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Introduction: Numerous classifications have been developed to assess tibial plateau fractures (TPF). Of these, the Schatzker system is the most widely reported in the literature yet this system is limited in its characterisation of morphological fracture features underlying the fracture location. The purpose of this study was to compare 3D morphological features of TPFs across different Schatzker types. Methods: This study retrospectively analysed preoperative TPF imaging data to reconstruct 3D models of the fractures. Ninety-one fractures (29 female, 62 male) were analysed and classified using Schatzker. Fracture location across Schatzker types was compared based on division of the articular surface into six ‘zones’. Additionally, morphological characteristics of the fractures were compared based on fracture type, including; the number, volume and shape of the fragments. Results: Schatzker II, IV and VI fractures were most common, making up 41%, 16% and 20%, respectively. Type II fractures commonly involved both the lateral and central aspect of the tibial plateau, similarly, type IV fractures incorporated the lateral condyle in most cases. Considering the morphological metrics, statistically significant differences were observed between Schatzker types for the number of; total, articular, cortical and volumetrically significant (all P < 0.001) fragments along with the volume of both primary (P < 0.001) and secondary (P = 0.02) fragments. Discussion: Assessment of underlying fracture characteristics in addition to fracture location can serve to provide greater detail relating to fracture morphology, which has the potential to assist with both surgical decision making and assessment of postoperative outcomes. Incorporating this information as part of a hierarchical or multifactorial framework for classifying fractures may help distinguish subtle differences between fracture types that are classifiable using the most current systems. Refereed/Peer-reviewed

BACKGROUND: The anatomy of the posterior wall of the acetabulum is important for the hip stability. We wanted to know whether differences can be observed. MATERIAL AND METHODS: On lateral 3D pelvic CT reconstruction of the pelvis two types were identified. On axial CT-images acetabular angles were determined. RESULTS: We observed 35 type I acetabular and 61 type II acetabular. Posterior acetabular sector angle was 114° in type I and 94° in type II acetabular (p

Spectral computed tomography (CT) has a great superiority in lesion detection, tissue characterization and material decomposition. To further extend its potential clinical applications, in this work, we propose an improved tensor dictionary learning method for low-dose spectral CT reconstruction with a constraint of image gradient l0-norm, which is named as l0TDL. The l0TDL method inherits the advantages of tensor dictionary learning (TDL) by employing the similarity of spectral CT images. On the other hand, by introducing the l0-norm constraint in gradient image domain, the proposed method emphasizes the spatial sparsity to overcome the weakness of TDL on preserving edge information. The split-bregman method is employed to solve the proposed method. Both numerical simulations and real mouse studies are perform to evaluate the proposed method. The results show that the proposed l0TDL method outperforms other competing methods, such as total variation (TV) minimization, TV with low rank (TV+LR), and TDL methods.

Among many of the image reconstruction techniques; the Feldkamp-Davis-Kress (FDK) is considered the most practical algorithm that used in clinical cone-beam Computed Tomography (CT) technology. In this paper, we present a full memory-aware management optimization scheme to reconstruct high-resolution volumes for a large number of X-Ray images as projections based on an efficient GPU acceleration technique. The proposed optimization technique is a scheme for FDK acceleration, that sheds new light on 4 new strategies: (1) Overcome limited device memory by evaluating different four configurations to migrate input and output data in the CPU/GPU system, (2) Reduce data transfer time during the FDK execution by using a Unified Memory (UM) model with data prefetching feature during reconstruction for data migration between host and device, (3) Accelerate the bottleneck algorithm back-projection as a result of computation mitigation, and (4) Optimize projection data layout that led to better device memory access and overcomes memory latency problem before processing and computing on GPU. The experimental results based on the proposed method show that it took 21.17 sec and 101.76 sec to reconstruct high-resolution 1024 3 , 2048 3 - voxel volume from 1800 projection of 1024 2 and 2048 2 -pixel respectively. The performance resulted from our optimization technique considered on-the-fly reconstruction (real-time), which means it can process 85 projections per second for high-resolution volumes from a large number of projections to achieve accuracy and resolution for reconstructed volume. In the term of speedup, the proposed method can achieve 1.72 speedup to reconstruct the low-resolution volume 512 3 , 1.82 speedup for 1024 3 volume and 1.70 s p e e d u p f o r 2048 3 for highest resolution volumes over baseline implementation and optimized over previous reconstruction methods based on FDK.

