 10 times lower radiation dose compared to 64 slice CT
 Due to its structural complexity and cost effectiveness and rapid advancement in
MDCT the role of EBCT is under the shadow.

15. Fig: e speed scanner and VRT image of heart demonstrating CAs

17. Sixth generation
 Spiral/helical CT
 Three technological development
 Slip ring technology
 High power x-ray tube
 interpolation

18. Fig: slip rings
Cylinder design Disc design

19. Fig: spiral/helical acquisition

21. Seventh generation
 MSCT/MDCT
 It is based on 3rd generation
geometry.

22. Advantage of MDCT
 The latest breakthrough in CT technology.
 The primary difference between single-slice CT (SSCT) and
MDCT hardware is in the design of the detector arrays.
 Faster Gantry rotation(sub second).
 Fast Data Acquisition System.
 High Speed image reconstruction system.
 The high rating x-ray tube i.e. 8 MHU or more.
 Multiple reconstruction technique.

23. Advancement
 Advancement in detectors
 Advancement in x-ray tube
 Gantry rotation time
 DECT
 Different techniques
 PET CT
 Portable CT

24. Advancement in detectors
 UFC
 Stellar detector
 Gemstone

25. Ultrafast ceramic
 Ultrafast ceramic is a hard yellow substance that resembles like
plastic and weighs as much as gold.
 UFC uses a crystal lattice of rare earth compounds like
gadolinium oxysulphide(GOS) and other compounds

26. Fig: UFC detector Fig: higher luminous efficiency
of UFC

27. Advantages of UFC
 High x-ray absorption efficiency
 Short afterglow
 Fast decay time
 Can be used with the fastest CT scanners, with rotational speeds well
under 0.3 seconds
 Resistance to air, humidity ,water , temperature and numerous
chemicals.

28.  The decay constant is nearly 3 ms and its optimized for
interrogation time of 20ms in order to maintain the image
quality.
 No permanent damage at all could be observed after 10 years of
operation(with 30kGray).
 UFC is a non-poisonous material that does not contain any toxic
elements as other solid state scintillation materials do.

30. Fig: afterglow behavior of UFC and other scintillator material

31. Stellar detectors
 The stellar detectors have combined all the analysis electronics in a
single chip
 The converted signals can be processed digitally with no loss which
makes possible to produce medical images with a noticeably higher
signal to electronic noise ratio(SNER) than before at the same radiation
dose.
 Reduces the image noise by 20 to 30% compared to conventional
detectors.
 Stellar detector consumes approximately 70% less power and dissipates
less heat than conventional detectors further reducing the image noise

33. Development of detectors

38. Fig : reduction in the image noise with the use of stellar detector

40. Gems stone detector
 It is the newly developed transparent polycrystalline scintillator
CT detector developed by GE health care.
 It has higher sensitivity to radiation and allow faster sampling
rate.
 It is made up of cerium activated rare earth based garnet material
 It is used in single source ultrafast dual energy switching ,
promising almost simultaneous spatial and temporal registration
and material decomposition.

41.  It has primary decay time only 30nsec i.e. 100 fold faster than
conventional scintillator.
 The most advantage of gemstone detector is the improved spatial
resolution.( high definition imaging up to 230mm resolution.)
 It has very low afterglow, extremely low radiation damage, very
good chemical durability and uniformity

43. Fig: decay time of gemstone and GOS

44. Fig: afterglow behavior of gemstone and GOS

46. Arrangement of the detector
 Matrix(uniform) array detector
 Adaptive(non- uniform) array detector
 Hybrid(mixed) array detector

47. Matrix array detector
 Also referred as uniform array detector.
 Contains detector elements that are equal in all dimensions.
 Used in GE scanners

48. Adaptive array detector
 Also called as non- uniform type of detector
 Detectors with variable thickness thinner rows centrally and
thicker rows peripherally.
 Used in Phillips and Siemens scanners

49. Hybrid array detector
 Detectors with two fixed thickness four thinner elements
centrally and thicker elements peripherally.
 Used in Toshiba scanners.

50. Advancement in CT tube
 Straton tube
 MRC( Maximus rotalix ceramic x-ray tube)
 LIMAX( liquid metal anode x-ray tube)
 Aquillion one x-ray tube

51. Straton tube
 One of the interesting development
is Siemens straton x-ray tube.
 The tube itself is a radical new
design where the entire tube body
rotates rather then just the anode
 This change allows all the bearings
to be located outside the evacuated
tube and enables the anode to be
cooled more efficiently.

