An integrated nomogram combining clinical and radiomic features of hyperattenuated imaging markers to predict malignant cerebral edema following endovascular thrombectomy.

Background: Malignant cerebral edema (MCE), a potential complication following endovascular thrombectomy (EVT) in the treatment of acute ischemic stroke (AIS), can result in significant disability and mortality. This study aimed to develop a nomogram model based on the hyperattenuated imaging marker (HIM), characterized by hyperattenuation on head noncontrast computed tomography (CT) immediately after thrombectomy, to predict MCE in patients receiving EVT. Methods: In this retrospective cohort study, we selected 151 patients with anterior circulation large-vessel occlusion who received endovascular treatment. The patients were randomly allocated into training (n=121) and test (n=30) cohorts. HIM was used to extract radiomics characteristics. Conventional clinical and radiological features associated with MCE were also extracted. A model based on extreme gradient boosting (XGBoost) machine learning using fivefold cross-validation was employed to acquire radiomics and clinical features. Based on HIM, clinical and radiological signatures were used to construct a prediction nomogram for MCE. Subsequently, the signatures were merged through logistic regression (LR) analysis in order to create a comprehensive clinical radiomics nomogram. Results: A total of 28 patients out of 151 (18.54%) developed MCE. The analysis of the receiver operating characteristic curve indicated an area under the curve (AUC) of 0.999 for the prediction of MCE in the training group and an AUC of 0.938 in the test group. The clinical and radiomics nomogram together showed the highest accuracy in predicting outcomes in both the training and test groups. Conclusions: The novel nomogram, which combines clinical manifestations and imaging findings based on postinterventional HIM, may serve as a predictor for MCE in patients experiencing AIS after EVT.

Evaluation of pancreatic iodine uptake and related influential factors in multiphase dual-energy CT.

OBJECTIVES: To establish normative values and identify potential factors influencing pancreatic iodine uptake using dual-energy CT (DECT). MATERIALS AND METHODS: This retrospective study included participants without pancreatic diseases undergoing DECT at two institutions with different platforms. Their protocols both included arterial phase (AP), portal venous phase (PP), and equilibrium phase (EP), defined as 35 s-40 s, 60 s-70 s, and 150 s-180 s after injection of contrast agent, respectively. Both iodine concentration (IC) and normalised IC (NIC) were measured. Demographic features, local measurements of the pancreas and visceral fat area (VFA) were considered as potential factors influencing iodine uptake using multivariate linear regression analyses. RESULTS: A total of 562 participants (median age 58 years [interquartile range: 47-67], with 282 men) were evaluated. The mean IC differed significantly between two institutions (all p < 0.001) across three contrast-enhanced phases, while the mean NIC showed no significant differences (all p > 0.05). The mean values of NIC were 0.22 at AP, 0.43 at PP and 0.45 at EP. NICAP was independently affected by VFA (ß = 0.362, p < 0.001), smoking (ß = -0.240, p = 0.001), and type-II diabetes (ß = -0.449, p < 0.001); NICPP by VFA (ß = -0.301, p = 0.017) and smoking (ß = -0.291, p < 0.001); and NICEP by smoking (ß = -0.154, p = 0.10) and alcohol consumption (ß = -0.350, p < 0.001) with statistical power values over 0.81. CONCLUSION: NIC values were consistent across institutions. Abdominal obesity, smoking, alcohol consumption, and diabetes are independent factors influencing pancreatic iodine uptake. CLINICAL RELEVANCE STATEMENT: This study has provided reference normative values, influential factors and effective normalisation methods of pancreatic iodine uptake in multiphase dual-energy CT for future studies in this area as a new biological marker. KEY POINTS: Evaluation of pancreatic iodine uptake measured by dual-energy CT is a promising method for future studies. Abdominal obesity, smoking, alcohol consumption, diabetes, and sex are independent factors influencing pancreatic iodine uptake. Utility of normalised iodine concentration is necessary to ensure the consistency across different institutions.

Multi-Energy Low-Kiloelectron Volt versus Single-Energy Low-Kilovolt Images for Endoleak Detection at CT Angiography of the Aorta.

