Digital Imaging Modalities and PACS PDF

Digital Imaging Modalities and PACS AMRR 24 D r. H u da A l mabadi Part IV :PACS Fundamentals • Image Acquisition • Display Workstations • Archive Servers • Workflow Today Lecture Will: 1. The picture archiving and communication system (PACS) is becoming more commonplace in today’s hospitals be...

Digital Imaging Modalities and PACS AMRR 24 D r. H u da A l mabadi Part IV :PACS Fundamentals • Image Acquisition • Display Workstations • Archive Servers • Workflow Today Lecture Will: 1. The picture archiving and communication system (PACS) is becoming more commonplace in today’s hospitals because hospital administrators have come to see the necessity of having such a system to serve physicians and patients even though the cost is great. 2. The initial capital cost is great, but the benefit of having the system far out- weighs the cost. Outlines the basic concept of a PACS and its components, common PACS architecture, and typical PACS workflows that may be seen in a hospital. Objectives 1. Define picture archiving and communication system (PACS). 2. Compare and contrast the various types of PACS display workstations. 3. Differentiate among the different types of digital imaging workflow. 4. Define system architecture and recognize the three major models. 5. Summarize the common functions found on a PACS workstation. 6. Describe the situations and users that may require advanced PACS workstation functions. KEY TERMS Archive Client/server-based system Digital imaging and communications in medicine (DICOM) Display workstation Distributed or stand alone system File room workstation Hanging protocol Navigation functions Picture archiving and communication system (PACS) Quality control (QC) station Reading station Review workstation Softcopy System architecture Teleradiology Web-based system Workflow Fundamentals 1. As discussed in lect 1, a PACS consists of digital acquisition, display workstations, and storage devices interconnected through an intricate network 2. The PACS is an electronic version of the radiologist reading room and the file room. 3. The first PACSs were used in the early 1980s and generally served one single modality. 4. Large research institutions housed early systems because most were developed by the scientists who worked at those institutions. 5. As vendors became more involved, they developed proprietary systems that were very specific to their modalities. Christi E. Carter and Beth L. Vealé. Digital Radiography and Pacs. 2010 by Mosby, Inc 6. Finally, as physicians and hospitals became interested, it was determined that there must be standardization. Digital imaging and communications in medicine (DICOM) is a universally accepted standard for exchanging medical images among the modality, viewing stations. and the archive To understand what a PACS is and how it is used, the following sections break down a PACS into its three fundamental parts : image acquisition, display workstations, and archive servers. Each of these topics is covered in depth in coming chapters(lectuers) . Image Acquisition 1. 2. 3. 4. 5. In modern radiology departments, most images are acquired in a digital format, meaning that the images are inherently digital and can be transferred via a computer network. Ultrasound, 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. As stated earlier, the first PACS served a single modality, namely, ultrasound. Ultrasound mini-PACS networks were the norm in many hospitals. Radiologists routinely made diagnoses by looking at images on the modality’s computer screen. It was a natural step from there to convert ultrasound to softcopy reporting, i.e., reading images on the computer without hardcopy films. Christi E. Carter and Beth L. Vealé. Digital Radiography and Pacs. 2010 by Mosby, Inc Image Acquisition 1. As the CT and MRI image sets became larger because of the increased number of cross-sectional images per patient, radiologists routinely went to the modality to view the images. 2. This slowed down the scanning process for the technologists, 3. and vendors began getting requests for extra console stations for radiologist viewing. 4. These workstations were directly connected to the modalities. 5. Radiologists could view the large stacks of images and perform simple image manipulation. 6. These workstations morphed into mini-PACS and eventually into full-blown systems for CT and MRI. Display Workstations 1. A display workstation is any computer that a health care worker uses to view a digital image . 2. It is the most interactive part of a PACS, and these work- stations are used inside and outside of radiology. 3. The display station receives images from the archive or from the various radiology modalities and presents them for viewing. 4. The display workstation has PACS application software that allows the user to perform minor image -manipulation techniques to optimize the image being viewed. 5. Some display stations have advanced software to perform more complex image-manipulation techniques. Archive Servers 1. 2. 3. 4. An archive server is the file room of the PACS. It is composed of a database server or image manager, short-term and long-term storage, and a computer that controls the PACS workflow, known as a workflow manager . The archive is the central part of the PACS and houses all of the historic data along with the current data being generated. In many institutions the archive serves as the central hub that receives all images before being released to the radiologists for interpretation. https://simple.wikipedia.org/wiki/Software Workflow 1. 2. 3. 4. 