Mr. Clemens Schmid Profile

Clemens Schmid

SPIE Involvement:

Author

Publications (3)

This will count as one of your downloads.

You will have access to both the presentation and article (if available).

DOWNLOAD NOW

This content is available for download via your institution's subscription. To access this item, please sign in to your personal account.

Email or Username Forgot your username?

Password Forgot your password?

Show

Keep me signed in

No SPIE account? Create an account

Proceedings Article | 18 October 2022 Open Access

Dark-field imaging on a clinical CT system: performance and potential based on first results

Nikolai Gustschin, Manuel Viermetz, Clemens Schmid, Jakob Hausele, Frank Bergner, Tobias Lasser, Thomas Koehler, Franz Pfeiffer

Proceedings Volume 12304, 1230403 (2022) https://doi.org/10.1117/12.2646988

KEYWORDS: Signal attenuation, Lung, Scattering, Tissues, Imaging systems, X-rays, Interferometers, X-ray computed tomography, Prototyping

Read Abstract +

X-ray computed tomography (CT) has been established as a daily tool in clinical diagnostics and has been continuously refined by more recent innovations in the last years. These systems are, however, limited by fundamental constraints since they are only capable of mapping X-ray attenuation differences in the tissue. Phase-contrast and dark-field imaging provide complementary contrast, which originates from physically different interaction processes of X-rays with matter. Particularly the dark-field signal is considered to have significant diagnostic potential since it is capable to retrieve micro-structural information below the actual resolution limit of the imaging system. This was demonstrated in various laboratory setups and recently also in the fist study with human patients in a clinical radiography system based on a grating interferometer. In a recent work, we presented the first implementation of such an X-ray interferometer into a clinical CT gantry. Upscaling and adapting this technology for a rotating CT gantry involves several challenges and tradeoffs ranging from limitations in interferometer design over fast, continuous signal acquisition requirements to tolerances in applied patient dose. In this work we discuss the performance of the first clinical dark-field CT prototype. For this purpose, we present results of our phantom studies which were designed to evaluate whether and how the dark-field contrast generated by the system is capable to provide additional structural sample information. The key aspects include the possibility of quantitative imaging and a gradual approach to simulate results that come as close as possible to a real application in a human patient.

DOWNLOAD PAPER

Proceedings Article | 18 October 2022 Open Access

Dark-field imaging on a clinical CT system: sample data processing and reconstruction

Jakob Haeusele, Clemens Schmid, Manuel Viermetz, Nikolai Gustschin, Tobias Lasser, Frank Bergner, Thomas Koehler, Franz Pfeiffer

Proceedings Volume 12304, 1230424 (2022) https://doi.org/10.1117/12.2646440

KEYWORDS: Imaging systems, Interferometers, Data processing, X-rays, X-ray imaging, Lung, Statistical analysis, Signal attenuation

Read Abstract +

Grating-based phase-contrast and dark-field X-ray imaging is a promising technology for improving the diagnosis and imaging capabilities of breast cancer and lung diseases. While traditional X-ray techniques only consider the attenuation coefficient, phase-contrast and dark-field imaging are also capable of measuring the refractive index decrement and the so-called linear diffusion coefficient, a measure of a sample’s small-angle scattering strength. Consequently, the technique provides additional information about the micro-structure of a sample. While it is already possible to perform human chest dark-field radiography, it is assumed that its diagnostic value increases when performed in a tomographic setup. The thereby acquired three-dimensional mappings of the three modalities yield detailed information about morphological changes without being obscured by overlaying structures. This work presents the sample data processing and reconstruction pipeline of the first human-sized clinical dark-field CT system. In this novel setting we require a processing concept which is (1) compatible with continuous rotation, (2) can compensate for perturbances induced by system vibrations, and (3) still enables short processing and reconstruction times. An advanced sliding window approach was chosen for the sample data extraction to meet requirements (1) and (3). Furthermore, we present the corrective measures that have to be applied in the employed processing and reconstruction algorithms to mitigate the effects of vibrations and deformations of the interferometer gratings. The developed techniques are shown to successfully reduce the emergence of artefacts in the reconstructed images.

DOWNLOAD PAPER

Proceedings Article | 18 October 2022 Open Access

Dark-field imaging on a clinical CT system: realization of Talbot-Lau interferometry in a gantry

Manuel Viermetz, Nikolai Gustschin, Clemens Schmid, Jakob Haeusele, Roland Proksa, Thomas Koehler, Franz Pfeiffer

Proceedings Volume 12304, 1230402 (2022) https://doi.org/10.1117/12.2646439

KEYWORDS: Interferometers, X-ray computed tomography, Imaging systems, Signal attenuation, X-ray sources, Visibility, Scattering

Read Abstract +

Computed tomography (CT) is a foundation of modern clinical diagnostics but it presently only retrieves information from X-rays attenuation. However, it is known that micro structural texture or porosity – which is well below the spatial resolution of CT – can be revealed by grating-based dark-field imaging. Diagnostic value of this sub-resolution tissue information has been demonstrated in pre-clinical studies on small-animal disease models and recently also in a first clinical radiography system.¹ These studies show that dark-field imaging is particularly useful for early detection and staging of lung diseases. While dark-field CT is regularly realized in laboratory environment, the transfer to human scale and bringing it to clinical application poses several technical challenges. Switching from a step-and-shoot acquisition to a mode where the gantry and acquisition operate continuously as well as reducing scan times to below seconds and ensuring stability against vibrations are key concerns when it comes to the translation of the established laboratory dark-field technology to full-body medical CT. In,² we recently demonstrated the first dark-field CT implementation, which collectively solves these roadblocks and therefore is a milestone in the development of clinical CT imaging. The prototype we present allows to reconstruct the attenuation and dark-field channels of a human thorax phantom from a one second long acquisition and covers a 45 cm diameter field of view. In this work, we present how the first dark-field CT prototype works and focus particularly on the technical design, optimized design of the gratings for CT application and the first characterization of the interferometer in the rotating gantry. We discuss which steps where particularly important for the realization and where we see potential for further improvements. These results provide key insights for future dark-field CT implementations.

DOWNLOAD PAPER

My Library

You currently do not have any folders to save your paper to! Create a new folder below.

Folder Name

Folder Description

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks. You are receiving this notice because your organization may not have SPIE eBooks access.*

*Shibboleth/Open Athens users─please sign in to access your institution's subscriptions.

To obtain this item, you may purchase the complete book in print or electronic format on SPIE.org.

ORGANIZATIONAL
Sign in with credentials provided by your organization.

Organizational Username

Organizational Password

Show/Hide Password

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available

Members:

Non-members: ADD TO CART

Keywords/Phrases

Search In:

Publication Years