Information Technology is an integral part of health care. A modern radiology department is no different. Ever since the invention of the computer, radiology departments have led the technology race beginning with computed tomography.
Ever since the abacus originated in Mesopotamia in 3500 B.C., the idea of a computer has evolved throughout history. It was finally the arrival of the microprocessor in 1972 that led to the development of the microcomputer and the foundation of the modern personal computer (PC)
A computer has four basic elements:
The personal computer can be further broken down into a variety of components:
Computers cannot understand complex phrases or numbers such as the in the decimal system. Instead, a simple system of "ones " "zeros" was developed for computers to use. This system is called Binary Code. This is because computer chips are simply a series of switches that are either "on" (=1) or "off" (=0). On or off can also equate to "true" or "false" and if-then statements.
Software is a set of instructions that tell the computer components what to do. Software can be separated into 5 types: System software or the Operating System (OS), application software (word processors, etc.), video games, websites, and firmware.
Many of the software programs have extensive Graphical User Interfaces (GUI's). GUI's are what allow people to interact with a computer. An example of a GUI is the arrow on the screen being controlled by the mouse or a file folder representing an area of stored information (an icon).
Computers function as the main component of a PACS system. In fact, a PACS is simply a series of computers and servers networked in a special way that allows for the transferring and storage of digital images.
Networking is the vehicle or pipeline for medical information. There are two basic network types. Local Area Networks (LAN) are confined to a relatively small geographical area such as a home or a small group of offices. In a Radiology department, a LAN can be a cluster of imaging devises. Wide Area Network (WAN) covers a wide geographical area involving a vast array of computers. For example, the internet is the largest WAN on the planet. WAN's are used to interconnect LAN's
Servers are a combination of powerful computers with specialized software. Servers are used to perform a wide variety of tasks in every industry. Specific to a PACS, servers perform data storage, backup, web functions, and image distribution duties. Essentially, a PACS is a LAN comprised of multiple servers performing a variety of support functions operating behind user interfaces (workstations)
The ability to store information is vital to any successful PACS. A good storage system is dynamic and able to adapt to changing technologies or demands. Furthermore, a good system is able to expand in order to accommodate increased data consumption. Data storage systems must also be able to withstand natural disasters or equipment failures. This is accomplished through redundancy such as the use of a RAID or off-site archives.
Storage Media
There are many devices that can be used to store information within a PACS. However, today the costs of storage have decreased to the point where the Hard Disk Drive is the first choice for many PACS. Hard drives can be used in a variety of roles and have a large range of price, size, and function. Other forms of storage media include flash based memory, magnetic tape, optical mediums (CD & DVD), etc.
RAID systems are the most common way PACS store their information. For example, a set of four hard disk drives can be connected in parallel to each other (information is broken down and written between each of the drives) to write 4x faster than a single disk. Disks can be connected in series (information is duplicated between more than one drive) for redundancy in case a drive fails. There are a variety of complex RAID systems that both increase speed and improve redundancy. These variations are called "Levels" for example, "RAID 0" is where data is broken up and distributed between multiple disks and "RAID 1" is where data is mirrored or duplicated between multiple disks. A "RAID 1+0" or simply "RAID 10" is a 4 or more disks, 2 sets of 2 disks, each set mirrors the other increasing both speed and redundancy. "RAID 5" is the most common system used in PACS. In addition, RAID systems can be combined to create "nodes" or RAIN.
The observation made in 1965 by Gordon Moore, co-founder of Intel, that the number of transistors per square inch on integrated circuits had doubled every year since the integrated circuit was invented. Moore predicted that this trend would continue for the foreseeable future. In subsequent years, the pace slowed down a bit, but data density has doubled approximately every 18 months, and this is the current definition of Moore's Law, which Moore himself has blessed. Most experts, including Moore himself, expect Moore's Law to hold for at least another two decades.
In essence with the doubling of the integrated circuit capacity, the speed and efficiency of computers will double along with data size and the need for space to store the data.
To a PACS system this means the storage space needed just to keep up with the current pace of technology must double every 2 years. This has slowed a bit in recent years but the basic principle still holds true
In an effort to keep speeds high and premium storage space efficient, many PACS systems use compression techniques to handle the storage of data. Compression is the minimizing of bites by removing redundant information in order to allow for files to take up less hard drive space and create faster transmission of information. For example, if an image has 6 bits of the same value (12, 12, 12, 12, 12, 12) the compression may re-write this information as 6x12. This is a form of "lossless" compression because the data is kept at its original integrity. Most PACS use lossless compression for the storage of their images. This is to prevent any liability issues that can be potentially caused by the removal of valuable information in an image. Compression can also completely remove information deemed low importance and using algorithms can re-construct the image on the other side of transmission. This is called "lossy" compression. Lossy compression is most commonly used to distribute images from a PACS for review over the LAN. For example, the ER physician viewing images in a web-based PACS. Some compression standards include JPEG, MPEG, Bitmap, GIF, and PDF.