Detection of hepatic portal venous gas: its clinical impact and outcome

The clinical impact and outcome of a rare radiographic finding of hepatic portal venous gas (HPVG) as well as the effectiveness of computed tomography (CT), CT scanogram, and conventional radiography in the detection of HPVG were retrospectively analyzed. CT scans, CT scanogram, and plain film radiographs of 11 patients with HPVG were reviewed and compared with their medical records and surgical and pathology reports. Eight of the 11 patients underwent plain film radiographs 1day before or after the CT scan. HPVG was detected at CT in all 11 patients, on CT scanogram in three (3 of 11, 27.3%), and on plain films in one (one of eight, 12.5%). In nine of 11 patients (81.8%), CT revealed an associated pneumatosis intestinalis. In six of the 11 patients (54.6%), acute mesenteric ischemia was the underlying disease for HPVG. Seven patients (63.6%) underwent emergency exploratory laparotomy. The mortality rate for HPVG alone was 27.3% (3 of 11) and for HPVG related to mesenteric bowel disease 50% (three of six). Acute mesenteric ischemia is the most common cause of HPVG, which continues to have a predictably higher mortality. CT is superior to CT scanograms and radiographs in the detection of HPVG and its underlying diseases and, therefore, should be used as the primary diagnostic too

Effect of varying injection rates of a saline chaser on aortic enhancement in CT angiography: phantom study

The effect of varying injection rates of a saline chaser on aortic enhancement in computed tomography (CT) angiography was determined. Single-level, dynamic CT images of a physiological flow phantom were acquired between 0 and 50 s after initiation of contrast medium injection. Four injection protocols were applied with identical contrast medium administration (150ml injected at 5ml/s). For baseline protocol A, no saline chaser was applied. For protocols B, C, and D, 50ml of saline was injected at 2.5ml/s, 5ml/s, and 10ml/s, respectively. Injecting the saline chaser at twice the rate as the contrast medium yielded significantly higher peak aortic enhancement values than injecting the saline at half or at the same rate as the contrast medium (P  0.05). In CT angiography, saline chaser injected at twice the rate as the contrast medium leads to increased peak aortic enhancement and saline chaser injected at half the rate tends towards prolonging peak aortic enhancement platea

Is body weight the most appropriate criterion to select patients eligible for low-dose pulmonary CT angiography? Analysis of objective and subjective image quality at 80kVp in 100 patients

The objective of this retrospective study was to assess image quality with pulmonary CT angiography (CTA) using 80kVp and to find anthropomorphic parameters other than body weight (BW) to serve as selection criteria for low-dose CTA. Attenuation in the pulmonary arteries, anteroposterior and lateral diameters, cross-sectional area and soft-tissue thickness of the chest were measured in 100 consecutive patients weighing less than 100kg with 80kVp pulmonary CTA. Body surface area (BSA) and contrast-to-noise ratios (CNR) were calculated. Three radiologists analyzed arterial enhancement, noise, and image quality. Image parameters between patients grouped by BW (group 1: 0-50kg; groups 2-6: 51-100kg, decadally increasing) were compared. CNR was higher in patients weighing less than 60kg than in the BW groups 71-99kg (P between 0.025 and <0.001). Subjective ranking of enhancement (P = 0.165-0.605), noise (P = 0.063), and image quality (P = 0.079) did not differ significantly across all patient groups. CNR correlated moderately strongly with weight (R = −0.585), BSA (R = −0.582), cross-sectional area (R = −0.544), and anteroposterior diameter of the chest (R = −0.457; P < 0.001 all parameters). We conclude that 80kVp pulmonary CTA permits diagnostic image quality in patients weighing up to 100kg. Body weight is a suitable criterion to select patients for low-dose pulmonary CT

Material differentiation in forensic radiology with single-source dual-energy computed tomography

The goal of this study was to investigate the use of dual-energy computed tomography (CT) in differentiating frequently encountered foreign material on CT images using a standard single-source CT scanner. We scanned 20 different, forensically relevant materials at two X-Ray energy levels (80 and 130kVp) on CT. CT values were measured in each object at both energy levels. Intraclass correlation coefficient (ICC) was used to determine intra-reader reliability. Analysis of variance (ANOVA) was performed to assess significance levels between X-Ray attenuation at 80 and 130kVp. T test was used to investigate significance levels between mean HU values of individual object pairings at single energy levels of 80 and 130kVp, respectively. ANOVA revealed that the difference in attenuation between beam energies of 80kVp compared to 130kVp was statistically significant (p<0.005) for all materials except brass and lead. ICC was excellent at 80kVp (0.999, p<0.001) and at 130kVp (0.998, p<0.001). T test showed that using single energy levels of 80 and 130kVp respectively 181/190 objects pairs could be differentiated from one another based on HU measurements. Using the combined information from both energy levels, 189/190 object pairs could be differentiated. Scanning with different energy levels is a simple way to apply dual-energy technique on a regular single-energy CT and improves the ability to differentiate foreign bodies with CT, based on their attenuation value

