WEBVTT 00:00.000 --> 00:30.000 position:50% align:top line:0% *This machine-generated transcript may have errors. If remediation or a manually-generated transcript is needed, please contact NLM Support at https://support.nlm.nih.gov.* 00:31.740 --> 00:31.950 Mhm. 00:35.040 --> 00:37.530 Radiographic processing is necessary for the 00:37.530 --> 00:40.080 production of the useful visible image. 00:40.190 --> 00:43.030 It links exposure to interpretation and 00:43.030 --> 00:44.360 influences quality. 00:44.940 --> 00:47.880 Discussion of a systematic approach toward artifact. 00:47.880 --> 00:50.690 Film interpretation affords the participant 00:50.700 --> 00:53.290 and understanding of the sources of artifacts. 00:53.310 --> 00:54.980 Film identification, 00:55.080 --> 00:57.550 test films and clues obtained by 00:57.560 --> 01:00.450 analyzing artifacts on radiographic films, 01:03.040 --> 01:05.630 artifact film interpretation can 01:05.630 --> 01:07.310 be an enjoyable, 01:07.450 --> 01:10.210 and yet it is a necessary aspect of uh 01:10.220 --> 01:11.090 processing. 01:11.090 --> 01:12.920 And of course the function of the department. 01:13.070 --> 01:16.020 Most of the time we have people who sort films, 01:16.020 --> 01:17.930 they look for quality positioning, 01:17.940 --> 01:18.910 correct exposure, 01:18.910 --> 01:19.740 penetration, 01:19.750 --> 01:22.690 amount of density on the film's correct identification 01:22.690 --> 01:25.350 of the patient's name and other 01:25.360 --> 01:26.460 pertinent information. 01:27.040 --> 01:28.710 But in reality, 01:28.710 --> 01:31.610 what they're doing is looking at the film to see if the film is of 01:31.800 --> 01:34.360 total acceptable quality Regarding 01:34.360 --> 01:35.120 processing. 01:35.120 --> 01:37.700 We need to look at the film to see if one 01:38.140 --> 01:40.470 there are any artifacts or 01:40.470 --> 01:42.840 to uh if indeed, 01:42.840 --> 01:45.810 we do have proper processing insofar as a sense 01:45.810 --> 01:46.750 of metric image. 01:47.140 --> 01:48.650 So what is an artifact? 01:48.660 --> 01:49.100 Well, 01:49.320 --> 01:51.640 too many people and many languages in the world. 01:51.650 --> 01:54.330 The word artifact is not used in 01:54.640 --> 01:57.410 discussing problems with our 01:57.410 --> 01:59.400 films or reasons to repeat the films. 01:59.690 --> 02:01.650 The word is a defect. 02:02.040 --> 02:04.970 So we might use the word defect or at least keep in the 02:04.970 --> 02:07.160 back of our minds when we talk about artifacts. 02:07.540 --> 02:10.510 But the best way that you might consider looking 02:10.510 --> 02:13.330 at artifacts is to simply pick up films and be very 02:13.330 --> 02:15.130 critical as to what you see on the, 02:15.140 --> 02:16.810 on the particular film. 02:17.030 --> 02:18.690 And so far as positioning, 02:18.700 --> 02:19.440 uh, 02:19.450 --> 02:20.700 the general technique, 02:20.710 --> 02:23.090 the marks on the film, 02:23.140 --> 02:24.850 the processing conditions. 02:25.100 --> 02:26.410 But in all of this, 02:26.420 --> 02:29.410 there is a systematic approach and this is what we're 02:29.410 --> 02:31.860 going to discuss in this lecture. 02:32.840 --> 02:33.600 To begin with, 02:33.610 --> 02:35.970 an artifact or defect can be 02:35.980 --> 02:38.690 a it can 02:38.690 --> 02:40.590 be something that is unwanted. 02:40.600 --> 02:42.860 It can be sensitive metric density, 02:43.240 --> 02:45.640 that is unwanted or non useful density, 02:45.810 --> 02:47.130 unwanted density. 02:47.200 --> 02:50.200 Or it could be a physical defect insofar 02:50.200 --> 02:53.150 as uh it might be a scratch on the film that 02:53.160 --> 02:56.140 would be seen as increased density 02:56.150 --> 02:59.080 because of the pressure of the scratching causing an 02:59.080 --> 03:01.560 exposure which developed into metallic silver. 03:01.640 --> 03:04.280 Or it may be that the scratch removed the 03:04.280 --> 03:04.840 gelatin, 03:04.840 --> 03:07.650 in which case now we do not have silver, 03:07.650 --> 03:10.460 We have an artifact that appears as a white mark where the 03:10.460 --> 03:11.040 silver, 03:11.150 --> 03:11.640 which should be. 03:11.640 --> 03:13.310 There has been scraped away. 03:13.840 --> 03:16.360 One of the very most common kinds of 03:16.360 --> 03:18.590 artifacts would be static, 03:18.650 --> 03:21.100 as in static electricity's we see in this 03:21.110 --> 03:21.760 slide, 03:22.440 --> 03:24.910 we have three kinds of the study. 03:25.020 --> 03:27.590 We have tree static smudge 03:27.600 --> 03:28.640 and crown. 03:28.640 --> 03:31.620 Study the tree static starts at a base 03:31.620 --> 03:33.450 and branches out as a tree wood. 03:34.030 --> 03:36.570 The crown static will start at a base 03:36.960 --> 03:39.750 and be smaller with fewer 03:39.750 --> 03:40.430 branches. 03:40.430 --> 03:42.510 And many times you even see an actual 03:42.520 --> 03:45.470 crown and a little short race coming 03:45.470 --> 03:47.730 off from the crown or sort of rounded 03:48.030 --> 03:51.000 uh static line discharge line smudge 03:51.000 --> 03:53.670 static or just a little round discharge balls. 03:53.670 --> 03:55.660 And we will look at these in greater details. 03:55.660 --> 03:57.960 We go along so we have 03:58.440 --> 03:59.560 unwanted density, 03:59.570 --> 04:02.350 that is density that you see there amongst the 04:02.350 --> 04:02.950 anatomy, 04:02.960 --> 04:05.520 anatomical densities and it's 04:05.520 --> 04:06.030 unwanted. 04:06.030 --> 04:06.560 Certainly, 04:06.570 --> 04:07.730 it is confusing. 04:07.730 --> 04:09.460 It interferes with the interpretation. 04:09.840 --> 04:12.760 Another kind of unwanted density that 04:12.760 --> 04:14.000 we might consider to be sensitive, 04:14.000 --> 04:15.960 metric artifacts or defects. 