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About ASTRO

James Purdy

By Theodore Phillips, MD, FASTRO and C. Clifton Ling, PhD, FASTRO

Dr. Phillips: Jim, why don’t you tell us where you were born and raised.

Dr. Purdy: I was born on July 16, 1941 in Tyler, Texas. That’s a town in east Texas, about a 100 miles east of Dallas. My family moved about a year and a half later to Orange, Texas, a small town on the Texas-Louisiana state line near the Gulf coast. When the war started, ship building jobs opened in Orange. Dad, who had good mechanic type skills, landed a job there. He worked in the shipyard building ships during the war effort, and later worked for DuPont for the rest of his life. So, I grew up entirely in Orange, Texas. As I said, Orange was a small town on the border of Louisiana, located in what’s called the “Golden Triangle”. It’s about 90 miles or so east of Houston, Texas. It was a great place to grow up. You could ride your bicycle anywhere. I could fish and hunt and do all the things young boys do. It really was a great place to grow up.

Dr. Phillips: Was it right on the coast?

Dr. Purdy: It wasn’t. It was on the border of Louisiana, right on the river - the Sabine River. And the Sabine River flows into the Gulf of Mexico and that’s why they built ships there. They could get them out to the Gulf pretty easily.

Dr. Phillips: Your father was working in a shipyard there?


Dr. Purdy: Yes, a shipyard right there in Orange, Texas. And then he moved on and worked for DuPont for the rest of his life after the war - a foreman in the petrochemical industry. It was a great place to grow up, because I could go down to the river and rent a little motorboat as a teenager and go out on the Sabine River and catch all kinds of fish and have lots of fun. I don’t think I would let my kids do that today, but it was a different time. It really gave you a spirit of adventure. Growing up in Texas, I had a 22 rifle and a 410 gauge shotgun. I went hunting with my Dad, with my buddies, or just by myself. I played little league baseball, and played a little intramural basketball and junior high football. As regards school, dad would bring home math problems from work. He was not college educated, but he recognized the value of education and he would bring home various math problems he encountered at work. He got me interested in math at a fairly young age, and I really give my dad a lot of credit for that; he kind of pushed me toward math and science.

Dr. Phillips: Was your mother a homemaker or did she work outside the home as well?

Dr. Purdy: She was a homemaker most of my childhood. But my dad died from a heart attack just after I graduated in 1959, about a month before my 18th birthday, and she had to go to work. I had been planning to go to college, the University of Texas, when Dad died of a heart attack. Looking back, I now realize that our diet was not real healthy. We ate a lot of fried foods and lots of eggs and things like that. Dad was in good physical shape, but working in the petrochemical industry was a physically demanding job, and we didn’t know as much about diet then. You can imagine those were stressful times after my Dad’s untimely death. I had three sisters. My oldest sister, Pat, was already married, Annabeth, my next oldest sister was in college studying to be a teacher, and I was scheduled to start college that September. I also had a younger sister, Nancy that was entering her sophomore year in high school. So, my mom had to go back to work. She had to figure out something in order to pay the bills. And I was really worried. I had no idea what she could do because she’d been a homemaker most of her adult life. She ended up starting a nursery school and was really good with little kids. She supported herself that way for many years before later becoming a very successful real estate agent in Houston, Texas. I was fortunate enough to get a National Defense loan and enrolled at the University of Texas (UT) in September 1959. But one of the things I now realize, as an 18 year old, I had no idea of what I wanted to do in life. I started out in engineering and made really good grades my first two semesters at UT. But I didn’t quite think engineering was right for me, it was a little bit, in a way, dull to me. The summer before my sophomore year, I got a job in the Texas oil fields near Tyler and made some money, enough to help me continue at UT, but I left engineering and started taking premed courses - biology, organic chemistry, and things like that. I made really good grades again, but, I soon realized I missed math. I was just too young at that time to know what I wanted to study for a profession. I began to struggle a little bit with my classes and within six months I decided I didn’t want to be a burden on my Mom or build up a lot of college debt with no clear career choice so I decided to join the Marine Corps. I enlisted and served just under three years in the Marines. That turned out to be a great decision and really gave me the maturity to come back to school and focus on my studies.

Dr. Phillips: Did you go into the Marines before you graduated?

Dr. Purdy: Yes I did. As I said, I didn’t really know what I wanted to do, but I knew I didn’t want to be a financial burden on my mom, and I didn’t want to build up a big debt. And so, I decided the Marine Corps was probably best for me. So I just enlisted - served in the infantry and rose to the rank of corporal. Turned out it was really fortunate for me because we were not at war or anything, but we underwent rigorous training that taught me a lot about self-discipline and teamwork. Also, I got to see the world – I trained at Camp Pendleton in California, and later was stationed in Okinawa, and visited the Philippines and Hong Kong. Before I was 21 years old, I was doing a lot of things like that. And it gives you the maturity when you come back to school so that you really focus. All in all, I really think enlisting in the Marine Corps was one of the most important decisions I made in my life.

Dr. Phillips: When you were stationed in those different places were you with the embassy guard?

Dr. Purdy: No, I was in the infantry and served on what was called the “floating battalion.” That’s what the Marines do. They train you for about 12 months over at Camp Pendleton, then they send you over to Okinawa for 13 months, and three of those months you’re on the floating battalion. I actually was on alert during the Cuban missile crisis. We didn’t know what was going on. Everyone was just on high alert.

Dr. Ling: In college you did not major in the physics, you were in engineering first and then premed.

Dr. Purdy: Yes, I did those two, but during my time in the Marine Corps, I got to do a lot of reading. When you’re stationed up in Okinawa there are not a whole lot of things you can do, so I read a lot. I’d go to the library and I’d check out books. I read Einstein, popular type books on relativity and science in general. As I said, I’d always been interested in science and math, but I also read lots of the classics in literature. I read a lot. When I was discharged from the Marine Corps, I had decided that I was going to go back to college and major in either law or physics. I came back home and enrolled (physics won out) in September 1964 at Lamar University in Beaumont, Texas, which was about 30 miles away from Orange. That’s where I got my undergraduate degree in physics, with a minor in mathematics in January 1967. I then got a teaching assistantship in physics at UT and started my graduate studies.