Whole-body computed tomography for multiple traumas using a triphasic injection protocol

To evaluate a triphasic injection protocol for whole-body multidetector computed tomography (MDCT) in patients with multiple trauma. Fifty consecutive patients (41 men) were examined. Contrast medium (300mg/mL iodine) was injected starting with 70mL at 3mL/s, followed by 0.1mL/s for 8s, and by another bolus of 75mL at 4mL/s. CT data acquisition started 50s after the beginning of the first injection. Two experienced, blinded readers independently measured the density in all major arteries, veins, and parenchymatous organs. Image quality was assessed using a five-point ordinal rating scale and compared to standard injection protocols [n = 25 each for late arterial chest, portovenous abdomen, and MDCT angiography (CTA)]. With the exception of the infrarenal inferior caval vein, all blood vessels were depicted with diagnostic image quality using the multiple-trauma protocol. Arterial luminal density was slightly but significantly smaller compared to CTA (P < 0.01). Veins and parenchymatous organs were opacified significantly better compared to all other protocols (P < 0.01). Arm artifacts reduced the density of spleen and liver parenchyma significantly (P < 0.01). Similarly high image quality is achieved for arteries using the multiple-trauma protocol compared to CTA, and parenchymatous organs are depicted with better image quality compared to specialized protocols. Arm artifacts should be avoide

Comparability of Pulmonary Nodule Size Measurements among Different Scanners and Protocols: Should Diameter Be Favorized over Volume?

BACKGROUND: To assess the impact of the lung cancer screening protocol recommended by the European Society of Thoracic Imaging (ESTI) on nodule diameter, volume, and density throughout different computed tomography (CT) scanners. METHODS: An anthropomorphic chest phantom containing fourteen different-sized (range 3-12 mm) and CT-attenuated (100 HU, -630 HU and -800 HU, termed as solid, GG1 and GG2) pulmonary nodules was imaged on five CT scanners with institute-specific standard protocols (P$_{S}$) and the lung cancer screening protocol recommended by ESTI (ESTI protocol, P$_{E}$). Images were reconstructed with filtered back projection (FBP) and iterative reconstruction (REC). Image noise, nodule density and size (diameter/volume) were measured. Absolute percentage errors (APEs) of measurements were calculated. RESULTS: Using P$_{E}$, dosage variance between different scanners tended to decrease compared to P$_{S}$, and the mean differences were statistically insignificant (p = 0.48). P$_{S}$ and P$_{E(REC)}$ showed significantly less image noise than P$_{E(FBP)}$ (p < 0.001). The smallest size measurement errors were noted with volumetric measurements in P$_{E(REC)}$ and highest with diametric measurements in P$_{E(FBP)}$. Volume performed better than diameter measurements in solid and GG1 nodules (p < 0.001). However, in GG2 nodules, this could not be observed (p = 0.20). Regarding nodule density, REC values were more consistent throughout different scanners and protocols. CONCLUSION: Considering radiation dose, image noise, nodule size, and density measurements, we fully endorse the ESTI screening protocol including the use of REC. For size measurements, volume should be preferred over diameter

An education and training programme for radiological institutes: impact on the reduction of the CT radiation dose

Objectives: To establish an education and training programme for the reduction of CT radiation doses and to assess this programme's efficacy. Methods: Ten radiological institutes were counselled. The optimisation programme included a small group workshop and a lecture on radiation dose reduction strategies. The radiation dose used for five CT protocols (paranasal sinuses, brain, chest, pulmonary angiography and abdomen) was assessed using the dose-length product (DLP) before and after the optimisation programme. The mean DLP values were compared with national diagnostic reference levels (DRLs). Results: The average reduction of the DLP after optimisation was 37% for the sinuses (180 vs. 113mGycm, P < 0.001), 9% for the brain (982 vs. 896mGycm, P < 0.05), 24% for the chest (425 vs. 322mGycm, P < 0.05) and 42% for the pulmonary arteries (352 vs. 203mGycm, P < 0.001). No significant change in DLP was found for abdominal CT. The post-optimisation DLP values of the sinuses, brain, chest, pulmonary arteries and abdomen were 68%, 10%, 20%, 55% and 15% below the DRL, respectively. Conclusions: The education and training programme for radiological institutes is effective in achieving a substantial reduction in CT radiation dos

Prospective randomised comparison of diagnostic confidence and image quality with normal-dose and low-dose CT pulmonary angiography at various body weights

