This volume provides an overview of X-ray technology and the historical development of modern CT systems. The main focus of the book is a detailed derivation of reconstruction algorithms in 2D and ...modern 3D cone-beam systems. A thorough analysis of CT artifacts and a discussion of practical issues such as dose considerations give further insight into current CT systems. Although written mainly for graduate students of biomedical engineering, medical physics, medicine (radiology), mathematics, electrical engineering, and physics, practitioners in these fields will also benefit from this book.
Over the past decade, computed
tomography
(CT)
theory, techniques and applications have undergone a rapid development. Since
CT is so
practical and useful, undoubtedly CT technology will continue ...advancing biomedical and
non-biomedical applications. In this outlook article, we share our opinions on the
research and development in this field, emphasizing 12 topics we expect to be critical in
the next decade: analytic reconstruction, iterative reconstruction, local/interior reconstruction, flat-panel
based CT,
dual-source CT, multi-source CT, novel scanning modes, energy-sensitive
CT,
nano-CT, artifact reduction, modality fusion, and phase-contrast CT. We also sketch
several representative biomedical applications.
Novel photon-counting detector CT (PCD-CT) has the potential to address the limitations of previous CT systems, such as insufficient spatial resolution, limited accuracy in detecting small ...low-contrast structures, or missing routine availability of spectral information. In this review article, we explain the basic principles and potential clinical benefits of PCD-CT, with a focus on recent literature that has grown rapidly since the commercial introduction of a clinically approved PCD-CT.
Purpose
Multi‐energy computed tomography (MECT) has a great potential to enable many novel clinical applications such as simultaneous multi‐contrast imaging. The purpose of this study was to ...implement triple‐beam MECT on a traditional energy‐integrating‐detector (EID) CT platform (EID‐MECT).
Methods
This was accomplished by mounting a z‐axis split‐filter (0.05 mm Au, 0.6 mm Sn) on Tube A of a dual‐source EID CT scanner. With the two split x‐ray beams from Tube A and the third beam from Tube B, three beams with different x‐ray spectra can be simultaneously acquired. With Tube B operated at 70 or 80 kV and Tube A at 120 or 140 kV, four different triple‐beam configurations were calibrated for MECT measurements: 70/Au120/Sn120, 80/Au120/Sn120, 70/Au140/Sn140, and 80/Au140/Sn140 kV. Iodine (I), gadolinium (Gd), bismuth (Bi) samples, and their mixtures were prepared for 2 three‐material‐decomposition tasks and 1 four‐material‐decomposition task. For each task, samples were placed in a water phantom and scanned using each of the four triple‐beam configurations. For comparison, the same phantom was also scanned using three other dual‐energy CT (DECT) or MECT technologies: twin‐beam DECT (TB‐DECT), dual‐source DECT (DS‐DECT), and photon‐counting‐detector CT (PCD‐CT), all with optimal x‐ray spectrum settings and at equal volume CT dose index (CTDIvol). The phantom for four‐material decomposition (I/Gd/Bi/Water imaging) was scanned using the PCD‐CT only (140 kV with 25, 50, 75, and 90 keV). Image‐based material decomposition was performed to acquire material‐specific images, on which the mean basis material concentrations and noise levels were measured and compared across all triple‐beam configurations in EID‐MECT and various DECT/MECT systems.
Results
The optimal triple‐beam configuration was task‐dependent with 70/Au120/Sn120, 70/Au140/Sn140, and 70/Au120/Sn120 kV for I/Gd/Water, I/Bi/Water, and I/Gd/Bi/Water material decomposition tasks, respectively. At equal radiation dose level, EID‐MECT provided comparable or better quantification accuracy in material‐specific images for all three material decomposition tasks, compared to EID‐based DECT and PCD‐CT systems. In terms of noise level comparison, EID‐MECT‐derived material‐specific images showed lower noise levels than TB‐DECT and DS‐DECT, but slightly higher than that from PCD‐CT in I/Gd/Water imaging. For I/Bi/Water imaging, EID‐MECT showed a comparable noise level to DS‐DECT, and a much lower noise level than TB‐DECT and PCD‐CT in all material‐specific images. For the four‐material decomposition task involving I/Gd/Bi/Water, the bismuth‐specific image derived from EID‐MECT was slightly noisier, but both iodine‐ and gadolinium‐specific images showed much lower noise levels in comparison to PCD‐CT.