Dr. Ling: As I remember, you got your PhD in nuclear physics.


Dr. Purdy: That’s right, but that particular area of study wasn’t chosen immediately. In graduate school, while you try to find a mentor working in an area that you’re interested in pursuing, you take the basic core courses in physics, such as classical mechanics, electrodynamics, quantum mechanics, statistical mechanics and nuclear physics. Things went really well at UT as I had found my niche. Also, during my second or third semester, someone from MD Anderson came up to Austin and gave a lecture on a new school that was just getting underway in Houston called the University of Texas Graduate School of Biomedical Sciences (UTGSBS). This really piqued my interest. As I said, I had a strong engineering, premed and physics background, so this looked like a perfect fit for me. I looked into their requirements, and found that I needed a master’s degree to get in. I approached my nuclear physics professor, Dr. Emmett Hudspeth, about completing a master’s thesis on some work needed in his laboratory. I was able to complete my thesis on studies involving tritium-titanium targets. Dr. Hudspeth was working on trying to modify an old Van de Graaff accelerator to create a triton beam, and he needed to develop appropriate targets. So I got a master’s degree at UT-Austin working on these tritium sources and enrolled in the UTGSBS in Houston that July to begin work for my PhD. I received a research assistant fellowship under Dr. Robert Shalek in the department of medical physics at MD Anderson and completed two semesters, 24 hours. Helen Stone was actually one my classmates. I would help her with math, and she would help me with some of the biology and we became good friends. But, after completing the two semesters, I was a little concerned that this program was not the best fit for me. I believe it was one of the first multidiscipline programs in the country. It was a little bit of physics, biophysics, a little bit of anatomy and physiology. I actually completed an anatomy course complete with cadavers. I was a little worried though that I was getting a little bit of knowledge in lots of areas, but I wasn’t quite sure it was going deep enough in any one area. So I made a decision, and I didn’t know if that was going to be a good one. I talked to Dr. Shalek and after lots of thought, I decided that I was going to go back to UT-Austin and work with Dr. Hudspeth on the triton accelerator conversion and get my PhD in nuclear physics, which I did. I completed that work in a little over two years. But I now realize that the mixture of biology, biophysics and experimental nuclear physics was a really good background for my future as a medical physicist. You might remember, Clif, there weren’t a whole lot of jobs in nuclear physics in the early 1970’s. The US had landed a man on the moon in 1969 and after that NASA laid off a lot of physicists and engineers. I decided to take advantage of my earlier year at UTGSBS and applied back to MD Anderson for a postdoctoral training in medical physics. I thought my background might be really well suited for medical physics. I was accepted by Dr. Shalek’s group and did my postdoctoral training there at MD Anderson, mentored by Peter Almond, Walter Grant and Al Smith, just to mention a few key individuals in my training.

Dr. Phillips: I have a question for both of you now. In 2014, what do you think is the best degree for somebody who’s interested in medical physics? Would it be some general thing like medical physics or should it be a specialized area of high-energy physics? Would either of you like to comment?


Dr. Purdy: We’re certainly much further down the road with multidiscipline studies and I think going into today’s field, actually, in any field you go into, being able to work as a team and being able to communicate with members with different backgrounds, e.g. biologists, physicians, physicists, is very important. So we now have medical physics degree programs that are very strong. But I still think our field benefits from bringing in people that have training in traditional areas of physics, i.e. nuclear physics, high-energy physics, solid-state physics. I think those new ideas that come in from other fields make our field much stronger. And so I think, medical physics really benefits when you get scientists from different backgrounds to enter the field. Clif, maybe you want to expand on that a little bit.

Dr. Ling: I agree with you one hundred percent. And the danger that we face now, is that there is the degree program and then medical physics. And some of the departments that have these programs want to protect their graduates, and so that the matter of how do the physicists that are trained in high-energy physics, solid-state, find an entry path. And that’s a concern, I think for some of us.


Dr. Purdy: Yes, I agree. As you know, they’re making more and more requirements in order to sit for board certification. Physicists of my generation were fortunate. When you got a PhD in any area of physics, a year of post-doc in medical physics would allow you an entry into the field. Now if you got a PhD in say high-energy physics, a one-year post-doc would not do it. I think physicists today that have entered the field with just one year of training are not prepared for a clinical job. It’s too complicated a medicine for that, and that’s why the medical physics residencies have been a good thing. Today, physicists entering the field require more training.

Dr. Ling: But Jim, you had a one-year training and a post-doc at MD Anderson.


Dr. Purdy: Yes, but it was a different time. Also, I had completed the MD Anderson “short courses,” while I was still at UT-Austin after I’d obtained my PhD and was waiting for the June post-doc training to start. So I did those in addition to the post-doc training.

Dr. Ling: Right. And then you took your first job at Mallinckrodt (at Washington School of Medicine in St. Louis).


Dr. Purdy: I did. Things were just really exciting at that time. It’s interesting, Mallinckrodt had purchased a Varian Clinac 35, and that was the first Varian Clinac 35 in the United States. One was going in at Princess Margaret Hospital in Toronto, also. But, the only high energy linac operational in the U.S. was the Sagittaire at MD Anderson on which I received valuable training specific to high-energy photon and electron dosimetry. Mallinckrodt was looking for a medical physicist that would take on the project of acceptance testing and commissioning and bringing the Clinac 35 into clinical use. It was a wonderful opportunity for me because the field was moving from betatrons to this type linear accelerator approach. The Clinac 35 was a prototype actually - radiation oncologists and physicists working through NCI helped develop the specifications for an advanced unit like the Clinac 35. Ted may remember this.

Dr. Phillips: Definitely, to design a very high-energy accelerator. I remember that grant to Kaplan at Stanford.

Dr. Purdy: Yes, and Varian built the Clinic 35 based on that specification. And it was a great opportunity. Mallinckrodt (WUSTL) was my first job as a medical physicist and I ended up staying there 31 and a half years. It truly is a great institution and I am very proud to have been associated with it.

Dr. Ling: You had never commissioned a linac before, right?


