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Background The impact of waning vaccine effectiveness on the severity of COVID-19-related findings discovered with radiologic examinations remains underexplored. Purpose To evaluate the effectiveness of vaccines over time against severe clinical and radiologic outcomes related to SARS-CoV-2 infections. Materials and Methods This multicenter retrospective study included patients in the Korean Imaging Cohort of COVID-19 database who were hospitalized for COVID-19 between June 2021 and December 2022. Patients who had received at least one dose of a SARS-CoV-2 vaccine were categorized based on the time elapsed between diagnosis and their last vaccination. Adjusted multivariable logistic regression analysis was used to estimate vaccine effectiveness against a composite of severe clinical outcomes (invasive ventilation, extracorporeal membrane oxygenation, or in-hospital death) and severe radiologic pneumonia (≥25% of lung involvement), and odds ratios (ORs) were compared between patients vaccinated within 90 days of diagnosis and those vaccinated more than 90 days before diagnosis. Results Of 4196 patients with COVID-19 (mean age, 66 years ± 17 [SD]; 2132 [51%] women, 2064 [49%] men), the ratio of severe pneumonia since their most recent vaccination was as follows: 90 days or less, 18% (277 of 1527); between 91 and 120 days, 22% (172 of 783); between 121 and 180 days, 27% (274 of 1032); between 181 and 240 days, 32% (159 of 496); and more than 240 days, 31% (110 of 358). Patients vaccinated more than 240 days before diagnosis showed increased odds of severe clinical outcomes compared with patients vaccinated within 90 days (OR = 1.94 [95% CI: 1.16, 3.24]; P = .01). Similarly, patients vaccinated more than 240 days before diagnosis showed increased odds of severe pneumonia on chest radiographs compared with patients vaccinated within 90 days (OR = 1.65 [95% CI: 1.13, 2.40]; P = .009). No difference in odds of severe clinical outcomes ( P = .13 to P = .68) or severe pneumonia ( P = .15 to P = .86) were observed between patients vaccinated 91-240 days before diagnosis and those vaccinated within 90 days of diagnosis. Conclusion Vaccine effectiveness against severe clinical outcomes and severe pneumonia related to SARS-CoV-2 infection gradually declined, with increased odds of both observed in patients vaccinated more than 240 days before diagnosis. © RSNA, 2024 Supplemental material is available for this article. See also the editorial by Wells in this issue.

Background Total lung capacity (TLC) has been estimated with use of chest radiographs based on time-consuming methods, such as planimetric techniques and manual measurements. Purpose To develop a deep learning-based, multidimensional model capable of estimating TLC from chest radiographs and demographic variables and validate its technical performance and clinical utility with use of multicenter retrospective data sets. Materials and Methods A deep learning model was pretrained with use of 50 000 consecutive chest CT scans performed between January 2015 and June 2017. The model was fine-tuned on 3523 pairs of posteroanterior chest radiographs and plethysmographic TLC measurements from consecutive patients who underwent pulmonary function testing on the same day. The model was tested with multicenter retrospective data sets from two tertiary care centers and one community hospital, including (a) an external test set 1 ( n = 207) and external test set 2 ( n = 216) for technical performance and (b) patients with idiopathic pulmonary fibrosis ( n = 217) for clinical utility. Technical performance was evaluated with use of various agreement measures, and clinical utility was assessed in terms of the prognostic value for overall survival with use of multivariable Cox regression. Results The mean absolute difference and within-subject SD between observed and estimated TLC were 0.69 L and 0.73 L, respectively, in the external test set 1 (161 men; median age, 70 years [IQR: 61-76 years]) and 0.52 L and 0.53 L in the external test set 2 (113 men; median age, 63 years [IQR: 51-70 years]). In patients with idiopathic pulmonary fibrosis (145 men; median age, 67 years [IQR: 61-73 years]), greater estimated TLC percentage was associated with lower mortality risk (adjusted hazard ratio, 0.97 per percent; 95% CI: 0.95, 0.98; P < .001). Conclusion A fully automatic, deep learning-based model estimated total lung capacity from chest radiographs, and the model predicted survival in idiopathic pulmonary fibrosis. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Sorkness in this issue.

