Just too good to be true

Steven Koepke, who goes by koepkesd @ Stocktwits and Steven @ Yahoo, has been busy reading this blog while trying to justify the lies by the Nanox CEO that somehow the $200 (or $100, depending on the day) Nanox.Tube can replace the $150,000 modern CT tube (these are "list prices," of course).

For the longest time I was trying to figure out how Ran can claim that his field emitting device (FED) can generate x-rays on par with the high end x-ray tubes used in CT machines. Those large tubes can generate 800 to 1,000 mA at 120 kV. They also cost $120,000-$150,000. Here is the math. The MEMS (FED) chip has an active area of 0.126cm^2 (4mm diameter on chip in diameter and the power level was communicated at 2.5A/cm^2. The power is concentrated down via focusing device onto the tungsten anode. The basic math provides the power of the beam to be 314mA and 120 kV (per conference call last week). That's quite close and running multiple sources in parallel amplifies the power. Cost comparison: 5 small tubes @ $100 vs $150,000 for singe large CT device tube. Micro-X has a similar arrangement working today with a CNT device (also Field Emitting Device)

 

So, what's wrong with his reasoning?

There is no such thing as a field emitting device.  FED refers to a failed display technology -  a field emitting DISPLAY.  It does not contain "a field" of emitters, as Nanox CEO believes - it emits electrons induced by an electrostatic field.  It is not a more efficient or a cooler way to generate x-rays - all x-ray tubes, whether using a cold cathode (based on the field effect) or a hot cathode (using a hot filament) to emit electrons, have about 1% efficiency as 99% of the energy applied to the tube gets wasted as heat at the anode.  A hot filament uses a lower voltage - about 4V - than the 40V (or way more) needed by a cold cathode.  Roentgen discovered x-rays in 1895 using a cold-cathode (gas discharge) tube.  GE invented the hot-cathode x-ray tube in 1913 and obliterated the cold-cathode ones.

The proposed Nanox.Source chip is not MEMS, as there is nothing mechanical about it.  The chip is not real, or commercially available, of course, as Nanox has no ability to manufacture it commercially, at least not yet.

The current density of 2.5A/cm^2 comes from a fraudulent, that is, intentionally misleading, 2015 datasheet by Nanox predecessor, which I have previously linked here on this blog. 

The Nanox.Tube cannot do 314mA and 120 kVp.  The one used in the Nanox.Cart can do up to 2mA and up to 40 kVp, at most (or 0.08 kW, per 510K summary).  The CEI one can do up to 1mA and up to 100 kVp (or something like 0.1 kW, per CEI video).  The tube used by GE in the predicate device for Nanox.Cart can do about 40 kW - it has a rotating anode.  The CT tube can do about 120 kW (using Steven's numbers). So, to replicate the power of a $150,000 CT tube, one needs to use, oh, something like 1,000-1,500 Nanox tubes that cost $100,000 or more.  An after-market CT tube will cost less than $100,000, of course.  All this has been already discussed last year.

Micro-X has a 4.8 kW tube (a bulky stationary-anode one) - it uses carbon nanotubes, which Nanox says is impossible - it sells a few units a year.  The biggest CEI tubes are smaller sizes than Micro-X's and go up to about 2.5 kW (also stationary-anode ones).  

Update June 10, 2021:  Investors will eventually blame Nanox CEO for their delusions.  Steven continues:

The anode temperature becomes the challenge with the NNOX tube. CEI states that their tubes can handle about 60KJ. The RSNA video shows the bed is moving through the sources quickly (15-20 seconds for whole body). My guess is that NNOX is using high current short bursts to keep the anode temperature under control. In the video they may have used 300mA for up to 0.2 seconds to make 10 shots (capturing 8" per shot) while the cart moves through. 300mA x 0.2 X 10 shots = 60KJ. You can't shot this with dental tubes like that. They don't have the current and the image gets too blurry.

He is right that a typical dental tube (which has a better performance than the Nanox tube) cannot do 300mA.  He is also right that at some point, the heat capacity of the anode becomes a challenge (the anode temperature is not really a problem - it is the temperature of a part of the anode, the tungsten target, that is the challenge).

But Steven does not understand what heat capacity means.  Yes, one of CEI's most powerful medical tubes, OX125-06, can handle 60 kJ (CEI only makes stationary-anode tubes).  But that does not mean that it can do 300 mA or that 300 mA  x 0.2 s  x 100 kVp  x 10 shots = 60 kJ.  Nor does it mean that you can do 5 A x 0.2 s  x 60 kVp x 1 shot.  CEI provides nice charts in its datasheets to explain the interplay between heat capacity, tube current, tube voltage, and time.