Orthogonal 2D cervical vertebra (C-vertebra) X-ray images have the advantages of high imaging efficiency, low radiation risk, easy operation and low cost for rapid primary clinical diagnoses. Especially in emergency departments, this technique is known to be significantly useful in triage for trauma patients. However, the technique can only provide overlapping anatomic information from limited projection views and is unable to visually exhibit full-view anatomy and precise stereo structures without further CT examination. To promote “once is enough” for visualizing 3D anatomy & structures and reducing repetitive radiation as much as possible, we proposed X-CTRSNet for 2D X-ray images. This is the first powerful work that simultaneously and accurately enables 3D C-vertebra CT reconstruction and segmentation directly from orthogonally anteroposterior- and lateral- view 2D X-ray images. X-CTRSNet combines the reciprocally coupled SpaDRNet for reconstruction & MulSISNet for segmentation, and a RSC Learning for tasks consistency. The experiment shows that X-CTRSNet successfully reconstructs and segments the 3D C-vertebra CT from the 2D X-ray images with a PSNR of 24.58 dB, an SSIM of 0.749, and an average Dice of 80.44%. All these findings reveal the great potential of X-CTRSNet in clinical imaging and diagnosis to facilitate emergency triage by enabling precise 3D reconstruction and segmentation on 2D X-ray images.

An incomplete projection reconstruction algorithm was proposed in this study. In synchrotron radiation computed tomography (SRCT) of mechanical loading process, shielded projection due to the loading device is the main problem of high-resolution CT reconstruction. Thus, the proposed algorithm was developed based on information repairment considering the continuity of sinogram and slice. The truncated sinogram was estimated using orientation total variation minimization (TVM), which was based on the continuity of projections at adjacent angles in sinogram. Slice rectification was conducted to restrain image distortion, which was based on the continuity of matter contribution. Then, the algorithm was validated by a series of numerical reconstruction experiments. Results showed that the new algorithm could repair the lost boundary and restrain the artifacts. Quantitative comparison of evaluation parameters indicated that the new algorithm worked well when the shielded angle was less than 60° and that satisfactory results could be obtained by approximately 200 times of iteration. Finally, the new algorithm was validated using actual SRCT data and demonstrated effective improvement of reconstruction quality. Therefore, the proposed algorithm may be a suitable method for the in situ SRCT studies of mechanical loading processes.

Purpose To investigate how various generations of iterative reconstruction (IR) algorithms impact low-contrast detectability (LCD) in abdominal computed tomography (CT) for different patient effective diameters, using a quantitative task-based approach. Methods Investigations were performed using an anthropomorphic abdominal phantom with two optional additional rings to simulate varying patient effective diameters (25, 30, and 35 cm), and containing multiple spherical targets (5, 6, and 8 mm in diameter) with a 20-HU contrast difference. The phantom was scanned using routine abdominal protocols (CTDIvol, 5.9–16 mGy) on four CT systems from two manufacturers. Images were reconstructed using both filtered back-projection (FBP) and various IR algorithms: ASiR 50%, SAFIRE 3 (both statistical IRs), ASiR-V 50%, ADMIRE 3 (both partial model-based IRs), or Veo (full model-based IR). Section thickness/interval was 2/1 mm or 2.5/1.25 mm, except 0.625/0.625 mm for Veo. We assessed LCD using a channelized Hotelling observer with 10 dense differences of Gaussian channels, with the area under the receiver operating characteristic curve (AUC) as a figure of merit. Results For the smallest phantom (25-cm diameter) and smallest lesion size (5-mm diameter), AUC for FBP and the various IR algorithms did not significantly differ for any of the tested CT systems. For the largest phantom (35-cm diameter), Veo yielded the highest AUC improvement (8.5%). Statistical and partial model-based IR algorithms did not significantly improve LCD. Conclusion In abdominal CT, switching from FBP to IR algorithms offers limited possibilities for achieving significant dose reductions while ensuring a constant objective LCD.

