Biomedical optics play crucial roles across medicine

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Hello, and welcome to the Physics World weekly

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podcast.

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This episode features the medical physicist,

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inventor,

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and entrepreneur,

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Brian Pogue, who is in conversation

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with Physics World's Tammy Freeman.

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They explore some of the crucial roles that

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optical technologies

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play in medicine.

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But first, a message from One Physics,

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Here is that conversation with Brian Pogue.

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It was recorded in association

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with the journal

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Physics in Medicine and Biology,

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which celebrates its seventieth

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anniversary

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this year.

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Optical technologies underlie many of today's routine medical

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procedures,

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from microscopic imaging of cells and tissues to

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clinical applications

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such as endoscopy,

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ophthalmology,

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blood oxygen monitoring, fluorescence guided surgery, and and

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many more.

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And the field of optics is also converging

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with the world of medical physics,

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enabling exciting new techniques for guidance, dosimetry, and

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in vivo verification

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of radio

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radiation therapy cancer treatments.

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I'm speaking today with Brian Pogue,

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professor of biomedical engineering at Dartmouth College and

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cofounder of several startups developing optics based systems

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for medicine.

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Welcome to the podcast, Brian.

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Well, thank you. It's a pleasure to be

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here.

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So can you tell us a little about

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your background? How did your interest in optics

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and medicine

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first begin?

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Sure. Yeah. Well, you know, I was trained

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as a physicist, and I wound up doing

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a master's in laser

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isotope separation. So I've learned a lot about

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lasers and optics,

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but then specifically pivoted into a PhD in

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medical physics. And so that's where I sort

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of blended my two

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interests in optics as well as medicine,

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which is, you know, at the time was

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a little bit of an unusual mix, but

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this

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advisers I had were experts in the field,

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and it was incredible opportunity. So I really,

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have enjoyed it and continued,

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through my postdoctoral

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training

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and today to to work at both medical

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physics and biomedical optics at the same time.

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Excellent. So, could you maybe give us a

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brief introduction to some of the more general

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applications of optics in medicine?

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Sure. Yeah. I mean, I you know, I

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routinely

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remind my

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radiology and radiation oncology and other folks in

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who work in medical physics that optics is

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actually an enormous field. It's much, much larger

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than the field of radiation and medicine.

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You know, if you think about surgical

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intervention, pretty much all tools

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use optics. If you if you even think

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about a family physician, pretty much

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most of the tools they use are optics

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based, either just looking in your ear, in

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your throat, in your eye,

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looking in,

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cat body cavities,

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or

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blood spectroscopy,

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pulse oximetry,

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and, pretty much all vision technology

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to work in the to image the back

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of the eye, the retina, the cornea.

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These are all optical tools.

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Laser surgery, an enormous field.

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Most people don't realize, but dermatologists

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are probably the biggest user of lasers

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in the world because they have a vast

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array of laser systems to to treat skin

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conditions.

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So it's just

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through to all of medicine, really, optics has

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a I I routinely say I I'm pretty

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sure this is true that it's the largest

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single technology sector

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in medicine today is biomedical optics.

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Yeah. Yeah. I guess people sort of like

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you say, it's not immediately obvious,

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but actually, yes, it's it's used in all

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sorts of things. So, I mean, what main

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advantages of using light for clinical applications such

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as diagnostic tests?

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Yeah. So the the, you know, the main

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applications are, hey. It's not dangerous.

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And so,

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it's

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used in, what I call point of care

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technologies where the physician and the patient are

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in the same room together. That's point of

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care, and they're doing some procedure.

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More often than not, that's an optical device,

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either taking a measurement or doing a treatment

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with a laser or an optical system.

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So point of care is one area. The

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other one is molecular diagnostics.

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You know, most

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molecular diagnostics

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use optical wavelengths

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to do spectroscopy

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to take those measurements, either Raman or,

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scatter or,

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fluorescence

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diagnostics.

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So molecular features,

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point of care technology,

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and just the,

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usability too. The fiber op the fact that

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you can use fiber optics for delivery

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or recovery,

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means that you can do endoscopy or minimally

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invasive procedures.

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And so, again,

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you know, has transformed medicine. Let's face it.

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It's transformed medicine completely

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by its ability to get information in or

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out of the body through fiber optics.

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Okay. And then

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looking

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specifically now at optics within medical physics, particularly

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radiation therapy,

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what are some of the uses of lights

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in this field?

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Yeah. So, again, I think it's,

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not widely appreciated, but

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most detector systems

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in their core,

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they're either the detected signal is electrical

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or optical

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or both.

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But, you know, specs and PET systems all

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use scintillation,

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to turn x, gamma ray into an optical

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signal. And so there's optical detectors at the

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back end of most nuclear medicine devices,

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often previously photomultiplier

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tubes, but now more and more solid state,

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silicon

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devices.

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Radiation detectors in general,

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Again, the once the radiation is

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converted to something, it's usually an electrical or

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an optical signal.

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And so,

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a lot of,

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personal radiation monitors like film badges,

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thermoluminescent

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detectors,

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optical sent

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to, optical,

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OSLDs

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are are,

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optical in their nature.

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So, you know, optics has a major role.

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And then even just very simple things like

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positioning of patients in the room. You know,

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we use

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laser lines

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to align patients,

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to millimeter level precision when they sit on

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a CT scanner or an MRI or a

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radiation therapy device. So,

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optical systems are used for patient alignment.

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And then more and more,

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we are using optical systems for alignment where

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there's some kind of a surface scanning technology

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where the body entire body is,

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scanned

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with, stereo vision or with, speckle patterns

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to,

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verify the position of the patient in the

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treatment device or the imaging device.

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Okay.

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And,

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is it used within

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dosimetry

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in radiotherapy?

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Yeah. So so in dosimetry,

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again,

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scintillators

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are probably the most one of the most

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ubiquitous.

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Ionization chambers are most commonly used as reference

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dosimeters,

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but to do basic

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measurements that are undistorted

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by,

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radiation fields or magnetic fields, scintillators are very

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commonly used.

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Film

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is also commonly used in a lot of

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the probably one of the oldest optical detectors

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that exists. Is film

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still, routinely used for surface dosimetry,

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and then it gets read out.

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The types of film we use today are

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different than the old types that needed development,

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but it's still an optical readout

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of,

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radiation dose.

