4. PACS Fundamentals Flashcards
-electronic version of the radiologist reading room and the file room.
PACS (Picture Archiving and Communication System)
-consists of a digital acquisition, display workstation and storage devices interconnected through an intricate network.
PACS (Picture Archiving and Communication System)
year of the First PACS
1980s
PACS generally served a single modality which is
Ultrasound
Modalities
Ultrasound, MRI, CT scan and more…
-first completed in 1985, this standard laid the groundwork for the future development of the integrated PACS.
DICOM (Digital Imaging and Communications in Medicine)
-is a universally accepted standard for exchanging medical images among the modality, viewing stations, and the archive.
DICOM (Digital Imaging and Communications in Medicine)
-each modality and PACS communicates via _____, and it continues to be refined every year.
DICOM (Digital Imaging and Communications in Medicine)
3 FUNDAMENTAL PARTS OF PACS
- Image Acquisition
- Display Workstations
- Archive Servers
-most images are acquired in a digital format, meaning that the images are inherently digital and can be transferred via a computer network.
Image Acquisition
-Ultrasound (UTZ), computed tomography (CT), magnetic resonance imaging (MRI), and nuclear medicine have been digital for many years and have been taking advantage of PACS far longer than general radiography has.
Image Acquisition
-any computer that a health care worker uses to view a digital image.
Display Workstations
- It is the most interactive part of a PACS, and these workstations are used inside and outside of radiology.
Display Workstations
-has a PACS application software that allows the user to perform minor image-manipulation techniques to optimize the image being viewed.
Display Workstations
Archive Servers are composed of
Database Server or Image Manager,
Short-term and Long-term Storage,
computer that controls the PACS workflow know as: Workflow Manager
computer that controls the PACS workflow
Workflow Manager
-a term that can be used in any industry or in any organization.
Workflow
-It simply means how a process is done, step by step.
Workflow
-In radiology, this term is used to describe how we complete an examination from order entry to transcribed report.
Workflow
-Most departments were designed years ago for film and chemical processing.
Film-based Workflow
-The hardware and software infrastructure of a computer system
System Architecture
System Architecture consists of:
Acquisition devices,
Storage,
Display Workstation, and
Image Management System
-The technologist may get the order via an electronic worklist or a paper requisition, but after that, things begin to change
Generic PACS Workflow
Types of System Architecture
Client/server-based system,
Distributed or stand-alone system,
Web-based system
Client “display workstation” (thin-client)
Client/server-based system (thin-client)
-images are sent directly to the archive server after acquisition and are centrally located
Client/server-based system (thin-client)
-The display workstation functions as a client of the archive server and accesses images based on a centralized worklist that is generated at the archive server
Client/server-based system (thin-client)
-The health care worker at the display workstation chooses a name from the central list, and the archive server sends the image data to display station. After the “client” is finished, the image data are flushed from its memory.
Client/server-based system (thin-client)
-Most systems allow basic image manipulation at the display workstation or “client,” and the changes are saved on the archive server.
Client/server-based system (thin-client)
-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)
Distributed or stand-alone system (thick-client)
-is very similar to a client/server system in how data flow.
Web-based system
-The significant difference is that both the images and the application software for the client display are held centrally
Web-based system
is a term used to describe the reading of images from outside of the hospitals walls.
Teleradiology
uses large multi viewer lightboxes to display the images
conventional film/screen radiography
DISPLAY WORKSTATION CONSISTS OF:
monitor,
a computer with a mouse and keyboard.
monitor used in cross sectional images (ct san)
1k monitor
monitor used in cr/dr projection
2k monitor
highest resolution monitors (mammography)
5k monitor
basic picture element on a display
Pixel
number of pixels contained on a display
Resolution
rectangular or square table of numbers that represents the pixel intensity to be displayed inn a monitor
Matrix
Display stations can be categorized by their primary use:
primary reading stations for radiologists,
review stations for referring physicians,
technologist quality control (QC) stations
-used by a radiologist when making a primary diagnosis.
Reading stations- radiologist
The reading station has the ________ hardware, including the _____ monitor
highest quality,
best,
-is a step-down model of the radiologist reading station.
Review station- referring physicians
-use the same level of software with the reading station but may eliminate some of the more advanced functions.
Review station- referring physicians
One of the most important features on a physician review station is
the ability to view current and previous reports along with the images
One of the greatest advantages of a PACS
is the ability to view the same set of images in multiple locations at one time.
-used to review images after acquisition but before sending them to the radiologist.
Technologist quality work station
may be used to improve or adjust image quality characteristics
Technologist quality work station
-it may be used to verify patient demographic information
Technologist quality work station
Before PACS, the file room was a
large open room with endless rows of shelves full of film jackets/envelopes
Today a file room in a PACS environment may be simple as
a couple of computers and a dry laser to make copies for outside needs.
-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
File Room Workstation
-are used to move through images, series, studies, and patients.
Navigation functions
Commonly used functions in General Radiology
Navigation functions,
Image manipulation and enhancement functions,
Image management functions
Most modern PACS software conforms to the look and feel of the
Windows (Microsoft, Redmond, WA)
how a set of images will be displayed on the monitor
Hanging Protocols
current or previous examination being viewed
Study Navigation
may comprise two or three single images such as the case with CR and DR (projection radiography), or it may contain several series of images such as the case with MRI.
Study Navigation
In studying function, Images can paged through either:
- Scroll wheel (mouse)
- Arrows on keyboard
- Cine
stack mode of scrolling
Cine
Cine comes from the word
Cinematic
it means to move through frame by frame of the series of images
Cinematic
Navigation tool that is commonly found is
close patient or close study icon
this icon closes the active patient or study and either pulls up the worklist or moves to the next unread patient in the worklist.
