Doppler Ultrasound Uses Confusing Color Scheme

In my algebra-based General Physics courses, I get many Biology/Pre-med/Life Science majors, so of course many of the examples that I choose tend to be related to those areas. When we cover traveling waves and Doppler effect, I dive into medical diagnostics to show a few of the applications of Doppler effect in that area.

Interestingly enough, in Doppler Ultrasound, the color scheme that they use tend to be a bit confusing with what we use in physics. In the Doppler effect, when the source of a wave, or the source that is reflecting the wave, is moving away from the observer, the wavelength will be longer than the original wave. We popularly say that the wave has been "redshifted". This is because in the visible spectrum, the longest wavelength is toward the red color.

Conversely, if the object is moving toward the observer, then the wavelength will be shortened, and thus, "blueshifted", since blue (or violet) is the shortest wavelength in the visible spectrum.

But this is not the color scheme adopted in the field of Doppler Ultrasound, as represented in this video:

It seems that if the flow is toward the transducer, it is given the red color while if the flow is going away from the transducer, it is given a blue color.

Obviously, this is not a source of confusion for people in that field since they don't normally encounter those color-shifted lexicon, but for students who are studying this topic for the very first time, this takes a bit of an effort to make sure they do not become confused with the contradicting color scheme. The first time I used the Doppler ultrasound example was, unfortunately, right after I discussed an example from astronomy where I indicated that most of the light from the galaxies are redshifted and thus, a strong evidence that the universe is expanding since those galaxies are moving away from us. You can imagine that the students who were paying attention got a bit confused because the blood flowing away from the transducer is now being labeled with blue color instead of red.

Does anyone know why this field adopts this color scheme? 

Zz.

The Unseen Impact of Physics In Healthcare

This is a nice news article that provides a basic summary of the applications of physics in healthcare and medicine. It's another one of those where if someone thinks physics only deals with esoteric and useless ideas, show him/her this. I've mentioned many examples of similar medical/health/etc. applications and concepts that came directly from physics, such as this one.

As someone who often teaches general physics to life science/premed/bio/kinesiology major, this is definitely another useful evidence to get them to realize that the physics class they are taking has a direct relevance to their area of study.

Zz.

Solid State Sensors To Detect COVID Virus?

First of all, I'm not sure why this is called "Quantum sensor". Maybe it is because it is using solid-state physics principles?

This is an interesting report, and if the simulation is valid, I'm hoping that such devices will be made real soon because it has the ability to detect other types of viruses. It really is a solid state sensor that makes use of solid state physics principles.

In the presence of viral RNA, these pairs will detach from the nanodiamond surface thanks to a process called c-DNA and virus RNA hybridization. The newly formed c-DNA-Gd³⁺/RNA compound will then freely diffuse in solution, thereby increasing the distance between the magnetic Gd and the nanodiamond. As a result of this increased distance, the NV centres will sense less magnetic “noise” and thus have a longer T₁ time, which manifests itself in a larger fluorescence intensity.

By optically monitoring the change in relaxation time using a laser-based sensor, the researchers say they could identify the presence of viral RNA in a sample and even quantify the number of RNA molecules. Indeed, according to their simulations, Cappellaro, Kohandel and colleagues, who report their work in Nano Letters, say that their technique could detect as few as a few hundred strands of viral RNA and boast an FNR of less than 1%, which is much lower than RT-PCR even without the RNA amplification step. The device could also be scaled up so that it could measure many samples at once and could detect RNA viruses other than SARS-CoV-2, they add.

I find this interesting because as students in solid-state physics, one of the first thing that the students encounter in such a course is the study of solid-state crystal lattice. This includes the type of defects in a crystal lattice, such as vacancies and impurities. So this diamond NV center is exactly those two types of defect in the lattice. Imagine that something you learned during the first couple of weeks of a course in school actually has a humongous application to human well-being!

Chalk this one up as another invaluable application from condensed matter physics.

Zz.

Tripple-Layer Mask Blocks Secondary Atomization of Cough Droplets

I had already posted several physics papers on the efficacy of masks, even single-layer ones, in reducing the airborne aerosol. Now comes another paper that deals with how cough droplets actually can break up into smaller-sized droplets that may pass through single and double-layered masks, especially when moving at such high speed from a cough.

