Trying to find out more about dosimetry

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justsomename

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I apologize if this is a little off topic, as this seems to be a subsection of Physician/Resident forums, but I wasn't sure where else to ask this.

I've been doing some reading about dosimetry and it has really piqued my interest. I've read descriptions online about the types of things they do. I understand they perform duties like design radiation fields and do dosing calculations, but I'm hoping someone on this forum that is in the know can be a little more specific in regards to their duties so I can better understand the day-to-day challenges of a dosimetrist.

What are the challenges I'd be facing as a dosimetrist? What is it about designing radiation fields and calculating dosages that requires a human's problem-solving and critical reasoning skills?

Is treatment planning for a dosimetrist sort of like determining a compromise between using enough radiation (and using it in the right places) in order for it to be curative, but not so much that it causes severe side effects or puts the patient at greater risk?

Thanks for any insight.

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What are the challenges I'd be facing as a dosimetrist? What is it about designing radiation fields and calculating dosages that requires a human's problem-solving and critical reasoning skills?

What you would be doing daily as a dosimetrist depends highly on where you are practicing (private vs. academic) and what type of hardware and treatment-planning software is available.

For larger, academic institutions dosimetrists are generally divided up by treatment site (e.g. head/neck, CNS, GU, GI, lung) or by technology (e.g. proton, IMRT, 3DCRT, clinical set up).

What you do, again, is highly variable by institution but would include some/all of the following:

- Contouring normal structures (generally the physician countours the tumor volumes); this involves a general understanding and familiarity with CT-based anatomy

- Based on the tumor's location and size dosimetrist choose the optimal beam arrangement; if you are using IMRT then you ask the software to inverse plan for you at this point

- Using the beams you selected (w/ or w/o IMRT) you have to decide if the plan is optimal; if not, then you have to re-adjust your parameters as needed; one of the key ways to determine the feasibility of a plan is to look at the dose-volume histograms which tells you which structures get what dose; each structure has a dose tolerance above which it is dangerous to go

- After you come up with one (or more) plans you have the physician and physicist look over it and they either approve it outright or work with you to optimize it further; sometimes the physician will give you relevant clinical information that you might not have otherwise known

- Once the plan is approved it is downloaded to the treatment machines where the radiation therapists can position the patient; pretty much this is where the dosimetrist's job ends

Other responsiblities include:

- Monitoring radiation doses on patients during treatment for quality assurance (e.g. using diodes, TLDs, etc).

- Calculating the output of the hardware (linear accelerators) for a given treatment set up

Is treatment planning for a dosimetrist sort of like determining a compromise between using enough radiation (and using it in the right places) in order for it to be curative, but not so much that it causes severe side effects or puts the patient at greater risk?

Yes, well put.

Although physicians are trained in dosimetry there is aboslutley no substitute for a good dosimetrist. We have somtetimes given them what we thought were nearly impossible parameters but they generate a beautiful plan which fulfilled all of our criteria.
 
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GFunk's assessment is spot on. Your role is largely determined by the size and style of practice in which you'll be working.

I worked in a small private practice clinic and I had a laundry list of responsibilites, most of which are detailed above. The only additional responsibilities I would add to the list are chart checks (quality assurance measure) and block cutting (for electrons and occassionally photons). However, these responsibilities are subject to change as well depending on institution.

One quick point to note: Dosimetrists generally have very little or no patient contact. You are still a very integratal part of the treatment team however often times you will never meet the person behind the plan.
 
Thanks everyone who responded. Especially Gfunk, wow, that was a very detailed description and gave me some great insight into the profession. I definitely appreciate that.
 
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