04:16.190 --> 04:18.030 Here we have three images, 04:18.740 --> 04:19.720 all identical, 04:19.720 --> 04:22.230 except for the fact that we can see better in one. 04:22.230 --> 04:24.960 We can any other consider the cloud formation 04:25.130 --> 04:26.660 in this particular radiograph. 04:27.040 --> 04:29.440 What we're talking about is contrast levels. 04:29.450 --> 04:32.360 Here we have a good moderately high 04:32.360 --> 04:34.910 contrast level in which we can see the cloud 04:34.910 --> 04:35.660 formation. 04:36.240 --> 04:39.190 We can easily see the piles of snow 04:39.240 --> 04:41.460 amongst the bushes around the base of the building 04:42.500 --> 04:43.790 in this radiograph. 04:43.800 --> 04:44.340 Do right. 04:44.340 --> 04:47.270 You see that you have quite a bit 04:47.280 --> 04:49.850 darker image here and you've lost 04:49.850 --> 04:50.560 information. 04:50.710 --> 04:52.520 You can see the piles of snow easier. 04:52.890 --> 04:54.250 The clouds are harder to see, 04:54.260 --> 04:56.560 but it's very difficult to see the window in the building 04:57.040 --> 04:58.980 coming over to the other extreme, 04:59.200 --> 05:01.570 we have increased contrast, 05:01.570 --> 05:03.460 we have very few shades of gray. 05:03.840 --> 05:05.450 Now we've lost the clouds, 05:05.710 --> 05:07.670 we've lost the piles of snow here, 05:07.670 --> 05:10.310 but we can more easily see the window in the building. 05:10.420 --> 05:12.820 So what we need is the correct level of 05:12.820 --> 05:13.560 contrast, 05:13.560 --> 05:16.440 the correct level of densities throughout the entire 05:16.440 --> 05:16.950 film, 05:16.980 --> 05:19.820 so that we can see such subtle little things as a snow 05:19.910 --> 05:22.840 starting to slide on the roof of the building so that we see 05:22.850 --> 05:23.950 all of the information. 05:24.440 --> 05:26.910 And this certainly would be one thing to consider in 05:26.930 --> 05:28.610 discussing artifacts. 05:28.620 --> 05:31.390 Do we have the best visualization of the 05:31.390 --> 05:33.540 information as the 05:33.580 --> 05:36.480 established level of quality shifted on us? 05:36.480 --> 05:38.630 Has it slowly day to day? 05:38.640 --> 05:39.860 Just lost a little bit? 05:40.340 --> 05:43.320 So we want to look for since in symmetric shifts or 05:43.320 --> 05:46.220 changes or defects or abnormalities 05:46.240 --> 05:48.720 and in the general category of an 05:48.720 --> 05:49.340 artifact, 05:49.350 --> 05:52.070 something that is unwanted in this 05:52.070 --> 05:52.900 particular slide, 05:52.900 --> 05:55.650 we can see a skull radiograph of 05:56.140 --> 05:58.530 degree of quality now, 05:58.540 --> 05:59.870 is that quality? 05:59.900 --> 06:01.990 The quality that you've selected? 06:01.990 --> 06:04.140 Is it better than yesterday or poor? 06:04.150 --> 06:05.590 Poorer than yesterday? 06:05.600 --> 06:08.360 So this would involve a judgment 06:09.040 --> 06:10.660 PN In this particular slide, 06:11.340 --> 06:14.090 we have information which can be easily 06:14.090 --> 06:16.540 seen in the contrast, 06:16.540 --> 06:19.160 the high contrast that we have in this center 06:19.170 --> 06:20.070 uh image. 06:20.070 --> 06:22.350 Of course this is a phantom 06:22.360 --> 06:24.430 situation here, 06:24.560 --> 06:27.410 it's washed away and here 06:27.410 --> 06:29.190 it's masked over with grey's. 06:29.370 --> 06:29.950 Well, 06:30.440 --> 06:33.440 in this case the grey or the 06:33.450 --> 06:36.270 lack of full penetration there is this due 06:36.270 --> 06:38.530 to exposure or have we simply 06:38.540 --> 06:39.620 overdeveloped, 06:39.620 --> 06:42.260 fogged or underdeveloped? 06:42.840 --> 06:43.290 Well, 06:43.290 --> 06:45.980 now we have the problem of saying that whereas 06:45.990 --> 06:47.950 before we had the consideration, 06:47.960 --> 06:49.760 is it at the correct exposure? 06:50.240 --> 06:53.010 Now we have to decide whether or not we have both the 06:53.010 --> 06:55.960 correct exposure or correct processing 06:56.440 --> 06:59.190 or if one is correct and the other is wrong or if one 06:59.190 --> 07:01.700 is is a little incorrect and the others tried to 07:01.700 --> 07:02.300 compensate. 07:02.480 --> 07:04.160 So we need to make decisions. 07:04.440 --> 07:07.230 We can't just continue on day after day with 07:07.240 --> 07:07.990 this unknown. 07:08.000 --> 07:09.580 So we use these clues. 07:09.580 --> 07:12.540 We use these films that we work with every day to tell 07:12.540 --> 07:13.460 us how we're doing. 07:13.840 --> 07:16.790 So in this way we can maintain 07:16.790 --> 07:17.640 consistency. 07:17.650 --> 07:20.090 We maintain efficiency in the department. 07:20.280 --> 07:23.020 Let's consider a little closer how we might want to 07:23.020 --> 07:25.780 look at radiographs insofar as looking for 07:25.780 --> 07:28.460 clues and an artifact sources. 07:29.640 --> 07:30.570 In the first case, 07:30.930 --> 07:33.340 we need to identify the sources of artifacts. 07:33.500 --> 07:36.500 This would be in the case of an exposure to the 07:36.500 --> 07:38.200 film or damage to the film. 07:38.200 --> 07:40.170 This can occur in one of three areas, 07:40.740 --> 07:41.900 Dark room and handling. 07:42.110 --> 07:44.850 This includes these four sub areas, 07:44.850 --> 07:47.370 manufacturing of the actual film delivery to the 07:47.370 --> 07:50.290 warehouses and eventually to the dealer's warehouse and 07:50.290 --> 07:52.360 then finally to the hospitals storeroom. 