Eric E. Williamson

Intracranial Gadolinium Deposition after Contrast-enhanced MR Imaging

PURPOSE To determine if repeated intravenous exposures to gadolinium-based contrast agents (GBCAs) are associated with neuronal tissue deposition. MATERIALS AND METHODS In this institutional review board-approved single-center study, signal intensities from T1-weighted magnetic resonance (MR) images and postmortem neuronal tissue samples from 13 patients who underwent at least four GBCA-enhanced brain MR examinations between 2000 and 2014 (contrast group) were compared with those from 10 patients who did not receive GBCA (control group). Antemortem consent was obtained from all study participants. Neuronal tissues from the dentate nuclei, pons, globus pallidus, and thalamus of these 23 deceased patients were harvested and analyzed with inductively coupled plasma mass spectrometry (ICP-MS), transmission electron microscopy, and light microscopy to quantify, localize, and assess the effects of gadolinium deposition. Associations between cumulative gadolinium dose, changes in T1-weighted MR signal intensity, and ICP-MS-derived tissue gadolinium concentrations were examined by using the Spearman rank correlation coefficient (ρ). RESULTS Compared with neuronal tissues of control patients, all of which demonstrated undetectable levels of gadolinium, neuronal tissues of patients from the contrast group contained 0.1-58.8 μg gadolinium per gram of tissue, in a significant dose-dependent relationship that correlated with signal intensity changes on precontrast T1-weighted MR images (ρ = 0.49-0.93). All patients in the contrast group had relatively normal renal function at the time of MR examination. Gadolinium deposition in the capillary endothelium and neural interstitium was observed only in the contrast group. CONCLUSION Intravenous GBCA exposure is associated with neuronal tissue deposition in the setting of relatively normal renal function. Additional studies are needed to investigate the clinical significance of these findings and the generalizability to other GBCAs. Online supplemental material is available for this article.

Intravenous Contrast Material–induced Nephropathy: Causal or Coincident Phenomenon?

PURPOSE To determine the causal association and effect of intravenous iodinated contrast material exposure on the incidence of acute kidney injury (AKI), also known as contrast material-induced nephropathy (CIN). MATERIALS AND METHODS This retrospective study was approved by an institutional review board and was HIPAA compliant. Informed consent was waived. All contrast material-enhanced (contrast group) and unenhanced (noncontrast group) abdominal, pelvic, and thoracic CT scans from 2000 to 2010 were identified at a single facility. Scan recipients were sorted into low- (<1.5 mg/dL), medium- (1.5-2.0 mg/dL), and high-risk (>2.0 mg/dL) subgroups of presumed risk for CIN by using baseline serum creatinine (SCr) level. The incidence of AKI (SCr ≥ 0.5 mg/dL above baseline) was compared between contrast and noncontrast groups after propensity score adjustment by stratification, 1:1 matching, inverse weighting, and weighting by the odds methods to reduce intergroup selection bias. Counterfactual analysis was used to evaluate the causal relation between contrast material exposure and AKI by evaluating patients who underwent contrast-enhanced and unenhanced CT scans during the study period with the McNemar test. RESULTS A total of 157,140 scans among 53,439 unique patients associated with 1,510,001 SCr values were identified. AKI risk was not significantly different between contrast and noncontrast groups in any risk subgroup after propensity score adjustment by using reported risk factors of CIN (low risk: odds ratio [OR], 0.93; 95% confidence interval [CI]: 0.76, 1.13; P = .47; medium risk: odds ratio, 0.97; 95% CI: 0.81, 1.16; P = .76; high risk: OR, 0.91; 95% CI: 0.66, 1.24; P = .58). Counterfactual analysis revealed no significant difference in AKI incidence between enhanced and unenhanced CT scans in the same patient (McNemar test: χ(2) = 0.63, P = .43) (OR = 0.92; 95% CI: 0.75, 1.13; P = .46). CONCLUSION Following adjustment for presumed risk factors, the incidence of CIN was not significantly different from contrast material-independent AKI. These two phenomena were clinically indistinguishable with established SCr-defined criteria, suggesting that intravenous iodinated contrast media may not be the causative agent in diminished renal function after contrast material administration. SUPPLEMENTAL MATERIAL http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12121823/-/DC1.

