Digitization of radiology departments, the need for higher resolution diagnostic images and widespread installation of picture archiving and communication systems in hospitals are providing the requisite impetus for growth of the global market for digital radiography systems.

The past few decades have witnessed consistent technological evolution in the field of radiology with the development of several newer imaging modalities such as computed tomography, magnetic resonance imaging and nuclear medicine, among others. The emergence of such computer-intensive imaging modalities have marked the advent of an era of film-less radiology. There has hence, been an augmentation in the availability of diagnostic capabilities in digital radiography domain, as well as their scope. The consequent emergence of the field of digital radiography (DR) and computed radiography (CR), has completely altered the face of the conventional x-ray imaging modality. Healthcare facilities worldwide are now following the global trend by gradually replacing film/screen radiography systems with digital radiography systems. The transition to film-less systems is being fuelled by the need to make images faster, easier and less expensive to obtain, review, duplicate, share and store. Further, digital radiography has the potential to offer greater productivity, improved efficiency and more accurate diagnoses.

As per a report, the global market for x-ray systems was valued at USD 4.9 billion in 2008 and the digital x-ray systems accounted for a whopping share of 86.2 percent of this market, amounting to USD 4.25 billion. The digital x-ray systems market is even expected to grow at a higher rate of 7.1 percent between 2008 and 2015, as compared to the x-ray systems market which will grow at an estimated 6.7 percent annually. This will also lead to an increase in the share of the digital x-ray market to 88.3 percent of the overall x-ray market. Pertaining to the Asian market, countries like China, Japan, South Korea, Taiwan and Hong Kong are moving towards adoption of digital radiography systems at a fast pace. China, for instance is providing strong incentives to its healthcare facilities to move from conventional to digital x-ray systems. The overall market is mainly concentrated between 3-4 major players, while the rest of the players account for relatively lesser shares. In fact, the emergence of digital x-ray equipment has provided the much necessary impetus to the growth of the overall x-ray market.

The gradual replacement of film-based systems with digital radiography systems can be attributed to certain prerequisite technological advances, such as high-resolution display monitors combined with high-performance computer workstations. The subsequent emergence of electronic archives that can efficiently store data has been another key factor that supported the evolution of digital radiography. Going further, installation of high-speed electronic networks with bandwidth capable enough of transferring images anywhere also became imperative for healthcare facilities around the world.

Advantages of Digital Radiography over Conventional Radiography
Digital Radiography	Conventional Radiography
Digital radiography systems provide immediate viewing of radiology images	There is a delay in viewing the image as the film has to get developed first before it can be read.
Allows the radiologist to enhance image quality by altering the contrast, enlarging the image, placing colour enhancements and so on. A	Does not offer image enhancement feature, as a film once developed cannot be altered.
Radiographic images can be easily stored on a computer and accessed any time, anywhere with the help of various available modalities.	The hard copies of the images are filed and stored because of which there are chances of the records getting misplaced.
Practically eliminates the need to develop films and maintain them as the images are directly displayed on the computer screen.	Maintaining the developing device and fixing the developing solution each time can be a time consuming and undesirable task.
Image sharing has now become a matter of minutes.	Image sharing takes time as the hard copies will either have to be scanned first before sharing the image online or sent via mail.
There is almost a 70 to 80 percent reduction in the radiation exposure as compared to conventional radiography.	Potentially high exposure to radiations may prove to be hazardous.

Technology Assessment

The CR and DR technology are similar as far as the digital format of the resultant image is concerned, as images obtained from both are compatible for storage in picture archiving and communication systems (PACS) and their appearance can be manipulated. However, the differences are far greater in number and involve the operation and image capture, workflow and cost, technique and dose, and image quality. The installation of CR does not require changing the conventional x-ray equipment; it is merely the addition of CR readers and cassettes. uation of the conventional radiography technique, in particular, reveals several advantages offered by this imaging modality. Exceptional image quality is probably the most important feature. It also completely eliminates the need for taking any retakes as the resolution of the image once captured can be easily altered on the monitor to improve quality. Also, a single exposure offers more information as compared to that obtained on a film. Reduction in costs for processing the images as compared to conventional techniques has also been noticed as the imaging plates used by CR can be re-used 15,000 to 40,000 times, which eliminates the need for x-ray film and their processing. In contrast to CR, in DR technology, no cassettes are required as the images are recorded directly in digital format. The elimination of cassettes in this technology makes this process faster than the CR process, and provides a greater patient throughput. However, as DR technology is more expensive than the CR, it is essential to consider the advantages and drawbacks of a DR system in terms of workflow and relative costs. This may largely depend on a facility’s patient load and future growth projections.