This article reviews the radiologic and pathologic findings of the epithelial and endothelial injuries in COVID-19 pneumonia to help radiologists understand the fundamental nature of the disease. The radiologic and pathologic manifestations of COVID-19 pneumonia result from epithelial and endothelial injuries based on viral toxicity and immunopathologic effects. The pathologic features of mild and reversible COVID-19 pneumonia involve nonspecific pneumonia or an organizing pneumonia pattern, while the pathologic features of potentially fatal and irreversible COVID-19 pneumonia are characterized by diffuse alveolar damage followed by fibrosis or acute fibrinous organizing pneumonia. These pathologic responses of epithelial injuries observed in COVID-19 pneumonia are not specific to SARS-CoV-2 but rather constitute universal responses to viral pneumonia. Endothelial injury in COVID-19 pneumonia is a prominent feature compared with other types of viral pneumonia and encompasses various vascular abnormalities at different levels, including pulmonary thromboembolism, vascular engorgement, peripheral vascular reduction, a vascular tree-in-bud pattern, and lung perfusion abnormality. Chest CT with different imaging techniques (eg, CT quantification, dual-energy CT perfusion) can fully capture the various manifestations of epithelial and endothelial injuries. CT can thus aid in establishing prognosis and identifying patients at risk for deterioration., (© RSNA, 2023.)

Background CT manifestations of SARS-CoV-2 may differ among variants. Purpose To compare the chest CT findings of SARS-CoV-2 between the Delta and Omicron variants. Materials and Methods This retrospective study collected consecutive baseline chest CT images of hospitalized patients with SARS-CoV-2 from a secondary referral hospital when the Delta and Omicron variants were predominant. Two radiologists categorized CT images according to the RSNA classification system for COVID-19 and visually graded pneumonia extent. Pneumonia, pleural effusion, and intrapulmonary vessels were segmented and quantified on CT images using a priori-developed neural networks, followed by reader confirmation. Multivariable logistic and linear regression analyses were performed to examine the associations between the variants and CT category, distribution, severity, and peripheral vascularity. Results In total, 88 patients with the Delta variant (mean age, 67 years ± 15 [SD]; 46 men) and 88 patients with the Omicron variant (mean age, 62 years ± 19; 51 men) were included. Omicron was associated with less frequent, typical peripheral bilateral ground-glass opacity (32% [28 of 88] vs 57% [50 of 88], P = .001), more frequent peribronchovascular predilection (38% [25 of 66] vs 7% [five of 71], P < .001), lower visual pneumonia extent (5.4 ± 6.0 vs 7.7 ± 6.6, P = .02), similar pneumonia volume (5% ± 1 vs 7% ± 11, P = .14), and a higher proportion of vessels with a cross-sectional area smaller than 5 mm 2 relative to the total pulmonary blood volume (BV5%; 48% ± 11 vs 44% ± 8; P = .004). In adjusted analyses, Omicron was associated with a nontypical appearance (odds ratio, 0.34; P = .006), peribronchovascular predilection (odds ratio, 9.2; P < .001), and higher BV5% (β = 3.8; P = .01) but similar visual pneumonia extent ( P = .17) and pneumonia volume ( P = .67) relative to the Delta variant. Conclusion At chest CT, the Omicron SARS-COV-2 variant showed nontypical peribronchovascular pneumonia and less pulmonary vascular involvement than did the Delta variant in hospitalized patients with similar disease severity. © RSNA, 2022 Online supplemental material is available for this article.

Background With the widespread use of gadolinium-based contrast agents (GBCAs), the incidence of allergic-like hypersensitivity reactions (HSRs) to GBCAs is increasing. Research on the incidence and risk factors for HSRs to GBCAs is needed for their safe use. Purpose To determine the incidence of acute and delayed reactions to GBCAs and to discuss the risk factors and strategies for the prevention of HSRs to GBCAs. Materials and Methods All cases of HSRs to contrast media that occurred at the Seoul National University Hospital from July 1, 2012, to June 30, 2020, were assessed. Information including age, sex, GBCA type, onset, and severity of HSRs was retrospectively analyzed. Results Among the 331070 cases of GBCA exposure in 154539 patients, 1304 cases of HSRs (0.4%) were reported. Acute HSRs accounted for 1178 cases (0.4%), while 126 cases (0.04%) were delayed HSRs. While both premedication (odds ratio [OR] = 0.7, P = .041) and changing the type of GBCA (OR = 0.2, P < .001) showed preventative effects in patients with a history of acute HSRs, only premedication (OR = 0.2, P = .016) significantly reduced the incidence of HSRs in patients with a history of delayed reactions. The risk of an HSR to GBCA was higher in those with a history of an HSR to iodinated contrast media (OR = 4.6, P < .001). Conclusion The rate of hypersensitivity reactions (HSRs) to gadolinium-based contrast agents (GBCAs) was 0.4%. The absence of premedication, repeated exposures to the culprit GBCA, and a history of HSRs to iodinated contrast media and GBCAs were risk factors for HSRs to GBCAs. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Kallmes and McDonald in this issue.

