CO2-based C-arm computed tomography (CACT) of the pelvic arteries: feasibility and diagnostic performance in comparison to CO2-angiography in patients with peripheral arterial disease.

BACKGROUND: Patients with substantially impaired kidney function and peripheral arterial disease (PAD) underwent comparative CO2-based depiction of the pelvic arteries (PAs). PURPOSE: To evaluate the feasibility and diagnostic performance of CO2-based C-arm computed tomography (CACT) and compare its depiction of PAs with CO2-digital subtraction angiography (DSA). MATERIAL AND METHODS: Fifteen patients (10 men, mean age 70 ± 11 years) with PAD received CO2-DSA and CO2-CACT of the PAs, depicted from the aorta to femoral arteries. These were divided into nine segments (135 in total) and graded by two independent readers for image quality (IQ; 1 = sufficient, 2 = minimal impairments, 3 = insufficient, 4 = outside field of view) and subsequent stenosis grading (SG; grade 1: normal to grade 4: occlusion), under exclusion of all segments with insufficient IQ. Inter-observer and inter-modality agreement calculation and subsequent consensus reading were performed and correlated to a standard of reference (StOR), representing a modality consensus. RESULTS: Of 135 segments, 117 showed sufficient IQ, excluding 18 segments (10 CACT, 8 DSA). Inter-observer agreement for IQ and consecutive SG demonstrated good to excellent agreement: IQDSA: κ = 0.83, IQCACT: κ = 0.76; StenosisDSA: κ = 0.71, StenosisCACT: κ = 0.84. Inter-modality agreement for SG lay at κ = 0.76 and κ = 0.65, respectively. More stenoses could be detected by CACT, and analysis of pooled consensus values of SG in CACTcons versus StOR showed an excellent agreement (κ = 0.96) that proved considerably higher than the moderate agreement between consensus values in DSAcons versus StOR (κ = 0.43). CONCLUSION: CO2-CACT proved feasible, and has the potential to optimize angiographic work-up of PAD in patients with contraindications for other contrast media.

Deep semantic lung segmentation for tracking potential pulmonary perfusion biomarkers in chronic obstructive pulmonary disease (COPD): The multi-ethnic study of atherosclerosis COPD study.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is associated with high morbidity and mortality. Identification of imaging biomarkers for phenotyping is necessary for future treatment and therapy monitoring. However, translation of visual analytic pipelines into clinics or their use in large-scale studies is significantly slowed by time-consuming postprocessing steps. PURPOSE: To implement an automated tool chain for regional quantification of pulmonary microvascular blood flow in order to reduce analysis time and user variability. STUDY TYPE: Prospective. POPULATION: In all, 90 MRI scans of 63 patients, of which 31 had a COPD with a mean Global Initiative for Chronic Obstructive Lung Disease status of 1.9 ± 0.64 (µ ± σ). FIELD STRENGTH/SEQUENCE: 1.5T dynamic gadolinium-enhanced MRI measurement using 4D dynamic contrast material-enhanced (DCE) time-resolved angiography acquired in a single breath-hold in inspiration. [Correction added on August 20, 2019, after first online publication: The field strength in the preceding sentence was corrected.] ASSESSMENT: We built a 3D convolutional neural network for semantic segmentation using 29 manually segmented perfusion maps. All five lobes of the lung are denoted, including the middle lobe. Evaluation was performed on 61 independent cases from two sites of the Multi-Ethnic Study of Arteriosclerosis (MESA)-COPD study. We publish our implementation of a model-free deconvolution filter according to Sourbron et al for 4D DCE MRI scans as open source. STATISTICAL TEST: Cross-validation 29/61 (# training / # testing), intraclass correlation coefficient (ICC), Spearman ρ, Pearson r, Sørensen-Dice coefficient, and overlap. RESULTS: Segmentations and derived clinical parameters were processed in ~90 seconds per case on a Xeon E5-2637v4 workstation with Tesla P40 GPUs. Clinical parameters and predicted segmentations exhibit high concordance with the ground truth regarding median perfusion for all lobes with an ICC of 0.99 and a Sørensen-Dice coefficient of 93.4 ± 2.8 (µ ± σ). DATA CONCLUSION: We present a robust end-to-end pipeline that allows for the extraction of perfusion-based biomarkers for all lung lobes in 4D DCE MRI scans by combining model-free deconvolution with deep learning. LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2020;51:571-579.

A Retrospective Analysis of Nonocclusive Mesenteric Ischemia in Medical and Surgical ICU Patients: Clinical Data on Demography, Clinical Signs, and Survival.

