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This review discusses the current state of artificial intelligence (AI) in 18F-NaF-PET/CT imaging and the potential applications to come in diagnosis, prognostication, and improvement of care in patients with bone diseases, with emphasis on the role of AI algorithms in CT bone segmentation, relying on their prevalence in medical imaging and utility in the extraction of spatial information in combined PET/CT studies.

Background Omission errors in medical imaging can lead to missed diagnosis and harm to patients. The subject has been studied in conventional imaging, but no data is available for functional imaging in general and for PET/CT in particular. In this work, we evaluated the frequency and characteristics of perceptual omission errors in the PET component of oncologic PET/CT imaging and we analyze the hazardous scenarios prone to such modality-specific errors. Materials and methods Perceptual omission errors were collected in one tertiary center PET/CT clinic during routine PET/CT reporting over a 26-month period. The omissions were detected either in reporting follow-up PET/CT studies of the same patient or during multidisciplinary meetings. Results Significant omission errors were found in 1.2 % of the 2100 reports included in the study. The most common omissions were bone metastases and focal colon uptake. We identified six PET-specific causative factors contributing to the occurrence of omissions, and we propose solutions to minimize their influence. Conclusions The data presented here can help to promote the awareness of interpreting physicians to body areas that require higher attention and to implement reading strategies for improving the accuracy of PET/CT interpretation.

Introduction Coronavirus disease 2019 (COVID‐19) has infected over 215 million individuals worldwide. Chest radiographs (CXR) and computed tomography (CT) have assisted with diagnosis and assessment of COVID‐19. Previous reports have described peripheral and lower zone predominant opacities on chest radiographs. Whilst the most common patterns on CT are bilateral, peripheral basal predominant ground glass opacities (Wong et al., Radiology, 296, 2020, E72; Karimian and Azami, Pol J Radiol, 86, 2021, e31). This study describes the imaging findings in an Australian tertiary hospital population. Methods COVID‐PCR‐positive patients who had chest imaging (CXR, CT and ventilation perfusion (V/Q) scans) from January 2020 to August 2020 were included. Distribution, location and pattern of involvement was recorded. Evaluation of the assessors was performed using Fleiss Kappa calculations for review of radiographic findings and qualitative analysis of CT findings. Results A total of 681 studies (616 CXRs, 59 CTs, 6 V/Q) from 181 patients were reviewed. The most common chest radiograph finding was bilateral lower lobe predominant diffuse opacification and most common CT pattern being ground glass opacities. Of the CT imaging, 33 were CT Pulmonary Angiograms of which five demonstrated acute pulmonary emboli. There was good inter‐rater agreement between radiologists in assessment of imaging appearances on CXR (kappa 0.29–0.73) and CT studies. Conclusion A review of imaging in an Australian tertiary hospital demonstrates similar patterns of COVID‐19 infection on chest X‐ray and CT imaging when compared to the international population.

Background. Sinonasal diseases are widespread in childhood. Radiological studies, including computer tomography, are an optimal and effective method of diagnosis. The child's body is more sensitive to radiation exposure than adults. The threshold of exposure, which may induce internal organs injury in children, requires a precise selection of the radiological method with minimal radiation dose. There is currently no unified position in the professional community on the appropriateness of the use of ultra-low-dose computed tomography in pediatrics.We reviewed the data on the appropriateness and effectiveness of paranasal low-dose computed tomography in pediatrics.Materials. 57 domestic and foreign publications, for the period from January 2001 to November 2019. In order to achieve the objective, we analyzed relevant domestic and foreign publications in scientific libraries e-LIBRARY, PubMed, Google Scholar per the keywords: “low-dose CT”, “children”, “paranasal sinus”, “pediatric”, “diagnosis”, “children”, “low-dose computed tomography”, “sinusitis”, “paranasal sinuses”.Results. The analysis of the available literature allowed summarizing the current data on pediatric paranasal disease diagnostics and the use of computed tomography, as well as to identify possible options for reducing radiation dose.Conclusions. Conducting many radiological examinations in a child leads to the risk of cancer. However, these examinations are an effective way to diagnose paranasal diseases, and a CT scan is the “gold standard”. The actual task is to develop a CT technique with reduced radiation exposure without compromising image quality. The need to review and optimize the standard protocols of radiological studies to determine the efficacy and feasibility of studies with minimal radiation exposure to children is justified.

Background Nowadays, PET/CT plays a substantial role in the diagnosis of different types of tumor by its ability to provide combined functional and anatomic imaging in the same session. The purpose of this study is to evaluate the added value of PET/CT in staging and re-staging of primary malignant bone tumors. Results Out of the studied 40 patients, 7 patients were referred for primary staging of different types of histologically proven primary malignant bone tumors, their FDG-PET/CT studies yielded additional diagnostic information in 28.6% of them. Thirty three patients were referred either for assessment of treatment response or for follow-up to detect any viable lesions; FDG-PET/CT was more sensitive and specific than CT in follow-up and assessment of treatment response with PET/CT sensitivity 94.4%, specificity 86.7%, and total accuracy 90.9% and CT sensitivity 88.2%, specificity 81.2%, and total accuracy 84.8%. Conclusions PET/CT was an accurate imaging modality in evaluation of primary malignant bone tumors regarding tumor staging, assessment of therapeutic response and detection of metastatic disease as compared to CT.

Recently, machine learning has outperformed established tools for automated segmentation in medical imaging. However, segmentation of cardiac chambers still proves challenging due to the variety of contrast agent injection protocols used in clinical practice, inducing disparities of contrast between cavities. Hence, training a generalist network requires large training datasets representative of these protocols. Furthermore, segmentation on unenhanced CT scans is further hindered by the challenge of obtaining ground truths from these images. Newly available spectral CT scanners allow innovative image reconstructions such as virtual non-contrast (VNC) imaging, mimicking non-contrasted conventional CT studies from a contrasted scan. Recent publications have demonstrated that networks can be trained using VNC to segment contrasted and unenhanced conventional CT scans to reduce annotated data requirements and the need for annotations on unenhanced scans. We propose an extensive evaluation of this statement. We undertake multiple trainings of a 3D multi-label heart segmentation network with (HU-VNC) and without (HUonly) VNC as augmentation, using decreasing training dataset sizes (114, 76, 57, 38, 29, 19 patients). At each step, both networks are tested on a multi-vendor, multi-centric dataset of 122 patients, including different protocols: pulmonary embolism (PE), chest-abdomen-pelvis (CAP), heart CT angiography (CTA) and true non-contrast scans (TNC). An in-depth comparison of resulting Dice coefficients and distance metrics is performed for the networks trained on the largest dataset. HU-VNC-trained on 57 patients significantly outperforms HUonly trained on 114 regarding CAP and TNC scans (mean Dice coefficients of 0.881/0.835 and 0.882/0.416, respectively). When trained on the largest dataset, significant improvements in all labels are noted for TNC and CAP scans (mean Dice coefficient of 0.882/0.416 and 0.891/0.835, respectively). Adding VNC images as training augmentation allows the network to perform on unenhanced scans and improves segmentations on other imaging protocols, while using a reduced training dataset.

Objectives This study sought to assess training volumes and its relationship to learning and identify potential new thresholds for determining expertise. Background Competency-based medical education (CBME) is being rapidly adopted and therefore training programs will need to adapt and identify new and novel methods of defining, measuring, and assessing clinical skills. Methods Consecutive cardiac computed tomography (CT) studies were interpreted independently by trainees and expert readers, and their interpretations (Agatston score, coronary artery disease severity, and Coronary Artery Disease Reporting and Data System) were collected. Kappa agreements were measured between trainees and experts for every 50 consecutive cases. Agreements between trainees and experts were tracked and compared with the agreement between expert readers. Results A total of 36 trainees interpreted 14,432 cardiac CT studies. Agreement between trainees and experts increased with CT case volumes, but trainees learned at different rates. Using a threshold for expertise, skill of measuring coronary calcification was achieved within 50 cases, but expertise for coronary CT angiography appeared to require a mean case volume of 750, comprising 400 abnormal cases. Conclusions Current volume-based training guidelines may be insufficient and higher case volumes may be required. We demonstrate that tracking cardiac CT learners is feasible and that CBME could be incorporated into CT training programs.