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And then, you know, in the last couple

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of decades, people have developed these gel dosimeters

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that are three-dimensional. It's sort of like a

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three-dimensional film

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that,

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is exposed to radiation and then turns color

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or turn either absorption or fluorescence,

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and that can be read out optically to

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get a three-dimensional

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image

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of radiation delivery.

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So, you know, all the way from point

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detectors

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to surface dose to three-dimensional

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dose,

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optical devices are used throughout radiation therapy.

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And

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then

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one really interesting development is, harnessing Cherenkov light

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to image radiation.

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So, first of all, can you just explain

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what Cherenkov light is?

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Sure. Yeah. So Cherenkov light is,

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this,

288
00:11:04,910 --> 00:11:06,529
a funny little light signal

289
00:11:06,954 --> 00:11:10,254
that comes off when ionizing radiation is incident

290
00:11:10,315 --> 00:11:11,294
in any material.

291
00:11:12,315 --> 00:11:13,034
And we

292
00:11:13,595 --> 00:11:15,294
almost everybody routinely

293
00:11:15,674 --> 00:11:16,654
thinks of

294
00:11:17,115 --> 00:11:18,954
when you think of radiation, you think of

295
00:11:18,954 --> 00:11:21,674
a blue glow. And in fact, that blue

296
00:11:21,674 --> 00:11:22,174
glow

297
00:11:22,779 --> 00:11:25,980
is Cerenkov light. So we implicitly most of

298
00:11:25,980 --> 00:11:26,480
us

299
00:11:27,019 --> 00:11:28,000
know of radiation

300
00:11:28,700 --> 00:11:30,160
in Cerenkov light already,

301
00:11:31,419 --> 00:11:33,820
and it's because we've seen pictures of used

302
00:11:33,820 --> 00:11:36,460
nuclear fuel bundles in water where there's a

303
00:11:36,460 --> 00:11:37,519
blue glow happening,

304
00:11:38,164 --> 00:11:41,464
or, there's pictures in the public media about

305
00:11:41,764 --> 00:11:42,485
radiation and,

306
00:11:43,924 --> 00:11:45,524
you know, this blue glow is sort of

307
00:11:45,524 --> 00:11:46,824
used to illustrate

308
00:11:47,125 --> 00:11:49,524
the presence of radiation. But in fact, it's

309
00:11:49,524 --> 00:11:50,024
real.

310
00:11:50,404 --> 00:11:52,350
It's it comes from soft

311
00:11:52,809 --> 00:11:56,029
collisions of high energy electrons with matter, and,

312
00:11:57,209 --> 00:11:58,269
the electromagnetic

313
00:11:58,809 --> 00:12:01,529
torque, if you will, of the medium emits

314
00:12:01,529 --> 00:12:03,629
this blue light as the electrons,

315
00:12:05,455 --> 00:12:08,434
collide. And and so it's a direct measurement

316
00:12:08,495 --> 00:12:09,315
of radiation

317
00:12:09,855 --> 00:12:11,634
dose in any material.

318
00:12:13,215 --> 00:12:16,894
Okay. So when this happens within tissue in

319
00:12:16,894 --> 00:12:18,815
a in a body, how can this light

320
00:12:18,815 --> 00:12:20,360
be used in radiotherapy

321
00:12:20,899 --> 00:12:21,379
for,

322
00:12:21,940 --> 00:12:22,919
measuring dose?

323
00:12:23,940 --> 00:12:27,059
Yeah. So, you it's possible to image. It's

324
00:12:27,059 --> 00:12:28,820
very low. You know, if you if you

325
00:12:28,820 --> 00:12:30,759
were actually standing in the room,

326
00:12:31,460 --> 00:12:33,539
you wouldn't be able to see Crenkov light

327
00:12:33,539 --> 00:12:35,595
unless you turned the room lights off. And

328
00:12:35,595 --> 00:12:38,034
it was pitch black and the radiation beam

329
00:12:38,034 --> 00:12:40,434
is hitting the patient. You actually could see

330
00:12:40,434 --> 00:12:42,514
the blue glow. You could see Cerenkov light

331
00:12:42,514 --> 00:12:45,654
coming off them. Patients for years have,

332
00:12:46,674 --> 00:12:48,514
commented on the fact that when their eyes

333
00:12:48,514 --> 00:12:50,970
are closed and there's radiation to their head,

334
00:12:51,049 --> 00:12:53,289
that they can see blue light in their

335
00:12:53,289 --> 00:12:56,269
eye, and that's a Cherenkov light, we believe.

336
00:12:57,209 --> 00:12:58,589
And so it is

337
00:12:59,129 --> 00:13:01,929
possible to image it. It's but it's very,

338
00:13:01,929 --> 00:13:04,329
very low. And so to do it,

339
00:13:04,730 --> 00:13:05,654
so we developed

340
00:13:06,055 --> 00:13:07,514
systems back in the,

341
00:13:08,134 --> 00:13:09,754
2012, 2014

342
00:13:10,055 --> 00:13:10,795
time frame

343
00:13:11,175 --> 00:13:13,195
to image this, and they have to be,

344
00:13:13,894 --> 00:13:15,355
especially time gated

345
00:13:15,735 --> 00:13:18,535
to linear accelerator pulses. And so that is

346
00:13:18,535 --> 00:13:19,195
the unique

347
00:13:19,870 --> 00:13:22,429
aspects that allows it to be detectable as

348
00:13:22,429 --> 00:13:24,610
you have to time gate your acquisition

349
00:13:25,230 --> 00:13:27,409
to the, delivery of the radiation.

350
00:13:27,949 --> 00:13:30,269
But it's it it comes off of everything

351
00:13:30,269 --> 00:13:31,169
that gets irradiated

352
00:13:31,485 --> 00:13:32,464
at some level.

353
00:13:32,924 --> 00:13:35,184
It's just a really small light

354
00:13:35,565 --> 00:13:37,325
signal. And and can you use, like, the

355
00:13:37,325 --> 00:13:39,245
sort of the level of this signal to

356
00:13:39,245 --> 00:13:41,964
indicate the dose that's been delivered? Is is

357
00:13:41,964 --> 00:13:43,259
one proportional to the other?