BACKGROUND: To analyze demography, clinical signs, and survival of intensive care patients diagnosed with nonocclusive mesenteric ischemia (NOMI) and to evaluate the effect of a local intra-arterial prostaglandin therapy. METHODS: Retrospective observational study screening 455 intensive care patients with acute arterial mesenteric perfusion disorder in a tertiary care hospital within the past 8 years. Lastly, 32 patients with NOMI were enrolled, of which 11 received local intra-arterial prostaglandin therapy. The diagnosis of NOMI was based on the clinical presentation and established biphasic computed tomography criteria. Clinical and biochemical data were obtained 24 hours before, at the time, and 24 hours after diagnosis. RESULTS: Patients were 60.5 (49.3-73) years old and had multiple comorbidities. Most of them were diagnosed with septic shock requiring high doses of norepinephrine (NE: 0.382 [0.249-0.627] µg/kg/min). The Sequential Organ Failure Assessment (SOFA) score was 18 (16-20). A decrease in oxygenation (Pao 2/Fio 2), pH, and bicarbonate and an increase in international normalized ratio, lactate, bilirubin, leucocyte count, and NE dose were early indicators of NOMI. Median SOFA score significantly increased in the last 24 hours before diagnosis of NOMI (16 vs 18, P < .0001). Overall, 28-day mortality was 75% (81% nonintervention vs 64% intervention cohort; P = .579). Median SOFA scores 24 hours after intervention increased by +5% in the nonintervention group and decreased by 5.5% in the intervention group (P = .0059). CONCLUSIONS: Our data suggest that NOMI is a detrimental disease associated with progressive organ failure and a high mortality. Local intra-arterial prostaglandin application might hold promise as a rescue treatment strategy. These data encourage future randomized controlled trials are desirable.

Nonocclusive Mesenteric Ischemia and Interventional Local Vasodilatory Therapy: A Meta-Analysis and Systematic Review of the Literature.

BACKGROUND: Intensive care patients with nonocclusive mesenteric ischemia (NOMI) show mortality rates of 70% to 90%. Besides emergency surgery, different interventional local vasodilatory treatment (LVT) attempts have been described. We performed a systematic review and a meta-analysis to evaluate feasibility, efficacy, and tolerability of LVT in patients with life-threatening NOMI. METHODS: Searches of PubMed, EMBASE, Web of Science, and Cochrane Library databases were performed until February 2019. Measured outcomes included immediate technical success rates (as indicated by mesenteric vasodilation on angiography or clinical improvement) and adverse events (AEs). Therapeutic efficacy was measured by the assessment of overall mortality. RESULTS: Twelve studies (335 patients, 245 received LVT) from 1977 to 2018 were included. All studies were retrospective (4 comparative and 8 noncomparative). Different intra-arterial vasodilators (4× papaverine, 6× prostaglandin E1, 1× tolazoline/heparin, 1× tolazoline + iloprost) were reported. Initial technical success rate was 75.9% (95% confidence interval [CI], 55.1%-89%, P = .017) with an AE rate of 2.9% (95% CI: 1.3%-6.6%; P = .983). Overall mortality in LVT patients was 40.3% (95% CI: 28.7%-53%, P = .134). In 4 studies, outcomes were compared between patients receiving LVT to those who received standard of care (odds ratio for death in LVT patients was 0.261 [95% CI: 0.095-0.712, P = .009]). CONCLUSIONS: Local vasodilatory treatment appears to be safe in patients with NOMI and might have the potential to at least partially reverse mesenteric vasoconstriction features in control angiographies. However, with no randomized and prospective studies available yet, the overall quality of published studies has to be considered as low; therefore, it is not possible to draw generalizable conclusions from the present data concerning clinical end points. Its application might hold promise as a rescue treatment strategy and deserves further evaluation in randomized controlled trials.

C-Arm computed tomography (CACT)-guided balloon pulmonary angioplasty (BPA): Evaluation of patient safety and peri- and post-procedural complications.

AIM: To assess the frequency and severity of complications of balloon pulmonary angioplasty (BPA) using C-arm computed tomography (CACT) guidance. MATERIAL AND METHODS: 266 consecutive interventions in 67 patients (42 females, mean age 66 ± 13 years) were included. Selective CACT was acquired prior to the intervention for three-dimensional (3D) guidance and to select appropriate balloon size based on the measured vessel diameter. Complications during and after the procedure, the need for further interventions and the impact on patient safety and outcome were assessed and categorised according to the SIR Classification System to Complications by Outcome (Grade A-F). RESULTS: Overall, 237 interventions were conducted without any complications (89.1%). Minor complications not requiring additional treatment occurred during or after 25 procedures (9.4%), including recurring dry cough in four patients during a total of 11 interventions (4.1%) (Grade A), three focal dissections of the targeted pulmonary artery (1.1%), four cases of pulmonary haemorrhage (1.5%), one case of reperfusion oedema (0.4%) and six cases of post-interventional short-term hemoptysis (2.3%) (Grade B). Four cases of major complications requiring additional treatment were observed (1.5%): one case of pulmonary haemorrhage (0.4%) and two cases of post-interventional haemoptysis (0.8%), all resolved after medical therapy without requiring further intervention, and one case of atrial tachycardia induced during catheterisation, subsequently requiring pharmacological cardioversion (0.4%) (Grade C). No fatal or life-threatening peri- or post-interventional complications or mortality were observed (Grade D-F). CONCLUSION: BPA performed under CACT guidance appears to be a safe procedure with a low risk of severe complications. KEY POINTS: • CACT guidance of BPA is safe and successful. • CACT-guided BPA procedures have a low complication profile. • CACT guidance is a valuable tool to navigate BPA.

Chronic thromboembolic pulmonary hypertension: Evaluation of 2D-perfusion angiography in patients who undergo balloon pulmonary angioplasty.

