Performance of CT With Adrenal-Washout Protocol in Heterogeneous Adrenal Nodules: A Multiinstitutional Study.

BACKGROUND. CT with adrenal-washout protocol (hereafter, adrenal-protocol CT) is commonly performed to distinguish adrenal adenomas from other adrenal tumors. However, the technique's utility among heterogeneous nodules is not well established, and the optimal method for placing ROIs in heterogeneous nodules is not clearly defined. OBJECTIVE. The purpose of our study was to determine the diagnostic performance of adrenal-protocol CT to distinguish adenomas from nonadenomas among heterogeneous adrenal nodules and to compare this performance among different methods for ROI placement. METHODS. This retrospective study included 164 patients (mean age, 59.1 years; 61 men, 103 women) with a total of 164 heterogeneous adrenal nodules evaluated using adrenal-protocol CT at seven institutions. All nodules had an available pathologic reference standard. A single investigator at each institution evaluated the CT images. ROIs were placed on portal venous phase images using four ROI methods: standard ROI, which refers to a single large ROI in the nodule's center; high ROI, a single ROI on the nodule's highest-attenuation area; low ROI, a single ROI the on nodule's lowest-attenuation area; and average ROI, the mean of the three ROIs on the nodule's superior, middle, and inferior thirds using the approach for the standard ROI. ROIs were then placed in identical locations on unenhanced and delayed phase images. Absolute washout was determined for all methods. RESULTS. The nodules comprised 82 adenomas and 82 nonadenomas (36 pheochromocytomas, 20 metastases, 12 adrenocortical carcinomas, and 14 nodules with other pathologies). The mean nodule size was 4.5 ± 2.8 (SD) cm (range, 1.6-23.0 cm). Unenhanced CT attenuation of 10 HU or less exhibited sensitivity and specificity for adenoma of 22.0% and 96.3% for standard-ROI, 11.0% and 98.8% for high-ROI, 58.5% and 84.1% for low-ROI, and 30.5% and 97.6% for average-ROI methods. Adrenal-protocol CT overall (unenhanced attenuation ≤ 10 HU or absolute washout of ≥ 60%) exhibited sensitivity and specificity for adenoma of 57.3% and 84.1% for the standard-ROI method, 63.4% and 51.2% for the high-ROI method, 68.3% and 62.2% for the low-ROI method, and 59.8% and 85.4% for the average-ROI method. CONCLUSION. Adrenal-protocol CT has poor diagnostic performance for distinguishing adenomas from nonadenomas among heterogeneous adrenal nodules regardless of the method used for ROI placement. CLINICAL IMPACT. Adrenal-protocol CT has limited utility in the evaluation of heterogeneous adrenal nodules.

Imaging of pregnant and lactating patients with suspected adrenal disorders.

A high level of clinical suspicion is essential in the diagnosis and management of a suspected adrenal mass during pregnancy and the peripartum period. Timely recognition is important in order to improve fetal and maternal outcomes. Imaging is often performed to confirm a suspected adrenal lesion; however, increasing usage of diagnostic imaging during pregnancy and lactation has also increased awareness, concerns and confusion regarding the safety risks regarding fetal and maternal exposure to radiation and imaging intravenous contrast agents. This may lead to anxiety and avoidance of imaging examinations which can delay diagnosis and appropriate treatment. This article briefly reviews evidence-based recommended imaging modalities during pregnancy and the lactation period for the assessment of a suspected adrenal mass while recognizing that no examination should be withheld when the exam is necessary to confirm an important clinical suspicion. The imaging characteristics of the more common adrenal pathologies that may affect pregnant women are also discussed.

Prevalence of Malignancy in Adrenal Nodules With Heterogeneous Microscopic Fat on Chemical-Shift MRI: A Multiinstitutional Study.

