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Title: SU-F-T-449: Dosimetric Comparison of Acuros XB, Adaptive Convolve in Intensity Modulated Radiotherapy for Head and Neck Cancer

Abstract

Purpose: There have been several publications focusing on dose calculation in lung for a new dose calculation algorithm of Acuros XB (AXB). AXB could contribute to dose calculation for high-density media for bone and dental prosthesis rather than in lung. We compared the dosimetric performance of AXB, Adaptive Convolve (AC) in head and neck IMRT plans. Methods: In a phantom study, the difference in depth profile between AXB and AC was evaluated using Kodak EDR2 film sandwiched with tough water phantoms. 6 MV x-ray using the TrueBeam was irradiated. In a patient study, 20 head and neck IMRT plans had been clinically approved in Pinnacle3 and were transferred to Eclipse. Dose distribution was recalculated using AXB in Eclipse while maintaining AC-calculated monitor units and MLC sequence planned in Pinnacle. Subsequently, both the dose-volumetric data obtained using the two different calculation algorithms were compared. Results: The results in the phantom evaluation for the shallow area ahead of the build-up region shows over-dose for AXB and under-dose for AC, respectively. In the patient plans, AXB shows more hot spots especially around the high-density media than AC in terms of PTV (Max difference: 4.0%) and OAR (Max. difference: 1.9%). Compared to AC, theremore » were larger dose deviations in steep dose gradient region and higher skin-dose. Conclusion: In head and neck IMRT plans, AXB and AC show different dosimetric performance for the regions inside the target volume around high-density media, steep dose gradient regions and skin-surface. There are limitations in skin-dose and complex anatomic condition using even inhomogeneous anthropomorphic phantom Thus, there is the potential for an increase of hot-spot in AXB, and an underestimation of dose in substance boundaries and skin regions in AC.« less

Authors:
 [1];  [2]
  1. National Cancer Center Hospital East, Kashiwa, Chiba (Japan)
  2. National Cancer Center, Kashiwa, Chiba (Japan)
Publication Date:
OSTI Identifier:
22649040
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; HEAD; HOT SPOTS; NECK; PHANTOMS; RADIATION DOSE DISTRIBUTIONS; RADIOTHERAPY; X RADIATION

