TY - JOUR
T1 - Localization accuracy from automatic and semi-automatic rigid registration of locally-advanced lung cancer targets during image-guided radiation therapy
AU - Robertson, Scott P.
AU - Weiss, Elisabeth
AU - Hugo, Geoffrey D.
N1 - Funding Information:
The authors wish to thank Dr. Matthew Orton for assisting with delineation and Dr. Nitai Mukhopadhyay for verifying all statistical analyses. This work was partially supported by NIH R01CA116249. None of the authors has any actual or potential conflicts of interest.
PY - 2012/1
Y1 - 2012/1
N2 - Purpose: To evaluate localization accuracy resulting from rigid registration of locally-advanced lung cancer targets using fully automatic and semi-automatic protocols for image-guided radiation therapy. Methods: Seventeen lung cancer patients, fourteen also presenting with involved lymph nodes, received computed tomography (CT) scans once per week throughout treatment under active breathing control. A physician contoured both lung and lymph node targets for all weekly scans. Various automatic and semi-automatic rigid registration techniques were then performed for both individual and simultaneous alignments of the primary gross tumor volume (GTVP) and involved lymph nodes (GTVLN) to simulate the localization process in image-guided radiation therapy. Techniques included standard (direct registration of weekly images to a planning CT), seeded (manual prealignment of targets to guide standard registration), transitive-based (alignment of pretreatment and planning CTs through one or more intermediate images), and rereferenced (designation of a new reference image for registration). Localization error (LE) was assessed as the residual centroid and border distances between targets from planning and weekly CTs after registration. Results: Initial bony alignment resulted in centroid LE of 7.3 ± 5.4 mm and 5.4 ± 3.4 mm for the GTVP and GTVLN, respectively. Compared to bony alignment, transitive-based and seeded registrations significantly reduced GTVP centroid LE to 4.7 ± 3.7 mm (p = 0.011) and 4.3 ± 2.5 mm (p < 1 × 10-3), respectively, but the smallest GTVP LE of 2.4 ± 2.1 mm was provided by rereferenced registration (p < 1 × 10-6). Standard registration significantly reduced GTVLN centroid LE to 3.2 ± 2.5 mm (p < 1 × 10-3) compared to bony alignment, with little additional gain offered by the other registration techniques. For simultaneous target alignment, centroid LE as low as 3.9 ± 2.7 mm and 3.8 ± 2.3 mm were achieved for the GTVP and GTVLN, respectively, using rereferenced registration. Conclusions: Target shape, volume, and configuration changes during radiation therapy limited the accuracy of standard rigid registration for image-guided localization in locally-advanced lung cancer. Significant error reductions were possible using other rigid registration techniques, with LE approaching the lower limit imposed by interfraction target variability throughout treatment.
AB - Purpose: To evaluate localization accuracy resulting from rigid registration of locally-advanced lung cancer targets using fully automatic and semi-automatic protocols for image-guided radiation therapy. Methods: Seventeen lung cancer patients, fourteen also presenting with involved lymph nodes, received computed tomography (CT) scans once per week throughout treatment under active breathing control. A physician contoured both lung and lymph node targets for all weekly scans. Various automatic and semi-automatic rigid registration techniques were then performed for both individual and simultaneous alignments of the primary gross tumor volume (GTVP) and involved lymph nodes (GTVLN) to simulate the localization process in image-guided radiation therapy. Techniques included standard (direct registration of weekly images to a planning CT), seeded (manual prealignment of targets to guide standard registration), transitive-based (alignment of pretreatment and planning CTs through one or more intermediate images), and rereferenced (designation of a new reference image for registration). Localization error (LE) was assessed as the residual centroid and border distances between targets from planning and weekly CTs after registration. Results: Initial bony alignment resulted in centroid LE of 7.3 ± 5.4 mm and 5.4 ± 3.4 mm for the GTVP and GTVLN, respectively. Compared to bony alignment, transitive-based and seeded registrations significantly reduced GTVP centroid LE to 4.7 ± 3.7 mm (p = 0.011) and 4.3 ± 2.5 mm (p < 1 × 10-3), respectively, but the smallest GTVP LE of 2.4 ± 2.1 mm was provided by rereferenced registration (p < 1 × 10-6). Standard registration significantly reduced GTVLN centroid LE to 3.2 ± 2.5 mm (p < 1 × 10-3) compared to bony alignment, with little additional gain offered by the other registration techniques. For simultaneous target alignment, centroid LE as low as 3.9 ± 2.7 mm and 3.8 ± 2.3 mm were achieved for the GTVP and GTVLN, respectively, using rereferenced registration. Conclusions: Target shape, volume, and configuration changes during radiation therapy limited the accuracy of standard rigid registration for image-guided localization in locally-advanced lung cancer. Significant error reductions were possible using other rigid registration techniques, with LE approaching the lower limit imposed by interfraction target variability throughout treatment.
KW - image registration
KW - image-guided radiation therapy
KW - lymph nodes
KW - non-small cell lung cancer
UR - http://www.scopus.com/inward/record.url?scp=84855446777&partnerID=8YFLogxK
U2 - 10.1118/1.3671929
DO - 10.1118/1.3671929
M3 - Article
C2 - 22225303
AN - SCOPUS:84855446777
SN - 0094-2405
VL - 39
SP - 330
EP - 341
JO - Medical physics
JF - Medical physics
IS - 1
ER -