07:52.940 --> 07:54.960 Next we have before exposure, 07:54.970 --> 07:57.730 after exposure and after processing and then the 07:57.730 --> 08:00.560 category of exposure itself with the not the correct 08:00.560 --> 08:03.310 exposure and then processing under 08:03.310 --> 08:04.200 dark room and handling. 08:04.200 --> 08:04.860 To begin with, 08:04.860 --> 08:06.060 we have manufacturing. 08:06.070 --> 08:08.580 Several manufacturers put stencils on the 08:08.580 --> 08:09.130 film. 08:09.350 --> 08:12.250 They have almost all manufacturers have emotion numbers on 08:12.250 --> 08:15.250 the boxes so that you can catalog these and 08:15.250 --> 08:17.980 you can write them down and keep a record of when the film was 08:17.980 --> 08:19.720 delivered and how it was stored, 08:19.720 --> 08:20.770 and when it was used, 08:20.780 --> 08:23.050 all films should be stored 08:23.240 --> 08:26.100 prior to exposure within the hospital on a 08:26.110 --> 08:27.100 FIFA system. 08:27.100 --> 08:28.300 First in first out, 08:28.310 --> 08:31.240 you use the the film in a 08:31.240 --> 08:33.660 way that you don't allow film to be 08:33.910 --> 08:35.510 left on the shelf too long 08:36.740 --> 08:39.740 before exposure also means that the film is taken 08:39.740 --> 08:42.300 to the dark room and it's put into the darkroom. 08:42.300 --> 08:45.170 The pouches or bags are open and the 08:45.170 --> 08:47.920 ambient conditions within the bag are allowed to acclimate to 08:47.920 --> 08:50.830 the ambient conditions of the dark room for at least 08:50.830 --> 08:53.150 an hour before usage where possible 08:54.340 --> 08:57.340 after exposure imposes another restriction on 08:57.340 --> 08:58.460 how the film is handled. 08:58.460 --> 09:01.330 And this is where dark room personnel should be the most highly 09:01.340 --> 09:04.090 skilled and trained after exposure. 09:04.090 --> 09:06.980 After the film has been bombarded with radiation and light 09:06.980 --> 09:08.130 from intensifying screens, 09:08.130 --> 09:08.770 the film, 09:08.930 --> 09:11.340 any speed of film will be 09:11.350 --> 09:11.960 faster. 09:11.960 --> 09:14.880 That means that with an equal exposure, 09:14.880 --> 09:17.340 such as a handling exposure or 09:17.460 --> 09:19.490 pressure or static discharge, 09:19.490 --> 09:22.240 that might occur before that may not 09:22.240 --> 09:22.950 damage the film. 09:22.950 --> 09:23.960 But after exposure, 09:23.960 --> 09:26.830 the film is much more sensitive to further 09:26.830 --> 09:29.410 exposure and we end up with 09:29.420 --> 09:32.060 increased artifacts occurring after exposure 09:32.740 --> 09:33.870 after processing. 09:33.880 --> 09:35.580 We have the problems of view boxes. 09:35.590 --> 09:38.450 View boxes need to be continually clean. 09:38.460 --> 09:41.430 They need to be scanned with a common photographer's 09:41.430 --> 09:44.120 light meter to make sure that you have equal intensity throughout 09:44.130 --> 09:45.420 the light box. 09:45.490 --> 09:48.490 You need to have equal intensity from the top to the bottom 09:48.810 --> 09:49.650 and you can use, 09:49.660 --> 09:50.310 as I mentioned, 09:50.320 --> 09:51.400 a common light meter. 09:51.410 --> 09:54.150 One of the best ways to use it is to simply 09:54.160 --> 09:56.750 use the exposure values the 09:56.760 --> 09:59.650 numbers on the light meter And the light meter 09:59.650 --> 10:00.340 should read an e. 10:00.340 --> 10:00.650 v. 10:00.650 --> 10:03.270 of about 13 to provide the correct illumination. 10:03.740 --> 10:06.580 As the bulbs deteriorate or 10:06.590 --> 10:09.320 as a view box gets dirty and incidentally in a clean 10:09.320 --> 10:10.910 environment such as a hospital, 10:11.210 --> 10:14.070 it is possible to lose at least 10 of 10:14.070 --> 10:17.040 the illumination just from dust accumulating on the glass and on the 10:17.040 --> 10:17.620 bulbs. 10:17.650 --> 10:20.510 So about once a month the view box should be 10:20.520 --> 10:23.170 inspected and or clean and 10:23.180 --> 10:25.930 uh bulbs replaced bulbs should all be 10:25.930 --> 10:28.820 replaced as matched bulbs for which there 10:28.820 --> 10:31.560 is a premium charged instead of just 10:31.560 --> 10:33.020 haphazardly one at a time. 10:33.030 --> 10:35.930 Or to use common bulbs Unmatched in intensity 10:35.930 --> 10:37.350 from say a hardware store. 10:38.340 --> 10:41.040 Also should you or radiologists have a 10:41.040 --> 10:43.790 preference for uh colored bulbs, 10:43.800 --> 10:46.740 a pinkish tinge or more yellow instead 10:46.740 --> 10:47.850 of a daylight white. 10:48.240 --> 10:51.150 Then consider making an entire view bank the same 10:51.160 --> 10:53.720 light intensity or light color 10:54.040 --> 10:56.960 instead of having different colours because certain colors along 10:56.960 --> 10:59.370 with a blue tint which is in the base will 10:59.380 --> 11:01.850 accentuate or uh 11:01.860 --> 11:04.580 diminish the ability to see information. 11:04.590 --> 11:06.660 So the view box is important. 11:06.670 --> 11:09.400 It's especially important for contrast 11:09.400 --> 11:09.990 levels. 11:10.090 --> 11:11.830 As a view box is diminished, 11:11.840 --> 11:14.190 you will have less like passing through the light areas of the 11:14.190 --> 11:16.650 radiograph and your radiograph will appear to have 11:16.650 --> 11:18.160 lost contrast. 11:18.640 --> 11:20.930 It will appear this way the radiograph of course, 11:20.930 --> 11:22.480 maybe excellent contrast, 11:22.480 --> 11:23.880 an excellent exposure. 11:24.020 --> 11:24.980 Excellent processing. 11:25.140 --> 11:27.780 But the view box can deteriorate the image just as 11:27.780 --> 11:30.620 surely as any other factor going back to our 11:30.620 --> 11:31.030 Georgia. 