Evaluation of Online/Offline Image Guidance/Adaptation Approaches for Prostate Cancer Radiation Therapy

The purpose of this study is to use the same diagnostic‐quality verification and planning CTs to validate planning margin account for residual interfractional variations with image‐guided soft tissue alignment of the prostate. For nine prostate cancer patients treated with IMRT to 78 Gy in 39 fractions, daily verification CT‐on‐rails images of the first seven and last seven fractions false(n=126false) were retrospectively selected for this study. On these images, prostate, bladder, and rectum were delineated by the same attending physician. Clinical plans were created with a margin of 8 mm except for 5 mm posteriorly, referred to as 8/5 mm. Three additional plans were created for each patient with the margins of 6/4 mm, 4/2 mm, and 2 mm uniform. These plans were subsequently applied to daily images and radiation doses were recalculated. The isocenters of these plans were placed according to clinical online shifts, which were based on soft tissue alignment to the prostate. Retrospective offline shifts by aligning prostate contours were compared to online shifts. The resultant daily target dose was analyzed using D99, the percentage of the prescription dose received by 99% of CTV. The percent of bladder volume receiving 65 Gy false(normalV65Gyfalse) and rectum normalV70Gy were also analyzed. After interfractional correction, using CTV normalD99>97%% criteria, 8/5 mm, 6/4 mm, 4/2 mm, and 2 mm planning margins met the CTV dose coverage in 95%, 91%, 65%, and 53% of the 126 fractions with online shifts, and 99%, 98%, 85%, and 68% with offline shifts. The rectum normalV70Gy and bladder normalV65Gy were significantly decreased at each level of margin reduction (p<0.05). With daily diagnostic quality imaging‐guidance, the interfractional planning margin may be reduced from 8/5 mm to 6/4 mm. The residual interfractional uncertainties most likely stem from prostate rotation and deformation.PACS number(s): 87.53.‐j

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“…With 3 mm planning margin, Qin et al (27) showed that the residual margin after kV‐CBCT guidance led to insufficient CTV coverage (

EUD < 95 %

of the prescription) in 18% daily fractions. It should be noted that our proposed margin does not include intrafraction motion.…”

Section: Discussionmentioning

confidence: 99%

Using daily diagnostic quality images to validate planning margins for prostate interfractional variations

Vassil

Godley

et al. 2016

J Applied Clin Med Phys

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“…Plan adaptation has been reported for various treatment sites including lung,7 prostate,8, 9, 10 and head and neck cancers 11, 12. Across all treatment sites, adaptation is necessary due to tumor shrinkage, weight loss or other significant anatomical changes that impact the dose distribution (e.g., lung collapse or re‐inflation).…”

Section: Introductionmentioning

confidence: 99%

Online daily assessment of dose change in head and neck radiotherapy without dose‐recalculation

Vickress

Battista

Barnett

et al. 2018

J Applied Clin Med Phys

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BackgroundHead and neck cancers are commonly treated with radiation therapy, but due to possible volume changes, plan adaptation may be required during the course of treatment. Currently, plan adaptations consume significant clinical resources. Existing methods to evaluate the need for plan adaptation requires deformable image registration (DIR) to a new CT simulation or daily cone beam CT (CBCT) images and the recalculation of the dose distribution. In this study, we explore a tool to assist the decision for plan adaptation using a CBCT without re‐computation of dose, allowing for rapid online assessment.MethodsThis study involved 18 head and neck cancer patients treated with CBCT image guidance who had their treatment plan modified based on a new CT simulation (ReCT). Dose changes were estimated using different methods and compared to the current gold standard of using DIR between the planning CT scan (PCT) and ReCT with recomputed dose. The first and second methods used DIR between the PCT and daily CBCT with the planned dose or recalculated dose from the ReCT respectively, with the dose transferred to the CBCT using rigid registration. The necessity of plan adaptation was assessed by the change in dose to 95% of the planning target volume (D95) and mean dose to the parotids.ResultsThe treatment plans were adapted clinically for all 18 patients but only 7 actually needed an adaptation yielding 11 unnecessary adaptations. Applying a method using the daily CBCT with the planned dose distribution would have yielded only four unnecessary adaptations and no missed adaptations: a significant improvement from that done clinically.ConclusionUsing the DIR between the planning CT and daily CBCT can flag cases for plan adaptation before every fraction while not requiring a new re‐planning CT scan and dose recalculation.

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“…The final treatment outcomes may have been improved with a re-planning procedure during treatment. Different authors [10, 11, 31, 32] analyzed the impact of an adaptive procedure in a clinical treatment, and demonstrated the effectiveness of offline dose compensation technique in IGRT prostate cancer. A single re-planning performed when the dose accumulation process exceeds the clinician thresholds may be necessary during the course of radiotherapy to remediate timely a deviation of the delivered treatment from the planned one.…”

Section: Discussionmentioning

confidence: 99%

Dose tracking assessment for image-guided radiotherapy of the prostate bed and the impact on clinical workflow

et al. 2017

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BackgroundThe cumulative dose was compared with the planned dose among fourteen patients undergoing image-guided, intensity-modulated radiotherapy of the prostate bed. Moreover, we investigated the feasibility of adding dose tracking to the routine workflow for radiotherapy.MethodsDaily cone beam computed tomography was conducted for image-guided radiotherapy, and weekly cumulative delivered doses were calculated for dose tracking. Deformable image registration was applied to map weekly dose distributions to the original treatment plan and to create a cumulative dose distribution. The dose–volume histogram (DVH) cut-off points for the rectum and bladder and the planning target volume (PTV), were used to compare the planned and cumulative delivered doses. The additional time required by the departmental staff to complete these duties was recorded.ResultsThe PTV coverage of the delivered treatment did not satisfy the expected goal for three patients (V98% >98%). In another three patients, the DVH cut-off point for the bladder was higher than the limits, while for the rectum, treatment was as expected in all cases (two patients failed both their bladder constraints and the PTV coverage). Overall, four patients did not satisfy one or more criteria at the end of their treatment.ConclusionsA well-defined strategy for dose tracking assessment is feasible, would have minimal impact on the workload of a radiotherapy department, and may offer objective information to support radiation oncologists in making decisions about adaptive procedures.

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Evaluation of Online/Offline Image Guidance/Adaptation Approaches for Prostate Cancer Radiation Therapy

Cited by 40 publications

References 29 publications

Using daily diagnostic quality images to validate planning margins for prostate interfractional variations

Using daily diagnostic quality images to validate planning margins for prostate interfractional variations

Online daily assessment of dose change in head and neck radiotherapy without dose‐recalculation

Dose tracking assessment for image-guided radiotherapy of the prostate bed and the impact on clinical workflow

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