Observation of Interfractional Variations in Lung Tumor Position Using Respiratory Gated and Ungated Megavoltage Cone-Beam Computed Tomography

Chang, Jenghwa; Mageras, G.; Yorke, Ellen; Arruda, Fernando De; Sillanpaa, Jussi; Rosenzweig, Kenneth E.; Hertanto, Agung; Pham, Hai; Seppi, E.; Pevsner, Alex; Ling, C. Clifton; Amols, Howard

doi:10.1016/j.ijrobp.2006.11.055

Cited by 52 publications

(37 citation statements)

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“…Studies with deformable analytical 14 and physical 18 phantom provide a known ground truth for comparison. The second means of validation is a patient imaging study, in which patients will receive an additional CBCT gated at end expiration 6 that acts as a bronze standard for comparison to the motion-corrected CBCT. …”

Section: Discussionmentioning

confidence: 99%

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Correction of motion artifacts in cone‐beam CT using a patient‐specific respiratory motion model

et al. 2010

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Purpose: Respiratory motion adversely affects CBCT image quality and limits its localization accuracy for image-guided radiation treatment. Motion correction methods in CBCT have focused on the thorax because of its higher soft tissue contrast, whereas low-contrast tissue in abdomen remains a challenge. The authors report on a method to correct respiration-induced motion artifacts in 1 min CBCT scans that is applicable in both thorax and abdomen, using a motion model adapted to the patient from a respiration-correlated image set. Methods: Model adaptation consists of nonrigid image registration that maps each image to a reference image in the respiration-correlated set, followed by a principal component analysis to reduce errors in the nonrigid registration. The model parametrizes the deformation field in terms of observed surrogate ͑diaphragm or implanted marker͒ position and motion ͑inhalation or exhalation͒ between the images. In the thorax, the model is obtained from the same CBCT images that are to be motion-corrected, whereas in the abdomen, the model uses respiration-correlated CT ͑RCCT͒ images acquired prior to the treatment session. The CBCT acquisition is a single 360°rotation lasting 1 min, while simultaneously recording patient breathing. The approximately 600 projection images are sorted into six ͑in thorax͒ or ten ͑in abdomen͒ subsets and reconstructed to obtain a set of low-quality respiration-correlated RC-CBCT images. Application of the motion model deforms each of the RC-CBCT images to a chosen reference image in the set; combining all images yields a single high-quality CBCT image with reduced blurring and motion artifacts. Repeated application of the model with different reference images produces a series of motion-corrected CBCT images over the respiration cycle, for determining the motion extent of the tumor and nearby organs at risk. The authors also investigate a simpler correction method, which does not use PCA and correlates motion state with respiration phase, thus assuming repeatable breathing patterns. Comparison of contrast-to-noise ratios of pixel intensities within anatomical structures relative to surrounding background tissue provides a quantitative assessment of relative organ visibility. Results: Evaluation in lung phantom, two patient cases in thorax and two in upper abdomen, shows that blurring and streaking artifacts are visibly reduced with motion correction. The boundaries of tumors in the thorax, liver, and kidneys are sharper and more discernible. Repeat application of the method in one thorax case, with reference images chosen at end expiration and end inspiration, indicates its feasibility for observing tumor motion extent. Phase-based motion correction without PCA reduces blurring less effectively; in addition, implanted markers appear broken up, indicating inconsistencies in the phase-based correction. In structures showing 1 cm or more motion excursion, PCA-based motion correction shows the highest contrast-to-noise ratios in the cases examined. Conclusions: Motion...

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Section: Discussionmentioning

confidence: 99%

“…We have investigated gated CBCT to reduce motion artifacts. 6 A limitation is the low duty cycle for imaging ͑20%-30%͒, resulting in correspondingly longer ͑4-5 min͒ acquisition times.…”

Section: Introductionmentioning

confidence: 99%

Correction of motion artifacts in cone‐beam CT using a patient‐specific respiratory motion model

et al. 2010

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“…Our earlier study has shown that interfractional variations in lung tumor position relative to the skeletal anatomy do occur in this patient group, and that correction of systematic error in tumor position may improve treatment accuracy. 13 A second study goal is to examine whether explicit measurement of tumor respiratory motion trajectories is important to tumor localization, by comparing registration of respiration-correlated image sets to that of respiration-averaged images. Tools for acquiring respirationaveraged images are more widely available and rigid registration of respiration-averaged CT and CBCT images is a wellestablished and time-efficient procedure.…”