Purpose To compare image quality, diagnostic performance, and conspicuity between single-energy and multi-energy images for endoleak detection at CT angiography (CTA) after endovascular aortic repair (EVAR). Materials and Methods In this single-center prospective randomized controlled trial, individuals undergoing CTA after EVAR between August 2020 and May 2022 were allocated to imaging using either low-kilovolt single-energy images (SEI; 80 kV, group A) or low-kiloelectron volt virtual monoenergetic images (VMI) at 40 and 50 keV from multi-energy CT (80/Sn150 kV, group B). Scan protocols were dose matched (volume CT dose index: mean, 4.5 mGy ± 1.8 [SD] vs 4.7 mGy ± 1.3, P = .41). Contrast-to-noise ratio (CNR) was measured. Two expert radiologists established the reference standard for the presence of endoleaks. Detection and conspicuity of endoleaks and subjective image quality were assessed by two different blinded radiologists. Interreader agreement was calculated. Nonparametric statistical tests were used. Results A total of 125 participants (mean age, 76 years ± 8; 103 men) were allocated to groups A (n = 64) and B (n = 61). CNR was significantly lower for 40-keV VMI (mean, 19.1; P = .048) and 50-keV VMI (mean, 16.8; P < .001) as compared with SEI (mean, 22.2). In total, 45 endoleaks were present (A: 23 vs B: 22). Sensitivity for endoleak detection was higher for SEI (82.6%, 19 of 23; P = .88) and 50-keV VMI (81.8%, 18 of 22; P = .90) as compared with 40-keV VMI (77.3%, 17 of 22). Specificity was comparable among groups (SEI: 92.7%, 38 of 41; both VMI energies: 92.3%, 35 of 38; P = .99), with an interreader agreement of 1. Conspicuity of endoleaks was comparable between SEI (median, 2.99) and VMI (both energies: median, 2.87; P = .04). Overall subjective image quality was rated significantly higher for SEI (median, 4 [IQR, 4-4) as compared with 40 and 50 keV (both energies: median, 4 [IQR, 3-4]; P < .001). Conclusion SEI demonstrated higher image quality and comparable diagnostic accuracy as compared with 50-keV VMI for endoleak detection at CTA after EVAR. Keywords: Aneurysms, CT, CT Angiography, Vascular, Aorta, Technology Assessment, Multidetector CT, Abdominal Aortic Aneurysms, Endoleaks, Perigraft Leak Supplemental material is available for this article. © RSNA, 2024.

Computed tomography derived anatomical predictors of vascular access complications following transfemoral transcatheter aortic valve implantation: A systematic review.

BACKGROUND: Vascular complications after percutaneous transfemoral transcatheter aortic valve implantation (TAVI) are associated with adverse clinical outcomes and remain a significant challenge. AIMS: The purpose of this review is to synthesize the existing evidence regarding the iliofemoral artery features predictive of vascular complications after TAVI on pre-procedural contrast-enhanced multidetector computed tomography (MDCT). METHODS: A systematic search was performed in Embase and Medline (Pubmed) databases. Studies of patients undergoing transfemoral TAVI with MDCT were included. Studies with only valve-in-valve TAVI, planned surgical intervention and those using fluoroscopic assessment were excluded. Data on study cohort, procedural characteristics and significant predictors of vascular complications were extracted. RESULTS: We identified 23 original studies involving 8697 patients who underwent TAVI between 2006 and 2020. Of all patients, 8514 (97.9%) underwent percutaneous transfemoral-TAVI, of which 8068 (94.8%) had contrast-enhanced MDCT. The incidence of major vascular complications was 6.7 ± 4.1% and minor vascular complications 26.1 ± 7.8%. Significant independent predictors of major and minor complications related to vessel dimensions were common femoral artery depth (>54 mm), sheath-to-iliofemoral artery diameter ratio (>0.91-1.19), sheath-to-femoral artery diameter ratio (>1.03-1.45) and sheath-to-femoral artery area ratio (>1.35). Substantial iliofemoral vessel tortuosity predicted 2-5-fold higher vascular risk. Significant iliofemoral calcification predicted 2-5-fold higher risk. The iliac morphology score was the only hybrid scoring system with predictive value. CONCLUSIONS: Independent iliofemoral predictors of access-site complications in TAVI were related to vessel size, depth, calcification and tortuosity. These should be considered when planning transfemoral TAVI and in the design of future risk prediction models.

