1. To learn about the basics of dual-energy CT (DECT).
2. To understand today's photon counting detector technology.
3. To learn how DECT is applied in clinical practice.
CT dual energy publications have heavily increased in the last years. The trend seems to be continuing since PubMed has found, from Jan 2015 until Nov 2017, around 1000 peer review abstracts. Publications on phantom simulation (for algorithm verification) and patient's study regarding the most important area of diagnostic have been published sourcing from CT imaging and Hybrid Imaging (PET CT for examples). Bone and high density tissue evaluation are one of the most important application with high density artifact reduction, materials analysis based on attenuation spectra observed, tumor analysis and no contrast imaging application. A lot of technological solutions have been introduced during the last years, but the technique has not yet seen widespread implementation in routine protocols. During the course, the basic principle of dual energy and some new trend of spectral imaging will be introduced both technologically and clinically. To compare image quality and radiation dose of single-energy CT and dual energy, it is very important to quantify the patient risk with the introduction of these new technologies. Quantitative evaluation studies (retrospective and prospective) will be more and more important. During the refresh-course, the basic principle of patient dose in spectral imaging will be presented and attention is paid to the quantitative method of image analysis.
1. To learn about the underlying physics and today's technology.
2. To see potential advantages compared to single-energy CT.
3. To appreciate the rationale behind clinical applications.
Dual energy CT (DECT) refers to the use of two CT beams of different photon energy spectrum to collect two separate sets of projection data and provide two corresponding image datasets of the same anatomical body region to exploit spectral information regarding attenuation ability of tissues for diagnostic purposes. Despite conceived during ‘70s soon after the first clinical CT, the clinical endorsement and widespread application of DECT was initiated with the advent of dual-source CT systems in 2006. Providing the potential to improve CT image quality through artifact suppression and extracting valuable information regarding tissue composition and function, DECT is the new exciting field for the radiology community and the main driving force for CT technology evolution over the last decade. Currently, all CT vendors put considerable efforts in developing CT systems capable of performing DECT studies, while novel clinical applications of DECT are continuously introduced. However, comprehension of the basic physics of DECT and familiarisation with the advanced technological features of modern DECT scanners is prerequisite to fully exploit the advantages of DECT imaging.
1. To learn about the underlying physics and technological solutions.
2. To understand the potential advantages compared to dual-energy CT.
3. To appreciate how mature today's photon counting technology is.
Recent years' advances in room-temperature semi-conductors, especially CZT and CdTe, have enabled the transformation from energy-integrated (EI) detectors to photon-counting (PC) detectors in diagnostic CT, enhancing significantly its clinical benefits. The higher signal per x-ray photon (X10) and the short rise time of ~10 nanoseconds enable spectral analysis of each counted photon, use of adjustable multi-energy bins, K-edge imaging, and increased CNR through different energy weightings, while reducing the dose significantly. The continuous sensitivity of a pixelated sensor and the elimination of electronic noise through a threshold above it enable using much smaller detection pixels than in a conventional EI CT and contribute to further lowering of the dose. Consequently, spatial resolution is improved compared to EI CT (> 20 lp/cm). Reduction of the detection pixel size is essential also for lowering photon rates per pixel to avoid pile-up effects. However, charge sharing and Kα escapes of Te and Cd cause severe distortions to the recorded x-ray spectrum. A forward model of the detector response is used to address it and restore spectral capability, using a projection domain material decomposition. It will be shown that this can be accomplished as long as the peak-to-tail ratio is not too large, namely, detection pixel of about 0.5 mm. HW and SW methods of pile-up corrections will be shown too. Phantom and pre-clinical verifications on the PHILIPS Spectral Photon-Counting CT (SPCCT) in Lyon demonstrate the capability of such a system achieving spectral results superior to dual-energy CT, and the advantage of dual-contrast injection in a single scan.
1. To learn about medical applications and potential benefits.
2. To understand which single-energy applications could be replaced by dual-energy applications, and why.
3. To learn which additional multi-energy CT applications could be developed.
During the last decade, dual-energy CT has gained increasing attention in clinical routine due to improved diagnostic performance from the quantitative analysis of different tissue composition. Various clinical indications for a dual-energy CT scan will be reviewed with a focus on the added value. Potential future opportunities of dual-energy CT, which still are viewed as research tools, will be also discussed.