C-arm flat-panel CT arthrography of the wrist and elbow: first experiences in human cadavers

Objective: To determine the optimal intra-articular iodine concentration for C-arm flat-panel computed tomography (FPCT) arthrography using advanced joint phantoms and to evaluate its application in human cadaveric wrists and elbows. Multi-detector (MD) CT served as the standard of reference. Materials and methods: Joint phantoms and 10 human cadaveric wrist and elbow joints were scanned with C-arm FPCT (5-s, 8-s, and 20-s runs) and standard MDCT using different and optimal concentrations of iodinated contrast material. CT numbers of contrast material, tissue, and noise were measured and contrast-to-noise ratios (CNR) calculated for quantitative analysis. Image and depiction of cartilage, bone, and soft tissues were rated. Radiation doses were compared. Results: In FPCT, iodine concentrations positively correlated with CT numbers and noise of contrast material and with radiation dose (r = 0.713-0.996, p < 0.05 each). At an iodine concentration of 45mg/ml, CNR of cartilage and soft tissues were highest for all FPCT acquisitions and higher than in MDCT. The 20-s FPCT run performed best for image quality and depiction of anatomical structures and was rated overall equal to MDCT (p = 0.857). Conclusion: The optimal iodine concentration for C-arm FPCT arthrography in this study is 45mg/ml, leading to superior CNR and image quality for an optimal FPCT protocol compared with standard MDCT arthrography in human cadaveric joint

Systematic analysis on the relationship between luminal enhancement, convolution kernel, plaque density, and luminal diameter of coronary artery stenosis: a CT phantom study

To systematically investigate into the relationships between luminal enhancement, convolution kernel, plaque density, and stenosis severity in coronary computed tomography (CT) angiography. A coronary phantom including 63 stenoses (stenosis severity, 10-90%; plaque densities, −100 to 1,000HU) was loaded with increasing solutions of contrast material (luminal enhancement, 0-700HU) and scanned in an anthropomorphic chest. CT data was acquired with prospective triggering using 64-section dual-source CT; reconstructions were performed with soft-tissue (B26f) and sharp convolution kernels (B46f). Two blinded and independent readers quantitatively assessed luminal diameter and CT number of plaque using electronic calipers. Measurement bias between phantom dimensions and CT measurements were calculated. Multivariate linear regression models identified predictors of bias. Inter- and intra-reader agreements of luminal diameter and CT number measurements were excellent (ICCs>0.91, p200HU. Measurement bias was significantly (p<0.01, each) correlated (ρ=0.37-55 and ρ=−0.70-85) with the differences between luminal enhancement and plaque density. In multivariate models, bias of luminal diameter assessment with CT was correlated with plaque density (β=0.09, p<0.05). Convolution kernel (β=−0.29 and −0.38), stenosis severity (β=−0.45 and −0.38), and luminal enhancement (β=−0.11 and −0.29) represented independent (p<0.05,each) predictors of measurement bias of luminal diameter and plaque number, respectively. Significant independent relationships exist between luminal enhancement, convolution kernel, plaque density, and luminal diameter, which have to be taken into account when performing, evaluating, and interpreting coronary CT angiograph

The impact of slice-reduced computed tomography on histogram-based densitometry assessment of lung fibrosis in patients with systemic sclerosis

