Inducible displacement CT for implant loosening detection: a scoping review on methods, validation, and challenges.

The role of CT in PET/CT imaging includes acquisition techniques for diagnostic, anatomic localization, and attenuation correction purposes. Diagnostic reference levels of the volumetric CT dose index (CTDIvol) are available for dedicated CT procedures on selected body regions, but similar reference levels for whole-body CT used in PET/CT examinations are limited. This work reports CTDIvol values from sites that conduct whole-body oncologic PET/CT examinations and participated in the scanner validation program of the Society of Nuclear Medicine and Molecular Imaging Clinical Trials Network. From 2010 to 2014, a total of 154 sites submitted CT acquisition parameters used in their clinical (18)F-FDG PET/CT oncology protocols. From these parameters, the CTDIvol was estimated using the ImPACT CTDI dosimetry tables. Histograms of CTDIvol values were created for each year, and descriptive statistics, including mean, median, and 75th percentile, were reported. Repeated-measures ANOVA was performed to determine whether significant differences occurred between reporting years. A wide range of technical parameters was reported, most notably in tube current. Between 2010 and 2014, the median CTDIvol ranged from 4.9 to 6.2 mGy and the 75th percentile from 9.7 to 10.2 mGy. There was no significant change in CTDIvol between reporting years (repeated-measures ANOVA, P = 0.985). The 75th percentile CTDIvol reported in this work was 9.8 mGy averaged over all reporting years. These data provide a resource for establishing CTDIvol reference values specific to performing CT in PET/CT whole-body examinations. The wide ranges of CT acquisition parameters reported by sites suggest that CTDIvol reference levels may be beneficial for optimization of CT protocols.

To evaluate whether different scan protocols using a first-generation dual-source photon-counting CT (PCD-CT) can reduce coronary stent artifacts and improve image quality in patients with chronic coronary artery disease (CAD) and in-stent restenosis (ISR). Patients undergoing CCTA for suspected ISR or progression of CAD were consecutively enrolled between November 2021 and February 2023. Patients were scanned on a dual-source PCD-CT using standard acquisition mode with collimation of 144 × 0.4mm or ultra-high-resolution (UHR) mode with collimation of 120 × 0.2mm. Tube voltages were set at 120 or 140kV. Scans were reconstructed using a standard kernel (Bv48), with UHR scans also reconstructed using a sharper kernel (Bv56). A total of 25 patients were included in the study, of whom 80% were male, with a mean age of 68 ± 8 years (IQR 64.8-75.3). UHR mode, particularly with Bv56 kernels, provided significantly thinner vessel walls and reduced beam hardening artifacts compared to standard mode and Bv48 kernel, especially at lower tube voltages. Noise levels varied, with generally lower noise in UHR scans. UHR mode with Bv56 kernels improves artifact reduction and vessel visualization in coronary stents, offering advantages over standard CCTA protocols. These findings may enhance the clinical diagnosis of ISR, leading to better patient outcomes through improved treatment planning.

Impact of an additional inspiration CT scan on the conventional protocol of the 18F-FDG PET-CT in the detection of small pulmonary nodes