OBJECTIVE: To evaluate the feasibility of 2D-perfusion angiography (2D-PA) in order to quantify perfusion changes of the lung parenchyma pre- and post-balloon pulmonary angioplasty (BPA). METHODS: Thirty consecutive interventions in 16 patients with 99 treated pulmonary artery segments were included. To quantify changes in pulmonary blood flow using 2D-PA, the acquired digital subtraction angiographies (DSA) pre- and post-BPA were post-processed. A reference ROI in the treated pulmonary artery and a distal target ROI in the lung parenchyma were placed in corresponding areas on DSA pre- and post-BPA. Time to peak (TTP), peak density (PD) and area under the curve (AUC) were assessed. The ratios reference ROI to target ROI (TTPparenchyma/TTPinflow; PDparenchyma/PDinflow; AUCparenchyma/AUCinflow) were calculated. Relative differences of the 2D-PA parameters were correlated to changes in the pulmonary-flow-grade-score. RESULTS: The pulmonary-flow-grade-score improved after BPA (p<0.0001). Likewise, the ratio TTPparenchyma/TTPinflow shortened by 10% (p=0.0002), the PDparenchyma/PDinflow increased by 46% (p<0.0001) and the AUCparenchyma/AUCinflow increased by 36% (p<0.0001). A significant correlation between changes in the pulmonary-flow-grade-score and changes in PDparenchyma/PDinflow (ρ=0.48, p<0.0001) and AUCparenchyma/AUCinflow (ρ=0.31, p=0.0018) was observed. CONCLUSION: Quantification of pulmonary perfusion pre- and post-BPA using 2D-PA is feasible and has the potential to improve monitoring of BPA. KEY POINTS: • Quantification of BPA results by use of 2D-PA is feasible. • 2D-PA allows objective assessment of changes in lung parenchymal perfusion. • 2D-PA has the potential to optimize BPA.

Image Quality and Radiation Exposure in Abdominal Angiography: A Head-to-Head Comparison of Conventional Detector-Dose-Driven Versus Contrast-to-Noise Ratio-Driven Exposure Control at Various Source-to-Image Receptor Distances and Collimations in a Pilot Phantom and Animal Study.

OBJECTIVES: This phantom and animal pilot study aimed to compare image quality and radiation exposure between detector-dose-driven exposure control (DEC) and contrast-to-noise ratio (CNR)-driven exposure control (CEC) as functions of source-to-image receptor distance (SID) and collimation. MATERIALS AND METHODS: First, an iron foil simulated a guide wire in a stack of polymethyl methacrylate and aluminum plates representing patient thicknesses of 15, 25, and 35 cm. Fluoroscopic images were acquired using 5 SIDs ranging from 100 to 130 cm and 2 collimations (full field of view, collimated field of view: 6 × 6 cm). The iron foil CNRs were calculated, and radiation doses in terms of air kerma rate were obtained and assessed using a multivariate regression. Second, 5 angiographic scenarios were created in 2 anesthetized pigs. Fluoroscopic images were acquired at 2 SIDs (110 and 130 cm) and both collimations. Two blinded experienced readers compared image quality to the reference image using full field of view at an SID of 110 cm. Air kerma rate was obtained and compared using t tests. RESULTS: Using DEC, both CNR and air kerma rate increased significantly at longer SID and collimation below the air kerma rate limit. When using CEC, CNR was significantly less dependent of SID, collimation, and patient thickness. Air kerma rate decreased at longer SID and tighter collimation. After reaching the air kerma rate limit, CEC behaved similarly to DEC. In the animal study using DEC, image quality and air kerma rate increased with longer SID and collimation (P < 0.005). Using CEC, image quality was not significantly different than using longer SID or tighter collimation. Air kerma rate was not significantly different at longer SID but lower using collimation (P = 0.012). CONCLUSIONS: CEC maintains the image quality with varying SID and collimation stricter than DEC, does not increase the air kerma rate at longer SID and reduces it with tighter collimation. After reaching the air kerma rate limit, CEC and DEC perform similarly.

New perspectives in unresectable cholangiocarcinoma? Evaluation of chemosaturation with percutaneous hepatic perfusion as a palliative treatment option.

Cholangiocarcinoma (CCA) are the second most common primary liver tumors and carry a dismal prognosis. Chemosaturation with percutaneous hepatic perfusion (PHP) is a palliative, intra-arterial therapeutic approach that provides a high dose chemotherapy of the liver with reduced systemic exposure. Aim of this retrospective, monocentric study was to analyze PHP as a palliative treatment for unresectable CCA. Toxicity, adverse events and complications were classified using the Common Terminology Criteria for Adverse Events (CTCAE v5.0). Overall response rate (ORR) and disease control rate (DCR) were evaluated according to the Response Evaluation Criteria in Solid Tumors (RECIST1.1). Median overall survival (mOS), median progression-free survival (mPFS) and hepatic mPFS (mhPFS) were computed using Kaplan-Meier estimation. In total 17 patients were treated with 42 PHP between 10/2014 and 09/2020. No significant complications occurred during the interventions. mOS was 27.6 (interquartile range (IQR) 16.5-37) months from first diagnosis and 9.9 (IQR 3.8-21) months from first PHP. mPFS was 4 (IQR 2-7) and mhPFS was 4 (IQR 3-10) months. ORR was 25% and DCR 75%. Significant, but transient hematotoxicity was frequent with grade 3/4 thrombopenia after 50%, leukopenia after 26% and anaemia after 21% of the interventions. An increase of transaminases (AST increase after 21% and ALT increase after 14% of the PHP) developed more often than a deterioration of the liver synthesis capacity. Salvage treatment with PHP has the potential to prolong life in selected patients with unresectable, refractory cholangiocarcinoma. The interventional procedure is safe. Post-interventional toxicity is frequent but manageable.

