HISTORY Flashcards
1
Q
- Hounsfield build a who,e body ct scanner
A
1975
2
Q
Hounsfield and Cormack were bith awarded with nibel prize in Physiology and Medicine; Two Popular Names of Computed Tomography
A
1979
3
Q
Two Popular Names of Computed Tomography
A
- Computer Axial Tomography (CAT)
- Computerized Tomography (CT scan)
4
Q
Electrical Musical Instrumentation (EMI) CT SCANNER
A
1979
5
Q
Introduced by Sir Godfrey Hounsfield
* Exclusive for neurologic examinations only
* Worked by a process called translation or rotation
* Patient’s head was recessed via a rubber membrane into a water filled box
A
1971
6
Q
Features: 1ST GEN
A
- Scanning Motion or Tube Detector
Movements: Translate- Rotate - Detectors: Single
- Xray source: Single
- Xray beam: narrow pencil shaped xray beam
- Duration of scan: 25-30 mins; 3-5 mins to scan one slice; 1.5 min to reconstruct
- Scan mode: step and shoot scanning
- Power supply: straighten twisted system cables
- Number of slice per rotation: 1
- Motion of gantry: linear and rotary
7
Q
is made up of Sodium lodide (Nal): (1ST GEN)
A
Detector
8
Q
180 translations with __rotation in linear motion (1ST GEN)
A
1 degree
9
Q
Total Rotary motion encompassed a ___ (1ST GEN)
A
180 degrees semicircle
10
Q
___ passed through the center of the patient’s head (1ST GEN)
A
Axis of rotation
11
Q
X-ray beam is “__” throughout the linear movement and “__” during rotary movements
A
ON
OFF
12
Q
ADVANTAGE
(1ST GEN)
A
- Low scattered radiation
13
Q
DISADVANTAGE (1ST GEN)
A
- Time Consuming
- Slow Reconstruction time
- Low Anatomic in an image
- Poor Spatial Resolution
- Nal is hygroscopic (absorbs moisture from air)
- Complicated Patient Positioning
14
Q
was an improvement in efficiency from its predecessor, while still utilizing similar general concepts.
A
second-generation CT
15
Q
The ____ is still used with an addition of multiple small fan beam to allow for a
more optimized and better coverage when compared to just one detector. (2ND GEN)
A
translate and rotate acquisition
16
Q
second-generation CT was first introduced, developed, and installed by ___ at Georgetown University in February 1974.
A
Ledley et al.
17
Q
machine utilizes 30 photomultiplier tubes as detectors and can complete a scan in only 9 translate/rotate cycle.
A
2ND GEN CT
18
Q
The device introduced many features that are now standard in modern CT____
A
(table movement through the gantry, gantry angulation, and a laser indicator to position slices) as well as a Fourier-based reconstruction.
19
Q
Second generation CT scanner
A
Narrow fan beam (10°)
Multiple detectors
Multiple angle acquisition at each position
Larger angle rotate Translate still required
Slow
- 20s per slice
20
Q
Pros: (2ND GEN)
A
- reducing scan time by 3-fold
- The trunk could be imaged
- By adding detectors angularly displaced , several projections could be obtained in a single translation
21
Q
CONS:(2ND GEN)
A
- Further speed improvements were hindered by the mechanical complexity of the rotate-translate geometry
- Translations and rotations have to be performed quickly and precisely while moving heavy (lead-shielded) x-ray tubes and the associated gantries and electronics- all while minimizing vibrations, which would cause artifacts.
22
Q
3 detectors each displaced by ___ (EARLY VERSION 2ND GEN)
A
1°
23
Q
Since each detector viewed the x-ray tube at a different angle , a single translation produced ___ (2ND GEN, EARLY VERSION)
A
3 projections
24
Q
The system could rotate 3° to the next projection rather than 1° (EARLY VERSION, 2ND GEN)
A
2ND GEN CT
25
– make only 60 translations instead of 180 to acquire a complete section (EARLY VERSION)
2ND GEN CT
26
Scan times were reduced X 3 (EARLY VERSION)
2ND GEN CT
27
up to 53 detectors
2ND GEN CT, LATER VERSION
28
– Fast enough (tens of seconds)to permit acquisition during a single breath hold – First designs to permit scans of the trunk
– Because rotating anode tubes could not
2ND GEN CT, LATER VERSION
29
an electrical engineer at EMI (Electric and Musical Industries Ltd).
