Hypodense liver lesions in patients with hepatic steatosis: do we profit from dual-energy computed tomography?

PURPOSE: To evaluate dual-energy CT (DECT) imaging of hypodense liver lesions in patients with hepatic steatosis, having a high incidence in the general population and among cancer patients receiving chemotherapy. METHODS: One hundred and five patients with hepatic steatosis (liver parenchyma <40 HU) underwent contrast-enhanced DECT with reconstruction of pure iodine (PI), optimum contrast (OC), 80 kVp, and 120 kVp-equivalent data sets. Image noise (IN), lesion to liver signal to noise (SNR) and contrast to noise (CNR) ratios were quantitatively analysed; image quality was rated on a 5-point scale (1, excellent; 2, good; 3, fair; 4, poor; 5, non-diagnostic) by two independent reviewers. RESULTS: In 21 patients with hypodense liver lesions, IN was lowest in PI followed by 120 kVp-equivalent and OC, and highest in 80 kVp. SNR was highest in PI (1.30), followed by 120 kVp-equivalent (0.72) and 80 kVp (0.63), and lowest in OC (0.55). CNR was highest in 120 kVp-equivalent (4.95), followed by OC (4.55) and 80 kVp (4.14), and lowest in PI (3.63). The 120 kVp-equivalent series exhibited best overall qualitative image score (1.88), followed by OC (1.98), 80 kVp (3.00) and PI (3.67). CONCLUSION: In our study, the 120 kVp-equivalent series was best suited for visualization of hypodense lesions within steatotic liver parenchyma, while using DECT currently seems to offer no additional diagnostic advantage. KEY POINTS: • Hepatic steatosis has high incidence in the general population and following chemotherapy. • Hypodense liver lesions can be obscured by steatotic liver parenchyma in CT. • Low kV p -CT shows no advantage in detecting hypodense lesions in steatotic livers. • Additional DECT image information does not improve visualization of hypodense lesions in steatosis. • 120 kV p -equivalent imaging yields best quantitative and qualitative image analysis results.

Combined Assessment of High-Sensitivity Troponin T and Noninvasive Coronary Plaque Composition for the Prediction of Cardiac Outcomes.

PURPOSE: To determine the risk-stratification ability of plaque volume and composition assessment with cardiac computed tomographic (CT) angiography and high-sensitivity troponin T (hsTnT) in patients at intermediate risk for coronary artery disease (CAD). MATERIALS AND METHODS: The study complied with the Declaration of Helsinki and was approved by the local ethics committee. All patients gave written informed consent. Five hundred twenty-one consecutive patients (mean age ± standard deviation, 62 years ± 10; 256 men and 265 women) were included in this prospective, observational, longitudinal, single-center study. Quantitative cardiac CT angiography analysis was performed in all patients (for 7690 coronary segments), whereas biomarkers (hsTnT and high-sensitivity C-reactive protein) were available in 408 patients (78%). To evaluate the incremental value of cardiac CT angiography and hsTnT for the prediction of cardiovascular events, multivariate Cox regression and integrated discrimination improvement analysis were applied. RESULTS: In 521 patients, 13 hard cardiac events occurred during a mean follow-up period of 2.3 years ± 1.1 (median, 2.4 years; range, 0.5-4.5 years), while 23 patients underwent late coronary revascularization. The Duke clinical score was 51% ± 30, indicating intermediate risk. The presence of no plaques or purely calcified versus noncalcified plaques, plaque volume according to tertiles, and increased hsTnT (≥14 pg/mL) was independently associated with hard cardiac events (hazard ratio [HR] = 26.08, 95% confidence interval [CI]: 2.78, 244.99; HR = 12.14, 95% CI: 1.87, 78.74; and HR = 10.31, 95% CI: 2.72, 39.0, respectively; P < .01 for all). Patients with increased hsTnT and plaque burden (n = 53) showed the highest incidence for hard cardiac events (annual rate, 12.7%), followed by those with either increased hsTnT or plaque burden (n = 145; annual rate = 0.44%, P < .03), while those with lower hsTnT and plaque burden exhibited excellent outcomes and no hard event during the follow-up duration (n = 210; annual rate = 0%, P < .001). CONCLUSION: Use of hsTnT as a marker of myocardial microinjury and cardiac CT angiography as a marker of the total atherosclerotic burden improves the prediction of cardiac outcome in patients with presumably stable CAD and may aid in personalized risk stratification in patients at intermediate risk.

When do we really need coronary calcium scoring prior to contrast-enhanced coronary computed tomography angiography? Analysis by age, gender and coronary risk factors.