Anti-COVID-19 vaccination has created new challenges. Lymphadenopathy (LA) with increased uptake in patients undergoing PET/CT may mislead to unnecessary further evaluation. We have analyzed routinely performed PET/CT studies following Pfizer-BioNTech vaccination to familiarize with PET/CT appearances with various PET tracers and to prevent consequences of misinterpretation. Methods: 1281 PET/CT studies performed between January 01 2021 and February 15 2021 were analyzed. Information about dates and site of vaccination was collected. Visual and semi-quantitative analysis of axillary - neck LA and arm uptake was correlated with immunization data. Results: Increased uptake in unilateral axillary LA was observed in 66% vaccinated patients, in 55% vaccinated once and in 69% vaccinated twice. Intensity of uptake decreased over time. 64/315 patients (20%) had simultaneous increased activity in the posterior arm and ipsilateral axillary LA ("double sign" [DS]). Sensitivity, specificity, PPV and NPV of axillary LA and DS were 55.4%, 83.6%, 86.7%, 49.2% and 38.6%, 100%, 100% and 66.1%, respectively. No DS was observed later than 10 and 21 days after first and the second vaccinations, respectively. None of the non-vaccinated patients had arm uptake or DS. Conclusion: Anti-COVID-19 vaccination frequently causes non-specific axillary LA with increased PET tracer activity. In one fifth of our study population this was associated with increased uptake at the vaccination site, DS. DS was 100% specific with 100% PPV for p/vaccination LA hence enabling to avoid misinterpretation of PET/CT studies and further unnecessary evaluation.

Background. In the structure of malignant neoplasms, basal cell skin cancer (BCC) occupies a leading position. In the initial stages of a malignant neoplasm, the main treatments are local treatment methods, both surgical and radiation. However, in about 1.3 % of cases, BCC can become locally or metastatic in which local treatment methods are limited. With the development of targeted drugs, such as the Hedgehog pathway inhibitor, the possibilities for effective and safe treatment of this category of patients have appeared.The objective is to present the clinical case of treating a patient with BCC who is receiving systemic therapy with a Hedgehog signaling pathway inhibitor.Case report. According to the patient, a tumor in the lower eyelid of the left eye appeared in 2000, did not seek medical help. In 2011, he applied to the clinic and was diagnosed with skin cancer of the lower eyelid of the left eye T2bN0M0. The patient refused the proposed treatment. Reapplied only in June 2017 already with a locally distributed process. The case is recognized as unresectable. From June 30, 2017 to September 4, 2017, he underwent a course of a radical program of radiotherapy, with a positive effect. 07/01/2019, he relapsed with a relapse of an orbital tumor on the left. From July 16, 2019, the patient began taking the drug wismodegib 150 mg once a day. Against the background of the treatment, control CT studies on 11/24/2019 and 11/03/2020 compared with CT data from 07/09/2019 reduced the volume of the tumor by 78 and 82 %. The patient currently continues to take wismodegib.Conclusion. The clinical case demonstrates successful treatment of locally advanced basal cell skin cancer with a Hedgehog signaling pathway inhibitor.

Background A retrospective multicentric study gathered 1439 CT chest studies with suspected coronavirus disease 2019 (COVID-19) affection. Three radiologists, blinded to other results, interpreted all studies using both lexicons with documentation of applicability and preferred score in assessing every case. The purpose of the study is to assess COVID-19 standardized assessment schemes’ (CO-RADS and COVID-RADS lexicons) applicability and diagnostic efficacy. Results This study included 991 RT-PCR-confirmed CT studies. An almost perfect agreement was found in COVID-RADS among the three observers (Fleiss Kappa = 0.82), opposed by a substantial agreement in CO-RADS (Κ = 0.78). The preference records favor COVID-RADS/CO-RADS in 78.5%/12.5%, 75.5%/24.5%, and 73.4%/24.5% regarding the three radiologists’ records, respectively. The distinguishability between positive and negative RT-PCR cases was 0.92 for COVID-RADS, while it was 0.85 for CO-RADS. On the other hand, both lexicons’ performance regarding clinical diagnosis and clinical suspicion index was 0.93 for COVID-RADS and 0.94 for CO-RADS. A very high to excellent agreement between the three observers for COVID-RADS/CO-RADS preference was concluded (Fleiss Kappa = 0.80 to 0.94). These results were statistically significant (p < 0.001). Conclusion Both lexicon scores (CO-RADS and COVID-RADS) were found to be applicable in the COVID-19 structured report with the preference of COVID-RADS in more than 50% of cases. The diagnostic accuracy of COVID-RADS against RT-PCR was higher than that of CO-RADS.

For 99mTc-sestamibi parathyroid single photon emission computed tomography/computed tomography (SPECT/CT), the traditional full-arc 360° acquisition technique has been suggested but not the theoretically low tissue-attenuated anterior 180° method. We aimed to compare the diagnostic performances and target-to-background ratios of anterior 180° and 360° SPECT/CT imaging. Ninety-nine patients who underwent 99mTc-sestamibi scintigraphy and received a surgical–pathological diagnosis of parathyroid adenoma or hyperplasia were enrolled. The SPECT/CT reconstructed images with anterior 180° and full-arc 360° data were interpreted by two physicians using a scoring scale, and the lesions were semi-quantified using target-to-background ratios for both image sets. In total, 113 abnormal parathyroid lesions were identified on the SPECT/CT images. The agreements of interpretation between the two image sets and readers were very good (κ value: 0.83–1.00). The accuracies of summative interpretation for the anterior 180° and full-arc 360° SPECT/CT were 83.04% and 82.46%, respectively. The target-to-background ratios were significantly higher for the anterior 180° than the full-arc 360° images (P

Variation of visual selective attention through the day has been demonstrated in several arenas of human performance, including radiology. It is uncertain whether this variation translates to an identifiable diurnal pattern of error rates for radiology interpretation. The purpose of this study was to attempt to identify particular days of the week and times of the day when radiologists might be most prone to error. Abdomen/pelvis CT studies containing at least one major error were collected from a 10-year period from the quality assurance (QA) database at our institution. A major error was defined as a missed finding that had altered management in a way potentially detrimental to the patient. The identified studies were categorized by the day of the week and hour of the day that the study was interpreted. Study volume data over this same period was also obtained by day of the week and time of day, so to normalize the data based on case volume. Standard errors of the volume-adjusted error rates were obtained based on the binomial distribution. The null hypothesis of constant error rates over time was tested using a weighted logistic regression model with linear time as predictor. A total of 252 major errors were identified. More errors were made on Monday than on any other day of the week (n = 58). Major error rates increased through the mid to late morning (9 am to 12 pm), and then decreased progressively through the afternoon until 4 pm, when a rise in the error rate was seen. This pattern persisted when error rates were normalized by study volume within each hour. Overall tests of time-constancy of error rates by day and hour were statistically significant (both p-values

OBJECTIVE. We reviewed a retrospective series of 126 18F-fluciclovine PET/CT studies of patients with biochemically recurrent prostate cancer at low (< 1 ng/mL) and very low (< 0.3 ng/mL) prostate-specific antigen (PSA) levels. CONCLUSION. The rate of PET/CT positivity was 33% (15/46) in patients with low PSA levels and 0% (0/17) in patients with very low PSA levels. Our results suggest that 18F-fluciclovine PET/CT can be helpful for localizing recurrence in patients with PSA levels between 0.3 and 1 ng/mL and that 18F-fluciclovine PET/CT is not recommended in patients with PSA levels less than 0.3 ng/mL.

OBJECTIVE. The purpose of this study was to determine whether contrast medium volume and method of administration and baseline estimated glomerular filtration rate influence the efficacy of prophylactic hydration for prevention of acute kidney injury after contrast administration. MATERIALS AND METHODS. An online search of PubMed conducted on August 25, 2017, produced a total of 697 studies. After the reports were reviewed, nine were included in this study. The extracted data on all patients in these studies were separated into a group that received prophylactic hydration and a group that did not. The following three parameters were used for subgroup analysis: contrast medium volume, contrast administration method, and baseline estimated glomerular filtration rate. The t test was performed, and study-level odds ratios with 95% CIs and p values were calculated. Tests of heterogeneity were conducted. RESULTS. When the volume of contrast agent administered exceeded 100 mL, hydration was beneficial in the prevention of contrast-induced acute kidney injury (odds ratio, 0.546). If the volume was less than 100 mL, hydration had no efficacy in preventing contrast-induced acute kidney injury (odds ratio, 0.917). Administration route and baseline estimated glomerular filtration rate exerted no effect on the efficacy of prophylactic hydration. CONCLUSION. For patients who receive less than 100 mL of contrast medium, the prevalent practice for contrast-enhanced CT studies, prophylactic hydration may not be necessary, regardless of the estimated glomerular filtration rate or route of contrast administration. For patients undergoing procedures requiring administration of large volumes of contrast medium, however, hydration is recommended to prevent contrast-induced acute kidney injury.