It turns out that having a mask with 3 layers or more might be the most effective here (I wonder at how many layers will we will of suffocation? :)) The new research is to be published in Science, and you can get the paper at the link to read to your heart's content.

A review of this paper can be found here. It is fascinating to read that expertise in the study of jet engines are being leveraged in studying the dynamics of this problem. But do you think people who don't believe in wearing masks to reduce the virus transmission will buy any of this? They believe in smartphones and jet engines, don't they?

Z.

Followup On Far-UVC Light Kills Airborne Coronavirus

This is a follow-up on the topic that I posted last time regarding evidence that far-UVC light can effectively reduce airborne virus transmission.

I read more about it, and found this extensive Physics World article that highlights the current development of the application of far-UVC light in virus sterilization. So obviously, this is a very active area of research right now. There are compelling evidence that far-UVC may be safe to human beings under limited exposure while still be effective in eliminating airborne viruses such as COVID-19.

But another issue that I've been trying to dig through is that, while far-UVC may be safer in terms of very short penetration depth into the skin and cornea, I haven't read much on possible ozone generation. One of the nasty effects of UVC light is that it can create ozone gas.

I sent to the International Ultraviolet Association webpage (didn't know one existed till recently), and went through their FAQs. One of them addresses the specific issue of ozone creation:

Does far UV (200 – 225 nm) generate ozone?

From a photochemical perspective, yes.

The Chapman cycle (Chapman, 1930) describes the counteractive processes of ozone formation and degradation from the interaction of light with molecular oxygen (O2) and ozone(O3). The rate of generation of ozone by far UV-C (known as the Herzberg continuum in atmospheric science) outweighs the rate of its degradation; the tipping point at which this generation/degradation balance flips is ~242 – 243 nm. (Andrew et al., 2003; Santos, Burini, and Wang, 2012), Far UVC (200-225 nm) only generates ozone in the upper atmosphere, where path lengths are very long. In a normal laboratory setting, ozone would not be generated because oxygen (O2) is a very weak absorber in the far UVC region.

As with any process, the risk of such hazards should be assessed on an application-by-application basis. A low power lamp operated in a well-ventilated area may not generate a measurable ozone concentration; a high-power system in an enclosed space may constitute a substantial risk.

Now, I don't quite understand why the "path lengths" have anything to do with ozone generation in the upper atmosphere, but it seems to imply that in a lab setting, far-UVC is not an effective ozone producer because it is a weakly absorbed by oxygen molecules. I can't get access to those articles while I'm at home, and I'm not even sure if my institution subscribes to any of those sources. So if anyone has more info on this, let's hear it.

This will be a tremendous way to reduce airborne transmission if it can be show to be effective and safe. But as with many things, it needs to be investigated carefully.

Zz.

Far-UVC Light Kills Airborne Viruses, And Safe To Humans Too?

First, let me give you the link to the paper that was published in Nature recently.

I actually have 3 separate topics to discuss here all based on this single paper.

The first is the science. UVC is used to kill viruses and sterilized stuff. We know that already. But it is also unsafe to human and we do not want to be exposed to it. But it turns out that far-UVC, having wavelengths in the range of 207-222 nm, is not totally harmful to human. In fact, ...

a regulatory limit as to the amount of 222 nm light to which the public can be exposed, which is 23 mJ/cm^2 per 8-hour exposure

means that humans can be exposed to this range of UVC for a limited amount of time. This is the basis of that research, i.e. using that wavelength and intensity of far-UVC, and see whether it can greatly "inactivate" the amount of viruses carried in airborne aerosols. They found that an exposure of just 25 minutes, very much below the regulatory limit. So there is a way to kill off viruses in airborne aerosols in the same space that human beings are around!

