Part 2 · Contrast Media, Nuclear Medicine and Radiotherapy

24. Radiotherapy Delivery: Teletherapy, Brachytherapy, Systemic, SRS, IMRT and Protons

~3 min read

Same concept, other depth: Foundation →

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Machine	Source	Features
Cobalt‑60 unit	artificial (Co‑59 neutron activation); t½ 5.27 years; gamma 1.17 and 1.33 MeV (mean ~1.25 MeV)	robust, cheaper, source decays (replace ~every 5 yr), larger penumbra; still used in low‑resource settings
Linear accelerator (LINAC)	electrons accelerated by microwaves → megavoltage X‑rays (6–18 MV) or electron beams	most widely used; no radioactive source; skin‑sparing (build‑up); electrons for superficial tumours
Orthovoltage/superficial	50–300 kV X‑rays	skin cancers, keloid

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Machine

Source

Features

Cobalt‑60 unit

artificial (Co‑59 neutron activation); t½ 5.27 years; gamma 1.17 and 1.33 MeV (mean ~1.25 MeV)

robust, cheaper, source decays (replace ~every 5 yr), larger penumbra; still used in low‑resource settings

Linear accelerator (LINAC)

electrons accelerated by microwaves → megavoltage X‑rays (6–18 MV) or electron beams

most widely used; no radioactive source; skin‑sparing (build‑up); electrons for superficial tumours

Orthovoltage/superficial

50–300 kV X‑rays

skin cancers, keloid