The medical imaging market is currently in a transition state as healthcare facilities around the world are now opting for digital radiography solutions over conventional radiography solutions. One of the most important reasons for this is the emergence and implementation of PACS network. Subsequently, the enhancement in the clinical value of PACS has also been a result of installation of direct digital modalities. PACS was launched with an idea to collect images from all modalities to a digital archive and to allow the transmission of these images to other workstations through local area network (LAN). Further, the traditional transmission control protocol/internet protocol (TCP/IP) was gradually replaced by digital imaging and communications in medicine (DICOM) protocol, which was capable of managing any sort of medical images. The DICOM protocol hence extended from the radiology department to the entire clinical department in a healthcare facility and became the standard of clinical data transmission. The increasing popularity of PACS is further driving the sale of high-end radiology information systems (RIS), a computerised system for patient registration, as text-based RIS products such as film tracking databases will be marketed with PACS solution.

It is crucial to however note that in absence of a PACS of PACS like solutions, the advantages of a digital radiography system are lost, more or less because there is no electronic information management system to store and retrieve patient information. The printouts of digital scans offered on a film are or the scanning of x-ray films to produce digitized images are both inefficient procedures. Hence a primary requirement for installing DR and CR solutions is to first install a viable information management system to efficiently manage all the data produced in these procedures.

Major roadblocks

The cost-sensitive nature of the Indian market does not allow a high-end technology like DR, which is associated with huge price tags, to grow. While, the high prices of these systems may be attributed to R&D and IT implementation, it is essential to balance the price of the technology with the product quality. The general perception still is that, unlike diagnostic modalities such as PET and MRI, installing DR is a luxury and not a necessity. It has hence become imperative for manufacturers to offer the best possible product at minimum price to encourage even smaller healthcare facilities to buy this technology. Gradually, the prices of these systems are coming down, however it will still take some time before it can fit the Indian pocket.

“The cost-sensitive nature of the Indian market does not allow a high-end technology like DR, which is associated with huge price tags, to grow. While, the high prices of these systems may be attributed to R&D and IT implementation, it is essential to balance the price of the technology with the product quality.”

DR and CR Solutions in Medicine

Digital Radiography Changing the way we work

Radiology has seen a sea change in the last thirty to forty years with the introduction of digital modalities like CT, MRI, ultrasound and mammography. Radiography is the last segment of radiology to turn digital and is currently going through a significant change across the world. Most hospitals, large to moderate and diagnostic centres are in the process of switching or have already switched to digital radiography. The primary driver for this change is not just the availability of newer technologies or it being fashionable, but the fact that digital systems significantly improve workflow, are much easier to work with and make economic sense in the longer term.

Computed Radiography (CR)

CR uses a technology called Photostimulable Luminescence or the storage phosphor technology. In this method a phosphor imaging plate (IP) replaces the x-ray film and screen. The IP, when exposed to an x-ray beam, stores the pattern of x-ray exposure and retains it as energy for several hours. When exposed to a light source, such as a focussed laser beam, the IP releases the stored energy by emitting light. This emitted light is captured and converted into usable electrical signals. These electrical signals are then processed to produce an image. Any latent energy still retained in the IP is then erased by exposing it to a very bright light. The IP can now be re-used to capture the next image.

Essentially a CR system consists of the following components in addition to a conventional x-ray machine.

• Specially designed CR cassettes with a matching IP inside

• A CR reader laser scanner connected to the workstation

• A computer workstation with the image processing software

The workflow of a CR system is very much akin to that of a conventional (analogue) film and screen based unit. Most part of the workflow remains similar to the conventional system except that the CR cassette is fed into a CR laser reader, instead of a dark room process.

