Transcript ct 2 yearx

Computed
Tomography
by
Ms. Nouf Alzahrani
Dr. Saddiq Jastniah
King Abdulaziz University
Faculty of Applied Medical Science
Radiology Department-
2nd year
What is a computed tomography
Scan
 It is a non-invasive medical
imaging procedure that combines
the use of X-rays and computer
processing to generate
tomographic (‘slices’) of the area
scanned.
 A computerized axial tomography
scan is more commonly known by
its abbreviated name, CAT scan or
CT scan
 Four classifications of the types of
scans:
Abdominal-Bone-Head-Vascular
CT scanner
System components of CT scanner
scanner room
computer
room
CT unit is divided into three main
rooms:
operating
room
Scanner room
GANTRY.
PATIENT COUCH (table).
Automatic Injector
GANTRY
This is shaped like a giant donut and it maintains the
alignment of the x‐ray tube and detectors
Gantry Houses:
(components) from inside :
X‐ray tube: produce the x‐rays
(ionizing radiation) with
continuous exposure.
Filter: to reduce the low energy
x‐rays which are not useful for
imaging
Collimators:
• Pre‐patient collimator mounted
on the tube housing, creates
more parallel beam and reduce
patient dose.
• Post‐patient collimator reduces
the scatter radiation on the
detector.
Detector arrays: to absorb the
x‐ray beam and located at the
opposite side of the tube.
Filter
pre
C
Patient
post
C
Detector
DAS
components from out side :
Control panel.
Display panel.
Aperture
Emergency button.
Icon
Function
Description
Stop Scan
When pressed, stops X-ray exposure, turns off the laser
alignment lights, halts all gantry and table motions.
Control
panel
Scan Start
Table In
Table Out
Table Up
When pressed, the table moves in, toward the
Gantry.
When pressed, the cradle moves out, away from
the
gantry.
When pressed, the table moves up and towards the
gantry. When the table moves up with the laser
alignment lights on, the cradle will adjust horizontally
to maintain the anatomic reference point
Icon
Function
Description
Table Down
When pressed, the table moves down and away from the
gantry.
Fast Speed
When pressed in conjunction with Table Up/Down or Cradle
In/Out, causes those functions to operate at a faster speed.
Control
panel
Tilt and
Table
Travel
Limits
Laser
Alignment
Light
Pressing allows you to view the current gantry tilt range and
scannable range, based on table position, on the gantry display
panel.
A toggle when pressed, turns all the laser alignment lights on or
off. These are used to help establish landmark locations.
Pressing (Cradle Lock) once unlocks the table, making it "free
Table
Lock/Release floating". This means that the cradle can be moved freely with
your hands.
Home
Pressing (Home) simultaneously moves the cradle out of the
gantry and return the gantry tilt to zero degrees..
Gantry Display
The gantry display provides gantry and
table status information
Table or Couch
 The CT table may be either flat or curved and it is used to
load a patient for scanning.
 It is usually made of carbon fiber material that is strong
enough;
 the table must be capable of vertical (up‐down) and
horizontal (in‐out) movements.
Automatic injector
Some examinations require injection of contrast
media to highlight specific areas.
The injector is used to inject the contrast through
vessels automatically and it consists of:
1‐ Two syringes: one for contrast, and the other
for saline "water".
2‐ Connecting tube.
3‐ Cannula (needle) with appropriate size.
4‐ Injector control monitor and it is located in
the operating console room.
Accessories
head holder
 Axial head holder
 Coronal head holder
U –shaped Foam insert
Cradle extender
Knee cushion
Arm support
Foam wedges
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The operating console will usually have tow TV monitors:
1‐ Scan monitor: this monitor can be mainly used for scanning
patients, adjusting the technical factors, slice thickness, angle of gantry and initiates scan , record
patient data(hospital identification, name , patient number, age ,sex ) and to provide
identification for each scan.
2‐ Display monitor: used to view the resulting images to manipulate post scan data, post
processing work‐measurement and 3D formations before sending to the radiologists.
3‐ Keyboard/mouse
Scan monitor
The Scan monitor contains the user interface that controls all aspects of scanning from entering
patient information to ending the patient exam.
Keyboard and Scan Interface module
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5
.
1.
Emergency Stop - In the event of an emergency situation, pressing emergency stops, stops
all table and gantry motions.
2.
Exposure Indicator - The (Exposure Indicator) illuminate amber when an actual exposure
is taking place.
3.
Start Scan - The (Start Scan) indicator flashes green once the tube has reached exposure
speed. Simply press the button to start the scan. Start Scan will flash for 30
seconds before timing out.
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4.
Move to Scan - The (Move to Scan) indicator flashes green indicating that the system is
ready for you to advance the cradle into the starting position. Simply press the button to advance
the
cradle. Move to Scan will flash for 180 seconds before timing out.
5.
Remote Tilt (Prescribed Tilt)- Press (Prescribed Tilt) and hold the button down until
the prescribe tilt is achieved.
6.
Talk - Pressing (Talk) and speaking towards the intercom above the button allows
you to communicate with the scan room.
7.
Volume Control (operator to patient) - This dial controls the volume of the
operator’s voice to the patient.
Set Up Patient Information
Use this procedure each time you start a new patient exam. It is best to setup the patient
information before you get the patient on the table.
1. click Patient Schedule,
2. From the scan monitor, click [New Patient].
3. click {add patient}
• The Patient Information screen appears automatically displaying the new Exam
Number. Enter the patient information.
• Click [Accept] to save changes and add patient information to the schedule list.
1.From the scan monitor, click [New Patient].
2. Then Set Patient Information
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Position the Patient
1.Head first
2.Feet first
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Selecting a Protocol
1. On the left monitor, place the mouse over the area that you want to scan and click on it.
􀂊 A list of all the protocols that you built in this area of the protocol manager appears.
2. From the list, select the protocol that you want to use by clicking on it.
Brain routine
Image
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Scout View
Axial Image
What happens when x-ray passes through
the patient?
• Attenuated and measured by the detector
• X ray tube and detectors are hidden inside the gantry of scanner
and rotate around patient during scanning
• Detector converts x ray photons into electrical signals (analog),
which must be converted into digital (numerical) for input on
computer
• Computer makes the image reconstruction process
• Reconstructing an image is in numerical form and must be
converted into electrical signal so it can be displayed on a television
monitor for viewing
• Image can be stored on magnetic tapes or optical disks and
recorded on x-ray film
CT images
Manipulation
transverse axial images
can be reformatted into
coronal , sagittal , and
three dimensional
processing
Computer room
The computer is designed to solve many
equations through controlling data
acquisition, processing, displaying, and
storage.
 Scanners store image data on either floppy
disk or magnetic tapes.
HARD COPY
LASER PRINTERS
COMMUNICATION
PACS