Impact of Structured Reporting of Lower Extremity CT Angiography on Report Quality and Workflow Efficiency.

We assessed the effects of structured reporting (SR) of lower extremity CT angiography (CTA) on report quality and workflow efficiency compared with conventional reports (CR). Surveys were conducted at an academic radiology department before and after the introduction of an SR template. Participants (n = 39, 21) rated report quality and report creation effort (1: very dissatisfied/low to 10: very satisfied/high) and whether SR represents an improvement over CR (1: completely disagree to 5: completely agree). Four residents and two supervising radiologists created both CR and SR of 40 CTA examinations. Report creation time was measured and the factual accuracy of residents' reports was judged. Report completeness (median 8.0 vs. 7.0, p = 0.016) and clinical usefulness (7.0 vs. 4.0, p = 0.029) were rated higher for SR. Supervising radiologists found report clarity improved by SR (8.0 vs. 4.5, p = 0.029). Report creation effort was unchanged (7.0 vs. 6.0, p > 0.05). SR was considered an improvement over CR (median 4.0, IQR,3.0-5.0). Report supervision was shortened by SR (6.2 ± 2.0 min vs. 10.6 ± 3.5 min, p < 0.001) but total time for report creation remained unchanged (36.6 ± 12.8 min vs. 36.4 ± 11.0 min, p > 0.05). Factual accuracy of residents' SR was deemed higher (8.0/9.5 vs. 7.0/7.0, p = 0.006/ < 0.001). In conclusion, SR has the potential to improve report quality and workflow efficiency for lower extremity CTA.

Calcium-Based Imaging of the Spine at Dual-Layer CT and Evaluation of Vertebral Fractures in Multiple Myeloma.

PURPOSE: To evaluate the prediction of vertebral fractures in plasma cell dyscrasias using dual-layer CT (DLCT) with quantitative assessment of conventional CT image data (CI), calcium suppressed image data (CaSupp), and calculation of virtual calcium-only (VCa) image data. MATERIAL AND METHODS: Patients (n = 81) with the diagnosis of a plasma cell dyscrasia and whole-body DLCT at the time of diagnosis and follow-up were retrospectively enrolled. CI, CaSupp25, and CaSupp100 were quantitatively analyzed using regions of interest in the lumbar vertebral bodies and fractured vertebral bodies on baseline or follow-up imaging. VCa were calculated by subtraction (CaSupp100-CaSupp25), delineating bone only. Logistic regression analyses were performed to assess the possibility of imminent spine fractures. RESULTS: In 24 patients, new vertebral fractures were observed in the follow-up imaging. The possibility of new vertebral fractures was significant for baseline assessment of CT numbers in CI, CaSupp25, and VCa (p = 0.01, respectively), with a higher risk for new fractures in the case of lower CT numbers in CI (Odds ratio = [0.969; 0.994]) and VCa (Odds ratio = [0.978; 0.995]) and in the case of higher CT numbers in CaSupp 25 (Odds ratio 1.015 [1.006; 1.026]). Direct model comparisons implied that CT numbers in CaSupp 25 and VCa might show better fracture prediction than those in CI (R2 = 0.18 both vs. 0.15; AICc = 91.95, 91.79 vs. 93.62), suggesting cut-off values for CI at 103 HU (sensitivity: 54.2%; specificity: 82.5; AUC: 0.69), for VCa at 129 HU (sensitivity: 41.7%; specificity: 94.7; AUC: 0.72). CONCLUSIONS: Quantitative assessment with CaSupp and calculation of VCa is feasible to predict the vertebral fracture risk in MM patients. DLCT may prove useful in detecting imminent fractures.

Feasibility of Reduced Iodine Loads for Vascular Assessment Prior to Transcatheter Aortic Valve Implantation (TAVI) Using Spectral Detector CT.

Reduced iodine loads for computed tomography (CT)-based vascular assessment prior to transcatheter aortic valve implantation (TAVI) may be feasible in conjunction with a spectral detector CT scanner. This prospective single-center study considered 100 consecutive patients clinically referred for pre-TAVI CT. They were examined on a dual-layer detector CT scanner to obtain an ECG-gated cardiac scan and a non-ECG-gated aortoiliofemoral scan. Either a standard contrast media (SCM) protocol using 80 mL Iohexol 350 mgI/mL (iodine load: 28 gI) or a body-mass-index adjusted reduced contrast media (RCM) protocol using 40-70 mL Iohexol 350 mgI/mL (iodine load: 14-24.5 gI) were employed. Conventional images and virtual monoenergetic images at 40-80 keV were reconstructed. A threshold of 250 HU was set for sufficient attenuation along the arterial access pathway. A qualitative assessment used a five-point Likert scale. Sufficient attenuation in the thoracic aorta was observed for all patients in both groups using conventional images. In the abdominal, iliac, and femoral segments, sufficient attenuation was observed for the majority of patients when using virtual monoenergetic images (SCM: 96-100% of patients, RCM: 88-94%) without statistical difference between both groups. Segments with attenuation measurements below the threshold remained qualitatively assessable as well. Likert scores were 'excellent' for virtual monoenergetic images 50 keV and 55 keV in both groups (RCM: 1.2-1.4, SCM: 1.2-1.3). With diagnostic image quality maintained, it can be concluded that reduced iodine loads of 14-24.5 gI are feasible for pre-TAVI vascular assessment on a spectral detector CT scanner.