AIMS: To investigate the value of coronary calcium scoring (CCS) as a filter scan prior to coronary computed tomography angiography (CCTA). METHODS AND RESULTS: Between February 2008 and April 2011, 732 consecutive patients underwent clinically indicated CCTA. During this 'control phase', CCS was performed in all patients. In patients with CCS≥800, CCTA was not performed. During a subsequent 'CCTA phase' (May 2011-May 2012) another 200 consecutive patients underwent CCTA, and CCS was performed only in patients with increased probability for severe calcification according to age, gender and atherogenic risk factors. In patients where CCS was not performed, calcium scoring was performed in contrast-enhanced CCTA images. Significant associations were noted between CCS and age (r = 0.30, p<0.001) and coronary risk factors (χ2 = 37.9; HR = 2.2; 95%CI = 1.7-2.9, p<0.001). Based on these associations, a ≤3% pre-test probability for CCS≥800 was observed for males <61 yrs. and females <79 yrs. According to these criteria, CCS was not performed in 106 of 200 (53%) patients during the 'CCTA phase', including 47 (42%) males and 59 (67%) females. This resulted in absolute radiation saving of ∼1 mSv in 75% of patients younger than 60 yrs. Of 106 patients where CCS was not performed, estimated calcium scoring was indeed <800 in 101 (95%) cases. Non-diagnostic image quality due to calcification was similar between the 'control phase' and the 'CCTA' group (0.25% versus 0.40%, p = NS). CONCLUSION: The value of CCS as a filter for identification of a high calcium score is limited in younger patients with intermediate risk profile. Omitting CCS in such patients can contribute to further dose reduction with cardiac CT studies.

In-vitro assessment of coronary artery stents in 256-multislice computed tomography angiography.

BACKGROUND: The important detection of in-stent restenosis in cardiovascular computed tomography (CT) is still challenging. The first study assessing the in-vitro stent lumen visualization of the state of the art 256-multislice CT (256-MSCT), which was performed by our research group, yielded promising results. As the applied technical approach is not suitable for daily routine, we assessed the capability of the 256-MSCT and its different reconstruction kernels for the coronary stent lumen visualization employing a clinically applicable technique in a phantom study. RESULTS: The XCD kernel showed significantly lower artificial lumen narrowing (ALN) values (overall ALN < 40%) than the other reconstruction kernels (CC, CD, XCB) irrespective of the stent caliber. The ALN of coronary stents with a diameter >3 mm was significantly lower than of stents with a smaller caliber. The ALN difference between stents with a diameter of 3 mm and smaller ones was not statistically significant. Yet, the lumen visualization of the smaller stents was impaired by a halo effect. The XCD kernel showed more constant attenuation values throughout the different stent diameters than the other reconstruction kernels. CONCLUSIONS: The 256-MSCT provides a good lumen visualization of coronary stents with a diameter >3 mm. The assessment of stents with a diameter of 3 mm seems feasible but has to be validated in further studies. The clinical evaluation of smaller stents cannot be recommended so far. The XCD kernel showed the best lumen visualization and should therefore be applied in addition to the standard cardiac reconstruction kernels when assessing coronary artery stents using 256-MSCT.

Detection of acute pulmonary embolism: feasibility of diagnostic accuracy of MRI using a stepwise protocol.

Multidetector computed tomography (MDCT) has become the imaging method of choice in patients suspected of having pulmonary embolism (PE) but has the inherent limitation of radiation dose and the side effects of contrast agents. The purpose of the study was to assess the feasibility of a stepwise MRI protocol in the clinical setting of acute PE. The stepwise approach should make it possible to diagnose acute PE in critically ill patients using fast MR sequences and included the option to add comprehensive sequences when patients were stable. Forty-five patients with acute PE (26 men, 19 women; 41 ± 16 years) were included in this prospective study. The diagnosis was initially confirmed by MDCT as gold standard. MRI at 1.5 T was subsequently performed without any delay in medical treatment. The MRI protocol proceeded stepwise from robust to detailed imaging techniques (i.e., from TrueFISP and single shot HASTE sequence to MR perfusion and 3D-MR angiography) if the patient was able to tolerate additional imaging time. Diagnostic accuracy was evaluated on the central (lobar) and peripheral (segmental) levels. The complete MR protocol was applied in 40 of the 45 patients (88 %). In the remaining five patients with severe dyspnea the diagnosis of acute PE was established by using fast TrueFISP sequences that were insensitive to respiratory movement. All five patients suffered from a major central PE. Highest sensitivity was achieved by MR perfusion (lobar, 98 %; segmental, 95 %). Real-time TrueFISP and MR angiography showed the highest specificity (lobar, 90-100 %; segmental, 95-97 %). The combination of all MR sequences matched closely the results of MDCT (lobar: sensitivity 98 %, specificity 100 %; segmental: sensitivity 95 %, specificity 97 %). MRI using a stepwise protocol is a promising approach for diagnosing acute PE. The protocol can be tailored for dyspneic patients with central PE using real-time MRI sequences. The diagnostic accuracy for peripheral PE can be improved by using combined MR techniques, achieving comparable results to MDCT.