BACKGROUND. Homogeneous microscopic fat within adrenal nodules on chemical-shift MRI (CS-MRI) is diagnostic of benign adrenal adenoma, but the clinical relevance of heterogeneous microscopic fat is not well established. OBJECTIVE. This study sought to determine the prevalence of malignancy in adrenal nodules with heterogeneous microscopic fat on dual-echo T1-weighted CS-MRI. METHODS. We performed a retrospective study of adult patients with adrenal nodules detected on MRI performed between August 2007 and November 2020 at seven institutions. Eligible nodules had a short-axis diameter of 10 mm or larger with heterogeneous microscopic fat (defined by an area of signal loss of < 80% on opposed-phase CS-MRI). Two radiologists from each center, blinded to reference standard results, determined the signal loss pattern (diffuse, two distinct parts, speckling pattern, central loss, or peripheral loss) within the nodules. The reference standard used was available for 283 nodules (pathology for 21 nodules, ≥ 1 year of imaging follow-up for 245, and ≥ 5 years of clinical follow-up for 17) in 282 patients (171 women and 111 men; mean age, 60 ± 12 [SD] years); 30% (86/282) patients had prior malignancy. RESULTS. The mean long-axis diameter was 18.7 ± 7.9 mm (range, 10-80 mm). No malignant nodules were found in patients without prior cancer (0/197; 95% CI, 0-1.5%). Four of the 86 patients with prior malignancy (hepatocellular carcinoma [HCC], renal cell carcinoma [RCC], lung cancer, or both colon cancer and RCC) (4.7%; 95% CI, 1.3-11.5%) had metastatic nodules. Detected patterns were diffuse heterogeneous signal loss (40% [114/283]), speckling (28% [80/283]), two distinct parts (18% [51/283]), central loss (9% [26/283]), and peripheral loss (4% [12/283]). Two metastases from HCC and RCC showed diffuse heterogeneous signal loss. Lung cancer metastasis manifested as two distinct parts, and the metastasis in the patient with both colon cancer and RCC showed peripheral signal loss. CONCLUSION. Presence of heterogeneous microscopic fat in adrenal nodules on CS-MRI indicates a high likelihood of benignancy, particularly in patients without prior cancer. This finding is also commonly benign in patients with cancer; however, caution is warranted when primary malignancies may contain fat or if the morphologic pattern of signal loss may indicate a collision tumor. CLINICAL IMPACT. In the absence of prior cancer, adrenal nodules with heterogeneous microscopic fat do not require additional imaging evaluation.

Adrenal Neoplasms: Lessons from Adrenal Multidisciplinary Tumor Boards.

The radiologic diagnosis of adrenal disease can be challenging in settings of atypical presentations, mimics of benign and malignant adrenal masses, and rare adrenal anomalies. Misdiagnosis may lead to suboptimal management and adverse outcomes. Adrenal adenoma is the most common benign adrenal tumor that arises from the cortex, whereas adrenocortical carcinoma (ACC) is a rare malignant tumor of the cortex. Adrenal cyst and myelolipoma are other benign adrenal lesions and are characterized by their fluid and fat content, respectively. Pheochromocytoma is a rare neuroendocrine tumor of the adrenal medulla. Metastases to the adrenal glands are the most common malignant adrenal tumors. While many of these masses have classic imaging appearances, considerable overlap exists between benign and malignant lesions and can pose a diagnostic challenge. Atypical adrenal adenomas include those that are lipid poor; contain macroscopic fat, hemorrhage, and/or iron; are heterogeneous and/or large; and demonstrate growth. Heterogeneous adrenal adenomas may mimic ACC, metastasis, or pheochromocytoma, particularly when they are 4 cm or larger, whereas smaller versions of ACC, metastasis, and pheochromocytoma and those with washout greater than 60% may mimic adenoma. Because of its nonenhanced CT attenuation of less than or equal to 10 HU, a lipid-rich adrenal adenoma may be mimicked by a benign adrenal cyst, or it may be mimicked by a tumor with central cystic and/or necrotic change such as ACC, pheochromocytoma, or metastasis. Rare adrenal tumors such as hemangioma, ganglioneuroma, and oncocytoma also may mimic adrenal adenoma, ACC, metastasis, and pheochromocytoma. The authors describe cases of adrenal neoplasms that they have encountered in clinical practice and presented to adrenal multidisciplinary tumor boards. Key lessons to aid in diagnosis and further guide appropriate management are provided. © RSNA, 2023 Online supplemental material is available for this article. Quiz questions for this article are available through the Online Learning Center.

Preoperative Prostate MRI Predictors of Urinary Continence Following Radical Prostatectomy.

Background Urinary continence after radical prostatectomy (RP) is an important determinant of patient quality of life. Anatomic measures at prostate MRI have been previously associated with continence outcomes, but their predictive ability and interrater agreement are unclear in comprehensive clinical models. Purpose To evaluate the predictive ability and interrater agreement of MRI-based anatomic measurements of post-RP continence when combined with clinical multivariable models. Materials and Methods In this retrospective cohort study, continence outcomes were evaluated in men who underwent RP from August 2015 to October 2019. Preoperative MRI-based anatomic measures were obtained retrospectively by four abdominal radiologists. Before participation, these radiologists completed measure-specific training. Logistic regression models were developed with clinical variables alone, MRI variables alone, and combined variables for predicting continence at 3, 6, and 12 months after RP; some patient data were missing at each time point. Interrater agreement of MRI variables was assessed by using intraclass correlation coefficients (ICCs). Results A total of 586 men were included (mean age ± standard deviation: 63 years ± 7). The proportion of patients with incontinence was 0.2% (one of 589) at baseline, 27% (145 of 529) at 3 months, 14% (63 of 465) at 6 months, and 9% (37 of 425) at 12 months. Longer coronal membranous urethra length (MUL) improved the odds of post-RP continence at all time points (odds ratio per 1 mm: 0.86 [95% CI: 0.80, 0.93], P < .001; 0.86 [95% CI: 0.78, 0.95], P = .003; and 0.79 [95% CI: 0.67, 0.91], P = .002, respectively) in models that incorporated both clinical and MRI predictors. No other MRI variables were predictive. Age and baseline urinary function score were the only other predictive clinical variables at every time point. Interrater agreement was moderate (ICC, 0.62) for MUL among readers with measure-specific prostate MRI training and poor among those without the training (ICC, 0.38). Conclusion Preoperative MRI-measured coronal membranous urethra length was an independent predictor of urinary continence after prostatectomy. © RSNA, 2022 Online supplemental material is available for this article.

