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An Interview with Geoffrey Ibbott, PhD, FASTRO

By Stacy Wentworth, MD, and Muthana (Matthew) Al-Ghazi, PhD

The following interview of Geoffrey Ibbott, PhD, FASTRO, was conducted on November 13, 2023, by Stacy Wentworth, MD, and Muthana (Matthew) Al-Ghazi, PhD.

Stacy Wentworth: Thank you so much for being with us. Would you just tell us a little bit about your family and growing up? Are there any physicists in your family? Just a little bit about your childhood and how you grew up.

Geoffrey Ibbott: Sure. Well, as I think you and Matthew have mentioned, I was born in England, in London, which was where both my parents were born and I think my grandparents too – in London or nearby. But shortly after I was born we moved to sort of a bedroom community of London, a little village to the southeast in Kent. So I say I grew up there, in Kent. I have one younger brother. So it was just the four of us.

But while I was still young, when I was eight years old actually, my father accepted a position to move to the U.S. So I really only had three or four years of school in England before we moved to Colorado. Nobody else in my family was a physicist, but my father was a biochemist. He arrived at his final career path in somewhat the same way I did mine.

He was recruited right out of high school, at the latter part of World War II, to build a chemistry lab at a hospital. It was a mental hospital that was being converted to treat war-wounded soldiers and I suppose civilians that were injured in the war, although there were still some psychiatric patients there. That’s where my parents met because my mother was a nurse, actually a nurse in training, at the same hospital. So I think his scientific interest and background certainly helped steer me in that direction.

When we moved to Colorado, he became chief of a clinical lab in Denver. It was part of the University of Colorado, but at the medical center which at the time was in Central Denver. It since moved to one of the eastern suburbs. He had been recruited by a pediatrician from also in London, someone he had worked with there. The objective was to create a lab that specialized in what they called then, and maybe still do, pediatric microchemistry. They literally did write the book on performing a myriad of tests on a single drop of blood from a newborn baby’s heel. The last time I was aware of it, I think their book was in its – I don't know – 30th printing or something like that.

He got me summer jobs at the medical center. And in high school, I suppose it was 11th grade, I took a physics course. I'd been struggling, especially struggling with chemistry, because I for a long time wanted to follow in his footsteps, but I didn't take well to chemistry. In comparison, physics just seemed completely natural. So my dad spoke with the medical physicist who had recently arrived at Colorado. There had been several others. In fact, Eric Hall was the medical physicist at the University of Colorado for a while. Then there was another physicist, Arnold Feldman, a lovely person who I enjoyed knowing for many years after that. But the person my dad then spoke to was Bill Hendee. Bill agreed to take me on for the summer. As he describes it, he did it under duress because my father was so insistent and I needed to be kept off the streets in the summer. And maybe this was finally something that I would be interested in doing. It was. It went very well. In fact, that summer, I spent almost the entire summer reading TLDs. As Matthew noted, that resulted in a publication. Of course, I did the measurements without, I suppose, really understanding exactly what it was I was doing but enjoying it anyway. So Bill and a couple of other people and I got a paper out of that. That was my first publication when I just graduated from high school. I went away to college for a year, to Oregon, and came back. Bill offered me another job that second summer. I did that and again things went well. Partway through that summer he suggested that I transfer to a college in Colorado and continue working part time while I went to school. So I did that and that went well.

But shortly after that my girlfriend got pregnant and so we had to get married. In those days there didn't, at least to me, seem to be another option. So my working part time and going to school full time quickly transitioned to working full time and going to school part time. Now the marriage didn't last long, but I – 

Stacy Wentworth: So you're newly married with a new baby and still going for physics now?

Geoffrey Ibbott: Yeah, and trying to get through my undergraduate degree. As I say, the marriage lasted less than two years actually. But I continued to work full time and go to school part time because I was enjoying the work. I guess I had become accustomed to the income and, for the obvious reasons, I still needed that income even though we were no longer married. So as a result it took me 12 years to get my undergraduate degree. But I was working full time pretty much all of that time and enjoying it, getting involved in various research projects.

Stacy Wentworth: So you're saying that the recommendation to achieve the success that you have achieved is to take 12 years to do your undergraduate degree, Dr. Ibbott. That must have been such an exciting time to be in radiation oncology though. I mean that was right as everything was happening. I mean that must have been really cool.  