Complications in CT-guided procedures: do we really need postinterventional CT control scans?

PURPOSE: The aim of this study is twofold: to determine the complication rate in computed tomography (CT)-guided biopsies and drainages, and to evaluate the value of postinterventional CT control scans. METHODS: Retrospective analysis of 1,067 CT-guided diagnostic biopsies (n = 476) and therapeutic drainages (n = 591) in thoracic (n = 37), abdominal (n = 866), and musculoskeletal (ms) (n = 164) locations. Severity of any complication was categorized as minor or major. To assess the need for postinterventional CT control scans, it was determined whether complications were detected clinically, on peri-procedural scans or on postinterventional scans only. RESULTS: The complication rate was 2.5 % in all procedures (n = 27), 4.4 % in diagnostic punctures, and 1.0 % in drainages; 13.5 % in thoracic, 2.0 % in abdominal, and 3.0 % in musculoskeletal procedures. There was only 1 major complication (0.1 %). Pneumothorax (n = 14) was most frequent, followed by bleeding (n = 9), paresthesia (n = 2), material damage (n = 1), and bone fissure (n = 1). Postinterventional control acquisitions were performed in 65.7 % (701 of 1,067). Six complications were solely detectable in postinterventional control acquisitions (3 retroperitoneal bleeds, 3 pneumothoraces); all other complications were clinically detectable (n = 4) and/or visible in peri-interventional controls (n = 21). CONCLUSION: Complications in CT-guided interventions are rare. Of these, thoracic interventions had the highest rate, while pneumothoraces and bleeding were most frequent. Most complications can be detected clinically or peri-interventionally. To reduce the radiation dose, postinterventional CT controls should not be performed routinely and should be restricted to complicated or retroperitoneal interventions only.

Computed tomography angiography of coronary artery bypass grafts: robustness in emergency and clinical routine settings.

BACKGROUND: There is a high probability for presence of irregular heart rates and artifacts in patients with previous coronary artery bypass graft (CABG) surgery. Previously reported diagnostic performance of ECG-gated 64-slice dual-source computer tomography angiography (CTA) in this patient group is based on pre-selection for normal heart rate and routine clinical setting. PURPOSE: To investigate image quality and diagnostic performance of CTA in patients with previous CABG surgery in various clinical settings. MATERIAL AND METHODS: Fifty-six non-selected, consecutive patients (110 grafts, 44 arterial, 66 venous) with previous CABG surgery were prospectively examined using a dual-source 64-slice CT (Siemens Definition, Forchheim, Germany) without utilization of CT-related pharmaceutical heart rate control. Patients were stratified according to the clinical setting: planned redo-cardiac surgery; emergency CTA within 30 days after CABG surgery; routine follow-up after CABG surgery. A reference standard was available for 30 patients (53.6%; 67/110 grafts). Image quality, artifacts, and graft patency were independently assessed by two observers. RESULTS: All CTAs were diagnostic despite the presence of irregular heart rhythm (25% of cases) and artifacts (72.7% of grafts). CTA was accurate in all patient groups in assessing graft patency (97.9% sensitivity; 100% specificity; 98.5% accuracy) but artifacts decreased diagnostic performance for stenosis detection (60% sensitivity; 88.6% specificity; 84.1% accuracy). Arterial grafts exhibited more surgical clip artifacts compared to venous grafts, which predominantly showed motion artifacts. Overall diagnostic quality was rated excellent in 70.9%/56.4%, good in 23.4%/39.1%, and sufficient in 5.5%/4.5% by each observer, respectively. CTA detected acute findings in 10 cases (graft bleeding, graft occlusion, pericardial hematoma, sternal instability with retrosternal abscess formation, pericardial effusion, left ventricle thrombus) in the emergency group; seven cases required surgical revision. CONCLUSION: Dual-source CTA is a robust and accurate method for assessment of graft patency and detection of relevant extra-cardiac pathologies in a non-selected patient population after CABG surgery in routine as well as emergency clinical settings. Artifacts caused by irregular heart rhythm or surgical clips do not impair graft patency evaluation but limit stenosis assessment.