Incidental Adrenal Nodules in Patients Without Known Malignancy: Prevalence of Malignancy and Utility of Washout CT for Characterization-A Multiinstitutional Study.

BACKGROUND. Washout CT is commonly used to evaluate indeterminate adrenal nodules, although its diagnostic performance is poorly established in true adrenal incidentalomas. OBJECTIVE. The purpose of this study was to compare, in patients without a known malignancy history, the prevalence of malignancy for incidental adrenal nodules with unenhanced attenuation more than 10 HU that do and do not show absolute washout of 60% or more, thereby determining the diagnostic performance of washout CT for differentiating benign from malignant incidental adrenal nodules. METHODS. This retrospective six-institution study included 299 patients (mean age, 57.3 years; 180 women, 119 men) without known malignancy or suspicion for functioning adrenal tumor who underwent washout CT, which showed a total of 336 adrenal nodules with a short-axis diameter of 1 cm or more, homogeneity, and unenhanced attenuation over 10 HU. The date of the first CT ranged across institutions from November 1, 2003, to January 1, 2017. Washout was determined for all nodules. Reference standard was pathology (n = 54), imaging follow-up (≥ 1 year) (n = 269), or clinical follow-up (≥ 5 years) (n = 13). RESULTS. Prevalence of malignancy among all nodules, nodules less than 4 cm, and nodules 4 cm or more was 1.5% (5/336; 95% CI, 0.5-3.4%), 0.3% (1/317; 95% CI, 0.0-1.7%), and 21.1% (4/19; 95% CI, 6.1-45.6%), respectively. Prevalence of malignancy was not significantly different for nodules smaller than 4 cm with (0% [0/241]; 95% CI, 0.0-1.2%) and without (1.3% [1/76]; 95% CI, 0.0-7.1%) washout of 60% or more (p = .08) or for nodules 4 cm or larger with (16.7% [1/6]; 95% CI, 0.4-64.1%) and without (23.1% [3/13]; 95% CI, 5.0-53.8%) washout of 60% or more (p = .75). Washout of 60% or more was observed in 75.5% (243/322; 95% CI, 70.4-80.1%) of benign nodules (excluding pheochromocytomas), 20.0% (1/5; 95% CI, 0.5-71.6%) of malignant nodules, and 33.3% (3/9; 95% CI, 7.5-70.1%) of pheochromocytomas. For differentiating benign nodules from malignant nodules and pheochromocytomas, washout of 60% or more had 77.5% sensitivity, 70.0% specificity, 98.8% PPV, and 9.2% NPV among nodules smaller than 4 cm. CONCLUSION. Prevalence of malignancy is low among incidental homogeneous adrenal nodules smaller than 4 cm with unenhanced attenuation more than 10 HU and does not significantly differ between those with and without washout of 60% or more; wash-out of 60% or more has suboptimal performance for characterizing nodules as benign. CLINICAL IMPACT. Washout CT has limited utility in evaluating incidental adrenal nodules in patients without known malignancy.

Effect of iodinated contrast material on post-operative eGFR when administered during renal mass ablation.

