On the dosimetric effect and reduction of inverse consistency and transitivity errors in deformable image registration for dose accumulation

Bender, Edward T.; Hardcastle, Nicholas

doi:10.1118/1.3666948

Cited by 50 publications

(58 citation statements)

References 12 publications

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“…10 However, through the use of inverse consistency (IC), intensity-based DIRs can improve dose accumulation results. 11,12 These studies highlight the need to relate clinical decision parameters (e.g., minimum dose to the target and maximum dose to the normal tissue) to the uncertainty in DIR algorithms on dose accumulation results.…”

Section: Introductionmentioning

confidence: 99%

Effect of deformable registration uncertainty on lung SBRT dose accumulation

2015

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Purpose: Deformable image registration (DIR) plays an important role in dose accumulation, such as incorporating breathing motion into the accumulation of the delivered dose based on daily 4DCBCT images. However, it is not yet well understood how the uncertainties associated with DIR methods affect the dose calculations and resulting clinical metrics. The purpose of this study is to evaluate the impact of DIR uncertainty on the clinical metrics derived from its use in dose accumulation. Methods: A biomechanical model based DIR method and a biomechanical-intensity-based hybrid method, which reduced the average registration error by 1.6 mm, were applied to ten lung cancer patients. A clinically relevant dose parameter [minimum dose to 0.5 cm 3 (Dmin)] was calculated for three dose scenarios using both algorithms. Dose scenarios included static (no breathing motion), predicted (breathing motion at the time of planning), and total accumulated (interfraction breathing motion). The relationship between the dose parameter and a combination of DIR uncertainty metrics, tumor volume, and dose heterogeneity of the plan was investigated. Results: Depending on the dose heterogeneity, tumor volume, and DIR uncertainty, in over 50% of the patients, differences greater than 1.0 Gy were observed in the Dmin of the tumor in the static dose calculation on exhale phase of the 4DCT. Such differences were due to the errors in propagating the tumor contours from the reference planning 4DCT phase onto a subsequent 4DCT phase using each DIR algorithm and calculating the dose on that phase. The differences in predicted dose were more subtle when breathing motion was modeled explicitly at the time of planning with only one patient exhibiting a greater than 1.0 Gy difference in Dmin. Dmin differences of up to 2.5 Gy were found in the total accumulated delivered dose due to difference in quantifying the interfraction variations. Such dose uncertainties could potentially be clinically significant. Conclusions: Reductions in average uncertainty in DIR algorithms by 1.6 mm may have a clinically significant impact on the decision-making metrics used in dose planning and dose accumulation assessment. C

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Section: Introductionmentioning

confidence: 99%

Effect of deformable registration uncertainty on lung SBRT dose accumulation

2015

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“…First, the current study only considers contour propagation. Surface analyses (20) or overlap metrics (40) provide limited information about deformation accuracy within a structure, so results of this study should not be generalized to other DIR applications, such as dose summation (41) . Second, the study was limited to a single commercially available DIR algorithm, though the methodology employed should be transferrable to other DIR algorithms.…”

Section: Discussionmentioning

confidence: 99%

Deformable image registration and interobserver variation in contour propagation for radiation therapy planning