Purpose To assess the impact of the Covid-19 pandemic on FDG-PET/CT work volume and to evaluate the occurrence of abnormal imaging findings suspicious or potentially diagnostic for interstitial pneumonia by Covid-19 infection in south Italy. Methods We retrospectively reviewed the number and the findings of FDG-PET/CT studies acquired between February and April 2020 during the Covid-19 pandemic at the University of Napoli Federico II. The number and the findings of FDG-PET/CT studies acquired in the corresponding period of 2019 were also assessed for direct comparison. Results The number of FDG-PET/CT studies performed during the pandemic (n = 299) and in the corresponding period of 2019 (n = 335) were comparable. The percentage of abnormal FDG-PET/CT findings, suspicious for interstitial pneumonia by Covid-19 infection, was significantly higher during the pandemic (9%) compared with that found in the corresponding period of 2019 (4%) (χ2 5.45, P = 0.02). No significant differences were observed in the distribution of Covid-19 reporting and data system (CO-RADS) classification and in the maximum standardized uptake value between the pandemic (2.6 ± 2.2) and the corresponding period of 2019 (3.2 ± 1.4). Of note, patients with abnormal imaging findings during the pandemic time had clinical data and/or laboratory tests negative for Covid-19 infection. Conclusion Despite the restrictive medical measures for the emergency, the number of FDG-PET/CT studies was unchanged during the pandemic compared with the previous year. Our findings also indicate that Covid-19 infection was contained in our series of patients from southern Italy.

We aimed to determine at what size melanoma metastases become detectable by PET/CT. We reviewed a total of 293 whole-body PET/CT studies performed on 212 patients for staging of melanoma where there was an MRI within a month of the PET/CT. MR and PET/CT were reviewed independently by separate readers. PET/CT revealed an overall incidental true-positive rate of 1% on a per-patient basis, consistent with other studies, with ‘hot’ lesions (more avid than brain parenchyma) visible at smaller sizes than ‘cold’ lesions. PET/CT can detect metastatic melanoma lesions over about 2 cm in size, with hot lesions generally visible at smaller sizes.

Purpose To compare tumor motion amplitudes measured with 2D fluoroscopic images (FI) and with an inhale/exhale CT (IECT) technique Materials and methods Tumor motion of 52 patients (39 lung patients and 13 liver patients) was obtained with both FI and IECT. For FI, tumor detection and tracking was performed by means of a software developed by the authors. Motion amplitude and, thus, internal target volume (ITV), were defined to cover the positions where the tumor spends 95% of the time. The algorithm was validated against two different respiratory motion phantoms. Motion amplitude in IECT was defined as the difference in the position of the centroid of the gross tumor volume in the image sets of both treatments. Results Important differences exist when defining ITVs with FI and IECT. Overall, differences larger than 5 mm were obtained for 49%, 31%, and 9.6% of the patients in Superior‐Inferior (SI), Anterior‐Posterior (AP), and Lateral (LAT) directions, respectively. For tumor location, larger differences were found for tumors in the liver (73.6% SI, 27.3% AP, and 6.7% in LAT had differences larger than 5 mm), while tumors in the upper lobe benefitted less using FI (differences larger than 5 mm were only present in 27.6% (SI), 36.7% (AP), and 0% (LAT) of the patients). Conclusions Use of FI with the linac built‐in CBCT system is feasible for ITV definition. Large differences between motion amplitudes detected with FI and IECT methods were found. The method presented in this work based on FI could represent an improvement in ITV definition compared to the method based on IECT due to FI permits tumor motion acquisition in a more realistic situation than IECT.

Introduction: Adequate suppression of physiologic myocardial glucose uptake is important to ensure the interpretability and diagnostic reliability of [18F]fluorodeoxyglucose (FDG) PET/CT studies performed in the context of cardiac inflammation and infection. This study describes our experience with 4 preparatory protocols used in our institution. Methods: FDG PET/CT scans were performed according to 4 preparatory protocols (716 scans total), i.e. 6-h fast (group 1), low-carbohydrate diet plus 12-h fast (group 2), low-carbohydrate diet plus 12-h fast plus intravenous heparin pre-administration (15 IU/kg) (group 3), and low-carbohydrate diet plus 12-h fast plus intravenous heparin pre-administration (50 IU/kg) (group 4). Consecutive scans were retrospectively included from time frames during which the particular protocol was used. FDG uptake in normal myocardium was scored on a scale ranging from 0 (uptake less than that in the left ventricular blood pool) to 4 (diffuse uptake greater than that in the liver). Complete suppression was defined as uptake less than or equal to the blood pool (scores 0–1). Results: Complete suppression was accomplished in 27% in group 1, 68% in group 2, 69% in group 3 and 81% in group 4. Complete suppression was significantly lower in group 1 compared with all other groups (P < 0.0001 for all comparisons) and significantly higher in group 4 compared with group 2 (P = 0.005) and group 3 (P = 0.007). Groups 2 and 3 did not differ significantly (P = 0.92). Conclusion: A total of 50 IU/kg single-dose heparin administration before FDG PET/CT in addition to a low-carbohydrate diet and prolonged fast significantly outperformed protocols with no or lower dose (15 IU/kg) heparin in completely suppressing myocardial glucose metabolism.

Background Low tube potential-high tube current computed tomography (CT) imaging allows reduction in iodine-based contrast dose and may extend the benefit of routine contrast-enhanced CT exams to patients at risk of nephrotoxicity. Purpose To determine the ability of an iodine contrast reduction algorithm to maintain diagnostic image quality for contrast-enhanced abdominal CT. Material and Methods CT exams with iodine contrast reduction were prescribed for patients at risk for renal dysfunction. The iodine contrast reduction algorithm combines weight-based contrast volume reduction with patient width-based low tube potential selection and bolus-tracking. Control exams with routine iodine dose were selected based on weight, width, and scan protocol. Three radiologists evaluated image quality and diagnostic confidence using a 4-point scale (Results Forty-six contrast reduction algorithm and control exams were compared (mean creatinine 1.6 vs. 1.2 mg/dL, P ≤ 0.0001). Thirty-nine contrast reduction patients had an eGFR 2 and 15 had single or transplanted kidney. Mean iodine contrast dose was lower in the contrast reduction group (20.9 vs. 39.4 g/mL, P < 0.0001). Diagnostic confidence was rated as acceptable in 95% (131/138) of contrast reduction and 100% of control exams (1.18–1.28 vs. 1.02–1.13, respectively; P > 0.06). Liver attenuation and contrast-to-noise ratio (CNR) were similar ( P = 0.08), but portal vein attenuation and CNR were lower with contrast-reduction (mean 176 vs. 198 HU, P = 0.02; 13 vs. 16, P = 0.0002). Conclusion This size-based contrast reduction algorithm using low kV and bolus tracking reduced iodine contrast dose by 50%, while achieving acceptable image quality in 95% of exams.

Pseudolipomas of Glisson's capsule are rare benign subcapsular liver lesions that typically affect older men. They are composed of degenerating fat that is thought to originate from a detached epiploic appendage. On Computed Tomographic (CT) imaging, pseudolipomas of Glisson's capsule are well-circumscribed and hypoattenuating compared to the hepatic parenchyma. This case report examines three consecutive CT studies in the same patient that show the pseudolipoma migrating to a hepatic subcapsular location over a period of 4.5 months. To our knowledge, this is the first documented case of a pseudolipoma migrating over time and it supports the hypothesis of a migrating epiploic appendage forming a pseudolipoma of Glisson's capsule. A comprehensive review of relevant literature and a discussion of the presented case are provided.

