Optimal Vascular and Parenchymal Contrast Enhancement: The Current State of the Art

Novel Computed Tomography Angiography Parameter Is Associated with Low Cardiac Index in Patients with Chronic Thromboembolic Pulmonary Hypertension: A Retrospective Analysis

Chronic thromboembolic pulmonary hypertension (CTEPH) is a complication of incomplete resolution of acute pulmonary embolism. We hypothesize changes in CT Hounsfield Unit gradient (HU-Δ) created by the dispersion of IV contrast through the downstream blood pool correlate with cardiac index (CI). We sought to compare HU-Δ with invasively obtained CI.

METHODS

We completed a retrospective analysis of CTEPH patients in which individuals with low CI (<2.2-L/min/m2) were identified. Both absolute and fractional HU-Δ were derived from pulmonary CTA by subtracting the HU value of the left atrium (LA) and left ventricle (LV) from the main pulmonary artery (MPA) (absolute) and expressing them as a percentage of MPA-HU (fractional) on static axial images. These were compared between low and normal CI.

RESULTS

Of the 237 patients, 50.2% were female, 53.2% were White, 36.7% were Black. Hemodynamics were mean pulmonary artery (PA) pressure = 45.4 ± 11.2-mmHg, pulmonary vascular resistance = 9.2 ± 4.4-WU, CI = 2.05 ± 0.48-L/min/m2. There was a higher mean MPA-HU = 391.1 ± 113.6 than LA-HU = 251.6 ± 81. In patients with low CI, the HU-Δ was higher, HU-ΔMPA-LA was 148.9 ± 78.4 vs. 124.5 ± 77.2 (p = 0.02), and HU-ΔMPA-LV was 170.7 ± 87 vs. 140 ± 82 (p = 0.009). A HU-ΔMPA-LA = 118 had a sensitivity of 75.6% and specificity of 77% to detect low CI, AUC 0.61, p = 0.003. A HU-ΔPA-LV = 156 had a sensitivity of 77% and specificity of 53% to detect low CI, AUC = 0.62, p = 0.001. A fractional reduction HU-ΔMPA-LA of 35% had a sensitivity and specificity of 79% and 53%, respectively, to detect low CI (AUC 0.65, p < 0.001). A fractional reduction of the HU-ΔMPA-LV of 40% had a sensitivity and specificity of 80% and 55%, respectively, to detect low CI (AUC 0.65, p < 0.001). HU Δ were highly reproducible (Kappa = 0.9, p < 0.001, 95% CI 0.86-0.95).

CONCLUSIONS

High HU Δ between MPA-LA and MPA-LV were associated with low CI in patients with CTEPH.

Imaging features and management of focal liver lesions

Notably, the number of incidentally detected focal liver lesions (FLLs) has increased dramatically in recent years due to the increased use of radiological imaging. The diagnosis of FLLs can be made through a well-documented medical history, physical examination, laboratory tests, and appropriate imaging methods. Although benign FLLs are more common than malignant ones in adults, even in patients with primary malignancy, accurate diagnosis of incidental FLLs is of utmost clinical significance. In clinical practice, FLLs are frequently evaluated non-invasively using ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI). Although US is a cost-effective and widely used imaging method, its diagnostic specificity and sensitivity for FLL characterization are limited. FLLs are primarily characterized by obtaining enhancement patterns through dynamic contrast-enhanced CT and MRI. MRI is a problem-solving method with high specificity and sensitivity, commonly used for the evaluation of FLLs that cannot be characterized by US or CT. Recent technical advancements in MRI, along with the use of hepatobiliary-specific MRI contrast agents, have significantly improved the success of FLL characterization and reduced unnecessary biopsies. The American College of Radiology (ACR) appropriateness criteria are evidence-based recommendations intended to assist clinicians in selecting the optimal imaging or treatment option for their patients. ACR Appropriateness Criteria Liver Lesion-Initial Characterization guideline provides recommendations for the imaging methods that should be used for the characterization of incidentally detected FLLs in various clinical scenarios. The American College of Gastroenterology (ACG) Clinical Guideline offers evidence-based recommendations for both the diagnosis and management of FLL. American Association for the Study of Liver Diseases (AASLD) Practice Guidance provides an approach to the diagnosis and management of patients with hepatocellular carcinoma. In this article, FLLs are reviewed with a comprehensive analysis of ACR Appropriateness Criteria, ACG Clinical Guideline, AASLD Practice Guidance, and current medical literature from peer-reviewed journals. The article includes a discussion of imaging methods used for the assessment of FLL, current recommended imaging techniques, innovations in liver imaging, contrast agents, imaging features of common nonmetastatic benign and malignant FLL, as well as current management recommendations.

A patient-specific timing protocol for improved CT pulmonary angiography

Rationale and objectives

To improve the image quality of CT pulmonary angiography (CTPA) using a patient-specific timing protocol.

Material and methods

A total of 24 swine (48.5 ± 14.3 kg) underwent continuous contrast-enhanced dynamic CT acquisition over 30 s to capture the pulmonary arterial input function (AIF). Multiple contrast injections were made under different cardiac outputs (1.4-5.1 L/min), resulting in a total of 154 AIF curves. The volume scans with maximal enhancement in these AIF curves were retrospectively selected as the reference standard (group A). Two prospective CTPA protocols with bolus-tracking were then simulated using these AIF curves: one used a fixed delay of 5 s between triggering and CTPA acquisition (group B), while the other used a specific delay based on one-half of the contrast injection duration (group C). The mean attenuation, signal-to-noise (SNR) and contrast-to-noise ratios (CNR) between the three groups were then compared using independent sample t-test. Subjective image quality scores were also compared using Wilcoxon-Mann-Whitney test.

Results

The mean attenuation of pulmonary arteries for group A, B and C (expressed in [HU]) were 870.1 ± 242.5 HU, 761.1 ± 246.7 HU and 825.2 ± 236.8 HU, respectively. The differences in the mean SNR and CNR between Group A and Group C were not significant (SNR: 65.2 vs. 62.4, CNR: 59.6 vs. 56.4, both p > 0.05), while Group B was significantly lower than Group A (p < 0.05).

Conclusion

The image quality of CT pulmonary angiography is significantly improved with a timing protocol determined using contrast injection delivery time, as compared with a standard timing protocol with a fixed delay between bolus triggering and image acquisition.

Can we rely on contrast-enhanced CT to identify pancreatic ductal adenocarcinoma? A population-based study in sensitivity and factors associated with false negatives

OBJECTIVES

To determine the sensitivity of contrast-enhanced computed tomography (CECT) in detecting pancreatic ductal adenocarcinoma (PDAC) and identify factors associated with false negatives (FNs).

METHODS

Patients diagnosed with PDAC in 2014-2015 were retrospectively identified by a cancer registry. CECTs performed during the diagnostic interval were retrospectively classified as true positive (TP), indeterminate, or FN. Sensitivity TP/(TP+FN) was calculated for all CECTs and the following subgroups: protocol (uniphasic vs. biphasic); tumor size (≤ 2 cm vs. > 2 cm); and resectability (potentially resectable vs. unresectable). Multivariate logistic regression was performed to assess which of the following factors were associated with FN: clinical suspicion of PDAC; size >2 cm; presence of metastases; protocol; isoattenuating tumor; and potentially resectable disease on imaging.