Sir Godfrey Hounsfield
30
are first introduced in 1975, in this generation marked the breakthrough of modern ct scan making it one of the successful generations. Thus making it as a bedrock of contemporary era of diagnostic imaging .
3RD GEN CT
31
It uses fan beam shaped of 40 – 60 degrees which covers the entire patient (all anatomy) acquiring all the data within each view
3RD GEN CT
32
It uses a an acquisition mode of “rotate-rotate” both the x-ray source and x-ray detector are rotating together. Using a rigid ring the x-ray tube and detector can be mounted such that they rotate around the patient. Larger array of detectors (more than 800) were used. Scanning time was reduced to 2 seconds.
3RD GEN CT
33
it is capable of generating high quality contrast images while delivering lower doses of ionizing radiation than their predecessors.
3RD GEN CT
34
What is exactly “rotate-rotate “ acquisition mode?
1. The x-ray beam hits a row of detectors wide enough to image the whole slice
2. The two then rotate together to image a different angle
3. This is repeated until a single slice is scanned then the array is moved to a different slice (axial scanning).
4. Alternatively, the detector array is continually moved down the patient as it rotates (spiral scanning This is the most commonly used method today and takes about 0.3 seconds to image a single slice
35
It requires extremely high detector stability and matching of the detector response
3RD GEN CT
36
If one of the detectors is out of calibration on a third-generation (rotating x-ray tube and detector assembly) scanner, the detector will give a consistently erroneous reading at each angular position, resulting in a circular artifact.
RING ARTIFACTS
37
CT scan image of a water-filled phantom shows ring artifacts
3RD GEN CT
38
A scanner with solid-state detectors, where all the detectors are seperate gas detectors, in which more susceptible to ring artifacts than a scanner with gas detectors, in which the detector array consits of a single xenon- filled chamber subdivided by electrodes
3RD GEN
39
were inherently stable and well matched because factor affecting detector response were either uniform for the entire array or constant over chamber.
XENON
40
Xenon were eventually replaced by solid state detectors
3RD GEN CT
41
Detectors:3RD GEN CT
multiple, originally 288; newer ones use over 1000 arranged in an arc
42
Type of beam::3RD GEN CT
fan-shaped x-ray beam
43
Helical ("spiral") image acquisition due to Slip-ring technology. Dual energy CT scanning
3RD GEN CT
44
Number of slice per rotation:3RD GEN CT
multiple due the parallel detectors array configuration, include x-ray detectors large enough to cover an entire organ in a single rotation.
45
Duration of scan (average):3RD GEN CT
approximately 5 sec
46
In 1976, 1 second scans were achieved with a design incorporating a large stationary ring of detectors, with the x-ray tube alone rotating around the patient.
4TH GENERATION CT SCAN
47
In 4th Generation CT Scan, the X-ray tube has to move inside this detector. Since it is rotated continuously, very fast scan time is possible. It has inter scan delay times, since the X-ray tube had to return to its starting position
Rotary X-ray Source
48
4th Generation Stationary array of detectors encircles the patient. These systems had fewer moving parts and needed not pass signal data across the moving gantry. It has a stationary ring of about 4,800 detectors
.Stationary Detector Ring
49
INNOVATIONS (4TH GEN CT)
1. SHORTER SCANNING TIME
Only the x-ray generator and tube rotate at 360, thus shortening the scanning time even more
2. REDUCE MOTION
Since the procedure takes up for a short amount of time only, motion is reduced which resulted in reduction of complexity.
3. ELIMINATE RING ARTIFACTS
The primary purpose of the fourth-generation scanner is that it overcomes a specific third- generation artifact. A ring or arc artifact in a CT is a hardware related artifact that occurs due to a defective or miscalibrated detectors.
50
LIMITATIONS(4TH GEN CT)
1. HIGH COST
The design principle, however, has currently been abandoned because of high system costs as a consequence of the large number of detector elements and other problems.
2. LESS EFFICIENT
In 4th generation CT scanners only small portion (about 30% to 40%) of a large array of detectors are exposed at any one time in operation.
3. INEFFECTIVE SCATTER REJECTION
Anti-scatter grids attached to stationary detectors would not remain focused to a moving X-ray source in operation, focused anti- scatter grids have not been used in fourth generation scanners
4. HIGHER PATIENT DOSE
The x-ray tube is closer to the patient, resulting
in higher skin dose.