Right Aortic Arch with Bicarotid Trunk and Isolated Left Subclavian Artery: Hitherto Unreported Pattern.

Variant arch anatomy may be seen associated with many congenital heart diseases. Its accurate preoperative identification is of paramount importance in optimal surgical planning of such cases. This case describes one such variant arch anatomy with two vessel right aortic arch, comprising of bicarotid trunk (giving rise to bilateral common carotid arteries) and right subclavian artery with isolation of the left subclavian artery, in a patient with tetralogy of Fallot. Right aortic arch with isolated left subclavian artery has already been described in association with tetralogy of Fallot. However, to the best of our knowledge, present arch pattern consisting of right aortic arch with bicarotid trunk and isolated left subclavian artery has not been reported in literature so far. Moreover, this case highlights the utility of multidetector computed tomography in accurate identification of variant arch anatomy in addition to delineation of cardiac and extracardiac details.

MDCT evaluation of Dorsal Pancreatic Artery and Intrapancreatic arcade anatomy.

OBJECTIVE: The purpose of the study was to analyze the anatomy and variations in the origin of the dorsal pancreatic artery, greater pancreatic artery and to study the various types of arterial arcades supplying the pancreas on multidetector CT (MDCT). METHODS: A retrospective analysis of 747 MDCT scans was performed in patients who underwent triple phase or dual phase CT abdomen between December 2020 and October 2022. Variations in origin of Dorsal pancreatic artery (DPA), greater pancreatic artery (GPA), uncinate process branch were studied. Intrapancreatic arcade anatomy was classified according to Roman Ramos et al. into 4 types-small arcades (type I), small and large arcades (type II), large arcades (type III) and straight branches (type IV). RESULTS: The DPA was visualized in 65.3% (n = 488) of cases. The most common origin was from the splenic artery in 58.2% (n = 284) cases. The mean calibre of DPA was 2.05 mm (1.0-4.8 mm). The uncinate branch was seen in 21.7% (n = 106) with an average diameter of 1.3 mm. The greater pancreatic artery was seen in 57.3% (n = 428) predominantly seen arising from the splenic artery. The most common arcade anatomy was of Type II in 52.1% (n = 63) cases. CONCLUSION: Pancreatic arterial variations are not very uncommon in daily practice. Knowledge of these variations before pancreatic surgery and endovascular intervention procedure is important for surgeons and interventional radiologist.

Pancreatic Cystic Lesions: Imaging Techniques and Diagnostic Features.

The detection of incidental pancreatic cystic lesions has increased over time. It is crucial to separate benign from potentially malignant or malignant lesions to guide management and reduce morbidity and mortality. The key imaging features used to fully characterize cystic lesions are optimally assessed by contrast-enhanced magnetic resonance imaging/magnetic resonance cholangiopancreatography, with pancreas protocol computed tomography offering a complementary role. While some imaging features have high specificity for a particular diagnosis, overlapping imaging features between diagnoses may require further investigation with follow-up diagnostic imaging or tissue sampling.

Partial anomalous pulmonary venous connection: state-of-the-art review with assessment using a multidetector computed tomography angiography.

Pulmonary venous anomalies occur as a result of failure in normal embryological development. These anomalies may present as a spectrum ranging from normal variation to partial anomalous pulmonary venous connection (PAPVC) and total anomalous pulmonary venous connection (TAPVC). Though not rare, PAPVC is an uncommon anomaly in which some of the pulmonary veins abnormally connect and drain into the vascular compartments other than the left atrium (LA); however, the others drain normally into the LA. The clinical presentation and severity of affected patients depend on the morphological heterogeneity of the disease. PAPVC associated with other complex conge-nital cardiac diseases present early and are more severe than isolated PAPVC-associated atrial septal defect only. This radiological review gives a detailed description of PAPVC in terms of morphological variability and associated anomalies along with a discussion of the role of multidetector dual-source computed tomography scan in the diagnostic assessment.

Contrast-enhanced multidetector computed tomography features and histogram analysis can differentiate ameloblastomas from central giant cell granulomas.

