IEC 62563-1 – Medical Image Display Systems: Evaluation Methods

Medical electrical equipment – Medical image display systems – Part 1: Evaluation methods

Medical image display systems are the final link in the diagnostic imaging chain. Regardless of how sophisticated the acquisition equipment, the diagnostic value of a medical image ultimately depends on its faithful reproduction on a display system. IEC 62563-1:2009 (consolidated with Amendment 1:2016), developed by Technical Committee 62 (Medical electrical equipment), provides comprehensive evaluation methods for medical image display systems used in diagnostic applications including radiography, mammography, CT, MRI, ultrasound, and nuclear medicine.

📋 Scope and Purpose

IEC 62563-1 specifies standardized methods for evaluating the performance of medical image display systems. The standard covers both monochrome and color displays, including cathode ray tube (CRT), liquid crystal display (LCD), organic light-emitting diode (OLED), and projection displays. It addresses display systems used for primary diagnostic interpretation as well as clinical review and reporting.

The evaluation methods are organized into the following categories:

Luminance response — conformity to DICOM Grayscale Standard Display Function (GSDF)
Luminance uniformity — spatial variation across the display area
Illuminance dependence — effect of ambient light on display performance
Chromaticity — color coordinates and color uniformity for color displays
Resolution and geometric distortion — spatial accuracy and detail rendering
Angular viewing characteristics — off-axis luminance and color shifts
Display reflection — specular and diffuse reflection coefficients
Veiling glare — contrast reduction due to internal light scattering

The standard uses the TG18 test pattern suite developed by the American Association of Physicists in Medicine (AAPM) Task Group 18 as reference test images. These patterns include TG18-QC for daily quality control, TG18-LN for luminance response, TG18-UN for uniformity, TG18-AFC for low-contrast detectability, and many others.

🔧 Evaluation Methods and Test Patterns

Luminance and Grayscale Evaluation

The cornerstone of medical display evaluation is the luminance response measurement. The display’s measured luminance values at different digital driving levels (DDL) must conform to the DICOM GSDF, which defines the perceptual linearization of grayscale medical images.

Evaluation Category	Test Pattern	Measurement	Acceptance Criteria
Luminance response	TG18-LN (18 luminance steps)	Luminance at each step	Max deviation ≤ 10% from GSDF target
Luminance uniformity	TG18-UN (uniform fields)	Luminance at 5+ positions	≥ 75% of max luminance across display
Ambient light influence	Reflection measurement	Diffuse + specular reflectance	Per manufacturer specification
Resolution	TG18-CX (Cx patterns)	Line pairs visible	≥ specified line pairs per mm
Geometric distortion	TG18-GEO (grid pattern)	Spatial distortion	≤ 1% across active area
Chromaticity	TG18-COL (color bars)	CIE u’ v’ coordinates	Stable within Δu’v’ < 0.01
Angular viewing	TG18-AD (angle dependence)	Luminance at ±30°, ±45°	Luminance ratio > 50% at ±30°
Veiling glare	TG18-GV (glare pattern)	Contrast ratio	Veiling glare index < 0.02

Ambient lighting in the reading room significantly affects perceived image quality. The standard requires measurement of display reflection properties to determine the acceptable ambient illuminance range. Exceeding this range can obscure low-contrast lesions — a direct patient safety concern. Medical display QA programs should include routine ambient light level monitoring.

Color Display Evaluation

With the increasing use of color displays in pathology, ultrasound, and nuclear medicine, the standard’s Amendment 1:2016 expanded color display evaluation methods including:

Color gamut measurement and verification
White point chromaticity stability over luminance range
Color uniformity across the display area
Color look-up table (CLUT) accuracy

🏗️ Engineering Design Insights

Display Quality Assurance Program Implementation

A comprehensive QA program based on IEC 62563-1 involves testing at three levels:

Acceptance testing — Full evaluation upon installation to establish baseline performance
Constancy testing — Daily or weekly checks using simplified protocols (TG18-QC pattern)
Periodic comprehensive testing — Full evaluation quarterly or semi-annually

For PACS workstations used in primary diagnosis, the minimum luminance of the display should be maintained above 400 cd/m² (for color) or 500 cd/m² (for monochrome), with a luminance ratio (max/min) of at least 250:1 for monochrome displays.

When integrating IEC 62563-1 evaluation into a clinical QA program, automation is key. Several commercial and open-source tools can automatically display test patterns, measure luminance via external sensors, and generate compliance reports. Automating these measurements reduces operator variability and ensures consistent QA across multiple displays in a department.

Display Selection for Specific Applications

Different medical applications have different display requirements:

Mammography — Highest requirements: ≥ 5 MP resolution, ≥ 600 cd/m² luminance, ≤ 1.2 cd/m² minimum luminance
Radiography/CT — 3 MP resolution typical, ≥ 450 cd/m², DICOM GSDF conformity essential
Ultrasound — Rapidly updating displays with good color performance, lower resolution requirements
Surgical/procedural — Moderate resolution, high brightness for ambient light tolerance, low latency
Clinical review (non-diagnostic) — 2 MP sufficient, less stringent luminance requirements

❓ Frequently Asked Questions

Q1: How often should medical displays be evaluated according to IEC 62563-1?
A: The standard recommends daily constancy checks (visual inspection using TG18-QC), monthly luminance measurements, and comprehensive evaluation at least annually. Primary diagnostic displays benefit from more frequent testing.

Q2: Can consumer-grade monitors be used for medical image diagnosis?
A: Consumer monitors typically lack the luminance stability, DICOM GSDF calibration, and quality assurance features required by IEC 62563-1. Their use for primary diagnosis increases the risk of missed findings. Medical-grade displays are recommended for any diagnostic interpretation.

Q3: How does ambient light affect display performance?
A: Ambient light reduces perceived contrast by adding a veiling luminance to the display. The standard provides methods to measure this effect and determine the maximum acceptable ambient illuminance for each display model.

Q4: What is the DICOM GSDF and why is it important?
A: The DICOM Grayscale Standard Display Function defines the relationship between pixel values and displayed luminance to ensure consistent appearance across different displays. IEC 62563-1 provides the method to verify and calibrate conformity to GSDF.