Posts Categorized: Science

Top 10 Lessons Learned after 10 Years of Plan Studies

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I couple weeks ago, I gave a webinar for the “Best of QADS” series put on by Sun Nuclear Corporation. The webinar was called “The Top 10 Lessons Learned after 10 Years of International Plan Studies.” The presentation (including the live Q&A session) was recorded. You can watch it by visiting the following link.

Click here to register and watch that presentation. (It’s free of course)....

Invariably Variable: The Art of Contouring

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An object at rest tends to stay at rest…
Newton’s First Law

I’ll never forget the reactions of those two physicians, those many years ago. Or, at least I won’t let myself. Not yet at least.

Allow me a moment to retell.

It was about seven years ago and I had just given a talk at a regional meeting in the Midwest. This particular audience was made up of medical dosimetrists and radiation therapists, with a smattering of medical physicists and radiation oncologists. My topic: “Variation in Anatomical Contouring.”

One of my first slides was a clumsy cartoon I had sketched together in PowerPoint. It showed a horse (labelled “treatment planning”) pulling a train of carts, each labelled with a specific technology dependent on the preceding one. And under the horse, representing the road on which the horse and all carts depended, was written one big, bold word: CONTOURING. I found that old cartoon and I’ve reproduced it in Figure 1, below.

Figure 1. My slide (circa ~2010) used to say, essentially, “We can talk about the cart and the horse all we want, but let’s not forget the condition of the road…”

My simple argument was that if you don’t get your anatomy volumes defined correctly – both for targets and critical organs – then everything else downstream suffers. Or, following the horse-and-cart metaphor, inaccurate contours make for a really bumpy ride. All the benefits of the elegant technology of radiation therapy – inverse planning and dose optimization, dose calculation, DVH and other plan metrics, image-guidance, and precision delivery – don’t even matter if your patient anatomy blueprint is wrong in the first place. The anatomy contours are the original “design input” to the personalized medicine that is radiation oncology. Get that wrong, and you’re in trouble.

For the talk, I showed some preliminary data on inter-observer anatomical contours over a range of critical organs. These were controlled experiments where all clinicians were given the same CT images, and the variation I was seeing in some organs was shocking. While there was not much variation for some organs like the brain or lung which are easily seen as clearly defined pixel regions, there was very large variation for many other organs like the parotid, sub-mandibular glands, brainstem, larynx, and even the spinal cord (!)....

Choose Your Own Adventure

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Here is talk I did for the annual AAMD meeting (Atlanta, GA) on June 12, 2016. The response I got and the line of people inspired to tell me “their stories” was a big lift.

Sometimes you just have to let it all hang out. Enjoy.


2016 AAMD Contouring Workshop

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Dr. Aaron Kusano and I will be leading this year’s AAMD Contouring Workshop. This will be our third workshop of this kind in a row, and we believe this year’s agenda is the best. We have incorporated the most frequent request (namely, for more “hands on” contouring time) while keeping the instruction and testing methods that have been successful the past two years.

Below is a short conversation with both of us that provides a nice summary of what we’re doing this year and why. We hope you sign up and join the workshop! It’s a volunteer effort on our part, and our only motivation is because of our passion and yours.


It’s Here: ProKnow

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I am proud to be collaborating with a multi-institutional team to build a system called “ProKnow.” ProKnow stands for “Profound Knowledge,” a term that many of you will recognize from Deming’s famous “System of Profound Knowledge” to improve quality and pride in workmanship across any company, team, or project.

ProKnow will allow the worldwide community to study, and ultimately improve, the standard of care in radiation oncology. We have powerful analytical modules to help you: ensure accurate anatomy contouring, quantify and study plan quality metrics, identify best practices, and ultimately correlate your methods and modalities with patient outcomes.

Here is the link to our cloud-based system: Take a look!...

Testing the Accuracy of Your DVH Calculations

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As an industry, we’ve spent decades talking about testing and improving the accuracy of 3D dose calculations. We’ve invented countless products – both hardware (e.g. dosimeters) and software – to help us along the way, and many AAPM Task Groups have published reports of various flavors and angles on this topic. None of this is too surprising because accurate dose calcs, especially in and around complex tissue shapes and varying densities, are not an easy thing.