Conclusions
For the first time, an EID‐based MECT system that can simultaneously acquire three x‐ray spectra measurements was implemented on a clinical scanner, which demonstrated comparable or better imaging performance than existing DECT and MECT systems.
Adhesion is the most common cause of small bowel obstruction, accounting for about 60％ of all cases. However, among patients with strangulated small bowel obstruction and a history of laparotomy, ...there are cases in which small bowel obstruction is not caused by adhesion, but by paracecal hernia. Here, we describe a case of strangulated small bowel obstruction caused by a paracecal hernia. A 73–year–old woman who underwent total hysterectomy presented with abdominal pain and vomiting and was diagnosed as having strangulated small bowel obstruction based on the findings of abdominal CT. Initially, adhesion was suspected as the cause of the intestinal obstruction. However, intraoperative findings revealed a lateral type of paracecal hernia with small bowel obstruction. Postoperative review of CT revealed displacement of the cecum and ascending colon into the ventral and medial sides because of a closed small intestinal loop that was present behind the colon. Furthermore, our case report suggests that in cases that exhibit the abovementioned CT findings, despite a history of laparotomy, paracecal hernia rather than adhesion should be considered as the likely cause of strangulated small bowel obstruction.
Dual-energy CT of the heart current and future status Albrecht, Moritz H.; De Cecco, Carlo N.; Schoepf, U. Joseph ...
European journal of radiology,
August 2018, 2018-Aug, 2018-08-00, 20180801, Letnik:
105
Journal Article
Recenzirano
•Dual-energy cardiac CT (DECT) has transitioned from the realm of research into clinical workflows.•DECT techniques can provide improved subjective evaluations and allow quantitative imaging.•DECT ...may allow for more gentle imaging because of the potential to decrease requisite radiation and contrast material doses.•Several promising investigational techniques are outlined for future directions.
Several applications utilizing dual-energy cardiac CT (DECT) have recently transitioned from the realm of research into clinical workflows. DECT acquisition techniques and subsequent post-processing can provide improved qualitative analysis, allow quantitative imaging, and have the potential to decrease requisite radiation and contrast material doses. Additionally, several experimental DECT techniques are pending further investigation and may improve the diagnostic accuracy of cardiac CT and/or provide evaluation of emerging imaging biomarkers in the future. This review article will summarize the major applications utilizing DECT in diagnosis of cardiovascular disease, including both the clinically used and investigational techniques examined to date.
The fourth edition of Implant Restorations: A Step-by-Step Guide provides a wealth of updated and expanded coverage on detailed procedures for restoring dental implants. Focusing on the most common ...treatment scenarios, it offers concise literature reviews for each chapter abd easy-to-follow descriptions of the techniques, along with high-quality clinical photographs demonstrating each step. Comprehensive throughout, this practical guide begins with introductory information on incorporating implant restorative dentistry in clinical practice. It covers diagnosis and treatment planning and digital dentistry, and addresses advances in cone beam computerized tomography (CBCT), treatment planning software, computer generated surgical guides, rapid prototype printing and impression-less implant restorative treatments, intra-oral scanning, laser sintering, and printing/milling polymer materials. Record- keeping, patient compliance, hygiene regimes, and follow-up are also covered. * Provides an accessible step-by-step guide to commonly encountered treatment scenarios, describing procedures and techniques in an easy-to-follow, highly illustrated format * Offers new chapters on diagnosis and treatment planning and digital dentistry * Covers advances in cone beam computerized tomography (CBCT), computer generated surgical guides, intra-oral scanning, laser sintering, and more An excellent and accessible guide on a burgeoning subject in modern dental practice by one of its most experienced clinicians, Implant Restorations: A Step-by-Step Guide, Fourth Edition will appeal to prosthodontists, general dentists, implant surgeons, dental students, dental assistants, hygienists, and dental laboratory technicians.