An approach was proposed for studying the effect of interpolation function on CT reconstruction, which could be utilized in both the assessment and the optimization of interpolation function. The underlying principle was based on a direct analysis of the numerical implementation of CT reconstruction algorithm. According to the theoretical and simulated results, we observed that different interpolation function really demonstrates different performance.

Purpose It is accepted that a donor's predicted total lung capacity (pTLC) can be 75-125% of the recipient's pTLC in lung transplantation; however, ‘optimal graft size’ is not clearly defined, especially in restricted lung disease (RD) patients. These disagreements exist as it is difficult to accurately measure lung size before and after transplantation and it is also difficult to predict and evaluate the extent of re-expansion of the restricted thoracic cavity after transplantation. This study examined changes in lung volume after lung transplantation using a 3D lung volume measurement from CT scans before and after surgery under the assumption that the patient's thoracic cavity would return to the size of the patient without underlying lung disease after surgery. Methods A total of 113 patients, who underwent lung transplantation between September 2012 and April 2019 in our institute, and met the inclusion criteria were enrolled in the study. This included 88 patients who were diagnosed with RD and 25 patients who were diagnosed with non-RD. Patients were further divided into oversized and undersized groups according to the donor and recipient pTLC ratio, and a total of 4 groups were studied. Preoperative and postoperative lung volume on CT scans were measured using the synapse 3D program (Fuji film, Japan). Results RD patients showed a significant increase in total lung volume (TLV) after surgery, while non-RD patients showed a decrease in TLV. These changes showed the greatest increase in the RD group within 1 year and continuously increased up to 5 years. In the non-RD group, TLV decreased within 3 months of surgery. These changes were not related to graft size. Conclusion In lung transplant patients, the thoracic cavity re-expanded in RD patients and reduced in the non-RD patients, returning to healthy values without lung disease status in terms of TLV.

The permeability of porous rock is a crucial indicator evaluating its ability to allow liquids to pass through it. However, challenges are always encountered in measurement and prediction of permeability, including the complicated process of laboratory experiments and the refined 3D numerical reconstruction. In order to improve the efficiency and accuracy of permeability prediction, the digital twin modeling technology is proposed to generate homologous and heterogeneous digital sandstone models based on a single two-dimensional image in this paper. Comparison of the CT reconstruction with the digital twin of sandstone indicates that they are very similar in complementary solid-phase morphology of porous media, global parameters (total porosity, fractal dimension, tortuosity), and local parameters (porosity of sequence layer, pore and throat characteristics, coordination number). In addition, the permeability of CT reconstruction and ten digital twins are analyzed by using the Lattice Boltzmann Method . The results show that the permeability of digital twins is very stable and close to the CT reconstruction at three orthogonal directions. The findings in this study may provide an accurate, stable, rapid and economic method for predicting the permeability of porous media.

Low-dose computed tomography (LdCT) imaging can greatly reduce the radiation dose imposed to patient, however it leads to the low signal-to-noise ratio (SNR) measured projection data. Using conventional analytical reconstruction method (e.g., filtered back-projection method), the reconstruction results usually suffer from serious noise in LdCT. To obtain high-quality CT images, iterative reconstruction method combined with prior knowledge of the object is of great importance. In this work, both structural group sparsity and gradient prior sparsity are jointed as a novel regularization constraint in the proposed CT reconstruction model. To solve the optimization-based CT reconstruction problem, original problem was transformed into a series of sub-problems based on alternating direction method of multipliers framework. The merit of the proposed joint regularization method is that global and local sparsity are both utilized. To valid the performance of proposed reconstruction algorithm, we did simulated experiments with different noise levels and real data studies. The qualitative and quantitative analyses show that the proposed reconstruction algorithm has better performance than other iterative reconstruction algorithms. What's more, compared to the existing iterative reconstruction methods, the proposed reconstruction algorithm can well reconstructed important structure features and effectively suppress the noise and artifacts.

International audience; By providing fast scanning with low radiation doses, sparse-view (or sparse-projection) reconstruction has attracted much research attention in X-ray computerized tomography (CT) imaging. Recent contributions have demonstrated that the total variation (TV) constraint can lead to improved solution by regularizing the underdetermined ill-posed problem of sparse-view reconstruction. However, when the projection views are reduced below certain numbers, the performance of TV regularization tends to deteriorate with severe artifacts. In this paper, we explore the applicability of Gamma regularization for the sparse-view CT reconstruction. Experiments on simulated data and clinical data demonstrate that the Gamma regularization can lead to good performance in sparse-view reconstruction.

