Machine learning-based CT fractional flow reserve assessment in acute chest pain: first experience.

BACKGROUND: Computed tomography (CT)-derived fractional flow reserve (FFRCT) enables the non-invasive functional assessment of coronary artery stenosis. We evaluated the feasibility and potential clinical role of FFRCT in patients presenting to the emergency department with acute chest pain who underwent chest-pain CT (CPCT). METHODS: For this retrospective IRB-approved study, we included 56 patients (median age: 62 years, 14 females) with acute chest pain who underwent CPCT and who had at least a mild (≥25% diameter) coronary artery stenosis. CPCT was evaluated for the presence of acute plaque rupture and vulnerable plaque features. FFRCT measurements were performed using a machine learning-based software. We assessed the agreement between the results from FFRCT and patient outcome (including results from invasive catheter angiography and from any non-invasive cardiac imaging test, final clinical diagnosis and revascularization) for a follow-up of 3 months. RESULTS: FFRCT was technically feasible in 38/56 patients (68%). Eleven of the 38 patients (29%) showed acute plaque rupture in CPCT; all of them underwent immediate coronary revascularization. Of the remaining 27 patients (71%), 16 patients showed vulnerable plaque features (59%), of whom 11 (69%) were diagnosed with acute coronary syndrome (ACS) and 10 (63%) underwent coronary revascularization. In patients with vulnerable plaque features in CPCT, FFRCT had an agreement with outcome in 12/16 patients (75%). In patients without vulnerable plaque features (n=11), one patient showed myocardial ischemia (9%). In these patients, FFRCT and patient outcome showed an agreement in 10/11 patients (91%). CONCLUSIONS: Our preliminary data show that FFRCT is feasible in patients with acute chest pain who undergo CPCT provided that image quality is sufficient. FFRCT has the potential to improve patient triage by reducing further downstream testing but appears of limited value in patients with CT signs of acute plaque rupture.

Inter-reader agreement of interpretation of radiological course of bile duct changes between serial follow-up magnetic resonance imaging/3D magnetic resonance cholangiopancreatography of patients with primary sclerosing cholangitis.

Objectives: Interpretation of MRI/MRCP in primary sclerosing cholangitis (PSC) at a single time point has low inter-reader agreement. Agreement of interpretation of the dynamic course of duct changes in follow-up MRI/MRCP is of clinical importance but remains unknown. Our aims are therefore to assess the inter-reader agreement of interpretation of the course of duct changes in PSC and investigate if elimination of 3 D MRCP affects inter-reader agreement.Materials and Methods: We studied 40 consecutive PSC-patients who underwent two liver MRI/MRCPs at two time points. Two readers independently evaluated the course of duct changes between the two time points in two imaging sets, one with and one without 3 D MRCP. The intraclass correlation coefficient (ICC) was calculated for evaluation of inter-reader and intra-reader agreement between the two time points and two imaging sets accordingly.Results: Inter-reader agreement of the interpretation of the course of duct changes between the two time points was poor (ICC up to 0.224). Elimination of 3 D MRCP neither improved inter-reader agreement which was again poor (ICC up to 0.26) nor did it change considerably the way readers interpret the course of ducts changes (ICC for intra-reader agreement between 0.809 and 0.978).Conclusions: Inter-reader agreement of the interpretation of radiological course of duct changes is poor in serial follow-up MRI/MRCP of PSC-patients. Elimination of 3 D MRCP does not increase inter-reader agreement but maintains an excellent intra-reader agreement for the interpretation of the dynamic course of bile duct changes.Key pointsInter-reader agreement of interpretation of radiological course of bile duct changes between serial follow-up MRI/MRCP examinations of patients with PSC is poor.Absence of 3D MRCP does not affect considerably the way readers interpret the radiological course of bile ducts changes.When MRCP is absent or of low quality, utilization of other sequences seems to be helpful as an alternative for bile duct evaluation.

Erratum to the impact of slice-reduced computed tomography on histogram based densitometry assessment of lung fibrosis in patients with systemic sclerosis.

