CT Reconstruction Techniques Research Articles

Blind CT Image Quality Assessment Using DDPM-Derived Content and Transformer-Based Evaluator.

Lowering radiation dose per view and utilizing sparse views per scan are two common CT scan modes, albeit often leading to distorted images characterized by noise and streak artifacts. Blind image quality assessment (BIQA) strives to evaluate perceptual quality in alignment with what radiologists perceive, which plays an important role in advancing low-dose CT reconstruction techniques. An intriguing direction involves developing BIQA methods that mimic the operational characteristic of the human visual system (HVS). The internal generative mechanism (IGM) theory reveals that the HVS actively deduces primary content to enhance comprehension. In this study, we introduce an innovative BIQA metric that emulates the active inference process of IGM. Initially, an active inference module, implemented as a denoising diffusion probabilistic model (DDPM), is constructed to anticipate the primary content. Then, the dissimilarity map is derived by assessing the interrelation between the distorted image and its primary content. Subsequently, the distorted image and dissimilarity map are combined into a multi-channel image, which is inputted into a transformer-based image quality evaluator. By leveraging the DDPM-derived primary content, our approach achieves competitive performance on a low-dose CT dataset.

Utility of follow-up ultra-high-resolution CT angiography with model-based iterative reconstruction after flow diverter treatment for cerebral aneurysms.

Follow-up examinations after flow diverter (FD) treatment for cerebral aneurysms typically involve magnetic resonance imaging (MRI) or digital subtraction angiography (DSA). However, MRI is prone to vascular defects due to metal artifacts from FD, and DSA carries a risk of ischemic complications. In the context of computed tomography angiography (CTA), this study compares the efficacy of ultra-high-resolution CT (UHRCT) and novel reconstruction techniques, such as model-based iterative reconstruction (MBIR), against conventional methods such as filtered back projection (FBP) and hybrid iterative reconstruction (IR), to determine if they are a viable alternative to DSA in clinical settings. A phantom study was conducted with the full-width half-maximum considered as the FD thickness. This study compared three reconstruction methods: MBIR, FBP, and hybrid IR. A clinical study was also conducted with 21 patients who underwent follow-up CTA after FD treatment. The FD's visibility was assessed using a 4-point scale in FBP, hybrid IR, and MBIR compared to cone-beam CT (CBCT) with angiographic systems. In the phantom study, FBP, hybrid IR, and MBIR visualized thinner FD thicknesses and improved detail rendering in that order. MBIR proved to be significantly superior in both the phantom and clinical study. UHRCT with MBIR is highly effective for follow-up evaluations after FD treatment and may become the first-choice modality in the future.

Artificial Intelligence-Based Image Reconstruction for Computed Tomography: A Survey

Computed tomography has made significant advances since its introduction in the early 1970s, where researchers have mainly focused on the quality of image reconstruction in the early stage. However, radiation exposure poses a health risk, prompting the demand of the lowest possible dose when carrying out CT examinations. To acquire high-quality reconstruction images with low dose radiation, CT reconstruction techniques have evolved from conventional reconstruction such as analytical and iterative reconstruction, to reconstruction methods based on artificial intelligence (AI). All these efforts are devoted to constructing high-quality images using only low doses with fast reconstruction speed. In particular, conventional reconstruction methods usually optimize one aspect, while AI-based reconstruction has finally managed to attain all goals in one shot. However, there are limitations such as the requirements on large datasets, unstable performance, and weak generalizability in AI-based reconstruction methods. This work presents the review and discussion on the classification, the commercial use, the advantages, and the limitations of AI-based image reconstruction methods in CT.

4D printed orbital stent for the treatment of enophthalmic invagination

Currently, the implants used for enophthalmic invagination have the disadvantages of precise filling difficulty, weak filling ability, large surgical wounds, and lack of CT development. Here, a CT-developable orbital stent was manufactured via 4D printing of a shape memory polyurethane composite for enophthalmos treatment. The composite was endowed with good CT development properties via incorporation of gold nanoparticles and nano-hydroxyapatite. Based on the bionic idea and CT reconstruction technique, a 4D printed orbital stent with a bionic honeycomb pore structure and an outer contour matching the orbital coloboma was designed to support the orbital tissue more accurately and stably. CT images of rabbits before and after the 4D printed orbital stent implantation showed better volume-filling capacity compared with the two types of the commercial orbital implants. The three-month follow-up showed the good postoperative result, which demonstrated the excellent performance of the composite in the precise minimally invasive treatment of enophthalmos compared with traditional orbital implants.