358
00:13:44,139 --> 00:13:46,399
That's right. So the the emission of Cherenkov

359
00:13:46,460 --> 00:13:47,919
light is directly proportional

360
00:13:48,540 --> 00:13:49,360
to the dose.

361
00:13:50,620 --> 00:13:52,620
It could you know, the signal can be

362
00:13:52,620 --> 00:13:55,179
distorted by the object that it's coming out

363
00:13:55,179 --> 00:13:58,444
from, but the production of Cherenkov is directly

364
00:13:58,444 --> 00:14:00,704
proportional to the radiation dose. So

365
00:14:01,084 --> 00:14:02,704
if you collect it properly,

366
00:14:03,164 --> 00:14:05,884
it can be a direct indicator of dose

367
00:14:05,884 --> 00:14:06,384
delivery.

368
00:14:07,245 --> 00:14:07,745
Okay.

369
00:14:08,620 --> 00:14:11,259
So, I mean, you are cofounder and president

370
00:14:11,259 --> 00:14:13,980
of a a Dartmouth spin off company called

371
00:14:13,980 --> 00:14:14,720
Dose Optics,

372
00:14:15,179 --> 00:14:18,320
which is commercializing this drink of imaging technology.

373
00:14:18,940 --> 00:14:20,959
So can you tell us about the company's

374
00:14:21,019 --> 00:14:22,095
BeamSight product?

375
00:14:23,134 --> 00:14:24,414
Sure. Yeah. So we,

376
00:14:24,894 --> 00:14:26,034
as I said, we

377
00:14:26,495 --> 00:14:29,154
developed the techniques of how to optimize

378
00:14:29,615 --> 00:14:31,634
collection of Cherenkov light and radiotherapy

379
00:14:32,414 --> 00:14:35,154
back in about 2012 to 2014,

380
00:14:35,454 --> 00:14:39,370
and we, developed patents around that as as

381
00:14:39,669 --> 00:14:42,250
every technology person should do,

382
00:14:43,190 --> 00:14:46,149
and then realized there was an opportunity there

383
00:14:46,149 --> 00:14:48,389
to spin off this as a as a

384
00:14:48,389 --> 00:14:51,769
unique dosimetry technology for radiation therapy.

385
00:14:52,184 --> 00:14:54,605
So this was really exciting for us because

386
00:14:55,225 --> 00:14:57,625
we had invented it in our lab and

387
00:14:57,625 --> 00:14:59,945
realized that there really should be a product

388
00:14:59,945 --> 00:15:00,445
here.

389
00:15:01,144 --> 00:15:02,044
And so

390
00:15:02,504 --> 00:15:03,725
myself with

391
00:15:04,105 --> 00:15:06,284
a a couple of other people from Dartmouth,

392
00:15:07,139 --> 00:15:10,259
spun out a company. And we were very

393
00:15:10,259 --> 00:15:12,339
lucky to get a pilot a series of

394
00:15:12,339 --> 00:15:13,860
pilot grants from the,

395
00:15:14,259 --> 00:15:16,360
NIH, National Institute of Health

396
00:15:16,820 --> 00:15:18,360
to kick off the company.

397
00:15:18,835 --> 00:15:19,554
And we,

398
00:15:19,955 --> 00:15:21,955
embarked for the next few years on sort

399
00:15:21,955 --> 00:15:24,514
of perfecting the product. And so we now

400
00:15:24,595 --> 00:15:26,054
it's gonna I'll call BeamSight,

401
00:15:26,514 --> 00:15:28,615
and it's really it's a camera system

402
00:15:29,315 --> 00:15:30,534
that's very sensitive,

403
00:15:31,379 --> 00:15:32,519
has a intensifier

404
00:15:32,899 --> 00:15:34,420
built into it to,

405
00:15:35,540 --> 00:15:37,480
both time gate the acquisition

406
00:15:37,940 --> 00:15:39,000
and amplify

407
00:15:39,379 --> 00:15:40,040
the intensity.

408
00:15:40,660 --> 00:15:43,940
Time gating is critical because the room is

409
00:15:43,940 --> 00:15:46,465
well lit, so we didn't. We knew we

410
00:15:46,465 --> 00:15:48,485
didn't wanna we couldn't ask

411
00:15:48,865 --> 00:15:51,105
the therapy people to turn the room lights

412
00:15:51,105 --> 00:15:53,605
off. So we have to capture this Trinkoff

413
00:15:53,745 --> 00:15:55,445
light signal that's really tiny

414
00:15:55,904 --> 00:15:59,825
in a massive ambient room background light.

415
00:16:00,649 --> 00:16:01,309
And so

416
00:16:01,769 --> 00:16:03,309
the key is time gating,

417
00:16:03,929 --> 00:16:06,509
and temporal sequencing of that,

418
00:16:06,970 --> 00:16:07,690
and then,

419
00:16:08,169 --> 00:16:11,289
pretty massive amount of image processing and signal

420
00:16:11,289 --> 00:16:13,710
processing on the back end. So these cameras,

421
00:16:14,250 --> 00:16:16,269
as most high end cameras are,

422
00:16:16,835 --> 00:16:19,095
they have a what's called a field programmable

423
00:16:19,394 --> 00:16:21,975
gate array. It's like a little programmable computer

424
00:16:22,355 --> 00:16:24,514
on board on the back end of the

425
00:16:24,514 --> 00:16:25,014
camera,

426
00:16:25,394 --> 00:16:27,634
and that does a a quite a bit

427
00:16:27,634 --> 00:16:28,774
of image processing,

428
00:16:29,939 --> 00:16:31,639
to make the image usable.

429
00:16:32,179 --> 00:16:32,919
And so,

430
00:16:33,459 --> 00:16:36,019
it's quite striking because the patients in the

431
00:16:36,019 --> 00:16:36,519
room,

432
00:16:37,220 --> 00:16:39,079
they're getting radiation therapy treatment.

433
00:16:39,620 --> 00:16:42,179
They are, I would say, unaware that there's

434
00:16:42,179 --> 00:16:44,595
this light signal coming off of them, but

435
00:16:44,595 --> 00:16:47,495
the camera picks it up, locks into it,

436
00:16:47,954 --> 00:16:48,454
rejects,

437
00:16:49,554 --> 00:16:51,794
you know, 99.99%

438
00:16:51,794 --> 00:16:53,334
of the background room light

439
00:16:53,634 --> 00:16:54,034
and,

440
00:16:54,595 --> 00:16:56,695
displays an image of that Cherenkov

441
00:16:57,910 --> 00:16:59,690
light coming off of their tissue.

