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Dosimetric effects of adaptive prostate cancer radiotherapy in an MR-linac workflow.
Radiat Oncol. 2020 Jul 10; 15(1):168.RO

Abstract

BACKGROUND

The purpose was to evaluate the dosimetric effects in prostate cancer treatment caused by anatomical changes occurring during the time frame of adaptive replanning in a magnetic resonance linear accelerator (MR-linac) workflow.

METHODS

Two MR images (MR1 and MR2) were acquired with 30 min apart for each of the 35 patients enrolled in this study. The clinical target volume (CTV) and organs at risk (OARs) were delineated based on MR1. Using a synthetic CT (sCT), ultra-hypofractionated VMAT treatment plans were created for MR1, with three different planning target volume (PTV) margins of 7 mm, 5 mm and 3 mm. The three treatment plans of MR1, were recalculated onto MR2 using its corresponding sCT. The dose distribution of MR2 represented delivered dose to the patient after 30 min of adaptive replanning, omitting motion correction before beam on. MR2 was registered to MR1, using deformable registration. Using the inverse deformation, the structures of MR1 was deformed to fit MR2 and anatomical changes were quantified. For dose distribution comparison the dose distribution of MR2 was warped to the geometry MR1.

RESULTS

The mean center of mass vector offset for the CTV was 1.92 mm [0.13 - 9.79 mm]. Bladder volume increase ranged from 12.4 to 133.0% and rectum volume difference varied between -10.9 and 38.8%. Using the conventional 7 mm planning target volume (PTV) margin the dose reduction to the CTV was 1.1%. Corresponding values for 5 mm and 3 mm PTV margin were 2.0% and 4.2% respectively. The dose to the PTV and OARs also decreased from D1 to D2, for all PTV margins evaluated. Statistically significant difference was found for CTV Dmin between D1 and D2 for the 3 mm PTV margin (p < 0.01).

CONCLUSIONS

A target underdosage caused by anatomical changes occurring during the reported time frame for adaptive replanning MR-linac workflows was found. Volume changes in both bladder and rectum caused large prostate displacements. This indicates the importance of thorough position verification before treatment delivery and that the workflow needs to speed up before introducing margin reduction.

Authors+Show Affiliations

Department of Medical Radiation Physics, Lund University, Lund, Sweden. annika.mannerberg@med.lu.se.Department of Hematology, Oncology and Radiation Physics, Skåne University Hospital, Lund, Sweden. Medical Radiation Physics, Department of Translational Medicine, Lund University, Malmö, Sweden.Department of Radiation Sciences, Umeå University, Umeå, Sweden.Department of Hematology, Oncology and Radiation Physics, Skåne University Hospital, Lund, Sweden. Medical Radiation Physics, Department of Translational Medicine, Lund University, Malmö, Sweden.Department of Hematology, Oncology and Radiation Physics, Skåne University Hospital, Lund, Sweden.Department of Hematology, Oncology and Radiation Physics, Skåne University Hospital, Lund, Sweden. Medical Radiation Physics, Department of Translational Medicine, Lund University, Malmö, Sweden.Department of Medical Radiation Physics, Lund University, Lund, Sweden.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

32650811

Citation

Mannerberg, Annika, et al. "Dosimetric Effects of Adaptive Prostate Cancer Radiotherapy in an MR-linac Workflow." Radiation Oncology (London, England), vol. 15, no. 1, 2020, p. 168.
Mannerberg A, Persson E, Jonsson J, et al. Dosimetric effects of adaptive prostate cancer radiotherapy in an MR-linac workflow. Radiat Oncol. 2020;15(1):168.
Mannerberg, A., Persson, E., Jonsson, J., Gustafsson, C. J., Gunnlaugsson, A., Olsson, L. E., & Ceberg, S. (2020). Dosimetric effects of adaptive prostate cancer radiotherapy in an MR-linac workflow. Radiation Oncology (London, England), 15(1), 168. https://doi.org/10.1186/s13014-020-01604-5
Mannerberg A, et al. Dosimetric Effects of Adaptive Prostate Cancer Radiotherapy in an MR-linac Workflow. Radiat Oncol. 2020 Jul 10;15(1):168. PubMed PMID: 32650811.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Dosimetric effects of adaptive prostate cancer radiotherapy in an MR-linac workflow. AU - Mannerberg,Annika, AU - Persson,Emilia, AU - Jonsson,Joakim, AU - Gustafsson,Christian Jamtheim, AU - Gunnlaugsson,Adalsteinn, AU - Olsson,Lars E, AU - Ceberg,Sofie, Y1 - 2020/07/10/ PY - 2020/04/07/received PY - 2020/06/23/accepted PY - 2020/7/12/entrez PY - 2020/7/12/pubmed PY - 2020/7/12/medline KW - Intrafractional motion KW - MR-linac KW - Motion induced dose effects KW - Prostate radiotherapy SP - 168 EP - 168 JF - Radiation oncology (London, England) JO - Radiat Oncol VL - 15 IS - 1 N2 - BACKGROUND: The purpose was to evaluate the dosimetric effects in prostate cancer treatment caused by anatomical changes occurring during the time frame of adaptive replanning in a magnetic resonance linear accelerator (MR-linac) workflow. METHODS: Two MR images (MR1 and MR2) were acquired with 30 min apart for each of the 35 patients enrolled in this study. The clinical target volume (CTV) and organs at risk (OARs) were delineated based on MR1. Using a synthetic CT (sCT), ultra-hypofractionated VMAT treatment plans were created for MR1, with three different planning target volume (PTV) margins of 7 mm, 5 mm and 3 mm. The three treatment plans of MR1, were recalculated onto MR2 using its corresponding sCT. The dose distribution of MR2 represented delivered dose to the patient after 30 min of adaptive replanning, omitting motion correction before beam on. MR2 was registered to MR1, using deformable registration. Using the inverse deformation, the structures of MR1 was deformed to fit MR2 and anatomical changes were quantified. For dose distribution comparison the dose distribution of MR2 was warped to the geometry MR1. RESULTS: The mean center of mass vector offset for the CTV was 1.92 mm [0.13 - 9.79 mm]. Bladder volume increase ranged from 12.4 to 133.0% and rectum volume difference varied between -10.9 and 38.8%. Using the conventional 7 mm planning target volume (PTV) margin the dose reduction to the CTV was 1.1%. Corresponding values for 5 mm and 3 mm PTV margin were 2.0% and 4.2% respectively. The dose to the PTV and OARs also decreased from D1 to D2, for all PTV margins evaluated. Statistically significant difference was found for CTV Dmin between D1 and D2 for the 3 mm PTV margin (p < 0.01). CONCLUSIONS: A target underdosage caused by anatomical changes occurring during the reported time frame for adaptive replanning MR-linac workflows was found. Volume changes in both bladder and rectum caused large prostate displacements. This indicates the importance of thorough position verification before treatment delivery and that the workflow needs to speed up before introducing margin reduction. SN - 1748-717X UR - https://www.unboundmedicine.com/medline/citation/32650811/Dosimetric_effects_of_adaptive_prostate_cancer_radiotherapy_in_an_MR-linac_workflow L2 - https://ro-journal.biomedcentral.com/articles/10.1186/s13014-020-01604-5 DB - PRIME DP - Unbound Medicine ER -
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