Systematic assessment of coronary calcium detectability and quantification on four generations of CT reconstruction techniques: a patient and phantom study

In computed tomography, coronary artery calcium (CAC) scores are influenced by image reconstruction. The effect of a newly introduced deep learning-based reconstruction (DLR) on CAC scoring in relation to other algorithms is unknown. The aim of this study was to evaluate the effect of four generations of image reconstruction techniques (filtered back projection (FBP), hybrid iterative reconstruction (HIR), model-based iterative reconstruction (MBIR), and DLR) on CAC detectability, quantification, and risk classification. First, CAC detectability was assessed with a dedicated static phantom containing 100 small calcifications varying in size and density. Second, CAC quantification was assessed with a dynamic coronary phantom with velocities equivalent to heart rates of 60–75 bpm. Both phantoms were scanned and reconstructed with four techniques. Last, scans of fifty patients were included and the Agatston calcium score was calculated for all four reconstruction techniques. FBP was used as a reference. In the phantom studies, all reconstruction techniques resulted in less detected small calcifications, up to 22%. No clinically relevant quantification changes occurred with different reconstruction techniques (less than 10%). In the patient study, the cardiovascular risk classification resulted, for all reconstruction techniques, in excellent agreement with the reference (κ = 0.96–0.97). However, MBIR resulted in significantly higher Agatston scores (61 (5.5–435.0) vs. 81.5 (9.25–435.0); p < 0.001) and 6% reclassification rate. In conclusion, HIR and DLR reconstructed scans resulted in similar Agatston scores with excellent agreement and low-risk reclassification rate compared with routine reconstructed scans (FBP). However, caution should be taken with low Agatston scores, as based on phantom study, detectability of small calcifications varies with the used reconstruction algorithm, especially with MBIR and DLR.

Pulmonary emphysema quantification at low dose chest CT using Deep Learning image reconstruction

PurposeQuantitative analysis of emphysema volume is affected by the radiation dose and the CT reconstruction technique. We aim to evaluate the influence of a commercially available deep learning image reconstruction algorithm (DLIR) on the quantification of pulmonary emphysema in low-dose chest CT. MethodsWe performed a retrospective study of low dose chest CT scans in 54 patients with chronic obstructive pulmonary disease (COPD). Raw data were reconstructed using FBP, iterative reconstruction (ASIR-V 70%) and deep learning based algorithms at high, medium and low-strength (DLIR -H, -M, -L). Filtered FBP images served as reference. Pulmonary emphysema volume (proportion of voxels below −950 UH) was measured on each reconstruction dataset and visually assessed by a chest radiologist. Quantitative image quality was assessed by placing 3 regions of interest in the trachea, in air and in a paraspinal muscle. Signal to noise ratio was also measured. ResultsThe mean CDTIvol was 2.38 ± 0.68 mGy. Significant differences in emphysema volumes between the filtered FBP reference and ASIR-V, DLIR-H, DLIR-M or DLIR-L were observed, (p < 10−3) for all. A strong correlation between filtered FBP volumes and DLIR-H was reported (r = 0.999, p < 10−4), a 10% overestimation with DLIR-H being observed. Noise was significantly reduced in DLIR-H volumes compared to the other reconstruction methods. Signal to noise ratio was improved when using DLIR-H (p < 10−6). ConclusionThere are significant differences regarding emphysema volumes between FBP, iterative reconstruction or deep learning-based DLIR algorithm. DLIR-H shows the closest correlation to filtered FBP while increasing SNR.

Impact of multidetector computed tomography scan parameters, novel reconstruction settings, and lung nodule characteristics on nodule diameter measurements: A phantom study.

