Evaluation of On-Board kV Cone Beam Computed Tomography–Based Dose Calculation With Deformable Image Registration Using Hounsfield Unit Modifications

Onozato, Yusuke; Kadoya, Noriyuki; Fujita, Yukio; Arai, Kazuhiro; Dobashi, Suguru; Takeda, Ken; Kishi, Kazuma; Umezawa, Rei; Matsushita, Haruo; Jingu, Keiichi

doi:10.1016/j.ijrobp.2014.02.007

Cited by 63 publications

(81 citation statements)

References 34 publications

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“…Thirdly, daily dose distributions were calculated based on deformed CTs after CT-to-CBCT DIR for HU modification using the implemented algorithm in VelocityAI [18]. The algorithm performance for CT-to-CBCT registration in the pelvic area was previously evaluated in terms of registration errors and small errors across the whole pelvic area (mean: 1.9 mm) were reported [19,20]. However, only the reported registration error for bladder was relatively large (mean: 4.6 mm) due to the initial large bladder volume differences in their study [19].…”

Section: Discussionmentioning

confidence: 99%

“…Next to the reported DIR accuracy and the high initial similarity between CBCTs and selected CTs, deformed CTs were visually inspected by an experienced observer to ensure correct HU modification for reliable dose calculation. Moreover, Onozato et al [20] evaluated the accuracy of dose calculation for pelvic anatomy after CT-to-CBCT DIR and reported average dose uncertainties of 1.2%. Furthermore, deformed CTs including possible deformation inaccuracies are used in both strategies and will not affect the outcome when comparing both strategies.…”

Section: Discussionmentioning

confidence: 99%

“…Consequently, possible small deviations are included in an identical way in both strategies and will not affect our outcome when comparing both strategies. Given the previously evaluated DIR accuracy [19], the reported negligible dose uncertainties induced by HU modification [20], the high initial similarity between pre-fraction CBCTs and selected CTs, delineation deformation validation by an experienced observer and the use of identical deformed delineations for both strategies, we consider our presented dose differences realistic and definitely representative for advantages of cervical cancer ART.…”

Section: Discussionmentioning

confidence: 99%

“…After rigid alignment based on bony anatomy, selected CTs with accurate HU were deformed to represent CBCT images. The performances of CT-to-CBCT deformable registration in the pelvic area using the VelocityAI software were validated previously and accurate DIR results were reported [19,20]. Additionally, an experienced observer visually assessed the DIR results to verify plausible HU modification for CBCT-based dose calculation.…”

Section: Daily Dose Calculationmentioning

confidence: 91%

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Dosimetric advantages of a clinical daily adaptive plan selection strategy compared with a non-adaptive strategy in cervical cancer radiation therapy

et al. 2017

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Background: Radiation therapy (RT) using a daily plan selection adaptive strategy can be applied to account for interfraction organ motion while limiting organ at risk dose. The aim of this study was to quantify the dosimetric consequences of daily plan selection compared with non-adaptive RT in cervical cancer. Material and methods: Ten consecutive patients who received pelvic irradiation, planning CTs (full and empty bladder), weekly post-fraction CTs and pre-fraction CBCTs were included. Non-adaptive plans were generated based on the PTV defined using the full bladder planning CT. For the adaptive strategy, multiple PTVs were created based on both planning CTs by ITVs of the primary CTVs (i.e., GTV, cervix, corpus-uterus and upper part of the vagina) and corresponding library plans were generated. Daily CBCTs were rigidly aligned to the full bladder planning CT for plan selection. For daily plan recalculation, selected CTs based on initial similarity were deformably registered to CBCTs. Differences in daily target coverage (D 98% > 95%) and in V 0.5Gy , V 1.5Gy , V 2Gy , D 50% and D 2% for rectum, bladder and bowel were assessed. Results: Non-adaptive RT showed inadequate primary CTV coverage in 17% of the daily fractions. Plan selection compensated for anatomical changes and improved primary CTV coverage significantly (p < 0.01) to 98%. Compared with non-adaptive RT, plan selection decreased the fraction dose to rectum and bowel indicated by significant (p < 0.01) improvements for daily V 0.5Gy , V 1.5Gy , V 2Gy , D 50% and D 2% . However, daily plan selection significantly increased the bladder V 1.5Gy , V 2Gy , D 50% and D 2% . Conclusions: In cervical cancer RT, a non-adaptive strategy led to inadequate target coverage for individual patients. Daily plan selection corrected for day-to-day anatomical variations and resulted in adequate target coverage in all fractions. The dose to bowel and rectum was decreased significantly when applying adaptive RT.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Daily Dose Calculationmentioning

confidence: 91%

See 2 more Smart Citations

Dosimetric advantages of a clinical daily adaptive plan selection strategy compared with a non-adaptive strategy in cervical cancer radiation therapy

et al. 2017

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“…In previous studies, degradation of accuracy in calculated dose distribution has been shown when original CBCT numbers were used for dose calculations; therefore, replacement of CBCT numbers with conventional CT numbers has been suggested [4] [5] [6] [7] [8]. Richter et al studied several conversion methods of CBCT numbers measured under different conditions by using two phantoms and 33 patients [4], and Hu et al used an approach to make a conversion curve for each patient by using CBCT images acquired on the day of the planning CT [5].…”

