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Lung cancer screening CT examinations are performed

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with a low radiation dose exposure.

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We'll talk about why that's important

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and the importance of you

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as a radiologist knowing your protocol

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and checking your radiation dose when you're reading exams.

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So we'll look at low dose CT technique, how to verify

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what the radiation dose exposure was

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for the CT when you're reading the exam,

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and the importance of giving feedback to the CT team

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or your quality control staff when you find deviation so

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that they can problem solve

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and make sure that the dose is low.

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If you remember the eligibility criteria

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for lung cancer screening as being annually from age 50

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to age 80, if patients are starting lung cancer screening

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journey at 50,

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they're having an annual chest CT for 30 years.

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And during that timeframe, they may have an abnormal screen,

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which might require interim CT examinations to assess

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for shorter term nodule growth or pet CT and so on.

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So it's incumbent upon us to create, use a dose protocol

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that is as low as we need to be able

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to get good quality imaging of the chest.

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Unfortunately, the chest being a predominantly air-filled

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structure, we don't need a lot of radiation exposure

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to get high quality images.

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The American College of Radiology, pcit Thoracic Radiology

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Practice Parameter for the Performance

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and reporting of lung cancer screening CT includes specific

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information about elements

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of your lung cancer screening protocol.

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For example, they indicate

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that the slice thickness should be two

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and a half millimeters

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or smaller with reconstruction intervals equal

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or less than the slice thickness.

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It says the examination may be acquired at reconstructed at

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one millimeter slice thickness

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or smaller to allow for better evaluation

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and characterization of small nodules.

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In our practice, we use 1.25 millimeter images

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that are overlapped at 50% intervals or 0.625.

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So we do our chest cts at low dose

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with very thin slice thickness so

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that off the bat we're detecting and characterizing

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and we don't have any CT chest exams in our practice at

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2.5 millimeters or larger.

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So we're a 1.25 millimeter or thinner practice.

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We know that this creates extra images,

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but by using some tools that help you detect and

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and measure nodules, it can mitigate against the pure volume

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of images that you're looking at.

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The practice parameter also talks about radiation dose

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should yield a dose index volume

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of three milligrams or less.

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For a standard size patient.

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We should use lower exposure in smaller patients,

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but we don't need as much radiation dose

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to get good quality images.

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And when we use larger higher dose in patients

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that are larger size to be able to get

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through those chest wall soft tissues

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and get good quality lung pictures.

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So you'll see if you participate in the

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ACRs lung cancer screening

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Registry, you'll see that we look at dose for patients

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of different size from small to average

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to overweight to obese,

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and we look at the radiation exposure to make sure

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that not only are you delivering a low radiation protocol

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to your patients, but that it is size adjusted,

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and that's something you can see on your A

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CR registry dashboards.

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Another reference

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for radiation dose in lung cancer screening is the American

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Academy of Physicians in Medicine Example protocols.

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If you simply Google A A PM Lung Cancer screening,

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you'll quickly get to their landing page

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for protocols across all makes and models

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or nearly all makes and models of CT scanner vendors.

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You can find your scanner vendor

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and then drill down into your specific scanners for the way

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that they would recommend.

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You might want to acquire your low-dose CT chest exams.

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In screening, they follow the a CR practice parameter in

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using the thin image slice sickness and the lesser

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or equal to three milligram exposure

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for a standard size patient adjusting for patient size.

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On the bottom here is a table of small, average

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and large patients by weight category in kilograms or pounds

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and A-C-T-D-I-V range.

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That might be acceptable in those patients depending on

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what type of scanning you have

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and what type of tools you have to do as low

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as reasonably achievable exams with good image quality,

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I just pulled from their website to screenshots,

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not specific to uh, anybody's practice in particular,

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but just pulled 'em for our two CT vendors.

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And you can see that the way they are formatted,

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they have the scanner type across the top, the make

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and model of the scanner,

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and they have all the details of exam acquisition

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from scan type helical mode.

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For example, rotation time beam collation detector

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configuration, pitch speed, KV and MA noise index and so on.

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And then the planes

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and slice thickness for image reconstruction.

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So you can find this level of detail for almost every make

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and model of CT scanner and use in the United States today,

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and you can look at it and compare the protocol

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that you might be using in your practice to these

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to see if there's any opportunities

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to reduce your radiation exposure.

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You'll notice that in many

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of them there will be both a reconstruction for lung tissue

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and a reconstruction for soft tissue.

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If you're going to use in your practice a tool that helps

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to detect and measure

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or characterize lung nodules, it's important

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that you have a reconstruction that is appropriate

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and maximize or optimized for the way those tools work.

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Now, what can you do as a radiologist if you're maybe not

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responsible for the protocols in your practice,

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but you're reading lung cancer screening cts

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or you're low dose nodule followup cts?

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It's important that you can be a participant in good quality

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control and patient safety by just checking

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that radiation dose output that comes with

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Every CT that we perform.

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And if it's not in the low dose range, follow up

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with your C CT team or a QC team to let them know.

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It may be simply something to educate a new technologist

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or remind them about how

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to pick the right protocol on the CT scanner when imaging.

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So good feedback is important

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to help your whole team function well

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and give the low radiation exposure to these exams

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that is safest for our patients.

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So here's an example from our practice of an exam

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with an appropriate radiation dose

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and one that we came across with a high radiation dose.

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We have an outstanding lung cancer screening coordinator

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who looks at all the radiation doses.

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She enters it into our lung cancer

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screening registry submission.

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And so she is very adept to finding the ones

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that come at a higher dose level.

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So here we see one where the C-T-D-I-V was 2.47, so

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that is within the range that was expected

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for an average sized patient,

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but here we have that one is high, it's 5.07.

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It's above the threshold that we would expect

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to be delivering a low dose exam for.

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So what do we do? We give this feedback

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to our CT uh technologist team

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and our QC team to do some drill down into

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what factors might have happened.

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Is it related to patient size that this is what we needed

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to do to get good image quality?

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Are there other mitigating factors

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or was there an error

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that occurred in selecting the right protocol

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that maybe we should figure out ways to avoid so

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that our CT technologists can function at the highest

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level of performance?

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And in this case, the patient was unable

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to elevate their arms over the head, which

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of course made the width of the body a lot thicker

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by having the bone and soft tissue

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of the arms at each side of the patients.

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The technologist noted that in their notes

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to the radiologist

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that we can see when we're reading the examinations.

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So we could say, Hmm, higher dose than expected,

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but we have a mitigating factor

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that explained why we delivered that radiation exposure

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for this low dose CT exam.

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So if you don't have a way

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of getting notes from your technologists when they deviate

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from protocols, it's a good idea

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because it helps us explain what we see in our examinations

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and explain things like radiation exposure.

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But if you don't have that feedback,

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and sometimes we'll see a high dose

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and we don't have a note on the exam, we will again work

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with our CT team

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and our quality improvement team to look into what happened,

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to talk to the technologists, to identify ways to make sure

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that it's easy to find the low dose protocol on the

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CT scanner, for example.

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So that's a little bit about knowing your low dose CT

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protocol, why it's important for patients

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who are undergoing lung cancer screening for as much

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as 30 years of their life, if they start at age 50,

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and how you as a radiologist can check the radiation dose on

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your exams and give

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that feedback when you see a higher than expected dose.