[This corrects the article DOI: 10.21037/jtd.2018.04.39.].

The synthetic localizer radiograph - A new CT scan planning method.

OBJECTIVE: To investigate if the conventional localizer radiograph (LR) can be replaced by a synthetic LR (SLR), generated from a low-dose spiral CT scan, for CT scan planning with minimal changes to current clinical workflows. METHODS: A dosimetric comparison of SLRs and LRs was made using Monte Carlo methods. Water equivalent diameters (WEDs) of a centered and mis-centered phantom were estimated from low-dose spiral CT scans and LRs acquired at different angles. Body sizes, in the form of two lengths and two diameters obtained from SLRs and LRs, were compared for 10 patients (4 men and 6 women with a mean age of 74.8 and 76.2 years respectively) undergoing CT of thorax and abdomen. The image quality of SLRs for CT scan planning relative to LRs was rated using a 5-grade scale by four radiologists and two CT radiographers. RESULTS: An SLR can be obtained at a comparable effective dose to that of traditionally acquired LRs: 0.14 mSv. WEDs from LRs were more affected by mis-centering than WEDs calculated from low-dose spiral scans. One significant discrepancy of estimated body sizes was observed, the broadest part of the patient that on lateral localizers showed a mean deviation of 17.7 mm (range: 7.3-28.7 mm, p < 0.001). The anteroposterior/posteroanterior SLR image quality was assessed as better compared to an LR while the same could not be shown for lateral localizers. CONCLUSIONS: SLRs based on low-dose spiral scans can replace LRs for CT planning.

The role of contrast-enhanced computed tomography to detect renal stones.

PURPOSE: To investigate the detectability of renal stones in corticomedullary and nephrographic phases on contrast-enhanced computed tomography (CT). METHODS: All consecutive patients between January 2012 and February 2016 undergoing CT of the kidneys according to our department's standard four-phase protocol and having at least one stone in the NC-phase (NCP) were included. Fifty patients with altogether 136 stones were eligible. Two radiologists in consensus evaluated the NCP from each examination and documented the number, location, and size of stones. Three abdominal radiologists blinded to the findings of the NCP reviewed independently the corticomedullary and nephrographic phases on two different occasions. They reported the number and location of stones in each kidney. For the inter-observer agreement the intra-class correlation coefficient (ICC) was estimated. The detection rate of renal stones was calculated for the three radiologists and compared between the two contrast-enhanced phases and the results were analyzed with concern to the size of the stones. RESULTS: The ICC was 0.86. There was no statistically significant difference between corticomedullary and nephrographic phases (p = 0.94). The detection rate for stones measuring 3-5 mm was 82-88% and 98% for stones ≥ 6 mm. CONCLUSION: The detectability of renal stones ≥ 6 mm on contrast-enhanced CT is extremely high. This means that stones with a higher risk of not passing spontaneously can be safely diagnosed.

Body composition evaluation with computed tomography: Contrast media and slice thickness cause methodological errors.

OBJECTIVE: Although computed tomography (CT) is frequently used to determine body composition, the effects of using different CT protocols is not well known. The aim of this study was to determine whether contrast media phase, radiation dose, and slice thickness in CT affect body composition segmentation. METHODS: Clinically indicated perfusion CTs of the upper abdomen in 20 patients (seven women) between 40 and 87 y of age with high suspicion of hepatocellular carcinoma were analyzed retrospectively. Axial images from the L3 level with varying imaging delay were reconstructed after contrast media injection (18 images per patient), slice thickness (5 images, 2-10 mm), and radiation dose (4 images with one-third to four-thirds of standard dose). Muscle and fat areas were segmented semiautomatically by drawing regions of interests and using established cutoff thresholds. Skeletal muscle index (SMI), steatotic muscle area, and adipose tissue index, as well as muscle attenuation and fat attenuation, were evaluated. RESULTS: Average SMI increased by up to 2.8% after contrast media injection. Steatotic muscle area decreased by ≤13.8%, and adipose tissue index decreased by ≤6.5%. Muscle attenuation increased after contrast media injection, whereas fat attenuation decreased (all P < 0.001). SMI decreased by 1.9% on average when increasing slice thickness from 2 to 10 mm. Steatotic muscle area increased by ≤3.3%, and adipose tissue index increased by ≤1.5% (all P < 0.05). Muscle attenuation did not change significantly with reconstruction thickness. Radiation dose had no effect on estimated area of spinal muscle, fatty spinal muscle, or visceral fat. CONCLUSIONS: Contrast media have a strong effect on the evaluation of body composition, whereas the influence of slice thickness is less pronounced. Radiation dose can be reduced by ≥66% without significantly affecting segmentation.