BACKGROUND: No qualitative or quantitative analysis of contrast-enhanced computed tomography (CT) images has been reported for the differentiation between ameloblastomas and central giant cell granulomas (CGCGs). AIM: To describe differentiating multidetector CT (MDCT) features in CGCGs and ameloblastomas and to compare differences in enhancement of these lesions qualitatively and using histogram analysis. METHODS: MDCT of CGCGs and ameloblastomas was retrospectively reviewed to evaluate qualitative imaging descriptors. Histogram analysis was used to compare the extent of enhancement of the soft tissue. Fisher's exact tests and Mann-Whitney U test were used for statistical analysis (P < 0.05). RESULTS: Twelve CGCGs and 33 ameloblastomas were reviewed. Ameloblastomas had a predilection for the posterior mandible with none of the CGCGs involving the angle. CGCGs were multilocular (58.3%), with a mixed lytic sclerotic appearance (75%). Soft tissue component was present in 91% of CGCGs, which showed hyperenhancement (compared to surrounding muscles) in 50% of cases, while the remaining showed isoenhancement. Matrix mineralization was present in 83.3% of cases. Ameloblastomas presented as a unilocular (66.7%), lytic (60.6%) masses with solid components present in 81.8% of cases. However, the solid component showed isoenhancement in 63%. No matrix mineralization was present in 69.7% of cases. Quantitatively, the enhancement of soft tissue in CGCG was significantly higher than in ameloblastoma on histogram analysis (P < 0.05), with a minimum enhancement of > 49.05 HU in the tumour providing 100% sensitivity and 85% specificity in identifying a CGCG. CONCLUSION: A multilocular, lytic sclerotic lesion with significant hyperenhancement in soft tissue, which spares the angle of the mandible and has matrix mineralization, should indicate prospective diagnosis of CGCG.

Management of vertebral compression fractures: the role of dual-energy CT in clinical practice.

PURPOSE: To evaluate the role of dual-energy computed tomography (DECT) in the management of vertebral compression fractures in clinical practice. MATERIALS AND METHODS: This retrospective IRB-approved study included 497 consecutive patients with suspected acute vertebral fractures, imaged either by DECT (group 1) or MRI (group 2) before vertebroplasty. The site, number and type of fractures at imaging findings, and clinical outcome based on any change in pain (DELTA-VAS), before (VAS-pre) and after treatment (VAS-post), were determined and compared. Two radiologists evaluated DECT and MRI images (15 and 5 years of experience, respectively), and inter-observer and intra-observer agreement were calculated using k statistics. RESULTS: Both in the control group (n = 124) and in the group of patients treated by vertebroplasty (n = 373), the clinical outcome was not influenced by the imaging approach adopted, with a DELTA-VAS of 5.45 and 6.42 in the DECT group and 5.12 and 6.65 in the MRI group (p = 0.326; p = 0.44). In the group of treated patients, sex, age, lumbar fractures, multiple fractures, previous fractures, Genant grade, involvement of anterior apex or superior endplates, and increased spinal curvatures were similar (p = ns); however, dorsal fractures were more prevalent in group 1 (p = 0.0197). Before treatment, the mean VAS-pre was 8.74 in group 1 (DECT) and 8.65 in group 2 (MRI) (p = 0.301), whereas after treatment, the mean VAS-post value was 2.32 in group 1 (p = 0.0001), and 2.00 in group 2 (p = 0.0001). The DELTA-VAS was 6.42 in the group of patients imaged using DECT and 6.65 in the group imaged using MRI (p = 0.326). Inter-observer and intra-observer agreement were 0.85 and 0.89 for DECT, and 0.88 and 0.91 for MRI, respectively. CONCLUSION: The outcome of vertebral compression fracture management was no different between the two groups of patients studied.

Efficacy of larger valve sizing with underfilling in balloon-expandable transcatheter aortic valve replacement.

