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High-energy X-rays are used in the treatment of a cancer tumour inside a patient's body - AQA - A-Level Physics - Question 5 - 2018 - Paper 5
Question 5
High-energy X-rays are used in the treatment of a cancer tumour inside a patient's body. The patient is given a series of scans before the treatment is started. D... show full transcript
Worked Solution & Example Answer:High-energy X-rays are used in the treatment of a cancer tumour inside a patient's body - AQA - A-Level Physics - Question 5 - 2018 - Paper 5
Step 1
Discuss how these scans are used to help provide the best and safest treatment for the patient when using the high-energy X-rays.
Answer
To ensure the best and safest treatment for a patient receiving high-energy X-rays, several key factors are considered:
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Locating the Tumor: Scans are utilized to precisely identify the position and size of the tumor, which helps in accurate targeting during treatment.
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Determining Depth: X-rays can provide vital information about the depth of the tumor, allowing healthcare providers to adjust the treatment plan accordingly.
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Maximizing Treatment Efficiency: By minimizing the time the patient is exposed to X-rays, the risks from radiation are reduced, ensuring a safer treatment.
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Diverse Imaging Angles: Scans taken from various directions can help in evaluating the tumor's characteristics more thoroughly.
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Protecting Healthy Tissue: Special protocols can be employed to minimize damage to surrounding healthy cells while ensuring maximal effect on the tumor.
Step 2
Step 3
Calculate the mass attenuation coefficient of lead for 500 keV X-rays.
Answer
The mass attenuation coefficient ( \mu) can be calculated using the formula:
$$\mu = \frac{h}{z}$$
where:
- \(h\) = half-value thickness = 4.2 \times 10^{-3} \text{ m}
- \(z\) = density of lead = 1.1 \times 10^4 \text{ kg m}^{-3}
Substituting these values in:
$$\mu = \frac{4.2 \times 10^{-3}}{1.1 \times 10^4}$$
Calculating this gives:
$$\mu \approx 3.81 \times 10^{-7} \text{ m}^2 \text{ kg}^{-1}$$
Step 4