442
00:17:00,310 --> 00:17:01,850
And and then this is used

443
00:17:02,230 --> 00:17:05,769
and displayed at the therapy console so the

444
00:17:05,990 --> 00:17:08,890
radiation therapy team can actually see what's happening.

445
00:17:09,029 --> 00:17:10,244
And it and it's,

446
00:17:11,045 --> 00:17:13,365
developed so it can image at 30 frames

447
00:17:13,365 --> 00:17:15,144
per second. So it's real time video,

448
00:17:16,484 --> 00:17:19,045
and and they can see the radiation treatment

449
00:17:19,045 --> 00:17:20,984
as it happens. And so,

450
00:17:21,525 --> 00:17:24,805
you know, most radiation treatments are just fine,

451
00:17:24,805 --> 00:17:26,109
perfect, you know,

452
00:17:26,570 --> 00:17:28,570
but that patients have to come in every

453
00:17:28,570 --> 00:17:31,049
single day for thirty days in a row

454
00:17:31,049 --> 00:17:32,910
and get millimeter level

455
00:17:33,609 --> 00:17:34,990
accuracy in their delivery.

456
00:17:35,450 --> 00:17:37,769
And so this camera system allows them to

457
00:17:37,769 --> 00:17:38,910
actually just see

458
00:17:39,214 --> 00:17:41,775
what's happening each day and and and help

459
00:17:41,775 --> 00:17:42,275
verify

460
00:17:42,894 --> 00:17:45,615
that the treatment is truly accurate. And, you

461
00:17:45,615 --> 00:17:47,934
know, I mean, let's face it. They're not

462
00:17:47,934 --> 00:17:50,494
all treatments are perfectly accurate, and so this

463
00:17:50,494 --> 00:17:52,670
camera can pick up little,

464
00:17:53,210 --> 00:17:56,330
incidents and help the therapy team, fix it

465
00:17:56,330 --> 00:17:57,309
when it does happen.

466
00:17:58,330 --> 00:18:00,490
Okay. So and is this in a routine

467
00:18:00,490 --> 00:18:01,789
clinical use yet?

468
00:18:02,650 --> 00:18:03,930
Yeah. So we,

469
00:18:04,809 --> 00:18:05,470
the company

470
00:18:06,134 --> 00:18:07,434
developed it as BeamSight.

471
00:18:08,134 --> 00:18:09,335
It got picked up,

472
00:18:09,654 --> 00:18:12,535
and is distributed by a British company called

473
00:18:12,535 --> 00:18:13,355
Vision RT,

474
00:18:14,134 --> 00:18:16,154
and they market it as DOSRT.

475
00:18:16,855 --> 00:18:17,734
It is now,

476
00:18:18,055 --> 00:18:20,789
in worldwide sales as of 2025,

477
00:18:21,109 --> 00:18:23,750
and I think the number is it's installed

478
00:18:23,750 --> 00:18:26,630
or being installed in over 40 cancer centers

479
00:18:26,630 --> 00:18:27,130
today.

480
00:18:27,430 --> 00:18:29,130
Oh, wow. That's that's impressive.

481
00:18:29,750 --> 00:18:30,250
Yeah.

482
00:18:31,029 --> 00:18:33,130
So, I mean, what's next in the pipeline

483
00:18:33,269 --> 00:18:34,650
for Cherenkov Imaging?

484
00:18:35,029 --> 00:18:36,470
Are there other things you can do with

485
00:18:36,470 --> 00:18:36,765
this

486
00:18:37,565 --> 00:18:40,445
technique? Yeah. So, I mean, I think we're

487
00:18:40,445 --> 00:18:43,884
in a a deployment phase where, you know,

488
00:18:43,884 --> 00:18:46,785
it's there were a couple early adopter academic

489
00:18:47,005 --> 00:18:49,164
medical centers that picked it up and used

490
00:18:49,164 --> 00:18:51,470
it, but we're really now in a phase

491
00:18:51,470 --> 00:18:52,529
where regular

492
00:18:52,909 --> 00:18:56,289
cancer therapy clinics are installing it, using it,

493
00:18:56,669 --> 00:18:57,150
and,

494
00:18:58,589 --> 00:19:01,390
they're using it in everyday radiotherapy. So that

495
00:19:01,390 --> 00:19:03,474
pay you know, every single day when a

496
00:19:03,474 --> 00:19:05,894
patient's getting treated, they can see it. And,

497
00:19:07,634 --> 00:19:10,674
we actually have a consortium of users now,

498
00:19:10,674 --> 00:19:13,714
and they sure sort of share stories and

499
00:19:13,714 --> 00:19:16,434
tips on how to use the technology and

500
00:19:16,434 --> 00:19:17,309
make sure that,

501
00:19:18,269 --> 00:19:21,009
they use it to effectively make their

502
00:19:21,309 --> 00:19:22,769
therapy as safe as possible.

503
00:19:23,070 --> 00:19:25,009
So we're in this kind of phase where

504
00:19:25,630 --> 00:19:27,090
there's a a growing

505
00:19:27,549 --> 00:19:29,570
slate of adopters, and those adopters

506
00:19:30,184 --> 00:19:30,845
are sharing

507
00:19:31,144 --> 00:19:32,924
use cases with each other.

508
00:19:33,785 --> 00:19:34,525
We are

509
00:19:35,704 --> 00:19:37,785
doing a couple different studies. You know, we're

510
00:19:37,785 --> 00:19:38,285
actually

511
00:19:38,744 --> 00:19:41,404
doing a study at Dartmouth now on contralateral

512
00:19:41,865 --> 00:19:44,369
breast dose. So, you know, the biggest use

513
00:19:44,369 --> 00:19:46,470
of radiation therapy is in breast cancer.

514
00:19:47,170 --> 00:19:50,470
And so women who get lumpectomy for

515
00:19:50,769 --> 00:19:51,750
a a cancer

516
00:19:52,130 --> 00:19:54,690
in the breast go on to radiation almost

517
00:19:54,690 --> 00:19:55,190
always.

