Thursday, 12 January 2017

Srs Treatment in Delhi

Srs Treatment in Delhi

Brain Tumors Primary brain tumors
» Tumors that originate in the brain
– Malignant (cancerous) or benign Metastatic brain tumors
» Malignant cells have spread from elsewhere

History of Linear Accelerator

Based Radiosurgery Early reports of linac-based radiosurgery
with stereotactic frames in 1980’s Winston and Lutz published their results
from Joint Center for Radiation Therapy in Boston in 1986
Early linac treatments required attachment of circular collimators to standard linacs
Some relied on inherent precision of the linac, others used high precision floor
mounts, Radionics, Leibinger and Fischer, Philips,
others began commercial distribution of add-on accessories in 1990s

Accuray CyberKnife: Robotic Arm and 6MV Linac

Industrial robot arm with 6MV. Xband linac.
Two orthogonal ceiling mounted. X-rays with floor mounted flat panel detectors
Infrared. positioning Extracrania capability

Recommendations for New Radiosurgery Programs: 

 Rigorous acceptance testing of new
Detailed small field dosimetry by Qualified Medical Physicist
Detailed investigation of accuracy and limitations of all imaging equipment:
CT, MR, angio
Careful examination of all systematic errors
Rigorous training for all staff members

Failures of Quality Assurance

U.S. NRC issued NUREG “Medical Misadministrations Caused by Human Errors in Gamma Stereotactic
Radiosurgery” in 1993 Listed 15 known misadministration reports: wrong
helmet, wrong coordinates, wrong side, wrong patient, shots repeated or skipped, failure to enter
intended radiation dose (treated w nominal dose)
Gamma Knife Center reported to CDRH accidental administration up to 52% overdose to 
77 patients in 2004-2005 due to miscalibration
Linac radiosurgery center in Florida mistakenly loaded wrong factor in initial calibration, accidentally
over-dosed 10 patients Death reported to FDA in Sep 2006 from linac
radiosurgery: failure to attach accessory cone mount


The problem with radiotherapy is… We are treating something we can’t see with
something we can’t see!
Need to know where the target is relative to something we can see
Stereotactic techniques utilize a visible reference frame that is fixed relative to the
» Traditionally a frame screwed to the head
» Can also be an image whose location is
known relative to the treatment machine

MRI Image Distortion Problems

Image distortions of up to 9mm reported Some sequences notorious: particularly
coronal or axial acquisitions
MRI image problems extremely scanner dependent
Some scanners exhibit severe metal artifacts
Vital to work with MRI expert and manufacturers engineer

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