Frequency of Acute Kidney Injury Following Intravenous Contrast Medium Administration: A Systematic Review and Meta-Analysis

PURPOSE To perform a systematic review and meta-analysis of controlled studies examining the incidence of acute kidney injury (AKI) and other outcomes in patients exposed to intravenous (i.v.) contrast medium compared with patients who underwent an imaging examination without contrast medium or were otherwise unexposed (control group). MATERIALS AND METHODS MEDLINE, EMBASE, Scopus, and the Cochrane Library were searched for all articles published through September 2011 that contained search terms related to nephrotoxicity following intravenous contrast medium administration. Two independent reviewers identified studies in which the incidence of AKI in patients exposed to i.v. contrast medium was directly compared with the incidence of AKI in unexposed patients through analysis of changes in serum creatinine level or estimated glomerular filtration rate 48-72 hours following imaging procedures or admission. Study characteristics and outcomes of AKI, dialysis, and mortality were extracted by using a standardized protocol. Relative risk (RR) was calculated by using random-effects models and was tested in subgroups of different patient comorbidities, contrast medium types, and AKI diagnostic criteria. RR results of less than 1.00 indicated that there was a higher incidence of these outcomes in the group that did not receive contrast medium (non-contrast medium group). RESULTS Of the 1489 studies originally identified, 13 nonrandomized studies (0.9%) representing 25,950 patients met inclusion criteria. In the group that received contrast medium (contrast medium group), risk of AKI (RR = 0.79; 95% confidence interval [CI]: 0.62, 1.02; P = .07), death (RR = 0.95; 95% CI: 0.55, 1.67; P = .87), and dialysis (RR = 0.88; 95% CI: 0.23, 3.43; P = .85) was similar, compared with the risk of AKI in the non-contrast medium group. This pattern was observed regardless of i.v. contrast medium type, diagnostic criteria for AKI, or whether patients had diabetes mellitus or renal insufficiency. CONCLUSION Controlled contrast medium-induced nephropathy studies demonstrate a similar incidence of AKI, dialysis, and death between the contrast medium group and control group. SUPPLEMENTAL MATERIAL http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12121460/-/DC1.

Risk of Intravenous Contrast Material–mediated Acute Kidney Injury: A Propensity Score–matched Study Stratified by Baseline-estimated Glomerular Filtration Rate

PURPOSE To determine the effect of baseline estimated glomerular filtration rate (eGFR) on the causal association between intravenous iodinated contrast material exposure and subsequent development of acute kidney injury (AKI) in propensity score-matched groups of patients who underwent contrast material-enhanced or unenhanced computed tomography (CT). MATERIALS AND METHODS This retrospective study was HIPAA compliant and institutional review board approved. All patients who underwent contrast-enhanced (contrast material group) or unenhanced (non-contrast material group) CT between 2000 and 2010 were identified and stratified according to baseline eGFR by using Kidney Disease Outcomes Quality Initiative cutoffs for chronic kidney disease into subgroups with eGFR of 90 or greater, 60-89, 30-59, and less than 30 mL/min/1.73 m(2). Propensity score generation and 1:1 matching of patients were performed in each eGFR subgroup. Incidence of AKI (serum creatinine [SCr] increase of ≥0.5 mg/dL [≥44.2 μmol/L] above baseline) was compared in the matched subgroups by using the Fisher exact test. RESULTS A total of 12 508 propensity score-matched patients with contrast-enhanced and unenhanced scans met all inclusion criteria. In this predominantly inpatient cohort, the incidence of AKI significantly increased with decreasing baseline eGFR (P < .0001). However, this incidence was not significantly different between contrast material and non-contrast material groups in any eGFR subgroup; for the subgroup with eGFR of 90 or greater (n = 1642), odds ratio (OR) was 0.91 (95% confidence interval [CI]: 0.38, 2.15), P = .82; for the subgroup with eGFR of 60-89 (n = 3870), OR was 1.03 (95% CI: 0.66, 1.60), P = .99; for the subgroup with eGFR of 30-59 (n = 5510), OR was 0.94 (95% CI: 0.76, 1.18), P = .65; and for the subgroup with eGFR of less than 30 mL/min/1.73 m(2) (n = 1486), OR was 0.97 (95% CI: 0.72, 1.30), P = .89. CONCLUSION Diminished eGFR is associated with an increased risk of SCr-defined AKI following CT examinations. However, the risk of AKI is independent of contrast material exposure, even in patients with eGFR of less than 30 mL/min/1.73 m(2).