RESULTS

In total, 176 CECTs (127 uniphasic; 49 biphasic) in 154 patients (90 men, mean age 72 ± 11 years) were included. Sensitivity was 125/149 (83.9%) overall and 87/106 (82.1%) and 38/43 (88.4%) for uniphasic and biphasic protocols, respectively. Sensitivity was decreased for tumors ≤ 2 cm (45.4% vs. 90.6%), no liver metastases (78.0% vs. 95.9%), and potentially resectable disease (65.3% vs. 93.0%). Factors significantly associated with FN were clinical suspicion (OR, 0.24, 95% CI: 0.07-0.75), size>2 cm (OR, 0.10, 95% CI: 0.02-0.44), absence of liver metastases (OR, 4.94, 95% CI: 1.29-22.99), and potentially resectable disease (OR, 4.13, 95% CI: 1.07-16.65).

CONCLUSIONS

In our population, the overall sensitivity of CECT to detect PDAC is 83.9%; however, this is substantially lower in several scenarios, including patients with potentially resectable disease. This finding has important implications for patient outcomes and efforts to maximize CECT sensitivity should be sought.

CLINICAL RELEVANCE STATEMENT

The sensitivity of CECT to detect PDAC is significantly decreased in the setting of sub-2 cm tumors and potentially resectable disease. A dedicated biphasic pancreatic CECT protocol has higher sensitivity and should be applied in patients with suspected pancreatic disease.

KEY POINTS

• The sensitivities of contrast-enhanced CT for the detection of PDAC were 87/106 (82.1%) and 38/43 (88.4%) for uniphasic and biphasic protocols, respectively. • The sensitivity of contrast-enhanced CT was decreased for small tumors ≤ 2 cm (45.4% vs. 90.6%), if there were no liver metastases (78.0% vs. 95.9%), and with potentially resectable disease (65.3% vs. 93.0%). • Absence of liver metastases (OR, 4.94, 95% CI: 1.29-22.99) and potentially resectable disease (OR, 4.13, 95% CI: 1.07-16.65) were associated with a false--negative (FN) CT result; suspicion of malignancy on the imaging requisition (OR, 0.24, 95% CI: 0.07-0.75) and size > 2 cm (OR, 0.10, 95% CI: 0.02-0.44) were negatively associated with FN.

Patient-specific post-trigger delay in coronary CT angiography: A prospective study comparing with fixed delay

OBJECTIVES

To validate the peak enhancement timing of a patient-specific post-trigger delay (PTD) in Coronary CT angiography (CCTA) and compare its image quality against a fixed PTD.

METHODS

In this prospective study, 204 consecutive participants were randomly divided into two groups to perform CCTA in bolus tracking with either a fixed 5-second PTD (Group A) or a patient-specific PTD (Group B). Test bolus was also performed in Group B to determine the reference peak enhancement timing. One reader evaluated objective image quality, while two readers rated subjective image quality. The predicted PTD was validated through correlation and agreement analysis with the reference measurement. Objective image quality was compared between groups via two-sample t-test and linear regression, while the subjective ratings were compared with chi-square analysis.

RESULTS

The two groups each had 102 participants with comparable characteristics (52.9 ± 11.3 versus 52.1 ± 11.3 years of age, and 53 versus 52 males). The scan timing from patient-specific PTD demonstrated strong correlation (R = 0.77) and consistency (ICC = 0.618) with the reference peak timing. Both readers rated better subjective image quality for the Group B (p < 0.001). The mean vessel enhancement was significantly higher in Group B in all coronary vessels (all p < 0.05). After adjusting for the participant variation, the patient-specific PTD strategy was associated with an average of 33.5 HU higher enhancement compared to the fixed PTD.

CONCLUSIONS

Patient-specific delay could achieve reliable scan timing, optimize vessel opacification and obtain better image quality in CCTA.

Intravenous Contrast Material for Cardiac Computed Tomography: Results From the Open-label Multicenter, Multivendor Italian Registry of Contrast Material Use in Cardiac Computed Tomography

PURPOSE

The Italian Registry of Contrast Material use in Cardiac Computed Tomography (iRCM-CCT) is a multicenter, multivendor, observational study on the use of contrast media (CM) in patients undergoing cardiac computed tomography (CCT). The aim of iRCM-CCT is to assess image quality and safety profile of intravenous CM compounds.

MATERIALS AND METHODS

iRCM-CCT enrolled 1842 consecutive patients undergoing CCT (≥50 per site) at 20 cluster sites with the indication of suspected coronary artery disease. Demographic characteristics, CCT, and CM protocols, clinical indications, safety markers, radiation dose reports, qualitative (ie, poor vascular enhancement) and quantitative (ie, HU attenuation values) image parameters were recorded. A centralized coordinating center collected and assessed all image parameters.

RESULTS

The cohort included 891 men and 951 women (age: 63±14 y, body mass index: 26±4 kg/m2) studied with ≥64 detector rows computed tomography scanners and different iodinated intravenous CM protocols and compounds (iodixanol, iopamidol, iohexol, iobitridol, iopromide, and iomeprol). The following vascular attenuation was reported: 504±147 HU in the aorta, 451±146 HU in the right coronary artery, 474±146 HU in the left main, 451±146 HU in the left anterior descending artery, and 441±149 HU in the circumflex artery. In 4% of cases the image quality was not satisfactory due to poor enhancement. The following adverse reactions to CM were recorded: 6 (0.3%) extravasations and 17 (0.9%) reactions (11 mild, 4 moderate, 2 severe).

CONCLUSIONS

In a multicenter registry on CM use during CCT the prevalence of CM-related adverse reactions was very low. The appropriate use of CM is a major determinant of image quality.

Improvement in arterial enhancement using diluted injection of contrast medium in CT angiography

BACKGROUND

Arterial enhancement after contrast injection affects the quality of computed tomography angiography (CTA) images.

PURPOSE

To evaluate whether the dilution of contrast medium (CM) for CTA increases arterial enhancement after the adjustment of iodine concentration as per the patient's body weight (BW).

MATERIAL AND METHODS

We retrospectively studied 700 patients who underwent coronary CTA. The first 350 consecutive patients underwent standard CTA with a fixed iodine concentration, whereas the remaining 350 underwent CTA with a diluted CM injection. All patients were classified into three groups according to their BW (<55, 55-65, and 66-73 kg). The mean and proportion of contrast enhancements (CEs) in the ascending aorta of ≥350 Hounsfield units (HUs) (CE₃₅₀) were compared between the standard CTA and diluted CM injection and among the BW groups. The associations between BW and CE were analyzed using linear regression.

RESULTS

Receiving diluted CM increased the mean CE in the <55-kg group (403.4 ± 55.4 HU vs. 382.8 ± 59.3 HU; P < 0.01) but not in the groups with heavier BW. The proportion of patients with CE₃₅₀ increased with BW (<55 kg = 71%, 55-65 kg = 84%, and 66-73 kg = 91%) and increased after dilution (86%, 93%, and 96%, respectively). After CM dilution, the correlation between BW and CE among patients undergoing CTA decreased from 0.37 to 0.22 (P < 0.05).

CONCLUSION

CM dilution for CTA improves arterial enhancement.