Quantitative analysis of left ventricular strain using cardiac computed tomography.

OBJECTIVES: To investigate whether cardiac computed tomography (CCT) can determine left ventricular (LV) radial, circumferential and longitudinal myocardial deformation in comparison to two-dimensional echocardiography in patients with congestive heart failure. BACKGROUND: Echocardiography allows for accurate assessment of strain with high temporal resolution. A reduced strain is associated with a poor prognosis in cardiomyopathies. However, strain imaging is limited in patients with poor echogenic windows, so that, in selected cases, tomographic imaging techniques may be preferable for the evaluation of myocardial deformation. METHODS: Consecutive patients (n=27) with congestive heart failure who underwent a clinically indicated ECG-gated contrast-enhanced 64-slice dual-source CCT for the evaluation of the cardiac veins prior to cardiac resynchronization therapy (CRT) were included. All patients underwent additional echocardiography. LV radial, circumferential and longitudinal strain and strain rates were analyzed in identical midventricular short axis, 4-, 2- and 3-chamber views for both modalities using the same prototype software algorithm (feature tracking). Time for analysis was assessed for both modalities. RESULTS: Close correlations were observed for both techniques regarding global strain (r=0.93, r=0.87 and r=0.84 for radial, circumferential and longitudinal strain, respectively, p<0.001 for all). Similar trends were observed for regional radial, longitudinal and circumferential strain (r=0.88, r=0.84 and r=0.94, respectively, p<0.001 for all). The number of non-diagnostic myocardial segments was significantly higher with echocardiography than with CCT (9.6% versus 1.9%, p<0.001). In addition, the required time for complete quantitative strain analysis was significantly shorter for CCT compared to echocardiography (877±119 s per patient versus 1105±258 s per patient, p<0.001). CONCLUSION: Quantitative assessment of LV strain is feasible using CCT. This technique may represent a valuable alternative for the assessment of myocardial deformation in selected patients with poor echogenic windows and general contraindications for magnetic resonance imaging.

Objective quantification of aortic valvular structures by cardiac computed tomography angiography in patients considered for transcatheter aortic valve implantation.

PURPOSE: To test the ability of a model-based segmentation of the aortic root for consistent assessment of aortic valve structures in patients considered for transcatheter aortic valve implantation (TAVI) who underwent 256-slice cardiac computed tomography (CT). METHODS: Consecutive patients (n = 49) with symptomatic severe aortic stenosis considered for TAVI and patients without aortic stenosis (n = 17) underwent cardiac CT. Images were evaluated by two independent observers who measured the diameter of the aortic annulus and its distance to both coronary ostia (1) manually and (2) software-assisted. All acquired measures were compared with each other and to (3) fully automatic quantification. RESULTS: High correlations were observed for 3D measures of the aortic annulus conducted on multiple oblique planes (r = 0.87 and 0.84 between observers and model-based measures, and r = 0.81 between observers). Reproducibility was further improved by software-assisted versus manual assessment for all the acquired variables (r = 0.98 versus 0.81 for annulus diameter, r = 0.94 versus 0.85 for distance to the left coronary ostium, P < 0.01 for both). Thus, using software-assisted measurements very low limits of agreement were observed for the annulus diameter (95%CI of -1.2 to 0.6 mm) and within very low time-spent (0.6 ± 0.1 min for software-assisted versus 1.6 ± 0.3 min per patient for manual assessment, P < 0.001). Assessment of the aortic annulus using the 3D model-based instead of manual 2D-coronal measurements would have modified the implantation strategy in 12 of 49 patients (25%) with aortic stenosis. Four of 12 patients with potentially modified implantation strategy yielded postprocedural moderate paravalvular regurgitation, which may have been avoided by implantation of a larger prosthesis, as suggested by automatic 3D measures. CONCLUSION: Our study highlights the usefulness of software-assisted preprocedural assessment of the aortic annulus in patients considered for TAVI.

Performance of dual source versus 256-slice multi-slice CT in the evaluation of 16 coronary artery stents.