Tantalum-specific contrast-to-noise ratio or conventional detector dose-driven exposure control in angiography: radiation dose and image quality evaluation in a porcine model.

BACKGROUND: The aim of this animal study was to compare the fluoroscopic image quality (IQ) and radiation dose between a tantalum (Ta)-specific contrast-to-noise ratio-driven exposure control (Ta-CEC) and a detector dose-driven exposure control (DEC) in abdominal angiography. METHODS: Nine angiography scenarios were created in seven anaesthetised pigs using Ta-based embolisation material during percutaneous liver and kidney intervention. Fluoroscopic images were acquired using three DEC protocols with different dose levels and Ta-CEC protocols with different IQ levels, sampled in small steps. Polymethyl-methacrylate and aluminium plates were used to simulate attenuation of three water equivalent thicknesses (WET). Three blinded readers evaluated the IQ of DEC and dose equivalent Ta images and selected the Ta-IQ equivalent image corresponding to the DEC image. RESULTS: Interobserver agreement for the IQ assessment was 0.43 for DEC, 0.56 for Ta-CEC and for the assessment of incident air kerma at the interventional reference point (Ka,r) for the Ta-IQ equivalent image 0.73. The average IQ of the dose equivalent Ta images was superior compared to the DEC images (p < 0.001) and also for every WET (26, 31, or 36 cm) and dose level (p ≤ 0.022). The average Ka,r for the Ta-IQ equivalent images was 59 ± 16% (mean ± standard deviation) lower compared to the DEC images (p < 0.001). CONCLUSIONS: Compared to DEC, Ta-CEC significantly improved the fluoroscopic depiction of Ta, while maintaining the Ka,r. Alternatively, the Ka,r can be significantly reduced by using Ta-CEC instead of DEC, while maintaining equivalent IQ.

The Value of C-Arm Computed Tomography in Addition to Conventional Digital Subtraction Angiography in the Diagnostic Work-up of Patients with Suspected Chronic Thromboembolic Pulmonary Hypertension: An Update of 300 Patients.

RATIONALE AND OBJECTIVES: To assess the value and possible benefit of combined C-arm computed tomography (CACT) and conventional digital subtraction angiography (DSA) of the pulmonary arteries in the diagnostic work-up of patients with suspected chronic thromboembolic pulmonary hypertension (CTEPH). MATERIALS AND METHODS: We evaluated 308 pulmonary artery angiographies of 308 consecutive patients with suspected CTEPH. Seven patients were excluded because of incomplete imaging. Thus, 301 datasets were included in our study. The pulmonary artery segments and their subsegmental branching were independently evaluated by two readers (R1, R2) using both, DSA and CACT for optimal image quality. Subsequently, the diagnostic findings were compared. Inter-modality and inter-observer agreement were calculated. Consensus reading was done and correlated to a standard of reference, representing the overall consensus of both modalities. Fisher's exact test and Cohen's Kappa were applied. RESULTS: A total of 5719 pulmonary segments were evaluated of which only 28 segments (0.4%) were rated to be nondiagnostic on both, CACT and DSA. Overall, 5640 (98.6%) and 5600 (97.9%) pulmonary segments were rated to be diagnostic in DSA and CACT, respectively. The main causes of nondiagnostic image quality were motion artifacts on both, CACT (R1:81, R2:50) and DSA (R1:60, R2:48). Interobserver agreement was excellent for DSA (κ = 0.9) and CACT (κ = 0.91) and intermodality agreement was substantial (R1: κ = 0.69, R2: κ = 0.77). Compared to standard of reference, the intermodality agreement for CACT was excellent (κ = 0.96), whereas it was inferior for DSA (κ = 0.75), due to the higher number of pathologic findings in CACT read as normal on DSA. CONCLUSION: CACT of the pulmonary arteries can provide additional information to DSA during CTEPH work-up. Moreover, the combination of CACT and DSA can minimize the portion of non-diagnostic examinations, therefore being a reasonable combination to optimize the diagnostic work-up.

Effectuality study of a 3D motion correction algorithm in C-arm CTs of severely impaired image quality during transarterial chemoembolization.