BMI-Adapted Double Low-Dose Dual-Source Aortic CT for Endoleak Detection after Endovascular Repair: A Prospective Intra-Individual Diagnostic Accuracy Study.

PURPOSE: To assess the diagnostic accuracy of BMI-adapted, low-radiation and low-iodine dose, dual-source aortic CT for endoleak detection in non-obese and obese patients following endovascular aortic repair. METHODS: In this prospective single-center study, patients referred for follow-up CT after endovascular repair with a history of at least one standard triphasic (native, arterial and delayed phase) routine CT protocol were enrolled. Patients were divided into two groups and allocated to a BMI-adapted (group A, BMI < 30 kg/m2; group B, BMI ≥ 30 kg/m2) double low-dose CT (DLCT) protocol comprising single-energy arterial and dual-energy delayed phase series with virtual non-contrast (VNC) reconstructions. An in-patient comparison of the DLCT and routine CT protocol as reference standard was performed regarding differences in diagnostic accuracy, radiation dose, and image quality. RESULTS: Seventy-five patients were included in the study (mean age 73 ± 8 years, 63 (84%) male). Endoleaks were diagnosed in 20 (26.7%) patients, 11 of 53 (20.8%) in group A and 9 of 22 (40.9%) in group B. Two radiologists achieved an overall diagnostic accuracy of 98.7% and 97.3% for endoleak detection, with 100% in group A and 95.5% and 90.9% in group B. All examinations were diagnostic. The DLCT protocol reduced the effective dose from 10.0 ± 3.6 mSv to 6.1 ± 1.5 mSv (p < 0.001) and the total iodine dose from 31.5 g to 14.5 g in group A and to 17.4 g in group B. CONCLUSION: Optimized double low-dose dual-source aortic CT with VNC, arterial and delayed phase images demonstrated high diagnostic accuracy for endoleak detection and significant radiation and iodine dose reductions in both obese and non-obese patients compared to the reference standard of triple phase, standard radiation and iodine dose aortic CT.

Phenotyping of COPD with MRI in comparison to same-day CT in a multi-centre trial.

OBJECTIVES: A prospective, multi-centre study to evaluate concordance of morphologic lung MRI and CT in chronic obstructive pulmonary disease (COPD) phenotyping for airway disease and emphysema. METHODS: A total of 601 participants with COPD from 15 sites underwent same-day morpho-functional chest MRI and paired inspiratory-expiratory CT. Two readers systematically scored bronchial wall thickening, bronchiectasis, centrilobular nodules, air trapping and lung parenchyma defects in each lung lobe and determined COPD phenotype. A third reader acted as adjudicator to establish consensus. Inter-modality and inter-reader agreement were assessed using Cohen's kappa (im-κ and ir-κ). RESULTS: The mean combined MRI score for bronchiectasis/bronchial wall thickening was 4.5/12 (CT scores, 2.2/12 for bronchiectasis and 6/12 for bronchial wall thickening; im-κ, 0.04-0.3). Expiratory right/left bronchial collapse was observed in 51 and 47/583 on MRI (62 and 57/599 on CT; im-κ, 0.49-0.52). Markers of small airways disease on MRI were 0.15/12 for centrilobular nodules (CT, 0.34/12), 0.94/12 for air trapping (CT, 0.9/12) and 7.6/12 for perfusion deficits (CT, 0.37/12 for mosaic attenuation; im-κ, 0.1-0.41). The mean lung defect score on MRI was 1.3/12 (CT emphysema score, 5.8/24; im-κ, 0.18-0.26). Airway-/emphysema/mixed COPD phenotypes were assigned in 370, 218 and 10 of 583 cases on MRI (347, 218 and 34 of 599 cases on CT; im-κ, 0.63). For all examined features, inter-reader agreement on MRI was lower than on CT. CONCLUSION: Concordance of MRI and CT for phenotyping of COPD in a multi-centre setting was substantial with variable inter-modality and inter-reader concordance for single diagnostic key features. CLINICAL RELEVANCE STATEMENT: MRI of lung morphology may well serve as a radiation-free imaging modality for COPD in scientific and clinical settings, given that its potential and limitations as shown here are carefully considered. KEY POINTS: • In a multi-centre setting, MRI and CT showed substantial concordance for phenotyping of COPD (airway-/emphysema-/mixed-type). • Individual features of COPD demonstrated variable inter-modality concordance with features of pulmonary hypertension showing the highest and bronchiectasis showing the lowest concordance. • For all single features of COPD, inter-reader agreement was lower on MRI than on CT.