BACKGROUND. The utility of 3-T MRI for diagnosing joint disorders is established, but its performance for diagnosing abnormalities around arthroplasty implants is unclear. OBJECTIVE. The purpose of this study was to compare 1.5-T and 3-T compressed sensing slice encoding for metal artifact correction (SEMAC) MRI for diagnosing peri-prosthetic abnormalities around hip, knee, and ankle arthroplasty implants. METHODS. Forty-five participants (26 women, 19 men; mean age ± SD, 71 ± 14 years) with symptomatic lower extremity arthroplasty (hip, knee, and ankle, 15 each) prospectively underwent consecutive 1.5- and 3-T MRI examinations with intermediate-weighted (IW) and STIR compressed sensing SEMAC sequences. Using a Likert scale, three radiologists evaluated the presence or absence of periprosthetic abnormalities, including bone marrow edema-like signal, osteolysis, stress reaction/fracture, synovitis, and tendon abnormalities and collections; image quality; and visibility of anatomic structures. Statistical analysis included nonparametric comparison and interchangeability testing. RESULTS. For diagnosing periprosthetic abnormalities, 1.5-T and 3-T compressed sensing SEMAC MRI were interchangeable. Across all three joints, 3-T MRI had lower noise than 1.5-T MRI (median IW and STIR scores at 3 T vs 1.5 T, 4 and 4 [range, 2-5 and 3-5] vs 3 and 3 [range, 2-5 and 2-4]; p < .01 for both), sharper edges (median IW and STIR scores at 3 T vs 1.5 T, 4 and 4 [both ranges, 2-5] vs 3 and 3 [range, 2-4 and 2-5]; p < .02 and p < .05), and more effective metal artifact reduction (median IW and STIR scores at 3 T vs 1.5 T, 4 and 4 [range, 3-5 and 2-5] vs 4 and 4 [both ranges, 3-5]; p < .02 and p = .72). Agreement was moderate to substantial for image contrast (IW and STIR, 0.66 and 0.54 [95% CI, 0.41-0.91 and 0.29-0.80]; p = .58 and p = .16) and joint capsule visualization (IW and STIR, 0.57 and 0.70 [range, 0.32-0.81 and 0.51-0.89]; p = .16 and p = .19). The bone-implant interface was more visible at 1.5 T (median IW and STIR scores, 4 and 4 [both ranges, 2-5] at 1.5 T vs 3 and 3 [both ranges, 2-5] at 3 T; p = .08 and p = .58), but periprosthetic tissues had superior visibility at 3 T (IW and STIR, 4 and 4 [both ranges, 3-5] at 3 T vs 4 and 4 [ranges, 2-5 and 3-5] at 1.5 T; p = .07 and p = .19). CONCLUSION. Optimized 1.5-T and 3-T compressed sensing SEMAC MRI are interchangeable for diagnosing periprosthetic abnormalities, although metallic artifacts are larger at 3 T. CLINICAL IMPACT. With compressed sensing SEMAC MRI, lower extremity arthroplasty implants can be imaged at 3 T rather than 1.5 T.

This work investigates a metal artifact reduction technique that combines weighted masking of projection data corrupted by metal, improved photon-counting detector modeling, and the constrained ‘one-step’ spectral CT image reconstruction (cOSSCIR) algorithm. The cOSSCIR algorithm directly estimates the basis material maps from the photon counts data using an optimization algorithm that places constraints on the basis maps. The improved photon-counting detector spectral modeling improves the accuracy of the polyenergetic forward model, which is expected to reduce beam hardening artifacts due to metal. This study also explores weighting schemes to reduce the contribution of counts measurements corrupted by metal during reconstruction, including selective masking across energy window. Unlike two-step decomposition approaches, cOSSCIR does not require energy windows to be registered, thus enabling energy-selective masking of data corrupted by metal. Preliminary feasibility of the proposed methods was investigated through experimental photon-counting CT acquisition of a tissue specimen with metal inserts. The cOSSCIR algorithm estimated acrylic and aluminum basis maps which were combined to form a 50 keV effective monoenergetic image. The effective monoenergetic image reconstructed by cOSSCIR from all counts data demonstrated reduced streak and view aliasing artifacts compared to the reference filtered backprojection image. Weighting of the data corrupted by metal further reduced the remaining beam hardening artifacts, with weighted masking further reducing the streak artifacts.

Effect of the cone-beam CT acquisition trajectory on image quality in spine surgery: experimental cadaver study