The pore structure and seepage characteristics of coal are of great significance to the study of seepage effect of coal seam water injection. Because the current methods for comprehensively characterizing the pore structure and seepage effect of coal mass are imperfect, a multi-scale and visualization method for exploring coal structure and seepage effect is proposed. Through 3D CT reconstruction, Nuclear Magnetic Resonance (NMR) T2 spectrum and Magnetic Resonance Imaging (MRI), the pore size distribution, connectivity, and seepage characteristics of 4 coal samples are explored. The results show that the pore and fissure structures larger than 47.59 μm can be obtained through 3D reconstruction and the equivalent pore diameters (Deq) of the 4 coal samples are mainly concentrated between 100 and 500 μm. Because the pore size distribution in 0–100 μm is supplemented through NMR, it is found that the pore size of each coal sample is mainly distributed between 0.01 and 0.1 μm. The 3D reconstructed pore structure is basically consistent with the water signal spectrum obtained by NMR in the water saturated state, and both methods show that samples Q-1 and Q-2 have good pore connectivity. In addition, it is indicated from the NMR seepage experiments that Q-1 and Q-2 have more seepage space made of large-scale pores and fissures, and thus better connectivity. Therefore, the seepage effect of water injection for coal mass with different structures can be reflected by combining CT and NMR methods to comprehensively characterize the pore structure at different scales, which eliminates the limitations of a single method.

Introduction When one of the anterior cruciate ligament (ACL) bundles is torn, it seems appropriate to preserve the remaining bundle to improve the vascularization and proprioception of the graft, and to reproduce the attachment sites of the torn bundle. After ACL reconstruction, the functional result is worse when the tunnels are positioned further away from the native ACL's isometric attachment points. The goal of this study was to use CT 3D reconstructions to analyse the position of the femoral tunnel following partial ACL reconstruction and to compare it to complete ACL reconstruction cases. We hypothesized that the femoral tunnel positioning was optimal during partial ACL reconstruction. Methods In this prospective single-centre study, 16 patients who underwent isolated anteromedial bundle reconstruction were evaluated during the immediate postoperative period using 3D reconstruction of CT images. During this same period, 180 patients who underwent complete ACL reconstruction in the same surgery unit served as a control group. Results In the partial ACL reconstruction group, 6 tunnels (37.5%) were in the optimal position and 10 tunnels (62.5%) were not. In the complete ACL reconstruction group, 124 femoral (68.9%) were in the optimal position and 56 (31.1%) were not ( P Discussion Femoral tunnel positioning is not always optimal in patients who undergo partial ACL reconstruction. Three-dimensional CT reconstruction is a good tool to help surgeons detect and learn from their errors. Level of evidence III (case-control study).

Background With the advent of 3D volume rendered CT scans, more information is potentially available to aid the surgeon in complex calcaneal fractures. The primary aim was to determine if there is a difference in inter-observer and intra-observer reliability of 3D CT reconstructions compared to 2D CTs of calcaneus fractures based on classification, identification of specific fracture characteristics and proposed treatment. It is hypothesized that the correlation will be greater between experienced surgeons and trainees when using 3D CT. As a secondary aim, the authors wished to investigate the surgeons’ satisfaction with 3D CT. Patients and methods There were six raters, split into 2 groups: high and low surgical experience. Both 2D and 3D scans (10 patients) were reviewed by each rater by filling out a validated questionnaire. This sitting was over a period of six months and all scans were sent separately and randomly by our research coordinator. This process was repeated after a four-week break. Results The overall evaluation and satisfaction of CT scans of calcaneal fractures was improved by the additional use of volume rendered 3D images. Inexperienced surgeons benefited more than experienced surgeons in terms of reliabilities with fracture configuration. 3D CTs were more likely to change the surgeons’ operative strategy. The consistency of deciding on the fracture classification and satisfaction was more uniform between all the raters when 3D CT was used. Conclusion Inter-observer and intra-observer reliability of 3D CT reconstructions compared to 2D CTs of calcaneus fractures was greater based on classification, identification of specific fracture characteristics and proposed treatment. Inexperienced surgeons were more consistent when interpreting the scans using 3D CTs (improved inter-observer reliability) and were always more satisfied using the 3D CTs. As there is no extra cost or radiation exposure, we propose that 3D CTs may be valuable with preoperative teaching and planning.