Background Body mass index (BMI) and sarcopenia status are well-established prognostic factors in patients with lung cancer. However, the relationship between the amount of adipose tissue and survival remains unclear. Purpose To investigate the association between baseline adipopenia and outcomes in patients with early-stage non-small cell lung cancer (NSCLC). Materials and Methods Consecutive patients who underwent surgical resection for stage I NSCLC between 2011 and 2015 at a single tertiary care center were retrospectively identified. The primary outcome was the 5-year overall survival (OS) rate, and secondary outcomes were the 5-year disease-free survival (DFS) rate and the major postoperative complication rate. The abdominal total fat volume at the waist and the skeletal muscle area at the L3 level were obtained from preoperative PET/CT data and were normalized by the height squared to calculate the fat volume index (FVI) and skeletal muscle index. Adipopenia was defined as the sex-specific lowest quartile of the FVI for the study sample, and sarcopenia was determined using the skeletal muscle index reference value (men, <55 cm 2 /m 2 ; women, <39 cm 2 /m 2 ). The association between body composition and outcomes was evaluated using Cox regression analysis. Results A total of 440 patients (median age, 65 years [interquartile range, 58-72 years]; 243 men) were evaluated. Most underweight patients (<20 kg/m 2 ) had adipopenia (97%, 36 of 37 patients), but overweight patients (25-30 kg/m 2 , n = 138) and obese patients (>30 kg/m 2 , n = 14) did not have adipopenia (3%, four of 152 patients). In the group with a normal BMI (20-25 kg/m 2 ), 28% (70 of 251 patients) had adipopenia and 67% (168 of 251 patients) had sarcopenia. After adjusting for age, sex, smoking history, surgical procedure, stage, histologic type, BMI, and sarcopenia, adipopenia was associated with reduced 5-year OS (hazard ratio [HR] = 2.2; 95% CI: 1.1, 3.8; P = .02) and 5-year non-cancer-specific OS rates (HR = 3.2; 95% CI: 1.2, 8.7; P = .02). There was no association between adipopenia and postoperative complications ( P = .45) or between adipopenia and the 5-year DFS rate ( P = .18). Conclusion Baseline adipopenia was associated with a reduced 5-year overall survival rate in patients with early-stage non-small cell lung cancer and may indicate risk for non-cancer-related death. © RSNA, 2021 Online supplemental material is available for this article.

Background Determining the activity of pulmonary tuberculosis on chest radiographs is difficult. Purpose To develop a deep learning model to identify active pulmonary tuberculosis on chest radiographs. Materials and Methods Chest radiographs were retrospectively gathered from a multicenter consecutive cohort with pulmonary tuberculosis who were successfully treated between 2011 and 2017, along with normal radiographs to enrich a negative class. The pretreatment and posttreatment radiographs were labeled as positive and negative classes, respectively. A neural network was trained with those radiographs to calculate the probability of active versus healed tuberculosis. A single-center consecutive cohort (test set 1; 89 patients, 148 radiographs) and data from one multicenter randomized controlled trial (test set 2; 366 patients, 3774 radiographs) were used to test the model. The area under the receiver operating characteristic curve (AUC) was used to evaluate the performance of the model and of the four expert readers. Results In total, 6654 pre- and posttreatment radiographs from 3327 patients (mean age ± standard deviation, 55 years ± 19; 1884 men) with pulmonary tuberculosis and 3182 normal radiographs from as many patients (mean age, 53 years ± 14; 1629 men) were gathered. For test set 1, the model showed a higher AUC (0.83; 95% CI: 0.73, 0.89) than one pulmonologist (0.69; 95% CI: 0.61, 0.76; P < .001) and performed similarly to the other readers (AUC, 0.79-0.80; P = .14-.23). For 200 randomly selected radiographs from test set 2, the model had a higher AUC (0.84) than the pulmonologists (0.71 and 0.74; P < .001 and .01, respectively) and performed similarly to the radiologists (0.79 and 0.80; P = .08 and .06, respectively). The model output increased by 0.30 on average with a higher degree of smear positivity (95% CI: 0.20, 0.39; P < .001) and decreased during treatment (baseline, 3 months, and 6 months: 0.85, 0.51, and 0.26, respectively). Conclusion A deep learning model performed similarly to radiologists for accurately determining the activity of pulmonary tuberculosis on chest radiographs; it also was able to follow posttreatment changes. © RSNA, 2021 Online supplemental material is available for this article.

