Impact of motion induced artifacts on automatic registration of lung tumors in Tomotherapy

Goossens, Samuel; Descampe, Antonin; Xivry, Jonathan Orban de; Lee, John A.; Delor, Antoine; Janssens, Guillaume; Geets, Xavier

doi:10.1016/j.ejmp.2015.07.140

Cited by 3 publications

(7 citation statements)

References 32 publications

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“…Consistent with the literature, MVCT images of targets subject to respiratory motion with breathing periods approaching or equal to 5.0 s suffer from aliasing artifacts but as the breathing period decreases, these artifacts are reduced 21 . This is clearly displayed in Figure 6, where the 5.0 s MVCT image has an excess volume of more than 50% but for 2.0 s is reduced to approximately 5%.…”

Section: Discussionsupporting

confidence: 84%

“…If patient breathing characteristics at the time of treatment are assumed to be the same as during 4DCT acquisition, one might expect the planned internal target volume (ITV) to match the pre‐treatment target volume as measured with OBI. However, underrepresentation of this target excursion, due to the poor selection of window and level or respiratory trace characteristics (e.g., long‐exhale (LE)), combined with differences in image acquisition speeds, has the potential to lead to incorrect positioning for treatment 15–21 …”

Section: Introductionmentioning

confidence: 99%

“…For a clinically unrealistic breathing period of 1.0 s to simulate the benefit of an ultra‐slow scan, motion artifacts were reduced and the image better represented the ITV known a priori in both volume and shape 18 . Goosens et al studied the use of tumor‐based registration between average planning kVCT and MVCT under clinically relevant respiration conditions in all three anatomical directions and found a high degree of registration accuracy except when the tumor motion period was equal to half of the gantry period during MVCT acquisition due to aliasing artifacts 21 . These studies made use of simple sinusoidal motion, as opposed to the LE motion generally observed clinically.…”

Section: Introductionmentioning

confidence: 99%

“…However, underrepresentation of this target excursion, due to the poor selection of window and level or respiratory trace characteristics (e.g., long‐exhale (LE)), combined with differences in image acquisition speeds, has the potential to lead to incorrect positioning for treatment. 15 , 16 , 17 , 18 , 19 , 20 , 21 …”

Section: Introductionmentioning

confidence: 99%

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MVCT versus kV‐CBCT for targets subject to respiratory motion: A phantom study

Baran

Dominello

Bossenberger

et al. 2021

J Applied Clin Med Phys

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The use of kilovoltage cone‐beam computed tomography (kV‐CBCT) or megavoltage computed tomography (MVCT) for image guidance prior to lung stereotactic body radiation therapy (SBRT) is common clinical practice. We demonstrate that under equivalent respiratory conditions, image guidance using both kV‐CBCT and MVCT may result in the inadequate estimation of the range of target motion under free‐breathing (FB) conditions when standard low‐density window and levels are used. Two spherical targets within a respiratory motion phantom were imaged using both long‐exhale (LE) and sinusoidal respiratory traces. MVCT and kV‐CBCT images were acquired and evaluated for peak‐to‐peak amplitudes of 10 or 20 mm in the cranial‐caudal direction, and with 2, 4 or 5 s periods. All images were visually inspected for artifacts and conformity to the ITV for each amplitude, period, trace‐type, and target size. All LE respiratory traces required a lower threshold HU window for MVCT and kV‐CBCT compared to sinusoidal traces to obtain 100% volume conformity compared with the theoretical ITV (ITVT). Excess volume was less than 2% for all kV‐CBCT contours regardless of trace‐type, breathing period, or amplitude, while the maximum excess volume for MVCT was 48%. Adjusting window and level to maximize conformity with the ITVT is necessary to reduce registration uncertainty to less than 5 mm. To fully capture target motion with either MVCT or kV‐CBCT, substantial changes in HU levels up to −600 HU are required which may not be feasible clinically depending on the target's location and surrounding tissue contrast. This registration method, utilizing a substantially decreased window and level compared to standard low‐density settings, was retrospectively compared to the automated registration algorithm for five lung SBRT patients exposed to pre‐treatment kV‐CBCT image guidance. Differences in registrations in the super‐inferior (SI) direction greater than the commonly used ITV to PTV margin of 5 mm were encountered for several cases. In conclusion, pre‐treatment image guidance for lung SBRT targets using MVCT or kV‐CBCT is unlikely to capture the full extent of target motion as defined by the ITVT and additional caution is warranted to avoid registration errors for small targets and patients with LE respiratory traces.

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Section: Discussionsupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

MVCT versus kV‐CBCT for targets subject to respiratory motion: A phantom study

Baran

Dominello

Bossenberger

et al. 2021

J Applied Clin Med Phys

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“…Specifically, motion-induced artifacts, especially if the target is moving in the lateral direction or at a breathing period of 5.0 seconds, may degrade the ability to perform automatic registration and in addition potentially increase interobserver variability. [11][12][13] Consequently, not only does the magnitude of the tumor motion influence registration but so does the direction and period of such motion.…”

Section: Discussionmentioning

confidence: 99%

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

Baran

Burmeister

Paximadis

et al. 2019

Technol Cancer Res Treat

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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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