Novel CT reconstruction techniques strive to maintain image quality and processing efficiency. The purpose of this study is to investigate the impact of a newer hybrid iterative reconstruction technique, Adaptive Statistical Iterative Reconstruction-V (ASIR-V), in combination with various CT scan parameters on the semi-automated quantification using various lung nodules. A chest phantom embedded with eight spherical objects was scanned using varying CT parameters such as tube current and ASIR-V levels. We calculated absolute percentage error (APE) and mean APE (MAPE) using differences between the semi-automated measured diameters and known dimensions. Predictive variables were assessed using a multivariable general linear model. The linear regression slope coefficients (β) were reported to demonstrate effect size and directionality. The APE of the semi-automated measured diameters was higher in ground-glass than solid nodules (β=9.000, p<0.001). APE had an inverse relationship with nodule diameter (mm; β=-3.499, p<0.001) and tube current (mA; β=-0.006, p<0.001). MAPE did not vary based on the ASIR-V level (range: 5.7%-13.1%). Error is dominated by nodule characteristics with a small effect of tube current. Regardless of phantom size, nodule size accuracy is not affected by tube voltage or ASIR-V level, maintaining accuracy while maximizing radiation dose reduction.

Fracture patterns in midshaft clavicle fractures

Current classifications of midshaft clavicle fractures are based on radiography. The aim of the study was to evaluate the fracture pattern of clavicle fractures using 3-dimensional computed tomography (3D CT). A retrospective analysis was performed on CT scans of 65 acute clavicle fractures. Using quantitative 3D CT reconstruction techniques, the fracture of the clavicle was virtually reduced. Based on these reconstructions, a group-based fracture heat map and small fragment heat map, and the location of the most common fracture line were determined. Also, the direction and amount of displacement were evaluated. Three fracture patterns could be distinguished. The primary fracture line in type 1 is going from posteromedial to anterolateral and located between 50% and 68% of the clavicle's length. In type 2, a transverse fracture line is located around 55%, and in type 3, a superolateral to inferomedial line is located between 47% and 56%. Wedged fracture fragments can be seen in types 1 and 2 and are mainly situated inferiorly. The displacement is similar in all types, but the main direction of displacement is specific for the different types (posterior, anterior, inferior). We can conclude that several fracture patterns can be seen in clavicle fractures. Most fractures are located laterally at the midshaft of the clavicle. Wedged segments are mainly located inferiorly, and at the posterior part of the clavicle, no comminution is ever seen. The direction of displacement depends on the fracture pattern.

Application of CT Image Based on Three-Dimensional Image Segmentation Algorithm in Diagnosis of Osteoarthritis

Objective: To investigate the application of multi-slice spiral CT in degenerative changes of lumbar facet joints using the LOG algorithm. Methods: The CT findings of 100 cases of degenerative vertebral facet joint disease were reviewed and analyzed in this paper. Results: The main CT manifestations of facet disease are osteophyte formation, articular hyperplasia and hypertrophy, osteosclerosis, narrowing of joint space, articular surface destruction, joint capsule calcification, joint gas accumulation, joint subluxation, and lateral recesses and vertebrae. Signs such as narrow mesopores. Conclusion: The multi-slice spiral CT (MSCT) and multi-planar reconstruction (MPR) techniques are analyzed by the LOG operator algorithm. It is found that the two techniques can fully display the anatomical structure and pathological changes of the vertebral facet joints, and are useful for the diagnosis of facet joint disease. Provide enough imaging evidence.

Artificial intelligence in image reconstruction: The change is here.

Innovations in CT have been impressive among imaging and medical technologies in both the hardware and software domain. The range and speed of CT scanning improved from the introduction of multidetector-row CT scanners with wide-array detectors and faster gantry rotation speeds. To tackle concerns over rising radiation doses from its increasing use and to improve image quality, CT reconstruction techniques evolved from filtered back projection to commercial release of iterative reconstruction techniques, and recently, of deep learning (DL)-based image reconstruction. These newer reconstruction techniques enable improved or retained image quality versus filtered back projection at lower radiation doses. DL can aid in image reconstruction with training data without total reliance on the physical model of the imaging process, unique artifacts of PCD-CT due to charge sharing, K-escape, fluorescence x-ray emission, and pulse pileups can be handled in the data-driven fashion. With sufficiently reconstructed images, a well-designed network can be trained to upgrade image quality over a practical/clinical threshold or define new/killer applications. Besides, the much smaller detector pixel for PCD-CT can lead to huge computational costs with traditional model-based iterative reconstruction methods whereas deep networks can be much faster with training and validation. In this review, we present techniques, applications, uses, and limitations of deep learning-based image reconstruction methods in CT.