BACKGROUND: To evaluate effectivity of a 3D-motion correction algorithm in C-Arm CTs (CACT) with limited image quality (IQ) during transarterial chemoembolization (TACE). METHODS: From 1/2015-5/2021, 644 CACTs were performed in patients during TACE. Of these, 27 CACTs in 26 patients (18 m, 8f; 69.7 years ± 10.7 SD) of limited IQ were included. Post-processing of the original raw-data sets (CACTOrg) included application of a 3D-motion correction algorithm and bone segmentation (CACTMC_no_bone). Four radiologists (R1-4) compared the images by choosing their preferred dataset and recommending repeat acquisition in case of severe IQ-impairment. R1,2 performed additional grading of intrahepatic vessel visualization, presence/extent of movement artifacts, and overall IQ. RESULTS: R1,2 demonstrated excellent interobserver agreement for overall IQ (ICC 0.79,p < 0.01) and the five-point vessel visualization scale before and after post-processing of the datasets (ICC 0.78,p < 0.01). Post-processing caused significant improvement, with overall IQ improving from 2.63 (CACTOrg) to 1.39 (CACTMC_no_bone;p < 0.01) and a decrease in the mean distance of identifiable, subcapsular vessels to the liver capsule by 4 mm (p < 0.01). This proved especially true for datasets with low parenchymal and high hepatic artery contrast. A good interobserver agreement (ICC = 0.73) was recorded concerning the presence of motion artifacts, with significantly less discernible motion after post-processing (CACTOrg:1.31 ± 1.67, CACTMC_no_bone:1.00 ± 1.34, p < 0.01). Of the 27 datasets, ≥ 23 CACTMC_no_bone were preferred, with identical datasets chosen by the readers to show benefit from the algorithm. CONCLUSION: Application of a 3D-motion correction algorithm significantly improved IQ in diagnostically limited CACTs during TACE, with the potential to decrease repeat acquisitions.

2D-Perfusion Angiography Using Carbon Dioxide (CO2): A Feasible Tool to Monitor Immediate Treatment Response to Endovascular Therapy of Peripheral Arterial Disease?

PURPOSE: Patients with peripheral arterial disease (PAD) or critical limb ischemia (CLI) require revascularization. Traditionally, endovascular therapy (EVT) is performed with iodinated contrast agent (ICM), which can provoke potential deterioration in renal function. CO2 is a safe negative contrast agent to guide vascular procedures, but interpretation of CO2 angiography is challenging. Changes in blood flow following iodine-aided EVT are assessable with 2D-perfusion angiography (2D-PA). The aim of this study was to evaluate 2D-PA as a tool to monitor blood flow changes during CO2-aided EVT. MATERIAL AND METHODS: 2D-PA was performed before and after ten EVTs (nine stents; one endoprosthesis; 10/2012-02/2020) in nine patients (six men; 65 ± 10y) with Fontaine stage IIb (n = 8) and IV (n = 1). A reference ROI (ROIINFLOW) was placed in the artery before the targeted obstruction and a target ROI (ROIOUTFLOW) distally. Corresponding ROIs were used pre- and post-EVT. Time to peak (TTP), peak density (PD) and area under the curve (AUC) were computed. The reference/target ROI ratios (TTPOUTFLOW/TTPINFLOW; PDOUTFLOW/PDINFLOW; AUCOUTFLOW/AUCINFLOW) were calculated. RESULTS: 2D-PA was technically feasible in all cases. A significant increase of 82% in PDOUTFLOW/PDINFLOW (0.44 ± 0.4 to 0.8 ± 0.63; p = 0.002) and of 132% in AUCOUTFLOW/AUCINFLOW (0.34 ± 0.22 to 0.79 ± 0.59; p = 0.002) was seen. A trend for a decrease in TTPOUTFLOW/TTPINFLOW was observed (- 24%; 5.57 ± 3.66 s-4.25 ± 1.64 s; p = 0.6). CONCLUSION: The presented 2D-PA technique facilitates the assessment of arterial flow in CO2-aided EVTs and has the potential to simplify the assessment of immediate treatment response.

Depiction of mosaic perfusion in chronic thromboembolic pulmonary hypertension (CTEPH) on C-arm computed tomography compared to computed tomography pulmonary angiogram (CTPA).

To evaluate mosaic perfusion patterns and vascular lesions in patients with chronic thromboembolic pulmonary hypertension (CTEPH) using C-Arm computed tomography (CACT) compared to computed tomography pulmonary angiography (CTPA). We included 41 patients (18 female; mean age 59.9 ± 18.3 years) with confirmed CTEPH who underwent CACT and CTPA within 21 days (average 5.3 ± 5.2). Two readers (R1; R2) independently evaluated datasets from both imaging techniques for mosaic perfusion patterns and presence of CTEPH-typical vascular lesions. The number of pulmonary arterial segments with typical findings was evaluated and the percentage of affected segments was calculated and categorized: < 25%; 25-49%; 50-75%; < 75% of all pulmonary arterial segments affected by thromboembolic vascular lesions. Inter-observer agreement was calculated for both modalities using the intraclass-correlation-coefficient (ICC). Based on consensus reading the inter-modality agreement (CACTcons vs. CTPAcons) was calculated using the ICC. Inter-observer agreement was excellent for central vascular lesions (ICC > 0.87) and the percentage of affected segments (ICC > 0.76) and good for the perceptibility of mosaic perfusion (ICC > 0.6) and attribution of the pattern of mosaic perfusion (ICC > 0.6) for both readers on CACT and CTPA. Inter-modality agreement was excellent for the perceptibility of mosaic perfusion (ICC = 1), the present perfusion pattern (ICC = 1) and central vascular lesions (ICC = 1). However, inter-modality agreement for the percentage of affected segments was fair (ICC = 0.50), with a greater proportion of identified affected segments on CACTcons. CACT demonstrates a high agreement with CTPA regarding the detection of mosaic perfusion. CACT detects a higher number of peripheral vascular lesions compared to CTPA.

