# 12                  HOW LOW CAN YOU GO?                  6/15 /13

     This is how I teach ALARA (As Low As Reasonably Achievable) to all of my students and whenever I give any kind of talk on digital radiography techniques to students or techs.  It's all about using the smallest/lowest mAs possible so that the dose is as low as it can be.  This can only be done by using the optimum kV (see blog #7 "Optimum kV for DR & CR Equipment" from April 1), which is a noticeably higher kV than was used with film.  With a higher kV, less mAs can then be used.               

     This new technique is only the first step in discovering how low you can go, although by adding 15% more kV and halving the mAs the entrance dose to the patient will be cut by about 33%!!  With such a quick and obvious way to save a patient 1/3 of the dose, you would think everyone would want to be doing this.  The fact is though, that instead of techniques being at an all time low (about 75% of the country now uses digital equipment which can employ lower doses than film) mAs/Dose Creep has occurred.  To read more about that, please see my first blog " The Problems of “CreepingmAs/Dose” in America" from January 1.

     The second step is knowing how perfect the image needs to be.  Some radiologist's want an image with absolutely no noise/mottle in it while others are absolutely fine with a little bit of noise.  In fact, the radiologist's at my hospital (Community Hospital of the Monterey Peninsula - CHOMP) want to see a little bit of noise.  This is called acceptable mottle and they actually dictate this term into their reading.  They know that by seeing a little bit of mottle we truly are taking the mAs/dose as low as we can go.  They also know that they cannot miss any kind of pathology with this small amount of noise in the image.

     I tell the students and radiographers that I would love it if they would make getting the lowest mAs a competition.  It is total bragging rights for whoever can use the lowest mAs for any given body type/size.  As the software in our digital computers allow for an inordinate amount of over radiation and still get a get a perfect looking image (automatic rescaling), the skill of "technique-ing" is becoming a lost art.  To see this first hand, go to the archive section in my Current Research and look up "Howmuch can you over-radiate and still get a perfect image?". 

     Basically anyone can use too much mAs and still have a perfect image every time, so that doesn't really take any talent.  What does take real technique-ing skill is to make an exposure that is very close to whatever Exposure Index (EI) number shows that the minimum amount of radiation was used.  My goal is to go for the perfect EI number to 50% more than that number.  If I am in that zone I know I nailed it!!

 Link to Digital Radiography Solutions Website

# 11       Supertech is our newest advertiser        06/01 /13

     Today's post is going to be a bit different than my usual fair of writing about  CR and DR.  Today I'm going to tell you about Supertech.  Although you may think I'm writing this about you,  Supertech is actually this amazing diagnostic imaging online store that is celebrating its 40th anniversary this year.

     If you've been to my website you know that I have two company's advertising on the right hand side of the home page.  The beauty of running my own business is I get to pick who I will do advertising with.  I decided when I founded the company and website it wasn't worth the money to have anyone on the site that I didn't have 100% respect for.  That's why I started with just 2 businesses, MTMI and the Ferlic Filter Co.  Now Supertech makes three.

     Needless to say, all great companies need a strong leader, and Supertech most certainly has that.  The president/CEO and owner is Judy McNitt-Mell, an amazing woman who started working with Supertech ten years ago.  Her father actually started the business back in 1973, owning just 10% of the company, but over the years ended up owning it outright.  In 2009, Judy's father retired and she took control of the company lock, stock and barrel.

     I've met Judy a few times over the years because I would see her in the vendors room at many of the largest radiology conferences around the country.  One can't walk through a vendor's room without stopping at her booth, because Supertech has so many different products they sell. 

     Here are just a few of them: X-Ray Technique Calculator, Anthropomorphic and Multi-Modality Phantoms, Quality Assurance Phantoms, Aprons, Barriers and Filters as well as pages of other products for CT, Ultra Sound, MRI and Nuclear Medicine.

     I had personal experience with Judy's wonderful customer care when I purchased ALL of our phantoms from Supertech many years ago.   We started with just the abdomen phantom, but a few years later we were able to acquire the head and neck, thorax, entire right arm, elbow and the wonderful "DUKE" quality control phantom.   I still remember thinking how incredibly knowledgeable  she was (and is!!) about all of these different phantoms considering how many different products they carried. Being the inquisitive guy I am,  I had grilled her as I wanted to know everything about every one of them.

