Wednesday, 4 February 2015

So You Want to Be a Medical Physicist: Part 1 - What Exactly Is a Medical Physicist

So You Want to Be a Medical Physicist
Part 1 - What Exactly Is a Medical Physicist?


Medical Physics can provide rewarding and stimulating profession, but there can sometimes be a lot of mystery behind what a Medical Physicist does and confusion about the process of getting into it.  I am a senior medical physicist working, teaching, and doing research in Alberta, Canada.  In this and subsequent documents I hope to offer some helpful insight based on my own experience to students or recent graduates curious about Medical Physics careers.

Medical Physics

In its broadest scope, Medical Physics is the branch of physics that applies to solving problems in medicine - problems regarding how various forms of electromagnetic and particulate radiation interact with the human body, development of imaging devices, optimization theory, modeling biological responses to treatment or disease kinetics, etc. are all examples.  In that sense, there is actually a lot of research in physics and in engineering, mathematics, chemistry and biology that could qualify as "Medical Physics."

With that said, throughout this post I'll largely be focusing on clinical Medical Physics though.  By that I mean the practice of physics in the provision of clinical services as a profession.

Radiation Oncology Physicists

Roughly 80% of Medical Physicists work in the field of radiation oncology - the application of radiation to the treatment of cancer (and a few other types of diseases).  This work has many dimensions, which is why sometimes it can be difficult to get a straight answer on what a Medical Physicist does.  It's important to underscore that although patients may not frequently see a Medical Physicist as often as they would a physician or a nurse, nearly all the work a Medical Physicist does has a direct impact on patient care.  Broadly speaking, the work of a clinical radiation oncology physicist involves:
  • establishing, supervising and executing a quality assurance program for the devices used to deliver radiation and their supporting systems (linear accelerators, brachytherapy afterloaders, image guidance systems, proton or heavy ion accelerators, CT simulators, MRI simulators, etc.)
  • commissioning of new radiation treatment devices, facilities and their supporting systems as they are introduced into clinics
  • administration of the computer networks and software used to run the radiation delivery machines and generate treatment plans
  • responsibility for the integrity of radiation therapy treatment plans (which can take the form of plan checking, consulting on difficult, abnormal or new modality plans, and in some cases planning treatments)
  • developing and updating procedures for radiation therapy treatment, and providing technical guidance for administrative decisions
  • investigating clinical problems (everything from calculating the dosimetric consequences of a treatment error to computer network slowness to chasing down the source of an asymmetry in a treatment beam)
  • leading clinical investigations or projects (examples include measuring how accurate your treatment planning system is at calculating dose in the presence of prosthetic hips, or investigating the clinical consequences of delivering radiation at a faster dose rate)

Diagnostic Imaging, MRI, and Nuclear Medicine

The other roughly 20% of Clinical Medical Physicists work in diagnostic imaging, MRI (MRI is it's own specialty), and nuclear medicine.  I won't go into as much detail with respect to these sub-specialties, but conceptually much of the work is similar and again, has a direct impact on patient care.  These sub-disciplines involve commissioning new imaging devices, establishing and maintaining quality assurance testing, network administration, clinical problem solving, consulting, administration and clinical research.  In the imaging specialties the focus of the commissioning and quality assurance work is to provide the optimum image quality for the best possible diagnoses, while balancing that with the safe delivery of radiation and minimizing unnecessary exposure.


Radiation Safety

Medical Physicists (from all disciplines) often also function as radiation safety officers (RSOs) - dealing with the occupational issues involved with the safe delivery of radiation.  This can involve personal dose monitoring, supervising a radiation safety program, teaching, and dealing with all of the licensing (applications, record-keeping, inspections, follow-up actions) involved with operating devices the deliver ionizing radiation.  I should note however that RSOs are not always Medical Physicists.  There is an entire sub-field called health physics that deals specifically with radiation safety.  Because of the cross-over between the fields, it's not uncommon to see Medical Physicists in these roles.

Academics (Teaching and Research)

In addition to clinical duties, many Medical Physicists also have academic appointments at universities and therefore are involved in both teaching and research.  I don't have exact breakdowns, but academic appointments appear to be more common in Canada than in the USA.  In the USA, there are more small and independent facilities.  Roughly one fifth of American Medical Physicists are solo practitioners and in such circumstances, academic responsibilities are unlikely.  In Canada, cancer centers are all publicly funded and tend to be larger facilities associated with universities, and as such have a mandate to conduct research.  According to a recent COMP survey, roughly a quarter of Canadian Medical Physicists' time is, when averaged out, spent on teaching and research combined (the standard deviation is quite wide in my experience).

Teaching duties can involve instructing medical physics graduate students, medical physics residents, undergraduate physics students, radiation oncology residents, radiation therapy students, medical students and many others.  These can be through formal university courses, laboratories, or semi-formal teaching situations such as in-services.

Medical Physics research is difficult to summarize because there are a very large number of problems in medicine that draw on physics to solve.  If you want to get a real idea of what current research involves I would recommend reading the following journals:

There are a lot of other very good journals in the field, and if you're serious about exploring research in Medical Physics, I suggest starting with one of these and following your nose.  If you are an undergraduate student, your library should have a subscription to these journals.  If not, many of them provide open access to the more popular articles - editor's choices, or award winners.  Another very good resource that I use to help keep on top of research in the community is Medical Physics Web. This site provides layperson-friendly summaries of recent publications in the fields along with author interviews that can help one learn about the field, which can be especially helpful as you learn a lot of the technical jargon.


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