OBJECTIVE. This study aims to compare the diagnostic accuracy of virtual unenhanced CT images derived from dual-source dual-energy contrast-enhanced CT with that of standard unenhanced CT images for evaluation of sialolithiasis. MATERIALS AND METHODS. All dual-energy CT studies of the neck performed during the preceding 5 years were reviewed for submandibular gland calculi. Only patients who had unenhanced CT and contrast-enhanced CT performed as part of the same evaluation were included in this study. This review yielded 30 patients. Virtual unenhanced CT images were derived from the dual-energy dataset and compared with the true unenhanced CT images by two separate radiologists who assessed the total number of calculi encountered, their location, the largest dimension, and the attenuation of the calculi. The radiation burden incurred for true unenhanced CT and virtual unenhanced CT and the total radiation burden were calculated. RESULTS. Our analysis revealed that measurements of stone size showed good interobserver agreement. The mean stone size was 7.9 ± 5.9 (SD) mm on virtual unenhanced CT and 8.4 ± 5.9 mm on true unenhanced CT (range, 2.0-31.8 mm); the difference was statistically insignificant. The mean stone attenuation differed considerably (p < 0.01) between the virtual and true unenhanced CT images (494.8 ± 187.5 HU and 924.4 ± 374.9 HU, respectively), but correlated well. The mean radiation dose for a dual-phase IV contrast-enhanced CT study was 23.13 mGy (volume CT dose index). The mean dose was 10.93 mGy for the true unenhanced CT phase, thereby suggesting a 47.25% reduction in administered radiation dose when a single-phase contrast-enhanced CT study with virtual unenhanced image reconstructions is performed. CONCLUSION. Virtual unenhanced CT images derived from dual-source dual-energy CT scans of the neck provide accurate assessment of sialolithiasis akin to that provided by conventional CT protocols but at only a fraction of the radiation dosage.

PURPOSE The objective of this study was to evaluate the accuracy of using CT attenuation and SUVs to differentiate enostoses from untreated and treated osteoblastic metastases on the attenuation-correction CT component of F-FDG PET/CTs. METHODS We retrospectively reviewed F-FDG PET/CT studies of 117 patients (169 lesions), of which 65 had imaging of enostoses, and 52 had imaging showing the transition of lesions from untreated to treated osteoblastic metastases. We measured the mean CT attenuations and the SUVmax and SUVmean of each lesion. Receiver operating characteristic curve analyses were used to evaluate the accuracy of each metric in distinguishing enostoses from untreated and treated osteoblastic metastases. RESULTS For differentiating enostoses from untreated osteoblastic metastases, mean CT attenuation achieved an area under the receiver operating characteristic curve (AUC) of 90.8%, with an optimized threshold of 795 HU. SUVmax achieved an AUC of 94.9%, with an optimized threshold of 2.2. For differentiating enostoses from treated osteoblastic metastases, the AUCs for every metric decreased, with mean CT attenuation being the best at 82.7%. A joint predictive model combining both CT attenuation and SUV increased the AUC to 88.3%, and performance was significantly better than SUVmax or SUVmean alone (P = 0.029 and P = 0.049, respectively). CONCLUSIONS CT attenuation and SUV can reliably distinguish between enostoses and metastases on F-FDG PET/CT. However, the accuracy of these metrics decreases when used to differentiate enostoses from treated metastases. A joint prediction model combining CT attenuation with SUV can improve accuracy.

PET using radiolabeled prostate-specific membrane antigen (PSMA) is now being more widely adopted as a valuable tool to evaluate patients with prostate cancer (PC). Recently, 3 different criteria for interpretation of PSMA PET were published: the European Association of Nuclear Medicine (EANM) criteria, the Prostate Cancer Molecular Imaging Standardized Evaluation criteria, and the PSMA Reporting and Data System. We compared these 3 criteria in terms of interreader, intrareader, and intercriteria agreement. Methods: Data from 104 patients prospectively enrolled in research protocols at our institution were retrospectively reviewed. The cohort consisted of 2 groups: 47 patients (mean age, 64.2 y old) who underwent Glu-NH-CO-NH-Lys-(Ahx)-[68Ga(HBED-CC)] (68Ga-PSMA11) PET/MRI for initial staging of biopsy-proven intermediate- or high-risk PC, and 57 patients (mean age, 70.5 y old) who underwent 68Ga-PSMA11 PET/CT because of biochemically recurrent PC. Three nuclear medicine physicians independently evaluated all 68Ga-PSMA11 PET/MRI and PET/CT studies according to the 3 interpretation criteria. Two of them reevaluated all studies 6 mo later in the same manner and masked to the initial reading. The Gwet agreement coefficient was calculated to evaluate interreader, intrareader, and intercriteria agreement based on the following sites: local lesion (primary tumor or prostate bed after radical prostatectomy), lymph node metastases, and other metastases. Results: In the PET/MRI group, interreader, intrareader, and intercriteria agreement ranged from substantial to almost perfect for any site according to all 3 criteria. In the PET/CT group, interreader agreement ranged from substantial to almost perfect except for judgment of distant metastases based on the PSMA Reporting and Data System (Gwet agreement coefficient, 0.57; moderate agreement), in which the most frequent cause of disagreement was lung nodules. Intrareader agreement ranged from substantial to almost perfect for any site according to all 3 criteria. Intercriteria agreement for each site was also substantial to almost perfect. Conclusion: Although the 3 published criteria have good interreader and intrareader reproducibility in evaluating 68Ga-PSMA11 PET, there are some factors causing interreader disagreement. Further work is needed to address this issue.

OBJECTIVE. The objective of our study was to evaluate the clinical utility of FDG PET/CT in staging and restaging pediatric patients with yolk sac tumor (YST). MATERIALS AND METHODS. We retrospectively reviewed the data from 31 pediatric patients with pathologically confirmed YST who underwent 34 PET/CT studies for the purpose of staging or restaging. The PET/CT studies were read by two nuclear medicine doctors in consensus. Histopathology combined with clinical and imaging follow-up was taken as the reference standard. The results of PET/CT were also compared with conventional imaging and α-fetoprotein (AFP) levels when available. RESULTS. Of the total 34 studies, six were performed for initial staging and the other 28 for posttherapy evaluation. FDG PET/CT was true-positive in all six staging studies, detected only a few more metastatic foci than conventional imaging, and changed the therapeutic regimen in none of the six patients. Nevertheless, PET/CT showed high accuracy in the restaging group, with a sensitivity of 100% and specificity of 85.7%. The treatment regimen was changed in 46.4% of the patients in the restaging group according to the PET/CT study. In addition, PET/CT had higher accuracy than AFP levels in YST restaging. Overall, the per-study performance of PET/CT was a sensitivity of 100%, specificity of 85.7%, positive predictive value of 90.9%, and negative predictive value of 100%. CONCLUSION. FDG PET/CT was only slightly superior to conventional imaging in staging YST in pediatric patients. However, PET/CT of posttherapy patients with YST showed high diagnostic accuracy and had a great impact on therapeutic management.

Purpose To assess pulmonary arteriovenous malformation (PAVM) growth among patients with untreated PAVMs using imaging from long-term follow-up per hereditary hemorrhagic telangiectasia international guidelines. Materials and Methods Analysis included 88 untreated PAVMs from 21 patients (6 male;15 female; mean age at presentation 47 y; range, 12–68 y). Two CT studies with the longest interval between were evaluated (mean 8.4 y; median 8.8 y; range, 3.1–14.1 y). Measurement of feeding artery diameter and anteroposterior (AP) and mediolateral (ML) sac dimensions for each PAVM was performed separately by 2 radiologists blinded to patient and CT order. Statistical analysis was performed to determine change in size between earliest and follow-up imaging. Results Mean feeding artery diameter, AP sac dimension, and ML sac dimension were 1.4 mm (range, 0.8–3.7 mm), 4.3 mm (range, 2.1–11.1 mm), and 4.1 mm (range, 1.8–9.2 mm) on earliest imaging and 1.4 mm (range, 0.9–2.6 mm), 4.5 mm (range, 2.2–12.2 mm), and 4.3 mm (range, 2.0–9.6 mm) on follow-up. Model-based mean analysis showed no statistically significant change in dimension of any variable between earliest and follow-up imaging. Secondary analysis including age also found no statistically significant difference (feeding diameter, P = .09; AP sac dimension, P = .9; ML sac dimension, P = .1). Analysis including time between measurements found no significant relationship between change in variables and time (feeding artery diameter, P = .4; AP sac dimension, P = .3; ML sac dimension, P = .06). Conclusions Untreated PAVMs grew slowly, if at all, in a near-decade span, and any demonstrated growth was minimal. These findings challenge the current recommendation of 3- to 5-year CT follow-up.

