New (as of 2019) airport CT scanners

BrianShaw · Aug 21, 2021

Many of the “no damage claims” seem devoid of certainty that CT equipment was actually being used. (I did not go back to validate my memory of that impression , though).

I’m not aware that it is even possible to engineer a film-safe CT system… but that’s beyond my skill set

pentaxuser · Aug 21, 2021

Based on what you have shown us Brian, I'd be astounded if any of the film makers were now to say that on further discussion with airports and CT scanner makers that any film is safe from even one pass. My reading of what they have said until now is, in effect, that CT scanners are completely unsafe and I'd expect Ilford in its reply to confirm this.
So what remains relevant to us is what if anything they have been able to do to persuade airports( Ilford mention Heathrow only but I'd expect others to follow suit) to allow hand inspections

I hope the reply will be positive but I will not be holding my breath until I receive such a reply

pentaxuser

wiltw · Aug 21, 2021

BrianShaw said:
Many of the “no damage claims” seem devoid of certainty that CT equipment was actually being used. (I did not go back to validate my memory of that impression , though).

I’m not aware that it is even possible to engineer a film-safe CT system… but that’s beyond my skill set

X-ray = low dose, low energy single emission
CT= low dose low enegy MULTIPLE emissions (one per 'slice' taken along a single object
...in the context of medical imaging.

So inherently CT has been typically characterized generally as about 100X the radiation dose as an X-ray, in medicine. The exact dose varies by which part of the body is subjected to X-ray or CT, as the following represents!

"The scientific unit of measurement for whole body radiation dose, called "effective dose," is the millisievert (mSv).
"Extremity (hand, foot, etc.) X-ray Less than 0.001 mSv
"Chest X-ray 0.1 mSv
"Barium Enema (Lower GI X-ray) 6 mSv
"Computed Tomography (CT)–Head and Neck 1.2 mSv
"Computed Tomography (CT)–Abdomen and Pelvis, repeated with and without contrast material 15.4 mSv"

Similarly, the amount of dose for checked luggage CT vs. Security carry-on CT most likely is not the same amount of radiation, due to the proximity of people going to the gates. The slice spacing in obtaining a 3D scan determines the number of individual CT slices of total radiation accumulation (e.g., 2 mm–5 mm slices of the baggage) , but the dose per slice is also a variable. Checked baggage and the newer carry-on screening systems produce slightly higher energy x rays, which also results in higher radiation levels within the unit. But some of these systems are activated (e.g., x ray on) throughout the entire screening process to produce a detailed image of the entire baggage. https://hps.org/publicinformation/ate/q12361.html

"The National Institute for Occupational Safety and Health conducted a study to measure the amount of radiation potentially received by materials imaged from both screening technologies. Sixty-seven dosimeters were intentionally irradiated in groups of three, from one to 10 times, in "checked baggage" and traditional "carry-on baggage" machines to characterize the response of the dosimeters when directly exposed to the beam. Data from dosimeter badges passed through a traditional carry-on baggage machine showed from none to very small amounts of measurable radiation. On page 24, the study notes that the highest dose measured on a dosimeter that was passed 36 times through the machine was 4 mrem or 0.04 millisievert (mSv).

Dosimeters that were passed through the "checked baggage" system that randomly activates the x ray had highly variable doses. If the dosimeters were near the area randomly selected by the software to activate the x-ray source, a higher dose would be measured. The average dose, after 10 passes through this type of system was about 28 mrem per scan (0.28 mSv per scan).

Dosimeters that were passed through the type of "checked baggage" system that stayed active for the entire screening process had an average dose of 156 mrem per scan (1.56 mSv) per scan. The newer carry-on screening systems are expected to deliver similar doses."

BrianShaw · Aug 21, 2021

pentaxuser said:
Based on what you have shown us Brian, I'd be astounded if any of the film makers were now to say that on further discussion with airports and CT scanner makers that any film is safe from even one pass. My reading of what they have said until now is, in effect, that CT scanners are completely unsafe and I'd expect Ilford in its reply to confirm this.
So what remains relevant to us is what if anything they have been able to do to persuade airports( Ilford mention Heathrow only but I'd expect others to follow suit) to allow hand inspections

I hope the reply will be positive but I will not be holding my breath until I receive such a reply

pentaxuser

Correct on all.

