• Progress in Medical Physics
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• v.24 no.4
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• pp.230-236
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• 2013

Our purpose is to present a novel technique for delivering craniospinal irradiation in the supine position using a perfect match, field-in-field (FIF) intrafractional feathering, and simple forward-optimization technique. To achieve this purpose, computed tomography simulation was performed with patients in the supine position. Half-beam, blocked, opposed, lateral, cranial fields with a collimator rotation were matched to the divergence of the superior border of an upper-spinal field. Fixed field parameters were used, and the isocenter of the upper-spinal field was placed at the same source-to-axis distance (SAD), 20 cm inferior to the cranial isocenter. For a lower-spinal field, the isocenter was placed 40 cm inferior to the cranial isocenter at a constant SAD. Both gantry and couch rotations for the lower-spinal field were used to achieve perfect divergence match with the inferior border of the upper-spinal field. A FIF technique was used to feather the craniospinal and spinal-spinal junction daily by varying the match line over 2 cm. The dose throughout the target volume was modulated using the FIF simple forward optimization technique to obtain homogenous coverage. Daily, image-guided therapy was used to assure and verify the setup. This supine-position, perfect match craniospinal irradiation technique with FIF intrafractional feathering and dose modulation provides a simple and safe way to deliver treatment while minimizing dose inhomogeneity.

• 대한방사선방어학회:학술대회논문집
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• 2009.11a
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• pp.128-129
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• 2009

• Radiation Oncology Journal
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• v.20 no.2
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• pp.165-171
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• 2002

Purpose : In order to perform craniospinal irradiation (CSI) in the supine position on patients who are unable to lie in the prone position, a new simulation technique using a CT simulator was developed and its availability was evaluated. Materials and Method : A CT simulator and a 3-D conformal treatment planning system were used to develop CSI in the supine position. The head and neck were immobilized with a thermoplastic mask in the supine position and the entire body was immobilized with a Vac-Loc. A volumetrie image was then obtained using the CT simulator. In order to improve the reproducibility of the patients' setup, datum lines and points were marked on the head and the body. Virtual fluoroscopy was peformed with the removal of visual obstacles such as the treatment table or the immobilization devices. After the virtual simulation, the treatment isocenters of each field were marked on the body and the immobilization devices at the conventional simulation room. Each treatment field was confirmed by comparing the fluoroscopy images with the digitally reconstructed radiography (DRR)/digitally composite radiography (DCR) images from the virtual simulation. The port verification films from the first treatment were also compared with the DRR/DCR images for a geometrical verification. Results : CSI in the supine position was successfully peformed in 9 patients. It required less than 20 minutes to construct the immobilization device and to obtain the whole body volumetric images. This made it possible to not only reduce the patients' inconvenience, but also to eliminate the position change variables during the long conventional simulation process. In addition, by obtaining the CT volumetric image, critical organs, such as the eyeballs and spinal cord, were better defined, and the accuracy of the port designs and shielding was improved. The differences between the DRRs and the portal films were less than 3 mm in the vertebral contour. Conclusion : CSI in the supine position is feasible in patients who cannot lie on prone position, such as pediatric patienta under the age of 4 years, patients with a poor general condition, or patients with a tracheostomy.