OBJECTIVES: There is increased interest in various new quantitative uptake metrics beyond standardized uptake value (SUV) in oncology PET/CT studies. The purpose of this study is to investigate the variability and test-retest repeatability (TRT) of metabolically active tumor volume (MATV) measurements and several other new quantitative metrics in non-small cell lung cancer (NSCLC) using [18F]FDG PET/CT with different segmentation methods, user interactions, uptake intervals, and reconstruction protocols. METHODS: Ten advanced NSCLC patients received two whole-body [18F]FDG PET/CT scans at both 60 and 90 min post-injection. PET data were reconstructed with four different protocols. Eight segmentation methods were applied to delineate lesions with and without a tumor mask. MATV, maximum and mean SUV (SUVmax, SUVmean), total lesion glycolysis (TLG), and intralesional heterogeneity features were derived. Variability and repeatability were evaluated using a generalized estimating equations statistical model with Bonferroni correction for multiple comparisons. The statistical model, including interaction between uptake interval and reconstruction protocol, was applied individually to the data obtained from each segmentation method. RESULTS: Without masking, none of the segmentation methods could delineate all lesions correctly. MATV was affected by both uptake interval and reconstruction settings for most segmentation methods. Similar observations were obtained for the uptake metrics SUVmax, SUVmean, TLG, homogeneity, entropy, and zone percentage. No effect of uptake interval was observed on TRT metrics, while the reconstruction protocol affected the TRT of SUVmax. Overall, segmentation methods showing poor quantitative performance in one condition showed better performance in other (combined) conditions. For some metrics, a clear statistical interaction was found between the segmentation method and both uptake interval and reconstruction protocol. CONCLUSION: All segmentation results need to be reviewed critically. MATV and other quantitative uptake metrics, as well as their TRT, depend on segmentation method, uptake interval, and reconstruction protocol. To obtain quantitative reliable metrics, with good TRT performance, the optimal segmentation method depends on local imaging procedure, the PET/CT system and/or reconstruction protocol. Rigid harmonization of imaging procedure and PET/CT performance will be helpful in mitigating this variability.

We aimed to explore proportion, involved organisms, and serial CT features of nodular bronchiectatic (NB) Mycobacterium avium complex (MAC) pulmonary diseases that manifested as unilateral lung disease.We retrospectively identified 674 patients with NB MAC pulmonary disease (PD) who underwent serial CT studies from January 2005 through December 2012. We selected patients with unilateral lung involvement as its initial manifestation. Retrospective analyses on serial CT findings in terms of presence and extent of lung abnormalities were performed. The organism identified (M. avium vs M. intracellulare) and treatment status were reviewed. To find the factors related to progression to involve both lungs, Cox regression analysis was performed.Unilateral MAC PD on initial CT was found in 47 patients (7%). Among them, 10 (21%) showed disease progression on follow-up CT to involve both lungs (mean evolving time, 1536 days). All 10 of these cases initially involved the right lung. Of these 10 patients, eight needed antibiotic treatment because of deteriorating imaging findings (4/8, 50%) or worsening symptoms (4/8, 50%). Initial total CT score (hazard ratio [HR], 1.414; 95% CI, 1.092-1.831; p0.01) and age (HR, 1.076; 95% CI, 1.004-1.154; p0.05) were related factors for disease progression in simple Cox regression test.Unilateral lung involvement of NB MAC PD is an occasional (7%) manifestation, and disease progressed in approximately 20% of patients in our study to involve both lungs. The imaging factor most related to disease progression appears to disease extent on initial CT.

The aim of this study was to use dual energy CT technology to maintain or improve image quality in pediatric head CT while simultaneously reducing radiation dose.In this retrospective study, helical head CTs performed using a standard head CT protocol were compared to studies performed with a dual energy (DE) protocol. Objective comparison was performed by measuring regions of interest in 11 areas of the brain. Subjective rating for image quality using a Likert scale, was performed by three radiologists. Radiation doses were evaluated using CT dose index and dose length product.Signal-to-noise ratio was, for the most part, not significantly different between the DE and conventional scans. Contrast-to-noise ratio was slightly lower for children over 6 year of age utilizing the dual energy protocol versus the standard protocol. Qualitatively, there was little difference in image quality in patients6 years old, with the only significant difference in infratentorial noise. However, in patients6 years of age, infratentorial noise, sharpness and diagnostic acceptability, as well as supratentorial sharpness were all significantly improved by DE CT technique. Radiation exposure as measured by CTDI and DLP was modestly lower with the dual energy protocol in all study populations.Dual energy CT can be used clinically in pediatric patients to maintain or improve image quality while reducing radiation dose.

Background The clinical and research value of Computed Tomography (CT) volumetry of esophageal cancer tumor size remains controversial. Development in CT technique and image analysis has made CT volumetry less cumbersome and it has gained renewed attention. The aim of this study was to assess esophageal tumor volume by semi-automatic measurements as compared to manual. Methods A total of 23 esophageal cancer patients (median age 65, range 51–71), undergoing CT in the portal-venous phase for tumor staging, were retrospectively included between 2007 and 2012. One radiology resident and one consultant radiologist measured the tumor volume by semiautomatic segmentation and manual segmentation. Reproducibility of the respective measurements was assessed by intraclass correlation coefficients (ICC) and by average deviation from mean. Results Mean tumor volume was 46 ml (range 5-137 ml) using manual segmentation and 42 ml (range 3-111 ml) using semiautomatic segmentation. Semiautomatic measurement provided better inter-observer agreement than traditional manual segmentation. The ICC was significantly higher for semiautomatic segmentation in comparison to manual segmentation (0.86, 0.56, p

Objectives: To accurately determine and compare patient radiation burden from routine multi-phase CT (MPCT) and dynamic CT liver perfusion (CTLP) studies taking into account the effect of iodine uptake of exposed tissues/organs. Materials and Methods: 40 consecutive MPCT of upper abdomen and 40 consecutive CTLP studies performed on a modern CT scanner were retrospectively studied. Iodine uptake of radiosensitive tissues at the time of acquisition was calculated through the difference of tissues’ CT numbers between NECT and CECT images. Monte Carlo simulation and mathematical anthropomorphic phantoms were employed to derive patient-size-specific organ dose data from each scan involved taking into account the effect of iodinated contrast uptake on absorbed dose. Effective dose estimates were derived for routine multiphase CT and CTLP by summing up the contribution of NECT and CECT scans involved. Results: The mean underestimation error in organ doses from CECT exposures if iodine uptake is not encountered was found to be 2.2%–38.9%. The effective dose to an average-size patient from routine 3-phase CT, 4-phase CT and CTLP studies was found to be 20.6, 27.7 and 25.8 mSv, respectively. Effective dose from CTLP was found lower than 4-phase CT of upper abdomen irrespective of patient body size. Compared to 3-phase CT, the radiation burden from CTLP was found to be higher for average size-patients but again lower for overweight patients. Conclusions: Modern CT technology allows CTLP studies at comparable or even lower patient radiation burden compared to routine multi-phase liver CT imaging.

We present a pediatric case with T-cell lymphoblastic leukemia and persistent chylothorax who was referred to lymphoscintigraphy to identify the site of leakage. Planar lymphoscintigraphy with SPECT/CT revealed hot spots at the left jugulovenous angle and the confluens of the vena brachiocephalica to vena cava, which were compatible with the sites of leakage. Hybrid imaging with SPECT/CT technique have great impact on accurate detection of the defects in the lymphatic system in patients with chylothorax.

Chest and sinus CT imaging among cancer patients undergoing chemotherapy and bone marrow transplant in the setting of neutropenic fever is not uncommon, yet the utility of routine imaging surveillance remains unclear. We aim to compare the rates of acute infection detected on CT chest and CT sinus exams performed in this clinical setting.Reports of 1059 consecutive CT chest and sinus examinations for the clinical indication of neutropenic fever on 262 patients performed between January through June 2017 were retrospectively reviewed. Infection as reported was characterized as acute or worsening, improving, stable, indeterminate or negative. Results were tabulated and Pearson's chi-square test was used for comparison analysis.Absence of infection on CT sinus was significantly higher than CT chest (86.1% vs. 58.5%; P0.001). Conversely, CT chest had significantly higher incidence of acute or worsening infection than CT sinus (28.7% vs. 11.6%; P0.001). CT chest also showed significantly higher incidence of improving infection compared to CT sinus (6.2% vs. 1.1%; P0.001). There was no significant difference between incidence of stable infection on CT chest and CT sinus (1.1% vs. 0.2%; P=0.059). Infection was indeterminate in 5.5% of CT chest vs. 1% on CT sinus (P0.001).CT chest showed significantly higher diagnostic yield for acute infection than CT sinus, suggesting that sinusitis is less likely to be the source of fever than chest infections in febrile neutropenic patients. The majority of CT studies showed absence of infection, raising the question of the overall utility of routine surveillance CT imaging among this subset of patients.