Geoffrey Ibbott: It was very exciting. Yeah. We were changing from cobalt units to linear accelerators. We were learning that there was so much more we could do with a linear accelerator.

Stacy Wentworth: Yes.

Geoffrey Ibbott: But a colleague at the University of Colorado, I guess, she was the physics instructor in the technology program, told me that she was going to imaging because everything that was ever going to be done in therapy had been done and it had plateaued and there would be nothing new there. Of course, this was at that point probably in the very early '70s. How wrong she was.

So it was great. It was a wonderful department. Bill Hendee was just a fabulous mentor and adviser who gave me all the opportunities I could handle and probably more and encouraged me so that I did ultimately finish my bachelor’s. By that time we'd started a master's program in the department and, in fact, I was already teaching some of the classes in the master's program. I went through the master's program very quickly and continued to work in the department after I finished my master's.

Again, I continued to have a lot of opportunities to teach. A lot of that teaching led to publications because the students, while it was a master's program, they weren't required to write a formal thesis. They all did projects and their projects were all publishable in one way or another. So many of those students got publications.
I was still doing some of my own things and as Matthew mentioned, at that point we were getting involved in hyperthermia as well. So that led to some interesting travel and a lot of very interesting research both in physics and clinical work. Somewhere along there I decided that I really enjoyed the academic environment and I would need a PhD to continue to progress in that environment. We didn't have a medical physics PhD at that time. There were a few people who did a PhD in the physics department in Boulder and did their research in medical physics. I considered that as a possibility, but the other option was to do my PhD in radiation biology. That appealed to me. I'm not really sure why it appealed to me more than the Boulder program, but it did. I had opportunities there to work with people like Mort Elkind and Ed Gillette. Ed Gillette was my adviser for my research there. I was able to do my research in Denver at the medical center, but I did have to go to Fort Collins for class. So I spent two years driving to Fort Collins on a pretty regular basis. On the first year I was driving there four days a week.

Stacy Wentworth: Oh, my god.

Geoffrey Ibbott: So I put lots of miles on my car, but I learned lots of very interesting biology and chemistry. That was sort of an awakening because by then I had come to grips with chemistry, to some extent anyway. I had a lot of very interesting and educational conversations with my father then as I was taking my first biochemistry class. Every meal turned into a chemistry lesson at that point in my life, at least when I was with him.

So I did finish my PhD through Fort Collins, but just as I finished it the circumstances in Denver had changed. Bill Hendee had left Colorado a few years earlier. I believe he went straight from there to the AMA. The physicians that I worked with there and thoroughly enjoyed were leaving and being replaced by other people. Good people, but it wasn't the same group and it wasn't the same environment.

In the meantime I met my second wife--my current wife. She at the time was working as a dosimetrist in the department. So we maintained a very secret relationship for quite a while, but then did get married. This was just before we decided that we were ready to leave that department and look for something new. We looked at several different opportunities. One was Yale. So I ended up taking a position at Yale and Diane took a dosimetrist position at another hospital in Connecticut. That was a good experience. I went from being essentially the solo physicist in radiation therapy in Colorado - although for the last year or two we had expanded and I had been able to recruit one of our graduate students to join me. But I went from that group to a larger group. Not huge, but I was one of four clinical physicists. And there were two other senior physicists. The senior physicist who recruited me was Bob Schulz. He's well-known in the early days of clinical dosimetry. Matthew might remember the name as one of the authors of TG-21.

Muthana (Matthew) Al-Ghazi: Yes, yes. The new TG.

Geoffrey Ibbott: Yeah. He and Ravi Nath, who was also there. Working with Bob Schulz was my introduction to gel dosimetry because Bob had a postdoctoral fellow called Marek Maryanski who got interested in this. Bob and an imaging physicist named Gore. I had forgotten his first name.

Muthana (Matthew) Al-Ghazi: John Gore.

Geoffrey Ibbott: John Gore. Thank you.

Muthana (Matthew) Al-Ghazi: Yeah, John Gore. Yes.

