Reducing 4DCBCT imaging time and dose: the first implementation of variable gantry speed 4DCBCT on a linear accelerator

O’Brien, Ricky; Stankovic, Uros; Sonke, Jan‐Jakob; Keall, Paul J.

doi:10.1088/1361-6560/62/11/4300

Cited by 13 publications

(21 citation statements)

References 28 publications

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“…We have previously demonstrated the feasibility of modifying the gantry velocity and projection time interval in response to a patient's real‐time respiratory signal on an Elekta linac, indicating the potential to move our dual adaptive protocol from simulation through to experimental realization. The movements of the gantry are smooth, not requiring rapid repositioning, and are within the mechanical constraints of a standard linac.…”

Section: Discussionmentioning

confidence: 99%

“…That is, for cardiaconly motion guided CBCT imaging we considered the effect of arrhythmias on image quality and scan time, 17 while for respiratory-only motion guided CBCT imaging we looked to encompass irregular breathing by examining 112 breathing traces from 24 lung cancer patients. 14 We have previously demonstrated the feasibility of modifying the gantry velocity and projection time interval in response to a patient's real-time respiratory signal on an Elekta linac, 15,16 indicating the potential to move our dual adaptive protocol from simulation through to experimental realization. The movements of the gantry are smooth, not requiring rapid repositioning, and are within the mechanical constraints of a standard linac.…”

Section: Discussionmentioning

confidence: 99%

“…Previously, we developed and tested methods to regulate the velocity of the gantry and projection time interval in response to the patient's real‐time respiratory signal . Importantly, these methods have already been implemented on an Elekta Synergy linear accelerator (linac) for respiratory motion guided imaging, displaying significant improvements in the image quality for the same dose as well as enabling up to a 70% reduction in imaging dose for the same original image quality .…”

Section: Introductionmentioning

confidence: 99%

“…Previously, we developed and tested methods to regulate the velocity of the gantry and projection time interval in response to the patient's real-time respiratory signal. [13][14][15] Importantly, these methods have already been implemented on an Elekta Synergy linear accelerator (linac) for respiratory motion guided imaging, displaying significant improvements in the image quality for the same dose as well as enabling up to a 70% reduction in imaging dose for the same original image quality. 16 Extending this concept to conduct cardiac motion guided imaging we have developed a gated CBCT imaging protocol, which regulates the gantry velocity and projection time interval in accordance with the patient's realtime electrocardiogram (ECG), under breath hold conditions.…”

Section: Introductionmentioning

confidence: 99%

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Dual cardiac and respiratory gated thoracic imaging via adaptive gantry velocity and projection rate modulation on a linear accelerator: A Proof‐of‐Concept Simulation Study

et al. 2019

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Purpose Cardiac motion is typically not accounted for during pretreatment imaging for central lung and mediastinal tumors. However, cardiac induced tumor motion averages 5.8 mm for esophageal tumors and 3–5 mm for some lung tumors, which can result in positioning errors. Our aim is to reduce both cardiac‐ and respiratory‐induced motion artifacts in thoracic cone beam computed tomography (CBCT) images through gantry velocity and projection rate modulation on a standard linear accelerator (linac). Methods The acquisition of dual cardiac and respiratory gated CBCT thoracic images was simulated using the XCAT phantom with patient‐measured respiratory and ECG traces. The gantry velocity and projection rate were modulated based on the cardiac and respiratory signals to maximize the angular consistency between adjacent projections in the gated cardiac‐respiratory bin. The mechanical limitations of a gantry‐mounted CBCT system were investigated. For our protocol, images were acquired during the 60%–80% window of cardiac phase and 20% displacement either side of peak exhale of the respiratory cycle. The comparator method was the respiratory‐only gated CBCT acquisition with constant gantry speed and projection rate in routine use for respiratory correlated four‐dimensional (4D) CBCT. All images were reconstructed using the Feldkamp‐Davis‐Kress (FDK) algorithm. The methods were compared in terms of image sharpness as measured using the edge response width (ERW) and contrast as measured using the contrast to noise ratio (CNR). The effects of the total number of projections acquired and magnitude of cardiac motion on scan time and image quality were also investigated. Results Median total scan times with our protocol ranged from 117 s (40 projections) through to 296 s (100 projections), compared with 240 s for the conventional protocol (1320 projections). The scan times were dictated by the number of projections acquired, heart rate, length of the respiratory cycle and mechanical constraints of the CBCT system. Our protocol was able to provide between 8% and 43% decrease in the median value of the ERW in the anterior/posterior (AP) direction across the 17 traces when there was 0.5 cm of cardiac motion and between 35% and 64% decrease when there was 1.0 cm of cardiac motion over conventional acquisition. In the superior‐inferior (SI) direction, our protocol was able to provide between 22% and 26% decrease in the median value of the ERW across the 17 traces when there was 0.5 cm of cardiac motion and between 30% and 35% decrease when there was 1.0 cm of cardiac motion over conventional acquisition. The magnitude of the cardiac motion did not have an observable effect on the median value of the CNR. Across all 17 traces, our adaptive protocol produced noticeably more consistent, albeit lower CNR values compared with conventional acquisition. Conclusion For the first time, the potential of adapting CBCT image acquisition to changes in the patient's cardiac and respiratory rates simultaneously for applications in radiotherapy was ...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Dual cardiac and respiratory gated thoracic imaging via adaptive gantry velocity and projection rate modulation on a linear accelerator: A Proof‐of‐Concept Simulation Study

et al. 2019

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“…It has been demonstrated that by varying the gantry speed and imaging frequency in response to changes in the patient's real-time respiratory signal, the imaging dose can be reduced by 50% to 70%. 7 IMRT has become an important radiation-delivery technique in the management of H&N cancers. It conforms the prescribed doses to the target volumes of complex shapes while sparing the adjacent critical structures without compromising the target coverage.…”

