Radiotherapy: 40 years from tracing paper to tomotherapy

NHS

Physicist Andy Moloney and Clinical Oncologist David Morgan reflect on how radiotherapy developed since their early careers

 

We first met in the autumn of 1981, when the NHS was, at 33 years from its inception, but a youngster. Andy had recently joined the Radiotherapy Physics staff at Nottingham General Hospital after graduating in Physics from the University of Nottingham, and David was returning to the clinical Department of Radiotherapy and Oncology after a year’s Fellowship at the Institut Gustave-Roussy in France. A firm friendship rapidly developed, one that continues to this day.

On reflection, joining the radiotherapy fraternity at that time was a leap of faith. The perceived wisdom amongst many of our scientific and clinical colleagues at the time was that this treatment technique was outdated and overshadowed by radical surgical procedures, new chemotherapy agents and biological modifiers poised to reduce radiotherapy to the history books.

picture 063This was a time when, in this Cinderella of specialties, physics planning was achieved by the superposition of two dimensional radiation plots (isodoses) ,using tracing paper and pencils, to produce summated maps of the distribution. The crude patient outlines were derived from laborious isocentric distance measurements augmented by the essential “flexicurve”. The whole planning process was slow and labour intensive fraught with errors and ridiculed by colleagues in the perceived prestigious scientific and clinical disciplines. The principal platform for external beam radiotherapy delivery, the Linear Accelerator (LinAc), had also reached something of a plateau of development, albeit with improved reliability, but few fundamental changes. Caesium tubes were transported from the “radium safe”, locked in an underground vault, to the operating theatre in a lead-lined trolley, where they were only loaded into “central tubes” and “ovoids” after the examination under anaesthetic (which was performed with the patient in the knee-chest position); they were then manually placed into the patient, who went to be nursed on an open ward, albeit behind strategically placed lead barriers.

For no sites outside the cranium was Computer Tomography (CT) scanning available. Magnetic Resonance Imaging (MRI) was still a vision seen only by a small number of enthusiasts.

All these limitations were met by a developing team of scientific and clinical enthusiasts believing in the future of radiotherapy if only technology could deliver solutions to address an improving understanding of the differing cancers and their radiobiology.

picture 066In the latter half of the eighties these solutions began to crystallise. Computers were being introduced across the NHS and their impact was not lost in radiotherapy. Pads of tracing paper were replaced with the first generation of planning computers. The simple “Bentley-Milan” algorithms could account for patient outlines accurately and speedily and optimising different beam configurations became practical. Consideration of Organs at Risk, as defined by the various International Commission on Radiation Units (ICRU) publications, became increasingly relevant. Recognition of the importance of delineating the target volumes and protecting normal tissue required improved imaging and this was provided by the new generation of CT scanners. In the nineties these were shared facilities with diagnostic radiology departments. However, the improvements provided by this imaging, enabling accurate 3-dimensional mapping of the disease with adjacent normal tissues and organs at risk, dictated their inclusion into every radiotherapy department soon after the millennium. The added bonus of using the grey scale pixel information, or Hounsfield numbers, to calculate accurate radiation transport distributions soon followed when the mathematical and computer technology caught up with the task. The value of MR and Positron Emission Tomography (PET) imaging was also recognised in the diagnosis, staging and planning of radiotherapy and the new century saw all of these new technologies embedded within the department.

Mould room technology was also improving with “instant” thermoplastic immobilisation shells replacing the uncomfortable plaster and vacuum forming methods. Custom shielding with low melting high density alloys was becoming routine and it was not long before these techniques were married with the emerging CT planning to provide “conformal” treatments.

picture 067LinAc technology also received added impetus. Computers were firstly coupled as a front end to conventional LinAcs as a safety interface to reduce the potential for “pilot error”. Their values were soon recognised by the manufacturers and were increasingly integrated into the machine, monitoring performance digitally and driving the new developments of Multi Leaf Collimators (MLC) and On Board Imaging (OBI).

The dominos for the radiotherapy renaissance were stacked up, but it needed the radiographers, clinicians and scientists to decide on the direction of travel. Computer power coupled with advanced electro-mechanical design had transformed MLC efficiency and resolution. Conventional conformal planning was now progressively superseded by sophisticated planning algorithms using merged CT and MR images. Intensity Modulated RadioTherapy (IMRT) had arrived in its evolving guises of multiple fixed field, dynamic arc therapy (RapidArc) or Tomotherapy. Whichever technique, they all offered the radiotherapy “Holy Grail” of providing three dimensional homogeneous dose distributions conformed to the Planning Target Volume (PTV) whilst achieving the required dose constraints for organs at risk and normal tissue preservation.

The tools had arrived, but an infrastructure to introduce these “toys” safely into a complex clinical background had also developed alongside. Quality standards (ISO9000), Clinical Trials, Multi Disciplinary Teams and Peer Review were governance mandates for all oncology departments and radiotherapy was leading the way. In forty years, radiotherapy had lost the “Cinderella” image and had been invited back to the clinical ball. Noticeably, breast and prostate adenocarcinoma constituted half of the radical workload.