OBJECTIVE: To evaluate the effect of intravenous iodinated contrast on estimated glomerular filtration rate (eGFR) when administered immediately after thermal ablation of clinically localized T1a (cT1a) renal cell carcinoma (RCC). METHODS: This HIPAA-compliant, dual-center retrospective study was performed under a waiver of informed consent. Three hundred forty-two consecutive patients with cT1a biopsy-proven RCC were treated with percutaneous ablation between January 2010 and December 2017. Immediate post-ablation contrast-enhanced CT was the routine standard of care at one institution (contrast group), but not the other (control group). One-month pre- and 6-month post-ablation eGFR were compared using the Wilcoxon signed-rank test or the Kruskal-Wallis test. Multivariate linear regression was used to determine the effect of contrast on eGFR. A 1:1 propensity score matching was performed for all patients with a logistic model using patient, tumor, and procedural covariates. RESULTS: In total, 246 patients (158 M; median age 69 years, IQR 62-74) were included. Median tumor diameter (2.4 vs 2.5, p = 0.23) and RENAL nephrometry scores (6 vs 6, p = 0.92), surrogates for ablation zone size, were similar. Baseline kidney function was similar for the control and contrast groups, respectively (median eGFR: 70 vs 74 mL/min/1.73 m2, p = 0.29). There was an expected mild decline in eGFR after ablation (control: 70 vs 60 mL/min/1.73 m2, p < 0.001; contrast: 75 vs 71 mL/min/1.73 m2, p = 0.001). Intravenous iodinated contrast was not associated with a decline in eGFR on multivariate linear regression (1.91, 95% CI - 3.43-7.24, p = 0.46) or 1:1 propensity score-matched model (- 0.33, 95% CI - 6.81-6.15, p = 0.92). CONCLUSION: Intravenous iodinated contrast administered during ablation of cT1a RCC has no effect on eGFR. KEY POINTS: • Intravenous iodinated contrast administered during thermal ablation of clinically localized T1a renal cell carcinoma has no effect on kidney function. • Thermal ablation of clinically localized T1a renal cell carcinoma results in a mild decline in kidney function. • A decline in kidney function is similar for radiofrequency and microwave ablation of clinically localized T1a renal cell carcinoma.

Retrospective Cohort Study of 1947 Thyroid Nodules: A Comparison of the 2017 American College of Radiology TI-RADS and the 2015 American Thyroid Association Classifications.

OBJECTIVE. The objective of our study was to compare diagnostic accuracy and reliability of the 2017 American College of Radiology (ACR) Thyroid Imaging Reporting and Data System (TI-RADS) and 2015 American Thyroid Association (ATA) classifications for thyroid nodules. MATERIALS AND METHODS. This study was a retrospective cohort study of 1947 consecutive thyroid nodules sampled with fine-needle aspiration (FNA) from 2007 to 2016. Reviewers assigned TI-RADS scores to all nodules while blinded to clinical outcome and histologic diagnosis and compared TI-RADS scores with nodule-specific ATA scores from the same cohort. Five blinded radiologists independently assigned TI-RADS scores to a subset of 151 nodules (interrater agreement). The primary outcome was a comparison of the diagnostic accuracy of the TI-RADS and ATA classifications using ROC curve analysis. The reference standard was cytopathologic diagnosis according to the Bethesda system. Interrater agreement was determined using intraclass correlation (ICC) and kappa statistics. RESULTS. Of 1947 sampled thyroid nodules, 31.8% (n = 620) met TI-RADS criteria for FNA, 28.0% (n = 545) met TI-RADS criteria for follow-up, and 40.2% (n = 782) met TIRADS criteria to be ignored. Applying the 2015 ATA criteria resulted in recommendations of immediate FNA procedures for more nodules than applying the 2017 TI-RADS (ATA vs TIRADS: 62.3% [1213/1947] vs 31.8% [620/1947], p < 0.0001). Diagnostic accuracies (AUCs: TI-RADS score, 0.684 [95% CI, 0.644-0.724]; ATA, 0.686 [95% CI, 0.646-0.725]) and false-negative rates (TI-RADS, 2.2% [43/1947]; ATA, 2.4% [47/1947]) for the two classifications were similar (p = 0.75). Overall interrater agreement was fair for both (ICCs: TI-RADS, 0.437 [95% CI, 0.357-0.520]; ATA classification, 0.460 [95% CI, 0.391-0.533]). CONCLUSION. The 2017 ACR TI-RADS and 2015 ATA classifications have similar diagnostic accuracies and interrater agreement, but TI-RADS results in fewer nodules being recommended for immediate FNAs and more nodules being recommended for imaging surveillance.

Age, Gender and R.E.N.A.L. Nephrometry Score do not Improve the Accuracy of a Risk Stratification Algorithm Based on Biopsy and Mass Size for Assigning Surveillance versus Treatment of Renal Tumors.

