Comparison of Different Strategies to Use Four-Dimensional Computed Tomography in Treatment Planning for Lung Cancer Patients

Journal Article · Sat Mar 15 04:00:00 EDT 2008 · International Journal of Radiation Oncology, Biology and Physics

DOI:https://doi.org/10.1016/j.ijrobp.2007.11.042· OSTI ID:21039848

Wolthaus, Jochem W.H.; Sonke, Jan-Jakob; Herk, Marcel van; Belderbos, Jose; Rossi, Maddalena M.G.; Lebesque, Joos V ^[1]

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1. Department of Radiation Oncology, Netherlands Cancer Institute - Antoni van Leeuwenhoek Hospital, Amsterdam (Netherlands)

Purpose: To discuss planning target volumes (PTVs) based on internal target volume (PTV{sub ITV}), exhale-gated radiotherapy (PTV{sub Gating}), and a new proposed midposition (PTV{sub MidP}; time-weighted mean tumor position) and compare them with the conventional free-breathing CT scan PTV (PTV{sub Conv}). Methods and Materials: Respiratory motion induces systematic and random geometric uncertainties. Their contribution to the clinical target volume (CTV)-to-PTV margins differs for each PTV approach. The uncertainty margins were calculated using a dose-probability-based margin recipe (based on patient statistics). Tumor motion in four-dimensional CT scans was determined using a local rigid registration of the tumor. Geometric uncertainties for interfractional setup errors and tumor baseline variation were included. For PTV{sub Gating}, the residual motion within a 30% gating (time) window was determined. The concepts were evaluated in terms of required CTV-to-PTV margin and PTV volume for 45 patients. Results: Over the patient group, the PTV{sub ITV} was on average larger (+6%) and the PTV{sub Gating} and PTV{sub MidP} smaller (-10%) than the PTV{sub Conv} using an off-line (bony anatomy) setup correction protocol. With an on-line (soft tissue) protocol the differences in PTV compared with PTV{sub Conv} were +33%, -4%, and 0, respectively. Conclusions: The internal target volume method resulted in a significantly larger PTV than conventional CT scanning. The exhale-gated and mid-position approaches were comparable in terms of PTV. However, mid-position (or mid-ventilation) is easier to use in the clinic because it only affects the planning part of treatment and not the delivery.

• OSTI ID: 21039848
• Journal Information: International Journal of Radiation Oncology, Biology and Physics, Journal Name: International Journal of Radiation Oncology, Biology and Physics Journal Issue: 4 Vol. 70; ISSN IOBPD3; ISSN 0360-3016
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
ANATOMY
CARCINOMAS
COMPARATIVE EVALUATIONS
COMPUTERIZED TOMOGRAPHY
CORRECTIONS
ERRORS
LUNGS
PATIENTS
PLANNING
RADIATION DOSES
RADIOTHERAPY
RESPIRATION
STATISTICS