3D dose calculation results are primarily used – in conjunction with 3D anatomy contouring – to produce dose volume histograms (DVH) for each target and organ-at-risk. The irony is that for a long time (again, decades), as an industry we’ve forgotten that assembling DVH curves requires calculations itself, and not all of these are created equal. How are anatomy volumes simulated and at what resolution? How are anatomy superior and inferior “end caps” modeled and what is assumed to happen in between axial slices? How does anatomy interplay with an orthogonal 3D dose grid, and what are the effects of that dose grid’s spatial resolution?

DVH calculations are not standard, folks. Not by a far cry.

Together with Vladimir Feygelman, Ph.D. and other scientists at Moffitt Cancer Center (Tampa, FL), we’ve done some really important work studying DVH accuracy and recommending standardized datasets and methods to validate your TPS software. We’ve published our first work in Medical Physics (August, 2015), and you can link to it here.

I hope you can take some time to read our new publication. If you’re a physician, physicist, or dosimetrist (or, just as important, if you’re a TPS software vendor) it will be well worth your time....

AAPM Plan Challenge: SBRT Lung

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The success and interest level in the “Plan Challenge” has now permeated to the AAPM, where we will be integrating a AAPM-dedicated Plan Challenge into a 2-hour special session on Plan Quality at the 2014 Spring Clinical Meeting.

In this Plan Challenge, we offer our first hypofractionated lung case. Participation is encouraged from physicists and dosimetrists alike, both domestic and international. Results will be presented for the first time on March 15, 2015 in Denver, CO, but we will repeat the results via live webinars and/or videos posted online after the AAPM spring meeting.

Here are some key links regarding the 2014 AAPM Plan Challenge:

– Link to register (which will kick off the ROR portal that will steer you through the process)
– Link to a recorded meeting going over the anatomy, objectives, and other interesting discussions on the particular Plan Quality Algorithm to be used
– For Quality Reports users, here is a link to a downloadable protocol which you can import directly into Quality Reports 1.1 or later, to allow self-scoring. Use the protocol labeled “AAPM Plan Challenge.”

Spread the word!...

New QA Publication is “Most Read” Article in Medical Physics 40(11), November 2013

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Thanks to my colleagues and co-authors, our newest publication was deemed “Editor’s Pick” for the November issue of the Medical  Physics journal.

The paper is called “Evaluating IMRT and VMAT dose accuracy: Practical examples of failure to detect systematic errors when applying a commonly used metric and action levels” and can be found in Medical Physics, volume 40(11) which was published in November of 2013.

You can link to the abstract and download the paper here....

New Publication: Interplay of Target Motion and Dynamic VMAT Delivery for SBRT

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Together with Moffitt Cancer Center (Tampa, FL) and the team of Vladimir Feygelman, Ph.D., we continue our ongoing scientific studies with a new publication called “Experimentally studied dynamic dose interplay does not meaningfully affect target dose in VMAT SBRT lung treatments,” just published in Medical Physics 40(9). We are proud to say this paper was selected as one of the “Editor’s Picks” for this issue (which, among other things, means anybody can download the PDF of the article for free – a really nice feature offered by the Medical Physics journal).

Prior to this work, we had been building up our knowledge and toolset for analyzed 4D doses, specifically for volume-modulated arc therapy (VMAT). We applied to clinical SBRT plans (hypo-fractionated with 10 Gy/fraction, 5 total fractions), and at first we were surprised by our results. Then, as we set about understanding the interplay phenomenon for hypo-fractionated VMAT, it started to make more and more intuitive sense why we didn’t see interplay effects. First, the high dose per fraction ultimately allows for many cycles of breathing motion during each daily delivery, which tends to average out the interplay effect. Second, the VMAT segments tend to be less complex at any given time than dynamic IMRT segments (which we know are susceptible to interplay, at least per fraction), also working to drive down interplay. And finally, a strategy of optimization of our VMAT plans was to pump up the dose at the PTV periphery, i.e. purposely induce dose heterogeneity, and the benefits of this for a moving target are evidence in this paper....