A 78-year-old man was referred to the hospital because of abdominal pain and vomiting. Plain chest x-ray showed an elevated left hemidiaphragm with a large gastric air bubble beneath it. The CT scan ...showed a dilated fluid-filled stomach, and the gastric antrum was moving behind the body and the pyloric region was located in the superior and anterior side of the cardia. A diagnosis of mesenteroaxial gastric volvulus was made, then endoscopic reduction was attempted. As an ordinary gastroscope could not pass through the antrum, an endosope for lower digestive tract was utilized. The longer scope could reach the second portion of the duodenum, and successful reduction of the volvulus was performed. The CT scan is valid to diagnose gastric volvulus because of capability of building three-dimensional images. Endoscopic reduction utilizing a longer endoscope is a good choice for the adult-onset volvulus.
Purpose
Inverse‐geometry computed tomography (IGCT) could have great potential in medical applications and security inspections, and has been actively investigated in recent years. In this work, we ...explore a special architecture of IGCT in a stationary configuration: symmetric‐geometry computed tomography (SGCT), where the x‐ray source and detector are linearly distributed in a symmetric design. A direct filtered backprojection (FBP)‐type algorithm is developed to analytically reconstruct images from the SGCT projections.
Methods
In our proposed SGCT system, a big number of x‐ray source points equally distributed along a straight‐line trajectory will sequentially fire in an ultra‐fast manner in one side, and an equispaced detector whose total length is comparable to that of the source will continuously collect data in the opposite side, as the object to be scanned moves into the imaging plane. We firstly present the overall design of SGCT. An FBP‐type reconstruction algorithm is then derived for this unique imaging configuration. With finite length of x‐ray source and detector arrays, projection data from one segment of SGCT scan are insufficient for an exact reconstruction. As a result, in practical applications, dual‐SGCT scan whose detector segments are placed perpendicular to each other, is of particular interest and is proposed. Two segments of SGCT together can make sure that the passing rays cover at least 180 degrees for each and every point if carefully designed. In general, however, there exists a data redundancy problem for a dual‐SGCT. So a weighting strategy is developed to maximize the use of projection data collected while avoid image artifacts. In addition, we further extend the fan‐beam SGCT to cone beam and obtain a Feldkamp–Davis–Kress (FDK)‐type reconstruction algorithm. Finally, we conduct a set of experimental studies both in simulation and on a prototype SGCT system and validate our proposed methods.
Results
A simulation study using the Shepp–Logan head phantom confirms that CT images can be exactly reconstructed from dual‐SGCT scan and that our proposed weighting strategy is able to handle the data redundancy properly. Compared with the rebinning‐to‐parallel‐beam method using the forward projection of an abdominal CT dataset, our proposed method is seen to be less sensitive to data truncation. Our algorithm can achieve 10.64 lp/cm of spatial resolution at 50% modulation transfer functions point, higher than that of the rebinning method which can only reach at 9.42 lp/cm even with extremely fine interpolation. Real experiments of a cylindrical object on a prototype SGCT further prove the effectiveness and practicability of the direct FBP method proposed, with similar level of noise performance to rebinning algorithm.
Conclusions
A new concept of SGCT with linearly distributed source and detector is investigated in this work, in which spinning of sources and detectors is no longer needed during data acquisition, simplifying its system design, development, and manufacturing. A direct FBP‐type algorithm is developed for analytical reconstruction from SGCT projection data. Numerical and real experiments validate our method and show that exact CT image can be reconstructed from dual‐SGCT scan, where data redundancy problem can be solved by our proposed weighting function.
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