RAD 255 - Test 4 - Digital Imaging

latent

A digital image is converted from a ____ image from numerical data by the computer.

CT

What is the first imaging modality to rely solely on a computer (digital imaging) to form the image?

Matrix - location; Pixel - shade of grey

How is a digital image is displayed? (Hint-involves the terms matrix and pixel)

pixel

What stands for Picture Element the digital image is made up of these tiny squares consisting of different brightness levels or shades of gray?

matrix

What is a layout of cells (pixels) in rows and columns?

Matrix of Pixels

A digital image is often referred to as a " _______ __ _________."

small, many, many

To obtain a digital image that more closely resembles an analog image:

- pixel size should be ____

- _____ pixels should comprise the image

- there should be ______ shades of gray available to form the image

- Rapid image acquisition

- Enhanced image contrast

- Postprocessing options

- Digital subtraction angiography (DSA)

What are some advantages of digital fluoroscopy over conventional fluoroscopy?

"Scanned Projection Radiography"

What is the following CT System?

- A filmless digital radiography system

- has an array of radiation detectors replaces the conventional cassette

- Fan shaped x-ray beam

- Prepatient & post patient collimators

- Tube and detector array translate across the patient during the exposure

- Detectors measure radiation and send electric signal to computer to construct image

Dual Energy Imaging

What is the special application for Scanned Projection Radiography that takes 2 images?

one with high contrast - for bony detail

one with low contrast - for soft tissue

chest lesions

What is Dual Energy Imaging useful for?

X-ray beam is pulsed rapidly during the exposure alternating between 140 & 60 KVP

How does Dual Energy Imaging work?

1. Instantaneous processing time (DR)

2. Less expensive in long run - no film (CR)

3. Less scatter - improved contrast resolution

4. Less physical storage space required

5. Manipulation of images possible

6. Can reduce radiation exposure (not always)

7. post- processing reduces repeats

8. DR systems require less exposure than film or CR

What are some advantages of obtaining a radiographic image through the digital process, as opposed to the conventional film imaging process?

Picture Archiving and Communication System

What does the acronym "PACS" stands for?

computer storage replaces hard copy film for filing radiographic images

What is the PACS system?

system can send images to distant sites

What are the advantages of the PACS system?

post-processing

What the method of enhancing the computerized image to display diagnostic information more clearly, without re-exposing the patient?

Annotation

Image subtraction

Pixel Shift

Edge enhancement

Windowing

Window Level Adjustment

Window Width Adjustment

Image rotation

(and more!)

What are some examples of "post-processing" techniques?

Edge Enhancement

What is the post-processing technique?

The computer changes the pixel values around the edges of a structure to increase contrast along the edges to make it more visible.

- Fractures

- High contrast structures

Smoothing/Equalization

What is the post-processing technique?

The computer averages out pixel values across the image, resulting in less variation in brightness and a clearer delineation of the structure

Light areas are made darker and dark areas are made lighter

Smoothing can be used to mask noise

Hounsfield unit (HU).

What is the term for each voxel is assigned a number by the computer based on its density?

+1000

What is the Hounsfield unit (HU) for dense bone?

0

What is the Hounsfield unit (HU) for water?

-1000

What is the Hounsfield unit (HU) for air?

directly related (bigger matrix = better spatial resolution)

How are matrix size and spatial resolution related?

window level

How can the brightness of a digital image be altered, once the exposure is made and the image acquired?

window width

How can the contrast of a digital image be altered, once the exposure is made and the image acquired?

Narrow Window Width = Increased Contrast

Wide Window Width = Decreased Contrast

How are window width and contrast related?

Increased Window Level = Increased Brightness

Decreased Window Level = Decreased Brightness

How are window level and brightness related?

using proper technique (not underexposing)

What is the best way to ensure that digital images have the optimum brightness (exposure) and contrast and are free of "noise" or quantum mottle?

DR - less expensive in the long run

CR - more expensive in the long run (film)

What is the difference in expense (in the long run) between the DR and CR Digital Radiography Systems?

DR - conventional equipment must be replaced

CR - uses existing equipment

What is the difference in ease of converting between the DR and CR Digital Radiography Systems?

DR - gives image right away

CR - have to run back and forth from reader to get an image

What is the difference in use on portables between the DR and CR Digital Radiography Systems?

barium fluorohalide

What material comprises the photostimulable phosphor in a CR imaging plate?

red laser

What is scanned across the IP to release the latent image energy, and what is used to erase the plate?

underexposed

Fugi "S" numbers greater than 500 are considered ___________.

overexposed

Fugi "S" numbers less than 25 may be grossly _________.

Direct-Capture Radiography OR Direct Readout Radiography

What does DR stand for?

Computed Radiography

What does CR stand for?

Amorphous Selenium (a-Se)

Thin Film Transistor (TFT)

What are the components used to construct a direct conversion detector?

Cesium Iodide

Fiber Optics

CCD or CMOS

What are the components used to construct an indirect conversion detector? (CCD?CMOS)

Cesium Iodide or Gadolinium Oxysulfide

Amorphous Silicon (a-Si)

Thin Film Transistor (TFT)

What are the components used to construct an indirect conversion detector? (TFT)

Digital Imaging and Communications in Medicine

What does DICOM stand for?

Hospital Information System

What does HIS stand for?

critical to allow radiologists to quickly access patent information, regardless of where that information resides

Why must PACS be networked with HIS and RIS systems?

Radiology Information System

What does RIS stand for?

A universally adopted standard for interchange of medical images

What does DICOM do?