Background The association of pulmonary embolism (PE) with deep vein thrombosis (DVT) in patients with coronavirus disease 2019 (COVID-19) remains unclear, and the diagnostic accuracy of D-dimer tests for PE is unknown. Purpose To conduct meta-analysis of the study-level incidence of PE and DVT and to evaluate the diagnostic accuracy of D-dimer tests for PE from multicenter individual patient data. Materials and Methods A systematic literature search identified studies evaluating the incidence of PE or DVT in patients with COVID-19 from January 1, 2020, to June 15, 2020. These outcomes were pooled using a random-effects model and were further evaluated using metaregression analysis. The diagnostic accuracy of D-dimer tests for PE was estimated on the basis of individual patient data using the summary receiver operating characteristic curve. Results Twenty-seven studies with 3342 patients with COVID-19 were included in the analysis. The pooled incidence rates of PE and DVT were 16.5% (95% CI: 11.6, 22.9; I 2 = 0.93) and 14.8% (95% CI: 8.5, 24.5; I 2 = 0.94), respectively. PE was more frequently found in patients who were admitted to the intensive care unit (ICU) (24.7% [95% CI: 18.6, 32.1] vs 10.5% [95% CI: 5.1, 20.2] in those not admitted to the ICU) and in studies with universal screening using CT pulmonary angiography. DVT was present in 42.4% of patients with PE. D-dimer tests had an area under the receiver operating characteristic curve of 0.737 for PE, and D-dimer levels of 500 and 1000 μg/L showed high sensitivity (96% and 91%, respectively) but low specificity (10% and 24%, respectively). Conclusion Pulmonary embolism (PE) and deep vein thrombosis (DVT) occurred in 16.5% and 14.8% of patients with coronavirus disease 2019 (COVID-19), respectively, and more than half of patients with PE lacked DVT. The cutoffs of D-dimer levels used to exclude PE in preexisting guidelines seem applicable to patients with COVID-19. © RSNA, 2020 Supplemental material is available for this article. See also the editorial by Woodard in this issue.

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Background Recent studies have suggested that chest CT scans could be used as a primary screening or diagnostic tool for coronavirus disease 2019 (COVID-19) in epidemic areas. Purpose To perform a meta-analysis to evaluate diagnostic performance measures, including predictive values of chest CT and initial reverse transcriptase polymerase chain reaction (RT-PCR). Materials and Methods Medline and Embase were searched from January 1, 2020, to April 3, 2020, for studies on COVID-19 that reported the sensitivity, specificity, or both of CT scans, RT-PCR assays, or both. The pooled sensitivity and specificity were estimated by using random-effects models. The actual prevalence (ie, the proportion of confirmed patients among those tested) in eight countries was obtained from web sources, and the predictive values were calculated. Meta-regression was performed to reveal the effect of potential explanatory factors on the diagnostic performance measures. Results The pooled sensitivity was 94% (95% confidence interval [CI]: 91%, 96%; I 2 = 95%) for chest CT and 89% (95% CI: 81%, 94%; I 2 = 90%) for RT-PCR. The pooled specificity was 37% (95% CI: 26%, 50%; I 2 = 83%) for chest CT. The prevalence of COVID-19 outside China ranged from 1.0% to 22.9%. For chest CT scans, the positive predictive value (PPV) ranged from 1.5% to 30.7%, and the negative predictive value (NPV) ranged from 95.4% to 99.8%. For RT-PCR, the PPV ranged from 47.3% to 96.4%, whereas the NPV ranged from 96.8% to 99.9%. The sensitivity of CT was affected by the distribution of disease severity, the proportion of patients with comorbidities, and the proportion of asymptomatic patients (all P < .05). The sensitivity of RT-PCR was negatively associated with the proportion of elderly patients ( P = .01). Conclusion Outside of China where there is a low prevalence of coronavirus disease 2019 (range, 1%-22.9%), chest CT screening of patients with suspected disease had low positive predictive value (range, 1.5%-30.7%). © RSNA, 2020 Online supplemental material is available for this article.

