Academic Courses > DOS 511 > CT Simulation
DOS 511 - Week 2 Discussion
Writing Prompt
CT Simulation:
After studying the use of a CT simulator, explain how it would be beneficial to have a dosimetrist present at the time of sim. What errors could be avoided by having them present?
After studying the use of a CT simulator, explain how it would be beneficial to have a dosimetrist present at the time of sim. What errors could be avoided by having them present?
Initial Post: CT Simulation
Our center is still very new. We have only been open for about 2 years, and it is the only proton center with a 1000 mile radius. Since there is basically zero supply of therapists who have proton experience, it is necessary to train therapists in some of the unique planning challenges and opportunities associated with proton beam therapy. The idea of a beam that can stop at a certain depth versus a beam that passes all the way through requires different ways of thinking about beam approach angles, such as shooting en face instead of tangents for breast. The fact that three of our four treatment rooms have limited choices of angles available also requires some creativity in how to design beam arrangements. The fact that we are ok with shooting protons through some tables but not others means we have to already have a good idea of the beam arrangement in our heads before the patient is scanned so that we can choose the right table.
In many cases, therapists, dosimetrists, and physicians will have already had a huddle prior to simulation to decide on the best table, patient position, positioning devices, and special arrangements for each patient. If an unforeseen issues crops up during a simulation, such as a patient not being able to comfortably maintain a desired arm position, then a therapist may have to make a decision about a new arm position. Many dosimetrists started their careers as therapists, so they have accumulated years of experience and wisdom that combines with their planning knowledge to form a complete picture of what is possible and what isn't. If a dosimetrist is present, they can discuss options with full knowledge of what will work with a beam arrangement prior to calling the physician back for final approval, saving everyone's time.
The accumulated experience of dosimetrists also helps in training new therapists. Since we are trying to train all of our therapists to be able to operate the CT/Sim at our center, most of the people operating the system are still relatively inexperienced because they may have only rotated to the CT/Sim area a few months ago. Having both a senior therapist and a dosimetrist present can give new people valuable context from both points of view so that they can develop a good sense of what works in the proton world. This sometimes requires some un-learning, since these therapists may have already worked in the photon world for a decade or more, and their ideas of what constitutes acceptable setup tolerances might be quite different from what is needed for proton treatment.
Many of the problems that a dosimetrist can spot could just as easily be spotted by a therapist who is savvy and attentive, but in most cases, the therapists are working quickly and may not have time or mental bandwidth to notice minutiae that are not part of their procedure. A dosimetrist who is simply observing will have the time to watch for things like patients who have not followed instructions to remove jewelry, dentures, constrictive underwear, and other foreign objects. They can act as an extra pair of eyes to make sure the patient is sufficiently straight on the table and that their head is tilted at the correct angle to allow easy beam planning to avoid organs at risk or to easily expose targets in the head and neck. They can watch whether a patient is compliant or fidgeting to see if additional immobilization or adjustments of uncomfortable pressure points might be necessary. During acquisitions of scouts, a dosimetrist can examine anatomy for one final run-through of whether the slice range needs to be expanded to encompass the entirety of an organ for DVH analysis, or even whether enough of the table in included for purposes of collision detection once planning starts. Once the CT is acquired, the dosimetrist can run through the slices to evaluate internal details, patient positioning, and artifacts to determine if the images are good enough for planning.
Since I am not coming to dosimetry from a therapy background, I have not been able to develop this base of accumulated wisdom, but my current manager has been making an effort to have me spend time in the CT/Sim area to observe and learn. I hope to continue to pick up tidbits when I get to my clinical internship site.
Grayden, Seattle
In many cases, therapists, dosimetrists, and physicians will have already had a huddle prior to simulation to decide on the best table, patient position, positioning devices, and special arrangements for each patient. If an unforeseen issues crops up during a simulation, such as a patient not being able to comfortably maintain a desired arm position, then a therapist may have to make a decision about a new arm position. Many dosimetrists started their careers as therapists, so they have accumulated years of experience and wisdom that combines with their planning knowledge to form a complete picture of what is possible and what isn't. If a dosimetrist is present, they can discuss options with full knowledge of what will work with a beam arrangement prior to calling the physician back for final approval, saving everyone's time.
The accumulated experience of dosimetrists also helps in training new therapists. Since we are trying to train all of our therapists to be able to operate the CT/Sim at our center, most of the people operating the system are still relatively inexperienced because they may have only rotated to the CT/Sim area a few months ago. Having both a senior therapist and a dosimetrist present can give new people valuable context from both points of view so that they can develop a good sense of what works in the proton world. This sometimes requires some un-learning, since these therapists may have already worked in the photon world for a decade or more, and their ideas of what constitutes acceptable setup tolerances might be quite different from what is needed for proton treatment.
Many of the problems that a dosimetrist can spot could just as easily be spotted by a therapist who is savvy and attentive, but in most cases, the therapists are working quickly and may not have time or mental bandwidth to notice minutiae that are not part of their procedure. A dosimetrist who is simply observing will have the time to watch for things like patients who have not followed instructions to remove jewelry, dentures, constrictive underwear, and other foreign objects. They can act as an extra pair of eyes to make sure the patient is sufficiently straight on the table and that their head is tilted at the correct angle to allow easy beam planning to avoid organs at risk or to easily expose targets in the head and neck. They can watch whether a patient is compliant or fidgeting to see if additional immobilization or adjustments of uncomfortable pressure points might be necessary. During acquisitions of scouts, a dosimetrist can examine anatomy for one final run-through of whether the slice range needs to be expanded to encompass the entirety of an organ for DVH analysis, or even whether enough of the table in included for purposes of collision detection once planning starts. Once the CT is acquired, the dosimetrist can run through the slices to evaluate internal details, patient positioning, and artifacts to determine if the images are good enough for planning.
Since I am not coming to dosimetry from a therapy background, I have not been able to develop this base of accumulated wisdom, but my current manager has been making an effort to have me spend time in the CT/Sim area to observe and learn. I hope to continue to pick up tidbits when I get to my clinical internship site.
Grayden, Seattle
|
Academic Courses > DOS 511 > CT Simulation
|
Written November 12, 2014
First Semester, Pre-Internship |