The first-in-human implementation of adaptive 4D cone beam CT for lung cancer radiotherapy: 4DCBCT in less time with less dose

O’Brien, Ricky; Dillon, Owen; Lau, Benjamin K.; George, Armia; Smith, Sandie; Wallis, Andrew; Sonke, Jan‐Jakob; Keall, P.; Vinod, Shalini

doi:10.1016/j.radonc.2021.05.021

Cited by 6 publications

(13 citation statements)

References 34 publications

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“…The ADAPT clinical trial focused on pre‐treatment 4DCBCT for lung cancer radiotherapy 21 . For two treatment fractions delivered, the patient cohort received a conventional 1320 project, 4 min, 4DCBCT scan for alignment and radiotherapy treatment as per routine standard of care.…”

Section: Methodsmentioning

confidence: 99%

“…The ADAPT clinical trial focused on pre-treatment 4DCBCT for lung cancer radiotherapy. 21 For two treatment fractions delivered, the patient cohort received a conventional 1320 project, 4 min, 4DCBCT scan for alignment and radiotherapy treatment as per routine standard of care. After the completion of the radiotherapy treatment, the patient cohort immediately received two additional adaptive 4DCBCT scans.…”

Section: Patient Breathing Data Used To Simulate Acquisition: the Ada...mentioning

confidence: 99%

“…[18][19][20] In addition to developing specialized reconstruction algorithms, adapting the gantry velocity and projection time interval between projections has been investigated as a pathway to reducing 4DCBCT imaging dose and scan time. One such example is adaptive 4DCBCT 21,22 (referred to in some literature as respiratory motion guided 4DCBCT or RMG-4DCBCT [23][24][25][26][27] ), which monitors a patient's breathing signal and modulates gantry velocity and projection time interval in real time. Combining adaptive 4DCBCT with motioncompensated reconstruction algorithms has enabled imaging dose to be reduced by 85% and scan time to be reduced by up to 75%.…”

Section: Introductionmentioning

confidence: 99%

“…22 Most recently, the feasibility of implementing adaptive 4DCBCT techniques in a clinical setting, has been examined in the Adaptive CT Acquisition for Personalized Thoracic imaging (ADAPT) clinical trial (ACTRN12618001440213). 21,22,28 A pillar for the success of adaptive 4DCBCT is an even angular separation of projections across all respiratory phases. However, this is not always trivial to achieve.…”

Section: Introductionmentioning

confidence: 99%

“…Combining adaptive 4DCBCT with motion‐compensated reconstruction algorithms has enabled imaging dose to be reduced by 85% and scan time to be reduced by up to 75% 22 . Most recently, the feasibility of implementing adaptive 4DCBCT techniques in a clinical setting, has been examined in the Adaptive CT Acquisition for Personalized Thoracic imaging (ADAPT) clinical trial (ACTRN12618001440213) 21,22,28 …”

Section: Introductionmentioning

confidence: 99%

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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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Section: Methodsmentioning

confidence: 99%

Section: Patient Breathing Data Used To Simulate Acquisition: the Ada...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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A review on 4D cone‐beam CT (4D‐CBCT) in radiation therapy: Technical advances and clinical applications

Zhang,

Jiang,

Zhang

et al. 2024

Medical Physics

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Cone‐beam CT (CBCT) is the most commonly used onboard imaging technique for target localization in radiation therapy. Conventional 3D CBCT acquires x‐ray cone‐beam projections at multiple angles around the patient to reconstruct 3D images of the patient in the treatment room. However, despite its wide usage, 3D CBCT is limited in imaging disease sites affected by respiratory motions or other dynamic changes within the body, as it lacks time‐resolved information. To overcome this limitation, 4D‐CBCT was developed to incorporate a time dimension in the imaging to account for the patient's motion during the acquisitions. For example, respiration‐correlated 4D‐CBCT divides the breathing cycles into different phase bins and reconstructs 3D images for each phase bin, ultimately generating a complete set of 4D images. 4D‐CBCT is valuable for localizing tumors in the thoracic and abdominal regions where the localization accuracy is affected by respiratory motions. This is especially important for hypofractionated stereotactic body radiation therapy (SBRT), which delivers much higher fractional doses in fewer fractions than conventional fractionated treatments. Nonetheless, 4D‐CBCT does face certain limitations, including long scanning times, high imaging doses, and compromised image quality due to the necessity of acquiring sufficient x‐ray projections for each respiratory phase. In order to address these challenges, numerous methods have been developed to achieve fast, low‐dose, and high‐quality 4D‐CBCT. This paper aims to review the technical developments surrounding 4D‐CBCT comprehensively. It will explore conventional algorithms and recent deep learning‐based approaches, delving into their capabilities and limitations. Additionally, the paper will discuss the potential clinical applications of 4D‐CBCT and outline a future roadmap, highlighting areas for further research and development. Through this exploration, the readers will better understand 4D‐CBCT's capabilities and potential to enhance radiation therapy.

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X-ray source arrays for volumetric imaging during radiotherapy treatment

Dillon

Reynolds

O’Brien³

2023

Sci Rep

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This work presents a novel hardware configuration for radiotherapy systems to enable fast 3D X-ray imaging before and during treatment delivery. Standard external beam radiotherapy linear accelerators (linacs) have a single X-ray source and detector located at ± 90° from the treatment beam respectively. The entire system can be rotated around the patient acquiring multiple 2D X-ray images to create a 3D cone-beam Computed Tomography (CBCT) image before treatment delivery to ensure the tumour and surrounding organs align with the treatment plan. Scanning with a single source is slow relative to patient respiration or breath holds and cannot be performed during treatment delivery, limiting treatment delivery accuracy in the presence of patient motion and excluding some patients from concentrated treatment plans that would be otherwise expected to have improved outcomes. This simulation study investigated whether recent advances in carbon nanotube (CNT) field emission source arrays, high frame rate (60 Hz) flat panel detectors and compressed sensing reconstruction algorithms could circumvent imaging limitations of current linacs. We investigated a novel hardware configuration incorporating source arrays and high frame rate detectors into an otherwise standard linac. We investigated four potential pre-treatment scan protocols that could be achieved in a 17 s breath hold or 2–10 1 s breath holds. Finally, we demonstrated for the first time volumetric X-ray imaging during treatment delivery by using source arrays, high frame rate detectors and compressed sensing. Image quality was assessed quantitatively over the CBCT geometric field of view as well as across each axis through the tumour centroid. Our results demonstrate that source array imaging enables larger volumes to be imaged with acquisitions as short as 1 s albeit with reduced image quality arising from lower photon flux and shorter imaging arcs.

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The first-in-human implementation of adaptive 4D cone beam CT for lung cancer radiotherapy: 4DCBCT in less time with less dose

Cited by 6 publications

References 34 publications

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

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

A review on 4D cone‐beam CT (4D‐CBCT) in radiation therapy: Technical advances and clinical applications

X-ray source arrays for volumetric imaging during radiotherapy treatment

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