Section: Introductionmentioning

confidence: 99%

Analysis of Dose Calculation Accuracy in Cone Beam Computed Tomography with Various Amount of Scattered Photon Contamination

Usui¹,

Ogawa²,

Sasai³

2017

IJMPCERO

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Cone-beam computed tomography (CBCT) images have inaccurate CT numbers because of scattered photons. Thus, quantitative analysis of scattered photons that affect an electron density (ED) curve and calculated doses may be effective information to achieve CBCT-based radiation treatment planning. We quantitatively evaluated the effect of scattered photons on the accuracy of dose calculations from a lung image. The Monte Carlo method was used to calculate CBCT projection data, and we made two calibration curves for conditions with or without scattered photons. Moreover, we applied cupping artifact correction and evaluated the effects on image uniformity and dose calculation accuracy. Dose deviations were compared with those of conventional CT in conventional and volumetric intensity modulated arc therapy (VMAT) planning by using γ analysis and dose volume histogram (DVH) analysis. We found that cupping artifacts contaminated the scattered photons, and the γ analysis showed that the dose distribution was most decreased for a scattered photon ratio of 40%. Cupping artifact correction significantly improved image uniformity; therefore, ED curves were near ideal, and the pass rate results were significantly higher than those associated with the scattered photon effect in 65.1% and 78.4% without correction, 99.5% and 97.7% with correction, in conventional and VMAT planning, respectively. In the DVH analysis, all organ dose indexes were reduced in the scattered photon images, but dose index error rates with cupping artifact correction were improved within approximately 10%. CBCT image quality was strongly affected by scattered photons, and the dose calculation accuracy based on the CBCT image was improved by removing cupping artifacts caused by the scattered photons.

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Patient‐specific calibration of cone‐beam computed tomography data sets for radiotherapy dose calculations and treatment plan assessment

MacFarlane

Wong

Hoover

et al. 2018

J Applied Clin Med Phys

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PurposeIn this work, we propose a new method of calibrating cone beam computed tomography (CBCT) data sets for radiotherapy dose calculation and plan assessment. The motivation for this patient‐specific calibration (PSC) method is to develop an efficient, robust, and accurate CBCT calibration process that is less susceptible to deformable image registration (DIR) errors.MethodsInstead of mapping the CT numbers voxel‐by‐voxel with traditional DIR calibration methods, the PSC methods generates correlation plots between deformably registered planning CT and CBCT voxel values, for each image slice. A linear calibration curve specific to each slice is then obtained by least‐squares fitting, and applied to the CBCT slice's voxel values. This allows each CBCT slice to be corrected using DIR without altering the patient geometry through regional DIR errors.A retrospective study was performed on 15 head‐and‐neck cancer patients, each having routine CBCTs and a middle‐of‐treatment re‐planning CT (reCT). The original treatment plan was re‐calculated on the patient's reCT image set (serving as the gold standard) as well as the image sets produced by voxel‐to‐voxel DIR, density‐overriding, and the new PSC calibration methods. Dose accuracy of each calibration method was compared to the reference reCT data set using common dose‐volume metrics and 3D gamma analysis. A phantom study was also performed to assess the accuracy of the DIR and PSC CBCT calibration methods compared with planning CT.ResultsCompared with the gold standard using reCT, the average dose metric differences were ≤ 1.1% for all three methods (PSC: −0.3%; DIR: −0.7%; density‐override: −1.1%). The average gamma pass rates with thresholds 3%, 3 mm were also similar among the three techniques (PSC: 95.0%; DIR: 96.1%; density‐override: 94.4%).ConclusionsAn automated patient‐specific calibration method was developed which yielded strong dosimetric agreement with the results obtained using a re‐planning CT for head‐and‐neck patients.

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Evaluation of On-Board kV Cone Beam Computed Tomography–Based Dose Calculation With Deformable Image Registration Using Hounsfield Unit Modifications

Cited by 63 publications

References 34 publications

Dosimetric advantages of a clinical daily adaptive plan selection strategy compared with a non-adaptive strategy in cervical cancer radiation therapy

Dosimetric advantages of a clinical daily adaptive plan selection strategy compared with a non-adaptive strategy in cervical cancer radiation therapy

Analysis of Dose Calculation Accuracy in Cone Beam Computed Tomography with Various Amount of Scattered Photon Contamination

Patient‐specific calibration of cone‐beam computed tomography data sets for radiotherapy dose calculations and treatment plan assessment

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