OBJECTIVES: To investigate the efficacy and safety of larger valve sizing beyond the commercially recommended annular range in transcatheter aortic valve replacement (TAVR) with balloon-expandable transcatheter heart valve (THVs). BACKGROUND: The clinical implications of larger balloon-expandable THV implantation with underfilling are poorly evaluated. METHODS: This retrospective study included 692 consecutive patients who underwent TAVR with SAPIEN3. A total of 271 patients who underwent SAPIEN 3 implantation were analyzed based on three border zones (Zone 1: 300-345 mm2 , 23 vs. 20 mm; Zone 2: 400-430 mm2 , 26 vs. 23 mm; Zone 3: 500-546 mm2 , 29 vs. 26 mm). The primary endpoint was the effective orifice area (EOA) assessed by echocardiography at 1 year, and secondary endpoints were a 30-day mortality rate, procedural complications during TAVR, and a composite of death from any cause and heart failure requiring rehospitalization at 1 year. RESULTS: At 1-year follow-up, the EOA in the larger valve groups was greater than that in the recommended valve group in each zone (Zone 1: 1.45 ± 0.03 vs. 1.06 ± 0.06 cm2 , p < 0.001; Zone 2: 1.83 ± 0.05 vs. 1.41 ± 0.05 cm2 , p < 0.001; Zone 3: 1.93 ± 0.07 vs. 1.69 ± 0.07 cm2 , p = 0.02). No significant difference in the secondary endpoint was observed in any of the zones. CONCLUSIONS: Implantation of the out-of-range larger SAPIEN 3 THVs with underfilling was associated with greater EOA at the 1-year follow-up and feasible in the selected patients.

Magnetic Resonance Angiography and Multidetector CT Angiography in the Diagnosis of Takayasu's Arteritis: Assessment of Disease Extent and Correlation with Disease Activity.

BACKGROUND: Takayasu's Arteritis (TA) is a large vessel vasculitis with diverse clinical presentations and arterial vascular bed involvement.It is characterized by chronic, nonspecific inflammation of all layers of the vessel wall which results in stenosis, occlusion, dilatation, or aneurysm formation in the involved blood vessels. METHODS: The study included 36 patients of TA. All patients fulfilled the modified Ishikawa's diagnostic criteria for TA. All patients were evaluated for clinical presentation, angiographic findings, and severity of the disease. The disease activity was assessed based on Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP) and also by CT Angiography (CTA)/Magnetic resonance angiography (MRA) imaging. The angiographic types were classified based on the International TA Conference in Tokyo 1994 angiographic classification. RESULTS: A total of 36 patients were included in the study, 86% were females and a mean age of 21.6 years. Hypertension (78%) was the most common clinical presentation. Type V was the most common angiographic type (42%) followed by type III (25%), type IV (14%), type IIb (11%), type I (5%) and type IIa (3%). Among the aortic arch branches the left subclavian artery (50%), right subclavian artery (38.8%), left vertebral artery (33.3%) and left common carotid artery (27.7%) were the most commonly involved arteries. Disease activity based on CT / MR imaging showed a significant statistical correlation with elevated ESR and positive CRP (p < 0.0001). Mediastinal lymphadenopathy was seen in 21 patients out of which 11 had active disease. However, no significant correlation was found between mediastinal lymphadenopathy and disease activity. CONCLUSION: TA presents with varied symptomatology and differing vascular involvement. CT/MR angiography is effective in diagnosis and accurately predicted the active stage of the disease.

Intrahepatic inferior vena cava interruption with transhepatic venous continuation initially misdiagnosed as a congenital portosystemic shunt.

We report a case of intrahepatic inferior vena cava interruption with azygos and transhepatic venous continuation discovered incidentally on CT angiography for acute aortic syndrome. The lesion was initially misdiagnosed as a congenital portosystemic shunt on multiphase CT of the liver but subsequent fluoroscopic venogram revealed no evidence of portosystemic shunting. While intrahepatic IVC interruption with azygos continuation is an uncommon but well-known anatomical variant, transhepatic venous continuation is extremely rare and only a few cases have been published. Excluding portosystemic shunting is important for determining management as persistent congenital portosystemic shunts can be associated with significant morbidity.

The role of multidetector computed tomography enterography in the evaluation of localized malignant small intestinal lesions: retrospective radiological and pathological experience.

