A novel concept to include uncertainties in the evaluation of stereotactic body radiation therapy after 4D dose accumulation using deformable image registration

In the context of head and neck cancer (HNC) adaptive radiation therapy (ART), the two purposes of the study were to compare the performance of multiple deformable image registration (DIR) methods and to quantify their impact for dose accumulation, in healthy structures. Fifteen HNC patients had a planning computed tomography (CT0) and weekly CTs during the 7 weeks of intensity-modulated radiation therapy (IMRT). Ten DIR approaches using different registration methods (demons or B-spline free form deformation (FFD)), preprocessing, and similarity metrics were tested. Two observers identified 14 landmarks (LM) on each CT-scan to compute LM registration error. The cumulated doses estimated by each method were compared. The two most effective DIR methods were the demons and the FFD, with both the mutual information (MI) metric and the filtered CTs. The corresponding LM registration accuracy (precision) was 2.44 mm (1.30 mm) and 2.54 mm (1.33 mm), respectively. The corresponding LM estimated cumulated dose accuracy (dose precision) was 0.85 Gy (0.93 Gy) and 0.88 Gy (0.95 Gy), respectively. The mean uncertainty (difference between maximal and minimal dose considering all the 10 methods) to estimate the cumulated mean dose to the parotid gland (PG) was 4.03 Gy (SD = 2.27 Gy, range: 1.06–8.91 Gy).

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Cone beam computed tomography and image registration based on target area for stereotactic body radiation therapy of lung cancer

Journal of Radiation Research and Applied Sciences ◽

10.1080/16878507.2021.1981754 ◽

2021 ◽

Vol 14 (1) ◽

pp. 404-411

Author(s):

Long-Gang Gui ◽

Miao Shi ◽

Jun Li

Keyword(s):

Computed Tomography ◽

Lung Cancer ◽

Radiation Therapy ◽

Image Registration ◽

Cone Beam Computed Tomography ◽

Stereotactic Body Radiation Therapy ◽

Cone Beam ◽

Target Area ◽

Stereotactic Body Radiation

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Imaging as Part of a Quality Assurance Program: Predictors of Interobserver Variability for Pretreatment Image Registration for Lung SBRT

Technology in Cancer Research & Treatment ◽

10.1177/1533033819870795 ◽

2019 ◽

Vol 18 ◽

pp. 153303381987079

Author(s):

Geoff Baran ◽

Jay Burmeister ◽

Peter Paximadis ◽

Todd Bossenberg ◽

Robert Halford ◽

...

Keyword(s):

Radiation Therapy ◽

Image Registration ◽

Stereotactic Body Radiation Therapy ◽

Interobserver Variability ◽

Quality Assurance Program ◽

P Value ◽

3 Dimensional ◽

Stereotactic Body Radiation ◽

Significant Difference ◽

Interobserver Variations

Purpose: To evaluate the magnitude of interobserver variability in pretreatment image registration for lung stereotactic body radiation therapy patients in aggregate and within 3 clinical subgroups and to determine methods to identify patients expected to demonstrate larger variability. Methods and Materials: Retrospective image registration was performed for the first and last treatment fraction for 10 lung stereotactic body radiation therapy patients by 16 individual observers (5 physicians, 6 physicists, and 5 therapists). Registration translation values were compared within and between subgroups overall and between the first and the last fractions. Four metrics were evaluated as possible predictors for large interobserver variability. Results: The mean 3-dimensional displacement vector for all patients over all comparisons was 2.4 ± 1.8 mm. Three patients had mean 3-dimensional vector differences >3 mm. This cohort of patients showed a significant interfraction difference in variance ( P value = .01), increasing from first fraction to last. A significant difference in interobserver variability was observed between physicians and physicists ( P value < .01) and therapists and physicists ( P value < .01) but not between physicians and therapists ( P value = .07). Three of the 4 quantities evaluated as potential predictive metrics showed statistical correlation with increased interobserver variation, including target excursion and local target/lung contrast. Conclusion: Variability in pretreatment image guidance represents an important treatment consideration, particularly for stereotactic body radiation therapy, which employs small margins and a small number of treatment fractions. As a result of the data presented here, we have initiated weekly “registration rounds” to familiarize all staff physicians with the target and normal anatomy for each stereotactic body radiation therapy patient and minimize interobserver variations in image registration prior to treatment. The metrics shown here are capable of identifying patients for which large interobserver variations would be anticipated. These metrics may be used in the future to develop thresholds for additional interventions to mitigate registration variations.

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