11:31.030 --> 11:33.600 And we can say that we have these 11:33.600 --> 11:36.440 factors associated with the handling of the film, 11:36.560 --> 11:39.460 the dark room and the viewing on the view 11:39.460 --> 11:39.950 box. 11:39.960 --> 11:42.920 Of course the sorting area by the view boxes and so forth, 11:42.920 --> 11:45.410 must be kept free of coffee sugar and 11:45.410 --> 11:48.310 spills and and cigarette ashes so that 11:48.330 --> 11:50.530 the film is not damaged. 11:50.530 --> 11:52.690 In this way exposure. 11:52.690 --> 11:55.630 This involves the correct selection of screens focal film, 11:55.630 --> 11:58.260 distance bucky grids and things of this nature, 11:58.640 --> 12:01.520 processing the correct time temperature and activity 12:01.520 --> 12:04.380 relationship alignment of the transport components, 12:04.860 --> 12:07.840 making sure the processors level and things of 12:07.840 --> 12:08.450 this nature. 12:09.440 --> 12:11.390 So when you do have an artifact, 12:11.390 --> 12:14.000 try to categorize it as one of these three 12:14.010 --> 12:16.800 general areas so that you don't end 12:16.800 --> 12:18.440 up rebuilding the process of. 12:18.440 --> 12:19.040 For instance, 12:19.050 --> 12:21.650 when you find actually that it was an exposure 12:21.740 --> 12:23.150 problem all along. 12:24.040 --> 12:26.800 Now we can say that there are certain ways to mark the 12:26.800 --> 12:29.790 films to create test films that will allow you 12:29.790 --> 12:31.680 to accumulate information, 12:31.810 --> 12:34.100 you will find that it's very difficult to 12:34.170 --> 12:35.770 solve an artifact problem. 12:35.780 --> 12:36.470 Immediately, 12:36.810 --> 12:39.460 in just one step many times, 12:39.460 --> 12:42.110 you have to look at the artifact two or three times on 12:42.110 --> 12:44.610 23 films and accumulate information 12:44.950 --> 12:47.790 until you can make a valid decision as to what to 12:47.790 --> 12:48.060 do. 12:48.540 --> 12:49.620 In this particular slide, 12:49.620 --> 12:51.060 we see a listing 12:52.340 --> 12:54.500 of things to do. 12:54.680 --> 12:57.580 We feed a film and when the film drops and receiver been 12:57.790 --> 13:00.780 lifted up and lay it on top of the processor and 13:00.780 --> 13:03.620 mark the leading edge and the edge that went down the 13:03.620 --> 13:04.140 side, 13:04.150 --> 13:06.720 let's say next to the drive side of the process. 13:06.720 --> 13:08.550 Er if you wish to orientate that way. 13:09.240 --> 13:12.190 This way we know that if any marks on this upper surface 13:12.190 --> 13:14.980 where are writing is then this 13:15.000 --> 13:17.930 surface went through the process in a certain way 13:17.940 --> 13:20.590 facing upwards uh and hitting certain 13:20.590 --> 13:22.650 rollers and not hitting other rollers. 13:23.040 --> 13:25.830 So mark the leading edge and put down the 13:25.840 --> 13:28.830 date and the time and any other information that is available to 13:28.830 --> 13:29.060 you. 13:29.440 --> 13:31.770 Uh you may know that your thermometers on your 13:31.770 --> 13:34.530 processors need to be calibrated or that they are 13:34.530 --> 13:35.920 reading a couple degrees off. 13:35.930 --> 13:38.180 Don't worry about it right down the temperatures, 13:38.180 --> 13:41.080 the times any conditions that happen to exist at 13:41.080 --> 13:41.760 that moment. 13:42.340 --> 13:43.560 We can then say, 13:44.340 --> 13:45.180 okay, 13:45.190 --> 13:48.110 perhaps you can run a few films through 13:48.110 --> 13:50.640 but you do not have time to sit down and 13:50.740 --> 13:53.490 and uh shut down the processor to analyze a 13:53.500 --> 13:53.960 problem. 13:54.540 --> 13:57.450 You might want to record all data and then process 13:57.450 --> 13:59.120 some test films for referral. 13:59.120 --> 14:01.860 Later on processing the standard 14 by 14:01.860 --> 14:04.850 17 and a variety 14:04.850 --> 14:07.570 of directions will allow you to stress the roller 14:07.570 --> 14:10.060 transport assembly if you first process some 14:10.060 --> 14:11.080 unexposed films, 14:11.080 --> 14:13.760 if there's any damage done to the film that appear as 14:13.760 --> 14:16.530 black marks as an exposure that 14:16.530 --> 14:17.260 develops up, 14:18.040 --> 14:20.860 we can take another film and flash it with white light. 14:20.950 --> 14:23.420 Do not walk out into the white light 14:23.430 --> 14:23.990 area. 14:23.990 --> 14:26.960 Just turn the white lights on real fast and this will give a 14:26.960 --> 14:28.150 good black image. 14:28.740 --> 14:31.620 But if the surface of this film turns out to 14:31.620 --> 14:32.550 be brownish, 14:32.940 --> 14:35.870 then we have deactivated developer 14:35.890 --> 14:38.780 or if there's a lack of blacks as you 14:38.780 --> 14:40.170 put it on a view box again, 14:40.170 --> 14:41.960 we have deactivated developer. 14:42.440 --> 14:44.960 If there's any picking off of 14:44.970 --> 14:46.970 gelatin or scratching the gelatin, 14:46.980 --> 14:49.070 it'll appear as white marks on this film, 14:49.080 --> 14:50.560 which should be very black. 14:51.240 --> 14:54.160 These films should tell you pretty much what the problem 14:54.160 --> 14:54.600 is. 14:55.340 --> 14:56.660 Help you to identify it. 14:57.040 --> 14:59.570 Another category would be too as a last 14:59.570 --> 15:02.380 resort sort of flash of film with a 15:02.390 --> 15:04.400 light exposure such as 70 K. 15:04.400 --> 15:04.580 V. 15:04.580 --> 15:05.880 P two M. 15:05.880 --> 15:06.330 S. 15:06.400 --> 15:09.310 With par speed screens tabletop to 15:09.310 --> 15:12.110 just slightly excite the salt 15:12.110 --> 15:13.960 crystals in the film. 15:14.100 --> 15:16.650 This makes the film as sensitive as films that are 15:16.650 --> 15:19.460 normally exposed and handled many 15:19.460 --> 15:20.010 times. 