Image quality and dose characteristics for an O‐arm intraoperative imaging system with model‐based image reconstruction

Uneri, Ali; Zhang, X.; Yi, Thomas; Stayman, J. Webster; Helm, Patrick A.; Theodore, Nicholas; Siewerdsen, Jeffrey H.

doi:10.1002/mp.13167

Cited by 22 publications

(27 citation statements)

References 69 publications

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“…For the head protocols, the dose for manufacturer‐specified clinical protocols was 0.8–4.7 mGy (~0.15 mGy/mAs), and the dose for the custom protocols investigated for potential low‐contrast visualization (e.g., intracranial hemorrhage) was 8.3–40 mGy. As points of reference, the dose reported for head scan protocols on other systems include: 1.3–6.8 mGy (Vision RFD 3D, Ziehm); 6.7–67 mGy (O‐arm, Medtronic); and ~30–50 mGy (diagnostic MDCT), recognizing that such dose values should not be interpreted in isolation, but in relation to the imaging task — for example, lower dose levels may correspond to fast, lower‐quality protocols suitable to bone imaging, and higher dose protocols may correspond to tasks requiring low‐contrast visualization (e.g., intracranial hemorrhage).…”

Section: Resultsmentioning

confidence: 99%

“…For the body protocols, the dose for manufacturer‐specified clinical protocols was 6.3–38 mGy (~0.06 mGy/mAs), and the dose for the custom protocols investigated for lower‐dose, high‐contrast visualization (e.g., bone and surgical instrumentation) was 0.9–4.9 mGy. As points of reference, the dose reported for body scan protocols on other systems include: 14.8–36.7 mGy (Vision RFD 3D, Ziehm); 6.7–27 mGy (O‐arm, Medtronic); and ~7–20 mGy (diagnostic MDCT), again recognizing that such dose values should not be interpreted in isolation, but in relation to the imaging task.…”

Section: Resultsmentioning

confidence: 99%

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A mobile isocentric C‐arm for intraoperative cone‐beam CT: Technical assessment of dose and 3D imaging performance

et al. 2020

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Purpose To characterize the radiation dose and three‐dimensional (3D) imaging performance of a recently developed mobile, isocentric C‐arm equipped with a flat‐panel detector (FPD) for intraoperative cone‐beam computed tomography (CBCT) (Cios Spin 3D, Siemens Healthineers) and to identify potential improvements in 3D imaging protocols for pertinent imaging tasks. Methods The C‐arm features a 30 × 30 cm2 FPD and isocentric gantry with computer‐controlled motorization of rotation (0–195°), angulation (±220°), and height (0–45 cm). Geometric calibration was assessed in terms of 9 degrees of freedom of the x‐ray source and detector in CBCT scans, and the reproducibility of geometric calibration was evaluated. Standard and custom scan protocols were evaluated, with variation in the number of projections (100–400) and mAs per view (0.05–1.65 mAs). Image reconstruction was based on 3D filtered backprojection using “smooth,” “normal,” and “sharp” reconstruction filters as well as a custom, two‐dimensional 2D isotropic filter. Imaging performance was evaluated in terms of uniformity, gray value correspondence with Hounsfield units (HU), contrast, noise (noise‐power spectrum, NPS), spatial resolution (modulation transfer function, MTF), and noise‐equivalent quanta (NEQ). Performance tradeoffs among protocols were visualized in anthropomorphic phantoms for various anatomical sites and imaging tasks. Results Geometric calibration showed a high degree of reproducibility despite ~19 mm gantry flex over a nominal semicircular orbit. The dose for a CBCT scan varied from ~0.8–4.7 mGy for head protocols to ~6–38 mGy for body protocols. The MTF was consistent with sub‐mm spatial resolution, with f10 (frequency at which MTF = 10%) equal to 0.64 mm−1, 1.0 mm−1, and 1.5 mm−1 for smooth, standard, and sharp filters respectively. Implementation of a custom 2D isotropic filter improved CNR ~ 50–60% for both head and body protocols and provided more isotropic resolution and noise characteristics. The NPS and NEQ quantified the 3D noise performance and provided a guide to protocol selection, confirmed in images of anthropomorphic phantoms. Alternative scan protocols were identified according to body site and task — for example, lower‐dose body protocols (<3 mGy) sufficient for visualization of bone structures. Conclusion The studies provided objective assessment of the dose and 3D imaging performance of a new C‐arm, offering an important basis for clinical deployment and a benchmark for quality assurance. Modifications to standard 3D imaging protocols were identified that may improve performance or reduce radiation dose for pertinent imaging tasks.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