Citation Formats

Uehara, R, and Tachibana, H. SU-F-T-449: Dosimetric Comparison of Acuros XB, Adaptive Convolve in Intensity Modulated Radiotherapy for Head and Neck Cancer. United States: N. p., 2016. Web. doi:10.1118/1.4956634.
Uehara, R, & Tachibana, H. SU-F-T-449: Dosimetric Comparison of Acuros XB, Adaptive Convolve in Intensity Modulated Radiotherapy for Head and Neck Cancer. United States. doi:10.1118/1.4956634.
Uehara, R, and Tachibana, H. 2016. "SU-F-T-449: Dosimetric Comparison of Acuros XB, Adaptive Convolve in Intensity Modulated Radiotherapy for Head and Neck Cancer". United States. doi:10.1118/1.4956634.
@article{osti_22649040,
title = {SU-F-T-449: Dosimetric Comparison of Acuros XB, Adaptive Convolve in Intensity Modulated Radiotherapy for Head and Neck Cancer},
author = {Uehara, R and Tachibana, H},
abstractNote = {Purpose: There have been several publications focusing on dose calculation in lung for a new dose calculation algorithm of Acuros XB (AXB). AXB could contribute to dose calculation for high-density media for bone and dental prosthesis rather than in lung. We compared the dosimetric performance of AXB, Adaptive Convolve (AC) in head and neck IMRT plans. Methods: In a phantom study, the difference in depth profile between AXB and AC was evaluated using Kodak EDR2 film sandwiched with tough water phantoms. 6 MV x-ray using the TrueBeam was irradiated. In a patient study, 20 head and neck IMRT plans had been clinically approved in Pinnacle3 and were transferred to Eclipse. Dose distribution was recalculated using AXB in Eclipse while maintaining AC-calculated monitor units and MLC sequence planned in Pinnacle. Subsequently, both the dose-volumetric data obtained using the two different calculation algorithms were compared. Results: The results in the phantom evaluation for the shallow area ahead of the build-up region shows over-dose for AXB and under-dose for AC, respectively. In the patient plans, AXB shows more hot spots especially around the high-density media than AC in terms of PTV (Max difference: 4.0%) and OAR (Max. difference: 1.9%). Compared to AC, there were larger dose deviations in steep dose gradient region and higher skin-dose. Conclusion: In head and neck IMRT plans, AXB and AC show different dosimetric performance for the regions inside the target volume around high-density media, steep dose gradient regions and skin-surface. There are limitations in skin-dose and complex anatomic condition using even inhomogeneous anthropomorphic phantom Thus, there is the potential for an increase of hot-spot in AXB, and an underestimation of dose in substance boundaries and skin regions in AC.},
doi = {10.1118/1.4956634},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = 2016,
month = 6
}
  • Purpose: To compare differences in dosimetric, clinical, and quality-of-life endpoints among a cohort of patients treated by intensity-modulated radiotherapy (IMRT) and conventional radiotherapy (CRT) for head-and-neck cancer of unknown primary origin. Methods and Materials: The medical records of 51 patients treated by radiation therapy for squamous cell carcinoma of the head and neck presenting as cervical lymph node metastasis of occult primary origin were reviewed. Twenty-four patients (47%) were treated using CRT, and 27 (53%) were treated using IMRT. The proportions of patients receiving concurrent chemotherapy were 54% and 63%, respectively. Results: The 2-year estimates of overall survival, local-regional control,more » and disease-specific survival for the entire patient population were 86%, 89%, and84%, respectively. There were no significant differences in any of these endpoints with respect to radiation therapy technique (p > 0.05 for all). Dosimetric analysis revealed that the use of IMRT resulted in significant improvements with respect to mean dose and V30 to the contralateral (spared) parotid gland. In addition, mean doses to the ipsilateral inner and middle ear structures were significantly reduced with IMRT (p < 0.05 for all). The incidence of severe xerostomia in the late setting was 58% and 11% among patients treated by CRT and IMRT, respectively (p < 0.001). The percentages of patients who were G-tube dependent at 6 months after treatment were 42% and 11%, respectively (p < 0.001). Conclusions: IMRT results in significant improvements in the therapeutic ratio among patients treated by radiation therapy for head-and-neck cancer of unknown primary origin.« less
  • Purpose: The authors evaluated the effects of multileaf collimator (MLC) leaf width (2.5 vs. 5 mm) on dosimetric parameters and delivery efficiencies of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) for head and neck (H and N) cancers. Methods: The authors employed two types of mock phantoms: large-sized head and neck (LH and N) and small-sized C-shape (C-shape) phantoms. Step-and-shoot IMRT (S and S-IMRT) and VMAT treatment plans were designed with 2.5- and 5.0-mm MLC for both C-shape and LH and N phantoms. Their dosimetric characteristics were compared in terms of the conformity index (CI) and homogeneity indexmore » (HI) for the planning target volume (PTV), the dose to organs at risk (OARs), and the dose-spillage volume. To analyze the effects of the field and arc numbers, 9-field IMRT (9F-IMRT) and 13-field IMRT (13F-IMRT) plans were established for S and S-IMRT. For VMAT, single arc (VMAT{sub 1}) and double arc (VMAT{sub 2}) plans were established. For all plans, dosimetric verification was performed using the phantom to examine the relationship between dosimetric errors and the two leaf widths. Delivery efficiency of the two MLCs was compared in terms of beam delivery times, monitor units (MUs) per fraction, and the number of segments for each plan. Results: 2.5-mm MLC showed better dosimetric characteristics in S and S-IMRT and VMAT for C-shape, providing better CI for PTV and lower spinal cord dose and high and intermediate dose-spillage volume as compared with the 5-mm MLC (p < 0.05). However, no significant dosimetric benefits were provided by the 2.5-mm MLC for LH and N (p > 0.05). Further, beam delivery efficiency was not observed to be significantly associated with leaf width for either C-shape or LH and N. However, MUs per fraction were significantly reduced for the 2.5-mm MLC for the LH and N. In dosimetric error analysis, absolute dose evaluations had errors of less than 3%, while the Gamma passing rate was greater than 95% according to the 3%/3 mm criteria. There were no significant differences in dosimetric error between the 2.5- and 5-mm MLCs. Conclusions: As compared with MLC of 5-mm leaf widths, MLC with finer leaf width (2.5-mm) can provide better dosimetric outcomes in IMRT for C-shape. However, the MLC leaf width may only have minor effects on dosimetric characteristics in IMRT for LH and N. The results of the present study will serve as a useful assessment standard when assigning or introducing equipment for the treatment of H and N cancers.« less