Background The SwiftScan solution (General Electric Healthcare) combines a new low-energy high-resolution sensitivity collimator and a tomographic step-and-shoot continuous (SSC) mode acquisition. The purpose of this study is to determine whether SSC mode can be used in clinical practice with shorter examination times, while preserving image quality and ensuring accurate semi-quantification. Twenty bone scan and 10 lung scan studies were randomly selected over a period of 2 months. Three sets of image datasets were produced: step-and-shoot (SS) acquisition, simulated 25% count reduction using the Poisson resampling method (SimSS), and SimSS continuous acquisition (SimSSC), where SimSS was summed with counts acquired during detector head rotation. Visual assessment (5-point Likert scale, 2 readers) and semi-quantitative evaluation (50 focal uptake from 10 bone studies), assessed by SUVmean, coefficient of variation (COV), and contrast-to-noise ratio (CNR), were performed using t test and Bland-Altman analysis. Results Intra-reader agreement was substantial for reader 1 (k = 0.71) and for reader 2 (k = 0.61). Inter-reader agreement was substantial for SS set (k = 0.93) and moderate for SimSSC (k = 0.52). Bland-Altman analysis showed a good interchangeability of SS and SimSSC SUV values. The mean CNR between SS and SimSSC was not significantly different: 42.9 ± 43.7 [23.7–62.1] vs. 43.1 ± 46 [22.9–63.3] (p = 0.46), respectively. COV values, assessing noise level, did not deviate significantly between SS and SimSSC: 0.20 ± 0.08 [0.18–0.23] vs. 0.21 ± 0.08, [0.18–0.23] (p = 0.15), respectively, whereas a significant difference was demonstrated between SS and SimSS: 0.20 ± 0.08 [0.18–0.23] vs. 0.23 ± 0.09 [0.20–0.25] (p < 0.0001), respectively. Conclusions SSC mode acquisition decreases examination time by approximately 25% in bone and lung SPECT/CT studies compared to SS mode (~ 2 min per single-bed SPECT), without compromising image quality and signal quantification. This SPECT sensitivity improvement also offers the prospect of more comfortable exams, with less motion artifacts, especially in painful or dyspneic patients.

Purpose To investigate the possibility of reducing the injected activity for whole-body [18F]FDG-PET/CT studies of paediatric oncology patients and to assess the usefulness of time-of-flight (TOF) acquisition on PET image quality at reduced count levels. Procedures Twenty-nine paediatric oncology patients (12F/17M, 3–18 years old (median age 13y), weight 45±20 kg, BMI 19±4 kg/m2), who underwent routine whole-body PET/CT examinations on a Siemens Biograph mCT TrueV system with TOF capability (555ps) were included in this study. The mean injected activity was 156 ± 45 MBq (3.8 ± 0.8 kg/MBq) and scaled to patient weight. The raw data was collected in listmode (LM) format and pre-processed to simulate reduced levels of [18F]FDG activity (75, 50, 35, 20 and 10% of the original counts) by randomly removing events from the original LM data. All data were reconstructed using the vendor-specific e7-tools with standard OSEM only, with OSEM plus resolution recovery (PSF). The reconstructions were repeated with added TOF (TOF) and PSF+TOF. The benefit of TOF together with the reduced count levels was evaluated by calculating the gains in signal-to-noise ratio (SNR) in the liver and contrast-to-noise ratio (CNR) in all PET-positive lesions before and after TOF employed at every simulated reduced count level. Finally, the PSF+TOF images at 50, 75 and 100% of counts were evaluated clinically on a 5-point scale by three nuclear medicine physicians. Results The visual inspection of the reconstructed images did not reveal significant differences in image quality between 75 and 100% count levels for PSF+TOF. The improvements in SNR and CNR were the greatest for TOF reconstruction and PSF combined. Both SNR and CNR gains did increase linearly with the patients BMI for both OSEM only and PSF reconstruction. These benefits were observed until reducing the counts to 50 and 35% for SNR and CNR, respectively. Conclusions The benefit of using TOF was noticeable when using 50% or greater of the counts when evaluating the CNR and SNR. For [18F]FDG-PET/CT, whole-body paediatric imaging the injected activity can be reduced to 75% of the original dose without compromising PET image quality.

Background COVID-19 is a pandemic disease and is important to know the nature of the disease during follow-up. We aimed to study different imaging signs and changes that occurred during the initial scan, follow-up, and complications. Moreover, to study the CT severity score and its relation to the patients’ clinical condition using oxygen saturation as a parameter. This was a retrospective study conducted on 125 patients, including 293 CT studies, from March till the end of August 2020. The mean age was 47.4 ± 15.7 years and 64.8% of the patients were males. All patients proved to have COVID-19 by the RT-PCR test. The CT studies of the patients were divided into four stages according to the timing after the onset of symptoms. The incidence of different CT features, patterns, complications, CT severity score, and oxygen saturation were recorded in different stages. Results During follow-up studies, GGOs were the most constant and common CT features. Consolidation and crazy paving showed gradual progression to reach the peak at the 3rd stage. Mixed attenuation pattern was the commonest pattern at the 3rd stage while a pure GGO pattern was the commonest feature in other stages. The complications occurred mostly in the 3rd stage. Nevertheless, the CT severity score showed an inverse relation with oxygen saturation. Conclusion Radiological evaluation of COVID-19 pneumonia showed gradual progression till the peak critical stage at 8-14 days from the onset of symptoms. Consolidation and mixed attenuation pattern can be considered as CT signs of disease severity.

18F-FDG accumulates not only in malignant lesions but also in infectious and inflammatory ones. 3'-deoxy-3'-18F-fluorothymidine (FLT) has been investigated as a promising PET tracer for evaluating tumor proliferating activity. We report a case of liver abscess during therapy of pancreatic cancer that underwent FDG PET/CT and FLT PET/CT studies. Although FDG PET/CT demonstrated several regions of increased uptake in the liver, FLT PET/CT showed no increased uptake in the liver.

Background Corona Virus Disease 2019 (COVID-19) outbreak was officially announced as a global pandemic by the WHO on March 11th 2020. Thorough understanding of CT imaging features of COVID-19 is essential for effective patient management; rationalizing the need for relevant research. The aim of this study was to analyze the chest CT findings of patients with real-time polymerase chain reaction (RT-PCR) proved COVID-19 admitted to four Egyptian hospitals. The recently published RSNA expert consensus statement on reporting COVID-19 chest CT findings was taken into consideration. Results Normal CT “negative for COVID-19” was reported in 26.1% of our RT-PCR proved COVID-19 cases. In descending order of prevalence, imaging findings of the positive CT studies (73.9%) included GGO (69%), consolidation (49.7%), crazy paving (15.4%), and peri-lobular fibrosis (40.6%). These showed a dominantly bilateral (68.2%), peripheral (72.4%), and patchy (64.7%) distribution. Remarkably, thymic hyperplasia was identified in 14.3% of studies. According to the RSNA consensus, CT findings were classified as typical in 68.9%, indeterminate in 3.6%, and atypical in 1.4% of the evaluated CT studies. Conclusion Although COVID-19 cannot be entirely excluded by chest CT, it can be distinguished in more than two-thirds of cases; making CT a widely available, non-invasive, and rapid diagnostic tool.

Advances in iterative image reconstruction enable absolute quantification of SPECT/CT studies by incorporating compensations for collimator–detector response, attenuation, and scatter. This study aimed to assess the quantitative accuracy of SPECT/CT based on different levels of (99m)Tc activity (low/high) using different SUV metrics (SUV(mean), SUV(max), SUV(0.6 max), and SUV(0.75 max) [the average values that include pixels greater than 60% and 75% of the SUV(max) in the volume of interest, respectively]). Methods: A Jaszczak phantom equipped with 6 fillable spheres was set up with low and high activity ratios of 1:4 and 1:10 (background-to-sphere) on background activities of 10 and 60 kBq/mL, respectively. The fixed-size volume of interest based on the diameter of each sphere was drawn on SPECT images using various metrics for SUV quantification purposes. Results: The convergence of activity concentration was dependent on the number of iterations and application of postfiltering. For the background-to-sphere ratio of 1:10 with a low background activity concentration, the SUV(mean) metric showed an underestimation of about 38% from the actual SUV, and SUV(max) exhibited an overestimation of about 24% for the largest sphere diameter. Meanwhile, bias reductions of as much as −6% and −7% for SUV(0.6 max) and SUV(0.75 max), respectively, were observed. SUV(max) gave a more accurate reading than the others, although points that exceeded the actual value were detected. At 1:4 and 1:10 background activity of 10 kBq/mL, a low activity concentration attained a value close to the actual ratio. Use of 2 iterations and 10 subsets without postfiltering gave the most accurate values for reconstruction and the best image overall. Conclusion: SUV(max) is the best metric in a high- or low-contrast-ratio phantom with at least 2 iterations, 10 subsets, and no postfiltering.

