4. (i) Iodine-123 is used as a radioactive tracer to diagnose thyroid problems - Edexcel - GCSE Physics - Question 4 - 2015 - Paper 1

Radium-223 is suitable for use inside the body to treat cancers because it targets bone metastases effectively, emitting alpha radiation that primarily harms cancer cells while sparing surrounding healthy tissue. Its half-life of 11.4 days allows for enough time to deliver an efficient dose, while its non-invasive method of administration enhances patient comfort.

Using radiotherapy for palliative care when cancers are incurable is helpful to patients as it can alleviate pain, reduce tumor size, and improve overall quality of life. It may help manage symptoms effectively, allowing patients to have a more comfortable life during their remaining time.