Comparison of Turbo Flash and dual-energy modes of third-generation dual-source CT in pre-transplant renal angiography: a prospective observational study

Background

The purpose of this study was to compare the Image Quality, Contrast Medium Volume, and Radiation dose in renal angiography performed using Turbo Flash mode and dual-energy (DE) mode in the third-generation dual-source dual-energy CT.

This prospective observational study was performed on renal donors who underwent CTA imaging as a pre-transplant workup. The study population was divided into two groups. Group A underwent DECT renal angiography. Group B underwent Turbo Flash Mode CT renal angiography. For group A, a contrast volume of 1 ml/kg and for group B at 0.5 ml/kg was administered. Image Quality was evaluated objectively by calculating CNR and SNR and subjectively by a 5-point scale. Radiation Dose analysis was done by noting CTDIvol and DLP on the scanner system and calculating effective radiation dose (ED).

Results

The subjective image quality scores for the Turbo Flash group were comparable with the DE group in qualitative image analysis. Additionally, in the Turbo Flash group, there was a reduction in contrast media and effective radiation dose by 47.5% and 32.7%, respectively. Nevertheless, mean attenuation of the abdominal arteries, CNR, SNR, and Noise (S.D) showed statistical significance between the two groups (p value < 0.01).

Conclusions

To our knowledge, no previous study compared Turboflash mode with DE protocol in CT renal angiography in a donor group of patients. Turbo Flash CT is an excellent modality that is faster and has an added advantage of decreased radiation dose and contrast media volume reduction, which can be recommended for screening of voluntary kidney donors but needs further clinical studies, validation, and standardization with tailored protocols.

Heterogeneity in Utilization of Optical Imaging Guided Surgery for Identifying or Preserving the Parathyroid Glands—A Meta-Narrative Review

Background: Postoperative hypoparathyroidism is the most common complication after total thyroidectomy. Over the past years, optical imaging techniques, such as parathyroid autofluorescence, indocyanine green (ICG) angiography, and laser speckle contrast imaging (LSCI) have been employed to save parathyroid glands during thyroid surgery. This study provides an overview of the utilized methods of the optical imaging techniques during total thyroidectomy for parathyroid gland identification and preservation. Methods: PUBMED, EMBASE and Web of Science were searched for studies written in the English language utilizing parathyroid autofluorescence, ICG-angiography, or LSCI during total thyroidectomy to support parathyroid gland identification or preservation. Case reports, reviews, meta-analyses, animal studies, and post-mortem studies were excluded after the title and abstract screening. The data of the studies were analyzed qualitatively, with a focus on the methodologies employed. Results: In total, 59 articles were included with a total of 6190 patients. Overall, 38 studies reported using parathyroid autofluorescence, 24 using ICG-angiography, and 2 using LSCI. The heterogeneity between the utilized methodology in the studies was large, and in particular, regarding study protocols, imaging techniques, and the standardization of the imaging protocol. Conclusion: The diverse application of optical imaging techniques and a lack of standardization and quantification leads to heterogeneous conclusions regarding their clinical value. Worldwide consensus on imaging protocols is needed to establish the clinical utility of these techniques for parathyroid gland identification and preservation.

Using Machine Learning to Identify Intravenous Contrast Phases on Computed Tomography

PURPOSE

The purpose of the present work is to demonstrate the application of machine learning (ML) techniques to automatically identify the presence and physiologic phase of intravenous (IV) contrast in Computed Tomography (CT) scans of the Chest, Abdomen and Pelvis.

MATERIALS AND METHODS

Training, testing and validation data were acquired from a dataset of 82,690 chest and abdomen CT examinations performed at 17 different institutions. Free text in DICOM metadata was utilized as weak labels for semi-supervised classification training. Contrast phase identification was approached as a classification task, using a 12-layer CNN and ResNet18 with four contrast-phase output. The model was reformulated to fit a regression task aimed to predict actual seconds from time of IV contrast administration to series image acquisition. Finally, transfer learning was used to optimize the model to predict contrast presence on CT Chest.

RESULTS

By training based on labels inferred from noisy, free text DICOM information, contrast phase was predicted with 93.3% test accuracy (95% CI: 89.3%, 96.6%) . Regression analysis resulted in delineation of early vs late arterial phases and a nephrogenic phase in between the portal venous and delayed excretory phase. Transfer learning applied to Chest CT achieved an AUROC of 0.776 (95% CI: 0.721, 0.832) directly using the model trained for abdomen CT and 0.999 (95% CI: 0.998, 1.000) by fine-tuning.

CONCLUSIONS

The presence and phase of contrast on CT examinations of the Abdomen-pelvis accurately and automatically be ascertained by a machine learning algorithm. Transfer learning applied to CT Chest achieves high precision with as little as 100 labeled samples.

Lean body weight-adjusted intravenous iodinated contrast dose for abdominal CT in dogs reduces interpatient enhancement variability while providing diagnostic quality organ enhancement

Contrast-enhanced computed tomography (CECT) is increasingly used to screen for abdominal pathology in dogs, and the contrast dose used is commonly calculated as a linear function of total body weight (TBW). Body fat is not metabolically active and contributes little to dispersing or diluting contrast medium (CM) in the blood. This prospective, analytic, cross-section design pilot study aimed to establish the feasibility of intravenous CM dosed according to lean body weight (LBW) for abdominal CECT in dogs compared to TBW. We hypothesized that when dosing intravenous CM according to LBW, studies will remain at diagnostic quality, there will be a reduced interindividual contrast enhancement (CE) variability, and there will be less change to heart rate and blood pressure in dogs compared to when administering CM calculated on TBW. Twelve dogs had two CECT studies with contrast doses according to TBW and LBW at least 8 weeks apart. Interindividual organ and vessel CE variability, diagnostic quality of the studies, and changes in physiological status were compared between protocols. The LBW-based protocol provided less variability in the CE of most organs and vessels (except the aorta). When dosed according to LBW, liver enhancement was positively associated with grams of iodine per kg TBW during the portal venous phase (P = 0.046). There was no significant difference in physiological parameters after CM administration between dosing protocols. Our conclusion is that a CM dose based on LBW for abdominal CECT lowers interindividual CE variability and is effective at maintaining studies of diagnostic quality.

Contrast media injection protocol for portovenous phase abdominal CT: does a fixed injection duration improve hepatic enhancement over a fixed injection rate?

PURPOSE

To assess whether a fixed contrast media (CM) injection duration improves the magnitude and inter-patient variability in hepatic enhancement over a fixed injection rate.

METHODS

Outpatients who underwent portovenous phase abdominal CT (fixed duration, February-November 2018; fixed rate, January-July 2020) with 1.22 mL/kg iohexol 350 were included. Subjects with liver, kidney or heart disease were excluded. The number of subjects and injection protocols were as follows: fixed duration arm, 56 women, 60 men, 35 s injection duration; fixed rate arm, 66 women, 62 men, 3 mL/s injection rate. Liver attenuation measurements were obtained from regions of interest on pre- and post-contrast images. Mean hepatic enhancement (MHE) and MHE normalized to iodine dose (MHE/I) were compared (unpaired t-tests and F-tests).

RESULTS

There was no statistically significant difference in age, weight, body mass index or CM dosing (p > 0.05). Enhancement indices were significantly lower in the fixed rate group as compared to the fixed duration group, as follows: MHE, 50.0 ± 12 vs. 54.8 ± 11 HU (p = 0.001); and MHE/I, 1.53 ± 0.43 vs. 1.66 ± 0.51 HU/g, (p = 0.04). However, there was no significant difference in the variances of MHE (p = 0.51) and MHE/I (p = 0.08).