PURPOSE: To compare the (18)F-NaF PET/CT studies ((18)F-NaF) with other imaging methods in the detection of skeletal metastases (SM) in patients with medullary thyroid cancer (MTC). METHODS: We retrospectively analyzed 31 patients with MTC who performed (18)F-NaF to assess SM. The results of the (18)F-NaF were compared with other imaging methods performed for metastasis detection: (99)Tc-MDP bone scan (BS), magnetic resonance imaging (MRI), contrast-enhanced CT (CT), and (68)Ga-Dotatate and (18)F-FDG PET/CT studies. A qualitative analysis comparing the (18)F-NaF findings with the ones of the other methods was performed, and the results were classified as superior (>), equal (=), and inferior ( BS and in 3 (18)F-NaF = BS), 1 performed (18)F-FDG ((18)F-NaF > (18)F-FDG), 4 performed (68)Ga-Dotatate (in 2 (18)F-NaF > (68)Ga-Dotatate and in 2 (18)F-NaF = (68)Ga-Dotatate), 20 performed CT of at least one body segment (in 15 (18)F-NaF = CT and in 5 (18)F-NaF > CT), and 16 performed MRI of at least one body segment, and in all of them, the (18)F-NaF was equal to the MRI. Beside this, the (18)F-NaF detected SM in body segments not routinely scanned in MRI and CT. CONCLUSION: In patients with MTC, the (18)F-NaF seems to be equal or superior to other imaging modalities in the detection of SM and allows the analysis of the whole skeletal in a single study.

Even though teeth are often included in the field of view for a variety of medical CT studies, dental pathology is often missed by radiologists. Given the myriad morbidity and occasional mortality associated with sequelae of dental pathology, an important goal is to decrease these false negatives. However, given the ever-increasing volume of cases studies that radiologists have to read and the number of structures and diseases they have to evaluate, it is important not to place undue time restraints on the radiologist to this end. We hypothesized that generating panoramic dental radiographs from non-dental CT scans can permit identification of key diseases, while not adding much time to interpretation. The key advantage of panoramic dental radiographs is that they display the plane of the teeth in two dimensions, thereby facilitating fast and accurate assessment. We found that interpreting panoramic radiographic reconstructions compared to the full CT volumes reduced time-to-diagnosis of key dental pathology on average by roughly a factor of four. This expedition was statistically significant, and the average time-to-diagnosis for panoramic reconstructions was on the order of seconds, without a loss in accuracy compared to full CT. As such, we posit that panoramic reconstruction can serve as a one-slice additional series in any CT image stack that includes the teeth in its field of view.

Background: Cardiac computed tomography (CT) is emerging as an adjunctive modality to echocardiography in the evaluation of infective endocarditis (IE) and surgical planning. CT studies in IE have, however, focused on its diagnostic rather than prognostic utility, the latter of which is important in high-risk diseases like IE. We evaluated the associations between cardiac CT and transesophageal echocardiography (TEE) findings and adverse outcomes after IE surgery. Methods: Of 833 consecutive patients with surgically proven IE during May 1, 2014 to May 1, 2019, at Cleveland Clinic, 155 underwent both preoperative ECG-gated contrast-enhanced CT and TEE. Multivariable analyses were performed to identify CT and TEE biomarkers that predict adverse outcomes after IE surgery, adjusting for EuroSCORE II (European System for Cardiac operative Risk Evaluation II). Results: CT and TEE were positive for IE in 123 (75.0%) and 124 (75.6%) of patients, respectively. Thirty-day mortality occurred in 3 (1.9%) patients and composite mortality or morbidities in 72 (46.5%). Pseudoaneurysm or abscess detected on TEE was the only imaging biomarker to show independent association with composite mortality or morbidities in-hospital, with odds ratio (95% CI) of 3.66 (1.76–7.59), P =0.001. There were 17 late deaths, and both pseudoaneurysm or abscess detected on CT and fistula detected on CT were the only independent predictors of total mortality during follow-up, with hazards ratios (95% CI) of 3.82 (1.25–11.7), P P =0.007, respectively. Conclusions: We identified cardiac CT and TEE features that predicted separate adverse outcomes after IE surgery. Imaging biomarkers can play important roles incremental to conventional clinical factors for risk stratification in patients undergoing IE surgery.

Purpose of review To review acute findings commonly encountered during routine clinical FDG PET/CT studies and present key imaging features to differentiate them from malignant counterparts. Recent findings FDG PET/CT is extensively used in routine clinical practice for oncology patients. Incidental acute findings in patients undergoing FDG PET/CT are increasingly common, and awareness of these findings and their mimics are important in delivering a clinically relevant and accurate radiological report for directing further management. Summary This article will review examples of common acute findings encountered during routine FDG PET/CT scans, compare them against examples of FDG-avid malignancy that can mimic these findings and emphasize key imaging findings to differentiate acute findings from their malignant mimics.

Purpose Some consider fluorodeoxyglucose positron emission tomography with computed tomography (FDG-PET/CT) clinically useful in patients presenting with nonspecific symptoms of malignancy, weight loss most commonly encountered. However, the appropriateness of such FDG-PET/CT studies remains to be clarified. This study evaluated the clinical value of FDG-PET/CT in patients referred primarily for weight loss. Methods From 2010 to 2017 in one academic center, 252 subjects underwent 254 FDG-PET/CT studies for weight loss as primary indication and retrospectively studied. Eighteen subjects were excluded due to ongoing active malignancy, weight loss not ultimately being the main indication for the FDG-PET/CT, technically inadequate FDG-PET/CT and insufficient follow-up. The FDG-PET/CT scans were considered clinically beneficial when true positive for the cause of weight loss that other investigations missed or would have missed, clinically neutral when true negative and clinically detrimental when false positive leading to additional investigations or false negative. Results Ultimately 234 unique subjects (236 FDG-PET/CT studies) were included. The average subject weight loss prior to the PET was 12 kg and average follow-up time post FDG-PET/CT scan was 3.4 years. The FDG-PET/CT scans were true positive in 24 studies (10%) with 8 studies (3%) clinically beneficial; false positive in 38 studies (16%) of which 26 led to 35 additional procedures and false negative in 13 studies (6%). In total, 39 (17%) FDG-PET/CT studies were clinically detrimental. The other 149 (63%) studies were true negative, clinically neutral. Conclusion FDG-PET/CT appears to have limited value in assessing subjects with weight loss as the leading clinical indication, proving to be five times more often detrimental than beneficial.

Purpose The aims of this study were to determine the prevalence and outcomes of extrapulmonary malignancies identified on lung cancer screening (LCS) and to determine the cost associated with the investigation of these lesions. Methods This retrospective study included 7,414 low-dose CT studies performed between June 2014 and December 2019 on 4,160 patients as part of an established LCS program. Patients with indeterminate extrapulmonary lesions were identified, and the diagnostic workup, management, and outcomes of the lesions were determined. Costs related to diagnostic evaluation were estimated using 2020 total facility relative value units and the 2020 Medicare conversion factor. Out-of-pocket costs were extracted from billing records. Results There were 20 extrapulmonary malignancies among 241 reported lesions in 225 patients (mean age, 66.1 ± 6.4 years; 109 men, 116 women). The prevalence of extrapulmonary malignancy was 20 of 4,160 (0.48%). Early-stage cancers were detected in 13 of 20 (65%). No cancer-specific mortality was observed. The predictive value for malignancy varied by organ (P = .03) and was highest in the chest wall and axilla (36.4%), followed by bone (25%). The average cost on the basis of Medicare reimbursement for diagnosis of an extrapulmonary malignancy on LCS was $1,316.03 ($6.33 per participant and $109.21 per indeterminate incidental lesion). Most patients (203 of 225 [90.2%]) did not have out-of-pocket costs related to diagnostic workup. In those who did, the median cost was $160.60 (range, $75-$606.76). Conclusions Low-dose CT for LCS detects extrapulmonary malignancy with high predictive value for certain locations. There is cost associated in the workup related to these incidental lesions, but most malignancies are detected at early stages and have good outcomes.