COVID-19 pneumonia: Prediction of patient outcome by CT-based quantitative lung parenchyma analysis combined with laboratory parameters.

OBJECTIVES: To evaluate the prognostic value of fully automatic lung quantification based on spectral computed tomography (CT) and laboratory parameters for combined outcome prediction in COVID-19 pneumonia. METHODS: CT images of 53 hospitalized COVID-19 patients including virtual monochromatic reconstructions at 40-140keV were analyzed using a fully automated software system. Quantitative CT (QCT) parameters including mean and percentiles of lung density, fibrosis index (FIBI-700, defined as the percentage of segmented lung voxels ≥-700 HU), quantification of ground-glass opacities and well-aerated lung areas were analyzed. QCT parameters were correlated to laboratory and patient outcome parameters (hospitalization, days on intensive care unit, invasive and non-invasive ventilation). RESULTS: Best correlations were found for laboratory parameters LDH (r = 0.54), CRP (r = 0.49), Procalcitonin (r = 0.37) and partial pressure of oxygen (r = 0.35) with the QCT parameter 75th percentile of lung density. LDH, Procalcitonin, 75th percentile of lung density and FIBI-700 were the strongest independent predictors of patients' outcome in terms of days of invasive ventilation. The combination of LDH and Procalcitonin with either 75th percentile of lung density or FIBI-700 achieved a r2 of 0.84 and 1.0 as well as an area under the receiver operating characteristic curve (AUC) of 0.99 and 1.0 for the prediction of the need of invasive ventilation. CONCLUSIONS: QCT parameters in combination with laboratory parameters could deliver a feasible prognostic tool for the prediction of invasive ventilation in patients with COVID-19 pneumonia.

Prospective Study of Low-Radiation and Low-Iodine Dose Aortic CT Angiography in Obese and Non-Obese Patients: Image Quality and Impact of Patient Characteristics.

The purpose of this study was to prospectively analyse image quality and radiation dose of body mass index (BMI)-adapted low-radiation and low-iodine dose CTA of the thoracoabdominal aorta in obese and non-obese patients. This prospective, single-centre study included patients scheduled for aortic CTA between November 2017 and August 2020 without symptoms of high-grade heart failure. A BMI-adapted protocol was used: Group A/Group B, BMI < 30/≥ 30 kg/m2, tube potential 80/100 kVp, total iodine dose 14.5/17.4 g. Intraindividual comparison with the institutional clinical routine aortic CTA protocol was performed. The final study cohort comprised 161 patients (mean 71.1 ± 9.4 years, 32 women), thereof 126 patients in Group A (mean BMI 25.4 ± 2.8 kg/m2) and 35 patients in Group B (34.0 ± 3.4 kg/m2). Mean attenuation over five aortoiliac measurement positions for Group A/B was 354.9 ± 78.2/262.1 ± 73.0 HU. Mean effective dose for Group A/B was 3.05 ± 0.46/6.02 ± 1.14 mSv. Intraindividual comparison in 50 patients demonstrated effective dose savings for Group A/B of 34.4 ± 14.5/25.4 ± 14.1% (both p < 0.001), and iodine dose savings for Group A/B of 54/44.8%. Regression analysis showed that female sex and increasing age were independently associated with higher vascular attenuation. In conclusion, BMI-adapted, low-radiation and low-iodine dose CTA of the thoracoabdominal aorta delivers diagnostic image quality in non-obese and obese patients without symptoms of high-grade heart failure, with superior image quality in females and the elderly.

Diagnostic accuracy of automated 3D volumetry of cardiac chambers by CT pulmonary angiography for identification of pulmonary hypertension due to left heart disease.

