Lesson 2 (PRELIMS) Flashcards by Justine RRT

The most prominent part of a CT scanner is the _____ – a circular, rotating frame with an X-ray tube mounted on one side and a detector on the opposite side. This tube generates the X-rays that pass through the body and are detected by sensors on the other side.

Gantry assembly
Gantry

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aka “doughnut shape equipment”

Gantry assembly

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It is the opening in the gantry of a CT scanner through which the patient is positioned for scanning. The gantry itself is the rotating frame that holds the X-ray tube and detectors.

Gantry aperture

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Gantry aperture: size for general diagnostic

50-80 cm (20” to 34”)

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The _____ is the central circular opening that allows the patient to pass through it, usually lying on a motorized table that moves them through the scanner. The size of the _____ varies depending on the model of the CT scanner, but it generally needs to be large enough to accommodate the body part being imaged.

Gantry aperture
aperture

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Gantry aperture: size for dedicated machines (radtherapy)

100 cm (39.3”)

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Enumerate gantry aperture considerations

Size
Patient comfort
Scan quality

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Gantry aperture: limits

tilt +/- 30 degree

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Gantry Aperture Considerations: Size: A _____ aperture can accommodate _____ body parts or patients, while a _____ one might be ideal for high-resolution scans of specific areas (such as the brain or heart).

Size
larger - larger
smaller

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Gantry Aperture Considerations: The size of the aperture must be balanced with_____, ensuring that the patient feels at ease during the scan.

Patient comfort

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Gantry Aperture Considerations: A larger aperture may affect the quality of the scan, so _____ in aperture size is important for ensuring accurate imaging.

Scan quality
precision

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Refers to the X-ray tube used in a CT scanner (computed tomography scanner). It is a critical component that generates X-rays, which are used to create cross- sectional images of the body.

CT Tube

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CT Tube: For 80x80 matrix display

Stationary anode with 2mmx16mm focal spot.
120 KVp, 30mA.

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CT Tube: For 512x512 matrix display

Rotating anode with 0.6mmx1.2mm focal spot.
KVp selectable (80, 120, 140), 1000mA.

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CT Tube: _____ thermal capacity.

0.5-5 million Heat Units

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A CT scan _____ is an essential component of a CT scanner. It helps capture the X-ray data that is used to create cross-sectional images (slices) of the body. The _____ works in tandem with an X-ray source to measure the X-rays that pass through the body.

Detection
detector

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The detector consists of an array of _____ or _____ that convert the X-rays(photons) into electrical(digital) signals. These signals are then sent to a computer.

scintillators or photodiodes

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Detectors: Source to Detector Distance

44” (110 cm) modern CT
20-40” (50-100 cm)

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Enumerate detector parameters

Capture efficiency
Absorption efficiency
Conversion efficiency
Detector dose efficiency
Stability
Response time
Dynamic range

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Detector parameters: Efficiency to receive photons. Controlled by detector _____ and _____.

Capture efficiency
size and interspacing

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Detector parameters: Efficiency to convert photons to light or ions. Controlled by detector _____, ______ and _____.

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Absorption efficiency
material, size and thickness

Detector parameters: Efficiency to Convert light or ions to digital signal.

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Conversion efficiency

Detector parameters: Overall efficiency

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Detector dose efficiency
( DDE= CapE + AE + ConE)

Detector parameters: the speed of the detector to react/recognize incoming xray photon and recover for the next input.

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Response time

Detector parameters: the ability to maintain in a quality calibrated state. Fixed detector arrays are the most stable.

5. Stability

Detector parameters: describes the range of x-ray intensities a detector can differentiate. A _____ provides the discrimination between small differences in x-ray attenuation.

7. Dynamic range high dynamic range

Types of detectors

1. Solid state detectors 2. Gas-filled detectors

Types of detectors: Consist of Scintillation Crystals (materials capable of releasing light photons when struct by xray) and Photomultiplier tube. *DDE = _____ *Near _____ Absorption Efficiency *_____ be packed tightly (interspacing), Capture Efficiency is around _____. *Uses Scintillation materials like _____ (_____, but has ______, _____ in Response Time.) *Modern solid state detectors uses _____, _____, _____, _____, _____. _____ Absoption Efficiency, has _____ afterglow, _____ in Response Time.

