iaea human health series publications - SEDIM

FIG. 35. Modified TG18-QC test pattern with test objects indicated: A — 0–5% contrast square, B — 95–100% contrast square,C — horizontal and vertical line pairs, D — squares going from black to white, E — 5 cm line, F— greyscale ramp, andG — ‘QUALITY CONTROL’ subjective test.(5) Inspect the greyscale ramps (F in Fig. 35) to ensure that they are smooth and continuous, without noticeableterracing or discontinuities.(6) Visually check that the lines dividing the test pattern into squares are crisp and straight, that the pattern iscentred in the active image area of the monitor and that the squares are indeed square (correct aspect ratio),with right-angled corners.(7) Verify that the 16 grey level patches framing the central portion of the test pattern are distinguishable fromone another, and that the low contrast corners in each patch are visible.(8) Examine the text areas (G in Fig. 35) below the central region of the pattern (only required for primary displaydevices/radiologist workstations). Letters spelling ‘QUALITY CONTROL’ are printed in progressivelyfainter text over dark, mid-grey and white backgrounds. Record the number of letters visible over eachbackground on the acquisition monitor display quality chart (Chart 13(a) in Annex II) or the review monitordisplay quality chart (Chart 13(b) in Annex II), as applicable.(9) Verify that the 0–5% contrast box (A) is clearly discernible.(10) Verify that the 95–100% contrast box (B) is clearly discernible.121