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Feasibility of MV CBCT-based treatment planning for urgent radiation therapy: dosimetric accuracy of MV CBCT-based dose calculations.
J Appl Clin Med Phys. 2015 11 08; 16(6):458-471.JA

Abstract

Unlike scheduled radiotherapy treatments, treatment planning time and resources are limited for emergency treatments. Consequently, plans are often simple 2D image-based treatments that lag behind technical capabilities available for nonurgent radiotherapy. We have developed a novel integrated urgent workflow that uses onboard MV CBCT imaging for patient simulation to improve planning accuracy and reduce the total time for urgent treatments. This study evaluates both MV CBCT dose planning accuracy and novel urgent workflow feasibility for a variety of anatomic sites. We sought to limit local mean dose differences to less than 5% compared to conventional CT simulation. To improve dose calculation accuracy, we created separate Hounsfield unit-to-density calibration curves for regular and extended field-of-view (FOV) MV CBCTs. We evaluated dose calculation accuracy on phantoms and four clinical anatomical sites (brain, thorax/spine, pelvis, and extremities). Plans were created for each case and dose was calculated on both the CT and MV CBCT. All steps (simulation, planning, setup verification, QA, and dose delivery) were performed in one 30 min session using phantoms. The monitor units (MU) for each plan were compared and dose distribution agreement was evaluated using mean dose difference over the entire volume and gamma index on the central 2D axial plane. All whole-brain dose distributions gave gamma passing rates higher than 95% for 2%/2 mm criteria, and pelvic sites ranged between 90% and 98% for 3%/3 mm criteria. However, thoracic spine treatments produced gamma passing rates as low as 47% for 3%/3 mm criteria. Our novel MV CBCT-based dose planning and delivery approach was feasible and time-efficient for the majority of cases. Limited MV CBCT FOV precluded workflow use for pelvic sites of larger patients and resulted in image clearance issues when tumor position was far off midline. The agreement of calculated MU on CT and MV CBCT was acceptable for all treatment sites.

Authors+Show Affiliations

University of California San Francisco. Mareike.Held@ucsf.edu.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

26699575

Citation

Held, Mareike, et al. "Feasibility of MV CBCT-based Treatment Planning for Urgent Radiation Therapy: Dosimetric Accuracy of MV CBCT-based Dose Calculations." Journal of Applied Clinical Medical Physics, vol. 16, no. 6, 2015, pp. 458-471.
Held M, Sneed PK, Fogh SE, et al. Feasibility of MV CBCT-based treatment planning for urgent radiation therapy: dosimetric accuracy of MV CBCT-based dose calculations. J Appl Clin Med Phys. 2015;16(6):458-471.
Held, M., Sneed, P. K., Fogh, S. E., Pouliot, J., & Morin, O. (2015). Feasibility of MV CBCT-based treatment planning for urgent radiation therapy: dosimetric accuracy of MV CBCT-based dose calculations. Journal of Applied Clinical Medical Physics, 16(6), 458-471. https://doi.org/10.1120/jacmp.v16i6.5625
Held M, et al. Feasibility of MV CBCT-based Treatment Planning for Urgent Radiation Therapy: Dosimetric Accuracy of MV CBCT-based Dose Calculations. J Appl Clin Med Phys. 2015 11 8;16(6):458-471. PubMed PMID: 26699575.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Feasibility of MV CBCT-based treatment planning for urgent radiation therapy: dosimetric accuracy of MV CBCT-based dose calculations. AU - Held,Mareike, AU - Sneed,Penny K, AU - Fogh,Shannon E, AU - Pouliot,Jean, AU - Morin,Olivier, Y1 - 2015/11/08/ PY - 2015/02/20/received PY - 2015/08/25/accepted PY - 2015/08/18/revised PY - 2015/12/25/entrez PY - 2015/12/25/pubmed PY - 2016/9/30/medline SP - 458 EP - 471 JF - Journal of applied clinical medical physics JO - J Appl Clin Med Phys VL - 16 IS - 6 N2 - Unlike scheduled radiotherapy treatments, treatment planning time and resources are limited for emergency treatments. Consequently, plans are often simple 2D image-based treatments that lag behind technical capabilities available for nonurgent radiotherapy. We have developed a novel integrated urgent workflow that uses onboard MV CBCT imaging for patient simulation to improve planning accuracy and reduce the total time for urgent treatments. This study evaluates both MV CBCT dose planning accuracy and novel urgent workflow feasibility for a variety of anatomic sites. We sought to limit local mean dose differences to less than 5% compared to conventional CT simulation. To improve dose calculation accuracy, we created separate Hounsfield unit-to-density calibration curves for regular and extended field-of-view (FOV) MV CBCTs. We evaluated dose calculation accuracy on phantoms and four clinical anatomical sites (brain, thorax/spine, pelvis, and extremities). Plans were created for each case and dose was calculated on both the CT and MV CBCT. All steps (simulation, planning, setup verification, QA, and dose delivery) were performed in one 30 min session using phantoms. The monitor units (MU) for each plan were compared and dose distribution agreement was evaluated using mean dose difference over the entire volume and gamma index on the central 2D axial plane. All whole-brain dose distributions gave gamma passing rates higher than 95% for 2%/2 mm criteria, and pelvic sites ranged between 90% and 98% for 3%/3 mm criteria. However, thoracic spine treatments produced gamma passing rates as low as 47% for 3%/3 mm criteria. Our novel MV CBCT-based dose planning and delivery approach was feasible and time-efficient for the majority of cases. Limited MV CBCT FOV precluded workflow use for pelvic sites of larger patients and resulted in image clearance issues when tumor position was far off midline. The agreement of calculated MU on CT and MV CBCT was acceptable for all treatment sites. SN - 1526-9914 UR - https://www.unboundmedicine.com/medline/citation/26699575/Feasibility_of_MV_CBCT_based_treatment_planning_for_urgent_radiation_therapy:_dosimetric_accuracy_of_MV_CBCT_based_dose_calculations_ L2 - https://doi.org/10.1120/jacmp.v16i6.5625 DB - PRIME DP - Unbound Medicine ER -