Define the term "radiation therapy."

Radiation therapy is specifically defined as a treatment modality that utilizes ionizing radiation to target and eliminate cancer cells. This therapeutic approach aims to damage the DNA of cancerous cells, thereby inhibiting their ability to proliferate and forcing them to die. By precisely directing high-energy radiation at tumors, radiation therapy can effectively shrink or destroy malignant growths.

In contrast, the other options describe different medical processes. One option refers to methods used for visualizing internal organs, which is typical in diagnostic imaging practices such as X-rays, CT scans, or MRIs. Another option mentions the use of sound waves, which refers to ultrasound imaging, commonly employed for various examinations without involving radiation. Lastly, a choice related to diagnostic imaging emphasizes techniques like bone scans or other imaging used to assist in diagnosis rather than treatment. Thus, the essence of radiation therapy distinctly lies in its intent and methodology focused on treating cancer with ionizing radiation.