Chest pain CT in the emergency department: Watch out for the myocardium.

RATIONALE AND OBJECTIVES: To evaluate the frequency and relevance of hypodense myocardium (HM) encountered in patients undergoing chest-pain CT in the emergency department (ED). MATERIAL AND METHODS: In this IRB-approved retrospective study, ECG-gated chest-pain CT examinations of 300 consecutive patients (mean age 60 ± 17 years) presenting with acute chest-pain to our ED were evaluated. Once ST-segment elevation infarction was excluded, chest-pain CT including the coronary arteries (rule-out acute coronary syndrome (ACS), pulmonary embolism (PE) and acute aortic syndrome (AAS): chest-pain CTcoronary, n = 121) or not including the coronary arteries was performed (rule-out PE and AAS: chest-pain CTw/o coronary, n = 179). Each myocardial segment was assessed for the presence of HM; attenuation was measured and compared to normal myocardium. RESULTS: HM was identified in 27/300 patients (9%): 12/179 in chest-pain CTw/o coronary (7%) and 15/121 in chest-pain CTcoronary (12%). Mean attenuation of HM (40 ± 17 HU) was significantly lower than that of healthy myocardium (103 ± 18 HU, p < 0.001), with a mean difference of 61 ± 19 HU. In 15/27 patients (55.6%) with HM, the final diagnosis was acute MI, and in the remaining 12/27 patients (44.4%) previous MI was found in the patients' history. Chest-pain CTw/o coronary identified HM in 10/15 patients (66.6%) with a final diagnosis of acute MI. CONCLUSION: HM indicating acute MI are often encountered in chest pain CT in the ED, also in chest-pain CTw/o coronary when MI is not suspected. This indicates that the myocardium should always be analyzed for hypodense regions even when MI not suspected.

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.

Triple Arterial Phase CT of the Liver with Radiation Dose Equivalent to That of Single Arterial Phase CT: Initial Experience.

Purpose To develop and evaluate a triple arterial phase CT liver protocol with a similar radiation dose to that of standard single arterial phase CT in study subjects suspected of having hepatocellular carcinoma (HCC). Materials and Methods The study consisted of a retrospective part A for protocol development (n = 15) and a prospective part B to evaluate diagnostic accuracy (n = 38). All 53 participants underwent perfusion CT with 50 mL contrast material between August 2013 and September 2014. Group B underwent an additional standard multiphasic liver CT examination with 120 mL of contrast material (range, 70-143 mL). Image sets from triple arterial phase imaging were reconstructed from perfusion CT by fusing images from three dedicated arterial time points. Triple arterial phase CT and standard single arterial phase CT were compared by two readers, who assessed subjective image quality and HCC detection rate. A third reader served as reference reader and assessed objective image quality. The paired Student t test, Wilcoxon signed rank test, jackknife alternative free-response receiver operating characteristic (JAFROC), and JAFROC curve were applied. Results The mean volume CT dose index was 11.6 mGy for triple arterial phase CT and 11.9 mGy for standard single arterial phase CT (P = .73). Triple arterial phase CT showed lower image noise and better contrast-to-noise ratio compared with standard single arterial phase CT (P < .001 and P = .032, respectively); however, there was no significant difference in lesion-to-liver-contrast ratio (P = .31). Subjective image quality was good for both protocols. The detection rate of the 65 HCC lesions was 82% for reader 1 and 83% for reader 2 at triple arterial phase CT and 80% for reader 1 and 77% for reader 2 at standard single arterial phase CT (P = .4). Conclusion Triple arterial phase imaging is feasible at the same radiation dose as that used for standard single arterial phase CT. Triple arterial phase imaging provides equivalent to superior image quality and equal HCC detection rate despite the use of less than half the contrast material dose used at standard single arterial phase CT. © RSNA, 2018.