The potential complexity is the various responsibilities for airport security. There is a pecking order in the US and I assume the same in other countries. To me it seems that some basic efforts to align have been made. I assume that is still possible. At top of the pecking order in US is one government agency - FAA (Department of Transportation). A mass appeal to them and their kin from the grass roots might be useful. Then there are the government screening authorities - TSA (Homeland Security Agency) in the US. They implement security measures but may not be able to change them. Appealing to them might be worthwhile so they understand why us looks are concerned. And then there are the airlines… appealing to them might help because if their customers are unhappy it might impact their business. That’s the road of airport security that I once knew. The airport authority itself, like Los Angeles Workd Airport, who operates LAX… generally nice folks but have very different concerns.

Im all for grass roots appeals. But some organization and a ring leader to get it going, direct it to the right decision makers, and keep it factual is needed. Nobody stepping up to that plate yet it seems.

Paul Howell · Aug 21, 2021

Seems that putting film in check baggage is safer than through a new carry on scanner.

BrianShaw · Aug 21, 2021

Thanks wiltw… but NIOSH data, I believe, is related to human exposure risks. Their dosimeter measures are interesting as independent validation of what the manufacturers spec sheets say. Not sure how that correlates to film safety/damage.

What we need are some real data on film being passed through carryon CT that quantifies the damage. You and I would both probably be correct to predict significant measurable damage in 1pass, even if the dosage has been “dialed down” for exposure protection of human bystanders. I assume that proper shielding is integrated into the machines to protect both operators and passengers. I doubt certification would be possible without proof of those exposure values.

BrianShaw · Aug 21, 2021

Paul Howell said:
Seems that putting film in check baggage is safer than through a new carry on scanner.

If CT is not used to scan the checked baggage. How will you know if you don’t see where you’re checked baggage goes after giving it to the skycap?

wiltw · Aug 21, 2021

BrianShaw said:
Thanks wiltw… but NIOSH data, I believe, is related to human exposure risks. Their dosimeter measures are interesting as independent validation of what the manufacturers spec sheets say. Not sure how that correlates to film safety/damage.

What we need are some real data on film being passed through carryon CT that quantifies the damage. You and I would both probably be correct to predict significant measurable damage in 1pass, even if the dosage has been “dialed down” for exposure protection of human bystanders. I assume that proper shielding is integrated into the machines to protect both operators and passengers. I doubt certification would be possible without proof of those exposure values.

Note the content of the quoted text: " Sixty-seven dosimeters were intentionally irradiated in groups of three, from one to 10 times, in "checked baggage" and traditional "carry-on baggage" machines to characterize the response of the dosimeters when directly exposed to the beam. "

But also note there is no available result for the CT machines at Security near the gates!

[edit: Quoting the full text]]

"For clarity, there are two types of screening systems used in airports. First is the "checked baggage" screening system, often referred to as an explosive detection system (similar to a computed tomography [CT] scan). The other screening is for "carry-on baggage," with which most people are familiar when they go through airport security. Carry-on baggage screening is sometimes referred to as a transmission x ray, similar to a posterior-to-anterior (PA) x ray. Newer carry-on baggage screening technologies are being installed that include the same CT scanning capabilities as the explosive detection systems. Both screening technologies generate (or emit) radiation based on the kiloVolt potential (kVp) and milliamp-second (mAs) settings, as mentioned in your question. Specific details cannot be provided for security reasons.

The amount of radiation absorbed by the materials varies greatly depending on the materials in the baggage, time in the primary beam field, and surrounding materials. All of these factors affect the amount of radiation that is also scattered from the primary beam which can vary to extremes.

The operational settings for checked baggage systems differ from the traditional carry-on baggage systems. Checked baggage and the newer carry-on screening systems produce slightly higher energy x rays, which also results in higher radiation levels within the unit. Some of these systems are activated (e.g., x ray on) throughout the entire screening process to produce a detailed image of the entire baggage. Others are activated randomly throughout the screening process to produce multiple images (e.g., 2 mm–5 mm slices of the baggage) during the scanning process. In other words, while checked baggage and the newer carry-on screening systems may emit the same amount of radiation intensity during the screening, the dose delivered to the materials will vary greatly because the unit isn't always active. Traditional carry-on baggage screening systems emit lower intensity x rays and these systems also vary with the amount of time the unit is active.

The National Institute for Occupational Safety and Health conducted a study to measure the amount of radiation potentially received by materials imaged from both screening technologies. Sixty-seven dosimeters were intentionally irradiated in groups of three, from one to 10 times, in "checked baggage" and traditional "carry-on baggage" machines to characterize the response of the dosimeters when directly exposed to the beam. Data from dosimeter badges passed through a traditional carry-on baggage machine showed from none to very small amounts of measurable radiation. On page 24, the study notes that the highest dose measured on a dosimeter that was passed 36 times through the machine was 4 mrem or 0.04 millisievert (mSv).

