Planned couch values, tattooless

SGRT - Best Practice & Applications
1

Hi everyone

Do you have any tips on how to enter the planned couch values to the first treatment fraction such that they correspond with the right ones, patient being near isocenter after automatic drive to the planned values? It is easy to conclude these values if there is a scale in the fixation, but in the pelvis for example with no scale in the fixation… Have you used some kind of homemade scale at the CT for this…? Do you have any tricks for this or do you just shift the couch manually and with the postural video initially check that you are going to the right direction and AlignRT begins to show the deltas on the first fraction? After first fractions image guidance it is easy to save these couch values, but what about beforehand?

Thank you so much!

Marko

2

Hi, we have a system for this- zero the CT couch at full retraction then record the CT long at the reference point (as the couch has been zeroed at the same point-full retraction- these numbers can be compared), use conversion to linac couch long, include iso shift if applicable. We have a conversion spreadsheet in CT/planning for ease of use. Hope that helps.

3

Hi Marko, glad its not just us that wanted to do something like this. We have the indexes for the couch marked on CT using Acrylic labels that are visible on the scan. The planner sets the user origin to one of these markers and runs a piece of ESAPI code which determines the couch values. This has worked well on over a 1000 patients so far. I’m presenting this at the next SGRT conference in November if your there.

4

I shared our solution to this at a SGRT meeting a few years ago. You can find the recording in the SGRT Community Video Library under the title: **Less is More: How to Dramatically Simplify Simulation & New Starts by Embracing a Markless Workflow
**
It does not require any scripting or spreadsheets as the goal was maximum simplicity and reliability.
We have implemented this across many of our locations now and find it solves the first day couch position problem you describe.

Happy to help if you have further questions as well.

Ryan