5. Workflow is a term that can be used in any industry or in any organization. It simply means how a process is done, step by step. In radiology, we have always used the term workflow to describe how we complete an examination from order entry to transcribed report. This section describes a generic film-based workflow and then compares it with a generic PACS workflow. The workflow in each radiology department is different because there are many variables. Christi E. Carter and Beth L. Vealé. Digital Radiography and Pacs. 2010 by Mosby, Inc Film-Based Workflow Most departments were designed years ago for film and chemical processing. Pass boxes were built into walls that fed into darkrooms and into large open reading rooms that had multiviewer lightboxes lining the walls . Eventually chemical processing time decreased from a few minutes to less than 60 seconds in some cases. As film and processing technology advanced, workflow became more efficient, despite having to still hand deliver film to radiologists and to make the occasional copy for a referring physician. Christi E. Carter and Beth L. Vealé. Digital Radiography and Pacs. 2010 by Mosby, Inc The following list outlines a typical workflow in a radiology department, from entering the order to transcribing the report The first step in any radiology department workflow is the entry of the order. The order may be a paper prescription from the ordering doctor, or the order may have been placed in the computer system by the emergency room (ER) or intensive care unit (ICU) staff. Either way, an order is placed in the radiology information system (RIS), and a requisition is generated. A requisition generally contains the following information: ● Patient’s name ● Patient’s hospital identification (ID) number ● Date of birth ● Ordering physician’s name ● Examination ordered ● Reason for examination ● Chief complaint Christi E. Carter and Beth L. Vealé. Digital Radiography and Pacs. 2010 by Mosby, Inc The paper requisition is then passed on to the technologist who will be performing the examination. The technologist prepares the room for the patient and brings the patient back to the room. The technologist verifies all of the patient’s information and completes a patient history. The technologist also inquires whether the patient needs a complete set of copies to take to the next doctor’s appointment. The technologist performs the examination and processes all of the film after the complete examination is done. The technologist critiques each film and repeats exposures as necessary. Christi E. Carter and Beth L. Vealé. Digital Radiography and Pacs. 2010 by Mosby, Inc The technologist makes copies if necessary and releases the patient with the films. The technologist goes to the file room to find the film jacket with all of the patient’s historic images, if applicable. The film jacket may not be located on site and may be kept at an off-site storage location. The film jacket is ordered to be picked up by the film courier. The film jacket arrives a couple of hours or even days later, and the current films are hung on a multiviewer lightbox to be read by a radiologist. The file room clerk may hang a set of historic images from the film jacket for comparison. The radiologist reads the films and dictates a report into the dictation system. The multiviewer lightbox is cleared of read films by the file room clerk, and the films are placed back into the film jacket. The film jacket is filed in the file room. A transcriptionist retrieves the recorded dictation and transcribes a report into the RIS. This may occur later that same day or the next day. The radiologist reviews the report, makes corrections, and signs the report as final. The final report is printed and placed in the patient’s film jacket along with any previous reports. A final report is also sent to the ordering physician for review. This final report may come several days after the examination was completed. Christi E. Carter and Beth L. Vealé. Digital Radiography and Pacs. 2010 by Mosby, Inc Generic PACS Workflow The PACS workflow is in many ways different from the film-based workflow . The technologist may get the order via an electronic worklist or a paper requisition, but after that, things begin to change. 1. Changes in the order entry are on the horizon, but for now, the order-entry process is the same as in film-based departments. 2. The technologist needs a requisition to verify the patient ID and to take a patient history. 3. The order is input into the RIS, and the RIS sends a message to the PACS to find all historic images and put them on the short-term archive. This eliminates wait- ing for the file room to retrieve a film jacket from the off-site storage location. Christi E. Carter and Beth L. Vealé. Digital Radiography and Pacs. 2010 by Mosby, Inc 4. The technologist performs the examination, and depending on the type of image acquisition device, the images are processed and repeated as necessary and sent to the appropriate PACS device. The patient images have been tagged with information from the RIS so that historic image reports are available at the PACS when the new images are sent. 5. The requisition is either taken to the radiologist, or the radiologist may pull the images from an electronic worklist. 6. The radiologist also pulls up historic images and reports and compares the previous images with the current images. 7. The radiologist dictates a report and has it transcribed, or voice recognition software may be used. 8. If the radiologist uses voice recognition software, he or she can review the report right after dictation, make corrections, and sign the report, making it final. https://computer.howstuffworks.com/motherboard4.htm System Architecture System architecture can be defined as the hardware and software infrastructure of a computer system. In a PACS, the system architecture normally consists of acquisition devices, storage, display workstations, and an image management system. The following discussion outlines three common PACS architectures and takes a look at the flow of images after acquisition. 1.Client/Server-based Systems • in a client/server-based system, images are sent directly to the archive server after acquisition and are centrally located . • 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. • 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. • Most systems allow basic image manipulation at the display workstation or “client,” and the changes are saved on the archive server. Advantages •Any examination sent to the PACS is available anywhere without other interventions. •Only one person can open the study with the intent to read it. Others that open •the study will receive a message that the study is open and being read. •There is no need to pull or send historic images to a particular workstation because •the old studies are available with the new on the archive. Disadvantages • 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 bottle- necked because of the high volume of requests. 