OBJECTIVES: To assess diagnostic accuracy of automated 3D volumetry of cardiac chambers based on computed tomography pulmonary angiography (CTPA) for the differentiation of pulmonary hypertension due to left heart disease (group 2 PH) from non-group 2 PH compared to manual diameter measurements. METHODS: Patients with confirmed PH undergoing right heart catheterisation and CTPA within 100 days for diagnostic workup of PH between August 2013 and February 2016 were included in this retrospective, single-centre study. Automated 3D segmentation of left atrium, left ventricle, right atrium and right ventricle (LA/LV/RA/RV) was performed by two independent and blinded radiologists using commercial software. For comparison, axial diameters were manually measured. The ability to differentiate group 2 PH from non-group 2 PH was assessed by means of logistic regression. RESULTS: Ninety-one patients (median 67.5 years, 44 women) were included, thereof 19 patients (20.9%) classified as group 2 PH. After adjustment for age, sex and mean pulmonary arterial pressure, group 2 PH was significantly associated with larger LA volume (p < 0.001), larger LV volume (p = 0.001), lower RV/LV volume ratio (p = 0.04) and lower RV/LA volume ratio (p = 0.003). LA volume demonstrated the highest discriminatory ability to identify group 2 PH (AUC, 0.908; 95% confidence interval, 0.835-0.981) and was significantly superior to LA diameter (p = 0.009). Intraobserver and interobserver agreements were excellent for all volume measurements (intraclass correlation coefficients 0.926-0.999, all p < 0.001). CONCLUSIONS: LA volume quantified by automated, CTPA-based 3D volumetry can differentiate group 2 PH from other PH groups with good diagnostic accuracy and yields significantly higher diagnostic accuracy than left atrial diameter. KEY POINTS: • Automated cardiac chamber volumetry using non-gated CT pulmonary angiography can differentiate pulmonary hypertension due to left heart disease from other causes with good diagnostic accuracy. • Left atrial volume yields significantly higher diagnostic accuracy than left atrial axial diameter for identification of pulmonary hypertension due to left heart disease without time-consuming manual processing.

Utility of Automated Cardiac Chamber Volumetry by Nongated CT Pulmonary Angiography for Detection of Pulmonary Hypertension Using the 2018 Updated Hemodynamic Definition.

BACKGROUND. Noninvasive tests for pulmonary hypertension (PH) are needed to help select patients for diagnostic right heart catheterization (RHC). CT pulmonary angiography (CTPA) is commonly performed for suspected PH. OBJECTIVE. The purpose of this study was to assess the utility of CTPA-based cardiac chamber volumetric measurements for the diagnosis of PH in comparison with echocardiographic and conventional CTPA parameters, with the 2018 updated hemodynamic definition used as reference. METHODS. This retrospective study included 109 patients (72 women and 37 men; median age, 68 years) who underwent nongated CTPA, transthoracic echocardiography, and RHC for the workup of suspected PH between August 2013 and February 2016. Two radiologists independently used automated 3D segmentation software to determine the volumes of the right ventricle (RV), right atrium (RA), left ventricle (LV), and left atrium (LA) and also measured the axial diameters of the cardiac chambers, main pulmonary artery, and ascending aorta. Interobserver agreement was assessed, and mean values were obtained; one observer repeated volumetric measurements to assess intraobserver agreement. ROC analysis was used to assess diagnostic performance for the detection of PH. A multivariable binary logistic regression model was established. RESULTS. A total of 60 of 109 patients had PH. Intra- and interobserver agreements were excellent for all volume measurements (intraclass correlation coefficients, 0.935-0.999). In patients with PH versus those without PH, RV volume was 172.6 versus 118.1 mL, and RA volume was 130.2 versus 77.0 mL (both p < .05). Cardiac chamber measurements with the highest AUC for PH were the RV/LV volume ratio and RA volume (both 0.791). Significant predictors of PH20 (as defined using the 2018 hemodynamic definition from the Sixth World Symposium on Pulmonary Hypertension) after adjustment for age, sex, and body surface area included RV volume per 10 mL (odds ratio [OR], 1.21), RA volume per 10 mL (OR, 1.27), RV/LV volume ratio (OR, 2.91), and RA/LA volume ratio (OR, 11.22). Regression analysis yielded a predictive model for PH that contained two independent predictors: echocardiographic pulmonary arterial systolic pressure and CTPA-based RA volume; the model had an AUC of 0.898, sensitivity of 83.3%, and specificity of 85.7%. CONCLUSION. Automated cardiac chamber volumetry using nongated CTPA, particularly of the RA, provides incremental utility relative to echocardiographic and conventional CTPA parameters for diagnosis of PH. CLINICAL IMPACT. Automated volumetry of cardiac chambers based on nongated CTPA may facilitate early noninvasive detection of PH, identifying patients who warrant further evaluation by RHC.

Acquisition of a Dose Management System with Consideration of Medico-Legal and Economic Aspects. / Beschaffung eines Dosismanagementsystems unter mediko-legalen und ökonomischen Aspekten.