CONCLUSION

A fixed CM injection duration yields a greater magnitude in hepatic enhancement indices than a fixed injection rate. Inter-patient variability in hepatic enhancement indices do not significantly differ between the two injection protocols.

Prospective multicenter study on personalized and optimized MDCT contrast protocols: results on liver enhancement

OBJECTIVE

To determine a personalized and optimized contrast injection protocol for a uniform and optimal diagnostic level of liver parenchymal enhancement, in a large patient population enrolled in a multicenter study.

METHODS

Six hundred ninety-two patients who underwent a standardized multi-phase liver CT examination were prospectively assigned to one contrast media (CM) protocol group: G1 (100 mL fixed volume, 37 gI); G2 (600 mgI/kg of total body weight (TBW)); G3 (750 mgI/kg of fat-free mass (FFM)), and G4 (600 mgI/kg of FFM). Change in liver parenchyma CT number between unenhanced and contrast-enhanced images was measured by two radiologists, on 3-mm pre-contrast and portal phase axial reconstructions. The enhancement histograms were compared across CM protocols, specifically according to a target diagnostic value of 50 HU. The total amount of iodine dose was also compared among protocols by median and interquartile range (IQR). The Kruskal-Wallis and Mann-Whitney U tests were used to assess significant differences (p < 0.005), as appropriate.

RESULTS

A significant difference (p < 0.001) was found across the groups with liver enhancement decreasing from median over-enhanced values of 77.0 (G1), 71.3 (G2), and 65.1 (G3) to a target enhancement of 53.2 HU for G4. Enhancement IQR was progressively reduced from 26.5 HU (G1), 26.0 HU (G2), and 17.8 HU (G3) to 14.5 HU (G4). G4 showed a median iodine dose of 26.0 gI, significantly lower (p < 0.001) than G3 (33.9 gI), G2 (38.8 gI), and G1 (37 gI).

CONCLUSIONS

The 600 mgI/kg FFM-based protocol enabled a diagnostically optimized liver enhancement and improved patient-to-patient enhancement uniformity, while significantly reducing iodine load.

KEY POINTS

• Consistent and clinically adequate liver enhancement is observed with personalized and optimized contrast injection protocol. • Fat-free mass is an appropriate body size parameter for correlation with liver parenchymal enhancement. • Diagnostic oncology follow-up liver CT examinations may be obtained using 600 mgI/kg of FFM.

Optimization of contrast medium volume for abdominal CT in oncologic patients: prospective comparison between fixed and lean body weight-adapted dosing protocols

Background

Patient body size represents the main determinant of parenchymal enhancement and by adjusting the contrast media (CM) dose to patient weight may be a more appropriate approach to avoid a patient over dosage of CM. To compare the performance of fixed-dose and lean body weight (LBW)-adapted contrast media dosing protocols, in terms of image quality and parenchymal enhancement.

Results

One-hundred cancer patients undergoing multiphasic abdominal CT were prospectively enrolled in this multicentric study and randomly divided in two groups: patients in fixed-dose group (n = 50) received 120 mL of CM while in LBW group (n = 50) the amount of CM was computed according to the patient’s LBW. LBW protocol group received a significantly lower amount of CM (103.47 ± 17.65 mL vs. 120.00 ± 0.00 mL, p < 0.001). Arterial kidney signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) and pancreatic CNR were significantly higher in LBW group (all p ≤ 0.004). LBW group provided significantly higher arterial liver, kidney, and pancreatic contrast enhancement index (CEI) and portal venous phase kidney CEI (all p ≤ 0.002). Significantly lower portal vein SNR and CNR were observed in LBW-Group (all p ≤ 0.020).

Conclusions

LBW-adapted CM administration for abdominal CT reduces the volume of injected CM and improves both image quality and parenchymal enhancement.

Personalized computed tomography - Automated estimation of height and weight of a simulated digital twin using a 3D camera and artificial intelligence

PURPOSE

 The aim of this study was to develop an algorithm for automated estimation of patient height and weight during computed tomography (CT) and to evaluate its accuracy in everyday clinical practice.

MATERIALS AND METHODS

 Depth images of 200 patients were recorded with a 3D camera mounted above the patient table of a CT scanner. Reference values were obtained using a calibrated scale and a measuring tape to train a machine learning algorithm that fits a patient avatar into the recorded patient surface data. The resulting algorithm was prospectively used on 101 patients in clinical practice and the results were compared to the reference values and to estimates by the patient himself, the radiographer and the radiologist. The body mass index was calculated from the collected values for each patient using the WHO formula. A tolerance level of 5 kg was defined in order to evaluate the impact on weight-dependent contrast agent dosage in abdominal CT.

RESULTS

 Differences between values for height, weight and BMI were non-significant over all assessments (p > 0.83). The most accurate values for weight were obtained from the patient information (R² = 0.99) followed by the automated estimation via 3D camera (R² = 0.89). Estimates by medical staff were considerably less precise (radiologist: R² = 0.78, radiographer: R² = 0.77). A body-weight dependent dosage of contrast agent using the automated estimations matched the dosage using the reference measurements in 65 % of the cases. The dosage based on the medical staff estimates would have matched in 49 % of the cases.

CONCLUSION

 Automated estimation of height and weight using a digital twin model from 3D camera acquisitions provide a high precision for protocol design in computer tomography.

KEY POINTS

  · Machine learning can calculate patient-avatars from 3D camera acquisitions.. · Height and weight of the digital twins are comparable to real measurements of the patients.. · Estimations by medical staff are less precise.. · The values can be used for calculation of contrast agent dosage..

CITATION FORMAT

· Geissler F, Heiß R, Kopp M et al. Personalized computed tomography - Automated estimation of height and weight of a simulated digital twin using a 3D camera and artificial intelligence. Fortschr Röntgenstr 2021; 193: 437 - 445.

Diagnostic accuracy of non-contrast quiescent-interval slice-selective (QISS) MRA combined with MRI-based vascular calcification visualization for the assessment of arterial stenosis in patients with lower extremity peripheral artery disease

OBJECTIVES

The proton density-weighted, in-phase stack-of-stars (PDIP-SOS) MRI technique provides calcification visualization in peripheral artery disease (PAD). This study sought to investigate the diagnostic accuracy of a combined non-contrast quiescent-interval slice-selective (QISS) MRA and PDIP-SOS MRI protocol for the detection of PAD, in comparison with CTA and digital subtraction angiography (DSA).

METHODS

Twenty-six prospectively enrolled PAD patients (70 ± 8 years) underwent lower extremity CTA and 1.5-T or 3-T PDIP-SOS/QISS MRI prior to DSA. Two readers rated image quality and graded stenosis (≥ 50%) on QISS MRA without/with calcification visualization. Sensitivity, specificity, and area under the curve (AUC) were calculated against DSA. Calcification was quantified and compared between MRI and non-contrast CT (NCCT) using paired t test, Pearson's correlation, and Bland-Altman analysis.