Dosimeters that were passed through the "checked baggage" system that randomly activates the x ray had highly variable doses. If the dosimeters were near the area randomly selected by the software to activate the x-ray source, a higher dose would be measured. The average dose, after 10 passes through this type of system was about 28 mrem per scan (0.28 mSv per scan).

Dosimeters that were passed through the type of "checked baggage" system that stayed active for the entire screening process had an average dose of 156 mrem per scan (1.56 mSv) per scan. The newer carry-on screening systems are expected to deliver similar doses.

Please note that these results reflect the potential dose to items passing through these screening systems as measured by a dosimeter calibrated for human measurements. Actual doses will vary depending on the materials in the checked- or carry-on baggage. Please see the NIOSH study for an assessment of potential radiation exposure to the workers who operate these systems.

John Cardarelli II, PhD, CHP, CIH, PE, RSO"

But NOTHING can be found to discuss dosage of the newest CT scanners at Security.

BrianShaw · Aug 21, 2021

wiltw said:
Note the content of the quoted text: " Sixty-seven dosimeters were intentionally irradiated in groups of three, from one to 10 times, in "checked baggage" and traditional "carry-on baggage" machines to characterize the response of the dosimeters when directly exposed to the beam. "

But also note there is no available result for the CT machines at Security near the gates!

That’s interesting information and probably good enough to have at least minimal statistical significance but what’s the engineering relationship between those dosimeter readings and film damage? I’ve never seen any such correlation. I’d love to see scientific/engineering assessment or data that pulls these pieces of data/knowledge together in a valid and authoritative way. Can you help with that aspect?

I certainly understand the information you provided but it still seems like it doesn’t really answer the question. We’ve had this very same discussion before.

For the legacy machines I have film damage data that quantifies in terms of several quantifiable metrics of film damage per “number of passes through the X-ray machine”. But no dosimeter readings. Maybe one could model such a thing; I really don’t think it would be tough. The legacy machine spec sheets were rather specific about the X-ray dosage inside and outside of the cabinets.

Kodak, Ilford, and enough internet experiences of real or potential film damage from a single pass through the new CT carryon devices is enough to make me fairly certain that it really doesn’t matter what a dosimeter might read when put through them.

wiltw · Aug 21, 2021

Brian,
I believe some of the complexity is inherent to the very nature of X-Ray vs. CT 3-D scan...
X ray is usually an AREA (like the area occupied by a half dozen teeth, in the case of a dental X-ray)
CT slice is a PLANE that slices thru cake, and the scan really is a bunch of parallel slices taken thru the rectangular volume. (Cone beam CT is a different animal, a fan of slices...not parallel planes)

So most information about CT is the total accumulated dose of the entire volume, with zero information provided about the per-slice radiation. If a 35mm cartridge travels perpendicular to the beam, it is subject to 8 slices thru its 40mm length in the case of 5mm slice intervals; or 20 slices in the case of 2mm slice intervals, or 4X the 'total dose'. But how badly each slice exposes a band which runs parallel to the 5' long strip of film...that is dependent on the dose per slice.

We can find no information both either slice thickness or dose per slice for either checked luggage or at Security near the gates.. In the quoted article it states, "Dosimeters that were passed through the type of "checked baggage" system that stayed active for the entire screening process had an average dose of 156 mrem per scan (1.56 mSv) per scan" but that is a measure of TOTAL DOSE accumulated by the badge, and not representative of what EACH of the many radiation slices does to the small part of the film which is intersected as each slice is taken.

Is the 35mm cartidge irradiated thru 8 different slices or 20 different slices...maybe it does not matter, as much as how much a SINGLE SLICE of X-ray does damage thru that one slice thru the film.
Assuming (for discussion purposes) it takes 10 units of radiation to ruin the film, if I do 10 parallel slices of 5 unit of radiation with a 4mm spacing, the film in the 40mm long film cartridge is NOT harmed...because 5 unit slices are each under the threshhold of film damage....and the 50 unit total does not matter (although it counts for a human)

BrianShaw · Aug 21, 2021

We are on the same page. I personally think all we need to care about is total dosage since CT slices depends on orientation of the film cartridge/roll/sheet. That just be too detailed for any practical differences.

With the legacy machines, dMin/dMax was measured but wasn’t “significant “ until multiple exposures. For the legacy CT machines (CTX5000) not only was there measurable difference of significance, but banding damage rather than overall degradation.

Banding, as you point out, due to CT multiple slice approach. ANY banding is detrimental whereas a small amount of overall damage generally isn’t… until it is.

wiltw · Aug 21, 2021

BrianShaw said:
We are on the same page. I personally think all we need to care about is total dosage since CT slices depends on orientation of the film cartridge/roll/sheet. That just be too detailed for any practical differences.