BackgroundMAR algorithms have not been productized in interventional imaging because they are too time-consuming. Application of a beam hardening filter can mitigate metal artifacts and doesn’t increase computational burden. We evaluate the ability to reduce metal artifacts of a 0.5 mm silver (Ag) additional filter in a Multidetector Computed Tomography (MDCT) scanner during CT-guided biopsy procedures.MethodsA biopsy needle was positioned inside the lung field of an anthropomorphic phantom (Lungman, Kyoto Kagaku, Kyoto, Japan). CT acquisitions were performed with beam energies of 100 kV, 120 kV, 135 kV, and 120 kV with the Ag filter and reconstructed using a filtered back projection algorithm. For each measurement, the CTDIvol was kept constant at 1 mGy. Quantitative profiles placed in three regions of the artifact (needle, needle tip, and trajectory artifacts) were used to obtain metrics (FWHM, FWTM, width at − 100 HU, and absolute error in HU) to evaluate the blooming artifact, artifact width, change in CT number, and artifact range. An image quality analysis was carried out through image noise measurement. A one-way analysis of variance (ANOVA) test was used to find significant differences between the conventional CT beam energies and the Ag filtered 120 kV beam.ResultsThe 120 kV-Ag is shown to have the shortest range of artifacts compared to the other beam energies. For needle tip and trajectory artifacts, a significant reduction of − 53.6% (p < 0.001) and − 48.7% (p < 0.001) in the drop of the CT number was found, respectively, in comparison with the reference beam of 120 kV as well as a significant decrease of up to − 34.7% in the artifact width (width at − 100 HU, p < 0.001). Also, a significant reduction in the blooming artifact of − 14.2% (FWHM, p < 0.001) and − 53.3% (FWTM, p < 0.001) was found in the needle artifact. No significant changes (p > 0.05) in image noise between the conventional energies and the 120 kV-Ag were found.ConclusionsA 0.5 mm Ag additional MDCT filter demonstrated consistent metal artifact reduction generated by the biopsy needle. This reduction may lead to a better depiction of the target and surrounding structures while maintaining image quality.

To compare two types of CT acquisition parameters: CT scan of the facial bone and CT scan of the sinuses, for studying the ethmoidal slit and its relationship with the frontal sinus and anterior ethmoidal artery. Retrospective study of 145 scans of the sinuses and 79 of the facial bones performed between 2012 and 2016. On each scan, the visibility of the ethmoidal slits, their length, their distance from the ethmoidal artery, and their relationship with the anterior and posterior wall of the frontal sinus were studied. The ethmoidal slit was better visualized on CT scans of the facial bone (58.2%) than on those of the sinuses (43.1%) (p = 0.02). The distance between the anterior ethmoidal artery and the anterior part of the cribriform plate was 9.3mm for CT scans of the facial bone and 8.4mm for CT scans of the sinuses. The theoretical risk of damaging the glabellar soft tissue and that of damaging the meninges during a frontal sinusotomy was evaluated, respectively, at 9.6% and 26.1% for CT scans of the facial bone, and at 6.2% and 21.5% for sinus scans. CT scans of the facial bone are better than CT scans of the sinuses for identifying ethmoidal slits and their distance from the canal of the anterior ethmoidal artery. The identification of these elements is relevant for the surgeon during frontal sinus surgery and makes it possible to assess the risk of damaging the glabellar soft tissue or meninges. Performing a CT scan of the facial bone seems preferable to that of a CT scan of the sinuses in certain pathological situations, such as cerebrospinal rhinorrhea or revision surgeries of the frontal sinus.

Distinguishing granulomas from adenocarcinomas by integrating stable and discriminating radiomic features on non-contrast computed tomography scans

Purpose: To investigate the effect of all user definable CT acquisition parameters on CT numbers for materials of various electron densities, and therefore patient dosimetry. Methods &amp; Materials: CT scanners come supplied with a large number of user definable parameters whose effects on CT numbers are not well documented. An electron density phantom (Gammex RMI 467), with 16 inserts, having 13 densities ranging from 0.28–1.69 g/cm3, was scanned using: helical and axial techniques; 3 kVp settings; 6 reconstruction filter types; 8 mAs settings; 4 different slice thicknesses; and 4 different field of view diameters. In our study we have utilize phantom with 16 inserts. A total of 77 scans were acquired. Results: The most significant variation in CT numbers resulted from the change in kVp settings. CT number variation progressively increases for inserts with density of 1.00 g/cm3 and higher. Standard deviation in CT numbers for 1.69 g/cm3 insert was 8%. However, in a case when kVp held constant adjusting other acquisition parameters (filters, mAs, slice thickness, field of view, technique) resulted in a standard deviation of no more then 3% for all 13 densities. Conclusions: The kVp settings has a most significant effect on CT numbers whereas change in mAs, reconstruction filter type, slice thickness and field of view diameter result in only minor variations. The dosimetric effect for pediatric cases, typically acquired at 90kVp, will be presented.