Digital Radiography (DR)

Unlike CR, DR uses x-ray detectors that directly produce an x-ray image on the computer monitor in a few seconds without the need of a laser reader. The fundamental principle behind a DR is to capture the pattern of x-ray exposure on a sensor which converts it into usable electrical signals that can be processed into an image. Since this technique does not involve physical transportation of cassettes or any scanning process, the exposure to image display is fast and efficient.

Two different types of technologies are used “Direct” & “Indirect” Detectors

• “Direct” Digital Radiography Amorphous Selenium Flat Panel Detectors (FPD)

• “Indirect” or Scintillator and CCD Based Detectors

• “Indirect” or Scintillator and Amorphous Silicon Flat Panel Detectors (FPD)

A “direct” DR FPD is made up of an array of microscopic Amorphous Selenium sensors that are arranged in a matrix of small picture elements (pixels), very close to each other. When exposed to an x-ray source, the corresponding sensors or pixels release proportionate amount of electrons causing an electron current. The electrical signal that is hence produced is amplified and processed to obtain an x-ray image.

In the “indirect” method a phosphor screen or scintillator, that converts x-ray photons into proportionate quantities of light photons, is used in conjunction with either photosensitive semiconductors or photodiodes or CCD to convert the x-rays into usable electrical signals. Since X-rays are first converted to light and then to usable electronic signals, it is called an “indirect” method or indirect detectors.

Primarily there are two types of “indirect” detectors commonly in use today. Some manufacturers use a scintillator coupled with a CCD panel to capture and deliver the x-ray image. Since CCD based detectors are “lossy” and inefficient compared to flat panels, they require a relatively higher x-ray dose. Moreover they are bulky and space consuming. As a result, Amorphous Silicon Flat Panels with built-in scintillators are emerging as the most popular and widely accepted technology of choice and are available in both fixed and portable formats.

Amorphous Silicon with scintillator is a technique that uses a scintillator or phosphor screen that is placed directly above an array of Amorphous Silicon sensors.

Bedside and Emergency Radiography

Significant improvement in detector packaging technology, better management of IC power consumption and heat dissipation have resulted in thinner and lighter flat panel detectors that are easy to handle and are portable. This has opened up a lot of options to the clinicians and hence digital radiography can now be made available at the point-of-care. The mobile x-ray machine, flat panel detector like the one seen in the picture combine to give instant results, right by the patient’s bed side or the point-of-care. Connectivity to LAN / WAN is available and images can be pushed to a PACS network instantly. Such flat panel detectors can be integrated with various types of x-ray systems to function as a full fledged digital radiography system. Various system configurations are possible and depending on the budget and application, either a single flat panel detector or multiple detectors can be configured with them.

Detector technology – Image phosphor coupled to a-Silicon photodiode array:-

Different types of digital radiography technologies are available in the market today. The most popular manufacturers of flat panel solutions such as Canon, Trixel, GE, Varian and others offer a technology that involves Amorphous Silicon coupled to a Phosphor Scintillator. The X-ray scintillator in the detector is normally a thallium doped Cesium Iodide (CsI) phosphor or a Gadolinium Oxy-Sulphide (Gd2O2S). The X-rays interact with the phosphor and release light photons. The phosphor is directly coupled with the read out array. The light from the phosphor is converted into electrical charge in the photodiode array; the charge is then stored in a capacitor until the charge is then read out from each of the pixels. These are commonly referred to as amorphous-Silicon (a-Si) systems.

DR: A Better Technology than CR

Has the emergence of digital imaging modalities had any significant effect on the medical imaging markets around the world? Is there a significant scope of growth of this technology in India?-

The innovation of digital radiography (DR) system has significantly improved the clinical workflow and efficiency of the department and has also helped shorten the diagnostic and therapeutic decision-making processes. Additional benefits are improved patient comfort, reduction in radiation doses, higher examination throughput (i.e. multiple examinations during one visit) and a more pleasant atmosphere in the waiting room (through shortened examination and waiting times for x-ray) as the x-ray images are available at any time, throughout the hospital, in a PACS environment. All represent major benefits for the patient and increased satisfaction.

The technology has tremendous scope in India, primarily in the major existing as well as upcoming hospitals. The existing hospitals, both government as well as private, are upgrading themselves to this new technology due to the benefits mentioned above.