     One of the things Judy is proudest of is the SPoRT Pediatric Sectional Phantom.  She had attended several meetings which addressed the topic of pediatric imaging.  The big push for "Image Gently" made her think that it would be helpful for the market if there were Pediatric Phantoms which would help new technologists learn how to image gently.  Telling someone what to do and having something for them to use in a laboratory setting are vastly different.  Judy knew that Computerized Imaging Reference Systems, Inc (CIRS) would have the engineers and physicists who could handle a tough project like this.  She was very grateful to CIRS for creating SPoRT and she is very excited about this product.

To check out Supertech, click here.

     

#10         Shamelessly Plugging My First Textbook      May 15, 2013

     My first published book just hit the stands (or would have hit the stands if there was such a thing as a bookstore anymore) this week, so I thought you the reader wouldn’t feel it was too inappropriate to shamelessly plug my baby “Adaptive Radiography with Trauma, Image Critique and Critical Thinking”.

     As some of you might know, I spent all of 2010 as the Subject Matter Expert (SME), writing and outlining the chapters and choosing the images for an Anatomy and Positioning Textbook for Lippincott, Wilkins and Williams.  At the end of the year the project was cancelled and so were my dreams of being a published author.

     A few months later I met an old acquaintance of mine, Quinn Carroll, who had just finished writing the first ever physics book for digital radiology– “Radiography in the Digital Age”.  In addition to his physics book masterpiece, he had also been writing a positioning book that would have all the “tricks of the trade” in it.  Or in other words, everything that is not in Merrill’s and Bontrager.  Those two books show how to position the average patient where our adaptive radiography book was created to show how to position someone who for whatever reason cannot move or be moved into that position.  Hence, you now need to adapt.

     When we met, his editor had just told him that he needed a lot more positioning tips and tricks, but he had written everything he knew.  So he offered me co-authorship of the book and I was back in saddle once again!!

     So I started putting together all of my information and Quinn rewrote the text to it.  For the next 6 months we kept this up and by the summer of 2012 we had the book finished.  Of course that is just step one in the long process that takes a finished manuscript and turns it into a book ready to be sold.  There were peer reviews, rewrites, artwork, etc…  So here we are just under a year later and the book is available for sale!!

     If you have already surveyed my website, you know that I have a section on the bottom menu bar called Adaptive Radiography.  If you’re interested in finding out more about the book, here is the place to do that:  http://digitalradiographysolutions.com/AdptRad.html

Link to Digital Radiography Solutions website

#9       How Much Off-Focus Radiation Comes Out of the Tube?                         5 /1/13

     Today's blog is about off-focus (stem) radiation which until a couple of weeks ago I had completely forgotten about.  As a reminder to all of you who haven't cracked open your physics books in a while; off-focus radiation are x-rays produced by stray electrons that interact at positions on the anode at points other than the focal spot and are emitted at angles not in the primary beam.   This turns out to be a truly amazing subject when it comes to patient safety and shielding.  So much so that I have also put it in my website as the newest Current Research so you could see the photos, images and doses. 

     Last month my student Ian asked me if one should shield a patient having a PA chest in the front or the back.  I told him we had that same discussion in my class 37 years ago and that I still had no idea what was the correct answer.  We had figured that shielding in the back really didn't do much as most of the scatter occurred once the radiation hit the body or happened inside the patient.  Shielding in the front seemed like it might be more beneficial because maybe there was a certain amount of the exit beam that hit the Bucky and bounced off back at the patient.                                                                                                                             

     I decided to test this out using an 8x10 CR cassette that I would run at 1200 speed, making it extremely sensitive to any radiation.  In an upcoming Current Research I will show you exactly what we discovered when we put this age old question of front or back shielding to the test.  One thing that was extremely obvious right off the bat was how much radiation hit the cassette when placed on the back side (facing the tube).  I had hung the cassette lengthwise with paper clips taped on and every clip showed up on the image.  What made this so incredible was that none of the cassette was in the primary beam.

     So where was all this radiation coming from?  We thought it might be radiation that had scattered from the molecules in the air, but that seemed unbelievable.  After speaking with my colleague Quinn Carroll (who recently wrote the physics book "Radiography in the Digital Age") he told that this kind of scatter would be physically impossible.  We then thought it might be leakage radiation coming through the collimators.  After showing my research to an amazing group of physicists I am in contact with, they determined that it is off-focus radiation.