Dr. Purdy: No, I had never commissioned a linac, but my post-doctoral training at MDA was ideal preparation for that task. This was not a research post-doc, but one that focused on clinical physics training. One of the strong things at MDA was the training offered regarding calibration of high-energy treatment machines, including the Betatron and the Sagittaire. It gave me a really strong background in calibration protocols, the use of dosimetry instrumentation and quality assurance. I also went out to a training school at Varian my first month at MIR and also spent some time at PMH with Alan Rawlinson who was commissioning their Clinac 35. The installation and acceptance testing of the Clinac 35 took just over a year. There was a lot development work done in the field, particularly regarding the electron beam applicators. It was a great opportunity and a real learning experience for me. And I was fortunate that Arnold Feldman was still at MIR when I arrived. Arnold was a tremendous support to me right after my post-doctoral training. I learned a lot about working in the clinic in that first year and the Clinac 35 project was a great experience for me.

Dr. Phillips: Who was the chair of physics then at Mallinckrodt?

Dr. Purdy: We were not a department at that time. George Oliver was chief of the physics section, Carlos Perez was chief of the clinical section, and Bill Powers was head of the division of radiation oncology, which was a part of the department of radiology. We were a division of radiation oncology at the Mallinckrodt Institute of Radiology at WUSTL. Ron Evans was the chairman of the department and director of MIR. George had been at MD Anderson also and had been recruited to MIR by Bill. And I think the experience I got at MDA working with people like Peter Almond, Walter Grant and Al Smith and others were probably the reason I was offered the Mallinckrodt job. And Carlos, as you know, had also trained at MD Anderson. So there was a strong influence of MD Anderson on my recruitment. At the time the really two big programs in radiation oncology were MD Anderson and Memorial Sloan-Kettering.

Dr. Phillips: They were the only cancer centers then.


Dr. Purdy: Yes, they were big cancer centers and provided great training opportunity. I didn’t realize it then, I mean being trained at MDA, seeing Gilbert Fletcher who was the head of radiation oncology back at Anderson. I’d go to those morning conferences and see how he interacted with people. As you remember, he was pretty tough; he really got things done.

Dr. Phillips: I went to some of those conferences. It was wonderful.

Dr. Purdy: Yes it was. It was great.

Dr. Phillips: At Mallinckrodt, was the physics of imaging separate from the therapy physics?

Dr. Purdy: Yes. Michel Ter-Pogossian was head of imaging physics and was really focusing on the development of a PET scanner. When you look back on it, it was just wonderful that such exciting things were happening at Mallinckrodt. We had the PET scanner being developed. He had a young associate there, Mike Phelps helping him, but I think Ter-Pogossian really drove the development of PET imaging. And Bill Powers truly wanted to get Mallinckrodt radiation therapy moving forward. He would go to many national/international meetings and he’d come back and be excited and would try very hard to motivate the faculty. I still remember my first couple of years, I think it was about my second year there, he threw down on my desk the 1965 Acta Radiological Supplement publication on conformation therapy by Dr. Takahashi, and said, “Purdy, this is what I want to do.” He saw the need for multileaf collimators and really pushed for conformal therapy before many realized the advantages. He was already thinking about that technology back in early 1971-72. He really was pursuing advanced technologies to improve the planning and delivery of radiation therapy. He pushed the development of Cerrobend blocks as an early step to conformal radiation therapy. And when we got the first Clinac 35 going in the U.S., I think that set the stage for Mallinckrodt to really be a major contributor in the field. It sort of put the drive in me, to be an innovator, to try to not wait till somebody else developed things, but to try to move the field. I mean radiation therapy seemed stuck back then in the cobalt and Betatron era and we needed to move forward. And the development of linear accelerators, Cerrobend block field shaping and treatment planning was very important. And Bill really pushed us.

Dr. Phillips: I know Mallinckrodt developed a lot and I think you were part of the development team that came up with Cerrobend blocks and that was a revolutionary invention for all of us.


Dr. Purdy: Cerrobend blocking was already in place when I joined MIR, but I helped refine it, emphasizing quality assurance and better instrumentation. I think Bill understood the importance of target volume specification and shielding normal tissue. And hand blocks could only do so much - radiation therapy was just stuck in that era. Bill really pushed the concept of making a practical system that could make field-shaping blocks efficiently. I think that was a huge thing. If you remember at that time, too, simulators were just coming into use. Radiation therapy in the late 60s early 70s had only a few institutions that had installed dedicated simulators. MIR had just gotten one - so radiation therapy was really going through a huge transition in the early ‘70s. Bill actually was on the president’s first advisory council on cancer. I think the early 70s was such an exciting time to be in this field. It was sort of like being on the ground floor – even though much development had been done earlier with the development of cobalt units and betatrons, the 70s were an exciting time to enter the field with the advent of the linear accelerator and dedicated treatment planning computers.

Dr. Phillips: Didn’t you at Mallinckrodt have the first or one of the first microcomputers dedicated to treatment planning? I sort of remember getting programs from you back then.


Dr. Purdy: Absolutely. Washington University played a huge role in the development of treatment planning computers. The PC-12 evolved from the work done at Wash U’s Biomedical Computer Lab (BCL). They developed the “program console.” And where others had used mainframe computers and bigger computers, this was really the birth of the small dedicated treatment planning computer - it really did get developed at Mallinckrodt through the BCL in collaboration with the radiation oncology division.

Dr. Ling: Jim, about the Clinac 35, you probably remember, I visited you at Mallinckrodt.

Dr. Purdy: Yes.

Dr. Ling: You were almost going back to MD Anderson at the time.

Dr. Purdy: Well, that’s exactly right. You bring up some interesting times. We got the Clinac 35 into operation and things were going pretty well and it was a good time. But Bill Powers had an interesting way of interacting with his department chairmen, Ron Evans. During my first two years at MIR, Bill resigned three or four times, but the resignations were never accepted. That was his way to get his way in departmental matters. MIR was one of the first in the country, if not the first, to get a CT scanner. Bill immediately wanted one down in radiation therapy - and Ron Evans said that’s a diagnostic machine and not ready for implementation down in the radiation therapy space. Anyway, we didn’t get it and Bill resigned. And this time Ron accepted his resignation. So, we didn’t have a chairman. Carlos was actually being recruited by many places to head their radiation oncology program, and I thought he was going to leave also. Things were sort of falling apart at Mallinckrodt. Bill had left, George Oliver was about to leave, and I thought Carlos was going to leave. I had received offers from several institutions, including Johns Hopkins and MD Anderson. But shortly thereafter, Carlos was named the new division director, and Carlos and I had worked well in the clinic together. I was the chief clinical physicist then. So I met with Carlos and agreed to stay. And I stayed and worked with Carlos for the next 30 or so years. In 1976, actually only three and half years after I started at MIR, Carlos offered me the job as head of the physics section. And from there I recruited some great physics faculty and built the MIR radiation therapy physics section.