What are the major advantages these systems offer over traditional film-based systems? What has been the major trend in the development of this technology over the past few years?

The conventional film based system involves patient x-rays to be taken on the film and developed in the manual/automatic film processor. About 7-8 years ago, the CR system was introduced, which changed the quality of x-ray images over conventional film-based radiography. However, these CR systems involved the CR cassettes, which have a definite life of few thousand x-ray exposures. After taking the x-ray on the CR cassettes, it has to be processed in the CR reader and then the image appears on the CR workstation, so that the image can be transferred to the network or to take printouts on the laser camera. The CR system of course improved the quality of the x-ray images and improved patient workflow and efficiency, as mentioned above.

In DR systems, the patient images are taken directly on the digital flat detector. So, there is no use of cassettes and the images are available immediately on the console. This has further improved the clinical workflow and the efficiency of the radiology department. Compared to the CR system, the quality of images is better in flat detector system (DR systems).

What are your major product offerings in this segment? Could you also enlist a few major customers who have purchased DR and CR systems from Siemens?

We offer a complete range of digital radiography system as follows:
Ysio: It is a completely new digital radiography solution. Whether for general, trauma, dedicated chest or other specialized imaging applications, for hospitals or private practices, for budgets large or small, Ysio is available in a variety of combinations. It can be used as a wall stand with an integrated detector; a wall and table system with a wireless detector (wi-D); as a mixed detector solution for high throughput and flexibility.

AXIOM Aristos FX Plus is a multifunctional, ceiling-mounted FD x-ray system for chest exposures and skeletal radiography of the skull, abdomen and extremities. The ceiling-mounted supports can be freely positioned in the room, offering a high level of flexibility during all exams enabling lateral and oblique exposures as well as trauma applications with a single X-ray system. The enhanced workflow of this system allows more than 500 organ programs for automatic system positioning making it a fast, flexible system positioning around the patient for greater comfort. A feature called DiamondView provides optimum image presentation. Lastly, it fulfills virtually all examinations with a single detector.

AXIOM Aristos VX Plus is a fast and flexible imaging system with a tiltable flat detector stand, a ceiling-suspended x-ray tube stand and an optional trolley. This system accommodates imaging of extremities as well as upright and recumbent examinations. Owing to digitization, activities such as loading and transporting cassettes and material disposal have been eliminated. The optimized workflow and connectivity features further reduce waiting times for higher patient throughput.

MULTIX Swing with its integrated mobile flat detector (mFD) enables users to access the convenience and benefits of digital radiography (DR). It virtually covers the full spectrum of general and specialized radiographic applications for both in-bucky and out-of-bucky examinations. The mFD is easy to handle and proves to be as flexible as the conventional cassettes.

AXIOM Aristos MX is the universal DR system for all standard examinations, from head to the spine, abdomen and extremities. It is an ideal solution for hospitals of all sizes. The automated tracking feature in vertical, horizontal and oblique axes for faster workflow. It also allows upgradeability to tomography for expanded applications.

Conceived as a multipurpose system, AXIOM Multix M covers the full spectrum of general-purpose radiographic applications from skeletal to thorax, pediatric to orthopedic exposures both on and off the table, as well as on the wall stand. With its DICOM standard compliance, it forms an ideal fit with existing IT and archival infrastructures and also with smaller stand-alone systems. Matching a wide application range with easy handling, AXIOM Multix M is a real time-saver in any radiology lab.

AXIOM Vertix MD Trauma is a radiography workstation designed and optimized specifically for traumatology. It offers lateral, oblique and p.a. projections and can be upgraded with a bucky wall unit.

AXIOM Vertix Solitaire M is a flexible, digital radiographic system with a ceiling-mounted X-ray tube stand, bucky wall stand and mobile Flat Detector. The system has no fixed table and is especially well-suited for stretcher, wheel chair and routine imaging with an emphasis on trauma. The system can be configured to cover several trauma bays, allowing for immediate imaging when it counts the most.

What is the role of integrated information management systems in DR and CR technology?

The Hospital information and radiology information system plays a major role in the hospital. Right from the appointment to scheduling of patient work list to reporting of images can be performed efficiently.

Which according to you is a better technology out of the two?

Of course, DR system is a better technology. At the  same time, this has to be uated on return on investment.

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