Barco R9003110 - Manual (Page 45)

6. Introduction to Medical Visualization systems
6. INTRODUCTION TO MEDICAL VISUALIZATION
SYSTEMS
DICOM
Digital Imaging and Communications in Medicine
It is a standard developed by the American College of Radiology (ACR) and the National Electrical Manufacturers
Association (NEMA). The standard specifies how digital image data can be moved from system to system. In addi-
tion, Supplement 28 Part 14 specifies a function that relates pixel values to displayed Luminance levels and is called
Grayscale Display Function Standard.
Overview
• DICOM conformance
• Architecture of a typical medical visualization system
• Overview of Barco’s DICOM THEATRE ®
• Introduction to MGP configuration
6.1 DICOM conformance
Need for standardization
A digital signal from an image can be reproduced objectively and accurately. However, the visual interpretation of that signal is
dependent on the characteristics of the systems displaying that image i.e. images produced by the same signal may appear different
depending on the display device. In medical imaging, it is important that there be a visual consistency in how a given image appears,
whether viewed, for example, on the display monitor of a workstation, a projector or as a film on a light-box. In the absence of any
standard which regulates how these images are to be visually presented on any device, a digital image which has good diagnostic
value when viewed on one device could look very different and have greatly reduced diagnostic value when viewed on another
device.
Accordingly, PS 3.14 was developed to provide mapping of digital image values into a given range of Luminance. The mapping
or relationship between digital values and display Luminance produces better visual consistency in how that image appears on
diverse display devices. The relationship that PS 3.14 defines between digital image values and displayed Luminance is based
upon measurements and models of human perception over a wide range of Luminance and thus independently of the nature of the
presentation device.
It is also not dependent upon user preferences but uses a DICOM Presentation Lookup Table.
A system is DICOM-compliant when it respects a predefined relationship (PS3.14) between digital input signal
values and display Luminance.
6.2 Architecture of a typical medical visualization system
LUT
Look Up Table. A table containing the displays output values (Luminance) in function of the input signal (amplitude)
System components
Basically a medical visualization system may contain:
• Calibration/Control unit
• Feedback unit
• Display unit
System Principal
A closed loop system insures a stable control system by means of a feedback signal being the Luminance at display level, and gets
rid of possible drift (caused mainly by aging and external conditions) in the displayed Luminance value.
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