Radiography in Modern Industry - Kodak
Radiography in Modern Industry - Kodak
Radiography in Modern Industry - Kodak
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used to set up the expos<strong>in</strong>g unit (if an exposure error is <strong>in</strong>dicated), or poor densitometry. If anabnormal process is <strong>in</strong>dicated, process another set of control strips. (It is for this purpose thatmore than the m<strong>in</strong>imum of two strips for each processor is advisable.)When an out-of-control condition does exist that is the result of a film process<strong>in</strong>g variation and notan obvious test<strong>in</strong>g error, the process should be restarted with fresh solutions. Add<strong>in</strong>g chemicalsto the developer is frequently unsuccessful, is more time consum<strong>in</strong>g, and is more expensive <strong>in</strong>the end than restart<strong>in</strong>g the process. Contam<strong>in</strong>ation of the developer (1 mL of fixer <strong>in</strong> a gallon ofdeveloper can be detected <strong>in</strong> film densities) and underreplenishment of the developer areexamples of conditions that <strong>in</strong>dicate the process should be restarted with fresh solutions.TechniqueExposure of Control FilmLoad the cassette with a sheet of control film. (If the control film has been refrigerated, be sure toallow enough time for the film to reach room temperature before handl<strong>in</strong>g.) If lead <strong>in</strong>tensify<strong>in</strong>gscreens are used <strong>in</strong> the normal production operation, use the set reserved for process control.Carefully set up the x-ray exposure unit for the exposure technique. The cassette and thestepped wedge must be positioned identically each time control film is exposed.Cut the exposed film <strong>in</strong>to a m<strong>in</strong>imum of twice the number of processors <strong>in</strong> the control system. Ifpossible, cut more than the m<strong>in</strong>imum, but do not make duplicate exposures and assume they areidentical. Each exposure of control film must be considered a complete control.Identify the strips as to date and expos<strong>in</strong>g unit.Place half or the exposed control strips <strong>in</strong> an airtight, light tight, and moisture proof wrapper andstore them <strong>in</strong> the refrigerator. Remove the moisture proof package of control strips exposed <strong>in</strong> thesame unit the previous day. When these latent-image control strips are at room temperature, theycan be handled and processed.Process<strong>in</strong>g of Control StripsProcess the freshly exposed control strips and the strips exposed <strong>in</strong> the same unit the previousday <strong>in</strong> the correspond<strong>in</strong>g processor (or processors).If the strips are less than 21/2 <strong>in</strong>ches wide, tape them to a leader. If a leader is not used, processa cleanup sheet before process<strong>in</strong>g the control strips.Always process a fresh control strip exposed <strong>in</strong> a designated unit with a control strip exposed <strong>in</strong>that same unit the previous day.Record <strong>in</strong> the log the temperature of the developer at the time the strips are <strong>in</strong> the processor.Record <strong>in</strong> the log any other <strong>in</strong>formation pert<strong>in</strong>ent to process control.DensitometryCheck the accuracy and the precision of the densitometer each time before it is used to obta<strong>in</strong>the numerical density values from the control strips.Determ<strong>in</strong>e the density value of each of the two steps selected for measur<strong>in</strong>g density on thefreshly exposed and processed control strip and the density of the two correspond<strong>in</strong>g steps onthe latent-image control strip. (Once these steps have been selected, the density of the samearea on each of the steps is used every time control strips are measured.)Record the densitometric read<strong>in</strong>gs and plot them on the process control charts.<strong>Radiography</strong> <strong>in</strong> <strong>Modern</strong> <strong>Industry</strong> 126