The question remains of how and why did this transformation occur? Obviously the developing computer power and technology were the pre-requisites for many of the developments, but a key catalyst was the foresight of all of the radiotherapy family from which enduring friendships have been forged. The working lives of the clinicians and physicists involved in radiotherapy planning have probably changed more dramatically than those of any other medical and paramedical groups over the last 35 years.

We may have retired, but we still cogitate about the future direction and science behind this developing and essential cancer treatment and look forward to our younger colleagues enjoying their careers as much as we enjoyed ours.

 


About David Morgan

david morganDr David A L Morgan began training in Radiotherapy & Oncology as a Registrar in 1977, and in 1982 was appointed a Consultant in the specialty in Nottingham, continuing to work there until his retirement in 2011. He joined the BIR in 1980 and at times served as Chair of its Oncology Committee and a Member of Council. He was elected Fellow of the BIR in 2007. He is author or co-author of over 100 peer-reviewed papers on various aspects of Oncology and Radiobiology.

 

About Andrew Moloney

andy moloneyAndy Moloney completed his degree in Physics at Nottingham University in 1980 before joining the Medical Physics department at the Queens Medical Centre in the same city. After one year’s basic training in evoked potentials and nuclear medicine, he moved to the General Hospital in Nottingham to pursue a career in Radiotherapy Physics and achieved qualification in 1985. Subsequently, Andy moved to the new radiotherapy department at the City Hospital, Nottingham, where he progressed up the career ladder until his promotion as the new head of Radiotherapy Physics at the North Staffordshire Royal Infirmary in Stoke-on-Trent. Over the next twenty years Andy has acted as Clinical Director for the oncology department and served on the Radiation Physics and Oncology Committees at the BIR and was appointed a Fellow in 2007. He has been the author and co-author of multiple peer reviewed articles over the years prior to his retirement in 2017.

 

When medical physicists wore white coats

NHS

Dr Edwin Aird shares his memories of the revolution he has experienced working in the medical physics department.

 

Edwin Aird portrait

While I was an undergraduate at Newcastle University (1962), the 2nd year honours group was invited to visit the Medical Physics Department at Newcastle General Hospital. I was so impressed with the department and the range of things they were doing and the application of physics to medicine that I wrote to Professor Frank Farmer (Head of Department at that time) to ask about working there. He responded with a proposal that I apply for a special research grant that he was hoping for locally and that I write again after my graduation.

The following year I got in touch with Frank Farmer again and was accepted on an MSc grant to study “In-homogeneities in Radiotherapy”; one year in the first instance (on a grant of about £700).

Meeting 1970 1

I can’t now remember my first day exactly; not sure what office I had, but I do remember the Professor’s insistence on donning a white coat (provided and laundered by the hospital) when arriving at work, This ‘uniform’ was thought to be a vital sign to patients that physicists were part of the ‘clinical’ team.

I divided my time in that first year between research and clinical work (interestingly, this was part of the philosophy of some of the early physicists, many of whom in the 1930s and 40s had transferred from academic physics, including Frank Farmer); the situation now couldn’t be more different.

Fig 1

Image 1 The gantry mounted linear accelerator at Newcastle General Hospital [ref 2]

So, on the routine side, I began to learn about radiotherapy: its planning and treatment. Newcastle at that time had two cobalt machines (Mobaltron-60s) and two linear accelerators as well as two Marconi 250kV sets and a Philips SXT (Superficial X-rays). This latter set I used extensively a little later in my career to optimise the characteristics of the Farmer chamber (image 1).

The main linear accelerator was manufactured by Mullard (a branch of Philips), which Frank Farmer had installed as the first gantry-mounted 4MV linac (image 2). There were a few stories about the installation of this linac. In particular I remember this: the team had reached the point where they needed to produce X-rays so needed a high atomic number transmission target. Someone found a sovereign, but forgot the amount of heat produced when the high energy electrons hit it. The sovereign promptly melted and fell out of the linac head. (This linac went on to perform 25 years’ service).

Fig 2

Fig 2 Newcastle Simulator (Frank Farmer at Controls) [ref 3]

For those physicists who find quality assurance (QA) on linear accelerators today a huge burden, my recollection of the checks we performed on this linac amounted to: dose measurements and field size checks. There was little attempt to measure flatness since the accelerated electron beam wasn’t bent before striking the target, so no perturbations in intensity across the field were expected.

 

 

Fig 3

Fig 3 A Head and Neck Xeroradiograph showing potential. Treatment volume [ref 3]

 

Treatment planning was done by hand, often mainly using % depth dose, but also with some isodose curves for more complex plans on tracing paper; on to an outline of the patient performed using lead wire and other devices, e.g. callipers. Newcastle was unique in having developed a home-made simulator (using a radiotherapy SXT unit mounted on a gantry (image 2) that allowed an image to be viewed on a Xerox plate immediately without the need for film development (ref 3, see also image 3).

The first computer in the department, which was to revolutionise treatment planning, came to Newcastle in the early 1970s and was called a PDP 8, the ‘Rad8 system’ developed by Bentley and Milan. (image 4 [ref 4]).