Foreign bodies in the pediatric population are frequently seen in the nasal, aural and oral cavities, but are much less commonly reported in the rectum. While these cases are rarely reported in the literature, 8359 rectal foreign bodies were documented in the National Electronic Injury Surveillance System in patients 0–25 years old between 2008 and 2017, with a significant up trend in reported frequency annually [1]. Rectal foreign bodies may result in grave complications such as bleeding, perforation, abscess, sepsis or death [2]. Despite its growing incidence and potentially morbid outcomes, there are few documented case reports in the existing literature and there is no established management guideline for evaluation and management of rectal foreign bodies in the pediatric population. In this case report and review of the literature, we present an unusual case of a radiolucent foreign object in the rectum of a 10 year old child, only visualized with 3D reconstruction on CT scan, and the steps taken towards its removal. Keywords: Rectal foreign body, Sharp rectal objects, Child abuse, Abdominal pain, Proctalgia, Hematochezia

Reconstruction of limited-view CT is an ill-posed inversion problem. In order to suppress the artefacts and improve the image quality, it has been proved to be a good method toincorporatesome apriori information of the sample(refers to as constraint in this paper) to the iterative process. In this paper, sample boundary is considered as a constraint and SART algorithm is chosen to test the performance of the constraint. Reconstructions from different number of projections of the famous Shepp-Logan head phantom with different levels of noise were simulated; projection data of a spark plug was acquired on the cold neutron CT platform of China Advanced Research Reactor (CARR) and the spark plug was reconstructed as well. Both the simulation and experimental results show that SART algorithm with sample boundary constraint leads to remarkable improvement of image quality and convergence speed for limited-view CT reconstruction when the noise level of projection data is less than 5%.

[EN] In the medical imaging field, iterative methods have become a hot topic of research due to their capacity to resolve the reconstruction problem from a limited number of projections. This gives a good possibility to reduce radiation exposure on patients during the data acquisition. However, due to the complexity of the data, the reconstruction process is still time consuming, especially for 3D cases, even though implemented on modern computer architecture. Time of the reconstruction and high radiation dose imposed on patients are two major drawbacks in computed tomography. With the aim to resolve them effectively, we adapted Least Square QR method with soft threshold filtering technique for few-view image reconstruction and present its numerical validation. The method is implemented using CUDA programming mode and compared to standard SART algorithm. The numerical simulations and qualitative analysis of the reconstructed images show the reliability of the presented method., This work has been supported by Universitat Politècnica de València and partially funded by ANITRAN PROMETEOII/2014/008 of the Generalitat Valenciana of Spain.

Significant economic advantage can be achieved by assessing logs at the inlet of a sawmill so that they can be optimally processed to produce the highest possible value products from the available raw material. Computed Tomography (CT) scanning is of particular interest because it can identify the locations and sizes of internal quality-controlling features such as knots, heartwood/sapwood extent, rot, cracks and holes. Conventional CT scanning is based on medical-style equipment, which needs to have very high spatial and density resolution. This need sets very high requirements on the measurement resolution and accuracy, and substantially increases equipment complexity and cost. These features make such equipment unsuited for typical sawmill applications. However, for log scanning applications, high spatial and density resolution and measurement accuracy are not needed because most targeted internal features are fairly large and have specific geometrical shapes. Based on this thought, this paper proposes a novel geometry-based CT reconstruction approach and corresponding density reconstruction algorithms. A prototype CT scanner was built and the CT reconstructions were determined by processing the measured data using the proposed density reconstruction approach. The results obtained compare well with the results computed from conventional CT reconstruction. The good comparison gives confidence in the usefulness and applicability of the proposed CT approach for industrial use in sawmills for log scanning.

