rad 265 introduction to digital radiography

The Field of Digital Radiography Loren Sachs Instructor... What is Digital Radiography?Historically, digital radiography referred to specialized modalities that produced digital images.

The Field of Digital

Radiography

Loren Sachs

Instructor

What is Digital Radiography?

Historically, digital radiography referred to specialized modalities that produced digital images

Examples would include:

– CT

– MRI

– Nuclear Medicine

– Ultrasound

Digital Radiography Today

Since the early 1990s, Digital Radiography has grown to include Computed

Radiography(CR) and ‘true’ Digital

Radiography(DR) or Direct Radiography

Our lecture today will focus on CR and DR

– Volume element This is a 3 dimensional

element that includes depth The pixel is

essentially the end of the voxel.

 Matrix

in rows and columns called a matrix Generally, the

larger the matrix the better the spatial resolution of the image.

 Bit

exponent to two, ie, a 2 bit image is two to the second

or four So the image would have 4 shades of gray

possible Today, most images are 10 or 12 bit.

– Field of view This is how much anatomy is displayed A 12 cm FoV will display 12 cm of anatomy on the screen The smaller the FoV the more magnified the anatomy is.

CR differs from analog in that the CR

cassette contains a phosphor plate instead of

a sheet of film

CR Overview

The Technology of CR

After the cassette is exposed by the x-ray

beam, the cassette is loaded into a reader

The reader removes the phosphor plate and exposes it to a laser, stimulating the

phosphors

The light emitted from the plate is collected, quantified, and digitized

CR Processing

Digital Radiography

DR uses no cassette The image capture device is embedded within the table-top

The advantage here is that the steps

involved in processing a ‘cassette’ are

eliminated resulting in a huge increase in productivity

Studies have estimated a 100% increase in room throughput

DR Overview

Direct Digital Radiography

The photoconductor is made up of

amorphous selenium

Indirect Digital Radiography

The intensifying screen is made up of

cesium-iodide crystals and the

photodetector is made up of amorphous silicon

Which DR Methodology is

Best?

It depends entirely on who you listen to

Basically, different manufacturers are using proprietary technology and claiming theirs

is the best

Ultimately, it will be decided by end-users

DR Issues

The significant disadvantage for DR is cost

Normally, rooms with DR technology have

to be constructed from the ground up

Today, the average DR room cost is

$400,000-600,000 plus construction costs

Construction costs can be overwhelming, particularly in older buildings that need to

be brought up to code

How does CR and DR Affect

You the Technologist?

 RSV is less for both CR and DR when compared

to film/screen combinations Consequently,

techniques are going to be higher.

 Centering and collimation are REQUIRED.

 You gain a tremendous amount of exposure

latitude.

 Post-processing manipulation allows you to adjust film quality.

How does CR and DR Affect

You the Technologist? 2

By selecting processing algorithms you can obtain different anatomical information with one exposure

– A PA chest film and be reprocessed as a PA rib film.

These methodologies are not a panacea for being a ‘bad’ technologist

How does CR and DR Affect the Patient and Medical Care?

 Patient dose goes up with these systems for an

individual exam; however, there are fewer repeats.

 Films are available hospital-wide almost

immediately and can be view in multiple locations simultaneously.

 No films get lost.

 Everyone associated with a patient’s films

becomes more efficient.

Other Considerations

 In order to gain maximum efficiency with CR and

DR a RIS/PACs systems needs to be deployed.

 RIS, Radiology Information Systems, are used to manage non-image patient data, i.e exam number, dictation status, and billing.

 PACs, Picture Archiving Computer, allows for the distribution of images over a pre-described area.

Digital radiography will change the way

technologists practice radiography

However, it will not eliminate the need for a quality education and an understanding of radiology principles In fact, digital

radiography will require additional learning

in order to maximize its usefulness