3. Distributed Systems • a 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). • In some systems, the images are sent from the modality to the archive server, and the archive server distributes the images to the designated workstation. • The reading station designations may be designed based on radiologist reading preferences. For example, MRI may be sent to one station and CT to another, or all cross-sectional neurological images may be sent to one station but all body imaging are sent to another. • The designation is decided after extensive workflow observation. • Moreover, in a distributed model, the workstations can query and retrieve images from the archive. • All images are then stored locally and then are sent to the archive server after they have been read. • These images remain on the local hard drive of the workstation until they are deleted either by a user or by system rules. Advantages •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 be forwarded automatically to the archive to be saved. •Because the images can be distributed to many locations at once, copies of an examination exist at various locations, 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 •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. • It is also possible for two radiologists to be reading the same examination and not know that the other has it until they try to start dictation. The paper requisition is very important with this type of PACS. Web-based Systems A web-based system is very similar to a client/server system in how data flow. The significant difference is that both the images and the application software for the client display are held centrally . In a client/server system, the client still has application software locally loaded to the client, and only the images are held at the archive. Advantages •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 disadvan- tage 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. Teleradiology is a term used to describe the reading of images from outside of the hospitals walls. It can be down the road at the radiologist’s home or on the other side of the world during nighttime hours. Disadvantages 1.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. 2.As with client/server systems, the network is the biggest obstacle to performance Display Workstations The display workstation is the most interactive part of a PACS, consisting of a monitor and a computer with a mouse and keyboard. In addition, each system has hardware that fits the users’ requirements. we know, conventional film/screen radiography uses large multiviewer light- boxes to display the images . Early in the history of PACS, radiologists believed that they needed four to six monitors to match the viewing capability they had with the lightboxes. As the radiologists have become more comfortable viewing images on monitors, the number of monitors required by the radiologists has decreased to an average of two . This decrease can also be attributed in part to the continued development of viewing software and better hardware, namely, mice. • The monitor is one of the most important elements of a PACS display station. • The cathode ray tube (CRT) and the liquid crystal display (LCD) are the most popular types of monitors in a radiology department. • The LCD has decreased in price and increased in quality during the past few years and will soon take over the entire PACS display market because of its size, resolution, and lack of heat production. • The LCD also requires less maintenance, gives out more light, and can be used in areas with a high amount of ambient light. • In early PACS reading rooms, supplemental air conditioning had to be installed to offset the heat put out by multiple CRTs. • Along with the number of monitors used, the resolution and orientation of the monitor are also factors in determining which type of monitor to buy for each workstation. • Most cross-sectional imaging is read on a 1K square monitor (Figure 8-15), and most CR and DR are read on at least a 2K portrait monitor • Remember from Chapter 2 that a basic picture element on a display is known as a pixel. • The number of pixels contained on a display is known as its resolution. • The relationship between pixels and resolution can be stated as follows: the more pixels in an image, the higher the resolution of the image, and the more information that can be displayed. • Resolution can also be defined as the process or capability of distinguishing between individual parts of an image that are adjacent. • Pixels are arranged in a matrix. • A matrix is a rectangular or square table of numbers that represents the pixel intensity to be displayed on the monitor. • Common screen resolutions that are found on today’s monitors are 1280 × 1024 (1K), 1600 × 1200 (2K), 2048 × 1536 (3K), and 2048 × 2560 (5K). Medical displays are generally of a higher quality than displays used for other applications. Radiologists often use the highest resolution monitors available for the modality that is being read. For example, mammography requires a 5K or 5-megapixel resolution to provide the viewing capacity needed, but a cross-sectional image requires only a 1K monitor to view the necessary information. Because a referring physician is not the primary doctor reading the examinations, a 1K monitor would be sufficient for his or her viewing needs. Display stations can be categorized by their primary use: • primary reading stations for radiologists, • review stations for referring physicians, • technologist quality control (QC) stations where technologists review images, • and image management stations for the file room personnel. Each of these workstations has one specific main purpose and is strategically located near the end-user of its designated purpose. Radiologist Reading Stations • The radiologist reading station is used by a radiologist when making a primary diagnosis. • The reading station has the highest quality hardware, including the best monitor. • The computer hardware meets the needs of the PACS vendor, but it will usually be very robust, requiring little downtime. The keyboard and mouse can be customized. • There are many different styles of mice available that can increase the efficiency of the software being used • There is generally access to a nearby RIS, with a dictation system near or even connected to the PACS station. Many PACSs have software that integrates the RIS