518
00:19:56,464 --> 00:19:58,785
And the design of that radiation therapy is

519
00:19:58,785 --> 00:20:01,505
to treat the diseased breast, but do not

520
00:20:01,505 --> 00:20:04,404
treat the normal breast on the contralateral

521
00:20:04,785 --> 00:20:07,424
side. And but, you know, sometimes the alignment

522
00:20:07,424 --> 00:20:09,265
isn't as good as it should be, and

523
00:20:09,265 --> 00:20:11,285
and there can be dosed to the contralateral

524
00:20:11,505 --> 00:20:14,250
breast. And so we're doing a study now

525
00:20:14,869 --> 00:20:17,269
to minimize that to or to well, a

526
00:20:17,269 --> 00:20:19,130
a, to identify when it happens,

527
00:20:19,509 --> 00:20:21,690
and then the second step will be to

528
00:20:22,070 --> 00:20:26,095
develop techniques to minimize that and using Cherenkov

529
00:20:26,154 --> 00:20:27,775
as a tool. Again,

530
00:20:28,075 --> 00:20:31,055
you know, the the benefit of Cherenkov is

531
00:20:31,355 --> 00:20:33,855
that prior to its invention,

532
00:20:34,795 --> 00:20:37,279
radiation therapy is completely invisible. So

533
00:20:37,660 --> 00:20:39,519
the patient gets lined up on the

534
00:20:39,820 --> 00:20:41,279
patient treatment couch,

535
00:20:42,059 --> 00:20:44,380
and everybody walks out of the room, and

536
00:20:44,380 --> 00:20:46,000
the patient's lying there by themselves.

537
00:20:46,380 --> 00:20:49,144
Radiation therapy device is doing the treatments to

538
00:20:49,144 --> 00:20:49,644
them,

539
00:20:50,024 --> 00:20:52,825
and there's a video camera, you know, in

540
00:20:53,464 --> 00:20:54,764
displaying the patient,

541
00:20:55,944 --> 00:20:58,345
view to the therapy team, but they're outside

542
00:20:58,345 --> 00:21:00,125
the room, you know, a few

543
00:21:00,505 --> 00:21:01,404
meters away.

544
00:21:02,390 --> 00:21:04,470
And and nobody can see the treatment, you

545
00:21:04,470 --> 00:21:06,710
know, because the X rays aren't visible. So

546
00:21:06,710 --> 00:21:09,269
the TranKov allows the team to just very

547
00:21:09,269 --> 00:21:10,250
simply intuitively

548
00:21:10,710 --> 00:21:11,769
see the treatment.

549
00:21:12,070 --> 00:21:13,830
And that, I think, is the main benefit

550
00:21:13,830 --> 00:21:14,330
is,

551
00:21:14,710 --> 00:21:15,610
you know, safety,

552
00:21:16,845 --> 00:21:18,305
really needs to be simple.

553
00:21:19,325 --> 00:21:21,505
If the safety tools you're using

554
00:21:21,805 --> 00:21:22,545
are complicated,

555
00:21:22,924 --> 00:21:24,924
it means there's lots of room for human

556
00:21:24,924 --> 00:21:27,085
error. You know? So I think the the

557
00:21:27,085 --> 00:21:28,144
value of Chernkoff

558
00:21:28,605 --> 00:21:30,785
is that it makes safety simple,

559
00:21:31,570 --> 00:21:33,190
and very visual and intuitive.

560
00:21:33,570 --> 00:21:35,809
And, I think that will be the the

561
00:21:35,809 --> 00:21:37,830
lasting power of it as a technology.

562
00:21:38,369 --> 00:21:40,369
And I guess this light is just it's

563
00:21:40,369 --> 00:21:43,029
generated within the patient. You're not doing anything

564
00:21:43,170 --> 00:21:45,445
extra other than detecting it. It's sort of

565
00:21:45,445 --> 00:21:47,065
there for you to use already.

566
00:21:47,605 --> 00:21:50,005
That's right. It's it's always there. It just

567
00:21:50,005 --> 00:21:52,085
needs a camera system to pick it up

568
00:21:52,085 --> 00:21:54,325
and display it, and every every patient who

569
00:21:54,325 --> 00:21:57,285
gets radiation therapy could benefit from it just

570
00:21:57,285 --> 00:21:59,465
to verify that the treatment was accurate.

571
00:22:00,509 --> 00:22:02,590
And and, again, the the important piece of

572
00:22:02,590 --> 00:22:04,910
this is patients come in for many days

573
00:22:04,910 --> 00:22:06,830
in a row, typically thirty days in a

574
00:22:06,830 --> 00:22:08,830
row. So, you know, if if you make

575
00:22:08,830 --> 00:22:09,330
one

576
00:22:09,710 --> 00:22:12,509
small positioning error, you you can fix it

577
00:22:12,509 --> 00:22:13,994
for the other 29.

578
00:22:14,875 --> 00:22:17,214
And that's the key is is the tool

579
00:22:17,994 --> 00:22:19,694
because positioning is so

580
00:22:20,154 --> 00:22:21,855
is supposed to be so high precision,

581
00:22:22,954 --> 00:22:25,454
we need tools to verify that high precision,

582
00:22:25,835 --> 00:22:27,674
and then it's gotta be done every single

583
00:22:27,674 --> 00:22:29,700
day for thirty days in a row. So,

584
00:22:30,659 --> 00:22:33,380
that is where why it's so important to

585
00:22:33,380 --> 00:22:35,880
have a intuitive and easily used tool

586
00:22:36,259 --> 00:22:37,639
like Cherenkov Imaging.

587
00:22:38,980 --> 00:22:39,480
Excellent.

588
00:22:40,019 --> 00:22:40,679
And then

589
00:22:41,460 --> 00:22:43,960
shifting focus now, you you've also cofounded

590
00:22:44,259 --> 00:22:47,134
another company called Hypoxia Surgical,

591
00:22:47,755 --> 00:22:50,315
and this company is developing an imaging system

592
00:22:50,315 --> 00:22:53,515
to visualize oxygen levels in tissue in real

593
00:22:53,515 --> 00:22:54,015
time.

594
00:22:54,555 --> 00:22:57,055
So could you explain how this technology works?