15:20.020 --> 15:20.980 Uh, 15:20.990 --> 15:23.950 quality control chief technologist may review a 15:23.950 --> 15:24.530 film and say, 15:24.530 --> 15:26.200 well on these films, 15:26.200 --> 15:29.130 I don't see the artifact and yet the radiologist complains of an 15:29.130 --> 15:29.750 artifact. 15:29.940 --> 15:32.470 And that's because these films are less sensitive than 15:32.470 --> 15:34.760 the the actual patient films which have been 15:34.760 --> 15:35.700 sensitized. 15:35.710 --> 15:36.280 Uh, 15:36.290 --> 15:37.760 and then perhaps uh, 15:37.770 --> 15:40.540 the artifact is put on after it went back into the dark 15:40.540 --> 15:40.860 room. 15:44.040 --> 15:45.550 So we have clues on the film. 15:45.550 --> 15:47.760 We have the patient's name that they 15:48.340 --> 15:50.350 When it was processed and handled. 15:50.500 --> 15:51.870 We have uh, 15:51.880 --> 15:54.800 the fact that the film and the screens and the cassette never 15:54.800 --> 15:55.720 exactly match. 15:55.730 --> 15:58.200 And we know that the screens will enhance the original X. 15:58.200 --> 16:00.660 Radiation beam about 100%. 16:01.140 --> 16:03.170 So that if we look at the non screen area, 16:03.180 --> 16:05.860 we can say that if the non screen area is 16:05.860 --> 16:08.760 fogged where the only exposure is made by X 16:08.760 --> 16:09.500 radiation, 16:09.900 --> 16:12.750 that that means that if this 16:12.750 --> 16:15.480 area is also fog but not totally burned out, 16:15.480 --> 16:18.200 that perhaps the fog is not due to radiation is 16:18.200 --> 16:21.060 probably due to chemical fog because chemistry does not 16:21.060 --> 16:23.250 know where the 16:23.840 --> 16:24.930 image starts and stop, 16:24.930 --> 16:25.530 it just falls. 16:25.530 --> 16:26.150 Everything. 16:26.640 --> 16:28.750 We have the stencil mark on the film. 16:28.760 --> 16:31.640 We have the general conditions of the 16:31.640 --> 16:34.620 film and be sure to look at both transmitted light 16:34.630 --> 16:37.380 and oblique light to try to try to find different clues, 16:37.380 --> 16:39.150 as many clues as you possibly can. 16:40.340 --> 16:43.330 Now let's go to view box and actually look 16:43.330 --> 16:46.130 at some radiographs and see some of the 16:46.130 --> 16:47.280 things we might consider. 16:47.560 --> 16:50.150 The first thing to do is look at the overall radiograph. 16:50.160 --> 16:52.070 In this case we see a hand, 16:52.070 --> 16:52.850 we see the hand, 16:53.190 --> 16:56.180 the exposure of the hand has been column mated. 16:56.190 --> 16:58.090 And you can also notice that this is a phantom. 16:58.160 --> 16:59.250 So it's a test film. 16:59.250 --> 17:00.350 It's not a patient film. 17:01.240 --> 17:04.150 We know that this non anatomical area out here 17:04.160 --> 17:06.980 should be uniformly gray and it's not we 17:06.980 --> 17:09.640 see a wispy cloud pattern here. 17:09.640 --> 17:12.510 This is a desensitized king mark and exposure 17:12.510 --> 17:14.040 was placed on the film, 17:14.040 --> 17:16.850 which caused the normal black area to be reversed 17:16.890 --> 17:19.260 so that what should be black is now white. 17:19.560 --> 17:21.050 It was not developed up, 17:21.050 --> 17:22.670 it was washed away in the fixer. 17:23.340 --> 17:24.860 You won't be able to see this. 17:24.860 --> 17:26.250 But in this particular radiograph, 17:26.250 --> 17:29.110 there happens to be some wet pressure sensitization from dirt on 17:29.110 --> 17:29.510 rollers. 17:29.510 --> 17:31.670 Pressing on this film has caused some 17:32.040 --> 17:34.780 since some silver deposits in the 17:34.790 --> 17:36.020 anatomical area. 17:36.180 --> 17:38.660 And that would be most disconcerting to the radiologist. 17:38.940 --> 17:41.270 And I'll show you better examples later on 17:41.840 --> 17:43.390 in this particular radiograph. 17:43.580 --> 17:44.110 Well, 17:44.740 --> 17:47.210 it's sort of uh light is, 17:47.220 --> 17:50.100 it's hard to read the information we see over 17:50.100 --> 17:50.440 here, 17:50.440 --> 17:51.760 that there's a white speck, 17:51.770 --> 17:54.340 most likely uh debris on the screen, 17:54.340 --> 17:56.040 which is absorbed the light. 17:56.040 --> 17:58.560 So therefore there is no exposure in this area. 17:58.570 --> 18:00.910 Here we see a dark glob of 18:00.910 --> 18:03.350 dirt and this dark cloud of dirt. 18:03.350 --> 18:03.750 Did you see? 18:03.750 --> 18:06.600 There happens to be a little piece of tape on the view box that I placed there, 18:06.600 --> 18:08.860 but it could be just as easily crown markings or 18:09.140 --> 18:10.810 any other kind of dirt. 18:11.070 --> 18:14.000 It causes the interpreter of 18:14.000 --> 18:15.860 the radiograph to work a little harder. 18:16.340 --> 18:17.700 This particular radiograph, 18:17.700 --> 18:20.680 would you say that this is a processing or exposure or a 18:20.680 --> 18:22.100 handling artifact? 18:22.190 --> 18:22.420 Well, 18:22.420 --> 18:25.110 certainly the film has been ripped and taped 18:25.110 --> 18:26.720 together so that might be handling. 18:27.010 --> 18:28.190 But as you look at it, 18:28.290 --> 18:29.470 you see dirt down here, 18:29.480 --> 18:30.670 perhaps that's processing. 18:31.040 --> 18:31.770 As it turns out, 18:31.770 --> 18:34.730 this is a double exposure and the film is of no value to us 18:34.730 --> 18:35.160 anyway. 18:35.160 --> 18:36.070 So it doesn't matter. 18:36.350 --> 18:38.050 It turns out it is a process. 18:38.050 --> 18:40.270 I mean it is an exposure artifact. 18:41.340 --> 18:42.810 In the next two radiographs, 18:42.840 --> 18:45.120 we can compare sensitive metric 18:45.130 --> 18:46.070 values. 18:46.110 --> 18:47.840 You see two films. 