With the legacy machines, dMin/dMax was measured but wasn’t “significant “ until multiple exposures. For the legacy CT machines (CTX5000) not only was there measurable difference of significance, but banding damage rather than overall degradation.

Banding, as you point out, due to CT multiple slice approach. ANY banding is detrimental whereas a small amount of overall damage generally isn’t… until it is.

And in the examples posted by some POTN members in this thread we see evidence of banding thru some of the examples, while other posts are free from radiation exposure artifact...WHY??? I think that some examples were mistakenly identified by the poster as 'CT scanner' when they were not. Or maybe the CT slice spacing is wider for increased throughput reasons.

BrianShaw · Aug 21, 2021

If I thought I could get TSA to do it for me, I’d gladly sacrifice a few rolls of film and send one roll through once, a second roll through twice, etc… just like the consortium did many years ago. Not sure that I’d do enough trial for statistical significance without some sort of funding, however. I’m now a pensioner!

BrianShaw · Aug 21, 2021

wiltw said:
And in the examples posted by some POTN members in this thread we see evidence of banding thru some of the examples, while other posts are free from radiation exposure artifact...WHY???

As I said before… I’m not convinced that those with no damage are certain that CT scanners were used.

Possibly but I doubt it… There also was baggage scanning machines that were 2-phase: traditional X-ray unless something indicated addition screening needed, then CT. I knew about that technique but not sure how widespread it became or if it was even commercially implemented. Sounded right, though, as it improves throughput significantly.

wiltw · Aug 21, 2021

BrianShaw said:
If I thought I could get TSA to do it for me, I’d gladly sacrifice a few rolls of film and send one roll through once, a second roll through twice, etc… just like the consortium did many years ago. Not sure that I’d do enough trial for statistical significance without some sort of funding, however. I’m now a pensioner!

My idea is glue multiple cartridges at multiple orientations and spacing onto foamcore board, laid onto the flat side of a small briefcase.

10 short rolls of B&W film (e.g. 12 exp) and home processing is the cost of such a test. and someone astute enough to recoganize a CT Scanner at Security (vs. simple X-ray machine, which Kodak already told us to be safe with ISO 400)

pentaxuser · Aug 21, 2021

Presumably and frankly most of what I say and I suspect a lot of the content on this thread is based on presumption only, Ilford has had the clout" to persuade Heathrow to allow each of its films to pass through its CT scanners a number of times after which it has developed those films and reported back its findings to the "key" authorities so that they can see the effect of the scanners. From that I presume ( here's that word again) that those authorities are now also convinced that the scanners are not safe for film

I presume that Ilford on its behalf and on the behalf of other film makers has then said to the "key" authorities that they are effectively preventing all its ( Ilford's ) customers from using its product when they air travel and from there it is but a small step to asking the key authorities to look at other ways of doing security checks on film which meets security requirements but avoids scanning

I really cannot believe that at that point the subject of hand inspection which key authorities must know is available to U.S. travellers, has not come up in the film makers / air travel authorities discussions.

However to date we have heard nothing further from either the film makers or Henning so in terms of practical progress we are none the wiser

pentaxuser

BrianShaw · Aug 21, 2021

wiltw said:
My idea is glue multiple cartridges at multiple orientations and spacing onto foamcore board, laid onto the flat side of a small briefcase.

10 short rolls of B&W film (e.g. 12 exp) and home processing is the cost of such a test.

LOL... I love it... sure but you are a madmen (fondly spoken)...

That and a densitometer...

I really like "screening studies" before committing to full investigations. I'd be satisfied with just one roll, orientation random, and willing to predict that one pass would prove the point.

Please don't forget color, 120 and sheet film!

BrianShaw · Aug 21, 2021

pentaxuser said:
PIlford has had the clout" to persuade Heathrow to allow each of its films to pass through its CT scanners a number of times after which it has developed those films and reported back its findings to the "key" authorities so that they can see the effect of the scanners. From that I presume ( here's that word again) that those authorities are now also convinced that the scanners are not safe for film.

That presumption, that film is not safe in CT scanners is, without any doubt by anyone who has been paying attention over the years and knows the least amount about the technology, true. Both Kodak and Ilford know this and have provided warnings for the past few years; Fuji may have also but I rarely use Fuji so may have missed anything they have to say on the topic. That isn't the issue.

The issues are:

1. Where is the Ilford data? Seeing is not only believing, but provides credibility over generic reports that it is believed to have happened and reported to "someone". There are no trade secrets asociated with hte data and not being transparent, unfortunately, can lead some to more skepticism than learning that the study may not have been perfectly scientific.