CT colonography with spectral filtration and advanced modeled iterative reconstruction in the third-generation dual-source CT: image quality, radiation dose and performance in clinical utility

To evaluate image quality, radiation dose and its diagnostic performance in clinical utility of CT colonography (CTC) applying spectral filtration and advanced modeled iterative reconstruction (ADMIRE) techniques in third-generation dual-source CT. A total of 125 patients for screening or diagnostic purposes underwent CTC at 120kVp standard dose (120kVp-STD) with filtered-back projection reconstruction (FBP) in supine position, then at a tin-filtered 150 kVp low dose (Sn150kVp-LD) and a tin-filtered 100 kVp ultra-low dose (Sn100kVp-ULD) with ADMIRE reconstruction in prone position. Radiation metrics were recorded. Objective and subjective image qualities were compared, and the diagnostic performance was assessed for both colonic and extracolonic findings using CTC reporting and data system (C-RADS). The effective dose was significantly lower for Sn150kVp-LD and Sn100kVp-ULD than 120kVp-STD protocol, resulting in 22.5% and 87.5% reductions (1.55±0.30 and 0.25±0.07 mSv vs. 2.00±0.52 mSv; both p<0.01), respectively. Image noise and signal-to-noise ratio were improved significantly for Sn150kVp-LD with ADMIRE compared with 120kVp-STD, both of which had similar excellent 2D and 3D subjective image quality with equivalent diagnostic performance. Sn100kVp-ULD with ADMIRE had decreased subjective image quality and significant different C-RADS extracolonic-score (E-score) compared with 120kVp-STD, however, C-RADS colonic-score (C-score) of that showed no significantly difference. Sn150kVp and Sn100kVp with ADMIRE reconstruction provide an alternative low dose CTC strategy and could be feasible in clinical screening or diagnostic scenarios.

Reproducibility of CT Radiomic Features within the Same Patient: Influence of Radiation Dose and CT Reconstruction Settings.

Background Results of recent phantom studies show that variation in CT acquisition parameters and reconstruction techniques may make radiomic features largely nonreproduceable and of limited use for prognostic clinical studies. Purpose To investigate the effect of CT radiation dose and reconstruction settings on the reproducibility of radiomic features, as well as to identify correction factors for mitigating these sources of variability. Materials and Methods This was a secondary analysis of a prospective study of metastatic liver lesions in patients who underwent staging with single-energy dual-source contrast material-enhanced staging CT between September 2011 and April 2012. Technique parameters were altered, resulting in 28 CT data sets per patient that included different dose levels, section thicknesses, kernels, and reconstruction algorithm settings. By using a training data set (n = 76), reproducible intensity, shape, and texture radiomic features (reproducibility threshold, R2 ≥ 0.95) were selected and correction factors were calculated by using a linear model to convert each radiomic feature to its estimated value in a reference technique. By using a test data set (n = 75), the reproducibility of hierarchical clustering based on 106 radiomic features measured with different CT techniques was assessed. Results Data in 78 patients (mean age, 60 years ± 10; 33 women) with 151 liver lesions were included. The percentage of radiomic features deemed reproducible for any variation of the different technical parameters was 11% (12 of 106). Of all technical parameters, reconstructed section thickness had the largest impact on the reproducibility of radiomic features (12.3% [13 of 106]) if only one technical parameter was changed while all other technical parameters were kept constant. The results of the hierarchical cluster analysis showed improved clustering reproducibility when reproducible radiomic features with dedicated correction factors were used (ρ = 0.39-0.71 vs ρ = 0.14-0.47). Conclusion Most radiomic features are highly affected by CT acquisition and reconstruction settings, to the point of being nonreproducible. Selecting reproducible radiomic features along with study-specific correction factors offers improved clustering reproducibility. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Sosna in this issue.

