Mutagenicity assessment of two potential impurities in preparations of 5-amino-2,4,6 triiodoisophthalic acid, a key intermediate in the synthesis of the iodinated contrast agent iopamidol.

5-Aminoisophthalic acid and 5-nitroisophthalic acid (5-NIPA) are potential impurities in preparations of 5-amino-2,4,6-triiodoisophthalic acid, which is a key intermediate in the synthesis of the iodinated contrast agent iopamidol. We have studied their mutagenicity in silico (quantitative structure-activity relationships, QSAR) and by the bacterial reverse mutation assay (Ames test). First, the compounds were screened with the tools Derek Nexus™ and Leadscope®. Both compounds were flagged as potentially mutagenic (class 3 under ICH M7). However, contrary to the in silico prediction, neither chemical was mutagenic in the Ames test (plate incorporation method) with or without S9 metabolic activation.

Improving pulmonary perfusion assessment by dynamic contrast-enhanced computed tomography in an experimental lung injury model.

Pulmonary perfusion has been poorly characterized in acute respiratory distress syndrome (ARDS). Optimizing protocols to measure pulmonary blood flow (PBF) via dynamic contrast-enhanced (DCE) computed tomography (CT) could improve understanding of how ARDS alters pulmonary perfusion. In this study, comparative evaluations of injection protocols and tracer-kinetic analysis models were performed based on DCE-CT data measured in ventilated pigs with and without lung injury. Ten Yorkshire pigs (five with lung injury, five healthy) were anesthetized, intubated, and mechanically ventilated; lung injury was induced by bronchial hydrochloric acid instillation. Each DCE-CT scan was obtained during a 30-s end-expiratory breath-hold. Reproducibility of PBF measurements was evaluated in three pigs. In eight pigs, undiluted and diluted Isovue-370 were separately injected to evaluate the effect of contrast viscosity on estimated PBF values. PBF was estimated with the peak-enhancement and the steepest-slope approach. Total-lung PBF was estimated in two healthy pigs to compare with cardiac output measured invasively by thermodilution in the pulmonary artery. Repeated measurements in the same animals yielded a good reproducibility of computed PBF maps. Injecting diluted isovue-370 resulted in smaller contrast-time curves in the pulmonary artery (P < 0.01) and vein (P < 0.01) without substantially diminishing peak signal intensity (P = 0.46 in the pulmonary artery) compared with the pure contrast agent since its viscosity is closer to that of blood. As compared with the peak-enhancement model, PBF values estimated by the steepest-slope model with diluted contrast were much closer to the cardiac output (R2 = 0.82) as compared with the peak-enhancement model. DCE-CT using the steepest-slope model and diluted contrast agent provided reliable quantitative estimates of PBF.NEW & NOTEWORTHY Dynamic contrast-enhanced CT using a lower-viscosity contrast agent in combination with tracer-kinetic analysis by the steepest-slope model improves pulmonary blood flow measurements and assessment of regional distributions of lung perfusion.

Efficient degradation and deiodination of iopamidol by UV/sulfite process: Assessment of typical process parameters and transformation paths.

Iopamidol (IPM) is widely used in medical clinical examination and treatment and has immeasurable harm to the ecological environment. The combination of UV and sulfite (UV/sulfite) process was developed to degrade IPM in this study. In contrast to that almost no removal of IPM was observed under sulfite reduction alone, the UV/sulfite process could efficiently reductively degrade IPM with the observed rate constant (kobs) of 2.08 min-1, which was nearly 4 times that of UV irradiation alone. The major active species in the UV/sulfite process were identified as hydrated electrons (eaq-) by employing active species scavengers. The influence of the initial pH, sulfite dosage, IPM concentration, UV intensity and common water matrix were evaluated. The degradation of IPM reached nearly 100% within only 2.5 min at pH 9, and kobs increased at higher initial sulfite dosages and greater UV intensities. HCO3- had a limited effect on the degradation of IPM, while humic acid (HA) was found to be a strong inhibitor in the UV/sulfite process. With the synergistic action of UV/sulfite, most of the iodine in IPM was found to release in the form of iodide ions (up to approximately 98%), and a few formed iodide-containing organic compounds, reducing significantly the toxicity of degradation products. Under direct UV irradiation and free radical reduction (mainly eaq-), 15 transformation intermediates of IPM were produced by amide hydrolysis, deiodination, hydroxyl radical addition and hydrogen abstraction reactions, in which free radical attack accounted for the main part. Consequently, the UV/sulfite process has a strong potential for IPM degradation in aquatic environments.