Dr. Phillips: Could you talk a little about the people you recruited and the people you’ve trained? I know a lot of outstanding physicists have come out of Mallinckrodt and are medical physics leaders throughout the country now.

Dr. Purdy: Yes, one of the things I realized, when I became head of the physics section, was that we needed to transition from just being a good clinical physics program to a more academic one. Clinical physics was obviously one of our strong points, but we needed to do more in research and development and in our physics training programs. And so, I had to start recruiting the type of physics faculty that could help us transition into a strong academic program. One of my first recruits was Satish Prasad, who helped us implement a three-dimensional dose calculation algorithm. When Satish was recruited away, I was fortunate to recruit John Wong from PMH. John took over the development of our advanced dose calculation work and worked with me for over 10 years. We had lots of fun developing the MIR 3-D planning system. John is now head of radiation oncology physics at Johns Hopkins. I also was able to recruit individuals like Marty Weinhous, who provided a great deal of computer technology expertise for the project; Marty later served as president of AAPM. We also had graduate students and post-docs like Cedric Yu and Dee Yan, who helped in our 3-D planning system development and went on to become heads of department radiation oncology physics programs. I also recruited Jeff Williamson, who really helped build our brachytherapy physics program, and also became head of a radiation oncology physics program. I was also very fortunate to have strong master’s degree clinical physicists - people like Russ Gerber, Eric Klein and Sasa Mutic (by the way, both Eric and Sasa continued their graduate studies and earned doctorates and are now co-division heads of radiation oncology physics at Wash U). You can see that I have been fortunate to have had such good individuals to work with me over the years. So we built a very strong physics group. You know, I didn’t even mention several of the people on the computer side of our 3-D planning effort - such as Bill Harms, Walter Bosch and John Matthews. Those three individuals really contributed and also helped me with establishing the 3D QA Center for clinical trials.

Dr. Phillips: The guy who’s chief at UCLA was one of your people, wasn’t he?


Dr. Purdy: Dan Low. Yes, Dan did his post-doc at MD Anderson, and I recruited him in 1991 and he worked with me for over 10 years. He really helped build our IMRT program. He took over my position when I left for UC Davis in 2004. He’s now head of radiation oncology physics at UCLA. I am very proud of what Dan has been able to accomplish. I also recruited Joe Deasy in 1999. We worked several years together and he is now head of medical physics at Sloan Kettering. So I’ve got a lot of chiefs out there whose career development I am extremely proud of. I think what I tried to instill in all of them during their time at Wash U is the importance of being strong in all three areas of academic physics – clinical physics, training and education, and innovation/research. They’ve got to keep innovating. They’ve got to keep working to help change and advance cancer therapy, and all of them are trying very hard to do just that.

I would be remiss if I also didn’t mention some of the physician residents that I helped train that contributed greatly to our 3D conformal therapy program, particularly, Jeff Michalski, Mary Lee Graham and Cliff Chao – they worked long and hard using 3D planning technology that was pretty cumbersome compared to today’s technology.

Dr. Phillips: Clif, do you have a question?

Dr. Ling: Yeah, so can you perhaps tell us who are the people who influenced you the most from the point of view of your medical physics and radiation oncology and any other discipline that you care to mention?


Dr. Purdy: Yes. I’d like to start with my physics professor at Lamar University, Roy Biser, where I received my B.Sc. His program really provided me a strong foundation in physics - I had great, great undergraduate teaching in physics. Then Emmett Hudspeth was a great physics professor at the University of Texas. In medical physics, clearly the one that most influenced my career is Dr. Bob Shalek at MD Anderson. I saw the interaction of Drs. Shalek and Fletcher and they taught me that radiation oncology really is a team effort. The physicist and the physician have got to be a team. They’ve got to work hard together and they’ve got to communicate. And I’ve sort of modeled my career on that kind of approach, of realizing that it’s not just about medical physics, it’s about radiation oncology. And so, it’s working closely with physician colleagues. And, of course, I have to give credit to Carlos Perez. Carlos was a great leader. To have a job over most of my career working for somebody like Carlos Perez was amazing. Carlos did not micromanage me at all. He said, “Jim, just do good – help me build this program.” And then, he left me alone. He’d give me encouragement at times. Development of treatment planning was one. He really encouraged me to pursue the Mallinckrodt tradition of trying to advance treatment planning. I really have to give Carlos a lot of credit, because he strongly supported the biology group. He supported physics. He supported the clinic. He wanted that kind of program. I also need to mention Bill Powers again. Bill would have been a harder person for me to work with long-time because Bill was always moving in lots of different directions, all at the same time. Carlos was more focused, but I have to give Bill a lot of credit - he really pushed us to be innovative, to pursue making a difference, so I enjoyed that aspect of his influence on my career. Physics-wise, Dr. Suntharalingam was very important to me early on in my career. He strongly promoted the professional aspect of medical physics - certification, clinical physics competency. If you’re working in the clinic, focus on the clinic - make sure you have adequate QA. So I give Suntha a lot of credit there. And I want to acknowledge several other MD Anderson mentors that helped me during my training, including Peter Almond, Walter Grant and Al Smith; they were great. And, you know, Clif, over the years, just interacting with people like you and Michael Goitein, Radhe Mohan, Ken Hogstrom, Dick Fraass, Alan Lichter, Bahman Emami, Julian Rosenman, Mary Austin-Seymour, Ira Kalet – all those involved in the NCI 3D research contracts - those really were wonderful times. And I need to mention your previous chair, John Laughlin – he was also involved in the 3D photon contract. All the groups had some really, really good people working on advancing 3D treatment planning - I really enjoyed the times spent in those NCI research contracts.