Geoffrey Ibbott: Bob Schulz and John Gore had been pushing this idea around and had done some early work. Maryanski picked that up and really developed it and developed some early polymerizing gels that looked very promising. We got some good work done there and I was able to carry that with me when I moved to Kentucky.
Bob Schulz had retired and actually now lives only about ten miles away from me here in Vermont. He had moved up here when he retired, so we see him actually very frequently. But I moved to Kentucky. I got the opportunity to go there and be the chief of a group of about a dozen people - six or seven physicists, and some technical and administrative people, and dosimetrists. So I was able to take the gel dosimetry work with me. I think the only time I've made the cover of the Red Journal was with a publication that at the time was in Kentucky.

We held the first of what we called at the time the dose gel meetings. They turned into the International Conference on 3-D Dosimetry as we didn't want to restrict it to just gels at that point. By then we'd made some other three-dimensional dosimeters that weren't gels, so maybe it was appropriate to expand. But that was the first one in Kentucky in 1999, the year I was president of the AAPM.

Muthana (Matthew) Al-Ghazi: Correct.

Stacy Wentworth: What was that like presenting that, about 3-D dosimetry? Did people think, "oh my gosh, who's this crazy guy from Kentucky?" What was that like when you were hosting these conferences? I can imagine there's believers and non-believers.

Geoffrey Ibbott: Absolutely. And there still are today. Sadly we're really not much closer to this being a clinically – I was going to say not so much clinically useful – it's very, very useful, but not a well-accepted tool. The reason is that it's still a bit of an art when we make gels or these other devices. Sometimes they are more sensitive than other batches we make. We don't know why. They are a bit messy to deal with, but they give you a full three-dimensional volume of data with one exposure. So they're quite an incredible tool in that sense.

I'm still working in that area as are a number of other people. There's a group of devotees all around the world. We get together every two years typically and hear about the new research. Many of these people are using gels routinely in their own clinics. But we just haven't done very well exporting it outside the research environment.

Stacy Wentworth: Were you doing a lot of photon dosimetry, or were you guys into neutrons at that point, or with cesium or radium? Was that all-encompassing for early physicists? I apologize for my lack of knowledge but –

Geoffrey Ibbott: No. Not at all. You don't need to.

Stacy Wentworth: Yeah. There's never been anything but really photons and HDR during my career. Maybe a little prostate LDR, but that's it.

Geoffrey Ibbott: Oh, sure. Potentially devices like these are useful for any radiation source; any source that results in ionization in a medium. In the case of some of our solid dosimeters, those result in a color change and they're more sensitive to some radiation than others. But still, yeah, protons, neutrons, external beam and brachytherapy are all valid uses for 3-D dosimetry.

But there's one challenge with brachytherapy in particular. That is, to measure the dose distribution around a brachytherapy source, you have to put the source into the dosimeter. So you either have to drill a hole into the dosimeter if it's a solid material or you have to pour a gel around the catheter. Yeah, that's certainly doable. When you do that, you limit the number of ways you can analyze the dosimeter because for most dosimeters we analyze them either with MRI – because a gel changes the paramagnetic parameters of the water molecules in the gel, and so we can image the gel with MRI. Or we do it optically. Putting a catheter or drilling a hole into a dosimeter interferes with the optical properties of the gel. The reason we can do it with what we call optical CT. It really is CT scanning but with a laser instead of an X-ray beam. Otherwise, it's exactly the same principle. We're making an image of the opacity or the color change in the dosimeter.

Stacy Wentworth: Yeah. Fascinating.

Geoffrey Ibbott: Yes, it is a fascinating technology and a great tool. So even after I left Kentucky and moved to MD Anderson, I was able to continue the project there. I'll jump ahead just a little bit because it fits. While I was at MD Anderson, we were approached by Elekta who were developing their MR-LINAC at that point. Ultimately we became the first clinical site and the first site outside of the Netherlands where the development work was done and the prototypes were installed. We were the first site to receive a clinical version of Elekta's MR-LINAC and that was exciting enough. But my interest in gel dosimetry revealed another interest because here's a device that you could not only irradiate a 3-D dosimeter but you could then do the analysis. In fact, we published some papers showing that we could do real-time dosimetry. We could image our dosimeter as we were delivering the radiation and watch the dose distribution develop. So that was truly fascinating.

Stacy Wentworth: Was there any conflict between you and your wife, who was a dosimetrist, when you told her their plans weren't really that good or she wasn't delivering what she thought she was?

Geoffrey Ibbott: I never evaluated any of her work.

Stacy Wentworth: That's probably very smart.