As the charts show, the tube cannot do more than 35mA at 60kVp for 0.1s or more than 20mA at 110 kVp for 0.1s. But it can do 15 mA at 100 kVp for 10 seconds.  The RSNS 2020 demo, which we now know was fake, never demonstrated a full-body scan - it scanned three phantom "organs." The "hand" scan consisted of 45 "shots" or images ( 5 tubes x 9 tilts/translations) - it took about 50 seconds for the images thumbnails to appear on the display.  That is about 1 second per shot, not 0.2 seconds (and we don't know what that's even real).

The CEI OX-70, a dental tube,  can do about 32mA at 60 kVp for 0.1s or more than 20mA at 90 kVp for 0.1s.  It can do 10mA at 90 kVp for 10 seconds.  Here is some summary table from CEI's datasheets.  Stationary-anode tubes all look kind of the same.  The tubes that do less than 100 kVp are "dental" and typically tolerate half the current than the "medical," and are a bit smaller. 

Model	Voltage  kVp	Current mA, 0.1s	Current mA, 100kV	Focal sp. (mm)	Diam. (mm)	Length (mm)
Small/Dental tubes
OX/70-P	70	19	N/A	0.8	30	72
OX/70-5	70	11	N/A	0.5	30	72
OCX/65-G	70	12	N/A	0.8	30	76
OX/70-4	70	9	N/A	0.4	30	72
OX/70	90	21	N/A	1.2	30	82
OX/90	90	9	N/A	0.5	30	83
OCX/70-G	70	12	N/A	0.8	30	65
OCX/70-G4	70	8	N/A	0.4	30	65
Medical/Mobile tubes
OPX/105	110	18	2.5	0.5	42	125
OPX/105-4	105	17	2.5	0.4	42	95
3D/cone-beam CT tubes
OCX/100	105	20	4	0.5	46	140
OX/100	100	26	1.5	1.0	35	85

Recall, the Nanox tube in Nanox.Cart can do only 2mA at 40 kVp (for 0.1s -1 s).  The CEI Nanox tube can do only 1 mA at 100 kVp for 40 seconds (per CEI video).  The CEI OX-70 dental tube can do about 40 mA at 40 kVp for 0.1s, about 25 mA at 40 kVp for 1s, and about 3 mA at 90 kVp for about 40 seconds (per datasheet charts).  If Nanox tubes perform like poorly-made hot-cathode dental tubes, they probably are.  No mystery Nanox.Source chip required.

Update June 10, 2021:   Just to clarify, regular dental tubes (just one or 5 ) can definitely replicate the fake RSNA 2020 Nanox.Arc demo.  The "hand" scan took about 50 seconds for 45 images.  Let's see whether a dental tube can do 45 images at 45 seconds, that is, a bit faster.  A CEI dental tube operating at 90 kVp can do 3mA continuously for 45 seconds, so each exposure (image) will be 3 mAs at 90 kVp.  The Nanox.Cart demo at RSNA 2020 image needed just 1.5 mAs at 40 kVp (so, significantly less than 1/4 of what the CEI dental tube can supply).  Commercial fluoroscopy equipment does ok with 100 kVp and 1 mAs for each frame (image) at 30 fps.  So, sure, with a good enough (expensive enough) detector, you can do the Nanox.Arc tomosynthesis within 45 seconds.  But the detector (regardless of the tubes used) won't cost anywhere near $10,000.  And no one would like to look at the images (the American College of Radiology never considers a tomosynthesis procedure to be "usually appropriate,"  except for breast, which the Arc cannot do).

Summary notes

The Summary of the 510(k) submission by Nanox for its Nanox.Cart device was published last week.  Here are some observations, in no particular order of importance (yet).

The name of the predicate device is wrong

The name of the predicate device, cleared under K021016, is AMX-4 Plus Mobile X-Ray System, not AMX-4 Mobile X-Ray System as claimed by the Summary.  What else is incorrect, if Nanox cannot even get the name of the predicate device right?  The "Plus" system is the upgraded model.  The predicate of the Plus model is AMX-3 Mobile X-ray System, K802047, another GE system.  The chair of Nanox Advisory Board is a former GE executive.

A micro-controller Arduino Mega 256 does not exist

Table 1 claims that Nanox.Cart uses a micro-controller Arduino Mega 256 that "controls the Nanox Cart X-ray System's functionality and GUI display."   No such micro-controller exists.  There is an Arduino Mega 2560 micro-controller board designed for hobbyists that uses the old and cheap ATmega2560 micro-controller released more than 15 years ago.  Quite novel.

The target angle of 0 degrees in Table 1 is non-sensical (a typo) and contradicts the 16 degrees value in Table 2

The target, or anode, angle is a very important characteristic of an x-ray tube, as it determines focal size and beam width, strength and composition.  At zero degrees, the tube will be completely unusable.  It is one mistake that Nanox should not have made, if its "X-ray source technology [were] the basis of [its] business" (page 9, annual report).