RESULTS

Image quality ratings were significantly higher for CTA compared to those for MRA (4.0 [3.0-4.0] and 3.0 [3.0-4.0]; p = 0.0369). The sensitivity and specificity of QISS MRA, QISS MRA with PDIP-SOS, and CTA for ≥ 50% stenosis detection were 85.4%, 92.2%, and 90.2%, and 90.3%, 93.2%, and 94.2%, respectively, while AUCs were 0.879, 0.928, and 0.923, respectively. A significant increase in AUC was observed when PDIP-SOS was added to the MRA protocol (p = 0.0266). Quantification of calcification showed significant differences between PDIP-SOS and NCCT (80.6 ± 31.2 mm³ vs. 88.0 ± 29.8 mm³; p = 0.0002) with high correlation (r = 0.77, p < 0.0001) and moderate mean of differences (- 7.4 mm³).

CONCLUSION

QISS MRA combined with PDIP-SOS MRI provides improved, CTA equivalent, accuracy for the detection of PAD, although its image quality remains inferior to CTA.

KEY POINTS

• Agreement in stenosis detection rate using non-contrast quiescent-interval slice-selective MRA compared to DSA improved when calcification visualization was provided to the readers. • An increase was observed in both sensitivity and specificity for the detection of ≥ 50% stenosis when MRI-based calcification assessment was added to the protocol, resulting in a diagnostic accuracy more comparable to CTA. • Quantification of calcification showed statistical difference between MRI and non-contrast CT; however, a high correlation was observed between the techniques.

Factors associated with missed and misinterpreted cases of pancreatic ductal adenocarcinoma

OBJECTIVES

To retrospectively examine US, CT, and MR imaging examinations of missed or misinterpreted pancreatic ductal adenocarcinoma (PDAC), and identify factors which may have confounded detection or interpretation.

METHODS

We reviewed 107 examinations in 66/257 patients (26%, mean age 73.7 years) diagnosed with PDAC in 2014 and 2015, with missed or misinterpreted imaging findings as determined by a prior study. For each patient, images and reports were independently reviewed by two radiologists, and in consensus, the following factors which may have confounded assessment were recorded: inherent tumor factors, concurrent pancreatic pathology, technical limitations, and cognitive biases. Secondary signs of PDAC associated with each examination were recorded and compared with the original report to determine which findings were missed.

RESULTS

There were 66/107 (62%) and 49/107 (46%) cases with missed and misinterpreted imaging findings, respectively. A significant number of missed tumors were < 2 cm (45/107, 42%), isoattenuating on CT (32/72, 44%) or non-contour deforming (44/107, 41%). Most (29/49, 59%) misinterpreted examinations were reported as uncomplicated pancreatitis. Almost all examinations (94/107, 88%) demonstrated secondary signs; pancreatic duct dilation was the most common (65/107, 61%) and vascular invasion was the most commonly missed 35/39 (90%). Of the CT and MRIs, 28 of 88 (32%) had suboptimal contrast dosing. Inattentional blindness was the most common cognitive bias, identified in 55/107 (51%) of the exams.

CONCLUSION

Recognizing pitfalls of PDAC detection and interpretation, including intrinsic tumor features, secondary signs, technical factors, and cognitive biases, can assist radiologists in making an early and accurate diagnosis.

KEY POINTS

• There were 66/107 (62%) and 49/107 (46%) cases with missed and misinterpreted imaging findings, respectively, with tumoral, technical, and cognitive factors leading to the misdiagnosis of pancreatic ductal adenocarcinoma. • The majority (29/49, 59%) of misinterpreted cases of pancreatic ductal adenocarcinoma were mistaken for pancreatitis, where an underlying mass or secondary signs were not appreciated due to inflammatory changes. • The most common missed secondary sign of pancreatic ductal adenocarcinoma was vascular encasement, missed in 35/39 (90%) of cases, indicating the importance of evaluating the peri-pancreatic vasculature.

Optimization of Pediatric Body CT Angiography: What Radiologists Need to Know

OBJECTIVE. Pediatric CT angiography (CTA) presents unique challenges compared with adult CTA. Because of the ionizing radiation exposure, CTA should be used judiciously in children. The pearls offered here are observations gleaned from the authors' experience in the use of pediatric CTA. We also present some potential follies to be avoided. CONCLUSION. Understanding the underlying principles and paying meticulous attention to detail can substantially optimize dose and improve the diagnostic quality of pediatric CTA.

Dosing Iodinated Contrast Media According to Lean Versus Total Body Weight at Abdominal CT: A Stratified Randomized Controlled Trial

RATIONALE AND OBJECTIVES

To compare the magnitude and interpatient variability in normalized mean hepatic enhancement (MHE) indices when dosing contrast media (CM) according to total body weight (TBW) and lean body weight (LBW).

MATERIALS AND METHODS

This ethics-approved stratified randomized controlled study allocated 280 outpatients for abdominal Computed Tomography (CT) between February-November 2018 to TBW- or LBW-dosing using computer-generated tables. CTs were acquired in portal venous phase after fixed 35-second injection of Iohexol 350. Patients with missing precontrast image, incorrect dose, or chronic kidney, liver or heart disease were excluded. The number of included patients and CM doses were: TBW arm, 51 women and 60 men, 1.22 mL/kg; LBW arm, 59 women, 1.66 mL/kg LBW, and 59 men, 1.52 mL/kg LBW. Liver attenuations were obtained from regions of interest. Values and standard deviations in MHE indices normalized to iodine dose (MHE/I) and iodine dose per kg TBW (aMHE = MHE/[I/TBW]) were compared (unpaired t tests and F-tests).

RESULTS

Cohorts were similar in age, sex, TBW, and LBW. TBW groups received more CM than LBW groups: men, 106.5 ± 20 versus 98.4 ± 11 mL, p = 0.007; women, 93.7 ± 20 versus 77.5 ± 11 mL, p < 0.0001. TBW and LBW groups showed no significant difference in MHE/I (women, 1.75 ± 0.5 versus 1.86 ± 0.6 HU/g, p = 0.31; men, 1.53 ± 0.4 versus 1.52 ± 0.4 HU/g, p = 0.90) or aMHE (women, 0.03 ± 0.01 versus 0.03 ± 0.01 HU/g/kg, p = 0.25; men, 0.02 ± 0.01 versus 0.02 ± 0.01 HU/g/kg, p = 0.52). Variances in MHE/I and aMHE were not significantly different for all groups (p > 0.05).

CONCLUSION

TBW- and LBW-based CM dosing yield a similar magnitude and interpatient variability in normalized MHE indices at routine abdominal CT.

State of the art of coronary computed tomography angiography

OBJECTIVES

The aim of this paper is to evaluate contrast media (CM) bolus geometry and opacification patterns in the coronary arteries with particular focus on patient, scanner and safety considerations during coronary computed tomography angiography (CCTA).

KEY FINDINGS

The rapid evolution of computed tomography (CT) technology has seen this imaging modality challenge conventional coronary angiography in the evaluation of coronary artery disease. Increases in spatial and temporal resolutions have enabled CCTA to become the modality of choice when evaluating the coronary vascular tree as an alternative in the diagnostic algorithm for acute chest pain. However, these new technologic improvements in scanner technology have imposed new challenges for the optimisation of CM delivery and image acquisition strategies.

CONCLUSION

Understanding basic CM-imaging principles is essential for designing optimal injection protocols according to each specific clinical scenario, independently of scanner technology.