Intravenous Contrast Material Exposure Is Not an Independent Risk Factor for Dialysis or Mortality

PURPOSE To determine the risk of emergent dialysis and short-term mortality following intravenous iodinated contrast material exposure. MATERIALS AND METHODS This single-center retrospective study was HIPAA compliant and institutional review board approved. All contrast material-enhanced (contrast group) and unenhanced (noncontrast group) abdominal, pelvic, and thoracic computed tomography scans from 2000-2010 were identified. Patients in the contrast and noncontrast groups were compared following propensity score-based 1:1 matching to reduce intergroup selection bias. Patients with preexisting diabetes mellitus, congestive heart failure, or chronic or acute renal failure were identified as high-risk patient subgroups for nephrotoxicity. The effects of contrast material exposure on the rate of acute kidney injury ( AKI acute kidney injury ) (serum creatinine level ≥ 0.5 mg/dL [44.2 μmol/L] above baseline within 24-72 hours of exposure) and dialysis or death within 30 days of exposure were determined by using odds ratios ( OR odds ratio s) and covariate-adjusted Cox proportional hazards models. Results were validated with a bootstrapped sensitivity analysis. RESULTS The 1:1 matching on the basis of the propensity score yielded a cohort of 21 346 patients (10 673 in the contrast group, 10 673 in the noncontrast group). Within this cohort, the risks of AKI acute kidney injury ( OR odds ratio , 0.94; 95% confidence interval [ CI confidence interval ]: 0.83, 1.07; P = .38), emergent dialysis ( OR odds ratio , 0.96; 95% CI confidence interval : 0.54, 1.60; P = .89), and 30-day mortality (hazard ratio [ HR hazard ratio ], 0.97; 95% CI confidence interval : 0.87, 1.06; P = .45) were not significantly different between the contrast group and the noncontrast group. Although patients who developed AKI acute kidney injury had higher rates of dialysis and mortality, contrast material exposure was not an independent risk factor for either outcome for dialysis ( OR odds ratio , 0.89; 95% CI confidence interval : 0.40, 2.01; P = .78) or for mortality ( HR hazard ratio , 1.03; 95% CI confidence interval : 0.82, 1.32; P = .63), even among patients with compromised renal function or predisposing comorbidities. CONCLUSION Intravenous contrast material administration was not associated with excess risk of AKI acute kidney injury , dialysis, or death, even among patients with comorbidities reported to predispose them to nephrotoxicity.

Chronic Oral Endothelin Type A Receptor Antagonism in Experimental Heart Failure

Endothelin-1 (ET-1) is a cardiovascular peptide that binds to two distinct receptors, ET(A) and ET(B), resulting in systemic and regional vasoconstriction, alteration in sodium excretion, mitogenesis, and release of other vasoactive peptides such as atrial natriuretic peptide (ANP). A role for ET-1 has been proposed in congestive heart failure (CHF) based on the increase in circulating ET-1 in this cardiovascular disease state. The present study determined the cardiorenal and endocrine responses to chronic selective oral ETA antagonism in experimental CHF. Two groups of conscious dogs underwent 21 days of pacing-induced CHF. These groups included a control untreated group (n = 6) and a group that received an orally active ET(A) receptor antagonist (A-127722, Abbott Pharmaceuticals, 5 mg/kg PO bid, n = 6). Each group was studied at baseline before the onset of CHF and after 14 and 21 days of CHF. Compared with the CHF control group, the ET(A) receptor antagonism group at 14 days of CHF showed lower mean arterial pressure and systemic vascular resistance. Similarly, ET(A) receptor antagonism markedly attenuated the increase in circulating ANP despite similar atrial pressures. At 21 days of CHF, ET(A) receptor antagonism lowered pulmonary artery pressure, pulmonary vascular resistance, and systemic vascular resistance in association with a higher cardiac output. Plasma ANP remained suppressed. Despite the lower mean arterial pressure and circulating ANP in the ET(A) receptor antagonist group, the absolute decrease in sodium excretion from baseline was less compared with the untreated CHF control group. The present investigation supports the conclusion that endogenous ET-1 participates in the systemic and pulmonary vasoconstriction, the elevation of ANP, and the sodium retention that characterize this model of experimental CHF, suggesting a potential therapeutic role for ET(A) receptor antagonism in CHF.

Assessing the adequacy of peripherally inserted central catheters for power injection of intravenous contrast agents for CT.

