The impact of temporal inaccuracies on 4DCT image quality

Mutaf, Y. D.; Antolak, John A.; Brinkmann, Debra H.

doi:10.1118/1.2717404

Cited by 82 publications

(74 citation statements)

References 29 publications

(23 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Algorithms for IMRT leaf sequencing have been developed and improved to reduce total segment numbers in order to shorten treatment delivery time 1 , 2 , 3 , 4 . Recent studies indicate that shortening treatment time could reduce dose delivery uncertainty due to organ motion and patient setup for image‐guided radiotherapy, adaptive radiotherapy, and radiotherapy quality assurance 5 , 6 , 7 , 8 . In addition to dosimetric quality, the workflow efficiency of the cancer clinic is also affected by long treatment time.…”

Section: Introductionmentioning

confidence: 99%

Direct aperture optimization using an inverse form of back‐projection

Zhu

Cullip

Tracton

et al. 2014

J Applied Clin Med Phys

View full text Add to dashboard Cite

Direct aperture optimization (DAO) has been used to produce high dosimetric quality intensity‐modulated radiotherapy (IMRT) treatment plans with fast treatment delivery by directly modeling the multileaf collimator segment shapes and weights. To improve plan quality and reduce treatment time for our in‐house treatment planning system, we implemented a new DAO approach without using a global objective function (GFO). An index concept is introduced as an inverse form of back‐projection used in the CT multiplicative algebraic reconstruction technique (MART). The index, introduced for IMRT optimization in this work, is analogous to the multiplicand in MART. The index is defined as the ratio of the optima over the current. It is assigned to each voxel and beamlet to optimize the fluence map. The indices for beamlets and segments are used to optimize multileaf collimator (MLC) segment shapes and segment weights, respectively. Preliminary data show that without sacrificing dosimetric quality, the implementation of the DAO reduced average IMRT treatment time from 13 min to 8 min for the prostate, and from 15 min to 9 min for the head and neck using our in‐house treatment planning system PlanUNC. The DAO approach has also shown promise in optimizing rotational IMRT with burst mode in a head and neck test case.PACS number: 87.55.D‐

show abstract

Section: Introductionmentioning

confidence: 99%

Direct aperture optimization using an inverse form of back‐projection

Zhu

Cullip

Tracton

et al. 2014

J Applied Clin Med Phys

View full text Add to dashboard Cite

show abstract

“…This is also evident from the inability of retrospective phase sorting methods to produce artifact-free 4D CT images. 1,3,5,7 However, it is assumed here that if the displacement and velocity of the respiratory trace match for two different cycles, it can also be assumed that the acceleration, and therefore the instantaneous force on the tumor, is equal or nearly equal, resulting in the same deformation and trajectory. It is therefore hypothesized that this method can produce accurate reconstructed 4D CT images in five dimensional parameter space, by sorting 2D CT images not only by using a temporal parameter, but also an "anatomical state" parameter.…”

Section: Introductionmentioning

confidence: 99%

“…Various studies have shown that the magnitude of artifacts resulting from retrospective displacement sorting is less severe than those resulting from retrospective phase sorting. 1,3,5,7 Recently it was found that at least one artifact appeared in retrospectively phase sorted 4D CT images for 45 out of 50 patients. 9 The problem with retrospective displacement sorting is, on the other hand, that data may be insufficient at some couch positions because of variations in the respiratory motion.…”

Section: Introductionmentioning

confidence: 99%

“…These mismatches become visible as artifacts in reconstructed 4D CT images. [1][2][3][4][5][6][7][8] These artifacts appear as undefined or irregular boundaries in the 4D CT images and cause systematic errors in patient contouring and dose calculations. Various studies have shown that the magnitude of artifacts resulting from retrospective displacement sorting is less severe than those resulting from retrospective phase sorting.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Accuracy in the localization of thoracic and abdominal tumors using respiratory displacement, velocity, and phase