PURPOSE: Our purpose is to present our experience in using multidetector computed tomography (MDCT) enterography in the evaluation of localized malignant small intestinal lesions with pathological correlation. MATERIAL AND METHODS: We retrospectively evaluated 53 patients of pathologically proven malignant localized small intestinal tumours, who underwent multidetector CT enterography. RESULTS: In this study, the mean age was 51.39 ± 17.4 years. The most commonly affected age group was from 50 to 59 years. The commonest clinical complaint was abdominal pain. The ileum was the most commonly affected anatomical region, showing 25 lesions (47.16%). Radiologically irregular/asymmetric wall thickening was detected in 42 cases(79.24%). Pathologically the most common malignancy was small intestinal adenocarcinoma, followed by carcinoid tumour, lymphoma, and gastrointestinal stromal tumours (GIST). We found that there was a statistically significant association between the pathological lymphadenopathy (p = 0.005) and absent proximal intestinal dilatation (p = 0.01) with intestinal lymphoma. Also, there was a statistically significant association between the extra-intestinal mesenteric fat changes with carcinoid tumours (p = 0.001). Irregular/asymmetric wall thickening was detected in 14 cases of small intestinal adenocarcinoma with a statistically significant association (p = 0.001) while exophytic pathological mass formation was statistically significant associated (p ≤ 0.001) with small intestinal GIST. CONCLUSIONS: Multidetector CT enterography is a non-invasive and accurate method in the evaluation of focal and localized small intestinal malignant lesions. The accurate detection of these lesions depends to some degree on the experience of the radiologist, lesional size, site and pattern of enhancement, as well as adequate intestinal distension.

Incidentally identified coronary artery calcium on non-contrast CT scan of the chest predicts major adverse cardiac events among hospital inpatients.

BACKGROUND: Coronary artery calcium (CAC) identified on non-gated CT scan of the chest is predictive of major adverse cardiac events (MACE) in multiple studies with guidelines therefore recommending the routine reporting of incidental CAC. These studies have been limited however to the outpatient setting. We aimed to determine the prognostic utility of incidentally identified CAC on CT scan of the chest among hospital inpatients. METHODS AND RESULTS: Consecutive patients (n=740) referred for inpatient non-contrast CT scan of the chest at a tertiary referral hospital (January 2011 to March 2017) were included (n=280) if they had no known history of coronary artery disease, active malignancy or died within 30 days of admission. Scans were assessed for the presence of CAC by visual assessment and quantified by Agatston scoring. Median age was 69 years (IQR: 54-82) and 51% were male with a median CAC score of 7 (IQR 0-205). MACE occurred in 140 (50%) patients at 3.5 years median follow-up including 98 deaths. Half of all events occurred within 18 months. Visible CAC was associated with increased MACE (HR) 6.0 (95% CI: 3.7 to 9.7) compared with patients with no visible CAC. This finding persisted after adjusting for cardiovascular risk factors HR 2.4 (95% CI: 1.3 to 4.3) and with both absolute CAC score and CAC score ≥50th percentile. CONCLUSION: Incidental CAC identified on CT scan of the chest among hospital inpatients provides prognostic information that is independent of cardiovascular risk factors. These patients may benefit from aggressive risk factor modification given the high event rate in the short term.

Ultra-low-dose chest CT performance for the detection of viral pneumonia patterns during the COVID-19 outbreak period: a monocentric experience.

BACKGROUND: Ultra low dose chest computed tomography (CT) acquisitions have been used for selected emergency room patients with acute dyspnea or minor thoracic trauma. The purpose of this study was to evaluate the diagnostic performance of ultra-low-dose (ULD) chest CT for detecting viral pneumonia patterns compared to standard (STD) dose chest CT. METHODS: All consecutive adult patients with two non-enhanced chest CT acquisitions, one STD and one ULD, for suspicion of viral pneumonia between March 5th and April 2nd 2020 were included. CT results were divided into two groups: non-viral pneumonia CT or compatible with viral pneumonia CT based on viral pneumonia CT patterns: ground-glass opacity (GGO), consolidation, crazy paving, air bronchogram signs and fibrous stripes. The diagnostic performance of ULD CT for suspicion of viral pneumonia was evaluated. For CTs compatible with viral pneumonia, CT pattern detection on ULD CT was assessed and STD CT was used as a reference. RESULTS: The study included 380 patients with 97 CTs (25.5%) compatible with viral pneumonia. The mean effective doses (EDs) were 1.66 (1.29; 2.18) mSv for STD and 0.20 (0.18; 0.22) mSv for ULD CT (P<0.001). The sensitivity and specificity of ULD CT for viral pneumonia detection were 98.9% and 99.0%, respectively. GGO, consolidation and fibrous stripes were equally visible in STD and ULD in 100% (n=97), 36% (n=35) and 23% (n=22) of compatible viral pneumonia-CT patients, respectively. Air bronchogram sign detection was equivalent, concerning 23% (n=22) of patients in STD and 22% (n=21) in ULD. Crazy paving was visible in 24% (n=23) of patients in STD and only 8% (n=8) in ULD (P=0.003). CONCLUSIONS: In comparison to STD dose chest CT, ULD chest CT, with a mean reduction dose of 88.0%, has comparable diagnostic performance for detecting viral pneumonia on CT.