Riegel

Antone

Zhang

et al. 2016

J Applied Clin Med Phys

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Deformable image registration (DIR) and interobserver variation inevitably introduce uncertainty into the treatment planning process. The purpose of the current work was to measure deformable image registration (DIR) errors and interobserver variability for regions of interest (ROIs) in the head and neck and pelvic regions. Measured uncertainties were combined to examine planning margin adequacy for contours propagated for adaptive therapy and to assess the trade‐off of DIR and interobserver uncertainty in atlas‐based automatic segmentation. Two experienced dosimetrists retrospectively contoured brainstem, spinal cord, anterior oral cavity, larynx, right and left parotids, optic nerves, and eyes on the planning CT (CT1) and attenuation‐correction CT of diagnostic PET/CT (CT2) for 30 patients who received radiation therapy for head and neck cancer. Two senior radiation oncology residents retrospectively contoured prostate, bladder, and rectum on the postseed‐implant CT (CT1) and planning CT (CT2) for 20 patients who received radiation therapy for prostate cancer. Interobserver variation was measured by calculating mean Hausdorff distances between the two observers' contours. CT2 was deformably registered to CT1 via commercially available multipass B‐spline DIR. CT2 contours were propagated and compared with CT1 contours via mean Hausdorff distances. These values were summed in quadrature with interobserver variation for margin analysis and compared with interobserver variation for statistical significance using two‐tailed t‐tests for independent samples (α=0.05). Combined uncertainty ranged from 1.5‐5.8 mm for head and neck structures and 3.1‐3.7 mm for pelvic structures. Conventional 5 mm margins may not be adequate to cover this additional uncertainty. DIR uncertainty was significantly less than interobserver variation for four head and neck and one pelvic ROI. DIR uncertainty was not significantly different than interobserver variation for four head and neck and one pelvic ROI. DIR uncertainty was significantly greater than interobserver variation for two head and neck and one pelvic ROI. The introduction of DIR errors may offset any reduction in interobserver variation by using atlas‐based automatic segmentation.PACS number(s): 87.57.nj, 87.55.D‐

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“…The 95% confidence interval of the total delivered dose NTCP is relatively small compared with the difference between total delivered dose and planned dose NTCPs. When DIR algorithms with small inverse consistency and transitivity errors are implemented in dose accumulation, the total delivered dose should vary little by the image pathway taken(18). …”

Section: Discussionmentioning

confidence: 99%

“…(18,26-28). As pointed out in reference 18 even though DIR and DDA are not perfect and suffer from residual errors, estimates of toxicity or tumor control based on these methods are likely to be more representative of clinical reality, than estimates based on methods that ignore anatomical change and structure distortion through out treatment, and simply use the total planned dose to estimate expected normal tissue complications and local tumor control. The current study focuses on exploring the benefit of using the total delivered dose calculated employing the DDA workflow shown in Figure 2 to arrive at an estimate of total delivered dose to the patient.…”

Section: Methodsmentioning

confidence: 99%

On Voxel-by-voxel Accumulated Dose for Prostate Radiation Therapy using Deformable Image Registration

Hardcastle

Jeong

et al. 2015

Technol Cancer Res Treat

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Since delivered dose is rarely the same with planned, we calculated the delivered total dose to ten prostate radiotherapy patients treated with rectal balloons using deformable dose accumulation (DDA) and compared it with the planned dose. The patients were treated with TomoTherapy using two rectal balloon designs: five patients had the Radiadyne balloon (balloon A), and five patients had the EZ-EM balloon (balloon B). Prostate and rectal wall contours were outlined on each pre-treatment MVCT for all patients. Delivered fractional doses were calculated using the MVCT taken immediately prior to delivery. Dose grids were accumulated to the last MVCT using DDA tools in Pinnacle3 ™ (v9.100, Philips Radiation Oncology Systems, Fitchburg, USA). Delivered total doses were compared with planned doses using prostate and rectal wall DVHs. The rectal NTCP was calculated based on total delivered and planned doses for all patients using the Lyman model. For 8/10 patients, the rectal wall NTCP calculated using the delivered total dose was less than planned, with seven patients showing a decrease of more than 5% in NTCP. For 2/10 patients studied, the rectal wall NTCP calculated using total delivered dose was 2% higher than planned. This study indicates that for patients receiving hypofractionated radiotherapy for prostate cancer with a rectal balloon, total delivered doses to prostate is similar with planned while delivered dose to rectal walls may be significantly different from planned doses. 8/10 patients show significant correlation between rectal balloon anterior-posterior positions and some VD values.

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On the dosimetric effect and reduction of inverse consistency and transitivity errors in deformable image registration for dose accumulation

Cited by 50 publications

References 12 publications

Effect of deformable registration uncertainty on lung SBRT dose accumulation

Effect of deformable registration uncertainty on lung SBRT dose accumulation

Deformable image registration and interobserver variation in contour propagation for radiation therapy planning

On Voxel-by-voxel Accumulated Dose for Prostate Radiation Therapy using Deformable Image Registration

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