A mobile isocentric C‐arm for intraoperative cone‐beam CT: Technical assessment of dose and 3D imaging performance

et al. 2020

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“…FBP reconstruction was based on the Feldkamp–Davis–Kress algorithm using the same elliptical cylinder support to extrapolate projection data outside the FOV and reduce truncation artifacts . A 2D Hann filter with adjustable cutoff frequency

f_{c}

in both

u

and

v

directions was implemented as in Uneri et al to give more isotropic noise and resolution characteristics.…”

Section: Methodsmentioning

confidence: 99%

“…All images were reconstructed using KC-Recon and compared to images reconstructed by the modified 3D FBP algorithm detailed in previous work. 36 Preinstrumentation images (for which KC-Recon reduces simply to PWLS, detailed in Section 2.B.2) were evaluated with respect to soft-tissue visibility, and postinstrumentation images were evaluated with respect to localization and visualization of surgical instrumentation (viz., spinal pedicle screws) and surrounding tissues. For spine discectomy or decompression procedures not involving instrumentation (Patients 1-5 in Table I), only "preinstrumentation" scans were acquired.…”

Section: A2 Clinical Studymentioning

confidence: 99%

Known‐component 3D image reconstruction for improved intraoperative imaging in spine surgery: A clinical pilot study

et al. 2019

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Purpose Intraoperative imaging plays an increased role in support of surgical guidance and quality assurance for interventional approaches. However, image quality sufficient to detect complications and provide quantitative assessment of the surgical product is often confounded by image noise and artifacts. In this work, we translated a three‐dimensional model‐based image reconstruction (referred to as “Known‐Component Reconstruction,” KC‐Recon) for the first time to clinical studies with the aim of resolving both limitations. Methods KC‐Recon builds upon a penalized weighted least‐squares (PWLS) method by incorporating models of surgical instrumentation (“known components”) within a joint image registration–reconstruction process to improve image quality. Under IRB approval, a clinical pilot study was conducted with 17 spine surgery patients imaged under informed consent using the O‐arm cone‐beam CT system (Medtronic, Littleton MA) before and after spinal instrumentation. Volumetric images were generated for each patient using KC‐Recon in comparison to conventional filtered backprojection (FBP). Imaging performance prior to instrumentation (“preinstrumentation”) was evaluated in terms of soft‐tissue contrast‐to‐noise ratio (CNR) and spatial resolution. The quality of images obtained after the instrumentation (“postinstrumentation”) was assessed by quantifying the magnitude of metal artifacts (blooming and streaks) arising from pedicle screws. The potential low‐dose advantages of the algorithm were tested by simulating low‐dose data (down to one‐tenth of the dose of standard protocols) from images acquired at normal dose. Results Preinstrumentation images (at normal clinical dose and matched resolution) exhibited an average 24.0% increase in soft‐tissue CNR with KC‐Recon compared to FBP (N = 16, P = 0.02), improving visualization of paraspinal muscles, major vessels, and other soft‐tissues about the spine and abdomen. For a total of 72 screws in postinstrumentation images, KC‐Recon yielded a significant reduction in metal artifacts: 66.3% reduction in overestimation of screw shaft width due to blooming (P < 0.0001) and reduction in streaks at the screw tip (65.8% increase in attenuation accuracy, P < 0.0001), enabling clearer depiction of the screw within the pedicle and vertebral body for an assessment of breach. Depending on the imaging task, dose reduction up to an order of magnitude appeared feasible while maintaining soft‐tissue visibility and metal artifact reduction. Conclusions KC‐Recon offers a promising means to improve visualization in the presence of surgical instrumentation and reduce patient dose in image‐guided procedures. The improved soft‐tissue visibility could facilitate the use of cone‐beam CT to soft‐tissue surgeries, and the ability to precisely quantify and visualize instrument placement could provide a valuable check against complications in the operating room (cf., postoperative CT).