INTRODUCTION: Invasive coronary angiography is the reference method for identification of in-stent restenosis (ISR) bearing the disadvantages of high costs and invasiveness. New approaches like dual-source CT (DSCT) and 256-multi-slice CT (256-MSCT) may potentially be the future methods of choice to reliably exclude ISR in patients with low or intermediate risk of restenosis. We sought to compare the performance of DSCT and 256-MSCT for the in vitro assessment of stent lumen diameter and basic scan parameters in stents of various diameters and designs. MATERIALS AND METHODS: In 16 coronary artery stents we evaluated relative in-stent lumen diameter, attenuation, noise, attenuation-/signal-to-noise ratio (ANR/SNR) and radiation dose (CTDIvol) in an acknowledged coronary vessel in vitro phantom (iodine-filled plastic tubes) with DSCT (Siemens, SOMATOM Definition, collimation=2×64×0.6mm, pitch=0.26, current=400mAs/rot, voltage=120kV, tube-rotation-time=330ms) and 256-MSCT (Philips Brilliance, iCT, tube collimation=2×128×0.625mm, pitch=0.18, current=800mAseff, voltage=120kV, tube-rotation-time=270ms). Diameter analysis was conducted with the observer-independent full-width-at-half-maximum (FWHM) technique. RESULTS: DSCT and 256-MSCT revealed similar stent lumen diameters (50.7±7.2% vs. 50.8±7.4%, p=0.98). Attenuation (-19±25HU vs. 54±29HU), ANR (-0.9±1.2 vs. 2.9±1.8) and SNR (12.1±2.4 vs. 17.4±1.9) were better in the DSCT (all p<0.001) at the expense of significantly higher radiation doses (CTDIvol=87 vs. 51mGy, p<0.01). Noise was comparable (21±2HU vs. 20±2HU, p=n.s.). Only stents with a diameter >3mm allowed sufficient stent lumen assessment in both scanners and showed a relative lumen diameter of 60-66%. CONCLUSIONS: The measured stent lumen diameter and image noise were similar in both scanners. Yet the DSCT offered a more truthful stent lumen visualization at the cost of higher radiation dose. Applying the FWHM approach only stents with a diameter >3mm offered sufficient stent lumen assessment.

Body mass index-adapted prospective coronary computed tomography angiography. Determining the lowest limit for diagnostic purposes.

PURPOSE: To investigate the value of 4 different protocols for prospectively triggered 256-slice coronary computed tomography angiography (coronary CTA). METHODS: Two hundred and ten patients underwent prospectively triggered coronary CTA for suspected or known coronary artery disease (CAD). Patients with heart rate >75 bps before the scan despite ß-blocker administration and with arrhythmia were excluded. From January to September 2010, 60 patients underwent coronary CTA using a non-tailored protocol (120 kV; 200 mAs) and served as our 'control' group. From September 2010 to April 2012, based on the body mass index (BMI) of the examined patients (BMI subgroups of <25; 25-28; 28-30, and ≥ 30 kg/m(2)) current tube voltage and tube current were: (1) slightly, (2) moderately or (3) strongly reduced, resulting into the 3 following BMI-adapted acquisition groups: (1) a 'standard' (100/120 kV; 100-200 mAs; n=50), 2) a 'low dose' (100/120 kV; 75-150 mAs; n=50), and 3) an 'ultra-low dose' (100/120 kV; 50-100 mAs; n=50) protocol. RESULTS: Patients examined using the non-tailored protocol exhibited the highest radiation exposure (3.2 ± 0.4 mSv), followed by the standard (1.6 ± 0.7 mSv), low-dose (1.2 ± 0.6 mSv) and ultra-low dose protocol (0.7 ± 0.3 mSv) (radiation savings of 50%, 63% and 78% respectively). Overall image quality was similar with standard dose (1.9 ± 0.6) and low-dose (2.0 ± 0.5) compared to the non-tailored group (1.9 ± 0.5) (p=NS for all). In the ultra-low dose group however, image quality was significant reduced (2.7 ± 0.6), p<0.05 versus all other groups). CONCLUSION: Using BMI-adapted low dose acquisitions image quality can be maintained with simultaneous radiation savings of ∼65% (dose of ∼1 mSv). This appears to be the lower limit for diagnostic coronary CTA, whereas ultra-low dose acquisitions result in significant image degradation.

Diagnosing and staging of cystic echinococcosis: how do CT and MRI perform in comparison to ultrasound?

