Scanning Systems, CT

• GROUP MEMBER:AHMAD RAFIQAN BIN NAYANMuhammad Irfan Bin AliasMohammad Al-Karim TayasnehMohd Izzad Samir Bin Iskandar

1. AXIAL CAT SCANNER2. COMPUTED TOMOGRAPHY SYSTEM

3. HELICAL CT SCANNER4. MULTISLICE CT SCANNER

5. SPIRAL CT SCANNER6. ULTRAFAST CT SCANNER

7. VOLUME CT SCANNER8. COMPUTED RADIOGARPHY CT SANNER

INTRODUCTION

• A computed tomography (CT) scan is an imaging method that uses x-rays to create pictures of cross-sections of the body.

• What is the different spectrometry CT and scanning system CT?

Block diagram of CT ScanX-tray tube

Detector scanner

Detector

High voltage supply

GantryCamera

O/P unit

DetectorTwo type of detector :

1. Scintillation crystal2. Ionization chamber

Scintillation crystal

Combination of Bismuth germanate crystals with photomultiplier or sodium iodide crystals which is less

afterglow and more efficient

Ionization chamber

Contain xenon gas under pressure which have no afterglow and less efficient.

Have two conductor forming capacitor where high voltage is applied to it. The chamber ionizes the xenon item causing it to

migrate to capacitor plate and causing a current in the high voltage load. This current is proportional to the radiation and

is fed to the computer as data for computing the image.

PRINCIPLES OF OPERATION

• DEMONSTRATION ( Procedure)

TYPES OF CT SCANNERS

• Slip-ring scanners • modern CT scanners are multislice• rows and channels• Three-dimensional (3-D) CT• Four-dimensional (4-D) CT• A dual-source computed tomography (DSCT)

system

IMAGE MANIPULATION

• LET SEE SOME VIDEO

IMAGE QUALITY AND RESOLUTION

• radiation dose, • reconstruction filter• spatial resolution• Z-resolution• Field of view (FOV)

CONTRAST

THICKNESS SLICE AND QUALITY DATA

50 CM IN DIAMETER

Reported Problem

Issue : Controlling the radiation doseProblem : Radiation overdoseSymptoms : hair loss, rashes, headaches,

memory loss, confusion, epilation or patchy hair loss

Consequece : Overdose might cause cancer (epilation is not related to carcinogenic effect)

Reported news1. Increased radiation-induced-cancer risk in pediatric patients

Factor :

Solution : - dose-reduction features geared toward pediatric patients is introduced- Regulatory agencies require CT scanner technicians to use patient size-specific charts- to reduce radiation doses for pediatric patients, reductions in tube current and gantry speed is introduced

scanning children protocol = scanning adult protocol

No difference in patient sizes and transmitted x-ray intensities

Reported news

2. Unexpectedly wide variations in the mean dose delivered to patients for the same studiesCauses : a. unnecessary testing could cause an overexposure to radiationb. System problemsc. communication breakdowns that result in repeat CT scans

2. Unexpectedly wide variations in the mean dose delivered to patients for the same studies

Causes : a. unnecessary testing could cause an

overexposure to radiation

b. System problemsc. communication breakdowns that result in repeat CT scans

Reported news

PURCHASE CONSIDERATION1. Upgrade their CT capabilities

- anticipate a need to upgrade their CT capabilities in the future.- 10-slice CT scanner 16 slices

- 40-slice system 64-slice system

why need to upgrde early?- buying lower-specification equipment and upgrading later will be more expensive

Upgrade to full-spec

2. air-conditioned computer rooms (necessary in some cases)why?- severely compromises the reliability of the scanner system and ultimately shortens its useful life

3. Conditioning the electrical power supply- make artifact-free images often depends strongly on the electrical power

4. Surge suppressors and means for automatic disconnection in the event of power failure must be installed

5. Enviromental considertions- reduce the use of rare metals during construction.

6. Cost considertions

Should purchase service contract

preventive maintenance will be performed at regular intervals

unexpected maintenance costs can be reduced

STAGE OF DEVELOPMENT

• Reduced radiation dose• Improved image quality• Wider coverage (more slices)• Perfusion studies• Interventional CT• Dual-energy CT

BENCHMARK

IPM FREQUENCY