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.

Influence of tube potential on CT body composition analysis.

OBJECTIVES: Our purpose was to investigate whether tube potential in contrast-enhanced computed tomography (CT) affects body composition analysis. METHODS: Images from dual-source, dual-energy CT from the abdomen with intravenous contrast media administration were used. A total of 17 patients (11 women, mean age 52) with a mean body mass index of 20.8 kg/cm2 were included. Simultaneously acquired images with a tube voltage of 80 kV and 140 kV were compared. Body composition was analyzed on a single slice at the L3 level. Parameters evaluated included muscle and fat attenuation (Hounsfield units [HU]), skeletal muscle index (cm2/m2), muscle area (cm2), and steatotic muscle area (cm2). Significant differences between 80 kV and 140 kV series were compared using the paired Student's t test. RESULTS: Tube potential affected muscle attenuation with an average difference of 17% between 80 kV and 140 kV series (48 HU versus 41 HU, P < 0.01), fat attenuation (-84 HU versus -69 HU, P < 0.01), skeletal muscle index of 5.2% (40.1 cm2/m2 versus 42.2 cm2/m2, P < 0.01), muscle area of 5.1% (117 cm2 versus 123 cm2, P < 0.01), and steatotic muscle area of 12.9% (31 cm2 versus 35 cm2, P < 0.01). CONCLUSION: Tube potential significantly affects body segmentation in contrast-enhanced CT.

Chest pain CT in the Emergency Department: evaluating the coronary arteries even when not specifically asked for?

Background Computed tomography (CT) for excluding acute aortic syndrome (AAS) and pulmonary embolism (PE) simultaneously in patients with chest pain could be used to exclude coronary artery disease (CAD). Purpose To evaluate the frequency of further testing for CAD in patients receiving a CT in the emergency department (ED) for simultaneous evaluation for AAS and PE. Material and Methods This retrospective study was conducted over a three-year period including all patients with acute chest pain visiting our ED. All patients were included that received an electrocardiography (ECG)-gated CT of the entire chest enquiring simultaneously for AAS and PE. Those patients were followed up for 30 days after their initial ED visit whether they received further testing for CAD. Results Within the study period, a total of 157 patients with acute chest pain received a chest pain CT for simultaneous evaluation of both AAS and PE. Image quality was deemed sufficient to evaluate the coronary arteries in 80% of the patients. Thirty-seven patients (24%) underwent additional testing for CAD within 30 days of their ED visit, including catheter coronary angiography (n = 25), cardiac-stress single-photon emission-CT (n = 6), and cardiac magnetic resonance imaging (MRI) (n = 6). Conclusion Of patients presenting to the ED with acute chest pain who received a chest pain CT for simultaneous evaluation of AAS and PE, 24% had further imaging for CAD within 30 days of the initial ED visit. Immediate evaluation of the coronary arteries as part of a chest pain CT should be considered here for not delaying diagnosis.

Noise Texture Deviation: A Measure for Quantifying Artifacts in Computed Tomography Images With Iterative Reconstructions.