IMPLICATIONS FOR PRACTICE

With rapid advances in CT scanner technology including faster scan acquisitions, the risk of poor opacification of coronary vasculature increases significantly. Therefore, awareness of CM delivery protocols is paramount to consistently provide optimal image quality at a low radiation dose.

False-Negative Low Tube Voltage Coronary CT Angiography: High Intravascular Attenuation at Coronary CT Angiography Can Mask Calcified Plaques

PURPOSE

To determine the impact of low tube voltage coronary CT angiography on detection of subclinical atherosclerosis.

MATERIALS AND METHODS

Retrospective sampling of an emergency department coronary CT angiography registry was performed. All patients in the registry underwent a noncontrast coronary artery calcium (CAC) scoring scan at 120 kV before coronary CT angiography. The study sample (n = 264) constituted patients with subclinical atherosclerosis (Coronary Artery Disease Reporting and Data System™ [CAD-RADS] 1 or 2) randomly mixed one-to-one with patients without atherosclerosis (CAD-RADS 0). The patients with coronary CT angiography performed at 70-90 kV were considered the low tube voltage group (n = 159) and patients with coronary CT angiography performed at 100-120 kV were considered the standard tube voltage group (n = 105). The number of coronary plaques and overall CAD-RADS classification (per patient) were evaluated twice: initially, by reading coronary CT angiography alone, and then, by coronary CT angiography in combination with a CAC scan. Considering the combined reading (CT angiography plus CAC scan) as the reference standard, the performance of coronary CT angiography alone was assessed for plaque detection and appropriate CAD-RADS (per patient) classification. The comparisons were made between the low tube voltage and standard tube voltage groups by using a Fisher exact test and χ2 test for proportions and a Mann-Whitney test and Kruskal-Wallis test for means.

RESULTS

In total, 455 plaques were identified in 118 patients (70 of 159 patients in the low tube voltage group; 48 of 105 in the standard tube voltage group). When reading coronary CT angiographic images alone, 97 of 455 (21%) plaques were missed that led to an incorrect CAD-RADS classification in 16 of 264 (6%) studies (interpreted as CAD-RADS 0 instead of CAD-RADS 1 or 2). Missed plaques were significantly more frequent in the low tube voltage group versus the standard tube voltage group (41% [85 of 206] vs 5% [12 of 249], respectively; P < .001). Incorrect CAD-RADS classification was also seen more commonly in the low tube voltage group (8.8% [14 of 159] vs 2% [two of 105]; P = .01), typically at low plaque burden (median CAC score, 1; range, 1-4). Calcified plaques that appeared isodense to luminal contrast material attenuation were seen more frequently in the low tube voltage group compared with the standard tube voltage group (20% [32 of 159] vs 7.6% [eight of 105], respectively; P = .005).

CONCLUSION

Coronary artery plaques may be missed at low tube voltage coronary CT angiographic examination performed without a concomitant CAC scan.© RSNA, 2019Supplemental material is available for this article.See also the commentary by Truong in this issue.

Current Imaging Standards for Nonmetastatic Benign and Malignant Liver Tumors

The accurate diagnosis of a liver mass can usually be established with a thorough history, examination, laboratory inquiry, and imaging. The necessity of a liver biopsy to determine the nature of a liver mass is rarely necessary. Contrast-enhanced computed tomography and magnetic resonance are the standard of care for diagnosing liver lesions and high-quality imaging should be performed before performing a biopsy. This article discusses current consensus guidelines for imaging of liver masses, as well as masses found on surveillance imaging. The ability to accurately characterize lesions requires proper use and understanding of the technology and expert interpretation.

Cross-sectional imaging of congenital pulmonary artery anomalies

Congenital pulmonary artery (PA) anomalies comprise a rare and heterogeneous spectrum of disease, ranging from abnormal origins to complete atresia. They may present in early infancy or more insidiously in adulthood, often in association with congenital heart disease such as tetralogy of Fallot or other syndromes. In recent years, cross-sectional imaging, including computed tomography (CT) and magnetic resonance imaging (MRI), has become widely utilized for the noninvasive assessment of congenital PA diseases, supplementing echocardiography and at times supplanting invasive angiography. In this article, modern CT and MRI techniques for imaging congenital PA disorders are summarized. The key clinical features, cross-sectional imaging findings, and treatment options for the most commonly encountered entities are then reviewed. Emphasis is placed on the ever-growing role of cross-sectional imaging options in facilitating early and accurate diagnosis and tailored treatment.

Volume Computed Tomography Perfusion Imaging: Evaluation of the Significance in Oncologic Follow-up of Metastasizing Renal Cell Carcinoma in the Early Period of Targeted Therapy - Preliminary Results

INTRODUCTION

The aim of this study was to assess the significance of volume computed tomography perfusion imaging of metastasizing renal cell carcinoma (mRCC) in the early period after the initiation of targeted therapy.

METHODS

Blood flow (BF), blood volume, and clearance (CL) were calculated in 10 patients with histologically verified mRCC before and 1 month after initiation of targeted therapy using compartmental analysis algorithms. In addition, the longest diameter of tumor was measured for both time points and compared. Correlation test was performed between perfusion parameters and size changes with time to progression (TTP).

RESULTS

Blood flow and CL were significantly lower after therapy initiation, whereas blood volume and the long diameter remained unchanged. Median values before and after 4 weeks of therapy were 144.2 versus 99.4 mL/min/100 mL for BF (P = 0.009) and 115.5 versus 46.8 mL/min/100 mL for CL (P = 0.007). Changes in BF and CL showed very strong negative correlation with TTP (r = -0.838, P = 0.009 and r = -0.826, P = 0.011, respectively).

CONCLUSIONS

Our preliminary study results indicate that volume computed tomography perfusion may assess targeted therapy response of mRCC earlier than the currently used Response Evaluation Criteria in Solid Tumors. In addition, changes in BF and CL may be a promising parameter for prediction of TTP.

Contrast dose reduction with shortened injection durations in coronary CT angiography on 16-cm Wide-detector CT scanner

OBJECTIVES:

To investigate the use of shortened contrast injection with late triggering in coronary CT angiography (CCTA) for decreasing contrast dose and maintaining image quality.

METHODS:

106 patients for CCTA on a 16-cm wide-detector CT were prospectively enrolled into groups A (n = 50) and B (n = 56) randomly. Patient weight-dependent contrast medium (Iopamiro, 370 mgI ml-1) at dose rate of 25 mgI/kg/s was used with 8 s and the standard 10 s injection time in groups A and B, respectively. CT values of the aortic sinus (AS), right coronary artery, left anterior descending and left circumflex at the proximal, middle and distal segments were measured and compared. Subjective image quality was evaluated and analyzed with Fisher exact test. Contrast dose, injection rate and enhancement duration (between the start of enhancement in AS and scan finish) were also compared.

RESULTS:

There was no difference in the injection rate and enhancement duration between the two groups (p > 0.05), while the total contrast dose in group A (36.2 ± 5.7 ml) was significantly lower than in group B (46.4 ± 6.3 ml) (p < 0.001). There was no difference for CT values in all major coronary vessels between the two groups and no difference in subjective image quality scores (all p > 0.05).

CONCLUSION:

It is feasible to shorten contrast injection to 8 s in CCTA on wide-detector CT systems to significantly reduce contrast dosage, maintain adequate enhancement and reduce contrast-related artifacts.