BACKGROUND: New radiation protection regulation encompassing additional obligations for monitoring, reporting and recording of radiation exposure, was enacted on December 31, 2018. As a consequence, dose management systems (DMS) are necessary to fulfill the requirements. The process of selection, acquisition and implementation of a suitable IT solution for this purpose is a challenge that all X-ray-applying facilities, including hospitals and private practices, are currently facing. METHOD: A target/actual-analysis as well as a cost-utility analysis is presented for this specific case as a foundation for the acquisition decision-making process. RESULT: An actual analysis is necessary in order to record the current status of dose documentation. An interdivisional approach is recommended to include all imaging modalities and devices. An interdisciplinary steering committee can be helpful in enabling consensus and rapid action. A target analysis includes additional criteria with respect to ease of operation, technical feasibility, process optimization and research opportunities to consider in addition to the statutory requirements. By means of a cost-benefit analysis, considerations between costs and the individually weighted advantages and disadvantages of eligible DMS result in a ranking of preference for the available solutions. CONCLUSION: Requirements of a DMS can be summarized in a specification sheet. Deploying an actual condition analysis, target state analysis and cost-utility analysis can help to identify a suitable DMS to achieve rapid commissioning and highest possible user acceptance while optimizing costs at the same time. KEY POINTS: · An actual analysis reveals optimization and standardization needs in examination protocols and technical coding of dose data that can be addressed before or during the acquisition process.. · A specification sheet covers all functional, technical, and financial aspects of a target analysis.. · A cost-utility analysis is useful for exploring an appropriate dose management system with high user acceptance, rapid implementation, and low cost.. · An interdisciplinary steering committee can be helpful to enable early consensus building and fast action.. CITATION FORMAT: · Do TD, Melzig C, Kauczor H et al. Acquisition of a Dose Management System with Consideration of Medico-Legal and Economic Aspects. Fortschr Röntgenstr 2022; 194: 363 - 372.

[Increased pulmonary arterial and venous pressure]. / Pulmonalarterielle und pulmonalvenöse Drucksteigerung.

BACKGROUND: Increases in pressure in the pulmonary arteries or pulmonary veins may be the result of a variety of underlying diseases. Noninvasive imaging plays a crucial role not only for identification, but also for differential diagnosis. OBJECTIVES: This article provides a comparative review of the signs of increased pulmonary arterial and pulmonary venous pressure in chest X­ray and computed tomography (CT). RADIOLOGICAL PROCEDURES: Typical signs of a pulmonary arterial or pulmonary venous pressure increase in chest X­ray and CT facilitate diagnosis of pulmonary hypertension (e.g., enlargement of central pulmonary arteries) and interstitial or alveolar pulmonary edema (e.g., Kerley lines/thickened interlobular septae or butterfly edema). A basic understanding of imaging findings and underlying pathophysiology helps in establishing the differential diagnosis. CONCLUSIONS: Chest X­ray and CT are essential for diagnosis of patients with suspected increased pulmonary arterial or pulmonary venous pressure.

Lower extremity CT angiography in peripheral arterial disease: from the established approach to evolving technical developments.

With the advent of multidetector computed tomography (CT), CT angiography (CTA) has gained widespread popularity for noninvasive imaging of the arterial vasculature. Peripheral extremity CTA can nowadays be performed rapidly with high spatial resolution and a decreased amount of both intravenous contrast and radiation exposure. In patients with peripheral artery disease (PAD), this technique can be used to delineate the bilateral lower extremity arterial tree and to determine the amount of atherosclerotic disease while differentiating between acute and chronic changes. This article provides an overview of several imaging techniques for PAD, specifically discusses the use of peripheral extremity CTA in patients with PAD, clinical indications, established technical considerations and novel technical developments, and the effect of postprocessing imaging techniques and structured reporting.

Single-energy versus dual-energy imaging during CT-guided biopsy using dedicated metal artifact reduction algorithm in an in vivo pig model.