Certainly the implication of this research can be quite important, considering that airborne transmission of the COVID-19 virus is a strong possibility, which is why we are all wearing masks in public. There is now a way to greatly reduce such mode of transmission if this research is verified. The only thing I'm a bit weary about is the health and safety aspect. I know that they cited several sources that seems to show that the far-UVC is harmless to human, and the regulatory limits that have been imposed. Still, I'd like to have this one to be more well-established before I get really excited about it. For example, although the exposure limit is given in per 8-hour doses, how often can someone be exposed to that limit, say, in a month? Is that 8-hour dose limit per day? And certainly, long-term effect needs to be considered in anything of this sort.

But still, I find this result to be very promising, and it certainly is a new piece of information to me that far-UVC is actually not that harmful to humans.

The second aspect of this paper that I want to highlight is to the general public who often do not quite understand the nature of scientific publication. The main reason for scientists to properly publish their work is so that the rest of the community, especially those experts within the same field of study as the work, can scrutinize the work and evaluate its validity. So having something published does not automatically makes it valid. This is important to remember and understand. It requires scrutiny and verification by other experts in the field, and can sometime takes years. Think of how long of a time period from the moment the Higgs mechanism was proposed till its experimental verification at the LHC.

Therefore, it is imperative that a paper contains all the relevant information used to arrive at its conclusion or result. In this case, it is an experimental paper that produces a result. For it to be evaluated by other experts, it must contain all the necessary information. If you look closely at the end, the authors included their methodology, the exact equipment that they used, the experimental setup, the nature of the data analysis used, etc... etc. In other words, everything is as transparent as possible. It allows for someone else to repeat the experiment, and that is a crucial aspect of experimental science - REPRODUCIBILITY. It is something pseudoscience cannot do!

The third and final aspect of this paper is educational. I'm excited at the various values that they used in this paper, because I can already see myself using them in my general physics lessons. I'm already planning on using many of these numbers and asking my students to calculate (i) the amount of power per unit area based on the exposure time, (ii) the energy per photon of 222 nm light, (iii) the number of photons that impinges on a unit area during the exposure time, etc... etc. This will be perfect especially for the general physics course that I have taught that is aimed at life-science/pre-med majors. I always like taking something current, and very relevant to our times, to use as a material in our lessons. The students can immediately see first-hand that what they are learning is, in fact, very useful and has a direct effect on them beyond just wanting a good grade at the end of the semester.

So yes, I'll be holding on to this paper for quite some time.

Zz.

State of the Art of MRI

This is a very good article from Physics Today on the history and development of Magnetic Resonance Imaging, which has become ubiquitous in medical diagnostics. Of course, this came out of the discovery of the nuclear magnetic resonance phenomenon, a technique that itself came out of our understanding of quantum mechanics.

When you read this article, pay attention to how it is continuing to be developed, to evolve, and its continuing improvement. Medical physicists are still actively improving this, and other aspect of the medical field by incorporating things that physicists already know and use. Without advancement in physics, both theoretically and experimentally, there is nothing to trickle down from to the medical field.

Zz.

First Human Scanned By Spectral X-Ray Scanner

Chalk this up to an application of high-energy physics in the medical diagnostic field. The first human has been scanned by a new type of x-ray scanner (registration required to read article at this moment).

The MARS scanner uses Medipix3 technology developed at CERN to produce multi-energy images with high spatial resolution and low noise. Medipix is a family of read-out chips originally developed for the Large Hadron Collider and modified for medical applications.

The Medipix3 detector measures the energy of each X-ray photon as it is detected. This spectral information is used to produce 3D images that show the individual constituents of the imaged tissue, providing significantly improved diagnostic information.

I'll repeat this, maybe to those not in the choir, that many of the esoteric experiments that you think have no relevance to your everyday lives, may turn out to be the ones that might save your lives, or the lives of your loved ones, down the road. So think about this when you talk to your elected political representatives when it comes to funding basic science.

Zz.

Therapeutic Particles

No, this is not some mumbo-jumbo New Age stuff.

While this technique has become more common, and there are already several places here in the US that are researching this, this is a nice article to introduce to you the current state-of-the-art in using charged particles in medicine, especially in treating and attacking cancer. It appears that the use of carbon ions is definitely catching up in popularity over the current use of protons.