Section: Human Papillomavirus and Hnscc Cancersmentioning

confidence: 99%

Head and Neck Cancers: Advantages of Advanced Radiation Therapy and Importance of Supportive Care

Spencer

2018

J Natl Compr Canc Netw

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For more than a decade, the incidence of head and neck cancers has been increasing in the United States. Worldwide, they are the ninth most common cancer. Today, newer advances in radiotherapy (RT), such as fractionation, 4-dimensional cone-beam CT, and intensity-modulated RT, have provided clinicians with the opportunity for improved patient outcomes. At the NCCN 23rd Annual Conference, Sharon Spencer, MD, described the advantages of advances in RT and the means to mitigate untoward side effects.

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Faster and lower dose imaging: evaluating adaptive, constant gantry velocity and angular separation in fast low‐dose 4D cone beam CT imaging

et al. 2023

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BackgroundThe adoption of four‐dimensional cone beam computed tomography (4DCBCT) for image‐guided lung cancer radiotherapy is increasing, especially for hypofractionated treatments. However, the drawbacks of 4DCBCT include long scan times (∼240 s), inconsistent image quality, higher imaging dose than necessary, and streaking artifacts. With the emergence of linear accelerators that can acquire 4DCBCT scans in a short period of time (9.2 s) there is a need to examine the impact that these very fast gantry rotations have on 4DCBCT image quality.PurposeThis study investigates the impact of gantry velocity and angular separation between x‐ray projections on image quality and its implication for fast low‐dose 4DCBCT with emerging systems, such as the Varian Halcyon that provide fast gantry rotation and imaging. Large and uneven angular separation between x‐ray projections is known to reduce 4DCBCT image quality through increased streaking artifacts. However, it is not known when angular separation starts degrading image quality. The study assesses the impact of constant and adaptive gantry velocity and determines the level when angular gaps impair image quality using state‐of‐the‐art reconstruction methods.MethodsThis study considers fast low‐dose 4DCBCT acquisitions (60–80 s, 200‐projection scans). To assess the impact of adaptive gantry rotations, the angular position of x‐ray projections from adaptive 4DCBCT acquisitions from a 30‐patient clinical trial were analyzed (referred to as patient angular gaps). To assess the impact of angular gaps, variable and static angular gaps (20°, 30°, 40°) were introduced into evenly separated 200 projections (ideal angular separation). To simulate fast gantry rotations, which are on emerging linacs, constant gantry velocity acquisitions (9.2 s, 60 s, 120 s, 240 s) were simulated by sampling x‐ray projections at constant intervals using the patient breathing traces from the ADAPT clinical trial (ACTRN12618001440213). The 4D Extended Cardiac‐Torso (XCAT) digital phantom was used to simulate projections to remove patient‐specific image quality variables.Image reconstruction was performed using Feldkamp‐Davis‐Kress (FDK), McKinnon‐Bates (MKB), and Motion‐Compensated‐MKB (MCMKB) algorithms. Image quality was assessed using Structural Similarity‐Index‐Measure (SSIM), Contrast‐to‐Noise‐Ratio (CNR), Signal‐to‐Noise‐Ratio (SNR), Tissue‐Interface‐Width‐Diaphragm (TIW‐D), and Tissue‐Interface‐Width‐Tumor (TIW‐T).ResultsPatient angular gaps and variable angular gap reconstructions produced similar results to ideal angular separation reconstructions, while static angular gap reconstructions produced lower image quality metrics. For MCMKB‐reconstructions, average patient angular gaps produced SSIM‐0.98, CNR‐13.6, SNR‐34.8, TIW‐D‐1.5 mm, and TIW‐T‐2.0 mm, static angular gap 40° produced SSIM‐0.92, CNR‐6.8, SNR‐6.7, TIW‐D‐5.7 mm, and TIW‐T‐5.9 mm and ideal produced SSIM‐1.00, CNR‐13.6, SNR‐34.8, TIW‐D‐1.5 mm, and TIW‐T‐2.0 mm. All constant gantry velocity reconstructions produced lower image quality metrics than ideal angular separation reconstructions regardless of the acquisition time. Motion compensated reconstruction (MCMKB) produced the highest contrast images with low streaking artifacts.ConclusionVery fast 4DCBCT scans can be acquired provided that the entire scan range is adaptively sampled, and motion‐compensated reconstruction is performed. Importantly, the angular separation between x‐ray projections within each individual respiratory bin had minimal effect on the image quality of fast low‐dose 4DCBCT imaging. The results will assist the development of future 4DCBCT acquisition protocols that can now be achieved in very short time frames with emerging linear accelerators.

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Reducing 4DCBCT imaging time and dose: the first implementation of variable gantry speed 4DCBCT on a linear accelerator

Cited by 13 publications

References 28 publications

Dual cardiac and respiratory gated thoracic imaging via adaptive gantry velocity and projection rate modulation on a linear accelerator: A Proof‐of‐Concept Simulation Study

Dual cardiac and respiratory gated thoracic imaging via adaptive gantry velocity and projection rate modulation on a linear accelerator: A Proof‐of‐Concept Simulation Study

Head and Neck Cancers: Advantages of Advanced Radiation Therapy and Importance of Supportive Care

Faster and lower dose imaging: evaluating adaptive, constant gantry velocity and angular separation in fast low‐dose 4D cone beam CT imaging

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