The maximum tube voltage for the predicate device in Table 1 is incorrect

Table 1 claims that the maximum tube voltage for the predicate device is 100 kV, which clearly contradicts the 125 kV value from the "kV range" section in the same table.  The actual value is 130 kV (from the tech specs of the HRT09 tube).

The power output of the reference device is annoying

Table 2 states that the power output of the reference device is 4.8 kW @ 104 msec, which is incorrect (a typo) and it should be "@100 msec," which is the standard (for example, IEC 60613:2010). 

The x-ray source used by Nanox.Cart is still a mystery

There is no mention in the summary of any of the non-sensical descriptions that Nanox typically uses for its proposed x-ray source - digital, MEMs, silicon, semi-conductor, novel, etc.   Table 2 claims that the "Nanox Tube" is similar to "Xinray CNT Tube," but that is incorrect based on the data in Table 2, as the CNT tube is 60x as powerful (4.8kW vs 0.08kW), capable of substantially higher tube voltage (110kVp vs 40kVp) and current.  Table 1 mentions that Nanox.Cart uses a "Nano-x's Cold Cathode tube" in the system description, but the tube type/model in both Table 1 and 2 is given as "Nanox Tube" (no cold-cathode here) and there is no tube model (Nanox' web site shows at least 4 completely different and incompatible "Nanox tubes" that look remarkably similar to regular industrial/dental hot-cathode tubes).

The mention of an x-ray source in the intended use is non-sensical

The description of the device's intended use begins with the non-sensical statement

The product is intended as an X-Ray source for diagnosis. 

The product is a mobile x-ray system - FDA product code IZL - not a x-ray source (which almost exclusively means an x-ray tube in the context of modern diagnostic equipment - other sources could be radioactive isotopes, synchrotrons, etc).  The product is supposed to include many more components other than an x-ray tube, as confirmed by the "system components" section in  Table 1, for example,  It appears this statement was intentionally inserted by Nanox to confuse investors and possibly subvert the 510(k) clearance process.

The single-source Nanox device is cleared only for hands, wrists, and fingers, on adult patients only

Both Table 1 and Table 2 claim that the intended use of the device is similar to that of the predicate and reference devices.  But that is incorrect and contradicts the actual description of the intended use, as the device is cleared for a very limited subset of examinations, while both the predicate and reference devices can do all general purpose X-ray diagnostic procedures.  In fact, the limitation for use explicitly states:

This device is not intended for general radiographic X-Ray examinations other than the indicated use...

So much for Nanox curing cancer.

The Nanox device is cleared to work with only one detector model, which appears unsuitable and has to be purchased separately

There is a bit of problem with the tech specs of the detector that Nanox has chosen to work with its device.  The summary states:

The Nanox Cart is specified and designed to operate only with a Flat Panel Digital X-ray Detector Model EVS3643, manufactured by DRTECH Inc.

The summary of the detector clearance specifies that the X-ray system using it must have tube voltage equal or higher to 40 kVp, so Nanox.Cart barely complies (its tube voltage is fixed at 40 kVp per Table 1 and 2). What is more troubling is that the generator "mA Range" used in the detector clearance is specified as "10mA ~ 1000mA," which Nanox Cart fails to meet, as it cannot deliver more than 2mA (implied by 0.08 kW power output and 40 kVp tube voltage).  

More importantly, this detector cannot be used for diagnostic purposes on a live subject by the proposed multi-source Nanox.Arc device, as it is too slow and takes about 5 seconds to capture and transfer an image.  A 45-image tomosynthesis of a wrist, for example, would take at least 4 minutes, if the RSNA 2020 demo were anywhere close to reality.

Finally, the lowest quote for this detector, obtained in the gray market - new, but from unauthorized distributors and without warranty - is about $20,000.  So much for being "cheap."

Many of the images supposedly made with the single-source device in the annual report and in investor presentations are likely fake

According to the annual report, 

[Nanox has] generated the images below with the Nanox.ARC using a single X-ray tube on an imaging phantom (page 61).

 

However, none of these images were generated by the device that received clearance, as the device tube voltage is limited to 40 kVp (so the 50 kVp tube voltage in the images is impossible).  Moreover, the device is not cleared for ankle/foot examinations.

Here is another image, from Nanox investor presentations, that is impossible to create by the device that got cleared.  

First, the device is not cleared for shoulder examinations.  Second, the 2.5mA reading exceeds the maximum device tube current of 2mA.

The mobility of the device is questionable

The device is cleared under the IZL product code, but it is not truly mobile/transportable.  The device description states:

The system facilitates X-ray examinations in situations where it is not possible or feasible to transport the patient to a ward with fixed equipment

But the device has no battery, unlike its predicate - it is as mobile as the length of the cord (less mobile than a regular vacuum cleaner). 

The device is "similar" to the predicate device, except that it is not

The section "Substantial Equivalence Discussion" is somewhat confusing.  The section argues that the device is equivalent except that it is not. 

