Brachytherapy
An internal radiation therapy technique where sealed radioactive sources are placed directly inside or adjacent to a tumor.
Governing formula
Inverse Square Dose Falloff: D(r) ∝ 1 / r²
SI unit
Gy/h (High or Low Dose Rate)
In depth
By placing radioisotope seeds (like I-125, Pd-103, or Ir-192) directly inside target tissue, inverse-square law dose falloff delivers maximum radiation to the tumor while minimizing dose to surrounding normal organs.
Examples in the real world
Permanent Iodine-125 seed implantation treating localized prostate cancer.