OBJECTIVES: The aims of this study were to introduce the measure noise texture deviation as quantitative parameter for evaluating iterative reconstruction (IR)-specific artifacts in computed tomography (CT) images and to test whether IR-specific artifacts, quantified through this measure, are reduced in advanced modeled IR (ADMIRE) as compared with sinogram-affirmed IR (SAFIRE) images of the liver ex vivo and in patients with hypodense liver lesions. MATERIALS AND METHODS: In the ex vivo study part, an abdominal phantom was used. In the institutional review board-approved in vivo study part, 40 consecutive patients (mean age, 63 years) with hypodense liver lesions undergoing abdominal CT in the portal-venous phase were included. Images were reconstructed with filtered back projection, with the second-generation IR algorithm SAFIRE and with the third-generation IR algorithm ADMIRE. Noise power spectra and noise texture deviation were calculated in the phantom; image noise was measured in the phantom and in patients. Two blinded readers evaluated all image data regarding IR-specific artifacts (plastic-like, blotchy appearance); patient data were evaluated regarding conspicuity and confidence for detecting hypodense liver lesions. RESULTS: Image noise was significantly reduced at increasing IR levels (P < 0.001) with both algorithms, with no significant differences between corresponding strength levels of SAFIRE and ADMIRE (all, P > 0.05). Noise power spectra were similar at corresponding strength levels of SAFIRE and ADMIRE (all, P > 0.05). Noise texture deviation in ADMIRE was reduced compared with corresponding strength levels of SAFIRE (all, P < 0.001) and strongly correlated with subjective IR-specific artifacts (r = 0.88, P < 0.001). Iterative reconstruction-specific artifacts were significantly reduced in ADMIRE compared with that in SAFIRE images at strength levels 3 or greater, both ex vivo and in vivo (all, P < 0.001). There were no significant differences in the readers' ratings of lesion conspicuity and lesion confidence in detecting hypodense liver lesions between SAFIRE and ADMIRE (P > 0.05). Only lesion conspicuity was superior with SAFIRE and ADMIRE compared with filtered back projection (all, P < 0.001). CONCLUSIONS: Noise texture deviation is a quantitative measure reflecting IR-specific artifacts and is reduced in CT images with ADMIRE compared with SAFIRE.

CT Angiography of the Aorta: Prospective Evaluation of Individualized Low-Volume Contrast Media Protocols.

Purpose To prospectively develop individualized low-volume contrast media (CM) protocols adapted to tube voltage in patients undergoing computed tomographic (CT) angiography of the aorta. Materials and Methods The study was approved by the institutional review board and local ethics committee. All patients provided written informed consent. CT angiography was performed by using automated attenuation-based tube voltage selection (ATVS) (range, 70-150 kVp; 10-kVp increments). Iodine attenuation curves from an ex vivo experiment in a phantom were used to design CM protocols for CT angiography of the thoracoabdominal aorta in 129 consecutive patients (hereafter, cohort A). Further modified CM protocols based on results in cohort A were designed with the aim of homogeneous vascular attenuation of 300-350 HU across tube voltages and were applied to another 61 consecutive patients (cohort B). Three independent blinded radiologists assessed subjective image quality, and one reader determined objective image quality. The Kruskal-Wallis test was performed to test for differences in subjective image quality, and linear regression was performed to test for differences in objective image quality between the automatically selected tube voltages. Results Experiments revealed tube voltage-dependent iodine attenuation curves, which were used to determine the CM protocols in cohort A; these ranged from 68 mL at 110 kVp to 45 mL at 80 kVp. In both cohorts, ATVS selected 80 kVp in 62 patients, 90 kVp in 84, 100 kVp in 33, and 110 kVp in 11. In cohort A, image quality that was satisfactory or better was attained in 126 (98%) of 129 patients who had no significant differences in subjective image quality between tube voltages (P = .106) but who did have significant differences in attenuation and contrast-to-noise ratio (CNR) (P < .001 for both). In cohort B, the further-modified CM protocol (from 33 mL at 80 kVp to 68 mL at 110 kVp) yielded image quality that was satisfactory or better in all 61 (100%) patients, without significant differences in subjective image quality (P = .178), and without significant differences between tube voltage and attenuation (P = .108), noise (P = .250), or CNR (P = .698). Conclusion Individualized low-volume CM protocols based on automatically selected tube voltages are feasible and yield diagnostic image quality for CT angiography of the aorta. (©) RSNA, 2016 Online supplemental material is available for this article.

