Patient treatment with photon beam

In summary, the conversation is about a medical physics question on the number of monitor units required to deliver a certain dose at the isocentre. The given information includes the treatment parameters and tissue maximum ratio for 6MV photons. The student attempted to solve the question using relevant equations but did not use the inverse square law correction. The correct answer is 221, which can be obtained by using the SAD factor in the equation. The conversation suggests seeking help from a more specialized forum for further clarification.
  • #1
Shinobi
1
0

Homework Statement


Doing some past papers but I got stuck to this question! Any medical physicists can give me a hand please?

A patient is treated with a 6MVphoton beam, 12.5 x 12.5cm at 110cm (Source to Axis Distance: SAD) to a 9cm depth. The machine is calibrated to deliver 1.0cGy per MU at 100cm for a 10 x 10cm field. The number of monitor units required to deliver 150cGy at the isocentre is?

Given the information below:
Tissue Maximum Ratio (TMR) for 6Mv Photons
Depth (cm) ---- 10 x 10cm ---- 12 x12cm ----14 x 14cm
1.5 --------------- 1.0000 ------- 1.0000 ------ 1.000
9.0 --------------- 0.810 ---------- 0.818 --------- 0.824

A. 183
B. 210
C. 247
D. 221

Homework Equations


MU = DOSE / ( OUTPUT FACTOR X SAD FACTOR)
SAD FACTOR = (SAD/ SAD + D)2

The Attempt at a Solution


Tried using the equations to solve but still not getting the correct answer which is supposed to be 221.
I got 183 but without using the SAD factor.
 
  • #3
You have not provided enough explanation for a nonspecialist to follow. E.g. what is D in your second relevant equation?
Please either include enough explanation that it becomes just an applied algebra problem, or find a more specialised forum.
 
  • #4
What is your reason for not using the inverse sq. law correction?
 

What is photon beam therapy?

Photon beam therapy, also known as external beam radiation therapy, is a type of cancer treatment that uses high-energy photons (particles of light) to target and destroy cancer cells in the body.

How does photon beam therapy work?

During photon beam therapy, a machine called a linear accelerator delivers a beam of photons to the tumor site. These photons penetrate the body and deposit their energy into the tumor, damaging the cancer cells and preventing them from growing and dividing.

What types of cancer can be treated with photon beam therapy?

Photon beam therapy can be used to treat a wide range of cancers, including those of the brain, head and neck, lung, breast, prostate, and skin. It can also be used to treat certain types of lymphoma and sarcoma.

What are the potential side effects of photon beam therapy?

The side effects of photon beam therapy can vary depending on the location of the tumor being treated. Common side effects may include fatigue, skin irritation, hair loss, and temporary changes in bowel or bladder function. Your doctor will discuss potential side effects with you and develop a treatment plan to minimize them.

How does photon beam therapy compare to other cancer treatments?

Photon beam therapy is a highly targeted therapy that can spare healthy tissue and minimize side effects compared to other cancer treatments, such as surgery or chemotherapy. It may also be used in combination with other treatments for more effective results.

Hot Threads

Recent Insights

Back
Top