Geoffrey Ibbott: Yeah. Right. But while I was still at Anderson, we did really the sort of development work there, proof-of-principle kind of work. We were just on the verge I think of using gel dosimetry as a clinical tool when it came time for me to retire. So that phase of the work has lapsed somewhat. But in retirement I've had the opportunity to work with an MD Anderson partner site in New Jersey. So MD Anderson started developing this network of partner sites of different levels. One of them is Cooper Hospital in Camden, New Jersey. My last position job at MD Anderson was as the sort of liaison. I was in charge of the physics aspects of this network of affiliate sites. So I came to know the people at Cooper well. When I retired they invited me to consult with them and that consultation continues today. It was ideal because the first aspect of that consultation was to help them select and install an MR-LINAC.

Stacy Wentworth: Wow.

Geoffrey Ibbott: I did that, but I was very open about the fact that I really did have a conflict with this experience with the Elekta system. But I tried to be very objective and I wrote up an analysis of both the Elekta and the ViewRay systems. Of course, this was a number of years ago. They went with the Elekta device of which I am very glad especially in light of the events of the last couple of months. So I jumped way ahead pretty much to the present.

Let me go back to the reasons for moving to Houston and to MD Anderson. I was approached by Ken Hogstrom, who was the chairman of radiation physics at MD Anderson, to come to Houston to lead what was at that time called the Radiological Physics Center or RPC. I really had not considered leaving Kentucky at that point and I certainly hadn't considered going to Texas at that point. We’d lived in northern states or the mid, well, the west – Colorado. But it sounded interesting. I have been familiar with the RPC for many years and I knew Will Hanson, who was currently the director, very well and had for years. He was retiring so they were looking for someone to take his position. After a couple of visits, I was sold on the job and the opportunity. So we moved to Houston at the beginning of 2001 and I took over as director of the RPC and chief of what they called the Section of Outreach Physics which was mainly two big programs. The RPC was one of them, and Marilyn Stovall's group was the other program.

Marilyn Stovall and her team did two things: one, was they also ran a mailed TLD program for audits, but it was a program that people could purchase and still can. It still exists. Rebecca Howell now leads that group. The program was available, as I say, for people to audit their own dosimetry as a second check backup. Hundreds of departments around the country and a few internationally have used it over the years and continue to.

The RPC did a mailed TLD program that was essentially at the time identical, but it was specifically for participants in clinical trials. In fact, the RPC was funded through a grant from the National Cancer Institute. That grant supported not only the TLD program and the staff that were needed to maintain that program, but the phantoms that we mailed to do an end-to-end check of stereotactic and IMRT treatments and audits that we did of dosimetry information.

Depending on the circumstances, people would either mail us their dosimetry information and fairly soon we started receiving that electronically. But we also had the program of visiting a number of institutions. We would visit, I think we'd visit 30 or 40 institutions a year. This was done by a staff of physicists. So there were seven, or eight, or more physicists who would travel at least five or six times a year. So, yeah, we would visit 40 or more institutions a year.

We would do essentially a very thorough commissioning or recommissioning check of a linear accelerator in the evening, after the institution had finished their treatments between about 5:00 p.m. or 6:00 p.m., whenever we get the machine. We tried not to keep the local staff out past midnight while we were doing this. We would make a complete set of measurements that we could then compare with the institution's own dosimetry data. Then over the course of, well, however many days it took, if they had two or three LINACs, one person would work the two or three evenings. If they had more than that, we would send two or even three physicists so that we could get the job done in no more than three or four days.

Stacy Wentworth: Did that increase your confidence in the physicists that were being trained or did you feel like there is a wide variety? I mean I guess I am, again, post-IMRT, so all of these had been figured out by the time I entered radiation. But I can imagine there was a wide variance when you first went out and then it kind of narrowed, hopefully.

Geoffrey Ibbott: Absolutely right, yes. Not only the visits but the phantoms increased as IMRT became more widely used. The visits, we measured more basic data. But as IMRT became more important we started measuring data that was relevant for IMRT as well. And you're right, in those early days of IMRT there was a huge variation in the quality of dosimetry, the understanding of the technology, and in particular the understanding that physicists in hospitals had of their planning systems and how to commission them.