CT-Fluoroscopy Image-Fusion Guidance for Embolization of Aortopulmonary Collaterals.

BACKGROUND: In adults with congenital heart disease, anatomically complex culprit collateral vessels may cause life-threatening hemoptysis and require catheter-based embolization. Techniques using conventional 2-dimensional (2D) fluoroscopy can be challenging. TECHNIQUE: We describe a technique using 2D/3-dimensional (3D) image fusion for intraprocedural guidance to embolize aortopulmonary collaterals. Two fluoroscopic images of the thorax at least 30° apart with pigtail catheter in the ascending aorta were used for image fusion with preprocedural computed tomography (CT) angiography using the spine and pigtail catheter as landmarks. 3D planning information was overlaid on 2D fluoroscopy for cannulation and embolization. RESULTS: Between November 2018 and June 2019, a total of 6 sessions of aortopulmonary collateral embolization using CT-fluoroscopy image-fusion guidance were conducted in 3 patients with adult congenital heart disease. In 3/6 sessions, the indication for embolization was hemoptysis. Common target vessels were left and right bronchial arteries (4 and 3 sessions, respectively). The spine and a pigtail catheter in the aorta were frequently used as landmarks for image fusion (67%). Particle embolization was used in 100% of cases. Mean procedure and fluoroscopy times were 3 hours, 23 minutes and 1 hour, 3 minutes, respectively. On average, 169 mL (350 mg iodine/mL) of contrast material was used in each session and total skin dose of radiation exposure was 1538 mGy. Successful collateral embolization was confirmed by postprocedure angiography that showed negligible or no flow through culprit collaterals. CONCLUSION: Use of CT-fluoroscopy image-fusion guidance can aid in embolization of aortopulmonary collaterals with complex anatomy in 3D space.

Utility of noncontrast MRI in the detection and risk grading of gastrointestinal stromal tumor: a comparison with contrast-enhanced CT.

BACKGROUND: Recently developed adjuvant therapies for gastrointestinal stromal tumor (GIST) have been shown to improve patient survival. Guidelines currently recommend contrast-enhanced computed tomography (CECT) for GIST detection and surveillance. Patients with moderate-to-high risk GISTs require more frequent surveillance due to a higher 5-year recurrence rate. Our study aimed to compare noncontrast magnetic resonance imaging (MRI) with CECT for GIST detection, and evaluate volumetric apparent diffusion coefficients (ADCs) for risk stratification of GIST. METHODS: We retrospectively enrolled 83 patients with histopathologically confirmed GISTs for lesion detection efficiency analysis between noncontrast MRI and matched CECT studies. A 5-point scale was used by two independent reviewers to determine if the lesion was present or absent. Another cohort, comprising 28 patients with pathologically confirmed primary GISTs, was further screened for risk stratification, with a comparison of volumetric ADC parameters between the pathologically very-low-to-low risk and moderate-to-high risk GIST patients. RESULTS: For identifying GISTs, the sensitivity and specificity of noncontrast MRI were 83.6% and 89.3% for reader 1 respectively, and 81.8% and 92.9% for reader 2 respectively; the sensitivity and specificity of CECT were 76.4% and 89.3% for reader 1 respectively, and 76.4 and 78.6% for reader 2 respectively. Tumor volumetric ADC histogram parameters, including ADCmax, ADCstdev, 90th and 95th percentiles, inhomogeneity, and entropy, were positively correlated with a higher risk grade of GIST (r=0.421-0.758). The receiver operator characteristic curve analysis showed ADCmax achieved the highest area under the curve value of 0.938 for discriminating very-low-to-low risk versus moderate-to-high risk GISTs. CONCLUSIONS: Noncontrast MRI was an efficient technique for identifying GIST patients. The combination of CECT and noncontrast MRI can improve the reliability of diagnosis. For patients with contraindications to CECT, noncontrast MRI may be a comparable alternative. Volumetric ADC histogram parameters may be useful in differentiating very-low-to-low risk from moderate-to-high risk primary GISTs.