SP-0698 CT-based delineation: What can we gain from state-of-the-art CT image acquisition and reconstruction techniques

SP-0698 CT-based delineation: What can we gain from state-of-the-art CT image acquisition and reconstruction techniques

Dual edge apparatus and algorithm for measurement of x-ray beam spot parameters.

The shape, size, and location of the x-ray beam spot (where the electron beam strikes the target) in a linac-based radiation therapy machine are of potential clinical significance. Established techniques to measure the beam spot parameters involve specialized hardware and typically assess size and shape of the beam spot or its position, but not both. A simple apparatus and algorithm for measuring all beam spot parameters simultaneously is proposed here. The apparatus is composed of two partially transmitting edge plates mounted at different vertical positions. The mount for the apparatus slides into the accessory tray of the linac treatment head so that it rotates with the collimator, and it is imaged by the existing electronic portal imaging device (EPID) over multiple collimator angles. A software algorithm takes the acquired images and uses a parallel-beam CT reconstruction technique to compute beam spot size, shape, and position in one computation. In addition, the wobble of the collimator assembly can be estimated. The overall method was validated with both Monte Carlo simulation and with comparison to in-house spot camera measurements on a radiation therapy system. The algorithm correctly predicted the beam spot parameters used for the Monte Carlo simulation to better than 50μm accuracy in all cases. Furthermore, results from the dual edge method matched spot camera results with 30μm accuracy for beam spot size and shape, with 80μm average accuracy for beam spot position, and better than 200μm accuracy for collimator assembly wobble. We have developed a combination dual edge apparatus and image processing algorithm that, when used on a radiotherapy linac with an EPID, can accurately determine the size and shape of the electron beam spot, its position relative to collimator rotation axis, and the wobble of the collimator assembly.

Image quality with iterative reconstruction techniques in CT of the lungs—A phantom study

BackgroundIterative reconstruction techniques for reducing radiation dose and improving image quality in CT have proved to work differently for different patient sizes, dose levels, and anatomical areas. PurposeThis study aims to compare image quality in CT of the lungs between four high-end CT scanners using the recommended reconstruction techniques at different dose levels and patient sizes. Material and methodsA lung phantom and an image quality phantom were scanned with four high-end scanners at fixed dose levels. Images were reconstructed with and without iterative reconstruction. Contrast-to-noise ratio, modulation transfer function, and peak frequency of the noise power spectrum were measured. ResultsIMR1 Sharp+ and VEO improved contrast-to-noise ratio to a larger extent than the other iterative techniques, while maintaining spatial resolution. IMR1 Sharp+ also maintained noise texture. ConclusionsIMR1 Sharp+ was the only reconstruction technique in this study which increased CNR to a large extent, while maintaining all other image quality parameters measured in this study.

An Approach to the Diagnosis of Craniofacial Fibrous Dysplasia from the 2500‐Year‐Old Remains of a Skull from Ancient China

A human skull, buried about 2500 years ago in a Bronze Age cemetery at Jinggouzi, a site of an important ethnic group in ancient China, appeared to have characteristics of fibrous dysplasia. The CT images indicated a reduction in bone density and relatively homogeneous lesions. More features were revealed using CT reconstruction techniques. Lesions seen in low‐magnification images using a 3D deep‐field microscope had an irregular honeycomb‐like structure. At higher magnification, the trabeculae morphology and the gaps between the trabeculae were irregular and varied in size and shape. Paraffin‐embedded specimens stained with HE showed trabeculae with tortuous irregular arrangements varying in shape and width. The irregular trabeculae of woven bone has been described as having fibrous dysplasia. Molecular analysis of the GNAS gene indicated no mutation. This provides a non‐invasive approach for us to make more comprehensive diagnoses and to assist research into ancient human diseases.

Could new reconstruction CT techniques challenge MRI for the detection of brain metastases in the context of initial lung cancer staging?