Purpose: Early tumor volume change holds promise for detecting the biologic activity of systemic therapy in non‐small cell lung cancer. It is imperative to optimize and standardize CT imaging protocols to further investigate volumetric response. This study explored the effects of CT acquisition parameters on volume measurements using a thorax phantom and segmentation algorithm. Methods: Eight phantom nodules of known volume (small size of 520–540mm^3, nominal diameter of 1mm and large size of 4210–4320mm^3, nominal diameter of 2mm), shape (spherical, elliptical) and density (−10 and +100 HU) were scanned on a GE VCT at four doses (25, 50, 100, and 200 mAs). For each scan, six image series were reconstructed at three slice intervals of 5, 2.5 and 1.25mm, and using the lung and standard reconstruction algorithms. Each nodule's volume was measured using an in‐house segmentation algorithm. Relative difference in volume (RDiV = (Algorithm‐True)/True*100%) was calculated. Linear mixed effects models were fitted to examine the effect of dose, and the combinations of slice thickness and reconstruction algorithm. Results: Dose did not affect the RDiV after adjusting for slice thickness and reconstruction algorithm (p=0.40). The combination of 1.25mm/standard had an estimated RDiv of −0.001 which was closest to 0. Slice thickness of 1.25mm/lung and 2.5mm/standard were not statistically different from 1.25mm/standard. Estimated differences of −6.3%(p=0.002), 7.1% (p<0.001), and 7.3%(p<0.001) in RDiV were observed for 2.5mm/lung, 5mm/standard and 5mm/lung when compared to 1.25mm/standard, respectively. Conclusion: Imaging acquisition parameters of CT slice thickness and reconstruction algorithm affect the accuracy and precision of lung nodule volume measurements to various degrees while dose has almost no effect. Our findings may help determine appropriate CT imaging acquisition parameters for clinical trials and care. Validation studies using different segmentation algorithms are warranted. This work is in part supported by Dr. Binsheng Zhao's NIH R01 CA149490. No other conflict of interest.

There is currently no Pediatric Regulatory Diagnostic Reference Level (DRL) in Cameroon to standardize protocols in hospitals. France, a European country, has DRL allowing them to optimize their examination protocol. For the sake of radiation protection, we have proposed to evaluate the dose and acquisition parameters delivered to our pediatric patients to optimize the protocols used. We also compared the 75th percentile values of dose parameters by acquisition between the three hospitals to Diagnostic Reference Level (DRL) of France. In this retrospective and evaluative multicenter study, a total of 320 patients who had at least one cranial CT scan were enrolled from three medical centers. The CT acquisition parameters including tube potential (kV), tube current (mA), slice Thickness (T), spiral or sequential scanning techniques, volume CT dose index (CTDIvol), and dose length product (DLP) were analyzed. CTDIvol values in our centers were found up to 17.42%, 46.01%, 21.56% respectively for children aged 1–4 higher than values of France's DRL. For those aged 5–9, we obtained 44.58%, 43.15%, 42.21% respectively. In addition, for children aged 10–14 there are also up to 47.73%, 44.11%, 46.39% respectively higher than values of France's DRL. It is similary for DLP values. The study showed a significant dosimetric overshoot compared to the France’s DRL and prompted us to make corrections to the protocols used and to a more rigorous monitoring of the principles of radiation protection and optimization rules in pediatric computed tomography in our hospitals. Our results have led us to make changes to our protocols which are the subject of a new dosimetric evaluation. The development of DRL for improving the pediatric CT scan in our country is necessary to optimize our protocols. Our results have led us to make changes to our protocols which are the subject of a new dosimetric evaluation. It would be necessary to set up a quality control structure in Cameroon and their applications in current practice.

