Page 19 - Essentia Vol 5 Issue 1

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Stereotactic

Radiosurgery

Dr Thamizholi Selvaraju (SRS)
Senior Consultant
Radiation Oncologist
Barpeta Cancer Centre

Introduction intersection (the isocentre), the cumulative
energy delivers a lethal dose to the target.
tereotactic Radiosurgery (SRS) is a highly
precise, non-invasive form of radiation Ê Biological Effect: High-intensity radiation
Stherapy used for selected tumours and breaks the double-stranded DNA of targeted
functional abnormalities of the brain and spine. cells, preventing replication and causing the
lesion to shrink or stabilise over time.
Despite the term “surgery”, it involves no incision,
scalpel or general anaesthesia. Using advanced Primary delivery platforms
3D neuroimaging, SRS delivers a high-intensity
dose of focused radiation to a defined lesion Three main technological systems are used to
while minimising exposure to surrounding healthy administer SRS:
structures. 1. Gamma Knife: Uses fixed cobalt-60
radioactive sources. It is highly specialised

Core mechanism of action for small-to-medium intracranial targets and
usually requires a rigid, pin-based head frame.
Unlike conventional fractionated radiation therapy,
which delivers smaller doses over several weeks, 2. Linear Accelerator (LINAC): Generates high-
energy X-rays. Systems such as Varian True
SRS achieves an “ablative” effect in 1–5 sessions. Beam or Cyber Knife use robotic arms and
Ê Spatial Convergence: Dozens of low-dose real-time image guidance, allowing frameless
radiation beams are directed from multiple treatment.
angles toward a single 3D coordinate point. 3. Proton Beam Therapy: Uses charged particles

Ê Summation Effect: Each individual beam instead of photons. Protons exhibit the “Bragg
passes safely through healthy tissue with Peak”, with energy falling off immediately
minimal damage. At the exact point of after reaching the target depth.

Clinical indications

Clinical Category Target Pathology Treatment Goal

Malignant Tumours Brain metastases, recurrent gliomas Local tumour control, symptom relief

Benign Tumours Acoustic neuromas, meningiomas, Growth cessation, nerve preservation
pituitary adenomas

Vascular Lesions Arteriovenous Malformations (AVMs) Vessel obliteration, stroke prevention
Functional Disorders Trigeminal neuralgia, essential tremor Disrupting faulty neurological pathways

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