55.  It has the low inherent heat capacity of 0.8 MHU but an extremely fast
cooling rate of 4.7 MHU/min ( Siemens claims the heat storage
capacity of 0 MHU)
 This compares with typical figures of 7-8MHU and up to 1.4MHU/min
for existing tubes.
 Tube cooled down within 20 sec
 Anode diameter: 120 mm
 Anode material : tungsten, zirconium and molybdenum
 Focal spot/track: alloy of tungsten and rhenium

56.  Enables gantry speed of 0.37 sec per rotation
 The electron beam in the tube is shaped and controlled by magnetic
deflection coil

57. Flying focal spot
• The no. of measurements channel can be doubled by rapid deflection of
X-ray tube focal spot for each projection increasing the image
resolution.
• This technology is achieved by electromagnetically deflecting the
electron beam within the X-ray Tube.
• For each focus position 2 – measured interlaced projection result, since
the detector continue to move continuously which double the sampling
frequency & enhance the spatial resolution.

58. (MRC) Maximus rotalix ceramic tube
 Introduced by Phillips in 1989
 Based on the technology of spiral groove bearing using liquid metal
alloy as the lubricant.
Fig: MRC x-ray tube
Fig: MRC model 600

59. Advantages of MRC
 Dissipation of the heat via the
liquid metal lubricant gave the
tube higher cooling capacity.
 Noiselessly rotating anode and
have a very long lifetime.
 Avoid waiting time during and
between examination.

60.  200 mm graphite backed anode
 Anode heat storage capacity- 8MHU
 Tube voltage- 90 to 140kv
 Tube current- 20 to 500 mA
 Anode angle- 7o

61. (LIMAX)Liquid metal anode x-ray tube
 The novel x-ray tube concept which predicts producing x-rays in a
turbulent flowing liquid metal which interacts with the electron beam
which is transmitted through a thin window.
 In this tubes an electron beam interacts with the liquid metal stream
flowing turbulently at high speed in a narrow channel
 Liquid metals eutectics, of SnPb, GaInSn, PbBi or PbBiInSn

62. Liquid metal
 It should contain element with high atomic number
 High thermal conductivity
 Chemically inert
 Liquid metal has to serve at least 2 purposes:
 It acts as the cooling medium
 It serves as the x-ray photon generating medium
 PbBi is the best choice as it got the higher x-ray output than other
liquid metals

63. Fig : photon emission spectra of three liquid metals covered with 5µm diamond

64. Electron beam window
 The x-ray photon will leave the anode in a reflection geometry , thus
the electron window has to have a low absorption coefficient
 Due to its extreme toxicity and relatively low melting point beryllium
cannot be used as the electron beam window material.
 Carbon in the form of diamond is the best choice due to high young’s
modulus , extremely good thermal conductivity, inertness to liquid
metals

66. Aquillion one

67. Aquillion one x-ray tube
 Heat storage capacity- 7.5 MHU
 Cooling rate- 1.7 MHU/min
 Anode is grounded
 Focal spot- 1.4mm* 1.4mm
 Air cooled tube

68. Gantry rotation time
 Rotation time is the time interval needed for a complete 360 ° rotation
of the tube and the detector system around the patient
 A short rotation time has following advantages
 Longer spiral length can be acquired in the same scan time
 Same volume and same slice thickness can be scanned in less time
 Increased temporal resolution
 Motions artefacts are reduced

69. Sub second gantry rotation
 In 16 slices- 0.5 sec
 In 64 slices- 0.3 sec
 In 320/640 slices- 0.27 sec

70. Post processing technique
 Multiplanar Reconstruction(MPR)
 MPR is the fast reconstruction method.
 Provide coronal or sagittal plane from axial scan.
 Depend on acquisition parameter- thin collimation
excellent results.
 Commonly used in orthopedic examination

71.  Shaded surface display(SSD)
 Also called surface rendering
 The marching cubes algorithm must be hallmark for surface
rendering.
 Commonly used for fracture, deformities of bone, CTA

74.  Volume Rendering Technique(VRT)
 Representation, visualization & manipulation of objects
represented as sampled data in 3 or more dimensions.
 Commonly used in CTA, CT Coronary angiography

75.  Maximum Intensity Projection(MIP)/ Minimum Intensity Projection(MinIP)
 MIP is a relatively simple method.
 for visualization permits easy viewing of vascular structures or air-filled
cavities.

78.  Virtual Endoscopy
 Used for 3D reconstruction of upper GI.
 Virtual Colonoscopy
 Used for 3D reconstruction of Colon.
 Virtual Bronchoscopy
 Used for 3D reconstruction of airways.