In the traditional three-dimensional CT reconstruction algorithms, high-frequency characteristics are difficult to obtain, and the noise is difficult to filter. In addition to, the reconstruction purpose is of diversification, and the three-dimensional filter to extract feature is more difficult to design and implement. Based on the characteristics of three-dimensional reconstruction algorithm and the RADON transform, a 3D CT reconstruction method to directly reconstruct multi-characteristic based on EMD was proposed and derived from the theoretical possibility and feasibility. EMD algorithm could firstly be used to decompose projection image before the reconstruction, and we could combine different IMF components to achieve a variety of feature, then use three-dimensional reconstruction algorithm to directly reconstruct the characteristics. The experimental results showed that the algorithm can better highlight a variety of useful information, simplify the filter design, and is of a certain practicability.

Emphysema is characterized by lung tissue destruction and trapped gas. On computed tomographic (CT) images, this may be expressed by widespread areas with high specific gas volume (SV(g)). SV(g) is highly sensitive to very low attenuation values, which frequently occur in the CT images of patients with severe emphysema. The purpose of the present work was to study if and how different reconstruction settings and different scanners significantly influence SV(g) distribution, particularly in the very low attenuation range.Two sets of CT images taken from two different CT scanners at two different lung volumes in 10 healthy volunteers and 18 subjects with severe emphysema were analyzed. Images were reconstructed using two different settings of reconstruction parameters: (1) thin slice thickness and sharp filter and (2) thick slice thickness and smooth filter. For each set of images, average values of SV(g) and their variation (ΔSV(g)) from total lung capacity to residual volume were calculated in the whole lung.Very low attenuation values are always present in CT images when reconstructed with thin slice thickness and a sharp filter and in very large numbers in patients with severe emphysema. SV(g) values were in general significantly higher in patients with emphysema than in healthy subjects, at both total lung capacity and residual volume (P.001), and were significantly influenced by the reconstruction filter (P.001) and CT scanner (P.001). ΔSV(g) was lower in patients with emphysema than in healthy subjects (P.001) and was significantly affected by the reconstruction setting but not by the CT scanner.The disproportionate effect of low-attenuation pixels on SV(g) likely causes overestimation of the severity of emphysema and trapped gas. This can be significantly reduced, however, by using thick slices and a smooth filter for image reconstruction. ΔSV(g) is generally robust for quantifying the functional impairment of the lung in severe emphysema.

Purpose The development of 4DCT imaging allows clinicians to account for movement of both the target tumour and organs at risk, although the choice of method of image reconstruction can impact how accurately observers can contour nearby organs. Motion-compensated (MC) image reconstruction is a technique that reduces blurring compared to standard averaged reconstruction. This study aims to quantify the presence of sharper boundaries by taking the value of the image gradient at contour lines, and link this increase in tissue definition to lower inter-observer variation. Methods Eight patients with early stage non-small lung cancer were imaged with 4DCT, and these scans were reconstructed using both motion-compensated and averaged techniques. These two sets of scans were then each delineated by five clinicians, who contoured nearby organs at risk. The mean distance between observers’ contours was calculated and compared to the image gradient value at each point on the delineation. Results Drawing on results by McWilliam et al. [1] , the use of motion-compensated CT image reconstruction results in a reduction in inter-observer variation across all sites delineated. The use of MC increases definition of boundaries between organs, represented by an increase in the image gradient at the delineation boundary. This result was particularly pronounced around the trachea, where preliminary results show the use of motion-compensated reconstruction reduced delineation separation by 50%; across all patients, the heart saw very little improvement between imaging techniques. Conclusions The use of motion-compensated CT reconstruction produces images with more well-defined boundaries between tissue, and higher values of image gradient. When delineating organs at risk, the presence of large gradients is a statistically significant (p

The last years, the clinical interest in quantitative SPECT/CT imaging is increasing. Especially in the rapidly growing field of radionuclide therapy, quantitative imaging is essential to provide nuclear medicine physicians with accurate dosimetric data. As a result, manufacturers now focus on producing SPECT/CT systems that are intrinsically quantitative. SPECT quantification is more challenging than PET quantification. In fact, the correction for photon absorption is relatively straightforward to apply in PET. In addition, in SPECT, we need to consider a variety of radionuclides with different photon energies and energy windows, different collimators and the potential for drifts in performance due to the greater number of moving parts in a SPECT system. With SPECT/CT, the coregistered CT data provide accurate information on the density of the body tissues, which can be used in algorithms that correct for photons that have been Compton-scattered or attenuated within the body. State-of-the-art reconstruction techniques are based on statistical iterative methods such as the ordered-subset maximum-likelihood expectation maximization algorithm (OSEM). In this approach, the physical characteristics of the acquisition process can be completely modeled in the reconstruction. In this presentation, an overview of all factors affecting SPECT image quantification will be presented. The latest developments to achieve quantitative SPECT/CT reconstruction will be discussed, together with calibration issues to finally obtain radioactivity concentrations per unit volume (kBq/ml).