Low dose contrast CT for transcatheter aortic valve replacement assessment: Results from the prospective SPECTACULAR study (spectral CT assessment prior to TAVR).

BACKGROUND: Computed tomographic angiography (CTA) based planning for transcatheter aortic valve replacement (TAVR) is essential for reduction of periprocedural complications. Spectral CT based imaging provides several advantages, including better contrast/signal to noise ratio and increased soft tissue contrast, permitting better delineation of contrast filled structures at lower doses of iodinated contrast media. The aim of this prospective study was to assess the initial feasibility of a low dose iodinated contrast protocol, utilizing monoenergetic 40 keV reconstruction, using a dual-layer CT scanner (DLCT) for CTA in patients undergoing TAVR planning. METHODS: 116 consecutive TAVR patients underwent a gated chest and a non-gated CTA of the abdomen and pelvis. 40 keV virtual monoenergetic images (VMI) were reconstructed and compared with conventional polychromatic images (CI). The proximal aorta and access vessels were scored for image quality by independent experienced cardiovascular imagers. RESULTS: Proximal aortic image quality as assessed by signal to noise (SNR) and contrast to noise ratio (CNR), were significantly better with 40 keV VMI relative to CI (SNR 14.65 ±â€¯7.37 vs 44.16 ±â€¯22.39, p < 0.001; CNR 15.84 ±â€¯9.93 vs 59.8 ±â€¯40.83, p < 0.001). Aortic root dimensions were comparable between the two approaches with a bias towards higher measurements at 40 keV (Bland Altman). SNR and CNR in all access vessel segments at 40 keV were substantially better (p < 0.001 for all peripheral access vessel segments) with comparable image quality. CONCLUSION: 40 keV VMI with low dose contrast dose spectral imaging is feasible for comprehensive preprocedural evaluation of access vessels and measurements of aortic root dimensions in patients undergoing TAVR.

Assessment of Response to Neoadjuvant Therapy Using CT Texture Analysis in Patients With Resectable and Borderline Resectable Pancreatic Ductal Adenocarcinoma.

OBJECTIVE. The goal of this study was to assess the correlation between CT-derived texture features of pancreatic ductal adenocarcinoma (PDAC) and histologic and biochemical markers of response to neoadjuvant treatment as well as disease-free survival in patients with potentially resectable PDAC. SUBJECTS AND METHODS. Thirty-nine patients completed this prospective study protocol between November 2013 and December 2016. All patients received neoadjuvant chemotherapy, underwent surgical resection, and had histologic grading of tumor response. Similar CT protocol was used for all patients. Pancreatic (late arterial) phase of pre- and posttreatment CT scans were evaluated. Histogram analysis and spatial-band-pass filtration were used to extract textural features. Correlation between textural parameters, histologic response, biochemical response, and genetic mutations was assessed using Mann-Whitney test, chi-square analysis, and multivariate logistic regression. Association with disease-free survival was assessed using Kaplan-Meier method and Cox model. RESULTS. Pretreatment mean positive pixel (MPP) at fine- and medium-level filtration, pretreatment kurtosis at medium-level filtration, changes in kurtosis, and pretreatment tumor SD were statistically different between patients with no or poor histologic response and favorable histologic response (p < 0.05). Changes in skewness and kurtosis at medium-level filtration significantly correlated with biochemical response (p < 0.01). On the basis of multivariate analysis, patients with higher MPP at pretreatment CT were more likely to have favorable histologic response (odds ratio, 1.06; 95% CI, 1.002-1.12). The Cox model for association between textural features and disease-free survival was statistically significant (p = 0.001). CONCLUSION. Textural features extracted from baseline pancreatic phase CT imaging of patients with potentially resectable PDAC and longitudinal changes in tumor heterogeneity can be used as biomarkers for predicting histologic response to neoadjuvant chemotherapy and disease-free survival.

The additional value of the arterial phase in the CT assessment of liver vascular injuries after high-energy blunt trauma.

