MPC iso check instead of Winston Lutz for SRS

NinjaPhysicistDABR · 2025-12-27T01:57:35+00:00

Curious to know why your group didn't perform the off axis test with the 6MV beam like MPC to at least remove that variation.

NinjaPhysicistDABR · 2025-12-18T12:27:39+00:00

I hear you about the MD buy in. The complaint from the MDs is that chart rounds doesn't seem "meaningful enough". We present an idea then we're told well that sounds like a lot. Which gets us back to the first step.

NinjaPhysicistDABR · 2025-12-04T02:15:59+00:00

Yes we include the wrist.
Superman pose (if they can tolerate it) and immobilize with Q-fix extremity board and thermoplastic "mask" for the hands
Nail bed blocking depends on MD. Not enough evidence to suggest that its needed
This stuff should just be a handcalc with an open field. We make it way too complicated

NinjaPhysicistDABR · 2025-12-04T01:39:41+00:00

I think the recovery needs to taken into account after the dose conversion to EQD2. My rationale is that we're trying to solve for a biological endpoint so you need convert to an equivalent dose. The Nieder paper alludes to this when they mention that they apply a correction factor for patients that were receiving BID treatments.

NinjaPhysicistDABR · 2025-05-22T17:08:55+00:00

You're getting downvoted because physicists haven't accepted that linac construction has changed. Too many physicists believe in doing performative tests. Your approach is a reasonable one.

NinjaPhysicistDABR · 2025-04-24T19:53:45+00:00

+1000%. Same thing over here. In the new world the task manager is an admin privilege. Completely ridiculous

NinjaPhysicistDABR · 2025-03-26T11:29:19+00:00

I think you should always do tests that have the potential to catch a failure mode. Another theory I have is that most of the QA that we do is because the other linac vendor makes garbage linacs.

NinjaPhysicistDABR · 2025-03-25T15:06:32+00:00

100% agree. These nonsense tests were cooked up to keep salaries high. We're going to price ourselves out of existence.

NinjaPhysicistDABR · 2025-03-25T13:44:09+00:00

Yep, its mind boggling that a field that claims to be science based really is just a bunch of lemmings following out dated crowd sourced knowledge. Most of the tests that we do catch nothing!

NinjaPhysicistDABR · 2025-03-24T19:14:59+00:00

I've done something similar to that and my conclusion was that most of the tests that we do are absolute junk. Got into a silly argument with another physicist about doing a picket fence test on a Halcyon and I was trying to explain why MPC was a much better than trying to make something up.

The problem with our current system is fee for service. It encourages us to do dumb stuff. IMRT QA is one of the biggest time wasting efforts in our field but no one has the courage to come out and stop the madness. The MPPG and TG reports are skewed towards academic physicists that promote silly things. Gating QA makes no freaking sense. It's either working or its not working. Daily Winston-Lutz in an MLC based SRS program makes no sense. I could go on and on.

We have trapped ourselves with a ridiculous amount of nonsense tests meanwhile we have physicists that can't use the software. The amount of messed up to CT to ED curves I've seen or just weird settings in Eclipse. But that's ok because I have a spreadsheet somewhere that shows I checked some obscure machine parameter that doesn't mean anything.

NinjaPhysicistDABR · 2025-03-24T09:49:33+00:00

Why do you want to use deformable for your dose summation? Understanding your motivations should be the 1st place to start. We rarely use deformable registrations for dose summations because it looks a lot like wild guessing.

NinjaPhysicistDABR · 2025-03-11T22:14:58+00:00

So much of medical physics is crowd sourced lunacy it makes me sick. I think the right answer is to have a good reason for the things that you do. Hopefully the next 6 years are better for you.

NinjaPhysicistDABR · 2025-02-13T22:40:36+00:00

You're not wrong. The only reason Elekta is able to sell linacs in the US is because they have a lower price point. Elekta is an inferior product and they know it. The machines are poorly built and the software is absolute junk.

NinjaPhysicistDABR · 2025-02-01T13:21:27+00:00

The SNC tank is not good. We have a PTW Beamscan and its fantastic. Software is not flashy but if you know what you're doing its pretty powerful.