Comparison of a contrast-to-noise ratio-driven exposure control and a regular detector dose-driven exposure control in abdominal imaging in a clinical angiography system.

PURPOSE: The first purpose of this phantom study was to verify whether a contrast-to-noise ratio (CNR)-driven exposure control (CEC) can maintain target CNR in angiography more precisely compared to a conventional detector dose-driven exposure control (DEC). The second purpose was to estimate the difference between incident air kerma produced by CEC and DEC when both exposure controls reach the same CNR. METHODS: A standardized 3D-printed phantom with an iron foil and a cavity, filled with iodinated contrast material, was developed to measure CNR using different image acquisition settings. This phantom was placed into a stack of polymethylmethacrylate and aluminum plates, simulating a patient equivalent thickness (PET) of 2.5-40 cm. Images were acquired using fluoroscopy and digital radiography modes with CEC using one image quality level and four image quality gradients and DEC having three different detector dose levels. The spatial frequency weighted CNR and incident air kerma were determined. The differences in incident air kerma between DEC and CEC were estimated. RESULTS: When using DEC, CNR decreased continuously with increasing attenuation, while CEC within physical limits maintained a predefined CNR level. Furthermore, CEC could be parameterized to deliver the CNR as a predefined function of PET. To provide a given CNR level, CEC used equal or lower air kerma than DEC. The mean estimated incident air kerma of CEC compared to DEC was between 3% (PET 20 cm) and 40% (PET 27.5 cm) lower in fluoroscopy and between 1% (PET 20 cm) and 55% (PET 2.5 cm) lower in digital radiography while maintaining CNR. CONCLUSION: Within physical and legislative limits, the CEC allows for a flexible adjustment of the CNR as a function of PET. Thus, the CEC enables task-dependent examination protocols with predefined image quality in order to easier achieve the as low as reasonably achievable principle. CEC required equal or lower incident air kerma than DEC to provide similar CNR, which allows for a substantial reduction of skin radiation dose in these situations.

Impact of a contrast-to-noise ratio driven and material specific exposure control on image quality and radiation exposure in angiography.

Conventional detector-dose driven exposure controls (DEC) do not consider the contrasting material of interest in angiography. Considering the latter when choosing the acquisition parameters should allow for optimization of x-ray quality and consecutively lead to a substantial reduction of radiation exposure. Therefore, the impact of a material-specific, contrast-to-noise ratio (CNR) driven exposure control (CEC) compared to DEC on radiation exposure was investigated. A 3D-printed phantom containing iron, tantalum, and platinum foils and cavities, filled with iodine, barium, and gas (carbon dioxide), was developed to measure the CNR. This phantom was placed within a stack of polymethylmethacrylate and aluminum plates simulating a patient equivalent thickness (PET) of 2.5-40 cm. Fluoroscopy and digital radiography (DR) were conducted applying either CEC or three, regular DEC protocols with parameter settings used in abdominal interventions. CEC protocols where chosen to achieve material-specific CNR values similar to those of DEC. Incident air kerma at the reference point(Ka,r), using either CEC or DEC, was assessed and possible Ka,r reduction for similar CNR was estimated. We show that CEC provided similar CNR as DEC at the same or lower Ka,r. When imaging barium, iron, and iodine Ka,r was substantially reduced below a PET of 20 cm and between 25 cm and 30 cm for fluoroscopy and Dr When imaging platinum and tantalum using fluoroscopy and DR and gas using DR, the Ka,r reduction was substantially higher. We estimate the Ka,r reduction for these materials between 15% and 84% for fluoroscopy and DR between 15% and 93% depending on the PET. The results of this study demonstrate a high potential for skin dose reduction in abdominal radiology when using a material-specific CEC compared to DEC. This effect is substantial in imaging materials with higher energy K-edges, which is beneficial, for example, in long-lasting embolization procedures with tantalum-based embolization material in young patients with arterio-venous malformations.

Evaluation of perfusion changes using a 2D Parametric Parenchymal Blood Flow technique with automated vessel suppression following partial spleen embolization in patients with hypersplenism and portal hypertension.

