Technical and radiological image quality comparison of different liquid crystal displays for radiology

Figures & data

Table 1 Short descriptions of technical parameters assessed for each liquid crystal display

Parameter	Section in reference^Citation19	Test pattern TG-18	Short description
Geometric distortion	III.A	QC, LPH, LPV	Visual evaluation of whether lines appear straight and parallel and whether squares appear square
Reflection	III.B	AD	Visual evaluation of low-luminance, low-contrast patterns in near total darkness and in ambient lighting
Luminance response	III.C	LN12	Quantitative measurement of luminance at 18 grayscales to determine conformity with grayscale display function
Luminance: nonuniformity	III.D	UN-L10, UN-L80	Quantitative measurement of luminance at four corners and in the center of the display
Luminance: angular dependence	III.D	LN12-01, LN12-18	Quantitative determination of view angle at which 70% luminance of frontal position is maintained
Resolution	III.E	QC	Visual score of CX patterns in the center and four corners of the display
Noise	III.F	AFC	Visual evaluation of number of visible low-contrast squares in the center and all corners of the display
Veiling glare	III.G	GV, GVN	Visual evaluation of number of visible globes to determine light spread within the display
		GQ	Quantitative measurement of glare
Chromaticity	III.H	UNL80	Quantitative measurement of color of pattern in the center and four corners

Note: Section numbers and test patterns are as designated by the American Association of Physicists in Medicine in an Executive Summary report.¹⁹ Copyright © 2005. American Association of Physicists in Medicine. Adapted from Samei E, Badano A, Chakraborty D, et al., Assessment of display performance for medical imaging systems: executive summary of AAPM TG18 report. Med Phys. 2005;32(4):1205–1225.¹⁹

Abbreviation: TG-18, Task Group 18.

Table 2 American Association of Physicists in Medicine Task Group-18 criteria used for radiological assessments

Test pattern	Evaluation criteria
TG-18-CH (chest X-ray)	Difficulty of interpretation
	Overall contrast
	Overall sharpness
	Symmetrical reproduction of the thorax, as shown by the central position of the process between the medial ends of the clavicles
	Medial border of the scapulae
	Reproduction of the whole rib cage above the diaphragm
	Visually sharp reproduction of the vascular pattern in the lungs
	Sharp reproduction of the trachea and proximal bronchi
	Sharp reproduction of the borders of the heart and the aorta
	Sharp reproduction of the diaphragm
	Visibility of the retrocardial lung and the mediastinum
	Visibility of the subdiaphragmatic features
	Visibility of the spine through the heart shadow
	Visibility of small details in the whole lung, including retrocardial areas
	Visibility of linear and reticular details of the lung periphery
TG-18-KN (knee X-ray)	Difficulty of interpretation
	Overall contrast
	Overall sharpness
	Reproduction of trabecular detail
	Reproduction of bony and soft tissues
TG-18-MM1 and TG-18-MM2 (mammograms)	Difficulty of interpretation
	Overall contrast and brightness
	Overall sharpness (no blur)
	Sharp appearance of cooper’s ligaments
	Clip structure and the presence of the apical gap (TG18-MM1 only)
	Appearance and visibility of subtle microcalcifications (TG18-MM1 only)
	Visibility of structures at the margins of the breast (TG18-MM1 only)
Chest CT	Difficulty of interpretation
	Overall contrast
	Overall sharpness
Brain MR	Difficulty of interpretation
	Overall contrast
	Overall sharpness

Notes: Each question was scored on a visual analog scale of 0–10 for each liquid crystal display. Criteria are as designated by the American Association of Physicists in Medicine in an Executive Summary report.¹⁹ Copyright © 2005. American Association of Physicists in Medicine. Adapted from Samei E, Badano A, Chakraborty D, et al., Assessment of display performance for medical imaging systems: executive summary of AAPM TG18 report. Med Phys. 2005;32(4):1205–1225.¹⁹

Abbreviations: CT, computed tomography; MR, magnetic resonance; TG-18, Task Group 18.

Table 3 Technical assessments of the different LCD models

	Description	Criterion	NEC^®	Eizo^®	Barco^® 3-MP	Barco^® 6-MP
Geometric distortion			Absent	Absent	Absent	Absent
Reflection	Number of visible patterns in total darkness		40	34	34	34
	Number of visible patterns in ambient lighting		39	27	6	34
Luminance response	Maximum, cd/m^2	≥170	410.9	394.0	399.7	328.1
	Deviation from 400 cd/m^2 (calibrated maximum luminance), %	≤5	2.7	1.5	0.1	18.0
	Deviation from GSDF over 18 grayscales, % (mean±SD)		3.7±2.8	2.4±2.5	2.1±1.9	3.2±2.2
	Maximum deviation from GSDF, %*	≤10	11.9	11.1	7.3	8.3
Luminance: nonuniformity	Nonuniformity for UNL10 (low luminance pattern), %	≤30	0.4	0.4	0.2	0.2
	Nonuniformity for UNL80 (high luminance pattern), %	≤30	8.9	8.4	3.3	10.5
Luminance: angle dependencies	View angle for LN12-01 (low luminance pattern), degrees		35	35	40	55
	View angle for LN12-18 (high luminance pattern), degrees		25	25	25	45
Resolution	Similarity between CX patterns**	≤4	1	1	1	1
Noise	Number of visible squares	≥15	15	16	16	16
Veiling glare	Number of visible globes	≥3	5	5	4	4
	Glare ratio	>400	1,711	1,406	485	364
Chromaticity	Difference in color coordinates	≤0.01	0.0017	0.0042	0.0023	0.0024

Notes:

* For all four displays, this was measured at the lowest gray level (LN12-01 pattern);

** lower scores indicate better resolution.

Abbreviations: GSDF, grayscale standard display function; LCD, liquid crystal display; MP, megapixels; SD, standard deviation.

Table 4 Reliability of image assessments for predicting liquid crystal display quality, determined with Cronbach’s alpha

	Cronbach’s alpha*
Chest X-ray	0.990
Knee X-ray	0.989
Mammogram	0.963
Chest CT	0.974
Brain MR	0.975

Note:

* Alpha values >0.70 indicate acceptable reliability.

Abbreviations: CT, computed tomography; MR, magnetic resonance.

Figure 1 Radiological assessments for each type of LCD, according to AAPM TG-18 criteria. Symbols indicate different LCD types; scores are represented as the mean and standard deviation on a scale from 0–10 (n=19 evaluators).

Abbreviations: AAPM, American Association of Physicists in Medicine; TG-18, Task Group 18; LCD, liquid crystal display; MP, megapixels; sd, standard deviation; CT, computed tomography; MR, magnetic resonance.

Table 5 P-values for comparisons of radiological assessments made with different liquid crystal displays

	Degree of difficulty	Overall contrast	Overall sharpness	Anatomy
Chest X-ray	0.109*	0.236*	0.008**	0.067*
Knee X-ray	0.346*	0.140*	0.088*	0.095*
Mammography	0.023**	0.031*	0.059*	0.072*
Chest CT	0.416*	0.637**	0.089*
Brain MR	0.153*	0.166*	0.024**

Notes: After Bonferroni adjustments for multiple comparisons, P≤0.0028 was considered statistically significant.

* P-value according to the Huynh-Feldt statistic

** P-value according to Mauchly’s test (spherical data).

Abbreviations: CT, computed tomography; MR, magnetic resonance.

SameiEBadanoAChakrabortyDAssessment of display performance for medical imaging systems: executive summary of AAPM TG18 reportMed Phys20053241205122515895604

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