PURPOSE: In the literature, no consensus exists about which CT protocol is to be adopted in patients who underwent high-energy blunt trauma. The aim of the study is to evaluate the additional value of the arterial phase in the CT assessment of vascular injuries of the liver. METHODS: Admission CT examinations for patients with traumatic injury of the liver due to high-energy blunt trauma, performed between 2011 and 2017 in two major trauma centres, were retrospectively reviewed. Images were analysed for presence or absence of liver parenchymal injury, intrahepatic contained vascular injuries and active bleeding in the arterial and portal venous phase of the CT study. RESULTS: Two hundred twelve patients have been identified. Parenchymal injuries were detected as isolated in 90.6% of cases, whereas they were associated with vascular injuries in 9.4% of cases: contained vascular injuries in 3.3% and active bleeding in 6.1%. Out of all parenchymal injuries detected on the CT portal venous phase, 90.5% were also detectable in the arterial phases (p < 0.0001). All of the contained vascular injuries were visible in the CT arterial phase, whereas they were detectable in 28.5% of cases also during the venous phase (p = 0.02). All 13 cases of active bleeding were detected on the CT venous phase, and 76.9% of these cases were also revealed in the arterial phase, thus confirming their arterial origin (p = 0.22). CONCLUSION: The addiction of the arterial phase to the venous phase in the CT assessment of patients who underwent high-energy blunt trauma allows an accurate identification and characterization of traumatic vascular injuries, so distinguishing between patients suitable for conservative management and those requiring interventional or surgical treatment.

AcidoCEST-UTE MRI for the Assessment of Extracellular pH of Joint Tissues at 3 T.

OBJECTIVES: The goal of this study was to demonstrate feasibility of measuring extracellular pH in cartilage and meniscus using acidoCEST technique with a 3-dimensional ultrashort echo time readout (acidoCEST-UTE) magnetic resonance imaging (MRI). MATERIALS AND METHODS: Magnetization transfer ratio asymmetry, radiofrequency (RF) power mismatch, and relative saturation transfer were evaluated in liquid phantoms for iopromide, iopamidol, and iohexol over a pH range of 6.2 to 7.8, at various agent concentrations, temperatures, and buffer concentrations. Tissue phantoms containing cartilage and meniscus were evaluated with the same considerations for iopamidol and iohexol. Phantoms were imaged with the acidoCEST-UTE MRI sequence at 3 T. Correlation coefficients and coefficients of variations were calculated. Paired Wilcoxon rank-sum tests were used to evaluate for statistically significant differences. RESULTS: The RF power mismatch and relative saturation transfer analyses of liquid phantoms showed iopamidol and iohexol to be the most promising agents for this study. Both these agents appeared to be concentration independent and feasible for use with or without buffer and at physiologic temperature over a pH range of 6.2 to 7.8. Ultimately, RF power mismatch fitting of iohexol showed the strongest correlation coefficients between cartilage, meniscus, and fluid. In addition, ratiometric values for iohexol are similar among liquid as well as different tissue types. CONCLUSIONS: Measuring extracellular pH in cartilage and meniscus using acidoCEST-UTE MRI is feasible.

Acute Stroke: Prognostic Value of Quantitative Collateral Assessment at Perfusion CT.

Purpose To develop a quantitative assessment of collateral perfusion at CT and to investigate its value in the prediction of outcome in patients with acute ischemic stroke (AIS). Materials and Methods This retrospective study reviewed data from consecutive patients with AIS and an occluded M1 segment of the middle cerebral artery who underwent pretreatment perfusion CT between May 2009 and August 2017. The maximum cerebral blood flow (CBF) of collateral vessels (cCBFmax) within the Sylvian fissure was calculated for each patient. Good outcome was defined as a 90-day modified Rankin scale score of 0-2. Multivariable logistic regression analysis was used to determine the relationship between cCBFmax and (a) hemorrhagic transformation and (b) clinical outcome. Results The final analysis included 204 patients (median age, 73 years; interquartile range, 62-80 years; 82 [40.2%] women). Multivariable logistic regression analysis showed that higher cCBFmax was an independent predictor for (a) a lower risk of hemorrhagic transformation (odds ratio [OR], 0.99; 95% confidence interval [CI]: 0.98, 1.00; P = .009) after adjusting for baseline National Institutes of Health Stroke Scale (NIHSS), endovascular thrombectomy, baseline infarct core volume, and recanalization and (b) better outcome (OR, 1.02; 95% CI: 1.01, 1.03; P = .001) after adjusting for age, baseline NIHSS score, endovascular thrombectomy, hypertension, baseline infarct core volume, and recanalization, respectively. Conclusion The measurement of maximum cerebral blood flow of collateral vessels within the Sylvian fissure is a feasible quantitative collateral assessment at perfusion CT. Maximum cerebral blood flow of collateral vessels was associated with clinical outcome in patients with acute ischemic stroke. © RSNA, 2019 Online supplemental material is available for this article.

