Understanding NRT- Reading 1- 2 of 2- Radiogaphic Testing A
Understanding nrt reading 1- 2 of 2- radiogaphic testing a
Understanding nrt reading 1- 2 of 2- radiogaphic testing a
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Tabular Solution <strong>of</strong> Milliamperage-Time and Distance Problems<br />
Problems <strong>of</strong> the types discussed above may also be solved by the use <strong>of</strong> a<br />
table similar to the one below. The factor between the new and the old<br />
exposure time, milliamperage, or milliamperage-minute (mA-min) value<br />
appears in the box at the intersection <strong>of</strong> the column for the new source-film<br />
distance and the row for the old source-film distance.<br />
Suppose, for example, a properly exposed radiograph has an exposure <strong>of</strong> 20<br />
mA-min with a source-film distance <strong>of</strong> 30 inches and you want to increase the<br />
source-film distance to 45 inches in order to decrease the geometric<br />
unsharpness in the radiograph. The factor appearing in the box at the<br />
intersection <strong>of</strong> the column for 45 inches (new source-film distance) and the<br />
row for 30 inches (old source-film distance) is 2.3. Multiply the old<br />
milliampere-minute value (20) by 2.3 to give the new value--46 mA-min.<br />
Charlie Chong/ Fion Zhang
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