Background To evaluate usability of slice-reduced sequential computed tomography (CT) compared to standard high-resolution CT (HRCT) in patients with systemic sclerosis (SSc) for qualitative and quantitative assessment of interstitial lung disease (ILD) with respect to (I) detection of lung parenchymal abnormalities, (II) qualitative and semiquantitative visual assessment, (III) quantification of ILD by histograms and (IV) accuracy for the 20%-cut off discrimination. Methods From standard chest HRCT of 60 SSc patients sequential 9-slice-computed tomography (reduced HRCT) was retrospectively reconstructed. ILD was assessed by visual scoring and quantitative histogram parameters. Results from standard and reduced HRCT were compared using non-parametric tests and analysed by univariate linear regression analyses. Results With respect to the detection of parenchymal abnormalities, only the detection of intrapulmonary bronchiectasis was significantly lower in reduced HRCT compared to standard HRCT (P=0.039). No differences were found comparing visual scores for fibrosis severity and extension from standard and reduced HRCT (P=0.051-0.073). All scores correlated significantly (P<0.001) to histogram parameters derived from both, standard and reduced HRCT. Significant higher values of kurtosis and skewness for reduced HRCT were found (both P<0.001). In contrast to standard HRCT histogram parameters from reduced HRCT showed significant discrimination at cut-off 20% fibrosis (sensitivity 88% kurtosis and skewness; specificity 81% kurtosis and 86% skewness; cut-off kurtosis ≤26, cut-off skewness ≤4; both P<0.001). Conclusions Reduced HRCT is a robust method to assess lung fibrosis in SSc with minimal radiation dose with no difference in scoring assessment of lung fibrosis severity and extension in comparison to standard HRCT. In contrast to standard HRCT histogram parameters derived from the approach of reduced HRCT could discriminate at a threshold of 20% lung fibrosis with high sensitivity and specificity. Hence it might be used to detect early disease progression of lung fibrosis in context of monitoring and treatment of SSc patients

Metal artefact reduction from dental hardware in carotid CT angiography using iterative reconstructions

Purpose: To determine the value of a metal artefact reduction (MAR) algorithm with iterative reconstructions for dental hardware in carotid CT angiography. Methods: Twenty-four patients (six of which were women; mean age 70 ± 12years) with dental hardware undergoing carotid CT angiography were included. Datasets were reconstructed with filtered back projection (FBP) and using a MAR algorithm employing normalisation and an iterative frequency-split (IFS) approach. Three blinded, independent readers measured CT attenuation values and evaluated image quality and degrees of artefacts using axial images, multi-planar reformations (MPRs) and maximal intensity projections (MIP) of the carotid arteries. Results: CT attenuation values of the internal carotid artery on images with metal artefacts were significantly higher in FBP (324 ± 104HU) datasets compared with those reconstructed with IFS (278 ± 114HU; P < 0.001) and with FBP on images without metal artefacts (293 ± 106HU; P = 0.006). Quality of IFS images was rated significantly higher on axial, MPR and MIP images (P < 0.05, each), and readers found significantly less artefacts impairing the diagnostic confidence of the internal carotid artery (P < 0.05, each). Conclusion: The MAR algorithm with the IFS approach allowed for a significant reduction of artefacts from dental hardware in carotid CT angiography, hereby increasing image quality and improving the accuracy of CT attenuation measurements. Key points: • CT angiography of the neck has proven value for evaluating carotid disease • Neck CT angiography images are often degraded by artefacts from dental implants • A metal artefact reduction algorithm with iterative reconstruction reduces artefacts significantly • Visualisation of the internal carotid artery is improve

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

Performance of turbo high-pitch dual-source CT for coronary CT angiography: first ex vivo and patient experience

Objectives: To evaluate image quality, maximal heart rate allowing for diagnostic imaging, and radiation dose of turbo high-pitch dual-source coronary computed tomographic angiography (CCTA). Methods: First, a cardiac motion phantom simulating heart rates (HRs) from 60-90bpm in 5-bpm steps was examined on a third-generation dual-source 192-slice CT (prospective ECG-triggering, pitch 3.2; rotation time, 250ms). Subjective image quality regarding the presence of motion artefacts was interpreted by two readers on a four-point scale (1, excellent; 4, non-diagnostic). Objective image quality was assessed by calculating distortion vectors. Thereafter, 20 consecutive patients (median, 50years) undergoing clinically indicated CCTA were included. Results: In the phantom study, image quality was rated diagnostic up to the HR75 bpm, with object distortion being 1mm or less. Distortion increased above 1mm at HR of 80-90bpm. Patients had a mean HR of 66bpm (47-78bpm). Coronary segments were of diagnostic image quality for all patients with HR up to 73bpm. Average effective radiation dose in patients was 0.6 ± 0.3mSv. Conclusions: Our combined phantom and patient study indicates that CCTA with turbo high-pitch third-generation dual-source 192-slice CT can be performed at HR up to 75bpm while maintaining diagnostic image quality, being associated with an average radiation dose of 0.6mSv. Key points : • CCTA is feasible with the turbo high-pitch mode. • Turbo high-pitch CCTA provides diagnostic image quality up to 73bpm. • The radiation dose of high-pitch CCTA is 0.6mSv on average