  • Purpose: The authors evaluated the effects of multileaf collimator (MLC) leaf width (2.5 vs. 5 mm) on dosimetric parameters and delivery efficiencies of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) for head and neck (H and N) cancers. Methods: The authors employed two types of mock phantoms: large-sized head and neck (LH and N) and small-sized C-shape (C-shape) phantoms. Step-and-shoot IMRT (S and S-IMRT) and VMAT treatment plans were designed with 2.5- and 5.0-mm MLC for both C-shape and LH and N phantoms. Their dosimetric characteristics were compared in terms of the conformity index (CI) and homogeneity indexmore » (HI) for the planning target volume (PTV), the dose to organs at risk (OARs), and the dose-spillage volume. To analyze the effects of the field and arc numbers, 9-field IMRT (9F-IMRT) and 13-field IMRT (13F-IMRT) plans were established for S and S-IMRT. For VMAT, single arc (VMAT{sub 1}) and double arc (VMAT{sub 2}) plans were established. For all plans, dosimetric verification was performed using the phantom to examine the relationship between dosimetric errors and the two leaf widths. Delivery efficiency of the two MLCs was compared in terms of beam delivery times, monitor units (MUs) per fraction, and the number of segments for each plan. Results: 2.5-mm MLC showed better dosimetric characteristics in S and S-IMRT and VMAT for C-shape, providing better CI for PTV and lower spinal cord dose and high and intermediate dose-spillage volume as compared with the 5-mm MLC (p < 0.05). However, no significant dosimetric benefits were provided by the 2.5-mm MLC for LH and N (p > 0.05). Further, beam delivery efficiency was not observed to be significantly associated with leaf width for either C-shape or LH and N. However, MUs per fraction were significantly reduced for the 2.5-mm MLC for the LH and N. In dosimetric error analysis, absolute dose evaluations had errors of less than 3%, while the Gamma passing rate was greater than 95% according to the 3%/3 mm criteria. There were no significant differences in dosimetric error between the 2.5- and 5-mm MLCs. Conclusions: As compared with MLC of 5-mm leaf widths, MLC with finer leaf width (2.5-mm) can provide better dosimetric outcomes in IMRT for C-shape. However, the MLC leaf width may only have minor effects on dosimetric characteristics in IMRT for LH and N. The results of the present study will serve as a useful assessment standard when assigning or introducing equipment for the treatment of H and N cancers.« less
  • Purpose: To assess the benefit of intensity-modulated radiotherapy (IMRT) compared with conventional RT for the quality of life (QOL) of head and neck cancer survivors. Methods and Materials: Cross-sectional QOL measures (European Organization for Research and Treatment of Cancer QOL questionnaire C30 and head and neck cancer module) were used with a French multicenter cohort of patients cured of head and neck cancer (follow-up {>=} 1 year) who had received bilateral neck RT ({>=} 45 Gy) as a part of their initial treatment. We compared the QOL mean scores regarding RT modality (conventional RT vs. IMRT). The patients of themore » two groups were matched (one to one) according to the delay between the end of RT and the timing of the QOL evaluation and the T stage. Each QOL item was divided into two relevant levels of severity: 'not severe' (responses, 'not at all' and 'a little') vs. 'severe' (responses 'quite a bit' and 'very much'). The association between the type of RT and the prevalence of severe symptoms was approximated, through multivariate analysis using the prevalence odds ratio. Results: Two comparable groups (67 pairs) were available. Better scores were observed on the head and neck cancer module QOL questionnaire for the IMRT group, especially for dry mouth and sticky saliva (p < 0.0001). Severe symptoms were more frequent with conventional RT concerning saliva modifications and oral discomfort. The adjusted prevalence odds ratios were 3.17 (p = 0.04) for dry mouth, 3.16 (p = 0.02) for sticky saliva, 3.58 (p = 0.02) for pain in the mouth, 3.35 (p = 0.04) for pain in the jaw, 2.60 (p = 0.02) for difficulties opening the mouth, 2.76 (p = 0.02) for difficulties with swallowing, and 2.68 (p = 0.03) for trouble with eating. Conclusion: The QOL assessment of head and neck cancer survivors demonstrated the benefit of IMRT, particularly in the areas of salivary dysfunction and oral discomfort.« less
  • Purpose: To compare the gross tumor volume (GTV) identified on CT to that obtained from fluorodeoxyglucose (FDG) positron emission tomography (PET) and determine the differences in volume and dose coverage of the PET-GTV when the CT-GTV is used for radiotherapy planning. Methods and Materials: A total of 40 patients with intact squamous cell carcinoma arising in the head-and-neck region underwent intensity-modulated radiotherapy (IMRT) at one department. All patients underwent CT simulation for treatment planning followed by PET-CT in the treatment position. CT simulation images were fused to the CT component of the PET-CT images. The GTV using the CT simulationmore » images was contoured (CT-GTV), as was the GTV based on the PET scan (PET-GTV). The IMRT plans were obtained using the CT-GTV. Results: The PET-GTV was smaller, the same size, and larger than the CT-GTV in 30 (75%), 3 (8%), and 7 (18%) cases respectively. The median PET-GTV and CT-GTV volume was 20.3 cm{sup 3} (range, 0.2-294) and 37.2 cm{sup 3} (range, 2-456), respectively. The volume of PET-GTV receiving at least 95% of the prescribed dose was 100% in 20 (50%), 95-99% in 10 (25%), 90-94% in 3 (8%), 85-89% in 1 (3%), 80-84% in 2 (5%), 75-79% in 1 (3%), and <75% in 3 (8%) cases. The minimal dose received by 95% of the PET-GTV was {>=}100% in 19 (48%), 95-99% in 11 (28%), 90-94% in 5 (13%), 85-89% in 2 (5%), and <75% in 3 (8%) cases. Conclusion: The PET-GTV was larger than the CT-GTV in 18% of cases. In approximately 25% of patients with intact head-and-neck cancer treated using IMRT, the volume of PET-GTV receiving at least 95% of the prescribed dose and minimal dose received by 95% of the PET-GTV were less than optimal.« less