Feasibility of Dose Optimization in a Second-Generation Dual-Source CT Scanner for a Manufacturer-Recommended Urolithiasis Protocol for Imaging Renal Stones.

OBJECTIVE: The purpose of this article is to investigate the magnitude of dose optimization for a manufacturer-recommended urolithiasis protocol in a second-generation dual-source CT scanner. MATERIALS AND METHODS: Custom renal phantoms with 24 stones were scanned using the manufacturer-provided dual-energy CT protocol (tube A, 100 kVp and 210 reference mAs; tube B, 140 kVp and 162 reference mAs) and seven dose-optimized protocols in which the reference tube current-time product setting of tube A was reduced stepwise by 20 mAs. Detection and characterization of the stones was assessed. In the patient study, 25 patients underwent the manufacturer-provided dual-energy protocol and 25 patients underwent imaging with a dose-optimized protocol (tube A, 100 kVp and 90 reference mAs; tube B, 140 kVp and 70 reference mAs). Dose-length product (DLP), image noise, and contrast-to-noise ratio (CNR) were assessed. Subjective image quality was analyzed by three independent radiologists. RESULTS: In the phantom study, the reference tube current-time product of tube A could be reduced from 210 to 90 mAs without losing the accuracy of detection or characterization of the calculi. In the patient study, the dose-optimized protocol resulted in a significant reduction of the average DLP by 51% compared with the standard protocol (219.4 vs 443.5 mGy·cm, respectively; p = 0.0001). The image noise was higher, and the CNR was lower, in the dose-optimized group than in the standard-dose group (p < 0.05). The subjective overall image quality of the dose-optimized CT examinations was rated as good, and that of the standard-dose CT examinations was rated as excellent (p = 0.001). CONCLUSION: The in vitro and in vivo assessment revealed a potential for a 51% dose reduction of the manufacturer-recommended dual-energy CT protocol for urolithiasis without compromising the accuracy.

Histogram Analysis of CT Perfusion of Hepatocellular Carcinoma for Predicting Response to Transarterial Radioembolization: Value of Tumor Heterogeneity Assessment.

PURPOSE: To evaluate in patients with hepatocellular carcinoma (HCC), whether assessment of tumor heterogeneity by histogram analysis of computed tomography (CT) perfusion helps predicting response to transarterial radioembolization (TARE). MATERIALS AND METHODS: Sixteen patients (15 male; mean age 65 years; age range 47-80 years) with HCC underwent CT liver perfusion for treatment planning prior to TARE with Yttrium-90 microspheres. Arterial perfusion (AP) derived from CT perfusion was measured in the entire tumor volume, and heterogeneity was analyzed voxel-wise by histogram analysis. Response to TARE was evaluated on follow-up imaging (median follow-up, 129 days) based on modified Response Evaluation Criteria in Solid Tumors (mRECIST). Results of histogram analysis and mean AP values of the tumor were compared between responders and non-responders. Receiver operating characteristics were calculated to determine the parameters' ability to discriminate responders from non-responders. RESULTS: According to mRECIST, 8 patients (50%) were responders and 8 (50%) non-responders. Comparing responders and non-responders, the 50th and 75th percentile of AP derived from histogram analysis was significantly different [AP 43.8/54.3 vs. 27.6/34.3 mL min(-1) 100 mL(-1)); p < 0.05], while the mean AP of HCCs (43.5 vs. 27.9 mL min(-1) 100 mL(-1); p > 0.05) was not. Further heterogeneity parameters from histogram analysis (skewness, coefficient of variation, and 25th percentile) did not differ between responders and non-responders (p > 0.05). If the cut-off for the 75th percentile was set to an AP of 37.5 mL min(-1) 100 mL(-1), therapy response could be predicted with a sensitivity of 88% (7/8) and specificity of 75% (6/8). CONCLUSION: Voxel-wise histogram analysis of pretreatment CT perfusion indicating tumor heterogeneity of HCC improves the pretreatment prediction of response to TARE.

