Image-guided radiotherapy using megavoltage cone-beam computed tomography for treatment of paraspinous tumors in the presence of orthopedic hardware.
OBJECTIVE
This report describes a new image-guided radiotherapy (IGRT) technique using megavoltage cone-beam computed tomography (MV-CBCT) to treat paraspinous tumors in the presence of orthopedic hardware.


METHODS
A patient with a resected paraspinous high-grade sarcoma was treated to 59.4 Gy with an IMRT plan. Daily MV-CBCT imaging was used to ensure accurate positioning. The displacement between MV-CBCT and planning CT images were determined daily and applied remotely to the treatment couch. The dose-volume histograms of the original and a hypothetical IMRT plan (shifted by the average daily setup errors) were compared to estimate the impact on dosimetry.


RESULTS
The mean setup corrections in the lateral, longitudinal, and vertical directions were 3.6 mm (95% CI, 2.6-4.6 mm), 4.1 mm (95% CI, 3.2-5.0 mm), and 1.0 mm (95% CI, 0.6-1.3 mm), respectively. Without corrected positioning, the dose to 0.1 cc of the spinal cord increased by 9.4 Gy, and the doses to 95% of clinical target volumes 1 and 2 were reduced by 4 Gy and 4.8 Gy, respectively.


CONCLUSIONS
Megavoltage-CBCT provides a new alternative image-guided radiotherapy approach for treatment of paraspinous tumors in the presence of orthopedic hardware by providing 3D anatomic information in the treatment position, with clear imaging of metallic objects and without compromising soft-tissue information.
Hansen
Eric K
EK
Department of Radiation Oncology, University of California San Francisco, San Francisco, CA 94115, USA.
Larson
David A
DA
Aubin
Michele
M
Chen
Josephine
J
Descovich
Martina
M
Gillis
Amy M
AM
Morin
Olivier
O
Xia
Ping
P
Pouliot
Jean
J
D005260:Female; D006801:Humans; D007796:Laminectomy; D008875:Middle Aged; D009989:Orthotic Devices; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012509:Sarcoma / Q000532:radiotherapy* / Q000556:secondary / Q000601:surgery; D013117:Spinal Cord Compression / Q000601:surgery; D013125:Spinal Neoplasms / Q000532:radiotherapy* / Q000556:secondary / Q000601:surgery; D013130:Spinal Stenosis / Q000601:surgery; D013904:Thoracic Vertebrae; D014057:Tomography, X-Ray Computed / Q000379:methods