Dr. Ling: Jim, you had very good working relationship with the vendors. Can you describe a little bit of that, those interactions and how things have changed?


Dr. Purdy: I think that came from that first experience with the Clinac 35. Varian had built the Clinac 4, and that machine was very successful and was going into many clinics. The Clinic 35 was much more complicated and was truly partly engineered in the field. I still remember working with engineers like Varian’s Ray McIntyre, where he actually took the flattening filter out of the treatment head and filed it right there to try to meet the agreed-on specification for field flatness. I worked very closely with those Varian engineers and installation technicians. I learned the importance of being able to communicate with the vendor, because these machines were not totally ready without problems. For example, the first electron applicator used lead inserts and weighed over 100 pounds for the small field; two people were required to connect it to the treatment head. Thus, I recognized early-on that vendors were a key partner in advancing radiation oncology. And I got to meet individuals at that time that later would be leaders of the industry in this field. Dick Levy actually was the salesperson that sold the Clinac 35 to Mallinckrodt. And I think Varian, as a company, realized the importance of developing strong relationships with institutions willing to work closely with their scientists and engineers with products that weren’t totally ready for large scale implementation. I’m going to go back to the time just before the Clinac 35 finally got accepted. Powers actually wanted to pull the Clinac 35 out and get a refund as the electron applicators were a disaster. He was really upset, but I showed him the data, documenting all the advantages the machine would have over our Betatron and Clinac 4. I convinced Bill, that there was a lot more that machine could do and he agreed. We accepted it, signed the contract, paid for the machine, and the rest was history. We kept the machine in operation over 10 years. And Varian began putting together various user group meetings and think-tank-type groups, and I was part of that. And Ted, you were on some of those.

Dr. Phillips: I was at Varian RT2000. Yes, I was on that until we bought all Siemens equipment, and that was the end of that.


Dr. Purdy: Even before RT2000, there was the so-called “RT Accessory Group” that provided ideas and feedback on accessories for clinical use with linacs. I believe Varian was very wise to bring in different clinic groups that provided input to them in design of their products. Also over the years, I worked with CMS in the same way. Rather than just buying a product, I thought it was much more important to interact with the company and try to influence their design. And I think companies in past years were able to do that. I think now it’s much harder, because of all the legal ramifications. Regulations are such that if your hospital purchases a piece of equipment, your involvement in those kinds of user think-tank groups, might pose a conflict of interest issue. And so, it is more complicated today. So Clif, I think we all grew up in a different era where there was much more of an opportunity for physicists and physicians to be able to interact with vendors and try to influence the design and help them build a better product.

Dr. Phillips: Now the 35 died out. Why do you think that it was unsuccessful in the long run?


Dr. Purdy: I think because it was never able to be manufactured in mass production. Each Clinac 35 was fairly unique. The Clinac 35 at PMH was a different machine than the one that came to MIR. Varian kept learning better ways of how to build these machines cost effectively. They built another one that went into Roswell Park, then MGH got one, and the last one went to an institution in Japan. Varian learned how to mass-produce a dual energy photon and electron linac and then used that knowledge to build the Clinac 18. They learned an awful lot on the Clinac 35 product. We also learned it had a 25-MV X-ray beam. When we measured the depth dose, we found that the beam was not as penetrating as the 25-MV beam from the Betatron. And that was because Varian didn’t quite understand when they built it, the impact of the flattening filter on the percent depth dose; it was made of lead and tungsten rather than aluminum, which was used on the Betatron. And so, we learned that with improved flattening filter design, you didn’t have to have that high of an energy photon beam. The Clinac 35 was also going to be used as a research machine to produce radioisotopes in the evening when not used for therapy. That never really panned out because it wasn’t possible, from a maintenance point of view, to keep that machine running 24 hours a day.

Dr. Phillips: Was it concluded that 25 was too high because of pair production or some other reason,that they dropped back to 18?


Dr. Purdy: You bring up a good point. You could get a depth dose of 80% at 10 cm without having to go to 25-MV, and if you did that with a lower energy beam, you would cut down on the neutron production. The neutron production, as you know, starts at around 10-MV and goes on up. But one of the things the higher energy did, and we did some studies on this, you could produce oxygen-15 when you irradiated with the higher energies. Oxygen-15 decays quickly and the positron and electron production allows one to image the dose distribution. So we experimented a little bit with that, but it never really became practical, quite frankly.

Dr. Phillips: Well, was there also a realization that electrons much above 20 MeV weren’t very useful?


Dr. Purdy: Well, when you got to the higher energies, to get a reasonably flat field, you had to have a thicker scattering-foil, which resulted in a less abrupt depth-dose fall-off and a higher bremsstrahlung tail. Now, with better technology such a multi-scattering foils and better designed electron applicators, we have improved EB depth-dose characteristics. But I wouldn’t give up on high-energy electrons beams. You may see much higher energy electron beams come back into use some day as technology is made more practical.

Dr. Phillips: Okay. Well, now could we go maybe to another topic, and that is your relationship with RTOG and the QA ATC Centers that you set up with RTOG.


Dr. Purdy: Well, I was involved with RTOG early on just because Mallinckrodt was a strong participant in clinical trials. I got a lot of experience with clinical trials from Simon Kramer and Carlos, both very dedicated to clinical trials. From the beginning of my career, Carlos encouraged me to go to RTOG meetings, and I did. And I got very involved with the physics committee there and worked with them in developing QA procedures. The 3D QA came about because - really we first need to go back and talk a little more about the NCI 3D research contracts. We had participated in the NCI photon, electron, and RTP tools contracts. So our 3D planning technology had been developed as part of those research contracts. The RTOG chair, Dr. Jim Cox, was aware that we had developed a 3D planning system that could receive some 3D treatment planning digital data as required by the research contracts. So Jim Cox telephoned me one day and said, “Jim could you put together a 3D QA Center?” And I said, “I think so.” I received an RTOG equipment grant which funded the development of a QA system that could receive digital data from participating institutions. We had to expand the data exchange format used in the contracts to meet the needs of protocols requiring 3D treatment planning, 94-06. We called it the “RTOG Data Exchange.” Now we had to have multiple workshops with institutions and vendors to show them how to implement the RTOG data exchange. We went through about seven of those. We were in great position when the NCI put out an RFP for a dose escalation study for prostate cancer (later became RTOG 9406). We submitted a grant to the NCI to be the QA Center for that particular study. We got the grant and were called the RTOG 3D QA Center. And we received all the digital data for the 9406 study. We had recognized the importance of review of target volumes drawn rather than just reviewing field apertures. So we received the contoured CT digital data – the GTV, CTV, and PTV, and we could review it on computer workstations and if there were problems we’d get back to the treating physician. And I truly believe that study changed clinical trials QA, I think forever.