How we do it: shifting MR arthrogram compounding from the fluoroscopy suite to the sterile pharmacy.

OBJECTIVE: To assess the impact of shifting arthrogram injectate compounding from the fluoroscopy suite to the main hospital sterile pharmacy on cost, examination delays, and infection rates. MATERIALS AND METHODS: All arthrograms from the 12 months before (629 in total) and the 12 months after (699 in total) the change in arthrogram preparation procedure were compared to identify differences in examination delays and infection rate. The arthrogram formulation was sent to the Compounder's International Analytical Laboratory for stability testing. Finally, cost per injection analysis was performed to compare fluoroscopy suite with sterile pharmacy compounding. RESULTS: In the 699 arthrograms performed in the 12 months following transfer of arthrogram preparation to the main hospital pharmacy, there were 0 reported examination delays, 0 reported infections, and a 53% decrease in the material cost per arthrogram. There were three recorded instances of fluoroscopy suite preparation of arthrogram injectate due to unexpected add-on patients. Outside stability testing determined that the arthrogram injectate retained at least 90% potency 30 h post-preparation. CONCLUSION: Shifting the compounding of the arthrogram injectate from the fluoroscopy room to the main hospital sterile pharmacy provides a modest cost saving and can be accomplished without examination delays or any increase in infection rate. It brought our practice into compliance with USP797, which is the current guideline for compounding practitioners, by transferring the compounding preparation of the arthrogram injectate from a procedure room to the sterile pharmacy.

Feasibility study of a synchronized diastolic injection with low contrast volume for proper quantitative assessment of aortic regurgitation in porcine models.

OBJECTIVES: To evaluate the in vivo feasibility of aortography with one accurately timed diastolic low-volume contrast injection for quantitative assessment of aortic regurgitation (AR) post transcatheter aortic valve replacement (TAVR). BACKGROUND: With the rise of a minimalistic approach for TAVR, aortography (re)emerges as a pragmatic tool for AR assessment. In a mock circulation system, we have validated the accuracy of a single diastolic injection triggered by electrocardiogram (ECG) with low-contrast volume. METHODS: Two-phase experiment: first, a series of aortograms were performed in a porcine model, with 8 mL of contrast using the synchronized (SYNC) and the conventional non-synchronized (NS) injections. In a second phase, we developed a model of AR by inserting partially unsheathed Wallstents of 6-10 mm of diameter across the pig's aortic valve, performing SYNC injections with 8 mL of contrast and NS injections with 8 mL and 15 mL (rate: 20 mL/sec). Respective accuracies of SYNC vs. NS were assessed using Passing-Bablock regression. An angiography core laboratory performed quantitative AR assessment with videodensitometry (VD-AR). RESULTS: The SYNC injections produced higher opacification of the aortic root compared with NS injections (P = 0.04 for density). In the second phase, a regression line for predicting VD-AR based on the SYNC injection resulted in a lower intercept and a slope closer to the line of identity (y = 11.9 + 0.79x, P < 0.001, r2 = 0.94) with the NS-8 mL than with the NS-15 mL injection (y = 26.5 + 0.55x, P < 0.001, r2 = 0.81). CONCLUSION: Synchronized diastolic injection with low contrast volume produced denser images in the aortic root and more accurate than the conventional injection; thus, may be an appealing alternative for assessment of AR post TAVR.

Comparison of the different imaging time points in delayed phase cardiac CT for myocardial scar assessment and extracellular volume fraction estimation in patients with old myocardial infarction.