BACKGROUND: Imaging plays the key role in diagnosing and staging of CE. The description of CE-specific imaging features and the WHO CE cyst classification is based on ultrasound. The reproducibility of the ultrasound-defined features of CE cysts is variable in MR- and CT-imaging. This is of particular importance for cysts that are not accessible by US and because of the increasing availability and overuse of CT and MR imaging. METHODOLOGY/PRINCIPAL FINDINGS: Retrospective analysis of patients with abdominal CE cysts of an interdisciplinary CE clinic who had CT and/or MRI scans performed additionally to US imaging. All images were read and interpreted by the same senior radiologist experienced in the diagnosis of CE. US, CT and MR images were staged according to the WHO classification criteria. The agreement beyond chance was quantified by kappa coefficients (κ). 107 patients with 187 CE cysts met the inclusion criteria. All cysts were assessed by US, 138 by CT, and 125 by MRI. The level of agreement beyond chance of the individual CE stages 1-4 was clearly lower for CT, with κ ranging from 0.62 to 0.72, compared to MRI with values of κ between 0.83 and 1.0. For CE5 cysts CT (κ = 0.95) performed better than MRI (κ = 0.65). CONCLUSIONS: Ultrasound remains the corner stone of diagnosis, staging and follow up of CE cysts. MRI reproduces the ultrasound-defined features of CE better than CT. If US cannot be performed due to cyst location or patient-specific reasons MRI with heavily T2-weighted series is preferable to CT.

Portomesenteric venous gas: is gas distribution linked to etiology and outcome?

PURPOSE: To investigate various anatomical locations of portomesenteric venous gas detected by computed tomography (CT) and their relationship with the underlying etiology and the outcome. METHODS: The study group consisted of 47 cases with evidence of portomesenteric venous gas detected on abdominal CT examinations, 12 cases were identified through a retrospective PACS search, 35 were prospectively included. The presence of gas at specific anatomical locations in the portomesenteric venous vasculature was assessed according to a pre-defined classification: the arcade vessels close to the bowel segments followed by segmental vessels, the superior mesenteric vein, the extra- and intrahepatic portal vein. The etiology of portomesenteric venous gas and its prognosis were assessed by review of surgical reports, histopathology and medical records. Surgery was performed on 30 patients. RESULTS: Overall 68.1% of cases were of ischemic etiology. Gas present in the arcade vessels was the best indicator for ischemia (sensitivity 93.8%; specificity 70.0%, positive predictive value 90.9%, negative predictive value 77.8%) compared to other locations and the mere presence of portomesenteric gas independent from the location. The overall mortality rate was 53.2%. Only gas in the arcade and segmental vessels were associated with considerably higher mortality rates (65.8% and 75.0%, respectively) and acceptable frequency (occurrence in 80.9% and 59.6%, respectively). CONCLUSIONS: The study results indicate that the presence of gas at specific anatomical locations in the portomesenteric venous system, namely the arcade and segmental vessels, may serve as strong indicator for ischemic etiology and poor prognosis in the assessment of individual cases.

MR relaxometry of the liver: significant elevation of T1 relaxation time in patients with liver cirrhosis.

OBJECTIVES: To evaluate hepatic relaxation times T1, T2 and T2* in healthy subjects and patients with liver cirrhosis stratified by the Child-Pugh classification (CPC). METHODS: Sixty-one consecutive patients were stratified by CPC (class A026; B020; C015) and compared with age-matched controls (n = 31). Relaxometry measurements were performed at 1.5 T using six saturation recovery times (200-3,000 ms) to determine liver T1, six echo times (TE 14-113 ms) for T2 and eight TE (4.8-38 ms) for T2* assessment. Signal intensities in selected regions of interest in the liver parenchyma were fitted to theoretical models with least squares minimisation algorithms to determine T1, T2 and T2*. RESULTS: The most significant difference was the higher T1 values (852 ± 132 ms) in cirrhotic livers compared with controls (678 ± 45 ms, P < 0.0001). A less significant difference was seen for T2* (23 ± 5 vs. 26 ± 7 ms). Subdifferentiation showed a statistically significant difference between control group and individual CPC classes as well as between class C and classes A or B for T1 relaxation times. CONCLUSION: Measurement of T1 relaxation time can differentiate healthy subjects from patients with liver cirrhosis, and can distinguish between mild/moderate disease (CPC A/B) and advanced disease (CPC C). KEY POINTS: • Significantly elevated magnetic resonance T1 relaxation times are found in liver cirrhosis. • T1 relaxation times can distinguish healthy subjects from patients with liver cirrhosis. • T1 relaxation times can distinguish Child-Pugh classes Aand B from C.

Detection and size of pulmonary lesions: how accurate is MRI? A prospective comparison of CT and MRI.