595
00:22:58,009 --> 00:22:59,929
Sure. Yeah. So I I, you know, so

596
00:22:59,929 --> 00:23:02,089
I I'm an optics person in general, not

597
00:23:02,089 --> 00:23:03,230
really necessarily

598
00:23:03,769 --> 00:23:04,750
married to one

599
00:23:05,289 --> 00:23:08,029
therapy. I I work in surgical guidance technologies

600
00:23:08,250 --> 00:23:08,909
as well,

601
00:23:09,769 --> 00:23:12,075
and and there's a whole field of what

602
00:23:12,075 --> 00:23:15,275
is sometimes referred to as molecular guided surgery,

603
00:23:15,275 --> 00:23:17,694
where you wanna give the surgeon

604
00:23:18,394 --> 00:23:21,134
a view of what they're cutting or doing

605
00:23:21,434 --> 00:23:24,335
based on the molecular signatures of the tissue.

606
00:23:25,194 --> 00:23:27,990
And and that's really what this technology is

607
00:23:27,990 --> 00:23:28,470
is,

608
00:23:29,269 --> 00:23:32,710
we have, developed a, again, a time gated

609
00:23:32,710 --> 00:23:33,210
technique

610
00:23:33,750 --> 00:23:35,369
to image a light signal

611
00:23:35,750 --> 00:23:37,049
that comes out of tissue

612
00:23:37,590 --> 00:23:38,250
that is

613
00:23:39,494 --> 00:23:42,134
amplified when there's no oxygen. So it's high

614
00:23:42,295 --> 00:23:44,615
when the tissue is hypoxic or no oxygen

615
00:23:44,615 --> 00:23:45,275
in it,

616
00:23:45,654 --> 00:23:48,934
this special light signal comes out. And we

617
00:23:48,934 --> 00:23:49,674
we induce,

618
00:23:50,775 --> 00:23:53,255
where we amplify that light signal by giving

619
00:23:53,255 --> 00:23:54,154
the the patients

620
00:23:54,829 --> 00:23:55,490
a metabolic

621
00:23:55,789 --> 00:23:56,930
drug called aminolubalinic

622
00:23:57,470 --> 00:24:00,529
acid. It's a very, commonly used agent,

623
00:24:01,549 --> 00:24:04,750
for a number of diagnostic and therapeutic conditions.

624
00:24:04,750 --> 00:24:07,089
So it's in wide human use.

625
00:24:08,750 --> 00:24:10,609
The cameras that we have developed,

626
00:24:11,204 --> 00:24:13,065
again, pick up when

627
00:24:13,845 --> 00:24:16,505
a signal from the tissue when it's hypoxic.

628
00:24:16,724 --> 00:24:20,265
And, you know, oxygen is ubiquitous in living

629
00:24:20,724 --> 00:24:23,220
organisms and tissue. Right? So when there's a

630
00:24:23,220 --> 00:24:26,200
lack of oxygen, that's a a disease state.

631
00:24:26,579 --> 00:24:27,880
And so tumors

632
00:24:28,259 --> 00:24:30,519
or peripheral vascular disease

633
00:24:31,140 --> 00:24:31,640
or,

634
00:24:32,420 --> 00:24:33,640
compromised lymphatics,

635
00:24:34,579 --> 00:24:35,400
have hypoxia.

636
00:24:35,859 --> 00:24:37,079
And so that's where

637
00:24:37,454 --> 00:24:38,674
this imaging tool,

638
00:24:39,534 --> 00:24:42,414
could have, its potential. So we're in early

639
00:24:42,414 --> 00:24:43,714
stage of this company,

640
00:24:44,575 --> 00:24:45,714
Hypoxia Surgical.

641
00:24:46,335 --> 00:24:47,875
The camera systems developed

642
00:24:48,255 --> 00:24:51,134
were exploring a couple different sort of medical

643
00:24:51,134 --> 00:24:52,349
use cases of it.

644
00:24:52,910 --> 00:24:53,809
But we know

645
00:24:54,109 --> 00:24:56,829
that the lack of oxygen is indicative of

646
00:24:56,829 --> 00:24:58,609
damage or disease.

647
00:24:58,990 --> 00:25:01,390
And so there's we're pretty confident that it

648
00:25:01,390 --> 00:25:02,210
will have

649
00:25:02,509 --> 00:25:03,809
its role in medicine.

650
00:25:04,109 --> 00:25:04,724
It's just,

651
00:25:05,365 --> 00:25:07,924
determining which one it is. And right now,

652
00:25:07,924 --> 00:25:10,345
we're looking at surgical guidance for,

653
00:25:11,125 --> 00:25:12,984
cancer or lymph nodes

654
00:25:13,285 --> 00:25:14,984
as one of the more compelling

655
00:25:15,444 --> 00:25:18,339
application areas for it. Yeah. But is there

656
00:25:18,339 --> 00:25:20,200
a way it could be used in radiotherapy

657
00:25:20,579 --> 00:25:22,359
as well? Because, obviously, hypoxia

658
00:25:23,220 --> 00:25:25,720
is a big important part of such treatments.

659
00:25:26,259 --> 00:25:28,994
Yeah. Great question. So oxygen is a is

660
00:25:28,994 --> 00:25:32,035
a very important molecule in radiation therapy. It

661
00:25:32,035 --> 00:25:34,835
increases the effect of radiation by close to

662
00:25:34,835 --> 00:25:35,894
a factor of three.

663
00:25:36,355 --> 00:25:39,795
So the lack of oxygen would increase would

664
00:25:39,795 --> 00:25:42,115
would indicate that radiation therapy would not be

665
00:25:42,115 --> 00:25:44,960
very as effective. And so we are exploring

666
00:25:45,099 --> 00:25:46,220
that use in,

667
00:25:46,619 --> 00:25:47,119
radiotherapy

668
00:25:47,660 --> 00:25:49,599
as a adjuvant tool as well.

669
00:25:50,539 --> 00:25:53,519
And this is more in early stage investigation,

670
00:25:54,059 --> 00:25:56,480
you know, studies in animals right now.

671
00:25:56,865 --> 00:25:59,505
But, for sure, we we can use it

672
00:25:59,505 --> 00:26:00,005
to,

673
00:26:01,025 --> 00:26:03,444
see when radiotherapy will be less effective.

