Characterization of Severe Arterial Phase Respiratory Motion Artifact on Gadoxetate Disodium-Enhanced MRI - Assessment of Interrater Agreement and Reliability.

PURPOSE: To assess the interrater agreement and reliability of experienced abdominal radiologists in the characterization and grading of arterial phase gadoxetate disodium-related respiratory motion artifact on liver MRI. MATERIALS AND METHODS: This prospective multicenter study was initiated by the working group for abdominal imaging within the German Roentgen Society (DRG), and approved by the local IRB of each participating center. 11 board-certified radiologists independently reviewed 40 gadoxetate disodium-enhanced liver MRI datasets. Motion artifacts in the arterial phase were assessed on a 5-point scale. Interrater agreement and reliability were calculated using the intraclass correlation coefficient (ICC) and Kendall coefficient of concordance (W), with p < 0.05 deemed significant. RESULTS: The ICC for interrater agreement and reliability were 0.983 (CI 0.973 - 0.990) and 0.985 (CI 0.978 - 0.991), respectively (both p < 0.0001), indicating excellent agreement and reliability. Kendall's W for interrater agreement was 0.865. A severe motion artifact, defined as a mean motion score ≥ 4 in the arterial phase was observed in 12 patients. In these specific cases, a motion score ≥ 4 was assigned by all readers in 75 % (n = 9/12 cases). CONCLUSION: Differentiation and grading of arterial phase respiratory motion artifact is possible with a high level of inter-/intrarater agreement and interrater reliability, which is crucial for assessing the incidence of this phenomenon in larger multicenter studies. KEY POINTS: · Inter- and intrarater agreement for motion artifact scoring is excellent among experienced readers.. · Interrater reliability for motion artifact scoring is excellent among experienced readers.. · Characterization of severe motion artifacts proved feasible in this multicenter study.. CITATION FORMAT: · Ringe KI, Luetkens JA, Fimmers R et al. Characterization of Severe Arterial Phase Respiratory Motion Artifact on Gadoxetate Disodium-Enhanced MRI - Assessment of Interrater Agreement and Reliability. Fortschr Röntgenstr 2017; 190: 341 - 347.

Diffusion-weighted imaging in the assessment of prostate cancer: Comparison of zoomed imaging and conventional technique.

PURPOSE: To compare reduced field-of-view (zoomed) diffusion-weighted imaging (DWI) and conventional DWI in the evaluation of prostate cancer with respect to lesion detection, image quality and alignment accuracy. MATERIAL AND METHODS: The study was carried out in accordance with the Declaration of Helsinki and was approved by the institutional review board. Image data of 29 histology-proven prostate cancer lesions in 15 patients were evaluated. All patients underwent both conventional DWI and zoomed DWI at 3T. Zoomed DWI and conventional DWI sequences were analysed qualitatively and quantitatively. Subjective image quality, visual distortion and presence of artefacts were rated on a 5-point Likert scale (1=excellent) by two readers in consensus. Lesion conspicuity, sensitivity and specificity in lesion detection were evaluated and compared for both DWI sequences using ROC curves and area under the curve (AUC). To analyze the geographic distortion in DWI the alignment accuracy of prostate and lesions was measured in three spatial dimensions referring to the T2-weighted anatomical images as reference. In a region of interest (ROI) evaluation, ADC values were measured in prostate tissue and malignant lesions. Comparison of qualitative and quantitative parameters was performed using Wilcoxon test with subsequent Bonferroni correction. RESULTS: Subjective image quality was rated significantly higher in zoomed DWI compared to conventional DWI (2.1±0.9 vs. 2.7±0.9; p=0.0375). Visual distortion and artefacts were reduced in zoomed DWI without reaching statistical significance (1.8±0.7 vs. 2.4±1.0 and 2.1±1.0 vs. 2.5±1.0). Sensitivity and specificity of zoomed and conventional DWI were not significantly different. Zoomed DWI had a slightly higher AUC compared to conventional DWI without significant difference (0.82 versus 0.78; p=0.0576). Lesion conspicuity did not significantly differ between zoomed DWI and conventional DWI (1.8±0.8 vs. 1.9±1.0; p=0.8523). The alignment accuracy of zoomed DWI was significantly higher regarding both the prostate gland and lesions (deviation of outer contours of lesions in sagittal plane: 3±4mm vs. 5±3mm; p=0.0008). ADC tended to be higher in zoomed DWI without statistical significance (ADCmean in peripheral zone: 1.7±0.2×10(-3)mm(2)/s vs. 1.5±0.4×10(-3)mm(2)/s; ADCmean in lesion: 1.0±0.71×10(-3)mm(2)/s vs. 0.8±0.2×10(-3)mm(2)/s). CONCLUSIONS: Zoomed technique offers improved image quality for diffusion-weighted imaging of the prostate with reduced image distortion both for the whole gland as well as for cancer lesions and at least comparable diagnostic performance. The zoomed technique could be useful for multiparametric tissue characterization but also for biopsy and radiation therapy planning.

