In this blog post, I will explain why X-ray films have almost disappeared from hospitals and summarize the principles and advantages of PACS, the computer system that has replaced them.
The Landscape and Challenges of the X-ray Film Era
In the past, it was a common sight in hospitals: after an X-ray was taken, the doctor would return to the examination room and insert the film into a light box to examine it. This scene, which anyone visiting a dentist or orthopedic clinic has likely experienced at least once, was a routine occurrence in almost every hospital just 10 to 15 years ago.
However, such film is now rarely seen in large university hospitals and many private clinics. Film-based medical imaging systems required vast amounts of space and significant costs for storage, and the burden of managing the ever-growing pile of film continued to increase over time. Furthermore, the process of locating and retrieving physical film was time-consuming and labor-intensive, and there was a critical drawback: once damaged, the film was difficult to restore.
The chemicals used in the development process caused environmental pollution, and since the quality was often inferior to high-resolution digital images, it led to a high rate of retakes, creating disadvantages from a clinical perspective. For these reasons, the need for a new system to digitize, store, and manage medical images within hospitals became apparent.
Definition and Operating Principles of PACS
What is PACS?
PACS (Picture Archiving and Communication System) refers to a comprehensive image management and communication system that acquires medical images in digital form, stores them in a database, and enables medical staff to view, search, and transmit images through linked software. Simply put, it is a computer infrastructure that allows medical images generated in hospitals to be electronically stored, shared, and utilized for patient care.
PACS Architecture and Workflow
PACS consists of three main components: imaging acquisition devices (e.g., X-ray, CT, MRI), a database for storing medical images, and client (viewer) software used by medical staff. Imaging acquisition devices output images for patient diagnosis in digital format, which are then saved in the international standard DICOM format.
The DICOM standard is used to ensure compatibility of images and related information across equipment from different manufacturers and between hospitals. In other words, it facilitates the transmission of images and joint diagnosis with other hospitals or institutions using the same PACS, making it advantageous for collaborative care and telemedicine.
Data Storage Methods and the Role of the Viewer
Images generated in DICOM format are stored in a database and managed in tiers such as Short Term, Mid Term, and Long Term, depending on the storage duration and frequency of access. The Short Term tier is a space for storing high-resolution, uncompressed images immediately after acquisition, and images from this tier are primarily used during medical consultations. Over time, the images are converted to a low-capacity format and transferred to the Mid Term and Long Term tiers to reduce storage costs.
Medical staff can quickly view images through viewer programs connected to the PACS and utilize various tools—such as brightness adjustment, zoom, and measurement—to make diagnoses. Viewers go beyond simple image display to provide various auxiliary functions necessary for diagnosis.
Changes and Actual Benefits Brought by PACS
The introduction of PACS has brought noticeable changes to hospital settings. First, the process of storing and managing physical film has been eliminated, resulting in significant savings in space and costs. Digital archives reduce the risk of loss or damage and facilitate long-term storage.
First, the likelihood of medical images being lost or damaged has been virtually eliminated, and long-term storage is now possible at a relatively low cost.
Second, digital images offer superior quality compared to film, leading to a lower rate of repeat imaging. Additionally, the viewer’s correction features allow for the correction of deficiencies, reducing the need to re-scan from the beginning.
Third, the viewer enables adjustments to brightness and contrast, precise measurements of length and angle, and magnification of areas of interest for observation, making more precise diagnoses possible. Another major advantage is that sharing images with medical staff in remote locations via the DICOM standard has made collaborative care and remote interpretation easier.
In summary, PACS has computerized the entire process—from the acquisition of medical images to their storage, retrieval, viewing, and transmission—thereby simultaneously improving operational efficiency and the quality of care. Even in hospital settings that may seem far removed from electrical and information technology, the introduction of such invisible technologies is quietly driving significant innovation.