So I told you about making the cover of the Red Journal. I made The New York Times too – not just me, but the RPC did. But I was the lucky one that got to be interviewed because The New York Times at that time had someone come to an AAPM or ASTRO meeting where I gave a talk about our early results with the phantoms evaluating IMRT. Our early experience, the first 20 or 30 irradiations with the phantoms, a third of the institutions failed to meet the criteria. That was already relaxed criteria. We were very generous at the time. It was 7% dose and four millimeters distance to agreement.

Stacy Wentworth: Wow.

Geoffrey Ibbott: Yeah, 35% of the institutions did not meet those criteria.

Stacy Wentworth: Holy moly.

Geoffrey Ibbott: Ultimately, we did learn that the problem in many cases was not understanding and not commissioning the treatment planning system correctly. Because it wasn't until IMRT that how well you modeled the beam in the penumbra was really critical. For conventional 3-D and even for stereotactic work, it didn't matter very much.

Stacy Wentworth: Yes. Right.

Geoffrey Ibbott: But for IMRT, it was huge. But then we found problems with machines themselves, MLCs that didn't move properly, or that the leaves sagged when the gantry rotated because of gravity.

Stacy Wentworth: What year was this, Doctor? 1980 –

Geoffrey Ibbott: This was the early 2000s.

Stacy Wentworth: Oh gosh.

Geoffrey Ibbott: Yeah. It wasn't that long ago.

Muthana (Matthew) Al-Ghazi: Can I provide a confirmatory statement on this particular topic?

Geoffrey Ibbott: Yes.

Muthana (Matthew) Al-Ghazi: I can attest to the value of the RPC and IROC. I have to say that throughout my career I would never turn the machine on a patient until I got the clearance from what was the RPC and then later on IROC, and the same one for the IMRT program. I was privileged to have other opportunities to have all vital phantoms already at my former institutions. Thankfully throughout I got a clear record. Once we didn't make the criteria, and that was because our setup wasn't correct. Not because our data was incorrect. I have to say this is just an incredible, incredible peer-review tool. You know being an academic institution we contribute to clinical trials. We cannot enroll patients on trials unless we got the certificate from RPC that we're complying with their criteria. So this is really an incredible patient safety issue that I am not sure we can do without. The radiation, once you give it, you can't take it back and there is no antidote to it. So this is something that's incredibly, incredibly useful. No matter how good your staff are, no matter how careful I was, I would never rest until I get the clearance from IROC. Thanks to Geoff's leadership, the RPC was transformed to IROC. Its activities and the complexity of techniques and all of these were totally expanded, and revamped, and carefully thought out. I have to say that this is grant money, NCI grant money that is totally, totally worth every cent.

Geoffrey Ibbott: Thank you, Matthew.

Muthana (Matthew) Al-Ghazi: With image-based treatment planning and delivery with motion management and all of these and complexity of the trials, I am happy to say that I am a bit of a stickler. I always calibrate it to 1% accuracy so that I can be sure that the RPC or IROC subsequently would give me the green light to go ahead. To date I have a clean record.

Geoffrey Ibbott: Excellent. While I was in that position I, of course, had a lot of opportunities to speak at meetings about the results, but also on panel discussions where I could encourage people to do exactly as Matthew has done – that before they institute a new procedure, to request a phantom from the RPC. In fact, that became so popular that it wasn't just clinical trials participants who wanted to test the technologies. So we expanded and built many more phantoms, recruited some more people, and developed a fee-for-service version of that program so people could purchase that service.

Stacy Wentworth: Geoff, do you think it should be a government requirement? That every year or every new center and every new LINAC, that that's part of the commissioning, do you feel?

Geoffrey Ibbott: I do think so. Absolutely. I think it was awkward for me when I was in that position and the people who followed me in that position to say that because it was clearly self-serving.

Stacy Wentworth: Oh, because you were charging for it.  

Geoffrey Ibbott: Right. But whenever I did have the opportunity, yes, I used my soapbox to encourage people to request it before they treated the first patient. So as the years went by, as new technologies came out, we developed new phantoms. As Matthew mentioned, motion management. That required a phantom with moving parts. It's simple, but it mimicked breathing motion. We developed phantoms for protons. One of the more recent things was phantoms for magnetic field environments. So MRI-LINACs. That's – I think speaking as objectively as I can from some distance now – everything Matthew said is correct. That is an extremely valuable program and it's done a great deal for the community.