ABSTRACT: To evaluate the feasibility and potential value of 2D Parametric Parenchymal Blood Flow (2D-PPBF) for the assessment of perfusion changes following partial spleen embolization (PSE) in a retrospective observational study design.Overall, 12 PSE procedures in 12 patients were included in this study. The outcome of the study was the platelet response (PR), calculated as the percentage increase of platelet count (PLT), following PSE. To quantify perfusion changes using 2D-PPBF, the acquired digital subtraction angiography series were post-processed. A reference region-of-interest (ROI) was placed in the afferent splenic artery and a target ROI was positioned on the embolization territory of the spleen on digital subtraction angiography series pre- and post-embolization. The ratios of the target ROIs to the reference ROIs were calculated for the Wash-In-Rate (WIR), the Time-To-Peak (TTP) and the Area-Under-the-Curve (AUC). Comparisons between pre- and post-embolization data were made using Wilcoxon signed-rank test and Spearman's rank correlation coefficient (r). Afterwards, the study population was divided by the median of the TTP before PSE to analyze its value for the prediction of PR following PSE.Following PSE, PLT increased significantly from 43,000 ±â€Š21,405 platelets/µL to 128,500 ±â€Š66,083 platelets/µL with a PR of 255 ±â€Š243% (P = .003). In the embolized splenic territory, the pre-/post-embolization 2D-PPBF parameter changed significantly: WIRpre-PSE 1.23 ±â€Š2.42/WIRpost-PSE 0.09 ±â€Š0.07; -64 ±â€Š46% (p = 0.04), TTPpre-PSE 4.41 ±â€Š0.99/TTPpost-PSE 5.67 ±â€Š1.52 (P = .041); +34 ±â€Š47% and AUCpost-PSE 0.81 ±â€Š0.85/AUCpost-PSE 0.14 ±â€Š0.08; -71 ±â€Š18% (P = .002). A significant correlation of a 2D-PPBF parameter with the PLT was found for TTPpre-PSE/PLTpre-PSE r = -0.66 (P = .01). Subgroup analysis showed a significantly increased PR for the group with TTPpre-PSE >4.44 compared to the group with TTPpre-PSE ≤4.44 (404 ±â€Š267% versus 107 ±â€Š76%; P = .04).2D-PPBF is an objective approach to analyze the perfusion reduction of embolized splenic tissue. TTP derived from 2D-PPBF has the potential to predict the extent of PR during PSE.

Evaluation of a Motion Correction Algorithm for C-Arm Computed Tomography Acquired During Transarterial Chemoembolization.

PURPOSE: The aim of this retrospective study was to evaluate the feasibility of a motion correction 3D reconstruction prototype technique for C-arm computed tomography (CACT). MATERIAL AND METHODS: We included 65 consecutive CACTs acquired during transarterial chemoembolization of 54 patients (47 m,7f; 67 ± 11.3 years). All original raw datasets (CACTOrg) underwent reconstruction with and without volume punching of high-contrast objects using a 3D image reconstruction software to compensate for motion (CACTMC_bone;CACTMC_no bone). Subsequently, the effect on image quality (IQ) was evaluated using objective (image sharpness metric) and subjective criteria. Subjective criteria were defined by vessel geometry, overall IQ, delineation of tumor feeders, the presence of foreign material-induced artifacts and need for additional imaging, assessed by two independent readers on a 3-(vessel geometry and overall IQ) or 2-point scale, respectively. Friedman rank-sum test and post hoc analysis in form of pairwise Wilcoxon signed-rank test were computed and inter-observer agreement analyzed using kappa test. RESULTS: Objective IQ as defined by an image sharpness metric, increased from 273.5 ± 28 (CACTOrg) to 328.5 ± 55.1 (CACTMC_bone) and 331 ± 57.8 (CACTMC_no bone; all p < 0.0001). These results could largely be confirmed by the subjective analysis, which demonstrated predominantly good and moderate inter-observer agreement, with best agreement for CACTMC_no bone in all categories (e.g., vessel geometry: CACTOrg: κ = 0.51, CACTMC_bone: κ = 0.42, CACTMC_no bone: κ = 0.69). CONCLUSION: The application of a motion correction algorithm was feasible for all data sets and led to an increase in both objective and subjective IQ parameters. LEVEL OF EVIDENCE: 3.

Comparison of the Uptake of Hepatocellular Carcinoma on Pre-Therapeutic MDCT, CACT, and SPECT/CT, and the Correlation with Post-Therapeutic PET/CT in Patients Undergoing Selective Internal Radiation Therapy.

(1) Background: To comparatively analyze the uptake of hepatocellular carcinoma (HCC) on pre-therapeutic imaging modalities, the arterial phase multi-detector computed tomography (MDCT), the parenchymal phase C-arm computed tomography (CACT), the Technetium99m-macroaggregates of human serum albumin single-photon emission computed tomography/computed tomography (SPECT/CT), and the correlation to the post-therapeutic Yttrium90 positron emission tomography/computed tomography (PET/CT) in patients with selective internal radiation therapy (SIRT). (2) Methods: Between September 2013 and December 2016, 104 SIRT procedures were performed at our institution in 74 patients with HCC not suitable for curative surgery or ablation. Twenty-two patients underwent an identical sequence of pre-therapeutic MDCT, CACT, SPECT/CT, and post-therapeutic PET/CT with a standardized diagnostic and therapeutic protocol. In these 22 patients, 25 SIRT procedures were evaluated. The uptake of the HCC was assessed using tumor-background ratio (TBR). Therefore, regions of interest were placed on the tumor and the adjacent liver tissue on MDCT (TBRMDCT), CACT (TBRCACT), SPECT/CT (TBRSPECT/CT), and PET/CT (TBRPET/CT). Comparisons were made with the Friedman test and the Nemenyi post-hoc test. Correlations were analyzed using Spearman's Rho and the Benjamini-Hochberg method. The level of significance was p < 0.05. (3) Results: TBR on MDCT (1.4 ± 0.3) was significantly smaller than on CACT (1.9 ± 0.6) and both were significantly smaller compared to SPECT/CT (4.6 ± 2.0) (pFriedman-Test < 0.001; pTBRMDCT/TBRCACT = 0.012, pTBRMDCT/TBRSPECT/CT < 0.001, pTBRCACT/TBRSPECT/CT < 0.001). There was no significant correlation of TBR on MDCT with PET/CT (rTBRMDCT/TBRPET/CT = 0.116; p = 0.534). In contrast, TBR on CACT correlated to TBR on SPECT/CT (rTBRCACT/TBRSPECT/CT = 0.489; p = 0.004) and tended to correlate to TBR on PET/CT (rTBRCACT/TBRPET/CT =0.365; p = 0.043). TBR on SPECT/CT correlated to TBR on PET/CT (rTBRSPECT/CT/TBRPET/CT = 0.706; p < 0.001) (4) Conclusion: The uptake assessment on CACT was in agreement with SPECT/CT and might be consistent with PET/CT. In contrast, MDCT was not comparable to CACT and SPECT/CT, and had no correlation with PET/CT due to the different application techniques. This emphasizes the value of the CACT, which has the potential to improve the dosimetric assessment of the tumor and liver uptake for SIRT.