Delayed enhancement cardiac CT is a potential tool for myocardial viability assessment and is essential for extracellular volume fraction (ECV) estimation with CT. The objective of this study is to determine the optimal delay time for acquisition of delayed CT scans. Thirty-five patients with enhancement pattern typical of previous myocardial infarction on delayed CT and 17 control subjects comprised the study population. Delayed scans were acquired at 3, 5 and 7 min after contrast material injection. Image quality and estimated ECV were compared among the three time points. Delayed CT at 5 min showed the highest signal-to-noise ratio of 15.2 ± 1.0 [p < 0.0001; vs. 3 min (13.6 ± 1.0), p = 0.0015; vs. 7 min (14.9 ± 1.0)]. Contrast-to-noise ratio of infarcted and remote myocardium was highest at 7 min (6.4 ± 2.5), but was not significantly different from 5 min (6.1 ± 2.2, p = 0.08). The ECV values were constant over the three time points, although, in segments containing infarcted myocardium, trend of lower values was noted at 3 min compared to 5 and 7 min. ECV values at 5 min was 27.1% ± 2.1% in control subjects, 27.2% ± 3.0% in remote segments of patients with infarction, and 39.6% ± 5.3% in segments containing infarcted myocardium. Myocardial scars are equally best visualized with delay time of 5 and 7 min post contrast administration. No significant difference was observed in ECV of healthy myocardium or focal scars among delay time of 3, 5, and 7 min. Delay time of 5 min after contrast injection may be recommended for CT delayed enhancement imaging.

Late iodine enhancement computed tomography with image subtraction for assessment of myocardial infarction.

OBJECTIVE: To evaluate the feasibility of image subtraction in late iodine enhancement CT (LIE-CT) for assessment of myocardial infarction (MI). METHODS: A comprehensive cardiac CT protocol and late gadolinium enhancement MRI (LGE-MRI) was used to assess coronary artery disease in 27 patients. LIE-CT was performed after stress CT perfusion (CTP) and CT angiography. Subtraction LIE-CT was created by subtracting the mask volume of the left ventricle (LV) cavity from the original LIE-CT using CTP dataset. The %MI volume was quantified as the ratio of LIE to entire LV volume, and transmural extent (TME) of LIE was classified as 0%, 1-24%, 25-49%, 50-74% or 75-100%. These results were compared with LGE-MRI using the Spearman rank test, Bland-Altman method and chi-square test. RESULTS: One hundred twenty-five (29%) of 432 segments were positive on LGE-MRI. Correlation coefficients for original and subtraction LIE-CT to LGE-MRI were 0.79 and 0.85 for %MI volume. Concordances of the 5-point grading scale between original and subtraction LIE-CT with LGE-MRI were 75% and 84% for TME; concordance was significantly improved using the subtraction technique (p <0.05). CONCLUSION: Subtraction LIE-CT allowed more accurate assessment of MI extent than the original LIE-CT. KEY POINTS: • Subtraction LIE-CT allows for accurate assessment of the extent of myocardial infarction. • Subtraction LIE-CT shows a close correlation with LGE-MRI in %MI volume. • Subtraction LIE-CT has significantly higher concordance with TME assessment than original LIE-CT.

Role of rapid kV-switching dual-energy CT in assessment of post-surgical local recurrence of pancreatic adenocarcinoma.

PURPOSE: The purpose of this study is to evaluate the performance of material-specific iodine (MS-I) images generated by rapid kV-switching single-source dual-energy computed tomography (rsDECT) for distinguishing post-operative changes from local tumor recurrence in patients on follow-up for pancreatic adenocarcinoma after surgical resection. METHODS: In this IRB-approved HIPPA-compliant study, retrospective review of 51 patients who underwent surgical resection of pancreatic adenocarcinoma was conducted and were followed up using contrast-enhanced rsDECT (Discovery CT 750HD, GE Healthcare, Milwaukee, WI). Independent qualitative assessment for presence of local tumor recurrence was performed by two radiologists who evaluated 65 keV (single-energy CT-equivalent interpretation) and 65 keV with MS-I (rsDECT interpretation) in separate sessions. Quantitative analysis of Hounsfield unit (HU, on 65 keV) and normalized iodine concentration (NIC on MS-I images; iodine concentration ratio in post-operative tissue to aorta) was measured. Follow-up imaging, temporal change of CEA and CA 19-9 or biopsy served as reference standard for presence and absence of local recurrence. Sensitivity and specificity of readers and quantitative parameters was calculated and receiver operating characteristic curves and Fisher's exact test were generated. A p value < 0.05 was considered statistically significant. RESULTS: A total of 51 patients (27 females, 24 males) with mean age of 64 years built the final cohort. Local recurrence was absent in 23 (Group A) and present in 28 (Group B) patients. The follow-up imaging was performed within 7 months of rsDECT. For both readers, the addition of MS-I increased the specificity for tissue characterization and improved reader confidence as compared to 65 keV (specificity: 80% and 56%, respectively) images alone. Quantitative analysis revealed a significantly lower NIC (0.28 vs. 0.35; p < 0.05) for non-recurrent tissue. However, HU was not significantly different for non-recurrent and recurrent tissue (0.63 vs. 0.70; p > 0.05). CONCLUSION: In inherently complex cases of post-operative pancreatic adenocarcinoma, MS-I images from rsDECT can be a useful adjunct to conventional scans in characterizing loco-regional soft tissue.