18:47.840 --> 18:50.510 They have different contrast levels between the 18:50.510 --> 18:52.540 two and we need to consider it. 18:52.540 --> 18:52.820 Well, 18:52.830 --> 18:55.260 is one better than the other or worse than the other. 18:55.640 --> 18:56.390 Uh, 18:56.400 --> 18:57.910 there are no real artifacts, 18:57.920 --> 19:00.820 but there is a different level of quality 19:00.830 --> 19:02.960 and one is acceptable and one isn't, 19:03.340 --> 19:05.960 that will leave to your judgment the last 19:05.960 --> 19:06.740 radiograph. 19:06.750 --> 19:09.190 We can notice the Patients 19:09.200 --> 19:11.890 identification block up here and it says 19:11.960 --> 19:13.760 a date which I'll read us as 19:13.770 --> 19:15.270 1966, 19:15.270 --> 19:18.260 the month and the day and some other the X 19:18.260 --> 19:19.350 ray number and so forth. 19:20.040 --> 19:22.420 We see a very washed out fogged film. 19:22.630 --> 19:25.630 We see that it's sort of modeled and that there are these little 19:25.630 --> 19:26.380 black marks. 19:26.380 --> 19:28.860 These are chemical splashes and 19:28.870 --> 19:31.760 this sort of a rundown fogged appearance. 19:31.960 --> 19:34.610 This is a result of manually processing in 19:34.620 --> 19:36.300 oxidized developer, 19:36.310 --> 19:37.350 very old developer. 19:37.940 --> 19:38.140 Now, 19:38.140 --> 19:38.580 of course, 19:38.590 --> 19:40.180 when you read radiographs, 19:40.180 --> 19:41.440 you need to consider, 19:41.530 --> 19:44.120 as I said in the beginning that you have to look at a lot of 19:44.120 --> 19:44.720 radiographs. 19:44.720 --> 19:46.440 This sort of becomes a hobby. 19:46.460 --> 19:49.070 So let's look at a number of radiographs and see what we 19:49.070 --> 19:49.800 find. 19:49.840 --> 19:51.260 And uh, 19:51.740 --> 19:54.200 the clues that we have and will start to 19:54.200 --> 19:57.040 accumulate some guidelines that you can 19:57.040 --> 19:59.680 then go to your own discard pile in the hospital, 19:59.690 --> 20:01.120 pick out any old film, 20:01.280 --> 20:04.250 put on a view box or handle it and see what you find. 20:04.390 --> 20:07.090 And then start making notes or drawing on the films. 20:07.090 --> 20:08.360 You'll see that I've done here. 20:10.140 --> 20:11.830 So keep in mind our clues. 20:11.840 --> 20:12.500 First of all, 20:12.500 --> 20:14.060 we have the stencil on the film. 20:14.840 --> 20:17.790 This tells us in this case that this is a high speed film. 20:17.790 --> 20:18.610 It's very sensitive, 20:18.610 --> 20:21.530 It requires less exposure to give us a 20:21.530 --> 20:22.590 certain level of density. 20:22.590 --> 20:24.660 So therefore we must handle it more carefully. 20:24.880 --> 20:27.590 This kind of high speed film will be a little more 20:27.600 --> 20:30.580 critical insofar as processing and the processor 20:30.870 --> 20:33.560 mechanical condition than with a par speed 20:33.640 --> 20:34.870 type of film. 20:34.880 --> 20:37.520 A film that is less less fast 20:37.530 --> 20:38.650 to radiation. 20:38.650 --> 20:40.800 A film that would require less exposed. 20:40.800 --> 20:43.630 I mean require more exposure to give an equal level of 20:43.630 --> 20:44.170 density. 20:47.040 --> 20:48.410 In this particular film, 20:48.410 --> 20:51.180 we see that we have guide shoe marks. 20:51.220 --> 20:51.450 Well, 20:51.450 --> 20:53.740 the guide shoe marks indicate that the 20:53.750 --> 20:56.550 uh film had to be processed in 20:56.660 --> 20:58.550 this direction or this direction. 20:58.770 --> 21:00.560 And the intensity of the guide to mark. 21:00.560 --> 21:03.070 The uniformity will help you to 21:03.080 --> 21:05.550 determine which is the leading edge. 21:05.700 --> 21:08.670 This is probably the leading edge for this particular processor. 21:08.910 --> 21:11.870 The guide to mark's happen to be two inches apart and in this 21:11.870 --> 21:14.720 particular hospital it only could be produced by the M. 21:14.720 --> 21:15.200 Four, 21:15.310 --> 21:16.250 not the PICO X. 21:16.250 --> 21:17.930 You or the proof X ray. 21:17.930 --> 21:19.240 It had to be the Kodak M. 21:19.240 --> 21:20.140 For processor. 21:20.390 --> 21:23.170 And here we see another stencil on the film 21:24.140 --> 21:26.950 so that we have a number of clues right here on 21:26.950 --> 21:28.670 this blank sheet of film 21:29.820 --> 21:32.100 and incidentally those are both deposits of silver. 21:32.100 --> 21:34.820 This stencil mark is cut into the film and it is it 21:34.820 --> 21:35.950 is silver. 21:37.440 --> 21:40.440 We can see that there is a faint image of fog 21:40.450 --> 21:41.360 in this area 21:46.040 --> 21:48.870 and again the stencil mark in this particular case there is a 21:48.870 --> 21:51.450 slight staining a light yellow 21:51.460 --> 21:51.970 staining. 21:51.980 --> 21:54.050 And we'll see more of this as we go along. 21:54.440 --> 21:56.540 And the problem in this particular 21:56.700 --> 21:59.630 film was that it was processed a long time 21:59.630 --> 22:01.620 ago and it has developed 22:01.630 --> 22:04.290 uh staying in 22:04.290 --> 22:07.280 storage called archival stain or silver sulfide 22:07.280 --> 22:10.100 stain in this 22:10.100 --> 22:11.180 particular radiograph. 22:11.180 --> 22:13.950 You look quickly over the entire radiograph and you may 22:13.950 --> 22:16.320 see a little bit of dirt and so forth. 22:16.330 --> 22:18.220 But notice where the arrows are. 22:18.230 --> 22:20.460 You see something that could be anatomy. 22:20.470 --> 22:22.950 These little wispy guys are 22:22.950 --> 22:25.880 desensitized kink marks and this of course 22:25.880 --> 22:28.650 would be a problem to the radiologist. 