Radium tubes and needles were still extensively used at this time for intracavitary and interstitial brachytherapy. I was also required to calculate the dwell times for gynae radium insertions (using ovoids and central vaginal sources with a modified Manchester system for the gynae and radium needles, mainly in back of tongue with radiographs and Paterson Parker tables). Following the calculation of the radium dwell times I would then go up to the ward to discuss the removal times, for each patient, with sister on the ward. Amazing now to think how much radioactivity (up to 105mg – equivalent to approximately 389 MBq-or more) for gynae insertions was handled by several different groups of staff at that time.

In those early years I also learnt the elements of radiation protection and nuclear medicine. Radiation Protection (guided by a ‘Code of Practice’; an excellent document that was used to help write the ‘Guidance Note’ now used under Ionising radiation Legislation) was regionally organised. Very early in my career (there were only two of us to perform the external radiation work: myself and MJ Day), I found myself organising visits within Northumberland, Cumbria and parts of Durham. (See The Regional Centre below). These were more as inspections than to make many measurements (not the very extensive QA that is performed now, although we did use film or image intensification – only recently developed – to look for faults in lead aprons; and we measured exposure levels in and out of beam with the ‘37D’ (Pitman) dosemeter (originally developed by Sidney Osborne as an excellent versatile instrument for exposure measurements ref 5). I learnt a pattern of inspection of barriers, filtration, lead aprons etc. very quickly. [In the early 1970s the NRPB decided to do their own inspections and were surprised to find that, because the HPA had organised things so well there was little need for NRPB to get too heavily involved].

My memories of nuclear medicine: incredibly slow rectilinear scanners, prior to the commercial development of gamma cameras; kidney function (renogram) using two ‘D’-shaped detectors (scintillation) with manual optimisation of their positions connected to count rate meters and chart recorders.

The regional centre

I’m not sure how many hospitals this covered in my early days in Northumberland, Tyneside, Durham and Cumbria. I know when Keith Boddy implemented Frank Farmer’s plan to have a small physics department (where gamma cameras were installed in district general hospitals) there were thirteen hospitals with physics departments in the region. Prior to this – from about my 3rd year at Newcastle – I was delegated to look after the small centre in Carlisle where there were two Marconi 250kV sets, an SXT and some iodine treatment. In the 1950s this had been the job of Jack Fowler who used some of his time to study arc therapy on 250kV (see ref 6).

Rad 2014 photo

Edwin Aird (right) receiving the BIR Sylvanus Thompson Award from Andy Beavis

In those early years I also found time to help develop differential X-ray absorptiometry to measure antimony in the local Tyneside Antimony workers’ lungs (organised by the Newcastle University Department of Industrial Health). I was also able to build on this experience to develop my own equipment, using characteristic X-rays, to measure bone mineral in the femur. This clinical work allowed me to meet a new set of clinicians (other than radiotherapists – as Clinical Oncologists were then called – and radiologists) involved with bone loss in patients: kidney specialists, endocrinologists and geriatricians. Commercial equipment has since been developed to perform bone mineral and body composition measurements (GE Lunar, Hologic, and Norland).


References:

  1. Aird EGA and Farmer FT. The design of a thimble chamber for the Farmer dosemeter. Phys Med Biol 1972 17: 169–174. https://doi.org/10.1088/0031-9155/17/2/001
  2. Day MJ and Farmer FT. The 4 MeV Linear Accelerator at Newcastle upon Tyne. Br J Radiol 1958; 31: 669–682. https://doi.org/10.1259/0007-1285-31-372-669
  3. Farmer FT, Fowler JF and Haggith JW. Megavoltage Treatment Planning and the Use of Xeroradiography. Br J Radiol 1963; 36: 426–435. https://doi.org/10.1259/0007-1285-36-426-426
  4. Bentley RE and Milan J. An interactive digital computer system for radiotherapy treatment planning. Br J Radiol 1971; 44: 826–833. https://doi.org/10.1259/0007-1285-44-527-826
  5. Osborn SB and Borrows RG. An Ionization Chamber for Diagnostic X-Radiation. Med.Biol1958; 3: 37–43. https://doi.org/10.1088/0031-9155/3/1/305
  6. Fowler JF and Farmer FT. Measured Dose Distributions in Arc and Rotation Therapy: A Critical Comparison of Moving and Fixed Field Techniques. Br J Radiol 1957; 30: 653–659. https://doi.org/10.1259/0007-1285-30-360-653

About Dr Edwin Aird

Edwin Aird was Head of Physics at Mount Vernon Hospital from 1988-2012 and Head of Radiotherapy Physics at St Bartholomew’s Hospital from 1985-1988. He was Head of Radiotherapy Physics at Newcastle General Hospital from 1980-1985. He is an IPEM Chief Examiner 1994-1997 (Physics Training Scheme), FRCR (RT) Examiner 1989-1993, Radiotherapy Degree (External Examiner (Liverpool University): 1993-1996. He is a IAEA: Qualified Expert: 1999-2005 and an LH Gray Trustee: 1999-2003.

He was awarded the BIR Roentgen Prize in 2005 and delivered the Silvanus Thompson: Award and Eponymous Lecture 2013.