PURPOSE: A previously published risk stratification algorithm based on renal mass biopsy and radiographic mass size was useful to designate surveillance vs the need for immediate treatment of small renal masses. Nonetheless, there were some incorrect assignments, most notably when renal mass biopsy indicated low risk malignancy but final pathology revealed high risk malignancy. We studied other factors that might improve the accuracy of this algorithm. MATERIALS AND METHODS: For 202 clinically localized small renal masses in a total of 200 patients with available R.E.N.A.L. (radius, exophytic/endophytic, nearness of tumor to collecting system or sinus, anterior/posterior, hilar tumor touching main renal artery or vein and location relative to polar lines) nephrometry score, preoperative renal mass biopsy and final pathology we assessed the accuracy of management assignment (surveillance vs treatment) based on the previously published risk stratification algorithm as confirmed by final pathology. Logistic regression was used to determine whether other factors (age, gender, R.E.N.A.L. score, R.E.N.A.L. score components and nomograms based on R.E.N.A.L. score) could improve assignment. RESULTS: Of the 202 small renal masses 53 (26%) were assigned to surveillance and 149 (74%) were assigned to treatment by the risk stratification algorithm. Of the 53 lesions assigned to surveillance 25 (47%) had benign/favorable renal mass biopsy histology while in 28 (53%) intermediate renal mass biopsy histology showed a mass size less than 2 cm. Nine of these 53 masses (17%) were incorrectly assigned to surveillance in that final pathology indicated the need for treatment (ie intermediate histology and a mass greater than 2 cm or unfavorable histology). Final pathology confirmed a correct assignment in all 149 masses assigned to treatment. None of the additional parameters assessed improved assignment with statistical significance. CONCLUSIONS: Age, gender, R.E.N.A.L. nephrometry score, R.E.N.A.L. score components and nomograms or combinations of these factors do not improve the predictive performance of a small renal mass management risk stratification algorithm based on renal mass biopsy and radiographic mass size.

Treatment Response Assessment for Bladder Cancer on CT Based on Computerized Volume Analysis, World Health Organization Criteria, and RECIST.

OBJECTIVE: The purpose of this study was to evaluate the accuracy of our autoinitialized cascaded level set 3D segmentation system as compared with the World Health Organization (WHO) criteria and the Response Evaluation Criteria In Solid Tumors (RECIST) for estimation of treatment response of bladder cancer in CT urography. MATERIALS AND METHODS: CT urograms before and after neoadjuvant chemo-therapy treatment were collected from 18 patients with muscle-invasive localized or locally advanced bladder cancers. The disease stage as determined on pathologic samples at cystectomy after chemotherapy was considered as reference standard of treatment response. Two radiologists measured the longest diameter and its perpendicular on the pre- and posttreatment scans. Full 3D contours for all tumors were manually outlined by one radiologist. The autoinitialized cascaded level set method was used to automatically extract 3D tumor boundary. The prediction accuracy of pT0 disease (complete response) at cystectomy was estimated by the manual, autoinitialized cascaded level set, WHO, and RECIST methods on the basis of the AUC. RESULTS: The AUC for prediction of pT0 disease at cystectomy was 0.78 ± 0.11 for autoinitialized cascaded level set compared with 0.82 ± 0.10 for manual segmentation. The difference did not reach statistical significance (p = 0.67). The AUCs using RECIST criteria were 0.62 ± 0.16 and 0.71 ± 0.12 for the two radiologists, both lower than those of the two 3D methods. The AUCs using WHO criteria were 0.56 ± 0.15 and 0.60 ± 0.13 and thus were lower than all other methods. CONCLUSION: The pre- and posttreatment 3D volume change estimates obtained by the radiologist's manual outlines and the autoinitialized cascaded level set segmentation were more accurate for irregularly shaped tumors than were those based on RECIST and WHO criteria.

Pediatric adrenocortical neoplasms: can imaging reliably discriminate adenomas from carcinomas?

BACKGROUND: There is a paucity of literature describing and comparing the imaging features of adrenocortical adenomas and carcinomas in children and adolescents. OBJECTIVE: To document the CT and MRI features of adrenocortical neoplasms in a pediatric population and to determine whether imaging findings (other than metastatic disease) can distinguish adenomas from carcinomas. MATERIALS AND METHODS: We searched institutional medical records to identify pediatric patients with adrenocortical neoplasms. Pre-treatment CT and MRI examinations were reviewed by two radiologists in consensus, and pertinent imaging findings were documented. We also recorded relevant histopathological, demographic, clinical follow-up and survival data. We used the Student's t-test and Wilcoxon rank sum test to compare parametric and nonparametric continuous data, and the Fisher exact test to compare proportions. We used receiver operating characteristic (ROC) curve analyses to evaluate the diagnostic performances of tumor diameter and volume for discriminating carcinoma from adenoma. A P-value ≤0.05 was considered statistically significant. RESULTS: Among the adrenocortical lesions, 9 were adenomas, 15 were carcinomas, and 1 was of uncertain malignant potential. There were no differences in mean age, gender or sidedness between adenomas and carcinomas. Carcinomas were significantly larger than adenomas based on mean estimated volume (581 ml, range 16-2,101 vs. 54 ml, range 3-197 ml; P-value = 0.003; ROC area under the curve = 0.92) and mean maximum transverse plane diameter (9.9 cm, range 3.0-14.9 vs. 4.4 cm, range 1.9-8.2 cm; P-value = 0.0001; ROC area under the curve = 0.92). Carcinomas also were more heterogeneous than adenomas on post-contrast imaging (13/14 vs. 2/9; odds ratio [OR] = 45.5; P-value = 0.001). Six of 13 carcinomas and 1 of 8 adenomas contained calcification at CT (OR = 6.0; P-value = 0.17). Seven of 15 children with carcinomas exhibited metastatic disease at diagnosis, and three had inferior vena cava invasion. Median survival for carcinomas was 27 months. CONCLUSION: In our experience, pediatric adrenocortical carcinomas are larger, more heterogeneous, and more often calcified than adenomas, although there is overlap in their imaging appearances.