PURPOSE: To evaluate dual-energy CT (DE) and dedicated metal artifact reduction algorithms (iMAR) during CT-guided biopsy in comparison to single-energy CT (SE). METHODS: A trocar was placed in the liver of six pigs. CT acquisitions were performed with SE and dose equivalent DE at four dose levels(1.7-13.5mGy). Iterative reconstructions were performed with and without iMAR. ROIs were placed in four positions e.g. at the trocar tip(TROCAR) and liver parenchyma adjacent to the trocar tip(LIVER-1) by two independent observers for quantitative analysis using CT numbers, noise, SNR and CNR. Qualitative image analysis was performed regarding overall image quality and artifacts generated by iMAR. RESULTS: There were no significant differences in CT numbers between DE and SE at TROCAR and LIVER-1 irrespective of iMAR. iMAR significantly reduced metal artifacts at LIVER-1 for all exposure settings for DE and SE(p = 0.02-0.04), but not at TROCAR. SNR, CNR and noise were comparable for DE and SE. SNR was best for high dose levels of 6.7/13.5mGy. Mean difference in the Blant-Altman analysis was -8.43 to 0.36. Cohen's kappa for qualitative interreader-agreement was 0.901. CONCLUSIONS: iMAR independently reduced metal artifacts more effectively and efficiently than CT acquisition in DE at any dose setting and its application is feasible during CT-guided liver biopsy.

The value of iterative metal artifact reduction algorithms during antenna positioning for CT-guided microwave ablation.

Objectives: To compare image quality between filtered back projection (FBP) and iterative reconstruction algorithm and dedicated metal artifact reduction (iMAR) algorithms during antenna positioning for computed tomography-guided microwave ablation (MWA).Materials and methods: An MWA antenna was positioned in the liver of five pigs under CT guidance. Different exposure settings (120kVp/200mAs-120kVp/50mAs) and image reconstruction techniques (FBP, iterative reconstruction with and without iMAR) were applied. Quantitative image analysis included density measurements in six positions (e.g., liver in extension of the antenna [ANTENNA] and liver >3 cm away from the antenna [LIVER-1]). Qualitative image analysis included assessment of overall quality, image noise, artifacts at the antenna tip, artifacts in liver parenchyma bordering antenna tip and newly generated artifacts. Two independent observers performed the analyses twice and interreader agreement was compared with Bland-Altman analysis.Results: For all exposure and reconstruction settings, density measurements for ANTENNA were significantly higher for the I30-1 iMAR compared with FBP and I30-1 (e.g., 8.3-17.2HU vs. -104.5 to 155.1HU; p ≤ 0.01, respectively). In contrast, for all exposure settings, density measurements for LIVER-1 were comparable between FBP and I30-1 iMAR (e.g., 49.4-50.4HU vs. 50.1-52.5U, respectively). For all exposure and reconstruction settings, subjective image quality for LIVER-1 was better for the I30-1 iMAR algorithm compared with FBP and I30-1. Bland-Altman interobserver agreement was from -0.2 to 0.2 for FBP and iMAR, and Cohen's kappa was 0.74.Conclusion: Iterative algorithms I30-1 with iMAR algorithm improves image quality during antenna positioning and placement for CT-guided MWA and is applicable over a range of exposure settings.

A Novel Method for Segmentation-Based Semiautomatic Quantitative Evaluation of Metal Artifact Reduction Algorithms.

OBJECTIVES: The aim of this study was to establish an objective segmentation-based evaluation of metal artifact reduction algorithms in the context of percutaneous microwave ablation in a porcine model. MATERIALS AND METHODS: Five computed tomography acquisitions from a previous animal study on computed tomography-guided percutaneous applicator positioning for microwave antenna were reconstructed with 6 different algorithms (30 image series total): standard filtered backprojection (B30f) and iterative reconstruction (ADMIRE-I30-1, ADMIRE-I30-3), all with and without metal artifact reduction. For artifact quantification, 3-dimensional segmentation of liver parenchyma without visible artifacts (VLiverReference) and liver volume surrounding the antenna (VLiverVOI) was performed, determining thresholds for artifact segmentation and calculating volume of voxels influenced by artifacts. Objective image analysis was based on relative volume of artifacts, and subjective image quality (ie, metal artifact extent) was evaluated by 2 independent observers. Correlation between objective and subjective evaluation was calculated. RESULTS: Both objective and subjective evaluations showed a significant reduction in metal artifacts when using dedicated metal artifact reduction algorithms (both P < 0.05). No significant reduction in metal artifacts was found when using iterative reconstruction (both P > 0.05). A good correlation between subjective and objective image quality was found (Spearman rank correlation coefficient rs = 0.65; P < 0.05). Interreader agreement was substantial (κ = 0.67). CONCLUSIONS: Segmentation-based objective evaluation of metal artifacts shows good agreement with conventional subjective evaluations and offers a promising quantitative and precise approach with limited time expenditure.

Combined automated 3D volumetry by pulmonary CT angiography and echocardiography for detection of pulmonary hypertension.

