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Volume 2 - Atomic Energy Regulatory Board

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C.3 Measurement of Timer Linearity<br />

Operating parameters : kVp : Slice thickness : mA:<br />

mA settings mAs Output μGy/mAs<br />

μGy<br />

(X)<br />

X max<br />

– X min<br />

Coefficient of linearity (COL) = —————<br />

X max<br />

+ X min<br />

Tolerance in COL : ± 0.1<br />

C.4 Output Consistency<br />

Operating parameters : mAs : Slice thickness :<br />

kVp Output Mean (X) COV<br />

1 2 3 4 5<br />

Coefficient of Variation (COV) = [ ∑ (Xi - X mean<br />

) 2 /(n-1)] ½ / X mean<br />

Tolerance in COV : ± 0.05<br />

D. CONTRAST RESOLUTION<br />

D.1 Low Contrast Resolution<br />

Use low contrast resolution test phantom.<br />

Operating parameters : kVp : mAs : Slice thickness<br />

Window width :<br />

Result :<br />

Low contrast resolution : ————— mm at ———— % contrast difference<br />

Tolerance :<br />

5.0 mm at 1% contrast difference (minimum)<br />

2.5 mm at 0.5 % contrast difference (expected)<br />

236

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