674
00:26:04,224 --> 00:26:05,744
And then there's this,

675
00:26:06,144 --> 00:26:09,204
ultra high dose rate radiotherapy that actually consumes

676
00:26:09,265 --> 00:26:10,484
oxygen very rapidly,

677
00:26:10,869 --> 00:26:13,669
and so we're using the hypoxia surgical cameras

678
00:26:13,669 --> 00:26:15,130
to image that as well.

679
00:26:16,470 --> 00:26:18,009
So it's been a great tool.

680
00:26:19,190 --> 00:26:21,589
You know, figuring out its use case in

681
00:26:21,589 --> 00:26:23,589
radiotherapy will take a little bit of time,

682
00:26:23,589 --> 00:26:26,089
but we're certainly working on that right now.

683
00:26:27,575 --> 00:26:28,075
Excellent.

684
00:26:28,695 --> 00:26:29,195
So

685
00:26:29,734 --> 00:26:31,115
many of these developments

686
00:26:31,894 --> 00:26:34,695
would have been published in the journal Physics

687
00:26:34,695 --> 00:26:36,154
in Medicine and Biology,

688
00:26:36,615 --> 00:26:40,359
which is celebrating its seventieth anniversary this year.

689
00:26:40,359 --> 00:26:41,799
So so with that in mind, I wonder

690
00:26:41,799 --> 00:26:43,400
if you could give us an example of

691
00:26:43,400 --> 00:26:45,559
some exciting research that you or your team

692
00:26:45,559 --> 00:26:47,179
has has published in PMB.

693
00:26:48,440 --> 00:26:49,960
Sure. Yeah. I mean, we've,

694
00:26:50,359 --> 00:26:51,179
I've published

695
00:26:51,535 --> 00:26:54,255
so many articles in PMB. It's actually hard

696
00:26:54,255 --> 00:26:54,914
to choose,

697
00:26:55,535 --> 00:26:56,595
which one exactly.

698
00:26:57,134 --> 00:26:57,954
But, certainly,

699
00:26:59,055 --> 00:27:00,115
the use of,

700
00:27:00,575 --> 00:27:02,674
oxygen imaging and flash radiotherapy

701
00:27:03,055 --> 00:27:05,830
has been a big one. And, we recently

702
00:27:05,970 --> 00:27:07,670
published a paper where we

703
00:27:07,970 --> 00:27:09,910
looked at the oxygen consumption

704
00:27:10,289 --> 00:27:12,230
in flash radiotherapy and,

705
00:27:12,690 --> 00:27:14,549
how it can be a limitation

706
00:27:15,570 --> 00:27:16,710
in, delivery.

707
00:27:18,515 --> 00:27:20,275
In in the field of flash radiation therapy,

708
00:27:20,275 --> 00:27:22,755
people are trying to figure out, what's going

709
00:27:22,755 --> 00:27:26,035
on. Like, in flash radiotherapy, if you give

710
00:27:26,035 --> 00:27:28,134
very high dose rate radiation,

711
00:27:28,835 --> 00:27:31,555
you reduce the damage to normal tissue, but

712
00:27:31,555 --> 00:27:33,815
you don't reduce the damage to tumor tissue.

713
00:27:33,900 --> 00:27:36,539
So that's the mystery. Like, why nobody can

714
00:27:36,539 --> 00:27:39,180
explain why that's true. Why do we reduce

715
00:27:39,180 --> 00:27:41,200
damage to normal tissue but not tumors?

716
00:27:41,660 --> 00:27:44,320
And so we're looking at the oxygen effect

717
00:27:44,859 --> 00:27:46,320
and its role,

718
00:27:46,835 --> 00:27:49,954
and that's what we published recently in,

719
00:27:50,355 --> 00:27:50,855
PMB,

720
00:27:52,355 --> 00:27:54,355
to try to explain that we we don't

721
00:27:54,355 --> 00:27:55,095
have the

722
00:27:55,394 --> 00:27:56,755
solution yet. It's like,

723
00:27:57,154 --> 00:27:59,394
we're writing a mystery novel, but we don't

724
00:27:59,394 --> 00:28:01,174
have the last chapter. You know?

725
00:28:01,880 --> 00:28:02,700
But, certainly,

726
00:28:03,240 --> 00:28:05,019
the pieces of the story

727
00:28:05,399 --> 00:28:06,859
are that oxygen is involved,

728
00:28:07,240 --> 00:28:08,779
and the consumption of oxygen

729
00:28:09,319 --> 00:28:12,039
changes when you change the dose rate. And

730
00:28:12,039 --> 00:28:14,244
so we think that's an important piece. We

731
00:28:14,244 --> 00:28:16,804
think it's a we know it's a major

732
00:28:16,804 --> 00:28:19,464
factor, but we we don't know the underlying

733
00:28:19,605 --> 00:28:22,565
mechanism yet. And, hopefully, that'll be our next

734
00:28:22,565 --> 00:28:25,765
paper once we discover the mystery of flash

735
00:28:25,765 --> 00:28:28,680
and publish that in PMB as well. Excellent.

736
00:28:28,740 --> 00:28:30,180
Yes. I want to keep an eye out

737
00:28:30,180 --> 00:28:30,660
on,

738
00:28:31,140 --> 00:28:33,140
I guess, what once the mystery is solved,

739
00:28:33,140 --> 00:28:35,000
then maybe we'll see FLASH

740
00:28:35,299 --> 00:28:35,799
radiotherapy

741
00:28:36,660 --> 00:28:38,519
in you being used in the clinic perhaps.

742
00:28:39,299 --> 00:28:41,720
It is. Yeah. There are clinical trials ongoing,

743
00:28:42,855 --> 00:28:44,934
but like most things in medicine, you know,

744
00:28:44,934 --> 00:28:46,634
you don't have to know the mechanism

745
00:28:47,095 --> 00:28:49,575
to use it clinically. So it is being

746
00:28:49,575 --> 00:28:50,555
explored clinically,

747
00:28:51,335 --> 00:28:53,654
but I think it would most people would

748
00:28:53,654 --> 00:28:55,440
agree it'd be more comforting if we sort

749
00:28:55,440 --> 00:28:57,960
of had at least a really solid guess

750
00:28:57,960 --> 00:29:00,460
about the underlying mechanism for how it works.