Assessment of Cirrhotic Liver Enhancement With Multiphasic Computed Tomography Using a Faster Injection Rate, Late Arterial Phase, and Weight-Based Contrast Dosing.

PURPOSE: This study aimed to update our liver computed tomography (CT) protocol according to published guidelines, and to quantitatively evaluate the effect of these modifications. METHODS: The modified liver CT protocol employed a faster injection rate (5 vs 3 mL/s), later arterial phase (20-second vs 10-second postbolus trigger), and weight-based dosing of iodinated contrast (1.7 mL/kg vs 100 mL fixed dose). Liver and vascular attenuation values were measured on CTs of patients with cirrhosis from January to September 2015 (old protocol, n = 49) and from October to December 2015 (modified protocol, n = 31). CTs were considered adequate if liver enhancement exceeded 50 Hounsfield units (HU) in portal venous phase, or when the unenhanced phase was unavailable, if a minimum iodine concentration of 500 mg I/kg was achieved. Attenuations and iodine concentrations were compared using the t test and the number of suboptimal studies was compared with Fisher's exact test. RESULTS: CTs acquired with the modified protocol demonstrated higher aortic (P = .001) and portal vein (P < .0001) attenuations in the arterial phase as well as greater hepatic attenuation on all postcontrast phases (P = .0006, .002, and .003 for arterial, venous, and equilibrium phases, respectively). Hepatic enhancement in the portal venous phase (61 ± 15 HU vs 51 ± 16 HU; P = .0282) and iodine concentrations (595 ± 88 mg I/kg vs 456 ± 112 mg I/kg; P < .0001) were improved, and the number of suboptimal studies was reduced from 57% to 23% (P = .01). CONCLUSIONS: A liver CT protocol with later arterial phase, faster injection rate, and weight-based dosing of intravenous contrast significantly improves liver enhancement and iodine concentrations in patients with cirrhosis, resulting in significantly fewer suboptimal studies.

Comparative assessment of image quality for coronary CT angiography with iobitridol and two contrast agents with higher iodine concentrations: iopromide and iomeprol. A multicentre randomized double-blind trial.

OBJECTIVES: To demonstrate non-inferiority of iobitridol 350 for coronary CT angiography (CTA) compared to higher iodine content contrast media regarding rate of patients evaluable for the presence of coronary artery stenoses. METHODS: In this multicentre trial, 452 patients were randomized to receive iobitridol 350, iopromide 370 or iomeprol 400 and underwent coronary CTA using CT systems with 64-detector rows or more. Two core lab readers assessed 18 coronary segments per patient regarding image quality (score 0 = non diagnostic to 4 = excellent quality), vascular attenuation, signal and contrast to noise ratio (SNR, CNR). Patients were considered evaluable if no segment had a score of 0. RESULTS: Per-patient, the rate of fully evaluable CT scans was 92.1, 95.4 and 94.6 % for iobitridol, iopromide and iomeprol, respectively. Non-inferiority of iobitridol over the best comparator was demonstrated with a 95 % CI of the difference of [-8.8 to 2.1], with a pre-specified non-inferiority margin of -10 %. Although average attenuation increased with higher iodine concentrations, average SNR and CNR did not differ between groups. CONCLUSIONS: With current CT technology, iobitridol 350 mg iodine/ml is not inferior to contrast media with higher iodine concentrations in terms of image quality for coronary stenosis assessment. KEY POINTS: • Iodine concentration is an important parameter for image quality in coronary CTA. • Contrast enhancement must be balanced against the amount of iodine injected. • Iobitridol 350 is non-inferior compared to CM with higher iodine concentrations. • Higher attenuation with higher iodine concentrations, but no SNR or CNR differences.