Objectives: To find a threshold body weight (BW) below 100kg above which computed tomography pulmonary angiography (CTPA) using reduced radiation and a reduced contrast material (CM) dose provides significantly impaired quality and diagnostic confidence compared with standard-dose CTPA. Methods: In this prospectively randomised study of 501 patients with suspected pulmonary embolism and BW <100kg, 246 were allocated into the low-dose group (80kVp, 75ml CM) and 255 into the normal-dose group (100kVp, 100ml CM). Contrast-to-noise ratio (CNR) in the pulmonary trunk was calculated. Two blinded chest radiologists independently evaluated subjective image quality and diagnostic confidence. Data were compared between the normal-dose and low-dose groups in five BW subgroups. Results: Vessel attenuation did not differ between the normal-dose and low-dose groups within each BW subgroup (P = 1.0). The CNR was higher with the normal-dose compared with the low-dose protocol (P < 0.006) in all BW subgroups except for the 90-99kg subgroup (P = 0.812). Subjective image quality and diagnostic confidence did not differ between CT protocols in all subgroups (P between 0.960 and 1.0). Conclusions: Subjective image quality and diagnostic confidence with 80kVp CTPA is not different from normal-dose protocol in any BW group up to 100kg. Key Points : • 80kVp CTPA is safe in patients weighing <100kg • Reduced radiation and iodine dose still provide high vessel attenuation • Image quality and diagnostic confidence with low-dose CTPA is good • Diagnostic confidence does not deteriorate in obese patients weighing <100k

Combining automated attenuation-based tube voltage selection and iterative reconstruction: a liver phantom study

Objectives: To determine the value of combined automated attenuation-based tube-potential selection and iterative reconstructions (IRs) for optimising computed tomography (CT) imaging of hypodense liver lesions. Methods: A liver phantom containing hypodense lesions was imaged by CT with and without automated attenuation-based tube-potential selection (80, 100 and 120kVp). Acquisitions were reconstructed with filtered back projection (FBP) and sinogram-affirmed IR. Image noise and contrast-to-noise ratio (CNR) were measured. Two readers marked lesion localisation and rated confidence, sharpness, noise and image quality on a five-point scale (1 = worst, 5 = best). Results: Image noise was lower (31-52%) and CNR higher (43-102%) on IR than on FBP images at all tube voltages. On 100-kVp and 80-kVp IR images, confidence and sharpness were higher than on 120-kVp FBP images. Scores for image quality score and noise as well as sensitivity for 100-kVp IR were similar or higher than for 120-kVp FBP and lower for 80-kVp IR. Radiation dose was reduced by 26% at 100kVp and 56% at 80kVp. Conclusions: Compared with 120-kVp FBP images, the combination of automated attenuation-based tube-potential selection at 100kVp and IR provides higher image quality and improved sensitivity for detecting hypodense liver lesions in vitro at a dose reduced by 26%. Key Points: • Combining automated tube voltage selection/iterative CT reconstruction improves image quality. • Attenuation values remain stable on IR compared with FBP images. • Lesion detection was highest on 100-kVp IR images

Comparison of temporal evolution of computed tomography imaging features in COVID-19 and influenza infections in a multicenter cohort study

Purpose To compare temporal evolution of imaging features of coronavirus disease 2019 (COVID-19) and influenza in computed tomography and evaluate their predictive value for distinction. Methods In this retrospective, multicenter study 179 CT examinations of 52 COVID-19 and 44 influenza critically ill patients were included. Lung involvement, main pattern (ground glass opacity, crazy paving, consolidation) and additional lung and chest findings were evaluated by two independent observers. Additional findings and clinical data were compared patient-wise. A decision tree analysis was performed to identify imaging features with predictive value in distinguishing both entities. Results In contrast to influenza patients, lung involvement remains high in COVID-19 patients > 14 days after the diagnosis. The predominant pattern in COVID-19 evolves from ground glass at the beginning to consolidation in later disease. In influenza there is more consolidation at the beginning and overall less ground glass opacity (p = 0.002). Decision tree analysis yielded the following: Earlier in disease course, pleural effusion is a typical feature of influenza (p = 0.007) whereas ground glass opacities indicate COVID-19 (p = 0.04). In later disease, particularly more lung involvement (p < 0.001), but also less pleural (p = 0.005) and pericardial (p = 0.003) effusion favor COVID-19 over influenza. Regardless of time point, less lung involvement (p < 0.001), tree-in-bud (p = 0.002) and pericardial effusion (p = 0.01) make influenza more likely than COVID-19. Conclusions This study identified differences in temporal evolution of imaging features between COVID-19 and influenza. These findings may help to distinguish both diseases in critically ill patients when laboratory findings are delayed or inconclusive