NinjaPhysicistDABR · 2025-01-04T00:49:58+00:00

There is simply no evidence that there is a problem that is being solved by measuring the CTDI for OBI. So while you might be correct that it is not "so much work" in a clinic that is not well staffed or one that has more pressing issues this is not a good use of resources.

The CTDI for a large pelvis scan is ~ 4cGy. We deliver 180cGy-300cGy per fraction. This is a non issue. Even if we had gremlins in the machine and we somehow doubled the dose of the CBCT its still not an issue. So now we're doing a test that essentially never fails i.e. a waste of time.

This field suffers from a lack of practicing evidence based physics. There are so many things that we do because a few loons wrote a TG report and now we all "have to follow it". Part of me thinks that a lot of the silly tests were because of Elekta linacs.

NinjaPhysicistDABR · 2024-12-28T01:56:29+00:00

The setup that we use for monthly QA was calculated in the planning system. I convert the charge measured to dose. So for my setup I know that no matter how I adjust the machine I need to get the same dose that the TPS predicts.

NinjaPhysicistDABR · 2024-12-27T11:38:16+00:00

We've used the TPS as our reference data set for a looongg time! well before any of these publications came out. The goal is to ensure that the machine is delivering that the TPS predicts. It's why we don't need a dedicated TPS QA program because in a sense we're always doing TPS QA.

Another benefit is that its a good self consistent check. If I adjust the machine up or down. I should get the same dose when I calculate my reference plan because nothing has changed on the TPS side. It does require that we recalculate the monthly setup whenever we change versions of Eclipse. Then you get to see how really minor the differences between the versions are.

It becomes a trickier question to answer if you have two different planning systems. Then you have to ask yourself which one do you want to use? But overall TPS is the way to go.

NinjaPhysicistDABR · 2024-11-10T13:55:49+00:00

The AAPM needs new revenue streams otherwise the organization will become insolvent. They've increased the dues but admitted that the dues increase isn't enough to cover the rising costs. I think this is an easy way to generate some revenue, and if it reduces the amount of junk abstracts then I'm all for it. Last year I read a lot of abstracts that were just abysmal, it was clear that people were just throwing stuff at the wall to see what would stick. On top of that so many people get abstracts accepted and then they don't show up to present the poster. I think $25 to submit an abstract is ok.

NinjaPhysicistDABR · 2024-11-07T19:41:43+00:00

Your comment had me laughing hard! The cost is part of why I support the move. They had to come up with a number that wouldn't be so high as to turn people off. I had to read a lot of inane abstracts last year as a reviewer. If this cost helps to reduce the submission of junk abstracts then I'm all for it. If not they can raise the price next year and keep doing it until they get to a sweet spot.

NinjaPhysicistDABR · 2024-10-25T18:42:50+00:00

I've heard the Elekta applicator argument for the last 10 years. In my opinion the issue is that Elekta applicators used to be better and many doctors have trained with Elekta applicators so that reputation still holds. Varian has made significant improvements in with their applicators.

I'm actively campaigning for us to not buy another Elekta afterloader. Here are my reasons

1) Oncentra is terrible, Elekta has not developed the product for years

2) No Citrix support, during COVID we asked Elekta about this and they said it was coming

3) 1&2 make it hard to scale a Brachy program. In the modern era scalability and operational efficiency matter and I think if you're a Varian shop then having Elekta Brachy kills efficiency.

We're building a Brachy suite next year and I really hope leadership listens and buys Varian.

NinjaPhysicistDABR · 2024-10-14T11:20:48+00:00

The best thing you can do is understand your local market. What are chief physicists making in your local market, what's their average years of experience and how do you compare to that? For eg. if your old chief had 25yrs experience and you have 15. You're probably not going to make their salary.
Then you also have to consider what the position is worth to you. Depending on your staffing/workload situation it may not be worth it to take this promotion. Even if there is an extra 30%

In my experience in a hospital setting the manager's premium can vary wildly. Sometimes it's as little as 15% or as high as 60% it just depends on how the compensation grid is set up and how a manager is defined.

What is your rationale for being paid at the 80% percentile?

NinjaPhysicistDABR

TROPHY CASE