Apple Mac OS X Server System Imaging and Software Update Administration For Version 10.4 or Later Manual de usuario descargar pdf (Pagina 13)

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Integrating Mac Systems into

a Medical IT Infrastructure

To conduct conformity tests of the 30-inch Apple Cinema Displays, we used a subset

of the given test criteria, according to the intended use. Table 1 shows the minimum

required values of dierent display characteristics for Germany’s Category A and B

applications.

Table 1: Conformity test standards for 30-inch Apple Cinema Displays (as applied to German

medical imaging application categories)

Application Category Maximum

Luminance

(cd/m

)

Maximum

Contrast

Matrix

Visible

Screen Size

(cm)

Inhomogeneity

Digital radiographic images,

e.g., X-rays

> 200 > 100 ≥ 2000 x ≥

2000

≥ 52 ± 15%

All other types of images,

e.g., angiographic or CT data

> 120 > 40 ≥ 1000 x ≥

1000

≥ 43 ± 20%

Regulations allow lower matrix sizes for Category A if a 1:1 zooming option is used.

Inhomogeneity is dened as the amount that luminance deviates from the center of the SMPTE test pattern to its corners on

50 percent gray level.

Grayscale Calibration

For a radiological workstation, grayscale calibration is critical to achieve the best

possible display quality. Calibration is necessary because the sensitivity of the human

visual system to brightness dierences varies from dark to bright levels. Grayscale

calibration addresses this by adjusting the resulting brightness of monitor pixels

according to the pixel values of the radiological image. Primarily, two dierent standard

display functions exist; they are provided by the DICOM standard

and the Commision

Internationale de l’Eclairage (CIE).

Though not required by law, it is also desirable

to equalize the color of gray to a homogenous, noncolored gray display result.

Gray level representation (ACD 30˝ native)

Gray level (%)

400,00

350,00

Luminance (cd/m

)

300,00

250,00

200,00

150,00

100,00

50,00

0,00

100 20 30 40 50

70 80 90 10060

Measured

Required (GSDF)

Figure 6: Gray level representation of the noncalibrated 30-inch Apple Cinema Display compared

with the required (and far less linear) GSDF curve.

Calibration with a LUT. To calibrate the Apple Cinema Displays, we had to apply an

individual correcting lookup table (LUT) to the viewing system. This allowed us to

match the display’s actual grayscale presentation with an ideal Grayscale Standard

Display Function (GSDF). On the luminance chart shown in Figure 6, GSDF is represent-

ed as the blue curve. This compares with the measured grayscale performance of the

Apple Cinema Displays, represented by the much more linear red curve. The goal

of calibration to is match the measured results with the required GSDF.

Display quality assurance in Germany

Display quality assurance regulations vary by

country. In Germany, for instance, a set of

mandated standards, including the German

DIN V 6868-57 directive, denes both the

application categories of display devices and

the corresponding limits such devices must meet.

For imaging work, it establishes two categories:

Category A covers digital radiographic images

such as chest X-rays.

Category B covers all other types of images such

as CT or angiographic data.

For reporting monitors used with nonradiological

data such as MRI or ultrasound, no special regu-

lations exist in Germany. But quality assurance

regularly includes the viewing of those data types

as Category B applications

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