Solid State Detectors >50% (DDE) 100% (AE) Cannot 50% (Cap E) Sodium Iodide (NaI) 100% AE phosphorescence, decrease Calcium Flouride [CaF2], Bismuth Germinate [Bi4Ge3O12], Cesium Iodide [CsI], Gadolinium Ceramics [Gd], and Calcium Tungstate [CaWO4] 90% AE no increase

Types of detectors: Consist of pressurized Gas-Filled (_____/_____ Gases) Ionization chambers and tungsten electrode plate (_____ apart). Inert gas or noble gas, any of the elements in Group _____ of the periodic table. In order of increasing atomic number they are: _____, _____, _____, ______, _____, _____. *_____ Absorption Efficiency *_____ be packed tightly, Capture Efficiency _____. *_____ Response Time *Highly _____ and must be set in a fixed position oriented to the xray source. *Cannot be used in ___, ____, ___ and _____ scanners

Gas-filled Detector Inert/Noble 1.5mm 18 helium, neon, argon, krypton, xenon, and radon 60-90% AE Can, >90% Cap E Fast Directional 4th,5th,7th and Helical Scanners

A _____ in a CT scanner is a device used to control and shape the X-ray beam as it exits the X-ray tube. Its primary purpose is to ensure that only the necessary portion of the body is exposed to radiation, which improves image quality and reduces unnecessary radiation exposure to the patient.

Collimator

Enumerate key functions of a collimator

1. Beam shaping 2. Reducing scatter radiation 3. Minimizing radiation dose 4. Controlling slice thickness

Key functions of a collimator: The collimator shapes the X-ray beam to match the area of the body being scanned. This ensures that the X-rays are directed only to the specific region of interest, helping to minimize exposure to surrounding tissues.

1. Beam shaping

Key functions of a collimator: Collimators help reduce scatter radiation, which is unwanted radiation that can bounce off tissues and create noise in the image. This improves the clarity and contrast of the final image.

2. Reducing scatter radiation

Key functions of a collimator: By restricting the X-ray beam to the area being scanned, the collimator ensures that only the targeted body area receives radiation, thereby minimizing the overall radiation dose to the patient.

3. Minimizing radiation dose

Key functions of a collimator: In some CT scanners, collimators also influence the thickness of the image slices. This is particularly important in multi-slice CT scanners where thin slices are often required for detailed imaging.

4. Controlling slice thickness

Types of Collimator

1. Pre-patient collimator 2. Post-patient collimator

Types of Collimator: Located between the _____ and the _____, this collimator helps to shape the X-ray beam before it interacts with the body. It is crucial for controlling the size and shape of the beam to cover only the necessary area.

1. Pre-patient collimator X-ray tube and the patient

Types of Collimator: Located _____ the patient, this collimator controls the X- rays that pass through the body and reach the detector. It helps eliminate any scattered X-rays that might contribute to noise or artifacts in the image.

2. Post-patient collimator after

In CT (Computed Tomography) imaging,"_____" and "_____" refer to specific movements of either the X- ray tube or the detector during the scan process

translate/rotate

This refers to the circular movement of the X-ray tube and the detector around the patient’s body. The tube and detector rotate around the body along the __-axis (_____). This allows the scanner to take multiple X-ray images from different angles, which are then used to create detailed cross-sectional images (slices) of the body.

Rotate X horizontal axis

Patient couch/table: Curved (_____), or Flat (_____) Low Z material (_____) Weight Limit (manufacturer’s specs) Typical weight capacity ranging from _____ to _____

General Radiography Radiation therapy Carbon Fiber Graphite 150 kg (330 lbs) to 250 kg (550 lbs)

The CT scan _____ (often referred to as the _____ or _____) is the core component responsible for controlling the entire CT scanning process, as well as _____, ______ and _____ the images produced by the scanner.

Computer CT scanner's computer system or CT imaging workstation processing, reconstructing, and displaying

This refers to the linear movement of the X-ray tube and detector along the body. In a CT scanner, translation often occurs when the patient moves through the scanner during the scan. This movement is typically along the ___-axis (the axis running _____, through the patient’s body).

Translate Z vertically

Key components of computer: Manages the processing power for reconstruction algorithms and system control.

Central Processor (CPU)

Key components of computer: Receives raw data from the detectors and transmits it to the processor.

Data Acquisition System (DAS)

Key components of computer

1. Central processor (CPU) 2. Data acquisition system (DAS) 3. Image reconstruction unit 4. Display workstation 5. Storage system

Key components of computer: Uses mathematical algorithms to convert raw data into usable images.

Image Reconstruction Unit

Key components of computer: Displays images for radiologists, with features for image manipulation and analysis.

Display Workstation

Key components of computer: Stores images and data securely, often in a PACS or cloud-based system.

Storage System

Enumerate functions of the CT scan computer

1. Control of the CT Scanner: 2. Data Acquisition 3. Image Reconstruction 4. Image Display 5. Post-Processing 6. Data Storage 7. Radiologist Workstations 8. Patient Management and Reporting

* As the X-ray tube rotates around the patient and the detectors collect the transmitted X-rays, the computer receives this data in the form of raw data (also called _____). These data points represent measurements of the X-rays that passed through different parts of the body. * The computer also monitors the detector elements (which can be made of scintillator crystals or solid-state detectors) to ensure they are functioning correctly during the scan.

Data Acquisition projections

Lesson 2 (PRELIMS) Flashcards

(51 cards)