Matched within-patient cohort study of transient arterial phase respiratory motion-related artifact in MR imaging of the liver: gadoxetate disodium versus gadobenate dimeglumine.

PURPOSE: To compare frequency and severity of arterial phase respiratory motion-related artifact following gadoxetate disodium and gadobenate dimeglumine in matched patients administered both contrast media at different times. MATERIALS AND METHODS: Institutional review board approval was obtained, with patient consent waived, for this retrospective, HIPAA-compliant study. Ninety patients underwent gadobenate dimeglumine-enhanced abdominal magnetic resonance (MR) followed by gadoxetate disodium-enhanced abdominal MR and were matched to 90 patients who were administered the same contrast media in reverse order (180 patients). Matching was based on length of time between paired examinations. Gadobenate dimeglumine dose was weight based (0.1 mmol per kilogram body weight). Gadoxetate disodium dose was typically fixed (10 or 20 mL [off label]). Three readers blinded to contrast agent assigned a respiratory motion-related artifact score (1 [none] to 5 [nondiagnostic]) for nonenhanced, arterial, venous, and late dynamic phases. Frequency of greater new arterial phase respiratory motion-related artifact in each within-patient pair and aggregate rate of new severe transient arterial phase respiratory motion-related artifact (scores ≤ 2, nonenhanced and venous and/or late dynamic phases; ≥ 4, arterial phase) were compared (McNemar test). RESULTS: For groups 1 and 2, respectively, mean dose (gadoxetate disodium, 16.6 mL vs 16.6 mL, P = .99; gadobenate dimeglumine, 18.0 mL vs 17.8 mL, P = .77) and mean time between examinations (191 days vs 191 days, P = .99) were not significantly different between matched populations. Gadoxetate disodium was associated with significantly higher incidence of new arterial phase respiratory motion-related artifact compared with gadobenate dimeglumine (39% vs 10%, P < .0001) and of new severe transient arterial phase respiratory motion-related artifact (18% vs 2%, P < .0001) in patients administered both agents at different times. CONCLUSION: Fixed off-label dose (10 or 20 mL) of gadoxetate disodium is associated with arterial phase respiratory motion-related artifact that is sometimes severe and occurs significantly more often than after gadobenate dimeglumine in patients who received both contrast media.

CT imaging characteristics of oncocytic adrenal neoplasms (OANs): comparison with adrenocortical carcinomas.

OBJECTIVE: Oncocytic adrenal neoplasms (OANs) are rare, but are an important subtype of adrenal tumors that is being diagnosed with increasing frequency. Unfortunately, the imaging characteristics of this tumor have not been well described. Our purpose was to identify CT features to differentiate OANs from adrenocortical carcinomas (ACC). MATERIALS AND METHODS: From 1991 to 2012, 18 patients with OANs were identified from our institution's pathology database. Twelve had CT examinations available for review. CT characteristics of five benign and seven malignant OANs were reviewed by two abdominal radiologists, and compared to ACC (n = 10). Morphologic characteristics and density measurements were recorded for each imaging phase. Absolute contrast washout was calculated and compared. RESULTS: Benign OANs were smaller [mean size 3.7 cm (range 2.6-5.3)] and more homogeneous than malignant OANs and demonstrated greater washout [mean washout percentage 72.3% (range 61-88)]. Malignant OANs demonstrated features similar to ACCs, including size [mean 9.4 cm (range 5.2-9.8)] and internal necrosis (n = 6). Mean enhancement washout percentage for malignant OANs was 12% (range -8 to 32). CONCLUSION: Benign OANs (oncocytomas) may be distinguished from lipid-rich adenomas on non-contrast CT but may be indistinguishable from lipid-poor adenomas. Malignant oncocytic neoplasms can demonstrate features similar to ACCs, including larger size, internal necrosis, and lower percentage enhancement washout.

Variability in computed tomography diameter measurements of solid renal masses.