MRI-CEST assessment of tumour perfusion using X-ray iodinated agents: comparison with a conventional Gd-based agent.

OBJECTIVES: X-ray iodinated contrast media have been shown to generate contrast in MR images when used with the chemical exchange saturation transfer (CEST) approach. The aim of this study is to compare contrast enhancement (CE) capabilities and perfusion estimates between radiographic molecules and a Gd-based contrast agent in two tumour murine models with different vascularization patterns. METHODS: MRI-CEST and MRI-CE T1w images were acquired in murine TS/A and 4 T1 breast tumours upon sequential i.v. injection of iodinated contrast media (iodixanol, iohexol, and iopamidol) and of gadoteridol. The signal enhancements observed in the two acquisition modalities were evaluated using Pearson's correlation, and the correspondence in the spatial distribution was assessed by a voxelwise comparison. RESULTS: A significant, positive correlation was observed between iodinated contrast media and gadoteridol for tumour contrast enhancement and perfusion values for both tumour models (r = 0.51-0.62). High spatial correlations were observed in perfusion maps between iodinated molecules and gadoteridol (r = 0.68-0.86). Tumour parametric maps derived by iodinated contrast media and gadoteridol showed high spatial similarities. CONCLUSIONS: A good to strong spatial correlation between tumour perfusion parameters derived from MRI-CEST and MRI-CE modalities indicates that the two procedures provide similar information. KEY POINTS: • Gd-based agents are the standard of reference for contrast-enhanced MRI. • Iodinated contrast media provides MRI-CEST contrast enhancement in animal tumour models. • Contrast enhancements were positively correlated between iodinated agents and gadoteridol. • Tumour perfusion map showed similar spatial distribution between iodinated agents and gadoteridol. • MRI-CEST with iodinated agents provide similar information to gadoteridol.

MDCT assessment of resectability in hilar cholangiocarcinoma.

PURPOSE: The purpose of this study is to investigate the value of multidetector computed tomography (MDCT) assessment of resectability in hilar cholangiocarcinoma, and to identify the factors associated with unresectability and accurate evaluation of resectability. METHODS: From January 2007 to June 2015, a total of 77 consecutive patients were included. All patients had preoperative MDCT (with MPR and MinIP) and surgical treatment, and were pathologically proven with hilar cholangiocarcinoma. The MDCT images were reviewed retrospectively by two senior radiologists and one hepatobiliary surgeon. The surgical findings and pathologic results were considered to be the gold standard. The Chi square test was used to identify factors associated with unresectability and accurate evaluation of resectability. RESULTS: The sensitivity, specificity, and overall accuracy of MDCT assessment were 83.3 %, 75.9 %, and 80.5 %, respectively. The main causes of inaccuracy were incorrect evaluation of N2 lymph node metastasis (4/15) and distant metastasis (4/15). Bismuth type IV tumor, main or bilateral hepatic artery involvement, and main or bilateral portal vein involvement were highly associated with unresectability (P < 0.001). Patients without biliary drainage had higher accuracy of MDCT evaluation of resectability compared to those with biliary drainage (P < 0.001). CONCLUSION: MDCT is reliable for preoperative assessment of resectability in hilar cholangiocarcinoma. Bismuth type IV tumor and main or bilateral vascular involvement highly suggest the unresectability of hilar cholangiocarcinoma. Patients without biliary drainage have a more accurate MDCT evaluation of resectability. We suggest MDCT should be performed before biliary drainage to achieve an accurate evaluation of resectability in hilar cholangiocarcinoma.

Assessment of myocardial delayed enhancement with cardiac computed tomography in cardiomyopathies: a prospective comparison with delayed enhancement cardiac magnetic resonance imaging.