Transjugular intrahepatic portosystemic shunt placement: portal vein puncture guided by 3D/2D image registration of contrast-enhanced multi-detector computed tomography and fluoroscopy.

BACKGROUND: To assess the technical feasibility, success rate, puncture complications and procedural characteristics of transjugular intrahepatic portosystemic shunt (TIPS) placement using a three-dimensional vascular map (3D-VM) overlay based on image registration of pre-procedural contrast-enhanced (CE) multi-detector computed tomography (MDCT) for portal vein puncture guidance. MATERIALS AND METHODS: Overall, 27 consecutive patients (59 ± 9 years, 18male) with portal hypertension undergoing elective TIPS procedure were included. TIPS was guided by CE-MDCT overlay after image registration based on fluoroscopic images. A 3D-VM of the hepatic veins and the portal vein was created based on the pre-procedural CE-MDCT and superimposed on fluoroscopy in real-time. Procedural characteristics as well as hepatic vein catheterization time (HVCT), puncture time (PT), overall procedural time (OPT), fluoroscopy time (FT) and the dose area product (DAP) were evaluated. Thereafter, HVCT, PT, OPT and FT using 3D-VM (61 ± 9 years, 14male) were compared to a previous using classical fluoroscopic guidance (53 ± 9 years, 21male) for two interventional radiologist with less than 3 years of experience in TIPS placement. RESULTS: All TIPS procedure using of 3D/2D image registered 3D-VM were successful with a significant reduction of the PSG (p < 0.0001). No clinical significant complication occurred. HVCT was 14 ± 11 min, PT was 14 ± 6 min, OPT was 64 ± 29 min, FT was 21 ± 12 min and DAP was 107.48 ± 93.84 Gy cm2. HVCT, OPT and FT of the interventionalist with less TIPS experience using 3D/2D image registered 3D-VM were statistically different to an interventionalist with similar experience using fluoroscopic guidance (pHVCT = 0.0022; pOPT = 0.0097; pFT = 0.0009). PT between these interventionalists was not significantly different (pPT = 0.2905). CONCLUSION: TIPS placement applying registration-based CE-MDCT vessel information for puncture guidance is feasible and safe. It has the potential to improve hepatic vein catherization, portal vein puncture and radiation exposure.

Risk prediction in intrahepatic cholangiocarcinoma: Direct comparison of the MEGNA score and the 8th edition of the UICC/AJCC Cancer staging system.

BACKGROUND: External validation of prognostic risk models is essential before they are implemented in clinical practice. This study evaluated the recently developed MEGNA score for survival prediction after resection of intrahepatic cholangiocarcinoma (ICC), with a focus on the direct comparison of its prognostic value to that of the current International Union Against Cancer (UICC)/American Joint Committee on Cancer (AJCC) Cancer staging system. MATERIAL AND METHODS: Between 1997 and 2018, 417 consecutive patients with ICC were referred to our tertiary care centre and were retrospectively identified out of a dedicated clinical database. Of this group, 203 patients underwent surgical resection and met the inclusion criteria. Multivariate analysis was performed to assess the predictors of the recently proposed MEGNA score regarding overall survival (OS). Concordance indices (C-indices) and integrated Brier scores (IBS) were calculated to assess the ability of both the MEGNA score and the current (8th) edition of the UICC/AJCC Cancer staging system to predict individual patient outcome. RESULTS: Stratification according to the MEGNA score resulted in a median OS of 34.5 months, 26.1 months, 21.5 months, and 16.6 months for MEGNA scores 0, 1, 2, and ≥3, respectively (log rank p < 0.001). However, of the five factors that contribute to the MEGNA score, age > 60 years was not a predictor for poor OS in our cohort. The C-index for the MEGNA score was 0.58, the IBS was 0.193. The 8th edition of the UICC/AJCC system performed slightly better, with a C-index of 0.61 and an IBS of 0.186. CONCLUSION: The ability of the MEGNA score to predict individual patient outcome was only moderate in this external validation. Its prognostic value did not reach that of the more widely known and used UICC/AJCC system. However, neither scoring system performed well enough to support clear-cut clinical decisions.