Background Multicenter studies may be required for establishing guidelines for safe usage of iodinated contrast media (ICM). Purpose To identify the prevalence, patterns, risk factors, and preventive measures for ICM-related hypersensitivity reactions (HSRs). Materials and Methods Between March 2017 and October 2017, a total of 196 081 patients who underwent ICM administration were enrolled from seven participating institutions. The occurrence of HSRs and baseline patient information were recorded. χ 2 and Student t test were performed, and logistic regression analyses were used to identify risk factors that predict occurrence and recurrence of HSR. Results Among 196 081 patients (mean age ± standard deviation, 59.1 years ± 16.0; 105 014 men and 91 067 women) who underwent ICM administration, the overall prevalence of HSRs was 0.73% (1433 of 196 081), and severe reactions occurred in 0.01% (17 of 196 081). Conditional logistic regression for patients with HSR ( n = 1433) and a control group (1:1 matched group for age, sex, ICM product, and institution) demonstrated that a patient's previous individual history of an ICM-related HSR (adjusted odds ratio [OR], 198.8; P < .001), hyperthyroidism (adjusted OR, 3.6; P = .04), drug allergy (adjusted OR, 3.5; P < .001), and other allergic diseases (adjusted OR, 6.8; P < .001) and a family history of ICM-related HSRs (adjusted OR, 14.0; P = .01) were predictors of HSR occurrence. Logistic regression analysis showed that use of premedication with antihistamine (OR, 0.5; P = .01) and change in the generic profile of ICM (OR, 0.5; P < .001) were preventive against recurrent HSR. Conclusion Family history as well as previous individual history of hypersensitivity reactions (HSRs) to iodinated contrast media (ICM) were risk factors for HSR occurrence, suggesting a potential genetic predisposition. A change in the culprit ICM and premedication with antihistamine are useful for reducing the recurrence of HSRs. © RSNA, 2019 Online supplemental material is available for this article.

Purpose To evaluate the malignancy risk of lung lesions that show nondiagnostic results at transthoracic needle biopsy (PTNB) of the lung and to identify any malignancy-associated risk factors in each nondiagnostic category. Materials and Methods In this retrospective study, 9384 initial PTNBs (9239 patients [mean age, 65 years; age range, 20-99 years] consisting of 5729 men [mean age, 66 years; age range, 20-99 years] and 3510 women [mean age, 63 years; age range, 20-94 years]) were performed in eight institutions between January 2010 and December 2014. PTNB results were categorized as diagnostic (malignant or specifically benign) or nondiagnostic (nonspecific benign pathologic findings, atypical cells, or insufficient specimen), and the proportion of final malignant diagnoses per nondiagnostic category was obtained. Malignancy-associated factors were determined by using multivariable analyses. Results Nondiagnostic results were present in 27.6% (2590 of 9384) of PTNBs. Proportions of final malignant diagnoses were 21.3% (339 of 1592) for nonspecific benignities, 90.1% (503 of 558) for atypical cells, and 46.6% (205 of 440) for insufficient specimens. In the nonspecific benign category, granulomatous inflammation (odds ratio [OR], 0.04; 95% confidence interval [CI]: 0.02, 0.12; P < .001), abscess (OR, 0.04; 95% CI: 0.01, 0.28; P = .001), and organizing pneumonia (OR, 0.05; 95% CI: 0.01, 0.23; P < .001) were demonstrated to be important factors negating malignancy. Atypical cells suspicious for malignancy were more associated with malignancy (OR, 6.3; 95% CI: 1.9, 21.0; P = .003) than were atypical cells of indeterminate malignancy. All 130 lesions with atypical cells suggestive of malignancy were finally malignant. Conclusion After nondiagnostic lung biopsies, lesions categorized as atypical cell lesions have a high likelihood of malignancy, with somewhat lower likelihood for lesions with insufficient specimens and nonspecific benign categories. © RSNA, 2018 Online supplemental material is available for this article. See also the editorial by Elicker in this issue.