Langner

Keall

2009

Medical Physics

View full text Add to dashboard Cite

Current four dimensional ͑4D͒ computed tomography ͑CT͒ reconstruction techniques are retrospectively created based on either the phase or displacement of the respiratory signal. Both techniques have known limitations which cause clinically significant motion artifacts in 4D CT images. These artifacts, which appear as undefined or irregular boundaries in the 4D CT images, cause systematic errors in patient contouring and dose calculations. The aim of this work was to evaluate the reproducibility of tumor position as a function of displacement, phase, and velocity of the respiratory signal, respectively, in order to determine the optimum parameter or combination of parameters to use in order to minimize artifacts in 4D CT images or to accurately deliver radiation to relevant structures during treatment. Method and materials: Estimated tumor centroid position and respiratory signal data were acquired with the Cyberknife Synchrony system for 26 thoracic radiotherapy patients ͑52 fractions͒. A reference respiratory cycle was calculated for each patient. Displacement, phase, and velocity of ten data points were calculated from this reference respiratory cycle, where each point represents an image bin. The corresponding tumor position was then sorted into these image bins if the phase, displacement, simultaneous displacement and phase, or simultaneous displacement and velocity of the respiratory signal were within tolerances of 0.5 mm for displacement and 0.5 mm/ s for velocity, respectively, from the corresponding data of the reference cycle for each image bin. Results: The mean of the standard deviations of tumor positions over all bins and all fractions for the superior-inferior direction were 2.13Ϯ 1.01 mm for phase sorting, 1.20Ϯ 0.76 mm for displacement sorting, 1.20Ϯ 0.71 mm for simultaneous displacement and phase sorting, and 1.10Ϯ 0.71 mm for simultaneous displacement and velocity sorting, with maximum deviations of 43.0, 16.1, 15.5, and 14.1 mm for each scenario, respectively. The same trend was observed for the anterior-posterior and left-right directions. A linear dependence was observed between the mean of the standard deviations of tumor positions over all fractions as a function of the velocity of the respiratory signal at each bin for all the sorting scenarios. A substantially larger gradient for the phase sorting scenario, compared to the other scenarios, suggests that tumor localization will become increasingly less accurate as the velocity of the tumor increases during a breathing cycle, e.g., if the amplitude of motion increases while the period of the respiratory cycle stays constant or during mid inhale or exhale phases of the respiratory cycle. Conclusion: This study illustrates that position of a tumor can be determined more accurately if displacement and velocity are used simultaneously as sorting parameters for 4D CT images or during treatment. A real-time displacement and velocity based 4D CT image sorting method may therefore produce fewer and smaller artifacts in 4D CT images than current r...

show abstract

“…19)], while there have been several improved sorting methods that reduce artifacts. [21][22][23][24][25][26][27][28] This study is the first to quantify the ventilation variation arising from different 4D CT sorting methods. In addition, we also investigated which provides higher physiologic accuracy by comparing with SPECT ventilation (assumed ground truth).…”

Section: Introductionmentioning

confidence: 99%

4D CT lung ventilation images are affected by the 4D CT sorting method

et al. 2013

View full text Add to dashboard Cite

Purpose: Four-dimensional (4D) computed tomography (CT) ventilation imaging is a novel promising technique for lung functional imaging. The current standard 4D CT technique using phase-based sorting frequently results in artifacts, which may deteriorate the accuracy of ventilation imaging. The purpose of this study was to quantify the variability of 4D CT ventilation imaging due to 4D CT sorting. Methods: 4D CT image sets from nine lung cancer patients were each sorted by the phase-based method and anatomic similarity-based method, designed to reduce artifacts, with corresponding ventilation images created for each method. Artifacts in the resulting 4D CT images were quantified with the artifact score which was defined based on the difference between the normalized cross correlation for CT slices within a CT data segment and that for CT slices bordering the interface between adjacent CT data segments. The ventilation variation was quantified using voxel-based Spearman rank correlation coefficients for all lung voxels, and Dice similarity coefficients (DSC) for the spatial overlap of low-functional lung volumes. Furthermore, the correlations with matching single-photon emission CT (SPECT) ventilation images (assumed ground truth) were evaluated for three patients to investigate which sorting method provides higher physiologic accuracy. Results: Anatomic similarity-based sorting reduced 4D CT artifacts compared to phase-based sorting (artifact score, 0.45 ± 0.14 vs 0.58 ± 0.24, p = 0.10 at peak-exhale; 0.63 ± 0.19 vs 0.71 ± 0.31, p = 0.25 at peak-inhale). The voxel-based correlation between the two ventilation images was 0.69 ± 0.26 on average, ranging from 0.03 to 0.85. The DSC was 0.71 ± 0.13 on average. Anatomic similarity-based sorting yielded significantly fewer lung voxels with paradoxical negative ventilation values than phase-based sorting (5.0 ± 2.6% vs 9.7 ± 8.4%, p = 0.05), and improved the correlation with SPECT ventilation regionally. Conclusions: The variability of 4D CT ventilation imaging due to 4D CT sorting was moderate overall and substantial in some cases, suggesting that 4D CT artifacts are an important source of variations in 4D CT ventilation imaging. Reduction of 4D CT artifacts provided more physiologically convincing and accurate ventilation estimates. Further studies are needed to confirm this result.

show abstract

The impact of temporal inaccuracies on 4DCT image quality

Cited by 82 publications

References 29 publications

Direct aperture optimization using an inverse form of back‐projection

Direct aperture optimization using an inverse form of back‐projection

Accuracy in the localization of thoracic and abdominal tumors using respiratory displacement, velocity, and phase

4D CT lung ventilation images are affected by the 4D CT sorting method

Contact Info

Product

Resources

About