Details

Autor(en) / Beteiligte

• Grills, Inga S., M.D
• Hugo, Geoffrey, Ph.D
• Kestin, Larry L., M.D
• Galerani, Ana Paula, M.D
• Chao, K. Kenneth, M.D
• Wloch, Jennifer, R.T.T
• Yan, Di, D.Sc

Titel

Image-Guided Radiotherapy via Daily Online Cone-Beam CT Substantially Reduces Margin Requirements for Stereotactic Lung Radiotherapy

Ist Teil von

• International journal of radiation oncology, biology, physics, 2008-03, Vol.70 (4), p.1045-1056

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

2008

Quelle

MEDLINE

Beschreibungen/Notizen

• Purpose To determine treatment accuracy and margins for stereotactic lung radiotherapy with and without cone-beam CT (CBCT) image guidance. Methods and Materials Acquired for the study were 308 CBCT of 24 patients with solitary peripheral lung tumors treated with stereotactic radiotherapy. Patients were immobilized in a stereotactic body frame (SBF) or alpha-cradle and treated with image guidance using daily CBCT. Four (T1) or five (T2/metastatic) 12-Gy fractions were prescribed to the planning target volume (PTV) edge. The PTV margin was ≥5 mm depending on a pretreatment estimate of tumor excursion. Initial daily setup was according to SBF coordinates or tattoos for alpha-cradle cases. A CBCT was performed and registered to the planning CT using soft tissue registration of the target. The initial setup error/precorrection position, was recorded for the superior–inferior, anterior–posterior, and medial–lateral directions. The couch was adjusted to correct the tumor positional error. A second CBCT verified tumor position after correction. Patients were treated in the corrected position after the residual errors were ≤2 mm. A final CBCT after treatment assessed intrafraction tumor displacement. Results The precorrection systematic (Σ) and random errors (σ) for the population ranged from 2–3 mm for SBF and 2–6 mm for alpha-cradle patients; postcorrection errors ranged from 0.4–1.0 mm. Calculated population margins were 9 to 13 mm (SBF) and 10–14 mm (cradle) precorrection, 1–2 mm (SBF), and 2–3 mm (cradle) postcorrection, and 2–4 mm (SBF) and 2–5 mm (cradle) posttreatment. Conclusions Setup for stereotactic lung radiotherapy using a SBF or alpha-cradle alone is suboptimal. CBCT image guidance significantly improves target positioning and substantially reduces required target margins and normal tissue irradiation.