OBJECTIVES: To assess the diagnostic accuracy of automated 3D volumetry of central pulmonary arteries using computed tomography pulmonary angiography (CTPA) for suspected pulmonary hypertension alone and in combination with echocardiography. METHODS: This retrospective diagnostic accuracy study included 70 patients (mean age 66.7, 48 female) assessed for pulmonary hypertension by CTPA and transthoracic echocardiography with estimation of the pulmonary arterial systolic pressure (PASP). Gold standard right heart catheterisation with measurement of the invasive mean pulmonary arterial pressure (invasive mPAP) served as the reference. Volumes of the main, right and left pulmonary arteries (MPA, RPA and LPA) were computed using automated 3D segmentation. For comparison, axial dimensions were manually measured. A linear regression model was established for prediction of mPAP (predicted mPAP). RESULTS: MPA, RPA and LPA volumes were significantly increased in patients with vs. without pulmonary hypertension (all p < 0.001). Of all measures, MPA volume demonstrated the strongest correlation with invasive mPAP (r = 0.76, p < 0.001). Predicted mPAP using MPA volume and echocardiographic PASP as covariates showed excellent correlation with invasive mPAP (r = 0.89, p < 0.001). Area under the curves for predicting pulmonary hypertension were 0.94 for predicted mPAP, compared to 0.90 for MPA volume and 0.92 for echocardiographic PASP alone. A predicted mPAP > 25.8 mmHg identified pulmonary hypertension with sensitivity, specificity, positive and negative predictive values of 86%, 93%, 95% and 81%, respectively. CONCLUSIONS: Automated 3D volumetry of central pulmonary arteries based on CTPA may be used in conjunction with echocardiographic pressure estimates to noninvasively predict mPAP and pulmonary hypertension as confirmed by gold standard right heart catheterisation with higher diagnostic accuracy than either test alone. KEY POINTS: • This diagnostic accuracy study derived a regression model for noninvasive prediction of invasively measured mean pulmonary arterial pressure as assessed by gold standard right heart catheterisation. • This regression model using automated 3D volumetry of the central pulmonary arteries based on CT pulmonary angiography in conjunction with the echocardiographic pressure estimate predicted pulmonary arterial pressure and the presence of pulmonary hypertension with good diagnostic accuracy. • The combination of automated 3D volumetry and echocardiographic pressure estimate in the regression model provided superior diagnostic accuracy compared to each parameter alone.

Advanced imaging in pulmonary hypertension: emerging techniques and applications.

Pulmonary hypertension (PH) is a pathophysiological disorder defined by an increase in pulmonary arterial pressure which can occur in multiple clinical conditions. Irrespective of etiology, PH entails a negative impact on exercise capacity and quality of life, and is associated with high mortality particularly in pulmonary arterial hypertension. Noninvasive imaging techniques play an important role in suggesting the presence of PH, providing noninvasive pulmonary pressure measurements, classifying the group of PH, identifying a possibly underlying disease, providing prognostic information and assessing response to treatment. While echocardiography, computed tomography (CT) and ventilation/perfusion scans are an integral part of routine work-up of patients with suspected PH according to current guidelines and across centers, innovative new techniques and applications in the field of PH such as 3D echocardiography, dual-energy CT, 4D flow magnetic resonance imaging (MRI), T1 and extracellular volume fraction mapping, non-contrast-enhanced MRI sequences for perfusion and ventilation assessment, and molecular-targeted positron emission tomography are emerging. This review discusses advanced and emerging imaging techniques in diagnosis, prognostic evaluation and follow-up of patients with PH.

Combined external beam radiotherapy with carbon ions and tumor targeting endoradiotherapy.

External beam radiotherapy (EBRT) with carbon ions and endoradiotherapy using radiolabeled tumor targeting agents are emerging concepts in precision cancer therapy. We report on combination effects of these two promising strategies. Tumor targeting 131I-labelled anti-EGFR-antibody (Cetuximab) was used in the prototypic EGFR-expressing A431 human squamous cell carcinoma xenograft model. A 131I-labelled melanin-binding benzamide derivative was utilized targeting B16F10 melanoma in an orthotopic syngeneic C57bl6 model. Fractionated EBRT was performed using carbon ions in direct comparison with conventional photon irradiation. Tumor uptake of 131I-Cetuximab and 131I-Benzamide was enhanced by fractionated EBRT as determined by biodistribution studies. This effect was independent of radiation quality and significant for the small molecule 131I-Benzamide, i.e., >30% more uptake in irradiated vs. non-irradiated melanoma was found (p<0.05). Compared to each monotherapy, dual combination with 131I-Cetuximab and EBRT was most effective in inhibiting A431 tumor growth. A similar trend was seen for 131I-Benzamide and EBRT in B16F10 melanoma model. Addition of 131I-Benzamide endoradiotherapy to EBRT altered expression of genes related to DNA-repair, cell cycle and cell death. In contrast, immune-response related pathways such as type 1 interferon response genes (ISG15, MX1) were predominantly upregulated after combined 131I-Cetuximab and EBRT. The beneficial effects of combined 131I-Cetuximab and EBRT was further attributed to a reduced microvascular density (CD31) and decreased proliferation index (Ki-67). Fractionated EBRT could be favorably combined with endoradiotherapy. 131I-Benzamide endoradiotherapy accelerated EBRT induced cytotoxic effects. Activation of immune-response by carbon ions markedly enhanced anti-EGFR based endoradiotherapy suggesting further evaluation of this novel and promising radioimmunotherapy concept.