To evaluate the feasibility of cardiac CT for the evaluation of myocardial delayed enhancement (MDE) in the assessment of patients with cardiomyopathy, compared to cardiac MRI. A total of 37 patients (mean age 54.9 ± 15.7 years, 24 men) who underwent cardiac MRI to evaluate cardiomyopathy were enrolled. Dual-energy ECG-gated cardiac CT was acquired 12 min after contrast injection. Two observers evaluated cardiac MRI and cardiac CT at different kV settings (100, 120 and 140 kV) independently for MDE pattern-classification (patchy, transmural, subendocardial, epicardial and mesocardial), differentiation between ischemic and non-ischemic cardiomyopathy and MDE quantification (percentage MDE). Kappa statics and the intraclass correlation coefficient were used for statistical analysis. Among different kV settings, 100-kV CT showed excellent agreements compared to cardiac MRI for MDE detection (κ = 0.886 and 0.873, respectively), MDE pattern-classification (κ = 0.888 and 0.881, respectively) and differentiation between ischemic and non-ischemic cardiomyopathy (κ = 1.000 and 0.893, respectively) for both Observer 1 and Observer 2. The Bland-Altman plot between MRI and 100-kV CT for the percentage MDE showed a very small bias (-0.15%) with 95% limits of agreement of -7.02 and 6.72. Cardiac CT using 100 kV might be an alternative method to cardiac MRI in the assessment of cardiomyopathy, particularly in patients with contraindications to cardiac MRI.

Assessment of 3 Bowel Preparation Protocols for Computed Tomography Pneumocolonography in Normal Dogs.

OBJECTIVE: To investigate the effects of 3 different bowel preparation protocols on interpretation of computed tomography (CT) pneumocolonography images. STUDY DESIGN: Experimental crossover design. ANIMALS: Intact male, hound-cross, research colony dogs (n=4). METHODS: All dogs received the 3 different bowel preparation protocols for CT pneumocolonography in the same order, with a minimum of 2 weeks between protocols. For each segment of large bowel, the subjective adequacy of bowel cleansing was assessed, residual fecal and bowel volumes were calculated, and the density of fecal material in the bowel lumen was measured. Linear mixed effect models that included a random dog effect were used to evaluate mean differences in outcome measures across protocols. RESULTS: No dogs experienced any clinical problems associated with the protocols or CT pneumocolonography. Bowel cleansing was considered adequate for CT pneumocolonography interpretation for all 3 protocols. There was a significant effect of protocol on residual fecal volumes and the fecal:bowel volume ratio, with the 2 protocols that included an extended fast producing the lowest total residual fecal volumes. There was a significant effect of protocol on maximum measured density of residual fecal material with the 2 protocols including iodinated contrast having the highest density. CONCLUSIONS: All protocols were sufficient for CT pneumocolonography interpretation and contrast-tagging of residual fecal material was successful with oral iopamidol administration. An at-home bowel cleansing protocol may provide adequate bowel cleansing for CT pneumocolonography image interpretation.

Assessment and treatment planning of lateral intracranial dural arteriovenous fistulas in 3 T MRI and DSA: A detailed analysis under consideration of time-resolved imaging of contrast kinetics (TRICKS) and ce-MRA sequences.

OBJECTIVES: The current gold standard in the assessment of lateral intracranial dural arteriovenous fistulas (LDAVF) is digital subtraction angiography (DSA). However, magnetic resonance imaging (MRI) is a non-invasive emerging tool for the evaluation of such lesions. The aim of our study was to compare the DSA to our 3 T MR-imaging protocol including a highly spatial resolved (ce-MRA) and a temporal resolved ("time-resolved imaging of contrast kinetics", TRICKS) contrast-enhanced MR angiography to evaluate if solely DSA can remain the gold-standard imaging modality for the treatment planning of LDAVF. METHODS: We retrospectively reviewed matched pairs of DSA and 3 T MRI examinations of 24 patients with LDAVF (03/2008-04/2014) by the same list of relevant criteria for an endovascular LDAVF treatment planning. In particular, we determined intermodality agreement for the Cognard classification, the identifeication of arterial feeders, and the detailed assessment of each venous drainage pattern. RESULTS: Intermodality agreement for the Cognard classification was excellent (ĸ = 1.0). Whereas MRI failed in identifying small arterial feeders, it was superior to the DSA in the assessment of the sinus and the venous drainage pattern. CONCLUSIONS: The combination of MRI and DSA is the new gold standard in LDAVF treatment planning. KEY POINTS: • DSA is superior to the MRI in detecting LDAVF arterial feeders. • MRI excellently evaluates the venous side of an LDAVF. • MRI can replace DSA in initial diagnosis and monitoring of LDAVF. • MRI and DSA combined are the new gold standard in LDAVF treatment planning.