751
00:29:00,839 --> 00:29:03,419
And so we wanna do both, really.

752
00:29:04,039 --> 00:29:04,539
Exactly.

753
00:29:05,079 --> 00:29:08,059
Okay. And then finally, looking into the future,

754
00:29:08,595 --> 00:29:10,855
where do you see optics having the biggest

755
00:29:10,914 --> 00:29:13,954
impact in impact in medical physics? So,

756
00:29:14,275 --> 00:29:17,815
will the techniques that we discussed become increasingly

757
00:29:17,954 --> 00:29:21,015
common perhaps for guiding and improving radiotherapy?

758
00:29:21,829 --> 00:29:23,509
Or do you think perhaps there's another area

759
00:29:23,509 --> 00:29:26,150
of medical physics in which optics could play

760
00:29:26,150 --> 00:29:27,609
a a really important role?

761
00:29:28,869 --> 00:29:31,109
Yeah. That's a great question. It's a question

762
00:29:31,109 --> 00:29:33,269
I think about all the time because I

763
00:29:33,269 --> 00:29:34,890
live in both of these worlds.

764
00:29:36,255 --> 00:29:38,894
It's almost impossible for me to pick one

765
00:29:38,894 --> 00:29:40,755
area, you know, but I I would just,

766
00:29:41,215 --> 00:29:43,634
leave off perhaps by saying, you know,

767
00:29:44,414 --> 00:29:47,535
the use of optics is much, much larger

768
00:29:47,535 --> 00:29:48,755
than the use of radiation

769
00:29:49,055 --> 00:29:51,269
in medicine. Right? And so the tools

770
00:29:52,210 --> 00:29:53,190
for imaging

771
00:29:53,569 --> 00:29:56,309
or diagnosing things with optics are incredible.

772
00:29:57,650 --> 00:29:58,470
And so

773
00:29:58,849 --> 00:29:59,670
the intersection

774
00:30:00,369 --> 00:30:01,829
between radiation medicine

775
00:30:02,695 --> 00:30:03,914
and optical diagnostics

776
00:30:04,215 --> 00:30:06,394
or therapeutics is really wide open.

777
00:30:06,775 --> 00:30:08,795
You know, we're looking at some,

778
00:30:09,894 --> 00:30:12,875
we're looking at some areas now where optical

779
00:30:12,934 --> 00:30:13,434
photosensitizers

780
00:30:14,535 --> 00:30:16,315
can become radiation sensitizers.

781
00:30:16,849 --> 00:30:19,009
You know, that's one really exciting area to

782
00:30:19,009 --> 00:30:21,750
me. But even more broadly than that, just

783
00:30:22,049 --> 00:30:23,750
the idea that optical,

784
00:30:24,690 --> 00:30:27,190
diagnostics and treatments can be combined

785
00:30:27,570 --> 00:30:28,230
with radiation

786
00:30:28,930 --> 00:30:31,865
therapy or diagnostics or treatments. To me, that's

787
00:30:31,865 --> 00:30:34,444
the intersection that is really fertile

788
00:30:35,065 --> 00:30:37,164
and and really quite unexplored.

789
00:30:38,184 --> 00:30:41,065
There's only a handful of researchers I know

790
00:30:41,065 --> 00:30:43,085
working at that intersection space,

791
00:30:43,464 --> 00:30:46,130
but it's huge because both fields are enormous.

792
00:30:46,190 --> 00:30:48,929
You know, again, the optical devices are just

793
00:30:49,230 --> 00:30:49,730
everywhere.

794
00:30:50,109 --> 00:30:52,130
Radiation is incredibly powerful.

795
00:30:53,710 --> 00:30:56,190
And and and often, they kill tissue in

796
00:30:56,190 --> 00:30:57,409
a complimentary ways

797
00:30:57,950 --> 00:30:58,929
or the diagnostic

798
00:30:59,309 --> 00:31:00,904
measurements are complimentary.

799
00:31:01,365 --> 00:31:03,625
You know? X rays are good at structure.

800
00:31:04,005 --> 00:31:06,025
Optics is good at molecular signatures.

801
00:31:06,404 --> 00:31:08,485
You know? So why not combine them to

802
00:31:08,485 --> 00:31:10,424
get more detailed information?

803
00:31:11,445 --> 00:31:13,365
That those those are the areas that excite

804
00:31:13,365 --> 00:31:15,319
me the most and I think has

805
00:31:15,940 --> 00:31:17,079
the enormous potential

806
00:31:17,380 --> 00:31:18,919
for, future development.

807
00:31:20,740 --> 00:31:23,380
Brilliant. Well, thank you very much for speaking

808
00:31:23,380 --> 00:31:24,279
with us today.

809
00:31:24,819 --> 00:31:26,740
Sure. Well, thank you, Tammy. It's been a

810
00:31:26,740 --> 00:31:27,240
pleasure.

811
00:31:35,264 --> 00:31:37,044
That was the medical physicist

812
00:31:37,345 --> 00:31:41,105
Brian Pogue in conversation with Physics World's Tammy

813
00:31:41,105 --> 00:31:41,605
Freeman.

814
00:31:42,339 --> 00:31:45,159
It was recorded in association with the journal

815
00:31:45,460 --> 00:31:47,639
Physics in Medicine and Biology,

816
00:31:48,259 --> 00:31:49,159
which celebrates

817
00:31:49,539 --> 00:31:50,359
its seventieth

818
00:31:50,740 --> 00:31:52,200
anniversary this year.

819
00:31:52,740 --> 00:31:55,779
I'm Hamish Johnston, and our producer is Fred

820
00:31:55,779 --> 00:31:56,279
Iles.

821
00:31:56,965 --> 00:31:58,744
The theme music for this podcast

822
00:31:59,045 --> 00:32:01,684
is called one three seven, and it was

823
00:32:01,684 --> 00:32:03,144
composed and performed

824
00:32:03,445 --> 00:32:04,424
by the physicist

825
00:32:05,045 --> 00:32:06,184
Philip Moriarty.

826
00:32:07,285 --> 00:32:08,105
This episode

827
00:32:08,485 --> 00:32:10,825
is supported by One Physics.

828
00:32:11,940 --> 00:32:13,799
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829
00:32:14,419 --> 00:32:14,919
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00:32:17,940 --> 00:32:20,019
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844
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