Section: Discussionmentioning

confidence: 99%

“…In a study of interfractional variations in lung tumor position using megavoltage CBCT, systematic deviations were comparable or larger than random ones, suggesting that using volumetric imaging for correction of systematic error could be an efficient and effective means of improving treatment accuracy. 13 A particular challenge in thoracic disease sites is that respiratory motion can introduce artifacts in a planning CT scan and blur in a CBCT, thus reducing localization accuracy. Respiration-correlated CT (RCCT), where images are retrospectively binned according to the respiratory phase, has been shown to reduce respiratory motion artifacts and yield 3D images at different points in the respiratory cycle.…”

Section: Introductionmentioning

confidence: 99%

A study of respiration‐correlated cone‐beam CT scans to correct target positioning errors in radiotherapy of thoracic cancer

et al. 2012

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Purpose: There is increasingly widespread usage of cone-beam CT (CBCT) for guiding radiation treatment in advanced-stage lung tumors, but difficulties associated with daily CBCT in conventionally fractionated treatments include imaging dose to the patient, increased workload and longer treatment times. Respiration-correlated cone-beam CT (RC-CBCT) can improve localization accuracy in mobile lung tumors, but further increases the time and workload for conventionally fractionated treatments. This study investigates whether RC-CBCT-guided correction of systematic tumor deviations in standard fractionated lung tumor radiation treatments is more effective than 2D imagebased correction of skeletal deviations alone. A second study goal compares respiration-correlated vs respiration-averaged images for determining tumor deviations. Methods: Eleven stage II-IV nonsmall cell lung cancer patients are enrolled in an IRB-approved prospective off-line protocol using RC-CBCT guidance to correct for systematic errors in GTV position. Patients receive a respiration-correlated planning CT (RCCT) at simulation, daily kilovoltage RC-CBCT scans during the first week of treatment and weekly scans thereafter. Four types of correction methods are compared: (1) systematic error in gross tumor volume (GTV) position, (2) systematic error in skeletal anatomy, (3) daily skeletal corrections, and (4) weekly skeletal corrections. The comparison is in terms of weighted average of the residual GTV deviations measured from the RC-CBCT scans and representing the estimated residual deviation over the treatment course. In the second study goal, GTV deviations computed from matching RCCT and RC-CBCT are compared to deviations computed from matching respiration-averaged images consisting of a CBCT reconstructed using all projections and an average-intensity-projection CT computed from the RCCT. Results: Of the eleven patients in the GTV-based systematic correction protocol, two required no correction, seven required a single correction, one required two corrections, and one required three corrections. Mean residual GTV deviation (3D distance) following GTV-based systematic correction (mean ± 1 standard deviation 4.8 ± 1.5 mm) is significantly lower than for systematic skeletal-based (6.5 ± 2.9 mm, p = 0.015), and weekly skeletal-based correction (7.2 ± 3.0 mm, p = 0.001), but is not significantly lower than daily skeletal-based correction (5.4 ± 2.6 mm, p = 0.34). In two cases, first-day CBCT images reveal tumor changes-one showing tumor growth, the other showing large tumor displacement-that are not readily observed in radiographs. Differences in computed GTV deviations between respiration-correlated and respiration-averaged images are 0.2 ± 1.8 mm in the superior-inferior direction and are of similar magnitude in the other directions. Conclusions: An off-line protocol to correct GTV-based systematic error in locally advanced lung tumor cases can be effective at reducing tumor deviations, although the findings need confirmation with larger patient s...

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“…Then, a margin around the target would be unnecessary, except in disease site with intra-fraction uncertainties. The complexity of IGRT-D is compounded at sites that experience motion*most commonly due to respiration [79]. Yet, respiratory control and IGRT-D are distinct processes and one does not imply the other.…”

Section: Dose Delivery Assurancementioning

confidence: 99%

Broadening the scope of Image-Guided Radiotherapy (IGRT)

Greco

Ling

2008

Acta Oncologica

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Observation of Interfractional Variations in Lung Tumor Position Using Respiratory Gated and Ungated Megavoltage Cone-Beam Computed Tomography

Cited by 52 publications

References 45 publications

Correction of motion artifacts in cone‐beam CT using a patient‐specific respiratory motion model

Correction of motion artifacts in cone‐beam CT using a patient‐specific respiratory motion model

A study of respiration‐correlated cone‐beam CT scans to correct target positioning errors in radiotherapy of thoracic cancer

Broadening the scope of Image-Guided Radiotherapy (IGRT)

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