One thing about IROC though, I do have to say the transition to IROC actually happened just after I left that position as director of RPC. I renewed the grant. I’d been encouraged to renew it for six years that time. Previously it had been shorter terms, but six years was great. That gave my successor, Dave Followill, a big cushion we thought. But shortly after he took over, the NCI told Dave that they wanted the RPC to be folded in with the group in Rhode Island. That group was called QARC at the time. They did clinical chart reviews for a number of clinical trials. For other groups that were going to do similar sorts of things but for imaging clinical trials as opposed to radiation therapy. So IROC stands for Imaging and Radiation Oncology Core. It was all six of those groups to be folded together into one grant and that was a tremendous challenge.

But, for a while there was a considerable amount of chaos because here were six groups all of which have their own grants being told to forget all that, you’re going together under one grant. I really have to credit Dave Followill for taking the leadership. He stepped in and took control and became essentially the PI for that larger grant that included all six groups. Now they all have their own funds in the grant and their own projects and divisions of responsibility. So they all have to put their own pieces into the grant, but it was Dave who pulled it together and submitted it. I am delighted that he was able to do that and that he was prepared to do that. It was the perfect stage of his career to do that. It gave me the opportunity to step away then, because I had been recruited to apply to chair the Physics Department at MD Anderson. That is a university department and it's about 220 people. I think we grew a little bit over the seven or eight years I was chair. There were 80 or 81 physicists at the time I stepped away from that. It's a huge department. Lots of trainees and technical staff are included in all those people and administrative staff for a department that size.

I know we're running short on time. I want to answer one of the other questions that I saw either from Paul or from Matthew. As is clear, I spent my career in academic departments and I would never regret that. There might be more money in other environments, but I enjoyed being in a training environment. Matthew said something about the number of publications that I'm very fortunate to have been a part of. That's largely because I've been involved with students throughout my career. And much of those publications are the work done by students who worked in my lab at one or other places. I've been again very fortunate to have had research funds to support a number of students. You'll see many of these publications on my CV have someone else as the first author. I'm either the second author as the student's adviser or the last author as the director of the lab. That's been just a wonderful opportunity for me and very enjoyable. So those students, many of whom I'm in contact with frequently today, were a delight of my career.

Stacy Wentworth: What do you think is the future of radiation physics? Is AI taking over, Doctor?

Geoffrey Ibbott: You know what? That is a very interesting question. Questions of that sort have been asked throughout decades and certainly all through my career. Is IMRT going to replace us all because – 

Stacy Wentworth: Hyperthermia.

Geoffrey Ibbott: Right. Exactly, yeah. It's never happened yet, but it does change our jobs. I think one of the most important things we can do as professionals in a rapidly changing field like this is adapt to it, learn how to adopt it and use it to our advantage. When you see fields fail I think is when people are resistant to a new technology or a new capability. It really does replace them or pushes them aside at least. I think the alternative is to embrace it, to make it yours, to become the leader in that and the resource and the expert in that. I see that happening. A number of my colleagues, Laurence Court at MD Anderson, has been doing wonderful things for a couple of decades now using what is now AI but early versions of that at first to improve treatment planning and to speed up treatment planning or do the routine tedious aspects, segmentation in particular. So he and a number of other people have done exactly that. They're embracing this tool. They're making it work to their advantage but all of our advantage as well. In the process they're becoming the leaders in a new field and the experts, the people we turn to. So no, I don't think it's going to replace us, but it certainly will change our lives, at least our professional lives.

Muthana (Matthew) Al-Ghazi:  Yeah. That's entirely correct. I dare say this is not my interview. It's yours, Geoff, and the attention is on you. But I'm old enough to remember when computers came around and people thought that there is going to be massive unemployment. Workers went on strike and so on and so forth. But really the long and short of it is that computers created jobs. They're just different jobs.

Geoffrey Ibbott: Right.

Muthana (Matthew) Al-Ghazi: Like you so rightly pointed out, we have to embrace change and use it to our advantage. What we do now in radiation treatment planning is not really what we did 20 years ago at all. The principles are the same in terms of dose and position, but the approach is quite modern. It's funny that you should mention that because I remember when I was in training my chief told me that 20 years earlier or 30 years earlier his chief was attending a meeting in Europe when chemotherapy was around and he had cabled to him sell cobalt machines, sell linear accelerator, cancer cure was found.   Well, where we are now, you know, 40 years later, and 
radiation therapy is working hand in hand with other modalities. So this symbiotic relationship changes and evolves with time, but it doesn't seem to abate any time soon.