ADVANCES IN KNOWLEDGE:

(1) Coronary CT angiography (CCTA) scans with shortened contrast medium injection duration and late triggering are feasible with a 16-cm wide-detector CT system (2) Compared with the conventional CCTA with 10 s contrast injection duration, the new contrast injection protocol of using shortened injection duration (to 8 s) and late triggering reduces contrast dose to 36.2 ml, while maintaining adequate enhancement in vessels and reducing contrast-related artifacts.

Contrast-enhanced computed tomography may be helpful for characterizing and staging canine gastric tumors

In humans, computed tomography (CT) is a widely performed technique for the diagnosis and staging of gastric tumors. The purpose of this retrospective case series study was to describe CT findings in a group of dogs with confirmed gastric tumors. For each included dog, the following CT parameters were recorded: gastric tumor location, tumor shape, gastric involvement pattern, tumor enhancement pattern in early and late phases, presence and location of lymphadenopathy, gastric tumor attenuation values, attenuation values of enlarged lymph nodes, maximum short-axis diameter (mm) of enlarged lymph node, maximum long-axis diameter (mm) of enlarged lymph node, and short-axis diameter to long-axis diameter ratio (short axis/long axis). A total of 16 dogs met inclusion criteria and had the following final diagnoses: five lymphoma, six adenocarcinoma, three inflammatory polyps, and two leiomyoma. In the early- and delayed-phase postcontrast images, the mean CT attenuation value for lymphoma was lower than that of other gastric tumors. Lymphadenopathy was widespread in lymphomas and regional in adenocarcinomas. Lymphadenopathy was not detected in leiomyomas. Lymph node measurements in lymphoma were larger than lymph node measurements in adenocarcinoma. Although there were overlapping findings for the different types of gastric tumors, contrast-enhanced CT provided helpful information for characterizing gastric tumors based on the following criteria: early and late enhancement patterns, the site of origin of the mass lesion, and extent of local invasion and distant metastases. Lymphoma should be considered for canine gastric tumors with low mean attenuation values during early- and delayed-phase postcontrast images, and widespread, bulky, and rounded lymphadenopathy.

Contrast Administration in CT: A Patient-Centric Approach

Patient-centric care has garnered the attention of the radiology community. The authors describe a patient-centric approach to iodinated contrast administration designed to optimize the diagnostic yield of contrast-enhanced CT while minimizing patient iodine load and exposure to ionizing radiation, thereby enhancing patient safety while providing reasonable diagnostic efficacy. Patient-centric CT hardware settings and contrast media administration are important considerations for clinical CT quality and safety.

Pancreatic adenocarcinoma: cross-sectional imaging techniques

Pancreatic adenocarcinoma is a common malignancy that has a poor prognosis. Imaging is vital in its detection, staging, and management. Although a variety of imaging techniques are available, MDCT is the preferred imaging modality for staging and assessing the resectability of pancreatic adenocarcinoma. MR also has an important adjunct role, and may be used in addition to CT or as a problem-solving tool. A dedicated pancreatic protocol should be acquired as a biphasic technique optimized for the detection of pancreatic adenocarcinoma and to allow accurate local and distant disease staging. Emerging techniques like dual-energy CT and texture analysis of CT and MR images have a great potential in improving lesion detection, characterization, and treatment monitoring.

Current Radiographic Iodinated Contrast Agents

Millions of radiologic examinations requiring the use of iodinated contrast are performed yearly in North America. Triiodobenzoic acid, the contrast agent molecule currently in use, is a benzene ring covalently bonded to the 3 iodine atoms. Iodinated contrast media can be divided in 4 categories: ionic monomers, ionic dimers, nonionic monomer, and nonionic dimers. Currently, second- and third-generation nonionic low-osmolar and iso-osmolar contrast media are used in clinical practice. The search for a safer and more effective iodinated contrast agents remains an ongoing challenge and important research topic.

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.

Noise indices adjusted to body mass index and an iterative reconstruction algorithm maintain image quality on low-dose contrast-enhanced liver CT

OBJECTIVES

Since body mass index (BMI) affects medical imaging quality or noise due to penetration of the radiation through bodies with varying sizes, this study aims to investigate and determine the optimal BMI-adjusted noise index (NI) setting on the contrast-enhanced liver CT scans obtained using 3D Smart mA technology with adaptive statistical iterative reconstruction (ASIR 2.0) algorithm.

MATERIALS AND METHODS

A total of 320 patients who had contrast-enhanced liver CT scans were divided into two equal-sized groups: A (18.5 kg/m2≤BMI<24.9 kg/m2) and B (24.9 kg/m2 ≤ BMI ≤34.9 kg/m2). The two groups were randomly divided into four subgroups with an NI of 11, 13, 15, and 17. All images were reconstructed with 50% ASIR 2.0. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated after the late arterial, portal venous, and equilibrium phases were completed. Images were evaluated by two radiologists using a subjective 0 -5 scale. Mean CT dose index of volume, dose-length product, and effective dose (ED) were calculated and compared using one-way ANOVA.

RESULTS

In group A, the best-quality images obtained at the lowest ED were scanned at an NI of 15 in the late arterial phase, and at an NI of 17 in the portal venous and equilibrium phases. In group B, the best results were obtained at an NI of 13 in the late arterial phase, and at an NI of 15 in the portal venous and equilibrium phases.

CONCLUSION

Adjusting NI and iterative reconstruction algorithm based on body mass index can help improve image quality on contrast-enhanced liver CT scans, even at low radiation dose.

Multidetector computer tomography in the pancreatic adenocarcinoma assessment: an update

Ductal adenocarcinoma of the pancreas is one of the most aggressive forms of cancer, with only a minority of cases being resectable at the moment of their diagnosis. The accurate detection and characterization of pancreatic carcinoma is very important for patient management. Multidetector-row computed tomography (MDCT) has become the cross-sectional modality of choice in the diagnosis, staging, treatment planning, and follow-up of patients with pancreatic tumors. However, approximately 11% of ductal adenocarcinomas still remain undetected at MDCT because of the lack of attenuation gradient between the lesion and the adjacent pancreatic parenchyma. In this systematic literature review we investigate the current evolution of the CT technique, limitations, and perspectives in the evaluation of pancreatic carcinoma.

Dual Energy CT (DECT) Monochromatic Imaging: Added Value of Adaptive Statistical Iterative Reconstructions (ASIR) in Portal Venography

OBJECTIVE

To investigate the effect of the adaptive statistical iterative reconstructions (ASIR) on image quality in portal venography by dual energy CT (DECT) imaging.

MATERIALS AND METHODS

DECT scans of 45 cirrhotic patients obtained in the portal venous phase were analyzed. Monochromatic images at 70keV were reconstructed with the following 4 ASIR percentages: 0%, 30%, 50%, and 70%. The image noise (IN) (standard deviation, SD) of portal vein (PV), the contrast-to-noise-ratio (CNR), and the subjective score for the sharpness of PV boundaries, and the diagnostic acceptability (DA) were obtained. The IN, CNR, and the subjective scores were compared among the four ASIR groups.