Dr. Phillips: Those tools allowed you to do that subsequent paper on the penile bulb, for example.


Dr. Purdy: That’s right. That archived data allowed UCSF’s Dr. Mack Roach to remotely access and view the data and contour new volumes using dose-volume histogram analysis along with the clinical trial results. He was able to complete a secondary analysis study on the dose to the penile bulb. So that was a good example of how useful such archived treatment planning data can be. Now I think most studies are being done digitally where the data is being accumulated and undergoes QA review using remote review tools. And I think this is where radiation therapy will continue to show advances in the future by having access to even more archived digital data.

Dr. Phillips: You mentioned the photon and the tools contracts. I remember them as extremely important in developing the future of 3D-CRT and IMRT. Who originated them? Who thought up the idea of having these contracts?

Dr. Purdy: I think the NCI 3D research contracts RFPs were put together by Dr. Al Smith. There was interest at that time at NCI to fund what was called “Collaborative Working Groups (CWGs).” I give Al Smith a lot of credit for pushing the CWG concept. I think it really helped advance conformal therapy. The 3D Photon Planning CWG consisted of Memorial Sloan Kettering, University of Pennsylvania, MGH and Wash U. The 3D Electron Planning CWG consisted of MD Anderson, University of Michigan and Wash U. The RTP Tools CWG consisted of Washington University in Seattle, University of North Carolina and Wash U. And I need to back up because the first NCI research contract was the Particle Planning contract which we were not part of. Ted, I think that your group may have been involved in that contract.

Dr. Phillips: Yes, we were part of that.


Dr. Purdy: That was the first planning research contract, and that set the stage for those still to come. The CWG concept seemed like a good idea. And Al then put together that same concept of having say three or four institutions get funded on a singular and so-called deliverable type project where you had to meet treatment planning deliverables requirements. I think Al Smith may have been also the one for the particle project. But the photon project, it was clearly Al. No one really had a functioning 3D planning system when we all started the project. Sloan Kettering didn’t, we didn’t, Penn didn’t, and even MGH didn’t have a clinical one for photons.

Dr. Phillips: They had them in the particle program at Berkley and MGH for photons. Is that correct, Clif?

Dr. Ling: MGH had one for protons, but not for photons.


Dr. Purdy: Yes. When you use photons, it’s not a single beam or even two beams. It’s multiple beams. All of us had to develop a 3D planning system. Sloan Kettering developed their system which generated a picture of a 3D display that was actually used as a cover for the National Geographic magazine. And we developed the MIR 3D system, and MGH was able to expand their system to accommodate photon beams. A lot of issues were studied. We had a full issue of the Red Journal devoted to results learned from the photon contract. And I really do believe that was one of the more important things I was involved with over the course of my career. Also, during the later part of the 1980s and early 90’s, I participated in ICRU writing groups that addressed target volume specification. Several U.S. radiation oncologists and medical physicists were involved including me, Gerry Hanks, and Suntharalingam, and of course representatives from Europe and Asia. We expanded a lot of the ideas that came out of that NCI Photon Planning contract, like the mobile target volume (MTV). It wasn’t quite the concept we wanted because it was not tied to the coordinate system of the treatment machine, but instead to the patient. So we came up with the concept of GTV, CTV, and PTV, with GTV and CTV tied to the patient’s coordinate system, while PTV is a fixed structure, an imaginary eggshell-like structure, fixed to the coordinates of the treatment machine.

Dr. Phillips: You were instrumental in ICRU 50, 62, 71 and 83.


Dr. Purdy: I was a member of all of those writing groups and I really enjoyed it. That was one of the really fun things I did in my career. I enjoyed the interactions with the people – the debates and interactions we had on lots of interesting concepts. We were criticized pretty heavily when ICRU 50 first came out. Several individuals thought the PTV concept really didn’t make sense, and we also didn’t address movement of the organs of risk. So we got criticized. But I think ICRU 50 really provided a roadmap of how to do 3D planning; defining a GTV, then expanding it for microscopic disease (CTV), and then putting a margin around that to account all of the uncertainties including motion and such. So I’m pretty proud of that effort, quite frankly.

Dr. Phillips: I think it has led to, probably in some peoples’ hands, overexpansion of the PTV because a lot of people have adopted 1 cm, 2 cm, and all of it is sometimes ridiculous because it expanded in areas where tumor can’t exist.

Dr. Purdy: Agreed. We then, though, have the other problem with the era of IMRT. The CTV is the big problem. It’s not visible. Bringing in a PTV margin around a CTV margin becomes a real struggle for physicians. But I agree with you. PTV is not just a simple addition of margins. You’ve got to use judgment, quite frankly, and you need to be careful. But that dilemma has spurred the image guidance era. We’re making a lot of progress. Target volume specification is important and now we have to have better imaging. And I think Clif has also contributed to this area with his concept of “biological target volume (BTV).” We can move forward and better understand hypoxia and other biological factors, and maybe our ability to “paint dose” around BTV’s will improve radiation therapy results. I really believe target volume specification is the most important issue.

Dr. Phillips: I’ve just been running the GI service here at Tucson for two months, filling in for somebody. But I’m impressed that using daily cone-beam CTs, the images in the Varian Cone-Beam CT system are just not good enough. You can’t see the detailed structures, except for bones, very well in their Cone-Beam CT. So that’s going to need a lot of work. Is that an inherent limitation of cone-beam or is that they haven’t worked out the artifacts well enough?