Purpose The purpose of this work was to determine the tolerance of silicone peripherally inserted central catheters (PICCs) of different sizes and lengths to power injection of contrast materials at flow rates suitable for CT studies. Method Fifty silicone PICCs in three single-lumen sizes (3 to 5F) and two double-lumen sizes (6 and 7F) were cut to two lengths (35 and 45 cm), and a uniform volume of 74% ioversol was injected into each at increasing rates of flow by a power injector. The flow rate, volume, and peak pressure were recorded for each injection. Results The respective tolerated flows for the 35 and 45 cm PICCs were 0.65 ml/s at 125 psi and 0.56 ml/s at 125 psi for the 3F catheters, 1.58 ml/s at 150 psi and 1.04 ml/s at 150 psi for the 4F catheters, 4.20 ml/s at 200 psi and 3.02 ml/s at 170 psi for the 5F catheters, 1.50 ml/s at 145 psi and 0.88 ml/s at 150 psi for the 6F catheters, and 9.52 ml/s at 350 psi and 8.78 ml/s at 330 psi for the 7F catheters. Conclusion The 3F catheters were unsuitable for power injection for CT studies because they could not accommodate adequate flow rates. The 4F single-lumen and 6F double-lumen catheters withstood flow rates that were marginally adequate for CT studies. The 5F single-lumen and 7F double-lumen PICCs tolerated peak flows and pressures well within the range necessary to allow power injection of contrast materials for CT studies. For each size of PICC, the 35 cm length withstood higher flow rates than the 45 cm length before failure.

Clinical Pharmacology, Uses, and Adverse Reactions of Iodinated Contrast Agents: A Primer for the Non-radiologist

Iodinated contrast agents have been in use since the 1950s to facilitate radiographic imaging modalities. Physicians in almost all specialties will either administer these agents or care for patients who have received these drugs. Different iodinated contrast agents vary greatly in their properties, uses, and toxic effects. Therefore, clinicians should be at least superficially familiar with the clinical pharmacology, administration, risks, and adverse effects associated with iodinated contrast agents. This primer offers the non-radiologist physician the opportunity to gain insight into the use of this class of drugs.

Prevalence and significance of incidental extracardiac findings at 64-multidetector coronary CTA

Introduction Computed tomography (CT) angiography of the coronaries has the ability to depict extracardiac lesions in the visualized thorax and upper abdomen. These incidental lesions can often present a challenge to physicians. Methods We performed a retrospective review of 100 consecutive patients referred for 64-multidetector CT coronary CT angiography performed on a 64-slice CT scanner. Two fellowship trained cardiac radiologists reviewed each study by consensus on a CT postprocessing workstation using commercially available software. Extracardiac CT findings (ECF) were classified as benign, indeterminate, or of clinical significance at the time of image evaluation. Benign findings were those considered to be of little clinical significance with no follow-up needed. Indeterminate findings were those deemed of potential clinical importance, requiring correlation of the patient history or a follow-up study. Clinically significant findings were those felt to be of definite clinical importance requiring immediate evaluation or intervention. Results The study cohort consisted of 68 males (68%) and 32 females (32%) with a mean (±standard deviation) age of 63.4±14.5 years and a range of 23 to 87 years. A total of 145 ECF were found in 67 patients (67%), 50 males and 17 females, with a mean age of 68.0±11.8 years and a range of 23 to 87 years. Of those, 107 (73.8%) were considered benign, 22 (15.2%) indeterminate, and 16 clinically significant findings (11.0%). By significance, a total of 107 benign ECF were found in 61 patients, 46 males and 15 females, with a mean age of 67.7±12.2 years and a range of 23 to 87 years. Only 22 ECF indeterminate findings were present, distributed in 21 patients, of which there were 17 males and 5 females, with a mean age of 68.5±13.9 and a range of 23 to 82 years. The 16 clinically significant ECF were distributed in 11 patients, all males, with a mean age of 68.0±8.8 and a range of 55 to 87 years. Conclusions The presence of ECF in our daily practice is frequent, and not limited to the identification of pulmonary nodules, and reinforces the notion that all the organs in the scan should be thoroughly and methodically evaluated.

Valsalva Sinus Aneurysms: Findings at CT and MR Imaging

Aneurysms of the Valsalva sinus (aortic sinus) can be congenital or acquired and are rare. They are more common among men than women and among Asians than other ethnic groups. Nonruptured aneurysms may be asymptomatic and incidentally discovered, or they may be symptomatic and manifest acutely with mass effect on adjacent cardiac structures. Ruptured Valsalva sinus aneurysms result in an aortocardiac shunt and may manifest as insidiously progressive congestive heart failure, severe acute chest pain with dyspnea, or, in extreme cases, cardiac arrest. Although both ruptured and nonruptured Valsalva sinus aneurysms may have potentially fatal complications, after treatment the prognosis is excellent. Thus, prompt and accurate diagnosis is critical. Most Valsalva sinus aneurysms are diagnosed on the basis of echocardiography, with or without angiography. However, both electrocardiographically gated computed tomography and magnetic resonance (MR) imaging can provide excellent anatomic depiction, and MR imaging can provide valuable functional information.