Automated 3D Volumetry of the Pulmonary Arteries based on Magnetic Resonance Angiography Has Potential for Predicting Pulmonary Hypertension.

PURPOSE: To demonstrate feasibility of automated 3D volumetry of central pulmonary arteries based on magnetic resonance angiography (MRA), to assess pulmonary artery volumes in patients with pulmonary hypertension compared to healthy controls, and to investigate the potential of the technique for predicting pulmonary hypertension. METHODS: MRA of pulmonary arteries was acquired at 1.5T in 20 patients with pulmonary arterial hypertension and 21 healthy normotensive controls. 3D model-based image analysis software was used for automated segmentation of main, right and left pulmonary arteries (MPA, RPA and LPA). Volumes indexed to vessel length and mean, minimum and maximum diameters along the entire vessel course were assessed and corrected for body surface area (BSA). For comparison, diameters were also manually measured on axial reconstructions and double oblique multiplanar reformations. Analyses were performed by two cardiovascular radiologists, and by one radiologist again after 6 months. RESULTS: Mean volumes of MPA, RPA and LPA for patients/controls were 5508 ± 1236/3438 ± 749, 3522 ± 934/1664 ± 468 and 3093 ± 692/1812 ± 474 µl/(cm length x m2 BSA) (all p<0.001). Mean, minimum and maximum diameters along the entire vessel course were also significantly increased in patients compared to controls (all p<0.001). Intra- and interobserver agreement were excellent for both volume and diameter measurements using 3D segmentation (intraclass correlation coefficients 0.971-0.999, p<0.001). Area under the curve for predicting pulmonary hypertension using volume was 0.998 (95% confidence interval 0.990-1.0, p<0.001), compared to 0.967 using manually measured MPA diameter (95% confidence interval 0.910-1.0, p<0.001). CONCLUSIONS: Automated MRA-based 3D volumetry of central pulmonary arteries is feasible and demonstrated significantly increased volumes and diameters in patients with pulmonary arterial hypertension compared to healthy controls. Pulmonary artery volume may serve as a superior predictor for pulmonary hypertension compared to manual measurements on axial images but verification in a larger study population is warranted.

Engineering cell-fluorescent ion track hybrid detectors.

BACKGROUND: The lack of sensitive biocompatible particle track detectors has so far limited parallel detection of physical energy deposition and biological response. Fluorescent nuclear track detectors (FNTDs) based on Al2O3:C,Mg single crystals combined with confocal laser scanning microscopy (CLSM) provide 3D information on ion tracks with a resolution limited by light diffraction. Here we report the development of next generation cell-fluorescent ion track hybrid detectors (Cell-Fit-HD). METHODS: The biocompatibility of FNTDs was tested using six different cell lines, i.e. human non-small cell lung carcinoma (A549), glioblastoma (U87), androgen independent prostate cancer (PC3), epidermoid cancer (A431) and murine (VmDk) glioma SMA-560. To evaluate cell adherence, viability and conformal coverage of the crystals different seeding densities and alternative coating with extracellular matrix (fibronectin) was tested. Carbon irradiation was performed in Bragg peak (initial 270.55 MeV u⁻¹). A series of cell compartment specific fluorescence stains including nuclear (HOECHST), membrane (Glut-1), cytoplasm (Calcein AM, CM-DiI) were tested on Cell-Fit-HDs and a single CLSM was employed to co-detect the physical (crystal) as well as the biological (cell layer) information. RESULTS: The FNTD provides a biocompatible surface. Among the cells tested, A549 cells formed the most uniform, viable, tightly packed epithelial like monolayer. The ion track information was not compromised in Cell-Fit-HD as compared to the FNTD alone. Neither cell coating and culturing, nor additional staining procedures affected the properties of the FNTD surface to detect ion tracks. Standard immunofluorescence and live staining procedures could be employed to co-register cell biology and ion track information. CONCLUSIONS: The Cell-Fit-Hybrid Detector system is a promising platform for a multitude of studies linking biological response to energy deposition at high level of optical microscopy resolution.