     I now changed the experiment to have as few variables in it as possible.  I wanted to use my dosimeter so that I could have exact readings as to how much dose was being emitted that was not in the primary beam and I already had ideas on writing this up for a peer reviewed article for the ASRT Journal.   I used a large conference room and our AMX portable machine so that I could hang my ion chamber with nothing remotely near it to cause back or side scatter.  I then made close to 400 exposures (for a peer reviewed experiment all "projections" need to be done 5 times and then the average is taken from that).

     I collimated the beam to 14x17 at a 72"SID with the bottom of the light field just above the ion chamber.  I used 2 average chest x-ray techniques: 85 kV @ 3.2 mAs and 115 kV @ 4 mAs.  Then I moved the tube 1" higher and made those 10 exposures again and continued an inch at a time.  With the 85 kV technique I needed to go 14" higher before the readouts were not accurate anymore.  With the 115 kV technique I was still getting precise readouts at 28" above the ion chamber but the tube could not go any higher.  I also did the experiment at a 40" SID using 85 kV @ 16 mAs to show how this would all pan out for an average abdomen technique.

     What has been proven so far is there is definite radiation below the collimated light field, more so on bigger techniques.  Although the dose is in the MicroR's (1/1000ths of a milliroentgen) one needs to be aware that there is a noticeable dose hitting the body outside of the primary beam.  My hospital has a 100% shielding policy, but if yours doesn't then you should definitely be aware of how much extra radiation is getting to your patient.

Please go to the Current Research to see what all this looks like.   

    

Link to Digital RadiographySolutions website 

# 8       Universal CR & DR Technique Charts        4/15/13

     Back in the film days I would always give my students a technique chart that had about 50 different body parts on it.  When we went digital in 2002, our vendor told to use the same techniques, so we continued to use those charts.  Four years later we had learned all about the new optimum kVs from Barry Burns (for more information on optimum kV or why you would want to use a higher kV and lower mAs see blog #7 from April 1^st). 

     In addition, Barry had taught us that all the manufacturers used the same style of x-ray tube and all large facilities used the same high frequency generators.  Most important was the fact that regardless of what the manufacturers called their Exposure Index (EI) number, they all got their perfect EI number if the image receptor received 1 mR (for more on EI numbers and their ranges see blog #2 from January 15^th). 

     Because of this I had the idea that a universal technique chart could be created, but needed to talk it over with Barry first.  He agreed that as long as the x-ray room had a modern high frequency generator (all hospitals and large facilities have used only these generators for the past 25 years) then a universal chart was absolutely feasible.  So I took my film/screentechnique chart, had my student Callie DeGuzman sit at the computer with a blank Excel chart in front of her and I did the 15% and 7 ½% Rule changes to the old techniques and came up with the new ones using the higher kV and lower mAs.  Then we did this over 190 times and when we were finished we had a fully functional CR Universal technique chart. 

     Soon after our radiologist’s let us cut the mAs in half for every exposure (except for abdomen’s which had too much mottle/noise).  These new images had a tiny bit of noise, which our radiologist’s called “acceptable mottle”.  When you go my website and go into All Charts, you will see many versions of the CR technique charts.  The first one is titled “Least mAs”, and the next one is “33% More mAs", then "66% More mAs" and finally "100% More mAs".  What this means is there are 4 sets of charts which will work for all manufacturers except Konica, which has its own set of 4.  The first chart titled "Least mAs" has the lowest amount of mAs, or in other words, the lowest dose.  It would also have the biggest possibility of having images with mottle/noise.

     So what I suggest to everyone is to do the following: Start with the "100% More mAs" chart and see how it works in your department.  If the images are coming up fine and the EI number shows that you can use even less mAs, go to the "66% More mAs" chart.  If the EI number shows you can continue to drop the mAs, go to the "33% More mAs" chart.  Lastly you might be able to drop the mAs/Dose all the way down and begin using the "Least mAs" charts.  As I mention in the disclaimer, your radiologist should always the final word if your image is diagnostic. 

     A few years later two DR rooms were built into our new emergency department with third generation GE using Cesium based detectors.  Immediately we noticed that the techniques were noticeably less than our CR techniques.  Two years after that we had three Siemens DR rooms installed in our main department and from there I could now compare techniques between these two major manufacturers.  The Siemens Rad room has two built in Cesium based detectors while the fluoro rooms use a tethered Canon detector (Gadolinium based).  During this time I discovered how similar both the GE and Siemens techniques were.  It took a full 6 months of studying, writing and comparing techniques before I was able to develop the Universal Cesium and Gadolinium DR technique charts.  These charts are pretty self explanatory, other than you need to know if your detectors are Cesium or Gadolinium based.  The Gadolinium detectors use just about 50% more mAs than the Cesium detectors.

