For those geeks who are interested in the technology used for radiation therapy, this is some info on the machine that performed the treatment on me.

It is made by Varian and the system is called Trilogy. This system does not use a tube, rather you lay on a platform and the arm swings 360 degrees around you. One other thing of note is the system shoots the beam and is guided by a panel that has a large set of plates/fingers that constantly move in and out and provide the outline of the area being targeted.

Many people mention clicking. I believe this is tomo-therapy type systems that administer dosage in slices thus the clicks whereas Trilogy is 100% real time adjusting the dosage so there is no clicking or fixed slices.

Lastly, the "beam on" time is 60 seconds in each sweep around the body. It goes around counter then clockwise for a total of 120 seconds. I noted the time once and it was 5 minutes from the time I laid down to the time I popped off the platform.

Hello Don:

I too am using a Varian Trilogy. From conversations with my RT she says they can use the machine in two different modes.

1. Continuous arc - apparently what you are getting.

2. Point and shoot - as many stationary shots as dosimetrist determines necessary.

The method of operation is chosen by the RO. Apparently they have different opinions as to which is better. My RO prefers point and shoot, so I get 11 shots each treatment. Laying on the table looking up at 12:00, my shots start at 5:30 (below right shoulder), 5:00, 3:00, 1:30, 12:00, 10:30, 9:30,
8:30, 7:00, 6:30 and then back up to 12:00 with a table reposition for a super-clavicular shot where they radiate the lymph nodes below my adams apple. Each shot is about 15 seconds in duration.

After 25 treatments they terminated the super-clav, saying I'd received all the dosimetrist wanted.

New, the machines were about $2.4 million each. Mine is about 4 years old. It takes about 2 hours to warm up every day before use and the beam is high energy x-rays, capable of going through you as well as the concrete wall on the other side of the room. The wall next to the therapists has about a half inch of lead in it besides the concrete. There are parking spots outside the other wall, so I expect they put lead in that wall too.

I'm a bit of a techy too.

Tony

2.5" of concrete, 1" of steel and 0.5" of lead all reduce the radiation levels by about half. Very, very roughly.

My treatment started with the continuous arcs and then in the last several they switched to the targeted spot treatment. They called the latter "boost".

I had the Varian IMRT at one facility, most likely the same at two other locations, not sure of the models though, and looks the same as the Trilogy, but may have done "Rapid Arc" too, which dosage time is accelerated as mentioned, and they may do IGRT also, not sure. Mine, point and shoot, some continuous, took about 17 minutes for 17 zaps, done bilaterally, and left side received the most, 9, and longer time.

My last IMRT a year ago, was 6 zaps, and the techs had to come in and turn the whole table for the last two shots to be in a 3 o'clock position.

[quote]Benefits of Trilogy

The Trilogy is the world's first image-guided radiation therapy system optimized for both conventional and stereotactic approaches to treating cancer. The versatile Trilogy system delivers IGRT as standard, and can be used to deliver 3D conformal radiotherapy, IMRT, stereotactic radiosurgery, fractionated stereotactic radiation therapy, and intensity-modulated radiosurgery for cancer and neurosurgical treatment.

The versatility of the Trilogy enables any area of the body to be treated using the latest and most effective treatments available. This includes advanced radiosurgery treatments. With full under couch access and multi-treatment modalities, the flexibility of the Trilogy helps clinicians offer treatments from a range of techniques suited to the needs of each patient.

In the case of IMRT, this includes:

Step and shoot
Sliding window
Small to large fields
Coplanar or non-coplanar fields
Radical or palliative plans[/quote]
As you can see Varian supports quite a variety of methods. It also needs the nuclear bomb shelter surrounding the thing.
From what I read about Tomotherapy is it is portable in that all the shielding is self contained, something like that.

Gulf - I've always wondered how common it is for treatment plans to alter the dosing of the fractions over the course of the plan. I suspected but never did validate that some of my side effects arrived at different times due to a change in what they zapped each day. Then again, it could just as easily be the simple accumulation of rads that take their toll in due time.

I did notice a variation in symptoms, too. The RO said the dose was constant, but maybe how it was directed altered the side effects.

From the way the treatment plan is specified; i.e. 2yg by 35 fractions = 70gy, then that aligns with constant dosing throughout. As to altering the map over time, that seems less likely. Just from what I saw of the process of identifying the areas to be radiated and the contouring and creation of the actual plan that is fed to the accelerator, it seems like more work for the dosimetrist and the risk outweigh the benefits.
Of course, my guessing is about as good as counting grains of sand on the beach. :-)

I had 35 doses from collar bone to chin (tumor and affected nodes). I then had 5 doses of "cone-down boost" to the tumor site. Ten days after the boost was, shall we say, interesting.

Interesting stuff for sure. I had Tomotherapy. From the little bit of reading I've done, it seems they are essentially the same sans the time on the table.

Here's an interesting article from 2008 on the subject.

http://medicalphysicsweb.org/cws/article/research/33598

The bottom line is if it works period. Both are equally effective from what I can discern.

Positive thoughts

"T"

"T"
Great link. It highlights, at least at the time, neither one was clearly superior to the other. Five years on in the clinical medical business is not much time; yet I'd be curious if much has changed.

Don

Just came across this document from ncbi about "boost". There is a method that does alter the dosing from fraction to fraction and targets areas in varying amounts.

I'm no expert here but it seems logical that the changing dose over the standard 35, 7 week timeframe can indeed be a factor in why radiated areas seem to be more/less impacted over treatment.

http://www.ncbi.nlm.nih.gov/pubmed/14644486
http://www.ncbi.nlm.nih.gov/pubmed/23824134

There are quite few different radiation delivery techniques besides the standard fractionization. Even with standard fractions, I don't think it's the same delivery over the course of the 7 weeks of treatment. One reason is radiation declines in tumor kill rate after 25 treatments or 5 weeks, due to tumor regeneration, oxygenation, and more is needed to kill the tumor, and that why you see treatments for 6 and 5 7 weeks that are shorter in durstion, and more effective in some studies, and hardly any for 8 weeks, which more is not better. How this is done in fractions, volume, percentage, other, I don't know. Only the wizard does

Altered fractionization
Concomitant boost
Split course
Hyperfractionization
Hypofractionation
Others

Interesting video how the linear accelerator works:

http://m.youtube.com/watch?v=jSgnWfbEx1A

Thanks for the video link.

Look about 6 minutes into your video and about 2 minutes into the this one http://www.youtube.com/watch?v=eZS6DVGBx0k

This describes what fascinated me about the whole thing. I would see those leaves dynamically reshape constantly and it was the beam being shaped to hit the target in the manner specified in the planning system. The link I provided is from 10 years ago so there has been refinement for sure but the underlying principles still apply. One thing is the newer units are continuous sweeping and do not stop at all around or click so I suspect the dose is now able to be given all the time as it sweeps around. The processors are much faster now so they can keep up with all the real time calcs that previously was a go-stop-reposition-go-stop affair. Of course that is all a big guess on my part. lol