BACKGROUND: Although CT is the modality of choice for morphological lung imaging, an increasing proportion of chest imaging is performed by MRI due to the utilization of whole-body MRI. Therefore, the diagnostic performance of MRI in reliably detecting pulmonary lesions should be established. PURPOSE: To investigate the detection rate of pulmonary lesions by MRI that can be expected in a clinical setting and to assess the accuracy of lesion measurement by MRI compared to CT. MATERIAL AND METHODS: Twenty-eight patients (median age 66 years) with indication for CT imaging due to suspected thoracic malignancy were prospectively included. Chest MRI performed on the same day as CT, comprised unenhanced TrueFisp, ecg-gated T2-weighted HASTE, T1-weighted VIBE, and contrast-enhanced T1-weighted, fat-saturated VIBE sequences. MR sequences were evaluated for lesion detection by two readers independently and measurement of lesion size was performed. MR findings were correlated with CT. RESULTS: One hundred and eight pulmonary lesions (20 thoracic malignancies, 88 lung nodules) were detected by CT in 26 patients. Lesions were ruled out in two patients. All thoracic malignancies were identified by MRI with strong correlation (r = 0.97-0.99; P < 0.01) in lesion size measurement compared to CT. Unenhanced, T1-weighted VIBE correctly classified 94% of thoracic malignancies into T-stages. Contrast-enhanced, T1-weighted VIBE performed best in identifying 36% of lung nodules, 40% were detected combining unenhanced and contrast-enhanced T1-weighted VIBE. Detection rate increased to 65% for the combined sequences regarding lesions ≥5 mm. Lesion size measurement by all MR sequences strongly correlated with CT (r = 0.96-0.97; P = 0.01). CONCLUSION: MRI is as accurate as CT in detection and size measurement of primary thoracic malignancies >1 cm in diameter. If a lung lesion is detected by MRI, it is a reliable finding and its measurement is accurate. CT remains superior in detecting small lung nodules (<6 mm). Detection rate of MRI for small lesions is improved using a multi-sequence protocol including contrast administration.

Quantitative analysis of left ventricular dyssynchrony using cardiac computed tomography versus three-dimensional echocardiography.

OBJECTIVES: We investigated whether cardiac computed tomography (CCT) can determine intraventricular dyssynchrony in comparison to real-time three-dimensional echocardiography (RT3DE) in patients who are considered for cardiac resynchronisation therapy (CRT). METHODS: 35 patients considered for CRT were examined. Left ventricular (LV) dyssynchrony was quantified by calculating the standard deviation index (SDI) of 17 myocardial LV segments by RT3DE and ECG-gated contrast-enhanced 64-slice dual-source CCT. For both analyses the same software algorithm (4D LV-Analysis) was used. RESULTS: Close correlations were observed for end-systolic volume, end-diastolic volume and LV ejection fraction between the two techniques (r = 0.94, r = 0.92 and r = 0.95, respectively, P < 0.001 for all). For the global dyssynchrony index SDI, a high correlation was found between RT3DE and CCT (r = 0.84, P < 0.001), which further increased after exclusion of segments with poor image quality by echocardiography (r = 0.90, P < 0.001). The required time for quantitative analysis was significantly shorter (162 ± 22 s vs. 608 ± 112 s per patient, P < 0.001) and reproducibility was significantly higher for CCT compared with RT3DE (interobserver variability of 4.5 ± 3.1% vs. 7.9 ± 6.1%, P < 0.05). CONCLUSION: Quantitative assessment of LV dyssynchrony is feasible by CCT. Owing to its higher reproducibility and faster analysis time compared with RT3DE, this technique may represent a valuable alternative for dyssynchrony assessment. KEY POINTS: • Quantitative assessment of left ventricular dyssynchrony is feasible by cardiac computed tomography (CCT). • This technique has been compared with real-time three-dimensional echocardiography (RT3DE). • Reproducibility is significantly higher for CCT compared with RT3DE. • Time spent for analysis is significantly shorter for CCT. • Computed tomography may represent a valuable alternative to ultrasound for dyssynchrony assessment.

Evaluation of bowel peristalsis by dynamic cine MRI: detection of relevant functional disturbances--initial experience.

PURPOSE: To investigate the diagnostic performance of a cine magnetic resonance imaging (MRI) sequence in the visualization and detection of impaired bowel peristalsis. MATERIALS AND METHODS: In all, 91 consecutive patients (mean age 45 years) were prospectively examined on a 1.5 T system and stratified into a surgery group (n = 22) and a nonsurgery group (n = 69). A coronal fast imaging with steady-state precession (TrueFISP) sequence with 30 acquisitions per slice covered the abdomen in 10-15 slices each 7-12 mm thick (temporal resolution: 6-8 sec per frame). Image evaluation for reduced bowel peristalsis and relevant bowel stenosis was compared to surgical findings or clinical follow-up. RESULTS: Cine MRI reached 96% accuracy (94% sensitivity; 100% specificity) in detecting a relevant reduction in bowel peristalsis and 85% of relevant stenosis was identified in the surgery group. Twenty of 69 patients of the nonsurgery group showed reduced peristalsis on cine MR which was attributed to underlying disease; 49/69 patients in this group had no findings on cine MR and were uneventfully followed up. CONCLUSION: Cine MRI of the bowel provides functional information of bowel passage. The visualization of a reduction in peristalsis may improve the assessment of the functional impact of suspected bowel adhesions or stenosis. Standard bowel MR protocols can be easily complemented by cine MR, extending scan time by <4 minutes.