Close patient or close study icon
-default function of the left mouse when an image is actively displayed in the software
Window/level
-this function should NOT be used to label left or right to indicate the patient’s side because digital R and L will not hold up in court
Annotations
-can indicate prone or supine, 30 minutes, upright or flat plate
Annotations
-These functions are used to orient the image in the anatomical hanging position
Flip and rotate
This function makes it very important that lead markers are used to ensure that the radiologist reads the correct side.
Flip and rotate
These functions are used primarily by the radiologist to increase the size of an area on the image.
Pan, zoom, and magnify
-Usually used together
Pan, and zoom
will usually enlarge a square area of the image, and the square can be moved around the image to quickly see various areas enlarged.
Magnify
most common measurements
Distance measurement
size of the pixel
the known measurement
another common measurement which measures the angle between two structures
Angle measurement
it is commonly used in spine studies
Angle measurement
Common measurement for radiologist
ROI (region of interest)
It will determine the pixel intensity of a certain area.
ROI (region of interest)
used to retrieve studies from the archive
Query/retrieve function
allows the user to query a study on multiple fields such as the patient’s name or ID, date of service, or modality
Query/retrieve function
most commonly used three-dimensional (3D) rendering techniques.
Multiplanar reconstruction (MPR)
most common application is producing coronal images from the axial set to reduce radiation to the patient and scan time at the modality
Multiplanar reconstruction (MPR)
used to visualize vessels
Maximum Intensity Projection (MIP)
air-filled structures
Minimum Intensity Projection (MinIp)
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
Volume rendering technique (VRT)
The technique uses a histogram-type graph to differentiate the various structures
Volume rendering technique (VRT)
-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.
Shaded surface display (SSD)
Used when multiple images need to be put together into one image
Stitching
Stitching is commonly used for
full-spine x-rays or
scoliosis series,
long bones (extremities)
advanced function of the workstation, such as edge enhancement, smoothing, and contrast enhancements
Image postprocessing
examples of image post processing
edge enhancement, smoothing,
contrast enhancements
4 CATEGORIES OF COMMON FUNCTIONS ON A PACS WORKSTATION
Navigation functions,
Image manipulation and enhancement functions,
Image management functions,
Advanced workstation functions
Navigation functions
Hanging Protocols
Study Navigation
Image manipulation and enhancement functions
Window width Annotations Flip and rotate Pan, zoom and magnify Measurements
Advanced workstation functions
Reading station advanced functions,
Technologist QC station advanced functions
Reading station advanced functions
Multiplanar reconstruction (MPR)
Maximum intensity projection (MIP) and Minimum intensity projection (MinIp)
Volume rendering technique (VRT)
Shaded surface display (SSD)
Technologist QC station advanced functions
Stitching
Image postprocessing
Cardiothoracic ratio
(0.42-0.50)
Carina distance – endotrachealtube ETP (distance measurements)
(2.5 cm) (4 cm/3-5 cm)
represents the range of gray values that are being viewed
Window
represents the center value of the range
Level
ADVANTAGES OF CLIENT/SERVER-BASED SYSTEM
- Any examination sent to the PACS is available anywhere without other interventions.
- Only one person can open the study and others that open it will receive a message that the study is open and being read.
- There is no need to pull or send historic images because the old studies are available with the new on the archive.
DISADVANTAGES OF CLIENT/SERVER-BASED SYSTEM
- The archive server is seen as a single point of failure. If the archive goes down, the entire system is down, and no image movement can take place. All newly acquired images must remain at the modality until the archive is up and can again receive the images.
- The system is very network dependent. The images are flying back and forth between the archive and the workstations, and the network can become bogged down because of the large volume of data being moved.
- The archive server is handling many requests at once and can become bottlenecked because of the high volume of requests
ADVANTAGES OF DISTRIBUTED OR STAND-ALONE SYSTEM
- If the archive server goes down, local reading at the workstations is not interrupted, other than not being able to get historic images. After the archive comes back up, the images that have been changed and signed off by the radiologist will automatically be forwarded to the archive to be saved.
- Copies of an examination exist at various locations because the images can be distributed to many locations at once. Therefore it is less likely that PACS data will be lost.
- The system is less dependent on the network for its speed. The user can be working on one examination while the workstation is pulling and getting the next examination ready to be read. The workstation can fetch historic images according to rules the user sets up.
DISADVANTAGES OF DISTRIBUTED OR STAND-ALONE SYSTEM
- There is heavy reliance on the assumption that the distribution of images is being done correctly. If the distribution is wrong, the prefetching of historic examinations will not be correct either.
- Each workstation has a different worklist, and therefore only one person can be working on that list at a time.
- It can be inconvenient to read additional studies; the radiologist would have to move to another workstation to read the images designated for that workstation.
- The users must depend on the query-and-retrieve function when nonscheduled examinations arrive at the workstation to be read.
ADVANTAGES OF WEB-BASED SYSTEM
- The hardware at the client can be anything that will support an appropriate web browser. This allows for greater flexibility with hardware but can also be a disadvantage because image displays (monitors) may not be able to support diagnostic quality.
- The same application can be used on site and at home in teleradiology situations.
DISADVANTAGES OF WEB-BASED SYSTEM
- The system’s functionality may be limited because the software is not installed locally. The bandwidth of the network connection limits the amount of data that can be transmitted for download, and some programs are too large to be transmitted over the network that is installed.
- As with client/server systems, the network is the biggest obstacle to performance