PURPOSE: To determine whether the frequency of intra-observer measurement discrepancies ≥5 mm for solid renal masses varies by renal mass characteristics and CT contrast phase. MATERIALS AND METHODS: This HIPAA-compliant retrospective study was approved by our IRB. We selected single CT images performed during the nephrographic phase (NP) of renal enhancement in 97 patients, each with a single solid renal mass. Mass location, margin, heterogeneity, and growth pattern were assessed. Six readers measured each mass on two occasions >3 weeks apart. Readers also measured the masses on images in 50 patients who had corticomedullary phase (CMP) images obtained during the same study. Results were assessed using Chi-square/Fisher's exact and Wilcoxon Signed Rank tests, and logistic regression analyses. RESULTS: For NP to NP comparisons, intra-reader measurement differences ≥5 mm were seen for 3.7% (17/463) of masses <4 cm, but increased to 16.8% (20/119) for masses >4 cm (p < 0.0001). Masses with poorly defined margins (15.9% [22/138] vs. 3.4% [15/444] for well-defined margins, p < 0.0001) and heterogeneity (15.3% [22/144], vs. 5.0% [14/282] for minimally heterogeneous, vs. 0.6% [1/156] for homogeneous, p < 0.0001), were more frequently associated with measurement differences ≥5 mm. Differences ≥5 mm were more frequent when only CMP images were utilized (14% [42/299]), or when CMP images were compared with NP images (26% [77/299]). CONCLUSIONS: A ≥5 mm intra-reader variation in measured size of solid renal masses <4 cm is uncommon for NP to NP comparisons. Variation increases when masses are ≥4 cm, poorly defined, or heterogeneous; or when CMP images are utilized.

Contrast material-induced nephrotoxicity and intravenous low-osmolality iodinated contrast material.

PURPOSE: To determine whether intravenous low-osmolality iodinated contrast material is associated with post-computed tomography (CT) acute kidney injury (AKI). MATERIALS AND METHODS: Institutional review board approval was obtained and patient consent waived for this HIPAA-compliant retrospective study. CT examinations performed over a 10-year period in adult inpatients with sufficient serum creatinine (SCr) data were identified. A one-to-one propensity-matched matched cohort analysis with multivariate analysis of effects was performed with post-CT AKI as the primary outcome measure (10,121 unenhanced and 10,121 intravenous contrast-enhanced CT examinations in 20,242 patients). Propensity matching was performed with respect to likelihood of patient receiving intravenous contrast material (36 tested covariates). The primary endpoint was post-CT AKI by using Acute Kidney Injury Network SCr criteria; the secondary endpoint was post-CT AKI by using traditional SCr criteria for contrast material-induced nephrotoxicity (CIN; SCr increase ≥0.5 mg/dL [44.20 µmol/L] or ≥25%). Multivariate subgroup threshold analysis was performed (SCr <1.5 [<132.60 µmol/L]; ≥1.5 to ≥2.0 mg/dL [≥132.60 to ≥176.80 µmol/L]) and adjusted for assigned propensity scores. RESULTS: Intravenous low-osmolality iodinated contrast material had a significant effect on the development of post-CT AKI for patients with pre-CT SCr levels of 1.6 mg/dL (141.44 µmol/L) or greater (odds ratio, 1.45; 95% confidence interval [CI]: 1.11, 1.89;P = .007). This effect strengthened as pre-CT SCr increased. Patients with stable SCr less than 1.5 mg/dL (132.60 µmol/L) were not at risk for developing CIN (P = .25, power > 95%). Both endpoints demonstrated similar results (eg, SCr ≥1.6 mg/dL [141.44 µmol/L] by using traditional CIN criteria: odds ratio, 1.64; 95% CI: 1.18, 2.28; P = .003). Post-CT AKI was prevalent in both the unenhanced and contrast-enhanced CT subgroups, and it increased with increases in pre-CT SCr. Many risk factors contributed to development of post-CT AKI, regardless of iodinated contrast material. CONCLUSION: Intravenous low-osmolality iodinated contrast material is a nephrotoxic risk factor, but not in patients with a stable SCr level less than 1.5 mg/dL. Many factors other than contrast material can affect post-CT AKI rates.

Comparison of acute transient dyspnea after intravenous administration of gadoxetate disodium and gadobenate dimeglumine: effect on arterial phase image quality.

