Which of the following are examples of radiosurgery modalities?

• A. Gamma Knife and CyberKnife
• B. Craniotomy and Endoscopy
• C. Biopsy and Radiotherapy
• D. PET and SPECT

Answer: (A)

Radiosurgery modalities are non-invasive, image-guided radiation therapies that deliver a very high dose to a small target with sharp dose fall-off, usually in a single session or in just a few fractions. Gamma Knife and CyberKnife fit this description because they deliver tightly focused radiation without opening the skull, aiming precisely at the lesion.

Gamma Knife uses numerous cobalt-60 sources arranged in a helmet-like configuration to converge beams on the target, achieving high precision with minimal exposure to surrounding tissue. CyberKnife employs a robotic arm and real-time imaging to track movement and adjust the beams from many angles, providing flexible, highly conformal coverage.

The other options involve procedures or modalities that are not radiosurgery. Craniotomy and Endoscopy are surgical procedures that physically access the brain or cavities. Biopsy is a diagnostic procedure, and Radiotherapy, while related, refers to broader external beam or internal radiotherapy not specifically the single-session, highly focused approach of radiosurgery. PET and SPECT are imaging tests, not treatment modalities.