Reduction of radiation exposure and improvement of image quality with BMI-adapted prospective cardiac computed tomography and iterative reconstruction.

PURPOSE: To assess the impact of body mass index (BMI)-adapted protocols and iterative reconstruction algorithms (iDose) on patient radiation exposure and image quality in patients undergoing prospective ECG-triggered 256-slice coronary computed tomography angiography (CCTA). METHODS: Image quality and radiation exposure were systematically analyzed in 100 patients. 60 Patients underwent prospective ECG-triggered CCTA using a non-tailored protocol and served as a 'control' group (Group 1: 120 kV, 200 mAs). 40 Consecutive patients with suspected coronary artery disease (CAD) underwent prospective CCTA, using BMI-adapted tube voltage and standard (Group 2: 100/120 kV, 100-200 mAs) versus reduced tube current (Group 3: 100/120 kV, 75-150 mAs). Iterative reconstructions were provided with different iDose levels and were compared to filtered back projection (FBP) reconstructions. Image quality was assessed in consensus of 2 experienced observers and using a 5-grade scale (1=best to 5=worse), and signal- and contrast-to-noise ratios (SNR and CNR) were quantified. RESULTS: CCTA was performed without adverse events in all patients (n=100, heart rate of 47-87 bpm and BMI of 19-38 kg/m2). Patients examined using the non-tailored protocol in Group 1 had the highest radiation exposure (3.2±0.4 mSv), followed by Group 2 (1.7±0.7 mSv) and Group 3 (1.2±0.6 mSv) (radiation savings of 47% and 63%, respectively, p<0.001). Iterative reconstructions provided increased SNR and CNR, particularly when higher iDose level 5 was applied with Multi-Frequency reconstruction (iDose5 MFR) (14.1±4.6 versus 21.2±7.3 for SNR and 12.0±4.2 versus 18.1±6.6 for CNR, for FBP versus iDose5 MFR, respectively, p<0.001). The combination of BMI adaptation with iterative reconstruction reduced radiation exposure and simultaneously improved image quality (subjective image quality of 1.4±0.4 versus 1.9±0.5 for Group 2 reconstructed using iDose5 MFR versus Group 1 reconstructed using FBP, p<0.05). CONCLUSIONS: Prospective ECG-triggered 256-slice CCTA allows for visualization of the coronary artery tree with high image quality within a wide range of heart rates and BMIs. The combination of BMI-adapted protocols with iterative reconstruction algorithms can reduce radiation exposure for the patients and simultaneously improve image quality.

Single coronary artery with anomalous rising of the right coronary artery: a rare coronary anomaly diagnosed by 256-multidetector computed tomography.

Herein we report the diagnostic potential of cardiac computed tomography (cCT) to delineate the origin and course of an anomalous right coronary artery (RCA) originating from the midpart of the left anterior descended artery (LAD) in an adult with no other form of congenital heart disease. The patient was referred to our institution due to exertional dyspnea and suspected coronary artery disease. The patient underwent X-ray coronary angiography, and no high grade lesions were observed in the left coronary vessels. In the course of the mid-left-anterior-descending artery (LAD), an anomalous side branch coursing away from the left circumflex coronary artery (LCX) was observed, while a right coronary ostium could not be depicted. cCT confirmed the absence of a right coronary ostium, and the vessel originating from the mid LAD was identified as an anomalous RCA, which coursed anterior of the aorta and the pulmonary trunk.

Model-based segmentation and motion analysis of the thoracic aorta from 4D ECG-gated CTA images.

Pathologies of the thoracic aorta can alter the shape and motion pattern of the aorta throughout the cardiac cycle. For diagnosis and therapy planning, determination of the aortic shape and motion is important. We introduce a new approach for segmentation and motion analysis of the thoracic aorta from 4D ECG-CTA images, which combines spatial and temporal tracking, motion determination by intensity-based matching, and 3D fitting of vessel models. The approach has been successfully applied to 30 clinically relevant 4D CTA image sequences. We have also performed a quantitative evaluation of the segmentation accuracy.