# Math at Work Monday: Rick Scherer the Certified Medical Dosimetrist

Estimated reading time: 3 minutes, 53 seconds

In today’s world, we’ve all unfortunately been touched by cancer in one way or another.  We may have stood beside a loved one as they battled the disease, or we may have experienced it first-hand.  Rick at First Dayton Cyberknife encounters cancer patients on a daily basis as he assists in their treatment.  I’m thankful for folks like him who use their math skills effectively to help others.

### Can you explain what you do for a living?

I am a certified medical dosimetrist at First Dayton Cyberknife. I work in radiation therapy which is used to treat people who have cancer. I make sure the radiation kills the cancer cells without harming the patient.

The medical dosimetrist is responsible for designing a treatment plan and carrying out calculations with mathematical accuracy for the delivery of radiation treatment based on the oncologist’s prescribed course of therapy. This treatment plan takes into consideration tumor pathology, tumor volume, and inherent dose-limiting structures surrounding the tumor. The treatment plan and radiation field-placement techniques are constructed utilizing sophisticated computer equipment and technology. The medical dosimetrist, along with the radiation oncologist and medical physicist, will work to construct a treatment plan that will meet the prescription written by the oncologist, ensuring that the patient will not lose important healthy organ function and that the radiation delivered will not affect healthy surrounding tissue. These treatment plans not only include the use of radiation but also, in many cases, involve the use of radioactive elements during interstitial brachytherapy procedures. Once the treatment plan is complete, the medical dosimetrist will work closely with the radiation therapists in the implementation of the prescribed plan.

### When do you use basic math in your job?

My whole job is math related. I wouldn’t be able to do my job without math skills. Most of my job pertains to the physical properties of radiation and its interactions with matter. There are calculations depending on energy, energy type (photon, electron, gamma ray), size of the treatment field etc. Most of these calculations are done using a treatment planning system (TPS). We use Eclipse, which is from a company called Varian. We also use a Cyberknife, which uses a software called MultiPlan.

### Do you use any technology to help with this math?

Most of the time I use specialized software for treatment planning but not always. Some plans have to be hand calculated.

Sometimes I use a hand calculation to basically determine how long the machine needs to stay on to deliver a certain dose to a certain depth. For example, the radiation oncologist will prescribe 2400 cGy (centigray is a unit of absorbed dose) in 10 treatments (240 cGy per treatment) to a depth of 80% or sometimes he will say 2 centimeterss. I will use a simple formula that we call a hand calc, 240

80% • 1.002 =299cGy
(where 1.002 is the output factor of field and energy)

1 cGy=1 monitor unit on the machine so the machine would be set to 299 mu’s per treatment for ten treatments for 100% coverage of radiation at the 80% isodose line. This is confusing as heck so I won’t get any deeper with this because I will just go on and on and on….

This is a very simple calculation. Most of the time we aren’t this lucky. Actually most of the time everything is calculated with the Treatment Planning System.

### How do you think math helps you do your job better?

Math is physics and physics is math, so you can’t have one without the other.

### How comfortable with math do you feel?

I feel very comfortable with some math, but with other math I still feel very uncomfortable.

### What kind of math did you take in high school?

The highest I took was Algebra II. I barely passed!

### Did you have to learn new skills in order to do the math you use in your job?

I have had to learn new calculations for new procedures depending on the type of treatment. Some treatments use a real source of radiation which has different factors. In college, medical physics and radiation physics were totally new to me. I can’t really compare it to normal math class. Lots of formulas, laws and other “math stuff.”

One law that is common is radiation is called the inverse square law: In physics, an inverse-square law is any physical law stating that a specified physical quantity or intensity is inversely proportional to the square of the distance from the source of that physical quantity. That is one of the first things you learn.

Want to know more about using math in the fight against cancer?  Let me know, and I’ll be sure to ask Rick your questions.

1. MelodyJ says

It was inspiring to read that Rick barely passed math in high school but now he’s using it to help save lives.

• Laura says

I felt the same way, Melody! I believe that as grownups, we do the math we *want* to do. And that math suddenly doesn’t seem so hard. Thanks for commenting, Melody.