RT202: MODULE 3 - PACS (Picture Archiving Communication System)

PACS (Picture Archiving Communication System)

electronic version of the radiologist reading room and the file room.

- It is a medical imaging technology that provides economical storage and convenient access to images from multiple modalities, replacing conventional films with digital images.

Early PACS

The first PACSs were used in the early 1980s and generally served one single modality

Digital Imaging and Communications in Medicine (DICOM)

the standard foundation for imaging & image management

First completed PACS

1985, this standard laid the groundwork for the future development of integrated PACS

PACS into its three fundamental parts:

image acquisition
display workstations
archive servers.

image acquisition

- is the first point of data entry into a picture archiving and communications system (PACS),

display workstations

is any computer that a health care worker uses to view a digital image.

archive servers

• is the file room of the PACS.
• It is composed of:
o database server or image manager
o short-term and long-term storage,
o workflow manager (a computer that controls the PACS workflow)

WORKFLOW

a term that can be used in any industry or in any organization. It simply means how a process is done, step by step

System architecture

defined as the hardware and software infrastructure of a computer system.

COMMON PACS ARCHITECTURE

Client-based system
Distributed or stand-alone system
Web-based system
Display workstation

Client-based system

• thin client (dependent to the archive)
• images are sent directly to the archive server after acquisition and are centrally located.

Distributed or stand-alone system

the acquisition modalities send the images to a designated reading station and possibly to review stations, depending on where the order originated (i.e., ICU or ER)

Web-based system

is very similar to a client/server system in how data flow

- This means that when someone wants to view images from a web-based application, he or she simply searches for the pertinent images and the web browser

Display workstation

consists of a monitor and a computer with a mouse and keyboard.

Monitor

is one of the most important elements of a PACS display station.

LCD (liquid crystal display)

• is the most popular type of monitor used in a radiology department, with the cathode ray tube (CRT)

Monitor Resolution

-cross-sectional images - 1K square monitor
-CR/DR digital projection - 2K portrait monitor
-highest resolution monitors - 5k monitor
- mammography requires a 5K or 5-megapixel resolution to provide the viewing capacity needed

PIXEL

Basic picture element on a display

RESOLUTION •

-Process or capability of distinguishing adjacent parts
- Number of pixels contained on a display

MATRIX

Rectangular or square table of numbers that represents the pixel intensity to be displayed in a monitor

Common Screen Resolutions that are found on today's monitors

1280 x 1024 (1K), 1600 x 1200 (2K), 2048 x 1536 (3K), 2048 x 2056 (5K)

Display stations can be categorized by their primary use:

Reading station
Review workstation
Technologist quality control station
File Room/Image Management Stations

Reading station

is used by a radiologist when making a primary diagnosis.

Review workstation

Ability to view current & previous reports along with the images which can only be accomplished with the integration of RIS functions with the PACS software.

Technologist quality control station

used to review images after acquisition but before sending them to the radiologist.

File Room/Image Management Stations

may be used to look up examinations for a physician or to print copies of images for the patient to take to an outside physician.

Common Functions

All of the functions should be available on any level of the workstation except for the advanced functions, which are specific to different types of workstations.

Common Functions consist:

Navigation functions
Hanging Protocols
Study Navigation

Navigation functions

Are used to move through images, series, studies, and patients.

Hanging Protocols

user has the ability to arrange a certain number of images per monitor per modality

Study Navigation

is the current or previous examination being viewed.

CINE

-Stack mode of scrolling
-Used most often in sectional imaging

Image Manipulation and Enhancement Functions

Window width/window level
Annotations
Flip and rotate
Pan, zoom, and magnify
Measurements

Window width/window level

This is usually a default function of the left mouse button or middle scroll wheel when an image is actively displayed in the software.

Annotations

This function should not be used to label left or right to indicate the patient's side; digital R and L will not hold up in court because of the ability to mark anywhere on the image and flip and rotate the image into any layout on the screen.

Flip and rotate

These functions are used to orient the image in the anatomic hanging position

Pan, zoom, and magnify

These functions are used primarily by the radiologist to increase the size of an area on the image.

Measurements

Various measurement functions are found on a PACS station.

-The most common is the distance measurement. o CTR (ratio) is calculated by dividing the cardiac diameter by the thoracic diameter

Image Management Functions

patient demographics
query/retrieve function
CD-burning option
copy and paste images
print films

patient demographics

Most PACSs allow the user to modify patient demographics. It is imperative that the patient demographics are correct.

query/retrieve function

used to retrieve studies from the archive

CD-burning option

Many vendors have provided a CD-burning option that allows users to save studies to a CD for outside use

copy and paste images

This is frequently used with the web-based systems when creating presentations for conferences.

print films

Some hospitals have retained the ability to print films for outside use. This is also usually done only in the file room so that control can be maintained over the printed films.

Advanced Workstation Functions

are usually placed on specialty workstations for the radiologist, but some are found on the technologist QC station to further enhance the images.

Reading Station Advanced Functions

Multiplanar reconstruction (MPR)
Volume rendering technique (VRT)
Shaded surface display (SSD)

Multiplanar reconstruction (MPR)

allow the radiologist to view several different anatomic planes from the original acquired sagittal images

-most commonly used three-dimensional (3D) rendering techniques.

Volume rendering technique (VRT)

Similar to MIP but allows the user to assign colors based on the intensity of the tissue so that bone, contrast agent, and organs can be seen in different colors

Shaded surface display (SSD)

Using a threshold of pixel intensity values, everything below the threshold will be removed, and everything above will be assigned a color and shown as a 3D object.

(MIP) Maximum intensity projection

Used to visualize vessels

(MinIp) minimum intensity projection

air-filled structures

Stitching

Used when multiple images need to be put together into one image.