#7                 Optimum kV for DR & CR Equipment                 4/1/13

     As soon as the film-screen combination was developed in our profession, there has been optimum kVs used for every body part.  Even when Rare Earth screens came on the market in the early 80’s and the mAs was cut to one third (from 9 to 3 for example) the kV stayed exactly the same.  This is because these kVs were perfect for the density and molecular make up of that body part.  This is also why we use the same120 kV on a chest x-ray for a 100 or 300 lb. patient.

     The beauty of knowing, and using, the optimum kV is you are always using the perfect kV.  By using the optimum (or in other words the best) kV, it also means that any technique problem you will ever encounter is mAs related, not kV.  This concept holds just as true today with digital radiography as it did with film except for 1 huge difference.  The optimum kVs are now higher with most of the body parts.

     Back in the early days of CR Barry Burns, an adjunct Professor of Radiologic Science, University of North Carolina School of Medicine in Chapel Hill, now retired, who was also a radiographer and physicist, immediately realized that the optimum kV for film was not the same as CR.  After careful research and experimentation, he discovered that when using CR everyone can increase 15-20 kV from film/screen techniques (except Konica which is 5-10 kV).  When both Gadolinium and Cesium based DR detectors were introduced, it was discovered that they too could use kVs 15-20 higher than those used with film/screen.

     To see these “new” optimum kVs, please go to All Charts on the Homepage and view chart 1 and 2 (Konica).  You will discover that with the exception of chest, barium work and pediatrics, all other body parts have a very noticeable increase in kV.

     Why would you want to increase the kV in the first place?  This would be so you could decrease the mAs.  By increasing the kV 15% and cutting the mAs in half (what most people call the 15% Rule), the entrance dose to the patient is decreased by 33%.  This is such a simple way to cut one third of the dose to your patient.

     As always, it boils down to patient dose.  How high a kV and how low a mAs can you use and still have a perfectly diagnostic image?  That’s the question we all need to be asking ourselves before every exposure. 

     In the upcoming months I will have at least two more articles related to this subject.  They will be “CR & DR Universal Technique Charts”, which is pretty self explanatory and “How Low Can You Go?” which will discuss how low can you take the mAs (dose) and still get that perfectly diagnostic image.

Link to Digital Radiography Solutions website 

Blog #6                                                                       3/15/2013             How much can you over-radiate and still get a perfect image?                                                                                                                                                                                                                                 

I decided to write and post this blog on the same day I changed my current research on my website.  This subject is one of the most exciting and scary things that is happening in our profession at this time.   If you go to the Current Research section, you’ll see handfuls of images proving that 5, 10, 50+ times too much mAs can be used and the images all look the same.

When I first started going to lectures on digital radiography, I heard that using 3-4 times too much mAs would cause noticeable changes in the images contrast and resolution.  This didn’t seem to match what I was seeing with our CR and DR equipment, so after a year of pleading and begging, CHOMP bought four phantoms and digital dosimeter to go with our abdomen phantom.  And with that; the “game” to finally understand what we were doing was on in earnest.

The first blog I wrote was about Creeping mAs/Dose.  I explained that one the reason’s this is occurring is because the digital computers all have the remarkable ability to automatically rescale the image.   So now an unbelievable amount of mAs (meaning way too much) can be used and a prefect image is created almost every time.

Without a body phantom to experiment with, it is impossible to see how easy it is to over-radiate a patient and still have a perfect (or at least very passable) image.  I have now been able to use my skull phantom on nine different manufacturers to determine how much mAs can be used, and over-used.  Currently I have four CR and five DR vendors.

From the experiments I’ve performed, all of the CR manufacturers except Agfa have the ability to “fix” an exposure that has been over-radiated by more than 50 times.  That is automatic rescaling at its finest.  It is also why no human being can see if an image was only over-radiated 2 or 3 times too much.  This is why it is impossible for anyone to be able to look at a monitor and tell if the patient was over-radiated, unless enough radiation was used to create burn on the image.  This is also why the EI numbers are the only way a radiographer can tell if the technique was correct.

I could go on and on (and do when I get to this section of my lectures) but I just hope you have a few minutes to go to the Current Research section of my website and see the images for yourself.  If there ever was a time where a picture is worth a thousand words, it will be there.

Link to:  Current Research