Geoffrey Ibbott: It doesn't. You're right, Matthew, it leads us to new relationships in many cases.

Muthana (Matthew) Al-Ghazi: Right.

Geoffrey Ibbott: I mean look at things like intravascular brachytherapy. That was a big deal when I was AAPM president.

Stacy Wentworth: Oh, my gosh. Thank goodness.

Geoffrey Ibbott: One of the challenges that year was the cardiac surgeons came to us, to AAPM, to ask us to teach them enough physics so that they could do intravascular brachytherapy. So we struggled with it. This is something that should be done by radiation oncologists. We don't want to help this other group compete, but also they're probably going to do it anyway and we can't let them do it badly or dangerously.

So, I had what I was sure was going to be an extremely difficult conversation with the president of ASTRO then to explain that we had agreed to work with the cardiologists. Actually, the American College of Cardiology came to us. That we were going to work with them because we felt they were going to do it. And if they were going to do it, they had to do it safely.

The president of ASTRO at the time was Larry Kun, who was at St. Jude's. That conversation could have so easily turned out very different but, if you ever met Larry Kun, you know he was a gentle and gracious and thoughtful individual. So we had a very rational and reasonable conversation that led to a long friendship that lasted through our years at the ABR. We were trustees at the ABR at the same time until his death a few years ago.

As I say, that was a phone call that I was really dreading when I placed it, but that turned out far better than I ever thought. Another example of a new relationship that wouldn't have happened perhaps if it hadn't been for a new technology that we decided we had to make our own.

Muthana (Matthew) Al-Ghazi: That's very interesting that you should mention intravascular brachytherapy because at our institution the cardiologist came to us and he said, "look, I really don't know what to do", basically. So myself and the radiation oncologist were always called to assess the patient and treat them and so on. Between the three of us, we were able to deliver that service for the time that it lasted until it was replaced with drug-eluting stents some years later. And they are right. Our cardinal principle is to do no harm and the safety of the patient is really of paramount importance.

Geoffrey Ibbott: That's right.

Muthana (Matthew) Al-Ghazi: To be involved right there in the patient care process. Yes, we are entrusted with the research and the development and all the rest of it. Well, so are they. The same goes for clinical trials and quality assurance in clinical trials. It really influences the quality of the trial and the results that are anticipated. Thank you, Geoff, for championing all of these at IROC, at MD Anderson. I know you are involved with the IAEA and many other international organizations. So maybe you can, as some say, allude to this in your interview. Remember, this is about you.

Geoffrey Ibbott: Well, I will. Thank you. And as long as you guys are okay with the time.

Muthana (Matthew) Al-Ghazi: Yes.

Geoffrey Ibbott  I won't keep you much longer, but I could tell you a couple of things.

Stacy Wentworth: Yes.  And we have to get to the maple syrup too. 

Geoffrey Ibbott: All right. We'll get there very quickly. Again, I just feel that I've been extremely fortunate to have opportunities throughout my career. One of them came through the IAEA. I'll try to make this brief. While I was at Colorado I got a call from MD Anderson actually. The fellow who was the chair of radiation physics at the time and who built the RPC was a physicist called Bob Shalek. I've known Bob. It was just fortuitously I met him through Bill Hendee at a summer school, and so I knew him well enough to speak to him. They had a program at Anderson to bring people, bring trainee, young physicists to Houston to spend a year in the department there and get more training. He had a young physicist, a young woman from Thailand who was in the middle of one of these fellowships at Anderson and wasn't enjoying it, wasn't happy with the duties she was being given and wanted an opportunity to spend more time in the clinic. Bob couldn't give her that for whatever reasons. So he asked if he could essentially transfer her to Colorado and have her come and work with me.

So she came to Denver and we worked together for the last three months of her fellowship. Fortuitously, I broke my legs skiing as she was sort of on her way to Colorado. Virtually the entire three months she was there I was on crutches or walking on a walking cast. So she got to do far more of the routine physics duties than she ever expected to. My colleagues from there still remember me walking down the hall on my crutches and this tiny Asian woman walking behind me carrying the water phantom going to the treatment machine.

