Delia Ciardo1, Daniela Alterio2, Barbara Alicja Jereczek-Fossa3, Marco Riboldi4, Dario Zerini2, Luigi Santoro5, Eleonora Preve2, Elena Rondi6, Stefania Comi6, Flavia Serafini2, Antonio Laudati2, Mohssen Ansarin7, Lorenzo Preda8, Guido Baroni4, Roberto Orecchia3. 1. Division of Radiation Oncology, European Institute of Oncology, via Ripamonti 435, Milano 20141, Italy. Electronic address: delia.ciardo@ieo.it. 2. Division of Radiation Oncology, European Institute of Oncology, via Ripamonti 435, Milano 20141, Italy. 3. Division of Radiation Oncology, European Institute of Oncology, via Ripamonti 435, Milano 20141, Italy; Department of Health Sciences, University of Milan, via Festa del Perdono 7, Milano 20122, Italy. 4. Dipartimento di Elettronica, Informazione e Bioingegneria (DEIB), Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, Italy; Centro Nazionale di Adroterapia Oncologica (CNAO), Strada Campeggi 53, Pavia 27100, Italy. 5. Division of Epidemiology and Biostatistics, European Institute of Oncology, via Ripamonti 435, 20141 Milano, Italy. 6. Unit of Medical Physics, European Institute of Oncology, via Ripamonti 435, 20141 Milano, Italy. 7. Division of Head and Neck Surgery, European Institute of Oncology, via Ripamonti 435, 20141 Milano, Italy. 8. Department of Radiology, European Institute of Oncology, via Ripamonti 435, 20141 Milano, Italy.
Abstract
OBJECTIVES: To compare the patient set-up error detection capabilities of three-dimensional cone beam computed tomography (3D-CBCT) and two-dimensional orthogonal kilovoltage (2D-kV) techniques. METHODS: 3D-CBCT and 2D-kV projections were acquired on 29 head-and-neck (H&N) patients undergoing Intensity Modulated Radiotherapy (IMRT) on the first day of treatment (time 0) and after the delivery of 40 Gy and 50 Gy. Set-up correction vectors were analyzed after fully automatic image registration as well as after revision by radiation oncologists. The dosimetric effects of the different sensitivities of the two image guidance techniques were assessed. RESULTS: A statistically significant correlation among detected set-up deviations by the two techniques was found along anatomical axes (0.60 < ρ < 0.72, p < 0.0001); no correlation was found for table rotation (p = 0.41). No evidence of statistically significant differences between the indications provided along the course of the treatment was found; this was also the case when full automatic versus manually refined correction vectors were compared. The dosimetric effects analysis revealed slight statistically significant differences in the median values of the maximum relative dose to mandible, spinal cord and its 5 mm Planning Organ at Risk Volume (0.95%, 0.6% and 2.45%, respectively), with higher values (p < 0.01) observed when 2D-kV corrections were applied. CONCLUSION: A similar sensitivity to linear set-up errors was observed for 2D-kV and 3D-CBCT image guidance techniques in our H&N patient cohort. Higher rotational deviations around the table vertical axis were detected by the 3D-CBCT with respect to the 2D-kV method, leading to a consistent better sparing of organs at risk.
OBJECTIVES: To compare the patient set-up error detection capabilities of three-dimensional cone beam computed tomography (3D-CBCT) and two-dimensional orthogonal kilovoltage (2D-kV) techniques. METHODS: 3D-CBCT and 2D-kV projections were acquired on 29 head-and-neck (H&N) patients undergoing Intensity Modulated Radiotherapy (IMRT) on the first day of treatment (time 0) and after the delivery of 40 Gy and 50 Gy. Set-up correction vectors were analyzed after fully automatic image registration as well as after revision by radiation oncologists. The dosimetric effects of the different sensitivities of the two image guidance techniques were assessed. RESULTS: A statistically significant correlation among detected set-up deviations by the two techniques was found along anatomical axes (0.60 < ρ < 0.72, p < 0.0001); no correlation was found for table rotation (p = 0.41). No evidence of statistically significant differences between the indications provided along the course of the treatment was found; this was also the case when full automatic versus manually refined correction vectors were compared. The dosimetric effects analysis revealed slight statistically significant differences in the median values of the maximum relative dose to mandible, spinal cord and its 5 mm Planning Organ at Risk Volume (0.95%, 0.6% and 2.45%, respectively), with higher values (p < 0.01) observed when 2D-kV corrections were applied. CONCLUSION: A similar sensitivity to linear set-up errors was observed for 2D-kV and 3D-CBCT image guidance techniques in our H&N patient cohort. Higher rotational deviations around the table vertical axis were detected by the 3D-CBCT with respect to the 2D-kV method, leading to a consistent better sparing of organs at risk.