Perfusion CT best predicts outcome after radioembolization of liver metastases: a comparison of radionuclide and CT imaging techniques

Objective: To determine the best predictor for the response to and survival with transarterial radioembolisation (RE) with 90yttrium microspheres in patients with liver metastases. Methods: Forty consecutive patients with liver metastases undergoing RE were evaluated with multiphase CT, perfusion CT and 99mTc-MAA SPECT. Arterial perfusion (AP) from perfusion CT, HU values from the arterial (aHU) and portal venous phase (pvHU) CT, and 99mTc-MAA uptake ratio of metastases were determined. Morphologic response was evaluated after 4months and available in 30 patients. One-year survival was calculated with Kaplan-Meier curves. Results: We found significant differences between responders and non-responders for AP (P 20ml/100ml/min had a significantly (P = 0.01) higher 1-year survival, whereas an aHU value >55 HU did not discriminate survival (P = 0.12). The Cox proportional hazard model revealed AP as the only significant (P = 0.02) independent predictor of survival. Conclusion: Compared to arterial and portal venous enhancement and the 99mTc-MAA uptake ratio of liver metastases, the AP from perfusion CT is the best predictor of morphologic response to and 1-year survival with RE. Key Points : • Perfusion CT allows for calculation of the liver arterial perfusion. • Arterial perfusion of liver metastases differs between responders and non-responders to RE. • Arterial perfusion can be used to select patients responding to RE

Moderne Techniken zur Strahlendosisreduktion in der Computertomographie

Computed tomography (CT) is one of the most commonly performed imaging modalities in radiology. This is mainly the result of wide availability, robustness, and fast image acquisition. However, CT is associated with ionizing radiation to the patients. Various recent techniques help to reduce the radiation dose considerably. These include automated attenuation-based tube current modulation and automated selection of the tube voltage. In addition, iterative reconstruction techniques allow for a dramatic decrease in radiation dose while image quality can be maintained. Using all these techniques, it has become possible to perform a diagnostic CT examination of the lungs with a radiation dose that is comparable to that of a conventional chest X-ray. ie Computertomographie (CT) gehört zu den am häufigsten durchgeführten Untersuchungen in der Radiologie. Diese liefert rasch wertvolle diagnostische Informationen, ist jedoch mit ionisierender Röntgenstrahlung verbunden. Moderne Techniken in der Radiologie können die Strahlendosis der CT erheblich senken, ohne dabei die diagnostische Information der Untersuchung zu reduzieren. Hierzu gehören die automatische Modulation des Röhrenstroms und die automatische Anpassung der Röhrenspannung an die Konstitution des Patienten. Zusätzlich können iterative Bildrekonstruktionsverfahren verwendet werden, um die Bildqualität bei niedrigerer Strahlendosis konstant zu halten. Verwendet man all diese Techniken zur Dosisreduktion, ist es heutzutage möglich, eine CT der Lunge in diagnostischer Bildqualität mit einer Strahlendosis einer konventionellen Röntgenthorax-Aufnahme durchzuführen

Single-phase bilateral low dose contrast medium injection for diagnosing occlusions of the thoracic venous system: a case report

Occlusion of the thoracic venous system and/or occlusion of central venous catheters (CVC) of unknown cause can, in selected cases, require advanced imaging. Here, we describe a case study of a patient with a failing central dialysis catheter (CDC) which was diagnosed by computed tomography (CT) in connection with a single-phase bilateral low-dose contrast medium (CM) injection using only 3.6 g of iodine. By injecting a low CM dose, the risk of streak artifacts from first-pass of high intravascular concentrations of CM can be avoided. Therefore, the technique described here should be beneficial also to patients with normal renal function