Dr. Purdy: Online CT imaging will continue to be developed and improved, but I don’t think that’s the total answer. If you look at cone-beam CT today compared to when it originally came out, it’s much better. Is it adequate? I don’t think so totally. That’s why I think the new ViewRay product, the MRI-guided treatment delivery system, is going to have significant impact for certain disease sites where imaging soft tissue is more important than bony structure. So imaging in radiation oncology, – we’ve always had some form of imaging to help improve the delivery dose. So I think you’re going to see radiation therapy machines continue to integrate imaging technology into their systems. The drawback is cost, obviously, but I think people will innovate and be able to keep cost under control. But you’re going to need to continue to improve imaging in the treatment arena. I think eventually you’ll have a CT/MRI/PET-type system in a radiation therapy room.

Dr. Ling: Jim, you have contributed so much scientifically, clinically, and also as a leader of the professional society. Can you perhaps look back and say how AAPM and ASTRO have evolved? Are there things that we should be careful about in such evolution because you can now sit back and say, well, this is the past, that was the present, and now what is the future. Can you comment on these professional societies and your vision for them?


Dr. Purdy: As you know, AAPM formed backed in the 1950s and there has always been a debate - is this a professional society or it is it a scientific society? That’s been an ongoing discussion. When I came into the field in the early 70’s, there was a pretty strong discussion going on that perhaps there should be an organizational recognition between scientists and engineers working in research and industry and those working in the clinic. Such discussions led to the formation of the American College of Medical Physics (ACMP) which was formed to address clinical physics practice, board certification, licensure, and other professional type issues. The hope was that the AAPM would become more the scientific organization and the ACMP would focus on those issues pertinent to the practicing clinical physicists. A similar organizational structure has been implemented for medical physicists in Canada. I actually think that is what we should have done. It turned out it didn’t continue to evolve that way. It became more political – the AAPM continued to represent both scientific and professional members and the ACMP no longer independently exists. It has now been absorbed within the AAPM. So my belief is that the Canadians have done it right. They have the Canadian Organization of Medical Physics (COMP) and the Canadian College of Medical Physics (CCMP), addressing clinical physics practice issue. And I still think that’s probably a better way because professional issues can get somewhat political. The ACMP/AAPM split led to over a decade of struggles with the American Board of Medical Physics and the American Board of Radiology. I supported both of those boards. I felt the American Board of Radiology has done a tremendous job in its efforts, but I felt the American Board of Medical Physics was a board for physicists and could have coexisted. Certification was the important issue, not which board did the certification. And now the AAPM is still a professional society, a scientific society. It’s also trying to be a voice for both imaging and radiation therapy, and that’s a lot to ask of a society the size of AAPM. I would like to see AAPM become much more focused in its effort. I think quality assurance efforts at AAPM have been very slow in developing protocols and practice guidelines. I think AAPM has got to become much more efficient and use new communication technologies to allow protocols and practice guidelines to be developed and kept up-to-date. I’ve seen ASTRO evolve from a true scientific organization to both a scientific and professional society. During a large part of my career, the ACR handled radiation oncology’s professional matters. I guess that’s a natural evolution of these societies. But I think it gets muddy when you see both professional and science matters having to be addressed by the same society.

Dr. Phillips: So the ABMP is gone, is that correct?


Dr. Purdy: Yes, in most areas of medical physics, the American Board of Medical Physics is not defunct. However, it still certifies in areas such as MRI and in medical health physics. The ABMP certifications in radiation therapy physics and diagnostic imaging physics are recognized by the ABR through a “letter of recognition.” But now, as you know, Maintenance of Certification is in place and individuals have to meet certain continuing education requirements to maintain their certification. In retrospect, we probably didn’t do as good a job as we should have in getting the ABMP and ABR to work together harmoniously. I don’t see why we had the conflicts, and it caused a lot of issues within the medical physics and physician communities. But hopefully going forward, we’re going to recognize that certification is the important issue. We need to have physicists in a clinic be board certified, and I’d like to see physicists take a larger responsibility for the board certification of medical physics. Things seem to be working pretty well now, I think, in regard to board certification. However, I am concerned regarding the road to get to that certification. I think what we’re seeing is the education and training needed may deter physicists from other fields such as nuclear, high-energy, or solid-state physicists from enter into medical physics. I think in the long run that’s going to be detrimental to medical physics and to radiation oncology.

Dr. Phillips: What do you think about the blend of masters’ levels and PhD level people that are coming in? As I understand it, you can go into a physics residency with either degree. Is that correct?

Dr. Purdy: That is correct. Some programs only accept PhDs. Others accept both. I see it as just a natural evolution of the field. When I came into the field, there were many B.Sc. degree physicists – Peter Wootton, head physicist at the University of Washington held only a bachelor’s degree. But as time went on, education requirements were raised, first it was a master’s degree and then PhDs. We’ll continue to see education and degree requirements evolve. I think some individuals are talking about a degree called Doctor of Medical Physics – Clif, help me out on this. You may know more about this.

Dr. Ling: Yes, some programs offer that now.

Dr. Purdy: Yes. So I think you’re going to continue to see changes evolve over the next several decades. I think the PhD will be the requirement for a research academic institution. And that’s where a research physicist is trained. If you’re going to get a PhD, that’s primarily a research degree. I’m not necessarily thinking you have to be a PhD to be a clinical physicist.

Dr. Phillips: Well, the master’s level plus the residency is good for the people out in private practice then you would think.

Dr. Purdy: I believe that would be a strong clinical physicist that has a master’s degree and a residency. I don’t think individuals awarded a master’s degree, or for that matter a PhD, are ready to go to work in a clinic right away. That’s not strong enough. I think they should complete residency training in clinical physics first.

Dr. Phillips: Let’s go off on a different track now. Can you tell us a little bit about your family?

