Monte Carlo Simulation in Medicine with TOPAS

March 17-19, 2021,  9:00 AM - 2:15 PM Pacific Time
Online via Zoom

Cost: Free


Registration Closes When 50 Attendees have been Registered


Format/Educational methods: A 15-hour online course with lectures and practical examples divided evenly over three days (5 hours a day, with a 15-minute break). The students will use the TOPAS system hands-on to simulate the examples shown by the instructors and observe the effect of changing parameters used in the different simulations.

Target audience: Medical physicists with basic knowledge of Monte Carlo simulations. The course is designed for new as well as experienced TOPAS users.

Requirement: Participants are required to complete the 2-hour online TOPAS introductory course and have TOPAS version 3.6 or newer installed on their computer prior to the course. Register for the introductory course at Installation instructions are given as part of the course.

Course objectives: To provide the background necessary for participants to reliably use the TOPAS Tool for Particle Simulation for Monte Carlo simulation in medicine. Participants will learn the fundamentals of the Monte Carlo method and its application in medicine, with focus on external beam radiotherapy. They will then learn through lectures and examples how TOPAS provides a simple, effective means to access the Geant4 Monte Carlo toolkit. Participants will leave the course with practical knowledge on how to use TOPAS for their own application.

Registration fee: There is no registration fee for this on-line course.

Registration period: February 1, 2021 at 9 am Pacific Time, closing March 1, 2021 or when we reach 50 participants on a first come, first served basis. REGISTRATION IS NOW CLOSED AS THE COURSE IS FULL

Registration method: Register online at

Activity location: The course will be given online. The instructors and their institutions are listed below.

Zoom: Zoom login information and password will be distributed to registered participants by March 15, 2020, prior to the start of the course.

CAMPEP application statement: This meeting has applied to CAMPEP for approval of 15 MPCEC hours. The online system to be used will allow tracking of attendance.

Sources of support: This course is partially supported by NIH grant U24CA215123.


  1. Bruce Faddegon, TOPAS U24 PI, UCSF (Bruce) – Email
  2. Harald Paganetti, Director of Physics Research, MGH (Harald)
  3. Joseph Perl, TOPAS Chief architect, SLAC (Joseph)
  4. Jan Schuemann, Ph.D., Head of Multi-Scale Monte Carlo lab, MGH (Jan)
  5. Jose Ramos Mendez, Ph.D., TOPAS Developer, UCSF (Jose)
  6. Jungwook Shin, Ph.D., TOPAS Time Feature Developer, MGH (Jungwook)
  7. Aimee McNamara, Ph.D., TOPAS Developer, MGH (Aimee)
  8. KyungDon Choi, Ph.D., TOPAS Developer, UCSF (KyungDon)


Course outline:

Times given in Pacific Time (PT – San Francisco)

Each lecture includes time for questions.

Participants will participate in one of three breakout sessions for each of the examples 1-3 and 4-6 the following day, giving time to try out the examples before the breakout sessions.


Day 1 (Wednesday, March 17, 2021) Jan Schuemann, chair

Introduction to Monte Carlo and TOPAS simulation of x-ray and electron therapy

9:00 am     Overview: MC simulation in medicine with TOPAS (Joseph)

9:15 am     Lecture 1 - Review of fundamentals of the Monte Carlo method (Jose)

10:00 am   Lecture 2 - Monte Carlo in x-ray and electron therapy (Bruce)

11:00 am   Example 1 - Linac treatment head simulation (KyungDon)

12:00 pm   Break

12:15 pm   Example 2 - Variance reduction for a generic x-ray linac (Jose)

1:15 pm     Example 3 - Importing patient CT in DICOM format (Jungwook)

2:15 pm     Adjourn - Participants work on problems from example sessions


Day 2 (Thursday, March 18, 2021) Aimee McNamara, chair

TOPAS simulation of proton therapy

9:00 am     Breakout sessions: Examples 1-3 (KyungDon, Jose, Jungwook)

10:00 am   Lecture 3 - Monte Carlo in proton therapy (Harald)

10:45 am   Lecture 4 - TOPAS advanced capabilities, Part I (Joseph)

11:15 am   Example 4 - Using Time Features to rotate a range modulator (Joseph)

12:15 pm   Break

12:30 pm   Example 5 - Extensions (Jose)

1:30 pm     Example 6 - Proton patient dose, LET and RBE calculation using pre-made extensions (Jan)

2:15 pm     Adjourn – Participants work on problems from example sessions


Day 3 (Friday, March 19, 2021) José Ramos Méndez, chair

TOPAS advanced capabilities and examples

9:00 am     Breakout session: Examples 4-6 (Joseph, Jose, Jan)

10:00 am   Lecture 5 - Geant4 and TOPAS (Jan)

11:00 am   Lecture 6 - TOPAS advanced capabilities, Part II (Joseph)

11:30 am   Example 7 - Using Time Features to create a scanning beam (Joseph)

12:30 pm   Break

12:45 pm   Example 8 - TOPAS-nBio advanced extension (Aimee)

2:15 pm     Adjourn