RESULTS

The IN (in HU) of PV (10.05±3.14, 9.23±3.05, 8.44±2.95 and 7.83±2.90) decreased and CNR values of PV (8.04±3.32, 8.95±3.63, 9.80±4.12 and 10.74±4.73) increased with the increase in ASIR percentage (0%, 30%, 50%, and 70%, respectively), and were statistically different for the 4 ASIR groups (p<0.05). The subjective scores showed that the sharpness of portal vein boundaries (3.13±0.59, 2.82±0.44, 2.73±0.54 and 2.07±0.54) decreased with higher ASIR percentages (p<0.05). The subjective diagnostic acceptability was highest at 30% ASIR (p<0.05).

CONCLUSIONS

30% ASIR addition in DECT portal venography could improve the 70 keV monochromatic image quality.

Contrast medium administration and image acquisition parameters in renal CT angiography: what radiologists need to know

Over the last decade, exponential advances in computed tomography (CT) technology have resulted in improved spatial and temporal resolution. Faster image acquisition enabled renal CT angiography to become a viable and effective noninvasive alternative in diagnosing renal vascular pathologies. However, with these advances, new challenges in contrast media administration have emerged. Poor synchronization between scanner and contrast media administration have reduced the consistency in image quality with poor spatial and contrast resolution. Comprehensive understanding of contrast media dynamics is essential in the design and implementation of contrast administration and image acquisition protocols. This review includes an overview of the parameters affecting renal artery opacification and current protocol strategies to achieve optimal image quality during renal CT angiography with iodinated contrast media, with current safety issues highlighted.

Low-volume contrast medium protocol for comprehensive cardiac and aortoiliac CT assessment in the context of transcatheter aortic valve replacement

RATIONALE AND OBJECTIVES

To investigate the diagnostic performance of a comprehensive computed tomography (CT) protocol for both cardiac and aortoiliac evaluation of patients considered for transcatheter aortic valve replacement (TAVR) using a single, low-volume contrast medium (CM) injection.

MATERIALS AND METHODS

Forty-four TAVR candidates were retrospectively analyzed. All underwent retrospectively electrocardiogram-gated cardiac CT followed by high-pitch CT angiography of the aortoiliac vasculature using one of two single injection protocols of 320 mgI/mL iodine CM: group A (n = 22), iodine delivery rate-based (1.28 gI/s), 60-mL CM volume, 4.0 mL/s flow rate; group B (n = 22), clinical routine protocol, 100-mL CM volume, 4.0 mL/s flow rate. Mean arterial attenuation, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were calculated. Subjective image quality was assessed.

RESULTS

Aortic root and iliofemoral dimensions could be analyzed in all cases. Patient characteristics showed no significant differences. Mean attenuation at the levels of the aortic root (285.8 ± 83.0 HU vs 327.5 ± 70.8 HU, P = .080) and the iliofemoral access route (256.8 ± 88.5 HU vs 307.5 ± 93.2 HU, P = .071), as well as SNR and CNR were nonsignificantly lower in group A compared to group B. Subjective image quality was equivalent.

CONCLUSIONS

In multimorbid TAVR patients, the performance of a combined CT protocol using a single low-volume CM bolus is feasible with maintained image quality compared to a standard protocol.

Effect of Right-Sided Versus Left-Sided Contrast Injection on Intra-arterial Opacification Characteristics of Head and Neck Computed Tomography Angiograms and Interactions With Patient Sex, Weight, and Cardiac Output

OBJECTIVE

The aims of this study were to support the standard clinical assumption that preferential right-sided injection (RSI) over left-sided injection (LSI) results in improved head and neck computed tomography angiograms and to determine which patients most benefit from RSIs.

METHODS

Head and neck computed tomography angiograms of 453 RSIs and 419 LSIs were included. Interactions between injection side, age, weight, body mass index, and left ventricular ejection fraction with mean vessel Hounsfield units (HU) were compared. Statistical analysis was performed using 2-tailed Student t tests, Mann-Whitney U tests, and simple linear (SL) and multiple linear regressions.

RESULTS

Right-sided injection yielded higher HU for patients older than 40 years (eg, RSI of the right common carotid artery [RCCA] vs LSI of the RCCA; P < 0.01). Body mass index (eg, RCCA; r = -0.31, P < 0.01 [SL]) and weight (eg, RCCA; r = -0.39, P < 0.01 [SL]) were negatively correlated with HU. Female had higher HU (mean ± SE, +39.7 ± 7.6 HU; P < 0.01 [multiple linear]). Left ventricular ejection fraction had no interactions with injection side or HU.

CONCLUSIONS

The findings support preferential RSI in patients older than 40 years with higher body mass index and weight, particularly male.

Dynamic enhancement pattern of HCC smaller than 3 cm in diameter on gadoxetic acid-enhanced MRI: comparison with multiphasic MDCT

BACKGROUND & AIMS

The dynamic enhancement pattern of HCCs smaller than 3 cm in diameter on gadoxetic acid-enhanced magnetic resonance imaging (MRI) have not been extensively investigated. We aimed to evaluate the dynamic enhancement patterns of small HCCs (≤3 cm) on gadoxetic acid-enhanced magnetic resonance imaging (MRI) and compare enhancement patterns with multiphasic multidetector computed tomography (MDCT) based on tumour cellular differentiation and size.

METHODS

We retrospectively included 55 patients with 67 surgically confirmed small HCCs (≤3 cm) who underwent multiphasic MDCT and gadoxetic acid-enhanced MRI. Dynamic enhancement patterns were analysed according to tumour cellular differentiation and size. Hepatobiliary phase images were also analysed to assess their additional value.

RESULTS

The proportion of small HCCs demonstrating the typical enhancement pattern differed depending on tumour cellular differentiation on both MRI (P = 0.001) and MDCT (P = 0.001), but differed depending on tumour size only on CT (P = 0.008). Gadoxetic acid-enhanced MRI more sensitively depicted the typical enhancement pattern than CT for all tumours (P = 0.001), for moderately or poorly differentiated HCCs (P = 0.021) and for HCCs ≤2 cm (P = 0.001). 80% of tumours with atypical enhancement could be diagnosed as HCC based on tumour size and hepatobiliary phase images.

CONCLUSIONS

On both gadoxetic acid-enhanced MRI and multiphasic CT, the dynamic enhancement patterns of small HCCs (≤3 cm) differed according to tumour cellular differentiation. Gadoxetic acid-enhanced MRI more frequently demonstrated the typical HCC enhancement pattern than CT in small HCCs.

Pediatric CT quality management and improvement program

Modern CT is a powerful yet increasingly complex technology that continues to rapidly evolve; optimal clinical implementation as well as appropriate quality management and improvement in CT are challenging but attainable. This article outlines the organizational structure on which a CT quality management and improvement program can be built, followed by a discussion of common as well as pediatric-specific challenges. Organizational elements of a CT quality management and improvement program include the formulation of clear objectives; definition of the roles and responsibilities of key personnel; implementation of a technologist training, coaching and feedback program; and use of an efficient and accurate monitoring system. Key personnel and roles include a radiologist as the CT director, a qualified CT medical physicist, as well as technologists with specific responsibilities and adequate time dedicated to operation management, CT protocol management and CT technologist education. Common challenges in managing a clinical CT operation are related to the complexity of newly introduced technology, of training and communication and of performance monitoring. Challenges specific to pediatric patients include the importance of including patient size in protocol and dose considerations, a lower tolerance for error in these patients, and a smaller sample size from which to learn and improve.