When you read this article, pay attention to the fact that this is an outcome of our understanding of particle accelerators, that this is a particle accelerator applications, and that high-energy physics experimental facilities are often the ones that either initiated the project, or are hosting it. So next time someone asks you the practical applications of particle accelerators or particle physics, point to this.

Zz.

How Does Proton Radiation Therapy Work?

Here's a video from Don Lincoln on a physicist's view of proton radiation therapy in attacking a tumor.



If you want a more detailed and technical information on proton therapy, you may access a more in-depth paper here. This, btw, is another example of the application of accelerator physics and elementary particle physics, in case you didn't know.

Zz.

The Physics of Proton Therapy

If you have read the news, you would have heard of the issues surrounding the parents of a sick child desperately seeking to have their son undergo a proton therapy.

Jon Butterworth has a nice article for the general public on the physics of proton therapy, and especially why it is different than other forms. When you are reading this, please note that this medical treatment came DIRECTLY out of our knowledge of experimental high energy physics, y'know, the physics that many people could not see the use of. So next time when someone questions the applications and benefits of funding this area, you point to him/her this article!

Zz.

Role of Physics in Medicine

This is a good article that reviews Lancet's special issue on Physics and Medicine.

While many of us, and especially those who are in this field, are aware of this, the article is more useful when it is preached to those who are not in the choir. The general public, and especially the politicians that determine fundings, need to be told of this FACT. While the knowledge that is gained out of apparently "useless" subject area such as high energy physics, elementary particle physics, astrophysics, etc. are themselves interesting and important, the EXPERIMENTAL techniques and the technology that are pushed to do these studies are paving the way for applications in other areas, including medicine. Your x-rays, MRI, proton therapy, PET-scans, etc., all came out of the advances made to perform these high energy physics/astrophysics/etc. experiments!

High energy physics, especially, continues to push detector technology. Unlike many areas of physics where experimentalists buy equipment off the shelf, and therefore their ability to do many of these experiments depends on what is commercially available, high energy physicists/astrophysicists often have to BUILD and DEVELOP their own detectors. The area of detector physics deals with a lot of applications that are targeted at detecting single-photon pulses of Cerenkov light from, say, a neutrino interacting with a tank of water, or a calorimeter for particle physics collider, etc. Many of the knowledge gained in producing these detectors will eventually make it into other areas, including medicine.

What this means is that, reduced funding in areas which you think has no effect on you is simply going to affect the future of your well-being, and the well-being of your children and grandchildren. It takes years for such knowledge to trickle down to useful applications, and one is simply ruining the seeds that one should be planting now.

Zz.

No Link Yet Between Cellphone Use And Brain Tumor

Another new studies that could not find any link between prolonged cell phone usage and brain tumors.

Y'know, people can make many speculative arguments back and forth on the issue of cell phone use and brain cancer. The FACT that we have right now are:

1. no established and clear link between cell phone and cancer, and
2. no physical mechanism for cell phone signals to cause cancer.

These are what we have currently. While people certainly are free to exercise caution if they want to, one should not confuse personal preferences and speculation with hard, valid evidence.

I'm more worried about drivers who use their cellphones while driving than I am about the cellphones causing cancers. If people are SO worried about their safety, why aren't they up-in-arms about that? There are enough documented evidence of accidents (including fatal accidents) that were direct results of using cell phones while driving. Instead, we get MORE publicity out of something that hasn't even been well-established, AND people who seem to already believe in them.

Makes no sense....

Zz.

Traveling at Warp Speed Would Kill You

... but not due to what you might think!

William Edelstein, a professor at Johns Hopkins University’s School of Medicine, has thought of another scenario on why those people on the Starship Enterprise would not have survived traveling through space at close to the speed of light. And it has nothing to do with the contortions of warped spacetime either. It is more basic and more well-known that that.

“I put in the Star Trek thing cause it would be dramatic,” he explains. The point of the paper was to really look at the impact of radiation at high speeds, he said. When you travel at high speeds in space “you are basically plowing through hydrogen,” he explained. “What actually happens as soon as they encounter the ship, the atoms split into protons and electrons and the protons mainly go through you and do damage.”