and dictation system. Physician Review Stations The physician review workstation is a step-down model of the radiologist reading station. Many vendors use the same level of software but may eliminate some of the more advanced functions. One of the most important features on a physician review station is the ability to view current and previous reports along with the images. This can be accomplished with the integration of RIS functions with the PACS software mentioned above. Most referring physicians want to read the radiologist’s report along with seeing the patient’s images, and often the report is more important to them than the images . The software may either be loaded on a stand-alone station that is dedicated to viewing images, or it may be delivered over a web browser on any personal computer (PC) within an office or on a floor. In high-volume areas such as the ER and ICU there are dedicated PACS workstations for image viewing. These dedicated stations may have the higher-end monitors like the radiologist reading stations, but many may have lower-end monitors because of cost constraints. One of the greatest advantages of a PACS is the ability to view the same set of images in multiple locations at one time. In the film/screen era, referring physicians would make the trek to the radiology department to consult with a radiologist about a patient’s image, hoping that the films would be found in the file room and that the radiologist was available to consult. Now with PACS, the referring physician can pull up the patient’s images in his or her office and read the radiologist’s report. The refer- ring physician and the radiologist can consult on the telephone while looking at the images simultaneously. This is one way that PACSs have improved continuity and speed of patient care. Technologist QC Stations The technologist QC station is used to review images after acquisition but before sending them to the radiologist. The QC station may be used to improve or adjust image quality characteristics, or it may be used to verify patient demographic information. Many QC stations are placed between the CR and DR acquisition modalities as a pass-through to ensure that the images have met the departmental quality standard. The technologist QC station generally has a 1K monitor. When manipulating images, the technologist must be careful not to change the appearance too much from the original acquired image. The technologist should consult fre- quently with the radiologist to ensure that the images being sent are of the required quality. The QC workstation can also be used to query and retrieve historic images before beginning an examination so that the technologist can check previous pathology or body characteristics. This can help with the selection of technical factors or procedural protocol. It is common protocol in a film-based department to pull film jackets on patients before performing an examination. The QC station affords the same benefit as pulling the film jacket. File Room/Image Management Stations The file room in a PACS environment has seen many changes in the past few years. Before PACS, the file room was a large open room with endless rows of shelves full of film jackets. Today a file room in a PACS environment may be as simple as a couple of computers and a dry laser to make copies for outside needs. The file room workstation 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. Many hospitals are moving away from printing films to save the cost of the film and are instead moving toward burning compact disks (CDs) with the patient’s images because they are less expensive. The CD of images can be viewed on any PC and generally comes with easy-to-use software burned onto it with the images. Common Functions • This section provides an overview of common functions found on a PACS workstation. • 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. • The functions can be broken down into four categories: navigation functions, image manipulation and enhancement functions, image management functions, and advanced workstation functions. •There are many functions available on a PACS workstation, and each set of functions can be broken down into four categories: navigation functions, image manipulation and enhancement functions, image management functions, and advanced workstation functions The file room may also be responsible for correcting patient demographics. If images with incorrect demographics are sent to the archive, then it is difficult to pull those images the next time the patient comes in for an examination. The archive is a database and is only as good as the information that is put into it. summary •A PACS consists of digital acquisition, display workstations, and storage devices interconnected through an intricate network. •DICOM is a universally accepted standard for exchanging medical images between the modality, viewing stations, and the archive. •A display workstation is any computer that a health care worker uses to view a digital image, and it is the most interactive part of a PACS. •The archive is the central part of the PACS and houses all of the historic data along with the current data being generated. •Workflow is how a process is done step by step or how a task is completed. •System architecture can be defined as the hardware and software infrastructure of a computerized system. •Common system architectures found with a PACS are client/server-based systems, distributed or stand-alone systems, and web-based systems. •Display stations can be categorized by their primary use, such as reading stations for radiologists, review stations for referring physicians, technologist QC station for technologist review of images, and image management station for the file room personnel. 1.What does the acronym PACS stand for, and what is its definition? 2.What are the different types of PACS worksta- tions, and how are they used? 3.Define workflow, and give an example of a generic PACS workflow from scheduled proce- dure to finalized report. 4.What is the definition of system architecture, and what are the three major models? 5. What are the advantages and disadvantages of the three system architecture models? 6. What are the most common functions found on a PACS workstation? 7. What specialized PACS workstations may be found in a hospital, and how are they used?