Diagnostic Accuracy of Quantitative and Qualitative Phase-Contrast Imaging for the ex Vivo Characterization of Human Coronary Atherosclerotic Plaques.

PURPOSE: To investigate the accuracy of x-ray grating interferometry phase-contrast (PC) imaging for the characterization of human coronary artery plaque. MATERIALS AND METHODS: PC and conventional absorption computed tomographic (CT) imaging was performed ex vivo in this institutional review board-approved study in 40 human coronary artery segments by using a synchrotron radiation source. Qualitative analyses and calculations of image quality (McNemar test), plaque components (McNemar test), and plaque classification (Cohen κ test) according to the American Heart Association classification were performed in 38 plaques detected at histopathologic examination (reference standard). Quantitative measurements of plaque components (ie, collagen, lipids, smooth muscle, and calcifications) were compared among PC and absorption images by using analysis of variance for repeated measures with post hoc Bonferroni correction. RESULTS: Image quality was superior in PC (median image score, 1) in all cases (100%) compared with absorption imaging (median image score, 3) (P < .001). Plaque components were detected by means of PC without significant differences (seven of seven calcifications, 22 of 22 plaques with collagen and smooth muscle cells, P > .99; 29 of 29 plaques with lipids, P = .10) with histopathologic findings, whereas absorption imaging was used to detect calcifications (seven of seven, P > .99) without statistical differences only (nine of 29 plaques with lipids, 0 of 22 plaques with collagen and smooth muscle cells, P < .001). Accuracy for plaque stage assessment with PC (early vs advanced) was 100%, and characterization was correct in 33 of 38 plaques (87%), while conventional absorption imaging allowed correct characterization of seven plaques only (18%, P < .001). PC CT numbers were significantly different (P < .05) for all plaque components (mean for calcifications, 1236 HU ± 69; collagen, 78 HU ± 24; lipids, -18 HU ± 23; and smooth muscle cells, 34 HU ± 12), whereas absorption images showed significant differences (P < .001) between calcifications (1336 HU ± 241) and other plaque components, but not for collagen (22 HU ± 13), lipids (-15 HU ± 14), and smooth muscle (13 HU ± 9) (P > .99). CONCLUSION: PC imaging allows accurate characterization of human coronary artery plaques and quantitative assessment of plaque components, thereby outperforming absorption imaging.

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 60-90 bpm in 5-bpm steps was examined on a third-generation dual-source 192-slice CT (prospective ECG-triggering, pitch 3.2; rotation time, 250 ms). 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, 50 years) 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 1 mm or less. Distortion increased above 1 mm at HR of 80-90 bpm. Patients had a mean HR of 66 bpm (47-78 bpm). Coronary segments were of diagnostic image quality for all patients with HR up to 73 bpm. Average effective radiation dose in patients was 0.6 ± 0.3 mSv. 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 75 bpm while maintaining diagnostic image quality, being associated with an average radiation dose of 0.6 mSv. KEY POINTS: • CCTA is feasible with the turbo high-pitch mode. • Turbo high-pitch CCTA provides diagnostic image quality up to 73 bpm. • The radiation dose of high-pitch CCTA is 0.6 mSv 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 (90)yttrium microspheres in patients with liver metastases. METHODS: Forty consecutive patients with liver metastases undergoing RE were evaluated with multiphase CT, perfusion CT and (99m)Tc-MAA SPECT. Arterial perfusion (AP) from perfusion CT, HU values from the arterial (aHU) and portal venous phase (pvHU) CT, and (99m)Tc-MAA uptake ratio of metastases were determined. Morphologic response was evaluated after 4 months 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 < 0.001) and aHU (P = 0.001) of metastases, while no differences were found for pvHU (P = 0.07) and the (99m)Tc-MAA uptake ratio (P = 0.40). AP had a significantly higher specificity than aHU (P = 0.003) for determining responders to RE. Patients with an AP >20 ml/100 ml/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 (99m)Tc-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.