Edelstein said in an interview with the Star that the problem is when travelling in space at close to light speed hydrogen turns into “intense radiation” that kills humans and destroys electronic instrumentation. Even a ship’s hull of 10 centimetres in thickness would do nothing in terms of preventing damage.

In his presentation he said that a fatal dose of radiation for humans is six sieverts. And with his calculations a crew would receive a dose of more than 10,000 sieverts within a second.

So forget about the stuff that we barely know of. Just simple rudimentary high energy collisions that we already know of, and its radiation effects, which we also know of quite well, can already kill you.

Tough luck, space travelers!

Zz.

Magnetometers for Cardiac Diagnosis

It's a long way from the very "pedestrian" applications of magnetometers. It seems that it is sensitive and reliable enough that it has been proposed as a diagnostic for heart conditions.

The sensor head is made up of a series of coils that cancel out unwanted signals and amplifies the signals that are needed. So the tiny magnetic fields produced by a person's heart can be transmitted into the heavily shielded environment. What we've been able to do is combine existing technology from the areas of atomic physics and medical physics in a completely unique way.

Supposedly, this development came as a "by-product" of a research grant titled "Creating Long Chain Entanglement Using a Phase Sensitive Micromaser". This is another example of not judging a scientific work by its name. You just never know what direct benefits that you will get even when the subject matter being studied sound esoteric.

Zz.

The Medical Isotope Shortage

I've mentioned before on this issue regarding the Chalk River facility and also the possible alternative of using particle accelerator to produce such isotopes. This is a good comprehensive review of the shortage of medical isotope that will become critical soon if no new solution can be found.

Zz.

Canada's Nuclear Know-How in a State of Accelerated Decay?

This article presents the issues surrounding the aging Chalk River nuclear reactor facility in Canada.

With problems continuing to plague the aged Chalk River reactor, once the source of more than half the world's supply of the radioactive material vital for cancer and cardiac testing, the four-member panel has been charged with recommending a new source by Nov. 30.

It examines two important aspect of the story:

1. The fate of nuclear isotope source for the world since the facility produces close to 50% of the world supplies of isotopes for nuclear medicine

2. The possible decline of nuclear expertise in Canada if the facility shuts down with any similar replacement.

I've mentioned earlier about the alternative option of using a particle accelerator to generate the Mo99 isotopes. Certainly this is a viable, but untested, alternative.

The accelerator proposal put forth by TRIUMF, a subatomic physics lab at the University of British Columbia, uses an electron accelerator to fire a photon beam at uranium, producing moly-99. But it's an untested process creating an unfamiliar product and a whole lot of questions.

For instance, reactor-based tech-99 is "milked" from moly-99 using a device called a generator, or moly cow. But the accelerator-based moly-99 may differ from reactor-based moly-99 just enough that an entirely new model of cow would have to be manufactured, adding considerably to the startup costs.

Such option is also being considered in other parts of the world, including the US. We will see how this will turn out. I think we are still in the "proof-of-principle" stage of the development.

Zz.

Hybrid Linac-MRI System

This is rather fascinating.

A new medical device is being proposed that combines two existing technologies - MRI with medical linear accelerator.

A more robust way to guide radiotherapy would be to image the entire tumor continuously and adjust the radiation beams accordingly. Fallone and his colleagues are testing a prototype Linac-MR system they built to do just that.

Linacs (short for linear particle accelerators) are basically devices that use radio waves to accelerate electrons to high speeds and crash them into a solid metal target -- typically tungsten -- producing high-energy X-rays in the collision. These high-energy X-rays destroy cancerous cells by causing irreparable damage to the cells' DNA, MRIs, familiar because of their ubiquity in modern hospitals, are very good at imaging soft tissue and would be an ideal technology for combining with Linacs because most cancers occur in soft tissue.

The problem is making MRIs and Linacs work together. Normally, each one would interfere with the other. Linac systems emit radio waves, which interfere with MRI hardware -- so much so that most hospital MRIs are placed in shielded rooms that specifically block radio waves. At the same time, MRIs employ strong magnets that can interfere with Linac systems.

