Advanced

Cone beam CT for QA of synthetic CT in MRI only for prostate patients

Palmér, Emilia ; Persson, Emilia LU ; Ambolt, Petra ; Gustafsson, Christian LU ; Gunnlaugsson, Adalsteinn LU and Olsson, Lars E. LU (2018) In Journal of Applied Clinical Medical Physics 19(6). p.44-52
Abstract

Purpose: Magnetic resonance imaging (MRI)-only radiotherapy is performed without computed tomography (CT). A synthetic CT (sCT) is used for treatment planning. The aim of this study was to develop a clinically feasible quality assurance (QA) procedure for sCT using the kV-cone beam CT (CBCT), in an MRI-only workflow for prostate cancer patients. Material and method: Three criteria were addressed; stability in Hounsfield Units (HUs), deviations in HUs between the CT and CBCT, and validation of the QA procedure. For the two first criteria, weekly phantom measurements were performed. For the third criteria, sCT, CT, and CBCT for ten patients were used. Treatment plans were created based on the sCT (MriPlannerTM). CT and CBCT... (More)

Purpose: Magnetic resonance imaging (MRI)-only radiotherapy is performed without computed tomography (CT). A synthetic CT (sCT) is used for treatment planning. The aim of this study was to develop a clinically feasible quality assurance (QA) procedure for sCT using the kV-cone beam CT (CBCT), in an MRI-only workflow for prostate cancer patients. Material and method: Three criteria were addressed; stability in Hounsfield Units (HUs), deviations in HUs between the CT and CBCT, and validation of the QA procedure. For the two first criteria, weekly phantom measurements were performed. For the third criteria, sCT, CT, and CBCT for ten patients were used. Treatment plans were created based on the sCT (MriPlannerTM). CT and CBCT images were registered to the sCT. The treatment plan was copied to the CT and CBCT and recalculated. Dose–volume histogram (DVH) metrics were used to evaluate dosimetric differences between the sCT plan and the recalculated CT and CBCT plans. HU distributions in sCT, CT, and CBCT were compared. Well-defined errors were introduced in the sCT for one patient to evaluate efficacy of the QA procedure. Results: The kV-CBCT system was stable in HU over time (standard deviation <40 HU). Variation in HUs between CT and CBCT was <60 HU. The differences between sCT–CT and sCT–CBCT dose distributions were below or equal to 1.0%. The highest mean dose difference for the CT and CBCT dose distribution was 0.6%. No statistically significant difference was found between total mean dose deviations from recalculated CT and CBCT plans, except for femoral head. Comparing HU distributions, the CBCT appeared to be similar to the CT. All introduced errors were identified by the proposed QA procedure, except all tissue compartments assigned as water. Conclusion: The results in this study shows that CBCT can be used as a clinically feasible QA procedure for MRI-only radiotherapy of prostate cancer patients.

(Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
cone beam CT, MRI, MRI only, prostate cancer, quality assurance, synthetic CT
in
Journal of Applied Clinical Medical Physics
volume
19
issue
6
pages
44 - 52
publisher
American College of Medical Physics
external identifiers
  • pmid:30182461
  • scopus:85053275777
ISSN
1526-9914
DOI
10.1002/acm2.12429
language
English
LU publication?
yes
id
f8719da5-5a31-43d0-83b7-28623fae5e72
date added to LUP
2018-10-22 10:38:56
date last changed
2020-02-12 09:41:37
@article{f8719da5-5a31-43d0-83b7-28623fae5e72,
  abstract     = {<p>Purpose: Magnetic resonance imaging (MRI)-only radiotherapy is performed without computed tomography (CT). A synthetic CT (sCT) is used for treatment planning. The aim of this study was to develop a clinically feasible quality assurance (QA) procedure for sCT using the kV-cone beam CT (CBCT), in an MRI-only workflow for prostate cancer patients. Material and method: Three criteria were addressed; stability in Hounsfield Units (HUs), deviations in HUs between the CT and CBCT, and validation of the QA procedure. For the two first criteria, weekly phantom measurements were performed. For the third criteria, sCT, CT, and CBCT for ten patients were used. Treatment plans were created based on the sCT (MriPlanner<sup>TM</sup>). CT and CBCT images were registered to the sCT. The treatment plan was copied to the CT and CBCT and recalculated. Dose–volume histogram (DVH) metrics were used to evaluate dosimetric differences between the sCT plan and the recalculated CT and CBCT plans. HU distributions in sCT, CT, and CBCT were compared. Well-defined errors were introduced in the sCT for one patient to evaluate efficacy of the QA procedure. Results: The kV-CBCT system was stable in HU over time (standard deviation &lt;40 HU). Variation in HUs between CT and CBCT was &lt;60 HU. The differences between sCT–CT and sCT–CBCT dose distributions were below or equal to 1.0%. The highest mean dose difference for the CT and CBCT dose distribution was 0.6%. No statistically significant difference was found between total mean dose deviations from recalculated CT and CBCT plans, except for femoral head. Comparing HU distributions, the CBCT appeared to be similar to the CT. All introduced errors were identified by the proposed QA procedure, except all tissue compartments assigned as water. Conclusion: The results in this study shows that CBCT can be used as a clinically feasible QA procedure for MRI-only radiotherapy of prostate cancer patients.</p>},
  author       = {Palmér, Emilia and Persson, Emilia and Ambolt, Petra and Gustafsson, Christian and Gunnlaugsson, Adalsteinn and Olsson, Lars E.},
  issn         = {1526-9914},
  language     = {eng},
  number       = {6},
  pages        = {44--52},
  publisher    = {American College of Medical Physics},
  series       = {Journal of Applied Clinical Medical Physics},
  title        = {Cone beam CT for QA of synthetic CT in MRI only for prostate patients},
  url          = {http://dx.doi.org/10.1002/acm2.12429},
  doi          = {10.1002/acm2.12429},
  volume       = {19},
  year         = {2018},
}