Use of three-dimensional ultrasound in the detection of breast tumor bed displacement during radiotherapy.
OBJECTIVE
To evaluate the feasibility and usefulness of a three-dimensional ultrasound (3D-US) image-guided system in identifying and tracking the tumor bed (TB) for planning and daily localization before radiation delivery for breast cancer.


METHODS
Twenty breast cancer patients underwent two CT scans at the time of simulation and just before their boost. Three-dimensional ultrasound images were acquired immediately after the CT scans, to which the images were automatically fused. Three-dimensional ultrasound images were also acquired immediately before treatment. Spatial and temporal TB differences between CT and US were evaluated.


RESULTS
The TB was not visible on US and CT in 1 subject who had and 1 subject who had not received chemotherapy before whole-breast radiotherapy. The mean (SD) TB volume overlap was 78% (14%). The mean centroid position of the TB on CT vs. US differed by 0.1, 0.2, and 0.4 mm in the anterior-posterior, left-right, and superior-inferior directions. The mean (SD) absolute radial displacement of the TB on each fraction from the treatment plan was 10.8 (6.3) mm.


CONCLUSIONS
The TB was well visualized by US for the majority of patients. Clinically insignificant differences in the displacements calculated by paired CT vs. paired US demonstrate the feasibility of using 3D-US. The present study suggests that a 10-mm planning target volume margin could result in undercoverage of the clinical target volumes in 50% of treatments. Multimodality planning and image-guided radiotherapy with US potentially offers an accurate and non-ionizing solution for the daily definition of the TB position during partial-breast irradiation and boost treatments.
Wong
Philip
P
Department of Radiation Oncology, McGill University Health Centre, Montreal, Quebec, Canada.
Muanza
Thierry
T
Reynard
Eric
E
Robert
Karine
K
Barker
Jennifer
J
Sultanem
Khalil
K
D000970:Antineoplastic Agents / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D009068:Movement; D056888:Patient Positioning; D014057:Tomography, X-Ray Computed / Q000379:methods; D047368:Tumor Burden; D014463:Ultrasonography
D000970:Antineoplastic Agents