2. Is Ilford (or Kodak or anyone else) is working with the "key authorities" to rectify the situation, like making hand checks a more commonly accepted practice in countries where it currently may not be? And what "key authorities" are they, British I would assume. I'm skeptical and would love to hear that those discussions are underway.

Those, to me, are the issues. The last of which, could be addressed in part by an well-orchestrated grass roots effort.

wiltw · Aug 21, 2021

BrianShaw said:
LOL... I love it... sure but you are a madmen (fondly spoken)...

That and a densitometer...

Please don't forget 120 and sheet film!

That test would eliminate the probability that a single roll of film was at exactly the right orientation to the beam that it could have also be IN BETWEEN two slices of the 3-D CT. I am confident that Medium Format and 4x5 sheetfilm could be excluded from the test, as ten 135 cartridges at the multiple orientations and spacings would form a comprehensive test sample. I think you meant 'dosimeter'...Could you provide a radiation dose badge so we could quantify radiation beam?

BrianShaw · Aug 21, 2021

wiltw said:
That test would eliminate the probability that a single roll of film was at exactly the right orientation to the beam that it could have also be IN BETWEEN two slices of the 3-D CT. I am confident that Medium Format and 4x5 sheetfilm could be excluded from the test, as ten 135 cartridges at the multiple orientations and spacings would form a comprehensive test sample. I think you meant 'dosimeter'...Could you provide a radiation dose badge so we could quantify radiation beam?

I was editing simultaneous to you. What I was sayin is, "I really like "screening studies" before committing to full investigations. I'd be satisfied with just one roll, orientation random, and willing to predict that one pass would prove the point."

I'm quite sure, without even knowing the slice intervals, that they are narrower than any orientation of cartridge or roll film. A slice of baloney on end... IDK...

Don't need to measure the dosage as long as you are certain that whatever the machine is engineered to provide was delivered. The machines in service are certified and monitored. It should be a very safe assumption.

But, no, I really meant DENSITOMETER for measurement of the film degradation (fogging and/or banding) resulting from the exposure.

wiltw · Aug 21, 2021

BrianShaw said:
I

But, no, I really meant DENSITOMETER for measurement of the film degradation (fogging and/or banding) resulting from the exposure.

That seems redundant...the unexposed film being subjected to the CT beam itself is defacto evidence that the Security CT beam intensity and duration 'does or does not damage film', just like the Check Baggage CT beam was proven to damage film decades ago.

BrianShaw · Aug 21, 2021

wiltw said:
That seems redundant...the unexposed film being subjected to the CT beam itself is defacto evidence that the Security CT beam intensity and duration 'does or does not damage film', just like the Check Baggage CT beam was proven to damage film decades ago.

For banding, yes, that has always been visibly evident in a single pass through hold baggage CT. Measurement would be interesting but, as you say, redundant.

If there are any other effects like fogging seen in the legacy carryon xray machines, measurement can show damage before it actually becomes visually evident. That is what was so interesting in the I3C data... there were measurable xray effects (quantifiable) even when it wasn't visually evident (qualitatively called "damage"). If one is going to do a study, why not be comprehensive and quantify the effects as well as doing qualitative assessment?

I'd volunteer my densitometer but left it in the lab several jobs ago.

As I said and think you might agree... one roll; one pass... I think it would speak for itself. BTW, what speed film... low ASA, I assume. I propose PanF. I really love scientific method and solid research, but this should be easily addressed in a simple screening study.

BrianShaw · Aug 21, 2021

wiltw... at this point I think we are in fundamental agreement and further discussion is either at detail level or somewhat moot. I really wish we could meet somewhere halfway and have coffee/beer/cocktail and some pleasant chatter. Wine in Paso Robles????

wiltw · Aug 21, 2021

BrianShaw said:
wiltw... at this point I think we are in fundamental agreement and further discussion is either at detail level or somewhat moot. I really wish we could meet somewhere halfway and have coffee/beer/cocktail and some pleasant chatter. Wine in Paso Robles????

Brian, thx for the invitation, but I will pass on the opportunity to drive 3 hours for each of us and have coffee/beer/cocktail and some pleasant chatter, and then drive 3 hours back....especially when there is Zoom vs. spending $4.79 a gallon for gas.

As for PanF...that ancient no longer avalable stuff? Starting with accumulated cosmic radiation over how many decides?! My illustrated film test would be with ISO400 as the minimum. Is Ilford Delta 13200 emulsion still made?!

BrianShaw · Aug 21, 2021

Ancient and no longer available? I just bought some at Freestyle. But good point… fast film first!

New (as of 2019) airport CT scanners

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