To evaluate the diagnostic performance of brain CT images reconstructed with a model-based iterative algorithm performed at usual and reduced dose. 115 patients with histologically proven lung cancer were prospectively included over 15 months. Patients underwent two CT acquisitions at the initial staging, performed on a 256-slice MDCT, at standard (CTDIvol: 41.4 mGy) and half dose (CTDIvol: 20.7 mGy). Both image datasets were reconstructed with filtered back projection (FBP) and iterative model-based reconstruction (IMR) algorithms. Brain MRI was considered as the reference. Two blinded independent readers analysed the images. Ninety-three patients underwent all examinations. At the standard dose, eight patients presented 17 and 15 lesions on IMR and FBP CT images, respectively. At half-dose, seven patients presented 15 and 13 lesions on IMR and FBP CT images, respectively. The test could not highlight any significant difference between the standard dose IMR and the half-dose FBP techniques (p-value = 0.12). MRI showed 46 metastases on 11 patients. Specificity, negative and positive predictive values were calculated (98.9-100 %, 93.6-94.6 %, 75-100 %, respectively, for all CT techniques). No significant difference could be demonstrated between the two CT reconstruction techniques. • No significant difference between IMR100 and FBP50 was shown. • Compared to FBP, IMR increased the image quality without diagnostic impairment. • A 50 % dose reduction combined with IMR reconstructions could be achieved. • Brain MRI remains the best tool in lung cancer staging.

Design and linear statics finite element analysis of screw hole filler for titanium locking plate system

Objective To investigate the conceptual feasibility and biomechanical advantages of our self-designed screw hole filler for a lateral bamboo-raft-type titanium locking plate in a digital model of prox-imal tibial fracture using linear statics finite element analysis. Methods A nut-type screw hole filler was designed. Four different idealized finite element models of proximal tibial fracture fixed by a lateral bam-boo-raft-type anatomic locking plate were established on the basis of three-dimensional CT reconstruction and digital orthopedic techniques. The first one was assembled with the filler and stabilized fibula, the second with stabilized fibula but without the filler, the third with the filler and unstabilized fibula, and the fourth with unstabilized fibula but without the filler. Linear statics finite element analyses were conducted for the 4 models under the same 26 groups of loads. The 4 models were compared in terms of maximum relative displacement on fracture surface, average relative displacement on fracture surface, maximum Von Mises stress of internal fixation, maximum contact stress on fracture surface, maximum contact stress between plate and tibial surface, maximum contact pressure on fracture surface, and maximum contact pressure between plate and tibial sur-face. Outcomes of the analyses for the 4 models were harvested and treated with Wilcoxon Signed Ranks Test. Results There were significant differences between using filler and not using filler in maximum relative displacement on fracture surface, average relative displacement on fracture surface, maximum Von Mises stress of internal fixation and maximum contact pressure between plate and tibial surface (P 0.05). The model as-sembled with the filler and unstabilized fibula led to the greatest improvement in maximum Von Mises stress of internal fixation (P< 0.05). Conclusions Since use of nut-type screw hole filler may increase the contact pressure between plate and bone surface, reduce the maximum Von Mises stress of internal fixation, the maximum displacement of the whole model, and the relative and average displacements on fracture surface, but has insignificant effect on the contact pressure on fracture surface, it improves the biomechanical perfor-mance of internal fixation. The filler deserves further study. Key words: Tibia; Fracture fixation, internal; Finite element analysis; Screw hole filler for locking titanium plate system

A new CT reconstruction technique using adaptive deformation recovery and intensity correction (ADRIC).