The technical characteristics of the System are not different from the predicate device except for the fixed Source-to-image Distance, Field of view, aperture, focal spot size, and the fixed tube voltage and reduced maximum exposure current-time product. 

Virtually all technical characteristics of the two devices are significantly different, and, it can be argued, raise many questions of effectiveness.  Table 1, for example, confusingly states that the fixed tube voltage and current exposure time product (or charge) are similar to the significantly wider ranges that are needed in practice and can be obtained from the predicate device.  For example, typical "technique charts" for digital detectors stipulate tube voltages of least 46 kVp for the intended use (adult fingers/wrist/hands), above the 40 kVp limit of the device.

The device requires cooling fluid

This must be surprising to Nanox investors who are led to believe by the CEO that a cold-cathode tube, even if real, runs somehow cooler than a regular hot-cathode tube of the same power.

The intended use contradicts the disclosures in the SEC filings

Nanox implies in its SEC filings that the device will not be commercialized, and so the statement that the indented use is to perform diagnostic radiographic examinations is misleading.

Specifically,  Nanox states in its SEC filings:

the multiple-source Nanox.ARC [rather than this cleared Nanox.Cart device] ... will be our commercial imaging system (page 2, Prospectus). 

Nanox has further revealed that, while not intending commercial distribution of the cleared device, it is using the 510(k) submission as part of its regulatory strategy, a step in 

a multi-step approach to the regulatory clearance process (page 1, Prospectus), 

where the apparent ultimate goal is to induce the FDA to clear the "the multiple-source Nanox.ARC" device by first creating a predicate out of the Nanox.Cart.

Therefore, any statements by Nanox about "indications for use" or intended use or intent to market the cleared device, other than an admission that the device is not intended to be marketed and the submission is simply a step in Nanox regulatory strategy, are problematic.

Update:  Here is a cheap (dental) tube, Toshiba/Canon D-081B, that is used in other devices cleared under the IZL  product code, that is smaller but much more powerful and much more useful than the proposed "Nanox Tube."

Update:  Replaced "implied by 2mAs and 1 second" with "implied by 0.08kW power output and 40 kVp tube voltage" as it is the correct derivation for max tube current (sustained for 0.1s) - in this case, both derivations result in 2mA tube current.

Update:  Nanox predecessor claimed in 2016 that the chip that forms its cold cathode can do 2.5A/cm2 (Nanox CEO was a Chief Strategy Officer at the time).  If Nanox had made no improvements since, it means that the active area of its "chip" is now 0.0008 cm2 or a square of about 0.3 mm x 0.3mm.  So why do the chips shown in Nanox annual report (page 66) and in a March 2021 tweet look much larger, at least 10 mm x 10 mm?  Each covering an area that is at least 1000x the supposed area claimed in 2016 ...

 

Of course, as discussed elsewhere on this blog, Nanox has been unable to manufacture such a chip commercially (and so the proposed Nanox Tube is almost certainly not using any chip or any cold cathode), contrary to claims in its annual report (the University of Tokyo labs, which Nanox claims to rent, prohibit commercial use).

Update May 11, 2021:  Replaced the image of the wafer from the annual report with an image from a tweet that shows the chip next to a ruler.   

Update May 14,2021: Garage Blitz TV @Youtube makes a great point about the reference device using a CNT tube, which according to the Nanox annual report cannot work.  Moreover, the Nanox "founder" claimed in November 2019 that no such device exists, to the best of Nanox "knowledge."  

To the best of Nanox knowledge

Nanox (and predecessor) "first" press releases are quite amusing - Singapore detector in October 2013, digital 1x1x1 in June 2019, and the field of cones, November 2019.

So, Mr. Masuya, a lawyer and the founder and CEO of Nanox predecessor, says in November 2019:

to the best of our knowledge no company have achieved a commercially stable [cold cathode] source [based on carbon nano tubes] that can be embedded inside a medical imaging system and operate with an acceptable lifespan. 

The problem is that he must have known that Carestream and Micro-X had received clearance for and commercialized their Nano x-ray system with a cold-cathode source based on carbon nano tubes in February 2018.  That source was initially made by XinRay (a Siemens JV now defunct, but see NuRay), and now by Micro-X Ltd.  So much for Nanox "knowledge."  

Micro-X CNT source ( from https://www.aumanufacturing.com.au/micro-xs-carbon-nanotube-x-ray-machine-in-clinical-use )

And where is that Nanox source that can be embedded inside a medical imaging system and operate with an acceptable lifespan?  Or did he mean a cheap underpowered hot-cathode Chinese source not suitable for medical imaging? 

Note:  High current with a maximum emitter current of 130mA for up to 2 seconds per tech page.  Compare to Nanox 11mA "proposed" hand-made "hight [sic]" chart.