22:28.910 --> 22:30.140 These are handling marks, 22:30.140 --> 22:33.140 not from fingernails or such is just a bending 22:33.140 --> 22:33.980 of the film. 22:34.190 --> 22:37.190 And the bending of the film has caused an area that should 22:37.190 --> 22:39.760 be exposed to be reversed 22:40.110 --> 22:41.770 and it becomes unexposed. 22:45.240 --> 22:46.010 If we look closer, 22:46.010 --> 22:48.870 we see that these are areas in which 22:48.880 --> 22:49.770 the information, 22:50.240 --> 22:52.860 the rib and so forth has been washed away. 22:52.860 --> 22:55.600 Or if you will lost in intensity. 22:56.140 --> 22:59.080 Notice also that we have a general level in these 22:59.080 --> 23:00.160 lighter areas, 23:00.710 --> 23:02.670 at a general level of fog. 23:03.140 --> 23:05.980 And over here on the non screen area where 23:06.050 --> 23:06.680 no radio, 23:06.690 --> 23:07.750 no light hits, 23:07.750 --> 23:10.230 just straight radiation that we have, 23:10.240 --> 23:13.120 The two layers of the screen screens never exactly match 23:13.120 --> 23:13.610 each other. 23:13.610 --> 23:15.680 And of course the film doesn't match either. 23:15.700 --> 23:18.370 So there's an area here where we can see 23:18.740 --> 23:19.860 that there's no exposure. 23:20.940 --> 23:23.420 And should this be fogged equal to this, 23:23.420 --> 23:24.240 where there's a very, 23:24.240 --> 23:26.960 very light exposure because of the contrast media, 23:27.540 --> 23:28.620 then we can say, 23:28.620 --> 23:28.850 well, 23:28.850 --> 23:31.720 that's most likely going to be chemical fog that 23:31.720 --> 23:34.390 this area is exposed with 23:34.400 --> 23:35.270 radiation. 23:35.640 --> 23:37.280 Remember over here where their screens, 23:37.290 --> 23:40.180 the radiation be magnified 100 times. 23:40.310 --> 23:43.140 This would be totally unacceptable insofar as the 23:43.150 --> 23:45.970 density levels and would be obvious that that was a 23:45.980 --> 23:46.950 bad radiograph. 23:50.040 --> 23:50.720 Also, 23:50.730 --> 23:52.790 we need to consider the screens, 23:53.240 --> 23:55.940 The speed of the screen that's being used many 23:55.940 --> 23:58.690 times sensitive metric artifacts develop because 23:58.930 --> 24:01.510 one type of 24:01.510 --> 24:04.180 screen is being phased out or it's left in one 24:04.180 --> 24:07.130 cassette and it has not been removed from the system as 24:07.130 --> 24:09.870 the hospital moves on to new screens or to 24:09.990 --> 24:11.350 a different speed of screen. 24:11.350 --> 24:14.300 So you need to uh make note of 24:14.300 --> 24:17.280 the speed of screen and also identify bad cassettes 24:17.280 --> 24:19.630 warped and damaged and things of this nature. 24:20.940 --> 24:23.880 This film is an interesting one is often called alligator hide 24:23.880 --> 24:25.120 or leaded glass effect, 24:25.120 --> 24:26.760 or stained glass effect. 24:27.240 --> 24:29.860 And we see that the film is also 24:29.860 --> 24:30.330 ripping. 24:30.410 --> 24:32.870 This was a tri acetate based film produced 24:32.870 --> 24:33.960 1949. 24:34.340 --> 24:35.400 If we look more closely, 24:35.400 --> 24:38.210 we can see that the film has shrunk and has bubbled 24:38.210 --> 24:39.080 up technically. 24:39.080 --> 24:41.730 This is called base shrinkage because that's the tape based film 24:41.740 --> 24:42.370 shrinks. 24:42.720 --> 24:45.260 The modern polyester bases do not 24:47.940 --> 24:48.660 this film. 24:49.040 --> 24:49.450 Well, 24:49.450 --> 24:50.190 if you look closely, 24:50.190 --> 24:51.620 you'll see a light yellow tinge. 24:51.620 --> 24:54.380 This is Dick Roeck stain up in the 24:54.380 --> 24:54.860 corner. 24:54.870 --> 24:56.910 We see a sensitized kink mark. 24:56.920 --> 24:59.600 The shape of a fingernail but not caused by a fingernail is 24:59.600 --> 25:01.640 caused by a flexing of the film, 25:01.650 --> 25:04.240 a bending of the film and where the film bends, 25:04.240 --> 25:06.750 it creates this pressure mark and that 25:06.760 --> 25:08.060 is silver. 25:09.240 --> 25:12.040 If we go to the the 25:12.040 --> 25:12.860 blackboard, 25:13.340 --> 25:16.110 this term decried stain results from a 25:16.110 --> 25:18.350 failure of the chemistry whereby, 25:19.040 --> 25:21.440 well yeah, 25:22.440 --> 25:25.370 die Croelick and we 25:25.370 --> 25:28.000 have a failure of the developer or the 25:28.000 --> 25:30.870 fixer or the development fixer are contaminated together 25:30.870 --> 25:33.530 or they're both partially uh deteriorated. 25:33.610 --> 25:35.940 And the stain that we 25:35.940 --> 25:38.670 get is a yellowish cast a yellowish 25:38.670 --> 25:39.080 stain. 25:39.090 --> 25:41.960 And this eventually we'll start producing pinks and 25:41.960 --> 25:43.190 yellows and so forth. 25:43.200 --> 25:46.170 And we end up with uh heavily stained 25:46.170 --> 25:46.470 film. 25:46.470 --> 25:49.290 But the stain occurs on the film as it's seen coming out of the 25:49.290 --> 25:49.770 process, 25:49.770 --> 25:51.560 er not after spinning stories for a while. 25:51.940 --> 25:53.670 So this is DI Kroeske stain. 25:53.810 --> 25:56.540 It begins as a yellowish tinge and may end up 25:56.550 --> 25:57.650 as a purple. 25:57.980 --> 25:58.800 And we'll see this. 25:58.800 --> 25:59.860 As we go along 26:05.240 --> 26:05.430 here, 26:05.430 --> 26:07.070 we see static discharges. 26:07.100 --> 26:08.430 If you look closely, 26:08.440 --> 26:11.410 you can see there's some smudge static up here in a random 26:11.420 --> 26:12.070 pattern. 26:12.160 --> 26:14.840 This is due to an ungrounded workbench and there's this 26:14.850 --> 26:17.050 discharge through the film to a ground 26:17.060 --> 26:19.860 grounding uh shorting system 26:19.860 --> 26:22.750 and uh the static on the film 26:22.750 --> 26:23.780 is piles of silver. 