Dr. Purdy: I really give my wife, Marilyn, lots of credit for what I was able to accomplish over the course of my career. Marilyn came to nearly every ASTRO and AAPM annual meeting with me until I retired in 2011. She was just a huge support to me in my career. I met Marilyn at the University of Texas in 1961, just before I joined the Marine Corps. I was actually her brother’s roommate at UT and she came to visit him. That turned out to be the luckiest event in my life. We had a few dates before I left for the Marines and reconnected just before I was discharged. We married a few months later, January 29, 1965, when I was enrolled at Lamar University. Marilyn pretty much supported us while I completed my bachelor’s degree in January 1967. I immediately entered graduate school at UT-Austin that January, and a few months later, our first daughter Katherine was born. Our second daughter, Laura was also born in Austin in 1968. Upon completing my medical physics training, we moved to St. Louis, and that’s where our children grew up. Our family was very fortunate as we got to travel to many other countries and experience many different cultures. Travel is really one of the great perks of an academic medical physics career. You get to visit many countries, and you quickly realize there are so many smart people all over and you make wonderful friends all over world. Marilyn really embraced travel. She’s a true adventurer at heart. I think we’ve seen over 50 countries together. Our daughters completed their bachelors’ degree – Laura from Indiana University and Katherine from Washington University. Both decided to move to California to pursue graduate studies in film making. Both moved to Los Angeles upon completing their masters’ degrees where they continue to reside. In 2002, Laura married a young man from Bogota, Columbia, Juan Devis, and we had our first grandchild, Eva Luna, born in June, 2003. It wasn’t long before Marilyn said that we needed to be closer to our daughters and our granddaughter. So in 2004, I left Washington University – Carlos was retiring as chair and Dr. Vijayakumar, the chair of radiation oncology at UC Davis, had been trying to recruit me for over a year to help him build the academic program there. With Marilyn’s insistence, we moved out here to California. Our second grandchild, Simon, was born May, 2006. We are now able to see both of them and our daughters about every 2 or 3 months. They either come up here or we go down to Los Angeles. We really like Davis and will probably live out our retirement here. It’s been just a wonderful time out here and to be able to see all our family much more often than if we had stayed in St. Louis.

Dr. Ling: Jim, if you have to name one thing that you are most proud of, what would that be?

Dr. Purdy: Clif, that’s a hard question to answer, because I don’t think it’s just one thing. I’m proud of my efforts in quality assurance, which includes efforts in target volume specification, linac QA, clinical trial QA, etc. My early training, starting with Drs. Shalek and Fletcher and continuing with Bill Powers and Carlos Perez, instilled this emphasis on QA into me. So I think my career has been devoted to trying to ensure patient safety and improve quality of radiation therapy. So I am proud, but it is not just one thing, as you can see. Whether it’s helping physicians define more accurate target volume or working with linacs – making sure things are operating correctly and doing it efficiently and effectively. All are things that I have spent a lot of effort on. So I think that’s probably what I’ll be remembered most for - my efforts in quality assurance. I’m also proud of the physics team that I was able to put together over the years. I was very fortunate to have recruited or helped train individuals that allowed Washington University to contribute so much to the field over these last three decades. Many of them now are heads of radiation oncology physics programs throughout the country. So I’m very proud of them. I also want to take the time to acknowledge the many dedicated individuals I interacted with over my career, the physicians, the physicists and the biologists. I mentioned some by name earlier and I realize we don’t have time now to name all the others. I’ve seen radiation therapy grow from the early linac technology efforts, computer treatment planning, hypothermia, conformal therapy, image-guided therapy, etc. Our field continues to grow, so I’m excited about radiation oncology. It seems to change itself almost every 10 or 15 years. I’m very optimistic about the future of the field. I know a lot of people think that this is the age of biology and that medical physics and technology likely will not contribute significantly in the future. All I say is that I do hope we find a cure for all the various types of cancer as soon as possible, but I still think physics can make a significant contribution. There’s a huge effort still needed. I truly believe that we will continue to improve technology and lower costs, that we will make high quality radiation therapy available to cancer patients around the world. Medical physics is still a great field to go into.

Dr. Phillips: It’s getting more important. As the drugs get better and kill a couple of logs of cells, then local control of the residual gross tumor gets more and more important, not less important. And I think your legacy at Mallinckrodt is still paying off. They are the first place to get a ViewRay machine and a dedicated proton room.

Dr. Purdy: I do think the legacy of Mallinckrodt radiation oncology is innovation. The Clinac 35 sort of set the foundation for that and Carlos and I did continue it. We were one of the early developers of 3D conformal therapy, and one of the early adopters of IMRT, installing a Nomos Peacock IMRT device, not the first, but one of the first. WUSTL is the first institution with the MEVION S250, the new single gantry proton machine. And the ViewRay, the new MRI guided treatment machine should go clinical early this year. By the way, ViewRay was invented by one of our medical physics trainees, Dr. Jim Dempsey. Again, just another example of innovation - and there’ll be others. I think that’s what’s absolutely needed. Institutions need to embrace innovation and work with vendors. These products are not going to be totally perfect initially. You need clinical groups to work with new technology to perfect it so that it can be improved and then eventually made available to community hospitals the world over.

Dr. Phillips: I think that’s a role that the academic center should play. The problem is many of them don’t have the money anymore to do it, and that’s a big loss to our field.


Dr. Purdy: Yes. And I don’t understand why they don’t have the money because radiation oncology, as you know, generates a lot of money. Unfortunately, that money is being used to support too many other things in hospitals now. I think radiation oncology needs to speak out about this issue. I don’t like the way the funding of medicine is done in this country right now. But I would like see more money put into radiation oncology and in cancer center development.

Dr. Ling: Any final thought, Jim, as to how you’re going to continue to contribute?


Dr. Purdy: Well, I’ll probably try to get back into the field a little bit more in the coming years. The annual meetings have all been away from the West Coast the past few years. I don’t like to fly so much anymore. But one of the things I do miss is the teaching of residents, both physician and physicist. I did enjoy teaching. So I do hope to get back into teaching and also try to work on a few specialized projects. I still go back to Wash U. We have the annual James A. Purdy Lecture usually in March, and I go back and visit with some of my colleagues still there. So I still enjoy very much my relationships back at Wash U.

Dr. Phillips: Jim, thank you so much for taking all of your time to do this for us.


Dr. Purdy: I enjoyed it. I really enjoyed talking to you and Clif again, too. I do miss seeing my colleagues and friends made over the years, so I definitely intend to get back and be a little bit more active in the field.