Purpose To evaluate premedication protocols involving administration of antihistamine and multidose corticosteroid that have been widely used in prevention of recurrent hypersensitivity reactions (HSRs) to iodinated contrast media (ICM); an evidence-based optimal preventive strategy customized for patients with mild cases has not yet been established. Materials and Methods The outcomes of patients with mild HSR who subsequently underwent contrast material-enhanced computed tomography (CT) between January 2012 and December 2015 were analyzed. For premedication, 4 mg of chlorpheniramine was intravenously administered 30 minutes prior to reexposure to ICM. Logistic regression with generalized estimating equations was used to determine the relationship between premedication and recurrence rate. Results A total of 1178 patients with mild immediate HSR were reexposed to ICM 3533 times. Among these patients, 1056 patients experienced allergylike reactions and 122 patients developed gastrointestinal reactions. With reexposure to the culprit agent without premedication, the recurrence rate was 31.1% (85 of 273 examinations). The recurrence rate decreased to 12% (105 of 872 examinations; P < .001) by only changing the culprit agent and to 7.6% (148 of 1947 examinations; P < .001) by using the combination of changing the ICM and antihistamine premedication. Changing the ICM plus antihistamine premedication was also helpful in reducing the recurrence of gastrointestinal symptoms from 16.1% to 1.8% (P = .020). However, despite changing of the ICM, some combinations of ICM did not show a prophylactic effect. Conclusion A combination of changing the culprit agent and antihistamine premedication resulted in the best preventive outcome for patients with mild immediate HSR. The optimal choice of substitute ICM could be individualized according to the culprit agent., (© RSNA, 2018 Online supplemental material is available for this article .)

Purpose To evaluate histogram and texture parameters on pretreatment dynamic contrast material-enhanced (DCE) magnetic resonance (MR) images in lung cancer in terms of temporal change, optimal time for analysis, and prognostic potential. Materials and Methods This retrospective study was approved by the institutional review board, and the requirement to obtain informed consent was waived. Thirty-eight patients with pathologically proved lung cancer undergoing standard pretreatment DCE MR imaging were included. A fat-suppressed, T1-weighted, volume-interpolated breath-hold MR sequence was performed every 30 seconds for 300 and 480 seconds after contrast material administration. A region of interest was manually drawn in the largest cross-sectional area of the tumor on DCE MR images to extract semiquantitative perfusion, histogram, and texture parameters. Predictability of 2-year progression-free survival (PFS) was analyzed by using the Kaplan-Meier method and Cox regression analysis. Results MR histogram and texture parameters increased rapidly 30-60 seconds after contrast material administration. Standard deviation and entropy then plateaued, whereas skewness and kurtosis rapidly decreased. Univariate Cox regression analysis revealed that standard deviation and entropy were significant predictors of survival; their statistical significance was preserved from 60 to 300 seconds, with the smallest P values (P ≤ .001) occurring from 120 to 180 seconds. At multivariate Cox regression analysis, entropy was the sole significant predictor of 2-year PFS (hazard ratio at 180 seconds, 10.098 [95% confidence interval: 1.579, 64.577], P = .015; hazard ratio at 120 seconds: 11.202 [95% confidence interval: 1.761, 71.260], P = .010). Conclusion Histogram and texture parameter changes varied after contrast material injection. The 120-180-second window after contrast material injection was optimal for MR imaging-derived texture parameter and entropy at DCE MR imaging. (©) RSNA, 2016 Online supplemental material is available for this article.

