Academic Courses > DOS 522
DOS 522  Dose Calculation for Medical Dosimetrists
Course Description
This course introduced the basics of how plan radiation exposures to achieve a desired dose in a desired location. We learned the fundamentals of how to doses fall off with distance and by attenuation of the medium through which they pass. The class introduced us to the concepts of where beam scattering can occur, and how important it is in determining the correct dose. Factors that affect scatter such as distance, field size, and beam energy were covered in detail. We learned about beam modifying devices such as wedges and how they affect beam quality and dose distribution. We also showed how handcalculation and computerized secondchecks to verify the results of a planning system's dose calculation can be an important safety check in the planning process.
Assessment
Grading for this class was based on participation in five discussion sessions, five sets of practice problems, and on a final exam. We were also expected to go through all of the practice problems in the appropriate sections of our textbooks. This ended up being quite a large number of problems, but the repetition was a good preparation for the final exam.
Discussions
Week 1: Calculating Dose With or Without Heterogeneity Correction
Week 2: Moving a Calc Point Away from Isocenter
Week 3: Irregular Field Calculation Methods
Week 4: Computerized MU Checks vs Hand Calculations
Week 5: Monitor Unit Discrepancies on Second Check
Week 2: Moving a Calc Point Away from Isocenter
Week 3: Irregular Field Calculation Methods
Week 4: Computerized MU Checks vs Hand Calculations
Week 5: Monitor Unit Discrepancies on Second Check
Reflections
At the conclusion of each course, students are asked to reflect on what they have learned about the material and about themselves. The reflection is guided by five questions:
The new knowledge and skills I gained during this course were...
Through repetition, repetition, and repetition, I have learned an intuitive sense for how various changes in setup distances, treatments depths, filters, field sizes, and other criteria affect an xray beam's output as they are adjusted. At first it was just rote memorization, but now I can easily understand why things work the way they do.
The new knowledge and skills will benefit me by...
Being able to understand the effect that a change to a beam will have on a plan is critical to the entire process of external beam planning. Being able to intuitively predict effects without having to guess and check multiple times is a valuable skill not only for time savings, but also for being able to formulate a strategy that may involve multiple interdependent changes to several beams all at once. This can open the door to optimizations that involve starting fresh with a new approach rather than trying to endlessly optimize a deadend approach.
I struggle with...
I am still a bit puzzled by the timer error calculation for Cobalt60 treatments. The formula is quite simple, but for some reason, I can't tell from its structure how it has any practical meaning. I think I need to find an explanation of how it was derived, so I can mentally map a real world meaning onto its parts. I also struggle a bit with TAR and BSF equations, because we didn't have a lot of practice in those areas. Most of these functions are obsolete at this point, but I would still be more comfortable with more practice.
I feel pretty good about...
I feel great about wedge transmission factors. The project paper that I wrote ended up going into way more detail than I had expected to go into, and I explained every step of the way. The process of collecting and organizing thoughts in order to write them out coherently creates a deeper level of understanding than just reading over it several times. Because of this, the best way to learn something is to try to teach it.
Other reflective thoughts...
The textbook practice problems and the practice problem sets assigned each week really helped me prepare for the final exam. I was quite nervous about the exam, but once I got into it, all of the time I spent practicing really paid off. I have now developed a habit of forming triangles in the air with my fingers to simulate what problems are asking, and I end up drawing a lot of triangles on scraps of paper to help out with quick calculations and geometry problems. I will have to make sure I am never far from a stack of scratch paper.
The new knowledge and skills I gained during this course were...
Through repetition, repetition, and repetition, I have learned an intuitive sense for how various changes in setup distances, treatments depths, filters, field sizes, and other criteria affect an xray beam's output as they are adjusted. At first it was just rote memorization, but now I can easily understand why things work the way they do.
The new knowledge and skills will benefit me by...
Being able to understand the effect that a change to a beam will have on a plan is critical to the entire process of external beam planning. Being able to intuitively predict effects without having to guess and check multiple times is a valuable skill not only for time savings, but also for being able to formulate a strategy that may involve multiple interdependent changes to several beams all at once. This can open the door to optimizations that involve starting fresh with a new approach rather than trying to endlessly optimize a deadend approach.
I struggle with...
I am still a bit puzzled by the timer error calculation for Cobalt60 treatments. The formula is quite simple, but for some reason, I can't tell from its structure how it has any practical meaning. I think I need to find an explanation of how it was derived, so I can mentally map a real world meaning onto its parts. I also struggle a bit with TAR and BSF equations, because we didn't have a lot of practice in those areas. Most of these functions are obsolete at this point, but I would still be more comfortable with more practice.
I feel pretty good about...
I feel great about wedge transmission factors. The project paper that I wrote ended up going into way more detail than I had expected to go into, and I explained every step of the way. The process of collecting and organizing thoughts in order to write them out coherently creates a deeper level of understanding than just reading over it several times. Because of this, the best way to learn something is to try to teach it.
Other reflective thoughts...
The textbook practice problems and the practice problem sets assigned each week really helped me prepare for the final exam. I was quite nervous about the exam, but once I got into it, all of the time I spent practicing really paid off. I have now developed a habit of forming triangles in the air with my fingers to simulate what problems are asking, and I end up drawing a lot of triangles on scraps of paper to help out with quick calculations and geometry problems. I will have to make sure I am never far from a stack of scratch paper.
Academic Courses > DOS 522

Published February 22, 2015
Second Semester, 2 Months into Internship 