Conversion coefficients for the estimation of effective doses in intraoral and panoramic dental radiology from dose-area product (DAP) values were determined by measuring organ-absorbed doses and the corresponding DAP values. Measurements were performed for all standard intraoral radiological projections and standard panoramic examination at different exposure parameters. Organ-absorbed doses were measured using thermoluminescent detectors and an adult anthropomorphic phantom specially designed for dosimetric study in dental radiology. Different techniques for the calculation of effective doses were evaluated. Conversion coefficients derived from this study range from 0.008 to 0.132 microSv mGy(-1) cm(-2) for intraoral radiography and 0.055 to 0.238 microSv mGy(-1) cm(-2) for panoramic radiography.

Multi-shot techniques offer improved resolution and signal-to-noise ratio for diffusion-weighted imaging, but make the acquisition vulnerable to shot-specific phase variations and inter-shot macroscopic motion. Several model-based reconstruction approaches with iterative phase correction have been proposed, but robust macroscopic motion estimation is still challenging. Segmented diffusion imaging with iterative motion-corrected reconstruction (SEDIMENT) uses iteratively refined data-driven shot navigators based on sensitivity encoding to cure phase and rigid in-plane motion artifacts. The iterative scheme is compared in simulations and in vivo with a non-iterative reference algorithm for echo-planar imaging with up to sixfold segmentation. The SEDIMENT framework supports partial Fourier acquisitions and furthermore includes options for data rejection and learning-based modules to improve robustness and convergence.

Purpose To improve the robustness of diffusion‐weighted imaging (DWI) data acquired with segmented simultaneous multi‐slice (SMS) echo‐planar imaging (EPI) against in‐plane and through‐plane rigid motion. Theory and Methods The proposed algorithm incorporates a 3D rigid motion correction and wavelet denoising into the image reconstruction of segmented SMS‐EPI diffusion data. Low‐resolution navigators are used to estimate shot‐specific diffusion phase corruptions and 3D rigid motion parameters through SMS‐to‐volume registration. The shot‐wise rigid motion and phase parameters are integrated into a SENSE‐based full‐volume reconstruction for each diffusion direction. The algorithm is compared to a navigated SMS reconstruction without gross motion correction in simulations and in vivo studies with four‐fold interleaved 3‐SMS diffusion tensor acquisitions. Results Simulations demonstrate high fidelity was achieved in the SMS‐to‐volume registration, with submillimeter registration errors and improved image reconstruction quality. In vivo experiments validate successful artifact reduction in 3D motion‐compromised in vivo scans with a temporal motion resolution of approximately 0.3 s. Conclusion This work demonstrates the feasibility of retrospective 3D rigid motion correction from shot navigators for segmented SMS DWI.

No abstract