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“…Cone‐beam computed tomography (CBCT) has become an increasingly prevalent imaging technology over the last two decades, manifesting in a broad variety of physical configurations (e.g., C‐arms, U‐arms, and O‐arms in mobile and/or fixed‐room systems) and clinical applications (e.g., dental, craniomaxillofacial, ENT, breast, MSK, image‐guided surgery (IGS), and radiation therapy [IGRT]). The dose and imaging performance characteristics of CBCT systems are distinct from those of helical multi‐detector CT (MDCT), and standard test tools, methodology, and metrology developed over the last 50 yr for CT/MDCT are not universally applicable to CBCT.…”

Section: Introductionmentioning

confidence: 99%

Cone‐beam CT dose and imaging performance evaluation with a modular, multipurpose phantom

et al. 2019

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Purpose A modular phantom for dosimetry and imaging performance evaluation in cone‐beam computed tomography (CBCT) is reported, providing a tool for quantitative technical assessment that can be adapted to a broad variety of CBCT imaging configurations and clinical applications. Methods The phantom presents a set of modules that can be ordered in various configurations suitable to a particular CBCT system. Modules include slabs containing a uniform medium, low‐contrast inserts, line‐spread features, and disk features suitable to measurement of image uniformity, noise, noise‐power spectrum (NPS), contrast, contrast‐to‐noise ratio (CNR), Hounsfield (HU) accuracy, linearity, spatial resolution modulation transfer function (MTF), and magnitude of cone‐beam artifact. Automated software recognizes the phantom configuration in DICOM images and provides structured reporting of such test measures. In any modular configuration, the phantom permits measurement of air kerma in central and peripheral locations with an air ionization chamber (e.g., Farmer chamber). The utility and adaptability of the phantom were demonstrated across a spectrum of CBCT systems, including scanners for orthopaedic imaging (Carestream OnSight 3D, Rochester NY), breast imaging (Doheny prototype, UC Davis), image‐guided surgery (IGS, Medtronic O‐arm, Littleton MA), angiography (Siemens Artis Zeego, Forcheim Germany), and image‐guided radiation therapy (IGRT, Elekta Synergy XVI, Stockholm Sweden). Results The phantom provided a consistent platform for quantitative assessment of dose and imaging performance compatible with a broad spectrum of CBCT systems. The purpose of the survey was not to obtain head‐to‐head performance comparison of systems designed for such distinct clinical applications. Rather, the survey demonstrated the suitability of the phantom to a broad spectrum of systems in a manner that provides characterization pertinent to disparate applications and imaging tasks. For example: the orthopaedic CBCT system (pertinent clinical tasks relating to high‐resolution bone imaging) was shown to achieve MTF consistent with imaging of high‐contrast trabecular bone structures (i.e., the MTF reduced to 10% at spatial frequency, f10 = 1.2 mm−1); the breast system (even higher‐resolution imaging of microcalcifications) exhibited f10 = 2.2 mm−1; the IGS system (tasks including both bone and soft‐tissue contrast resolution) provided f10 = 0.9 mm−1 and soft‐tissue CNR = 1.64; the angiography system (soft‐tissue body interventions) demonstrated CNR = 1.2 in soft tissues approximating liver lesions; and the IGRT system (pertinent tasks emphasizing HU linearity and image uniformity) showed linear response with HU values (R2 = 1), with a cupping artifact (tcup = 5.8%) due to x‐ray scatter. Conclusions The phantom provides an adaptable, quantitative basis for CBCT dosimetry and imaging performance evaluation suitable to a broad variety of CBCT systems. The dosimetry and image quality metrics are consistent with up‐to‐date methods for rigorous, quantitative,...

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Image quality and dose characteristics for an O‐arm intraoperative imaging system with model‐based image reconstruction

Cited by 22 publications

References 69 publications

A mobile isocentric C‐arm for intraoperative cone‐beam CT: Technical assessment of dose and 3D imaging performance

A mobile isocentric C‐arm for intraoperative cone‐beam CT: Technical assessment of dose and 3D imaging performance

Known‐component 3D image reconstruction for improved intraoperative imaging in spine surgery: A clinical pilot study

Cone‐beam CT dose and imaging performance evaluation with a modular, multipurpose phantom

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