51
Make images without rings
4th Gen 1976
52
All Anatomy Rotate-Stationary 1 sec
Expensive, not good for scatter
4th Gen 1976
53
Both the x-ray source material and the detector are stationary. In this sense this is a stationary-stationary design.
5th generation CT
54
* Three rings
* Each ring makes connectivity to the X-ray generator, detector, and control signals.
SLIP-RING
55
SLIP-RING
6TH GEN CT
56
The X-ray tube can rotate faster (5 s/rot) and move more than 360 degrees.
6TH GEN CT
57
* Reconstruction is possible at any desired z-axis position.
6TH GEN CT
58
* Eliminatedinterscandelay.
6TH GEN CT
59
* Made helical CT possible.
6TH GEN CT
60
ADVANTAGES: 6TH GEN CT
Shorter total scan time
Requires less contrast media Improve image resolution Decreased patient risk to contrast media reactions Eliminates overlap & missed areas
Pitch settings can be set to oversample sections of interest Improved diagnostic accuracy
Beneficial to patient comfort.
Large volume of tissue in a single breath hold.
Beneficial to department productivity
Superior MPR & 3D reformation
61
DISADVANTAGES: 6TH GEN CT
Full 360° projection data is not acquired for each section. Characteristics
Sections are reconstructed to represent approximate acquisition of planar data.
62
Applications 6TH GEN CT
* CT Angiography
* Radiation Therapy treatment planning
* Imaging uncooperative patient
63
* Multislice CT
* Multidetector Array (MDA)
* Produces multiple slices in a single rotation.
* The number of X-ray detected is 4 times higher.
7TH GENERATION
64
* Increases slice thickness
* Reduced spatial resolution
Single Array
65
Single Array
7TH GENERATION
66
* Slice thickness is determined by detector size not by the collimator.
Multiple Detector Array
67
Multiple Detector Array
7TH GENERATION
68
High - Speed CTScanner
5TH GEN
69
Electron - Beam Scanner (EBC Use for cardiac only and
Has a dynamic spatial reconstruction ability.
5TH GEN
70
* HIGH SPECIALIZED AND HIGH SPEED
* HIGH SPECIALIZED AND HIGH SPEED SCANNER
* REOUIRE SCAN DATE IN MILLISECOND
5TH GEN
71
was dedicated cardiac scanning.
The niche of 5th generation CT
72
This method allows for very fast acquisitions and is ideal for cardiac scanning (with a temporal resolution of a given slice as low as 17ms).
5th generation CT
73
these scanners did not have full volumetric coverage and the flux that could be delivered was more limited.
5th generation CT
74
Both the x-ray source material and the detector are stationary.
5th generation CT
75
The x-tube in this design is a scanning x-ray tube, where the electrons are steered magnetically (like in old TVs) rather than physically moving the x-ray tube.
5th generation CT
76
* Helical or Spiral CT
* Volumetric Scanners
* Continuous data acquisition scanning
* Uninterrupted table movement
6TH GEN
77
* Willi Kalender
German medical physicist
* Kazuhiro Katada
Professor, Department of radiology, Faculty of Medicine, Fujita Health University
6TH GEN
78
is an electromechanical device that conducts electricity through rings & brushes across a rotating surface onto a fixed surface.
Slip-ring Technology
79
Helical CT Scanners
6TH GEN
80
Perform a scan in which the patient moves slowly through the gantry.
Slip-ring Scanners (6TH GEN)
81
Patient is simultaneously transported at a constant speed through the gantry.
One breath-hold & obtain a volume of x-rayed tissue. Data are continuously acquired without pausing.
6TH
82
Scans with CT technique recquired 15 to 30 minutes. but Helical CT scanner is faster.
6TH
83
The x-ray beam from the CT traces a helical path.
6TH
84
* The tube is energized continuously.
SLIP-RING TECHNOLOGY
85
* 8 Slice (7TH)
2000
86
* 64 Slices (7TH)
MODERN
87
Multislice CT * 4 slice (7TH)
1998
88
* 16 Slice (7TH)
2001
89
* 256 Slices (7TH)
Future Advanced
90
ADVANTAGES(7TH)
Provides longer & faster z axis coverage Increased volume coverage/ unit time Reduces total examination time
Allows post-acquisition reconstruction Increases image resolution
91
* Artificial Intelligence (AI) * Detect acute neurologic occurrences within 1.2 seconds * Using 37,000 head CT exams * The process is 150 times faster.
THE FUTURE OF CT SCAN