Purpose: To evaluate the imaging features of intrahepatic mass-forming cholangiocarcinomas (IMCCs) at computed tomography (CT), with a special emphasis on the degree and pattern of arterial enhancement, and to determine whether the clinicopathologic features of IMCCs with arterial enhancement differ from those of IMCCs with less arterial enhancement., Materials and Methods: The institutional review board of Seoul National University Hospital approved this retrospective study, and informed patient consent was waived. Sixty-four patients with 70 pathologically confirmed IMCCs after surgical resection underwent multiphasic CT-unenhanced, hepatic arterial phase (HAP), portal venous phase, and/or equilibrium phase imaging. CT images were retrospectively evaluated for tumor morphology and enhancement features. Patients were placed into typical or atypical enhancement groups according to the presence of enhancement in the largest volume (>50%) of the tumors during the HAP. Imaging features of IMCCs were correlated with pathologic features. The typical and atypical enhancement groups were compared with respect to disease-free survival and overall survival. Survival rates were calculated by using the Kaplan-Meier method, and differences in survival were compared by using the log-rank test. A Cox proportional hazards model was used for multivariate survival analysis., Results: Fifty (71%) of 70 IMCCs showed typical arterial enhancement, and 20 (29%) showed atypical enhancement. The mean diameter of atypical IMCCs was significantly smaller than that of typical IMCCs (P = .001). Chronic liver disease was more frequent in the group with atypical lesions (P = .021). During the HAP, the prevalent enhancement pattern in this group was a mixed pattern of peripheral rim and internal heterogeneous enhancement. At pathologic evaluation, atypically enhancing IMCCs showed less central stroma and necrosis and larger cellular areas and more frequently had a cholangiolocellular component than typically enhancing IMCCs. Arterial enhancement of IMCCs was found to be an independent prognostic factor for longer disease-free survival., Conclusion: Arterially enhancing IMCCs were not rare; thus, enhancement pattern analysis of arterially enhancing IMCCs will be helpful in differentiating them from hepatocellular carcinomas. In addition, arterial enhancement of IMCCs appears to correlate with disease-free survival.

Purpose: To evaluate the enhancement patterns, prevalence of secondary signs, and histopathologic features of 20-mm-diameter or smaller pancreatic cancers seen on multiphasic multidetector computed tomographic (CT) images., Materials and Methods: This retrospective study was approved by the institutional review board; the requirement for informed consent was waived. From January 2002 through September 2009, the authors reviewed the clinical and imaging data of 130 consecutive patients (76 men, 54 women; mean age, 64.1 years; age range, 28-82 years) who had surgically proven 30-mm-diameter or smaller pancreatic cancers and underwent preoperative multidetector CT and 33 consecutive patients (17 men, 16 women; mean age, 65.1 years; age range, 48-84 years) who had histopathologically proven pancreatic cancer and underwent incidental multidetector CT before the diagnosis was rendered. Only pancreatic phase CT was performed in two patients, and only hepatic venous phase CT was performed in nine patients. Two radiologists in consensus classified the tumor attenuation as hyper-, iso-, or hypoattenuation during the pancreatic and hepatic venous phases. Accompanying secondary signs, temporal changes in tumor attenuation, and histopathologic findings also were analyzed. The Fisher exact test, χ(2) test, generalized estimating equation, and Student t test were used to compare the variables., Results: Seventy tumors were 20 mm or smaller, and 93 were 21-30 mm. Isoattenuating pancreatic cancers were more commonly observed among the 20-mm or smaller tumors (16 of 59, 27%) than among the 21-30-mm tumors (12 of 93, 13%) (P = .033). They were also more common among well-differentiated tumors (seven of 12, 58%) than among moderately differentiated (20 of 124, 16%) and poorly differentiated (one of 10, 10%) tumors (P = .001). The prevalence of secondary signs differed significantly according to tumor size (53 [76%] of 70 ≤20-mm tumors vs 92 [99%] of 93 21-30-mm tumors) (P < .001). The prevalence of secondary signs was high among isoattenuating pancreatic cancers (14 [88%] of 16 ≤20-mm tumors vs all 12 [100%] 21-30-mm tumors). Most of the isoattenuating tumors seen at prediagnostic CT were hypoattenuating after 6 months (100% [four of four] during pancreatic phase, 71% [five of seven] during hepatic venous phase)., Conclusion: The prevalence of isoattenuating pancreatic cancers differed significantly according to tumor size and cellular differentiation. Most small isoattenuating pancreatic cancers showed secondary signs., Supplemental Material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11101133/-/DC1., (RSNA, 2011)