79. Fig: fly through technique

80. Dual energy MDCT
 DECT uses the principle that different material shows different attenuation at
varying energy level and this difference can be used for better tissue
characterization.
• With dual-energy CT, two image datasets are acquired in the same anatomic
location with two different x-ray spectra to allow the analysis of energy-dependent
changes in the attenuation of different materials.
• Each type of material demonstrates a relatively specific change in attenuation
between images obtained with a high-energy spectrum and those obtained with a
low-energy spectrum, and this attenuation difference allows a more distinct
characterization of the features depicted.
• Two different materials that show similar attenuation on images acquired with one
of the two energy spectra are often more easily differentiated on images acquired
with the other spectrum because of substantial differences in their attenuation

81. When dual-energy images reconstructed for 50 and 80 keV are compared, iodine
demonstrates a greater decrease in attenuation than calcium does at the higher energy,
whereas the attenuation of water remains more or less constant

82. Historical perspective
 In the early days, Sir Hounsfield proposed that ,two pictures are
taken of the same slice one at 100KV and other at 140 kv. tests
carried out have shown that iodine (z=53) can be readily
differentiated from calcium(z=20)
 Alvarez , Macovski and Calender also described the theoretical
basis of the dual energy scanning in the early 1980s.

83.  In 2006 DECT is introduced for the first time commercially
( somatom definition, Siemens)(DSDECT)
 First generation DSDECT have FOV limited to 26cm
 Whereas in second generation it was broaden up to 33cm
 Over the time new modifications and advancement on DECT
were made.
 Then later single source dual energy CT was introduced by GE

84. fig: 1st generation fig: 2nd generation

85. SSDECT

86. Types of DECT
 Source driven approach
 Dual source dual energy
 Single source single energy
 Detector driven approach
 Single source dual layer detectors
 Photon counting detectors

89. Clinical use of DECT
 Direct subtraction of bone.
 Differentiation between plaque and contrast agent
 Virtual unenhanced abdominal organ imaging
 Kidney stone characterization
 Visualization of cartilage, tendons, ligaments
 Evaluation of lung perfusion defects
 Heart perfusion blood volume
 Uric acid crystal visualization
 Lung vessel embolisation
 Brain hemorrhage differentiation.

90. Dose modulation techniques
 SURE DOSE used by Toshiba scanners
 DOSE RIGHT used by Phillips scanners
 CARE KV and CARE DOSE 4D by Siemens scanners
 AUTO MA or SMART MA by GEMS

91. Iterative reconstruction dose reduction
 AIDR-3D - Toshiba (adaptive iterative dose reconstruction)
 ASIR – GEMS(adaptive statistical iterative reconstruction)
 I DOSE IMR – Phillips(iterative model reconstruction)
 ADMIRE- Siemens(advanced modeled iterative reconstruction.

92. Metal artifact reduction techniques
 SEMAR- Toshiba
 MAR- GEMS
 iMAR- Siemens
 O-MAR- Phillips

96. O- MAR

97. matrix
80 x 80 512 x 512

98. PET CT
 PET and CT provide complementary information.
 PET provides functional information but little anatomic detail.
 CT provides anatomic and morphologic information (size,
shape, density of lesions ) but provides little physiologic
insight into tissues

99. Fig: PET CT

100. Portable CT

101. SUMMARY

102. bibliography
 Liquid-metal anode x-ray tube, DOI: 10.1117/12.504503
 https://www.spiedigitallibrary.org/conference-proceedings-of-
spie/5541/0000/Liquid-metal-anode-x-ray-tubes--interesting-but-
are/10.1117/12.561615.short?SSO=1
 http://spie.org/Publications/Proceedings/Paper/10.1117/12.561615
 Essential book of Physics - Busburg, third edition.
 Diagnostic radiology. Recent advances and applied and applied physics in
imaging.( Arun Kumar gupta , veena chowdhary , niranjan khandelwal)
 Christensen's Physics of Diagnostic Radiology Fourth edition
by Thomas S.curry,James Dowery

103.  Gemstone – The Ultimate Scintillator for Computed Tomography
(GE Healthcare)
 www.mahameru.com
 www.genewsroom.com
 Comparison of Three Generations of Electron Beam Tomography on Image Noise
and Reproducibility, a Phantom Study
Chau, Alex BS; Gopal, Ambarish MD; Mao, SongShou MD; Tseng, Philip H. BS;
Fischer, Hans MD, PhD; Budoff, Matthew J. MD
 matron's C-150 scanner as Evolution EBT (SCAN 4/12/95).
 Electron Beam Computed Tomography (EBCT)
Valentin E. Sinitsyn, Stephan Achenbach

104.  https://www.researchgate.net/figure/Virtual-endoscopy-showing-
concentric-narrowing-of-the-airway-a-View-of-the-proximal-
part_fig2_46289289
 www.radiopaedia.com
 https://www.jbsr.be/articles/10.5334/jbr-btr.1420/
 www.phillips.co.uk

105. Thank You!!!!