Studies show that up to 80% of all radiology errors are due to errors in perception. Early detection is critical for good outcomes in patients with primary lung cancer and lung metastasis. However, pulmonary nodules can be easily missed due to their small size. We prospectively applied a machine vision algorithm to CT studies containing lung parenchyma to detect pulmonary nodules, as well as a natural language processing algorithm to the text of the report to identify documentation of pulmonary nodules. Apparent discrepancies in perception – instances where a pulmonary nodule was not reported – were flagged for a secondary review by a radiologist. Four thousand and nine hundred studies were prospectively processed, of which 450 cases with potential discrepancies were detected. Preliminary manual analysis was performed to analyze the base error rate and to optimize thresholds for the machine vision and natural language processing algorithms, and 104 cases were flagged for final review. Of these 104 cases, 50 cases contained undocumented pulmonary nodules. Among these cases, 7 cases were classified as likely to be significant, where report addendums were done and the clinicians notified. We have successfully implemented an automated double read system to detect pulmonary nodule discrepancies, with minimal disruption to the radiology workflow and while keeping personal health information on-premises. This successful implementation demonstrates the viability of using an automated and secure radiology double-read system to improve patient safety in radiology workflows, either at a health system or an independent radiology practice.

Purpose To evaluate diagnostic accuracy and clinical outcomes of patients with porcelain gallbladder (GB) diagnosed on CT. Materials and Methods In this IRB-approved, HIPAA-compliant study, consecutive patients with porcelain gallbladder reported on CT between December 1, 2000 and August 31, 2017 in a tertiary academic center were included. Two radiologists independently reviewed CT images and confirmed presence of porcelain gallbladder. Discrepant cases were reviewed by a third reader with 15 years of experience in abdominal imaging. Porcelain gallbladder diagnosis was confirmed by surgery/pathology or follow-up imaging. Results Porcelain gallbladder was reported in 133 CT studies. Radiologist review and pathology results confirmed porcelain gallbladder in 90/133 (68%) patients (age 71.6 ± 13.8 years, 57% female). One third (42/133; 32%) of CT reports were false positive; 1/133 (1%) remained indeterminate. Frequent pitfalls included: stones filling the whole gallbladder lumen in 39/43 (91%), sludge in 3/43 (7%) and mucosal enhancement in 2/43 (5%). In 5/90 (6%) patients, concurrent gallbladder cancer was noted on the initial CT scan. No patient developed subsequent gallbladder cancer during 6.6 ± 4.6 years of follow-up. One third (30/90, 33%) of patients with porcelain gallbladder have deceased during the follow-up period, all from unrelated causes. Conclusion At the time of presentation with porcelain gallbladder, 6% of patients had concurrent gallbladder cancer. No patient with porcelain gallbladder alone diagnosed on CT developed gallbladder cancer during a follow-up of 6.6 ± 4.6 years. Porcelain gallbladder is overcalled on CT, with frequent pitfalls including gallstones filling the whole gallbladder lumen, sludge, and wall enhancement.

Background Atypical manifestations of coronavirus disease 2019 (COVID-19) are being encountered as the pandemic unfolds, leading to non–chest CT scans that may uncover unsuspected pulmonary disease. Purpose To investigate patients with primary nonrespiratory symptoms who underwent CT of the abdomen or pelvis or CT of the cervical spine or neck with unsuspected findings highly suspicious for pulmonary COVID-19. Materials and Methods This retrospective study from March 10, 2020, to April 6, 2020, involved three institutions, two in a region considered a hot spot (area of high prevalence) for COVID-19. Patients without known COVID-19 were included who presented to the emergency department (ED) with primary nonrespiratory (gastrointestinal or neurologic) symptoms, had lung parenchymal findings suspicious for COVID-19 at non–chest CT but not concurrent chest CT, and underwent COVID-19 testing in the ED. Group 1 patients had reverse transcription polymerase chain reaction (RT-PCR) results obtained before CT scan reading (COVID-19 suspected on presentation); group 2 had RT-PCR results obtained after CT scans were read (COVID-19 not suspected). Presentation and imaging findings were compared, and outcomes were evaluated. Descriptive statistics and Fisher exact tests were used for analysis. Results Group 1 comprised 62 patients (31 men, 31 women; mean age, 67 years ±17 [standard deviation]), and group 2 comprised 57 patients (28 men, 29 women; mean age, 63 years ± 16). Cough and fever were more common in group 1 (37 of 62 [60%] and 29 of 62 [47%], respectively) than in group 2 (nine of 57 [16%] and 12 of 57 [21%], respectively), with no significant difference in the remaining symptoms. There were 101 CT scans of the abdomen or pelvis and 18 CT scans of the cervical spine or neck. In group 1, non–chest CT findings provided the initial evidence of COVID-19–related pneumonia in 32 of 62 (52%) patients. In group 2, the evidence was found in 44 of 57 (77%) patients. Overall, the most common CT findings were ground-glass opacity (114 of 119, 96%) and consolidation (47 of 119, 40%). Major interventions (vasopressor medication or intubation) were required for 29 of 119 (24%) patients, and 27 of 119 (23%) died. Patients who underwent CT of the cervical spine or neck had worse outcomes than those who underwent abdominal or pelvic CT (P = .01). Conclusion In a substantial percentage of patients with primary nonrespiratory symptoms who underwent non–chest CT, CT provided evidence of coronavirus disease 2019–related pneumonia. © RSNA, 2020

OBJECTIVE: To develop a deep convolutional neural network (CNN) to automatically segment an axial CT image of the pelvis for body composition measures. We hypothesized that a deep CNN approach would achieve high accuracy when compared to manual segmentations as the reference standard.MATERIALS AND METHODS: We manually segmented 200 axial CT images at the supra-acetabular level in 200 subjects, labeling background, subcutaneous adipose tissue (SAT), muscle, inter-muscular adipose tissue (IMAT), bone, and miscellaneous intra-pelvic content. The dataset was randomly divided into training (180/200) and test (20/200) datasets. Data augmentation was utilized to enlarge the training dataset and all images underwent preprocessing with histogram equalization. Our model was trained for 50 epochs using the U-Net architecture with batch size of 8, learning rate of 0.0001, Adadelta optimizer and a dropout of 0.20. The Dice (F1) score was used to assess similarity between the manual segmentations and the CNN predicted segmentations.RESULTS: The CNN model with data augmentation of N = 3000 achieved accurate segmentation of body composition for all classes. The Dice scores were as follows: background (1.00), miscellaneous intra-pelvic content (0.98), SAT (0.97), muscle (0.95), IMAT (0.91), and bone (0.92). Mean time to automatically segment one CT image was 0.07 s (GPU) and 2.51 s (CPU).CONCLUSIONS: Our CNN-based model enables accurate automated segmentation of multiple tissues on pelvic CT images, with promising implications for body composition studies.

Purpose: To study interreader variability for classifying pulmonary opacities at CT as perifissural nodules (PFNs) and determine how reliably radiologists differentiate PFNs from malignancies. Materials and Methods: CT studies were obtained retrospectively from the National Lung Screening Trial (2002-2009). Nodules were eligible for the study if they were noncalcified, solid, within the size range of 5 to 10 mm, and scanned with a section thickness of 2 mm or less. Six radiologists classified 359 nodules in a cancer-enriched data set as PFN, non-PFN, or not applicable. Nodules classified as not applicable by at least three radiologists were excluded, leaving 316 nodules for post-hoc statistical analysis. Results: The study group contained 22.2% cancers (70 of 316). The median proportion of nodules classified as PFNs was 45.6% (144 of 316). All six radiologists uniformly classified 17.7% (56 of 316) of the nodules as PFNs. The Fleiss k was 0.50. Compared with non-PFNs, nodules classified as PFNs were smaller and more often located in the lower lobes and attached to a fissure (P , .001). Thirteen (18.6%) of 70 cancers were misclassified 21 times as PFNs. Individual readers' misclassification rates ranged from 0% (0 of 125) to 4.9% (eight of 163). Of 13 misclassified malignancies, 11 were in the upper lobes and two were attached to a fissure. Conclusion: There was moderate interreader agreement when classifying nodules as perifissural nodules. Less than 2.5% of perifissural nodule classifications were misclassified lung cancers (21 of 865) in this cancer-enriched study. Allowing nodules classified as perifissural nodules to be omitted from additional follow-up in a screening setting could substantially reduce the number of unnecessary scans; excluding perifissural nodules in the upper lobes would greatly decrease the misclassification rate.