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Verification techniques and dose distribution for computed tomographic planned supine craniospinal radiation therapy
Eric L Chang1, Pei Fong Wong, Kenneth M Forster
1Division of Radiation Oncology, The University of Texas M D Anderson Cancer Center, Houston, TX 77030, USA. echang@mdanderson.org
Summary
This study introduces a modified 3-field technique for craniospinal irradiation (CSI), verifying its accuracy using rulers and film phantom measurements. The described methods enable safe CSI without direct junction visualization, despite increased stochastic error in the supine position.
Area of Science:
- Radiation Oncology
- Medical Physics
Background:
- Craniospinal irradiation (CSI) requires precise alignment of cranial and spinal fields.
- Accurate junctional dose delivery is critical to minimize toxicity and ensure treatment efficacy.
Purpose of the Study:
- To describe and evaluate a modified 3-field technique for CSI using opposed cranial and single spinal fields.
- To assess the accuracy and safety of this technique through pre-treatment and treatment verification methods.
Main Methods:
- A modified 3-field technique with opposed cranial fields and a single spinal field was designed.
- Pre-treatment verification included orthogonal ruler visualization and film phantom measurements.
- Treatment verification utilized posterior-anterior (PA) portal films, radiopaque wire, and a record-and-verify system.
Main Results:
- Systematic error was -0.5 mm (underlap), with a stochastic error standard deviation of 5.39 mm.
- Dose at the craniospinal junction ranged from 89.3% to 108% with junction shifts.
- The technique allowed for CSI without direct visualization of the craniospinal junction.
Conclusions:
- The described verification methods support safe craniospinal irradiation (CSI) without direct junction visualization.
- Rigorous film verification may reduce systematic error, but supine positioning might increase stochastic error compared to prone CSI.