To identify reproducible hematoma radiomics features (RFs) for use in predicting hematoma expansion (HE) in patients with acute intracerebral hemorrhage (ICH). For test-retest analysis, three syringes with different volumes of blood collected at the same time (to mimic homogeneous hematoma) and a phantom (FT/HK 2000; Huake, Szechwan, China) containing three cylindrical inserts were scanned seven times within 6 h on the same CT scanner. Three additional syringes with mixed blood collected at different time points (to mimic heterogeneous hematoma) were tied together with the first three syringes as well as the phantom were scanned using modified CT acquisition parameters for intra CT analysis. A coefficient of variation below 10% served as the cutoff value for reproducibility. Finally, reproducible and potentially useful RFs were used to predict HE in 144 acute ICH patients, with the area under the receiver operating characteristic curves (AUC) used to evaluate their diagnostic performance. A total of 630 RFs including 18 first-order, 24 gray-level co-occurrence matrix (GLCM), 16 gray-level run length matrix (GLRLM), five neighborhood gray-tone difference matrix (NGTDM), 63 Laplacian of Gaussian (LoG), and 504 Wavelet features were evaluated. In the test-retest analysis, the percentages of reproducible RFs ranged from 42.54% (268/630) to 45.4% (286/630) for the three homogeneous hematoma samples and 79.05% (498/630) to 81.43% (513/630) for the phantom. In the intra-CT analysis, the percentages varied from 31.43% (198/630) to 42.38% (267/630) for the six hematoma samples and 48.89% (308/630) to 53.97% (340/630) for the phantom. In the in vitro experiment, 148 RFs were reproducible for all hematoma samples in both the test-retest and intra-CT analyses; however, only 80 were statistically different between homogeneous and heterogeneous hematoma samples. Finally, HE occurred in 25% (growth >6 ml, 36/144) to 31.94% (growth >3 ml or 33%, 46/144) of the patients. The AUCs in predicting HE ranged from 0.625 to 0.703. Only a few CT-based RFs from the in vitro hematoma were reproducible and can distinguish between homogeneous and heterogeneous hematomas. The use of RFs alone to predict HE in acute ICH showed only a moderate performance. Using an in vitro experiment and clinical validation, this study demonstrated for the first time that CT-based hematoma RFs can be used to predict HE in acute ICH; nonetheless, only a few RFs are reproducible and can be used for prediction.

Hip arthroplasty has become the standard treatment for end-stage hip disease, allowing pain relief and restoration of mobility in large numbers of patients; however, pain after hip arthroplasty occurs in as many as 40% of cases, and despite improved longevity, all implants eventually fail with time. Owing to the increasing numbers of hip arthroplasty procedures performed, the demographic factors, and the metal-on-metal arthroplasty systems with their associated risk for the development of adverse local tissue reactions to metal products, there is a growing demand for an accurate diagnosis of symptoms related to hip arthroplasty implants and for a way to monitor patients at risk. Magnetic resonance (MR) imaging has evolved into a powerful diagnostic tool for the evaluation of hip arthroplasty implants. Optimized conventional pulse sequences and metal artifact reduction techniques afford improved depiction of bone, implant-tissue interfaces, and periprosthetic soft tissue for the diagnosis of arthroplasty-related complications. Strategies for MR imaging of hip arthroplasty implants are presented, as well as the imaging appearances of common causes of painful and dysfunctional hip arthroplasty systems, including stress reactions and fractures; bone resorption and aseptic loosening; polyethylene wear-induced synovitis and osteolysis; adverse local tissue reactions to metal products; infection; heterotopic ossification; tendinopathy; neuropathy; and periprosthetic neoplasms. A checklist is provided for systematic evaluation of MR images of hip arthroplasty implants. MR imaging with optimized conventional pulse sequences and metal artifact reduction techniques is a comprehensive imaging modality for the evaluation of the hip after arthroplasty, contributing important information for diagnosis, prognosis, risk stratification, and surgical planning.

Radiomics features (RFs) studies have showed limitations in the reproducibility of RFs in different acquisition settings. To date, reproducibility studies using CT images mainly rely on phantoms, due to the harness of patient exposure to X-rays. The provided CadAIver dataset has the aims of evaluating how CT scanner parameters effect radiomics features on cadaveric donor. The dataset comprises 112 unique CT acquisitions of a cadaveric truck acquired on 3 different CT scanners varying KV, mA, field-of-view, and reconstruction kernel settings. Technical validation of the CadAIver dataset comprises a comprehensive univariate and multivariate GLM approach to assess stability of each RFs extracted from lumbar vertebrae. The complete dataset is publicly available to be applied for future research in the RFs field, and could foster the creation of a collaborative open CT image database to increase the sample size, the range of available scanners, and the available body districts.