Gradient changes in bioprosthetic valve thrombosis: duration of anticoagulation and strategies to improve detection.

OBJECTIVE: Bioprosthetic valve thrombosis (BPVT) is increasingly recognised as a major cause of prosthetic dysfunction in the first years postimplantation. How early abnormal gradients can be detected prior to diagnosis and how fast they normalise with anticoagulant therapy is unknown. We set forth to (1) evaluate patterns of increase in gradients prior to BPVT diagnosis and (2) characterise time-course of response to anticoagulation. METHODS: Patients treated with warfarin for BPVT (1999-2019) with clinically significant reduction of mean gradients (≥25%) were identified retrospectively. Recovery was defined as gradient decrease ≥50%, to postimplantation or to normal-range gradients per position, model and size. Time-to-BPVT (implantation-BPVT diagnosis), potential diagnostic delay (first abnormal gradient by position, model and size-BPVT diagnosis) and time-to-recovery (BPVT diagnosis-complete resolution) were recorded. RESULTS: 77 patients were identified; 32 (42%) aortic (23 surgical-12 porcine, 11 pericardial; 9 transcatheter); 24 (31%) mitral; 21 (27%) tricuspid. Median time-to-BPVT was 24, 21 and 10 months, respectively. Potential diagnostic delay was median 21 months for aortic, 4 months for mitral, but 0 for tricuspid. Recovery was significantly faster in mitral than aortic (median 2.5 vs 4.8 months, p=0.038) and tricuspid (median 5.9 months, p=0.025) positions. Porcine aortic valves responded faster than pericardial aortic valves (median 2.9 vs 20.3 months, p=0.004). CONCLUSION: Gradients start to increase months before the clinical BPVT diagnosis. Recovery is faster in mitral and surgical aortic porcine valves; a longer warfarin trial seems indicated in tricuspid and surgical aortic pericardial valves.

Effect of different reconstruction algorithms on coronary artery calcium scores using the reduced radiation dose protocol: a clinical and phantom study.

BACKGROUND: This study aimed to evaluate the effects of different iterative reconstruction (IR) algorithms on coronary artery calcium (CAC) score quantification using the reduced radiation dose (RRD) protocol in an anthropomorphic phantom and in patients. METHODS: A thorax phantom, containing 9 calcification inserts with varying hydroxyapatite (HA) densities, was scanned with the reference protocol [120 kv, 80 mAs, filtered back projection (FBP)] and RRD protocol (120 kV, 20-80 mAs, 5 mAs interval) using a 256-slice computed tomography (CT) scanner. Raw data were reconstructed with different reconstruction algorithms [iDose4 levels 1-7 and iterative model reconstruction (IMR) levels 1-3]. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and Agatston score (AS) were calculated for each image series. The correction factor was derived from linear regression analysis between the reference image series and other image series with different parameters. Additionally, 40 patients were scanned with the RRD protocol (50 mAs) and reconstructed with FBP, iDose4 level 4, and IMR level 2. AS was calculated for the 3-group image series, and was corrected by applying a correction factor for the IMR group. The agreement of risk stratification with different reconstruction algorithms was also analyzed. RESULTS: For the phantom study, the iDose4 and IMR groups had significantly higher SNR and CNR than the FBP group (all P<0.05). There were no significant differences in the total AS after comparing image series reconstructed with iDose4 (level 1-7) and FBP (all P>0.05), while AS from the IMR (level 1-3) image series were lower than the FBP group (all P<0.05). The tube current of 50 mAs was determined for the clinical study, and the correction factor was 1.14. For the clinical study, the median AS from the iDose4 and IMR groups were both significantly lower compared to the FBP image series [(112.89 (63.01, 314.09), 113.22 (64.78, 364.95) vs. 118.59 (65.05, 374.48), both P<0.05]. After applying the correction factor, the adjusted AS from the IMR group was not significantly different from that of the FBP group [126.48 (69.62, 355.85) vs. 118.59 (65.05, 374.48), P=0.145]. Moreover, the agreement in risk stratification between FBP and IMR improved from 0.81 to 0.85. CONCLUSIONS: The RRD CAC scoring scan using the IMR reconstruction algorithm is clinically feasible, and a correction factor can help reduce the AS underestimation effect.