#4    The Trouble with Post Processing “Collimation”    2-15-2013

     Post processing “collimation”, shuttering or cropping seemed to be one of the greatest features of digital radiography.  With our first CR unit we were taking badly collimated chest x-rays and then with a couple of mouse and key strokes turning in images that looked like we were the best collimating super techs in the world!! 

     After almost two years of this one of our radiologist’s finally realized something weird was gong on and asked what we were doing.  When we told and showed him, he couldn’t believe it.  He immediately told us that what were doing was basically illegal as the radiologist is legally responsible for every bit of anatomy that was radiated and appeared on the image receptor (IR).  This rule has not changed one bit since the film days.

     The predicament we have with this is no one even knows it’s a problem.  I know for a fact that in one somewhat large U.S. city two different hospitals were sued because the radiographer cropped out anatomy that was later proven to have shown a tumor.

     Picture this:  You take a lateral C-spine and get almost the entire mandible on the image.  You don’t notice that there is a small tumor in the mandibular body so you crop out almost the entire mandible, leaving just a perfect looking lateral C-spine.  Six months later lawyers looking through every image taken on their client sees that your images would have shown the tumor half a year ago.  Six weeks ago the patient had to have a huge part of their mandible excised in surgery because of the fast growing cancer.  Your hospital is now being sued for five or ten million dollars and they are not even going to try to fight it because it would be impossible to win.  It was completely your fault and everyone knows it.

     Now I know you haven’t heard about these two cases. Also if it’s happened twice in this city, what are the odds it hasn’t happened countless times in cities all over the country?  The reason this is still a secret is because the hospital is willing to hand over this incredibly large sum of money with one stipulation, and that is a gag order is invoked whereby no one is allowed to talk about the case.  So until the day a patient decides to have their day in court, we are not going to read or hear about this.

     So there are only two ways you can post “collimate” and have it still be legal.  First is to only crop out areas that are outside the border of the body tissue (white or black areas).  Second is to make a copy of the original image and turn it in along with the cropped version.

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#3                                How to Properly Critique a Digital Image                                  2-1-2013                             

          We have had hundreds of digital equipment training hours at my hospital in the past 10 years, but in all of that I don’t remember any time given in learning how to correctly critique the image.  I have to imagine this is the same with everyone around the country, possibly the world.

          Last month I wrote about how reliable the Exposure Index (EI) numbers are, especially when the collimation and centering were good.  Today I am again to reiterate that these numbers have to be a huge part of the critiquing process.  Without the actual phantom lateral skull images I use in all of my talks to prove my point, we are stuck with you just having to believe me. 

          I have taken my skull phantom and shot 9 different manufacturers to prove exactly how much mAs can be used and still have a passable image.  Depending on the vendor one can use from 10 - 100 times too much mAs and still have a perfectly passable image, if a visual check is the only guideline being followed.  This is why the EI numbers must be used.

          Sometimes a radiographer will “post collimate” or “shutter” an image which depending on the vendor may change the EI number.  As a huge side note, if any of the actual body is cropped out during this process, the image is now open for a lawsuit (see upcoming blog #4 on Feb. 15^th).

          Another “tool” to use is the magnification mode button.  Quite often burn or mottle can only be seen with the image, or part of the image, being magnified.

          The last “tool” to use is Level/Windowing.  Whether your facility allows you to Level and Window the image and send it to PACS, all departments should allow a radiographer to Level and Window and then reset it before sending it to PACS.  Whenever an image does not look perfect, one should always Level and Window it and see if the image can be made to look perfect (or at least much better).  If after Level and Windowing the image does not look better, it is impossible to know if the radiologist can make it look better.

          So as a quick synopsis, the 3 things that should be done to properly critique a digital image are:

1-    Check the EI number

2-    Use the magnification mode to check for burn and mottle

3-    Level and Window the image and either reset it or send it depending on your facility’s protocol

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