Well, ten years later her department in Thailand got funding from the IAEA to install new treatment equipment. At the time they had two cobalt units, but they were getting funds for a LINAC and a simulator and a treatment planning system. They also had funds to bring people there to help them learn to use it. So she gave the IAEA my name along with some other people. Harold Johns was one of the people who went there. But I ended up making three trips there for essentially a month each time to help them learn to use this new equipment. So I guess my trips were about a year apart and, as I say, for about a month each time. So that created another new relationship and as a result I visited Thailand. My wife has come with me on a number of occasions for a variety of reasons. So I still have many friends there.

One other international thing that I've been involved with is the International Electrotechnical Commission. We call that the IEC. It writes standards for electrical equipment, standards for manufacturing equipment. The IEC writes standards for everything from electric toothbrushes to bullet trains, and power plants, but also medical equipment.

I chair a working group and have done for a number of years now, the group that writes the standards for radiation therapy equipment. So the reason really that we have dual dosimetry systems on linear accelerators or the reason that gantry angle of zero is vertical pointing down and 90 degrees is rotating clockwise from there, those things are all dictated by IEC standards. Now the manufacturers are very much involved in writing these standards, but part of my role is to make sure there's a clinical input as well to that. So that's one other aspect of my international activities. Again, volunteer work, but I thoroughly enjoy it.

Two last things I'll finish up with. One is I mentioned already that I was a volunteer for the ABR for a number of years. Like anyone else who gets involved with the ABR, I started out writing questions for exams, and then was assigned to a committee to assemble those questions into an exam, and then ultimately became a trustee. After a couple of terms of being a trustee, that was when the ABR split the board of trustees into two and created a board of governors. So I was one of the first governors of the ABR. That ended. I completed the allowable number of terms including two terms on the governors in 2017 just before I retired in 2018.

In 2020 the ABR approached me about being one of four associate executive directors. This is a part-time staff position at the ABR. So that's what I've been doing since mid-2020. Similar position – Paul Wallner was the AED for radiation oncology for many years. So I'm the AED for medical physics now and work with the trustees, the medical physics trustees, and the volunteers on the committees, and with the staff in the office in Tucson. But I enjoy the job thoroughly. One reason I do is because I can do it from here in Vermont and just visit Tucson occasionally.

Muthana (Matthew) Al-Ghazi: A couple more last things that you might like to – if you recall, I sent a set of notes that sort of complement the chairman's briefing. One of them is if you were to look in a crystal ball about the future of medical physics and the other is more personal. How do you manage to keep your elegant English accent after so much time in the U.S.?

Geoffrey Ibbott: Matthew, yeah, I don't know – to your second question, when my parents were alive, my wife says she could always tell when I was on the phone with them even if they called and she didn't know who was calling because my accent got even stronger or more pronounced. So I suppose maybe the answer is it got refreshed regularly either when I was living with them or when I would see them or speak to them. But I suppose some things you just never lose completely too.

Muthana (Matthew) Al-Ghazi: That's wonderful. Where do we go to on the future of medical physics and what advice would you give to the young folks who are starting out?

Geoffrey Ibbott: I would remind people, as I do when I'm involved in teaching and I still am, that this is a field of amazing opportunities. As we've alluded to earlier, what's key for us is to embrace and take advantage of these opportunities. Not view them as an unwelcome challenge, but a very welcome opportunity and challenge. I think that's how we grow and how we maintain the strength and vitality of our profession. It's by embracing these new technologies, new structures, and new relationships. I think the field is very healthy. We do have a challenge today in the supply of new physicists mainly because we just don't have enough residency programs.

Muthana (Matthew) Al-Ghazi: Correct.

Geoffrey Ibbott: The people who have done the studies can support that with data that show that there are more vacancies than there are new physicists coming out of training. Everybody who is our age, Matthew, will say, yes, this is cyclical. We've seen this before. There are times when there is a flood of people with no jobs and times when it's like this now with lots of jobs that people can't fill. I suppose that's a phenomenon that we'll never get away from and we'll never be able to respond quite quickly enough as the demand for people changes. But I think we're going to see this demand continue for quite a while now because of the new technologies, the new modalities, AI, and other technologies related to AI machine learning, automated planning and so on. So either we rise and meet that challenge or somebody else is going to come in and take it. I think we need to be the ones to meet that challenge.

Muthana (Matthew) Al-Ghazi: Thank you so very much. It's been just a real, real pleasure and honor to talk to you, Geoff. 
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