In a sequence of CT studies of the same patient, the anatomy can deform but much of the anatomical information remains consistent from one study to the next. Therefore, once an initial CT has been made, it should be possible to approximately reconstruct subsequent 3D representations of the anatomy from less than a full set of CT sinogram data. We present a scheme to do this. A parameterized deformation model is applied to the initial CT. Two or more projection radiographs are then acquired of the anatomy after it has changed shape. Corresponding synthetic radiographs are computed from the initial CT while it is iteratively deformed by the model. The model parameters are adjusted until the synthetic radiographs optimally resemble the actual projections. We show that the deformation model that yields matching real and synthetic projections accurately describes the actual deformation of the anatomy imaged in the radiographs.

Extralobar pulmonary sequestration (ELS) and congenital cystic adenomatoid malformation have been reported to coexist in several variations. This suggests a common embryologic origin. A 6-month-old boy presented with a history of recurrent pneumonias. The patient was diagnosed with a right lower lobe congenital cystic adenomatoid malformation (CCAM) and a left lower lobe ELS/CCAM. The diagnosis was made with the aid of a multidetector computed tomography (CT). Three-dimensional CT reconstruction showed the presence of a right lower lobe CCAM, a left lower ELS with an aberrant arterial supply from the celiac axis, and possible venous drainage into the right CCAM. The patient underwent a right thoracotomy. Intraoperatively, the lesions were discovered to be connected by a band of tissue. The right lower lobe CCAM and the left ELS were removed from the right chest. Histologic analysis confirmed the presence of a CCAM within the right lower lobe. The ELS had involvement of a type II CCAM within the sequestration. The connection between the right CCAM and left ELS/CCAM showed an anomalous conducting airway, anomalous vein, and anomalous artery connecting the 2 lesions. The authors present the first case of a CCAM connected to an ELS/CCAM in the contralateral hemithorax. The unique anatomic configuration of these lesions suggests a common embryologic origin of ELS and CCAM.

Chronic traumatic aneurysm of the thoracic aorta is an unusual occurrence. Previously, arteriography was performed on all patients seen in our institution with this entity to allow confirmation of the diagnosis and anatomic delineation for operation. A case of chronic traumatic aneurysm of the distal descending aorta discovered on a routine chest roentgenogram and evaluated with chest computed tomographic scanning with three-dimensional reconstruction is presented. It is our belief that not all thoracic aneurysms require arteriography, and improved methods of computed tomographic scanning allow adequate diagnosis and anatomic delineation with decreased morbidity and cost.

We had stated in this article that multiplanar reformats using thick-section source images resulted in poorly reconstructed images in other planes with “stair-step” artefacts as the sections are “stacked.” This is accentuated in the specific situation where angled reconstruction of previously reconstructed images is undertaken to correct for patient position. This occurs due to the projection of the “corner” of the stair step into the sections above and below after the images was angled. A detailed explanation with figures is provided in our paper. I agree that this is an artefact to be aware of and recommend that the thin-section source images should be inspected prior to the reformats. I hope that the reference cited helps to explain the technical reasons for the artefact and how to avoid it.

Artifacts in reconstructed image caused by the errors in projection data depend on the source of the error itself, on the data collection mode and on the reconstruction algorithm. The effect of the multiple-rotation fan-beam data collection modes and corresponding reordered parallel convolution-backprojection algorithms on reconstruction artifacts of this type is analysed.

A portable, high resolution X-ray CT (computed tomography) scanner has been developed for nondestructive measurement of the cross-section of live trees, wooden utility poles, building columns, statues, etc., in the field environment. The spatial resolution of CT reconstruction is good enough for observing the details of annual rings of trees. The scanner should be useful in plant physiology, environment assessment, safety assurance of poles, lumber milling, archaeology and dendrochronology.