#2                                Problems with Exposure Index (EI) Numbers                             01-15-2013

     When Fuji first developed CR back in the early 80’s, they were also the first company to invent an Exposure Index (EI) number system.  As most of us know, they went with S numbers and decided to have those numbers correspond with the speed of film –screen systems so that the higher the number the less the dose.  Unfortunately they didn't ask one radiographer anywhere in the world who would have told them that this is was not a good idea as it’s not intuitive and it’s backwards from the way we think.  Pretty much every CR vendor after them followed suite as they decided to use Logarithms.  Finally DR came into the picture and all the vendors were able to develop EI numbers that were more user friendly.  Almost all of them came up with systems that had an EI number that would double when the mAs was doubled.
     Pretty much all digital radiography equipment have some sort of EI number.  There are S, LgM, DEI, EXI, REX, EI and probably others.  These numbers were developed to tell us how much radiation made it through the patient and exposed the image receptor (IR).  The problems with the numbers are twofold:
1-      They are easily corrupted or skewed by poor collimation and/or centering (up to 75% I've found in my research).
2-      Unless one is good with math the EI numbers are difficult to use to figure out how to fix a bad technique.
     Because of these two reasons, many radiographers do not use the EI numbers when critiquing their images.  Instead they use the same methods that were used with film, which are incorrect (see my next blog on Feb 1^st that will cover how to properly critique a digital image).  These EI numbers are quite reliable, even more so when the collimation and centering are good.  This is why everyone should be trying their hardest to collimate as tightly as possible.
     There is no doubt that the EI system is not a great system by any stretch of the imagination, but it is the ONLY system we have to help us critique our technique at this point in time.  Hopefully in the near future the manufacturers will be able to create better and truer EI numbers, so all radiographers will truly know if they have used the correct technique.
     I'm not a big government guy, but I think I would be OK with Big Daddy telling the vendors that they have to all play nice with each other and figure out 1 EI system that will be universal.  It's all going to be too much hassle (and costly) for them to do it, so unless they are forced into it, I don't  think it will ever happen.  And that's just a cryin' shame.


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#1                           The Problems of “Creeping mAs/Dose” in America                             01/01/13     

     As this is my first blog, I decided to jump right in and tackle what I believe is one of the biggest problems in radiology today; and that is the over radiation that is occurring everywhere with digital x-ray (CR and DR).  As of January 1st, 2013, well over half of the radiology departments in the US are now digital.  

     The first CR equipment came out in 1983, which means it has now been around for 30 years.  That's thirty years!!  The problem is most of us never had proper training when it came to the new techniques which implements using at least 15% more kV and cutting the mAs in half.  By doing this the patient’s entrance dose is cut by 33%.  Most vendors either had facilities utilize the same techniques that were used with film, a slightly higher kV with the same or even more mAs.

     Most training consisted of being shown how to correctly set up and get an exposure and post process the image, and that was about it.  The whole concept of a “light” image on your monitor no longer exists but if the patient is under radiated the image could have mottle/noise.  To take no chances, many radiographers slowly started to increase the mAs little by little to guarantee a perfect “looking” image every time. The problem is the computer has the ability to automatically rescale the image and make it look perfect even though 5, 10, 50 times too much mas/dose/radiation is used.  The Exposure Index (EI) numbers show that the patient has been over radiated but these numbers are not utilized nearly enough (see my next blog on the EI numbers later this month).

     To make matters even worse, students don’t really learn to be as discriminating in determining the exact size of a patient so that they can use the perfect technique.  Also there is so much latitude with how much mAs can be used in digital radiography, it’s impossible for any radiographer or student to be as good with manual techniques as we had to be with film.  So each year the mAs slowly and insidiously creeps up a little bit at a time but over a 10-20 year period departments are now using double and triple the mAs that is needed    

     Finally, how do we combat this problem? 

1.     Everyone needs to be better educated about using higher kV and lower mAs.

2.     Radiographers need to teach the students how to visually access the correct size of a patient (or use calipers).

3.     Everyone needs to be better trained in using the EI numbers.