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Craniospinal RT



Compensation for Spinal Cord Depths PRONE

Spinal cord varies in depth below the surface.  Patient positioning helps - but cord always deeper at neck vs sacrum.

Compensation in planning needed if dose variation is > 5%.  A compensation technique is used to improve the non-uniform dose distribution at the spinal cord caused by varying depth, and tissue inhomogeneity. 

Custom dose compensator defined along surface of anterior spine

    • Each individual patient has his/her CT of spine which defines the depths at multiple points along the spine of that patient
    • Based on those depths - a computer program calculates the compensation necessary to get the most homogeneous dose distribution across these points
    • A compensator is milled in styrofoam based on  these calculations
    • The styrofoam mould is filled with 2.5mm diameter stainless steel granules
    • This is inserted onto LINAC machine for each individual patient
    • Each patient compensator is verified with film and ionization chamber measurements.












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