Sequential same-patient CT images may involve deformation-induced and non-deformation-induced voxel intensity changes. An adaptive deformation recovery and intensity correction (ADRIC) technique was developed to improve the CT reconstruction accuracy, and to separate deformation from non-deformation-induced voxel intensity changes between sequential CT images. ADRIC views the new CT volume as a deformation of a prior high-quality CT volume, but with additional non-deformation-induced voxel intensity changes. ADRIC first applies the 2D-3D deformation technique to recover the deformation field between the prior CT volume and the new, to-be-reconstructed CT volume. Using the deformation-recovered new CT volume, ADRIC further corrects the non-deformation-induced voxel intensity changes with an updated algebraic reconstruction technique ("ART-dTV"). The resulting intensity-corrected new CT volume is subsequently fed back into the 2D-3D deformation process to further correct the residual deformation errors, which forms an iterative loop. By ADRIC, the deformation field and the non-deformation voxel intensity corrections are optimized separately and alternately to reconstruct the final CT. CT myocardial perfusion imaging scenarios were employed to evaluate the efficacy of ADRIC, using both simulated data of the extended-cardiac-torso (XCAT) digital phantom and experimentally acquired porcine data. The reconstruction accuracy of the ADRIC technique was compared to the technique using ART-dTV alone, and to the technique using 2D-3D deformation alone. The relative error metric and the universal quality index metric are calculated between the images for quantitative analysis. The relative error is defined as the square root of the sum of squared voxel intensity differences between the reconstructed volume and the "ground-truth" volume, normalized by the square root of the sum of squared "ground-truth" voxel intensities. In addition to the XCAT and porcine studies, a physical lung phantom measurement study was also conducted. Water-filled balloons with various shapes/volumes and concentrations of iodinated contrasts were put inside the phantom to simulate both deformations and non-deformation-induced intensity changes for ADRIC reconstruction. The ADRIC-solved deformations and intensity changes from limited-view projections were compared to those of the "gold-standard" volumes reconstructed from fully sampled projections. For the XCAT simulation study, the relative errors of the reconstructed CT volume by the 2D-3D deformation technique, the ART-dTV technique, and the ADRIC technique were 14.64%, 19.21%, and 11.90% respectively, by using 20 projections for reconstruction. Using 60 projections for reconstruction reduced the relative errors to 12.33%, 11.04%, and 7.92% for the three techniques, respectively. For the porcine study, the corresponding results were 13.61%, 8.78%, and 6.80% by using 20 projections; and 12.14%, 6.91%, and 5.29% by using 60 projections. The ADRIC technique also demonstrated robustness to varying projection exposure levels. For the physical phantom study, the average DICE coefficient between the initial prior balloon volume and the new "gold-standard" balloon volumes was 0.460. ADRIC reconstruction by 21 projections increased the average DICE coefficient to 0.954. The ADRIC technique outperformed both the 2D-3D deformation technique and the ART-dTV technique in reconstruction accuracy. The alternately solved deformation field and non-deformation voxel intensity corrections can benefit multiple clinical applications, including tumor tracking, radiotherapy dose accumulation, and treatment outcome analysis.

Diagnostic accuracy of MIP slice modalities for small pulmonary nodules in paediatric oncology patients revisited: What is additional from the paediatric radiologist approach?

BackgroundMaximum intensity projection (MIP) CT image reconstruction is a beneficial diagnostic tool in paediatric radiology and can help to distinguish between small pulmonary nodules and adjacent vessels or pulmonary scars. ObjectivesThe purpose of this study was to determine the optimal MIP slice thickness and reconstruction plane for pulmonary nodule detection in paediatric patients. Materials and methodsFifty-five paediatric patients with suspected nodules less than 5mm who were diagnosed with extra-pulmonary malignancy and underwent multidetector computed tomography (MDCT) of the thorax were evaluated. Multiplanar CT 5 mm MIP reconstruction (axial-coronal-sagittal), 2mm axial-coronal MIPs, and 1-mm and 5-mm axial source slices, were interpreted independently by three blinded radiologists. The axial -1mm slices were accepted as the gold standard method as the result of retrospective consensus session in order to get comparison with similar studies. The number of nodules, size and location, distance from pleura, overall time taken and confidence were recorded separately for each observer. ResultsReceiver operating characteristic (ROC) analysis showed significant advantages of MIP images over averaged images. With high significance (p<0.001), coronal 5mm MIP reconstructions were found to be most advantageous over conventional reconstruction techniques. Mean reading time was fastest in axial 5mm MIP images. ConclusionsCompared to conventional paediatric chest CT reconstruction techniques, detection of pulmonary nodules with diameters smaller than 5mm was found to be most sensitive in 5mm coronal MIP images.Diagnostic accuracy of MIP slice modalities for small pulmonary nodules in paediatric oncology patients revisited: What is additional from the paediatric radiologist approach?