Assessment of subjective image quality, contrast to noise ratio and modulation transfer function in the middle ear using a novel full body cone beam computed tomography device

Anssi-Kalle Heikkinen; Valtteri Rissanen; Antti A Aarnisalo; Kristofer Nyman; Saku T Sinkkonen; Juha Koivisto

doi:10.1186/s12880-023-00996-6

Assessment of subjective image quality, contrast to noise ratio and modulation transfer function in the middle ear using a novel full body cone beam computed tomography device

BMC Med Imaging. 2023 Apr 10;23(1):51. doi: 10.1186/s12880-023-00996-6.

Authors

Anssi-Kalle Heikkinen¹, Valtteri Rissanen², Antti A Aarnisalo², Kristofer Nyman³, Saku T Sinkkonen², Juha Koivisto⁴

Affiliations

¹ Department of Otorhinolaryngology-Head and Neck Surgery and Tauno Palva Laboratory, Head and Neck Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland. anssi-kalle.heikkinen@helsinki.fi.
² Department of Otorhinolaryngology-Head and Neck Surgery and Tauno Palva Laboratory, Head and Neck Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
³ Radiology, HUS Diagnostic Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
⁴ Department of Physics, University of Helsinki, Helsinki, Finland.

Abstract

Background: Multi slice computed tomography (MSCT) is the most common used method in middle ear imaging. However, MSCT lacks the ability to distinguish the ossicular chain microstructures in detail resulting in poorer diagnostic outcomes. Novel cone beam computed tomography (CBCT) devices' image resolution is, on the other hand, better than MSCT resolution. The aim of this study was to optimize imaging parameters of a novel full body CBCT device to obtain optimal contrast to noise ratio (CNR) with low effective dose, and to optimize its clinical usability.

Methods: Imaging of five anonymous excised human cadaver temporal bones, the acquisition of the effective doses and the CNR measurements were performed for images acquired on using Planmed XFI® full body CBCT device (Planmed Oy, Helsinki, Finland) with a voxel size of 75 µm. All images acquired from the specimens using 10 different imaging protocols varying from their tube current exposure time product (mAs) and tube voltage (kVp) were analyzed for eight anatomical landmarks and evaluated by three evaluators.

Results: With the exception of protocol with 90 kVp 100 mAs, all other protocols used are competent to image the finest structures. With a moderate effective dose (86.5 µSv), protocol with 90 kV 450 mAs was chosen the best protocol used in this study. A significant correlation between CNR and clinical image quality of the protocols was observed in linear regression model. Using the optimized imaging parameters, we were able to distinguish even the most delicate middle ear structures in 2D images and produce accurate 3D reconstructions.

Conclusions: In this ex vivo experiment, the new Planmed XFI® full body CBCT device produced excellent 2D resolution and easily created 3D reconstructions in middle ear imaging with moderate effective doses. This device would be suitable for middle ear diagnostics and for e.g., preoperative planning. Furthermore, the results of this study can be used to optimize the effective dose by selecting appropriate exposure parameters depending on the diagnostic task.

Keywords: 3D reconstruction; CNR; Cone beam computed tomography; Contrast to noise ratio; Full body CBCT; Middle ear imaging; Subjective image quality.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Cone-Beam Computed Tomography* / methods
Ear, Middle / diagnostic imaging
Humans
Phantoms, Imaging
Radiation Dosage
Tomography, X-Ray Computed* / methods