Water Phantom (3D)

Question 1

What is a water phantom used for?

Answer 1

A 3D water phantom is used for acceptance, commissioning, validation of pre-commissioned linacs, and annual QA.
i. Acceptance – validation if the machine is within its specified parameters
ii. Commissioning – measurement of beam/machine characteristics used for beam modelling
iii. Validation of pre-commissioned linacs – validation if the machine’s beam characteristics match the data used for the beam model
iv. Annual QA – comparison of beam characteristics over time against the beam characteristics at the time of commissioning

Question 2

What’s the technology we are using for determination of the detector position and what’s the difference compared to the competition?

Answer 2

The technology is called magneto-strictive technology. The advantages compared to the technology the competition is using (stepper-motors) are the following:
i. No tear and wear since it is contact-less
ii. No regular calibration required
iii. Absolute distance instead of a relative distance

Question 3

What kind of dosimetry is a 3D water phantom mainly used for and what is the difference between the two types of dosimetry?

Answer 3

a. Relative Dosimetry
b. The difference between relative and absolute dosimetry is
i. Relative dosimetry means the measurement of profiles and percentage depth doses (PDDs). All data points are relative to a reference point (normalization point)
ii. Absolute dosimetry means the (point) measurement of dose (absorbed dose under standard conditions)

Question 4

What machines are our 3D water tanks compatible with? And what machines are the not compatible with?

Answer 4

a. Compatible with C-arm linacs including Elekta Harmony, Varian Halcyon, and Cyberknife
b. Not compatible with MR Linacs (both) and ZAP-X

Question 5

What are the competitive products from other vendors to our 3D phantoms?

Answer 5

a. PTW – Beamscan
b. Sun Nuclear – SunScan 3D
c. Standard Imaging – DoseView 3D