PURPOSE: To determine whether acute transient dyspnea and/or arterial phase image degradation occurs more or less often after intravenous administration of gadoxetate disodium than with intravenous administration of gadobenate dimeglumine. MATERIALS AND METHODS: Institutional review board approval and patient consent were obtained for this prospective observational study. One hundred ninety-eight gadolinium-based contrast media administrations (99 with gadoxetate disodium [10 mL, n = 97; 8 mL, n = 1; 16 mL, n = 1] and 99 with gadobenate dimeglumine [0.1 mmol per kilogram of body weight, maximum dose, 20 mL]) for hepatobiliary indications were assessed in 192 patients. Subjective patient complaints were assessed. Objective respiratory motion degradation on T1-weighted precontrast and dynamic postcontrast (arterial, venous, or late dynamic or extracellular) magnetic resonance (MR) imaging datasets were independently assessed in a randomized, blinded fashion by five readers using a five-point scale, with mean scores of 4 or greater indicating severe motion. Comparisons between agents were made by using χ(2) or Fisher exact test, where appropriate. RESULTS: Significantly more patient complaints of acute transient dyspnea occurred after gadoxetate disodium administration than gadobenate dimeglumine (14% [14 of 99] vs 5% [five of 99], P = .05). There were significantly more severely degraded arterial phase data sets for gadoxetate disodium than for gadobenate dimeglumine for both the general population (17% [17 of 99] vs 2% [two of 99], P = .0007) and the subpopulation with cirrhosis (19% [14 of 72] vs 3% [one of 37], P = .02). This effect did not extend to venous (1% [one of 99] vs 2% [two of 99], P > .99 [overall population]) or late dynamic or extracellular (2% [two of 99] vs 0% [zero of 99], P = .5 [overall population]) phases. No patient required treatment for self-limited dyspnea. CONCLUSION: Intravenous gadoxetate disodium can result in acute self-limiting dyspnea that can have a deleterious effect on arterial phase MR image quality and occurs significantly more often than with intravenous gadobenate dimeglumine.

Can established CT attenuation and washout criteria for adrenal adenoma accurately exclude pheochromocytoma?

OBJECTIVE: The purpose of this article is to determine the proportion of pheochromocytomas that mimic adrenal adenoma using established CT washout and attenuation criteria. MATERIALS AND METHODS: The CT characteristics of pheochromocytomas confirmed by histologic analysis (n = 46) and (131)I-metaiodobenzylguanidine (n = 1) were compared with those of 98 adrenal adenomas (negative plasma and urinary metanephrines or catecholamines, and one or more of the following characteristics: unenhanced attenuation ≤ 10 HU, absolute washout ≥ 60%, and relative washout ≥ 40%). CT numbers were measured in all available phases (unenhanced [n = 37], 1-minute contrast enhanced [n = 46], and delayed contrast enhanced [n = 43]) using a region of interest that encompassed the majority of the mass. Absolute washout, relative washout, and degree of enhancement (1-minute minus unenhanced) were calculated. Mass size and heterogeneity were recorded and compared using the Student t test and a chi-square test, respectively. RESULTS: Twenty-four of 47 (51%) pheochromocytomas were imaged with a triphasic examination using a 15-minute delay. Eight of 24 (33%) met relative (6/24 [25%]) or absolute (7/24 [29%]) washout criteria for the diagnosis of a lipid-poor adenoma. Four of these (50% [4/8]) were homogeneous on all three phases. None of the pheochromocytomas had an unenhanced attenuation of 10 HU or less. Pheochromocytomas were significantly larger than adrenal adenomas (mean diameter, 3.9 cm [range, 0.6-14 cm] vs 2.0 cm [range, 0.8-3.9 cm]; p < 0.0001) and were significantly less likely to be homogeneous (15/47 [32%] vs 95/98 [97%]; p < 0.0001), but there was overlap. CONCLUSION: A substantial minority of pheochromocytomas have absolute or relative washout characteristics that overlap with those of lipid-poor adenomas.

Differentiation of papillary renal cell carcinoma subtypes on CT and MRI.

OBJECTIVE: The objective of our study was to determine the frequency of atypical papillary renal cell carcinomas (RCCs) and identify imaging differences between type 1 and type 2 papillary RCCs once atypical papillary RCC tumors have been excluded. MATERIALS AND METHODS: Eighty-two papillary RCC tumors were classified at pathology as type 1, type 2, or atypical. The CT and MRI examinations of these tumors were reviewed. Imaging features such as tumor size, margins, heterogeneity, and enhancement were assessed and the findings in type 1 and type 2 tumors were compared. RESULTS: There were 43 type 1 and 13 type 2 tumors. Atypical histologic features (i.e., tumors containing both type 1 and type 2 components, clear cells, or components with atypically high nuclear grade [in type 1 tumors] or low nuclear grade [in type 2 tumors]) were seen in 26 tumors. On CT, type 2 tumors more commonly had infiltrative margins (p = 0.05) and were more likely to have calcifications (p = 0.04) than type 1 tumors, although these features were seen in all tumor types. Type 2 tumors were also more heterogeneous than type 1 tumors (p = 0.04). On CT, 11 papillary RCCs showed enhancement of less than 20 HU, seven of which showed enhancement of less than 10 HU. On MRI, all tumors showed enhancement on subtraction images. CONCLUSION: Nearly one third of papillary RCCs in our patient population had atypical features at histology. On CT and MRI, there are some significant differences in imaging features between type 1 and type 2 tumors; however, substantial overlap precludes categorization on a per-patient basis. On CT, many papillary RCCs do not enhance, indicating that assessment of enhancement alone is insufficient for differentiating papillary RCCs from hyperdense cysts.