That's what I thought when I first read this. These are two systems that one seldom thought would be compatible with each other, since they both produces effects that the other doesn't want. I think this is more of a technical or engineering issue that needs to be carefully solved. Certainly, I don't see any showstopper that would stop the progress here. It would be an amazing and important development if one could image and perform the treatment simultaneously. In fact, if one could even detect where the x-ray is actually being deposited as the treatment is being done, that would be as important.

Zz.

How Astrophysics Could Save Heart Patients?

This news article highlights the common factor between the study of planetary formation and the flow of molten "metal" at the center of a planet with blood flow in human.

Still, I'm not sure if I'm being picky here, but it appears to be more about the connection between geology and saving heart patients, rather than astrophysics. I don't see any "astrophysics" in this article, at least not in the traditional sense. Did I miss something?

I would hate to think that geologists who are really doing such work are not having their profession being credited for this.

Zz.

How Physics Can Solve Crime And Help To Cure Cancer

While we know that physics works everywhere, how it works and how it is used are often lost by the public, especially when they really do not understand physics. So I often try to highlight these applications when they explicitly use physics principles to work. Hopefully, these provide one of the infinite examples where physics is clearly used, besides the often-overlooked applications that are already common and numerous in our everyday lives.

The physics that is used in forensics is described briefly in this article from the March issue of Physics Today. It is unfortunately that a clear example on where it is useful is in a tragic incident.

A young woman was found at the bottom of a cliff in Sydney, Australia, in June 1995. The site was a popular suicide spot, and the police assumed she had killed herself. But last November the woman's boyfriend was convicted of murder. “It took 10 years to figure out that the woman was thrown off the cliff; she did not jump,” says Rod Cross, a physicist at the University of Sydney who served as a consultant for the case. It took that long, he adds, “mainly because the police did not understand that physics could help solve the problem.”

The second example comes from the same issue of Physics Today, and in fact, is the very next article. It deals with the issue of making proton accelerators more compact (and thus, affordable) in the treatment of cancer. I decided to highlight this for two reasons:

1. It shows another application of accelerator physics which does not involved a high energy physics experiment, and

2. It shows that physicists and physics CAN, in fact, be used to "cure" cancer.

I'm mentioning this because of a blog entry that I made that was completely unrelated to this. I mentioned an amusing poster produced by the APS on how long one has to yell at a cup of coffee to heat it up. For some odd reason, it was picked up by fark.com, and the comment on the story was:

Scientists solve the biggest puzzle of our age: How long would you have to yell at a cup of coffee to heat it up? And why is there still no cure for cancer?

I also received a rather nasty and profanity-laced "comment" to the blog, which basically asked why us "MF's" are wasting out time and not using our brains to cure cancer (the comment was not approved and it is now gone into laa-laa land).

I'm sure the first was written in jest, but both of these comments reflects an ignorance of the usefulness of the back-of-the-envelope calculation shown in that "coffee" article, and how physicists often determine something at the very beginning before plunging into something. It is an example or illustration on how we translate physical concepts and ballpark figures to determine some "boundary conditions" to how something can occur. It has nothing to do with the coffee, it has EVERYTHING to do with the skill involved. This still transcends that stupid coffee and can be used in almost any kind of situation. I could easily come up with several different example: (i) if we need to build a solar collector to produce 20 MW of energy over the duration of x hours, how big does it have to be?; (ii) if we have a cancer cell that needs to be irradiated by a proton beam over an area that is this big, how energetic should the protons be? etc... etc...

These are the type of quick calculation that one start with to lay down the foundation of possibility or realistic scenario for the detailed calculation later on that takes into account more factors involved. But that initial calculation is crucial to narrow down or at least provide some idea on where in phase space the problem is, and what kind of daunting scenario we are faced with.

And yes, that SAME skill is involved in providing the physics to those in the medical profession the TOOLS needed to fight cancer, both in terms of treatment, diagnostic (where do you think MRI, CAT scans, PET scans, etc. came from?), and advanced analysis. These professionals are the ones you need to hark at to find the cure for cancer. Yelling at physicists to do that is similar to asking medical doctors to find the origin of high-Tc superconductors. They may help in maintaining the well-being of the people who are finding the answers to high-Tc superconductors, but they are not really experts in the field and not directly working in it.

Capice??!!

Zz.