26:23.780 --> 26:24.670 It's an exposure. 26:25.140 --> 26:27.980 This line along here is a lot of little 26:27.980 --> 26:28.380 dots. 26:28.380 --> 26:31.310 It happens to be a beaded chain that was 26:31.310 --> 26:34.280 attached to a pair of scissors and this discharged 26:34.290 --> 26:36.520 uh causing the image on the film. 26:36.520 --> 26:37.170 If you will, 26:37.640 --> 26:38.730 we have white spots. 26:38.730 --> 26:41.360 This is dirt on the screens that has caused a 26:42.040 --> 26:44.050 an absorption of the radiation. 26:44.510 --> 26:45.510 If we look along the edge, 26:45.510 --> 26:47.300 we see some lines coming in. 26:47.300 --> 26:49.300 It's always difficult to determine if this 26:49.740 --> 26:52.710 blackish line is an increase in density or if 26:52.710 --> 26:55.700 in reality the darker line is normal and what is 26:55.700 --> 26:58.560 between is a loss of density as the source of artifacts. 26:59.140 --> 26:59.860 It turned out. 26:59.860 --> 27:02.460 This film was fed and 27:02.840 --> 27:04.630 a normal fashion this way. 27:04.890 --> 27:06.860 And these lines which are very, 27:06.860 --> 27:07.520 very faint, 27:07.530 --> 27:08.110 but they are, 27:08.110 --> 27:10.790 they're these lines are a result of a failure of the 27:10.790 --> 27:13.360 fixer to properly neutralize the developer. 27:13.370 --> 27:16.260 So there is slight over development on this 27:16.260 --> 27:16.960 one edge, 27:19.340 --> 27:20.290 we look more closely, 27:20.290 --> 27:22.790 we can see that this is silver 27:23.050 --> 27:24.010 smudge static. 27:24.020 --> 27:24.460 And again, 27:24.460 --> 27:26.520 we have a screen identification. 27:26.770 --> 27:29.550 We have this line from the beaded chain along the edge. 27:29.550 --> 27:29.890 Again, 27:29.890 --> 27:32.520 we have this increased density because we did not 27:32.530 --> 27:34.060 accurately stop development. 27:34.540 --> 27:37.150 There's a pile of dirt just sitting right on the surface of the 27:37.150 --> 27:40.110 film and we have dirt on the screens 27:42.540 --> 27:45.060 here we see smoke study. 27:45.740 --> 27:47.170 We can see the 27:48.740 --> 27:51.420 edge along here is heavily bombarded. 27:51.430 --> 27:53.170 We look at these things more closely, 27:54.240 --> 27:57.140 we have static again 27:57.340 --> 27:58.170 as silver 28:01.020 --> 28:01.960 smudge static. 28:04.340 --> 28:06.750 Here we see wet pressure sensitization. 28:06.750 --> 28:08.100 And this is a bombarding. 28:08.400 --> 28:09.010 Here we go again. 28:09.010 --> 28:09.930 To the blackboard. 28:09.940 --> 28:12.650 This is a bombarding of the of the film by dirt on 28:12.650 --> 28:15.350 rollers and it causes a 28:15.840 --> 28:17.160 and exposure. 28:21.340 --> 28:21.760 Let's go. 28:27.040 --> 28:27.250 Yeah, 28:28.340 --> 28:30.670 it's called wet pressure sensitization 28:31.240 --> 28:33.900 and this is often enhanced by the 28:33.900 --> 28:35.050 failure of the chemistry. 28:38.440 --> 28:41.400 Here again is another form of wet pressure sensitization. 28:41.460 --> 28:42.760 It is piles of silver 28:44.840 --> 28:47.840 and this particular radiograph there is so much 28:47.840 --> 28:50.770 pressure sensitization in this area that might be 28:50.770 --> 28:53.750 considered as a defect of the patient's 28:53.760 --> 28:54.860 bone structure 28:56.940 --> 28:58.350 and dirt on the radiograph, 29:00.940 --> 29:03.900 scratch marks from lifting a film out of 29:03.960 --> 29:05.860 the rough receiver been 29:06.340 --> 29:07.670 sensitized king mark, 29:10.440 --> 29:12.060 desensitized king marks. 29:13.940 --> 29:15.050 There's a sensitized mark. 29:15.050 --> 29:15.330 Again, 29:15.330 --> 29:16.270 you can see the silver. 29:18.840 --> 29:21.800 This is a film that's unclear due to the 29:21.810 --> 29:24.670 failure of the developer hardener and the film was 29:24.670 --> 29:27.440 over swollen and the fixer did not have enough time to 29:27.440 --> 29:29.850 fully clear and we see it's not clear and here it is. 29:30.010 --> 29:31.110 This is also stained. 29:31.110 --> 29:33.960 The film has twice the normal hyper retention level 29:34.840 --> 29:36.330 and there we see die acrylic stain. 29:36.330 --> 29:36.590 Of course, 29:36.590 --> 29:38.400 it's not a normal process film. 29:38.560 --> 29:41.560 You can see the heavy staining colors 29:42.540 --> 29:43.430 and here again, 29:43.830 --> 29:46.260 the purple color is very heavy decried stain 29:48.440 --> 29:50.400 run down and again the stain. 29:50.570 --> 29:52.460 This is also called a curtain effect. 29:54.540 --> 29:56.690 It is usually found in solar processing 29:57.010 --> 29:58.520 transport assemblies. 29:58.670 --> 30:01.020 This is an excellent example of diet coke stain. 30:01.030 --> 30:03.030 The surface will appear metallic sized, 30:03.040 --> 30:04.770 almost a gold color. 30:06.040 --> 30:07.270 And of course, 30:07.270 --> 30:10.060 when we have guide shoe marks and general staining also, 30:10.160 --> 30:11.780 so the list is endless. 30:11.780 --> 30:12.740 We can continue. 30:12.910 --> 30:15.590 But it's the kind of thing that these are just some 30:15.720 --> 30:16.970 typical examples. 30:17.110 --> 30:17.730 Again, 30:17.870 --> 30:19.040 having looked at this, 30:19.310 --> 30:22.050 take some films out of the discard bin. 30:22.250 --> 30:23.300 See what you find, 30:23.470 --> 30:24.820 mark them down and save them. 30:24.830 --> 30:27.550 Put them in a little file for yourself as you find better ones. 30:27.640 --> 30:30.350 Discard the poor examples and eventually you build up an 30:30.350 --> 30:31.740 excellent artifact. 30:31.860 --> 30:32.630 Teaching file. 31:08.840 --> 31:09.510 I want to 31:11.840 --> 31:12.050 mm