Pulmonary lesion assessment: comparison of whole-body hybrid MR/PET and PET/CT imaging--pilot study.

PURPOSE: To compare the performance of magnetic resonance (MR)/positron emission tomography (PET) imaging in the staging of lung cancer with that of PET/computed tomography (CT) as the reference standard and to compare the quantification accuracy of a new whole-body MR/PET system with corresponding PET/CT data sets. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained. Ten patients in whom bronchial carcinoma was proven or clinically suspected underwent clinically indicated fluorine 18 fluorodeoxyglucose (FDG) PET/CT and, immediately thereafter, whole-body MR/PET imaging with a new hybrid whole-body system (3.0-T MR imager with integrated PET system). Attenuation correction of MR/PET images was segmentation based with fat-water separation. Tumor-to-liver ratios were calculated and compared between PET/CT and MR/PET imaging. Tumor staging on the basis of the PET/CT and MR/PET studies was performed by two readers. Spearman rank correlation was used for comparison of data. RESULTS: MR/PET imaging provided diagnostic image quality in all patients, with good tumor delineation. Most lesions (nine of 10) showed pronounced FDG uptake. One lesion was morphologically suspicious for malignancy at CT and MR imaging but showed no FDG uptake. MR/PET imaging had higher mean tumor-to-liver ratios than did PET/CT (4.4 ± 2.0 [standard deviation] for PET/CT vs 8.0 ± 3.9 for MR/PET imaging). Significant correlation regarding the tumor-to-liver ratio was found between both imaging units (ρ = 0.93; P < .001). Identical TNM scores based on MR/PET and PET/CT data were found in seven of 10 patients. Differences in T and/or N staging occurred mainly owing to modality-inherent differences in lesion size measurement. CONCLUSION: MR/PET imaging of the lung is feasible and provides diagnostic image quality in the assessment of pulmonary masses. Similar lesion characterization and tumor stage were found in comparing PET/CT and MR/PET images in most patients.

Non-invasive pulmonary perfusion assessment in young patients with cystic fibrosis using an arterial spin labeling MR technique at 1.5 T.

OBJECT: To assess lung perfusion in young patients with cystic fibrosis (CF) using an arterial spin labeling (ASL) technique. MATERIALS AND METHODS: Perfusion imaging was performed in 5 healthy volunteers and 33 pediatric patients (13 ± 5 years) with CF using an ASL technique. Image quality was evaluated on a five-point scale (1 = excellent). Quantitative perfusion maps were calculated based on the modified Bloch equations. Perfusion differences between volunteers and CF patients and regional differences between lobes were analyzed using Student's t test. The association of perfusion values and forced expiratory volume in 1 s (FEV1) was analyzed using univariate regression analysis. RESULTS: Mean lung perfusion was 698 ± 67 ml/100g/min (range: 593-777 ml/100g/min) in volunteers and 526 ± 113 ml/100g/min (range: 346-724 ml/100g/min) in CF patients. Median image quality was 2 in volunteers and 3 in CF patients. In CF patients, significantly lower perfusion was observed in the upper lobes compared to healthy volunteers. Mean perfusion values significantly correlated with FEV1 (r = 0.84, P < 0.0001). CONCLUSION: ASL perfusion imaging provides lung perfusion assessment in young CF patients. This non-invasive functional imaging technique is worth being evaluated in the clinical monitoring of CF patients.

Assessment of synovitis in erosive osteoarthritis of the hand using DCE-MRI and comparison with that in its major mimic, the psoriatic arthritis.

RATIONALE AND OBJECTIVES: To investigate the diagnostic value of high-resolution dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) for assessment of synovitis in erosive osteoarthritis (EOA) of the hand and compare the results with those acquired in its potential mimic, the psoriatic arthritis (PsA). MATERIALS AND METHODS: Twenty-six patients (17 PsA, 9 EOA) were examined at 3 T. The time course of synovial contrast uptake was measured by ROI analysis using a three-dimensional encoded spoiled gradient-echo sequence. Characteristic parameters of synovial uptake curves (time to peak [TTP], peak value, mean transit time [MTT], area under the curve [AUC], and maximum upslope) of PsA and EOA patients were compared using gamma variate analysis and calculation of the late relative enhancement 15 minutes after contrast administration. RESULTS: Enhancement curves of PsA and EOA patients paralleled each other at comparable levels in the early phase after contrast injection without statistical difference in the following calculated characteristic curve parameters: TTP, peak value, MTT, AUC, and maximum upslope. However, significant difference was found in the late relative enhancement 15 minutes after contrast injection (P = .0275) with higher values in EOA patients. CONCLUSION: DCE-MRI provides assessment of synovitis in both patients with EOA and PsA. Interestingly, synovial enhancement characteristics were comparable for the most part in these two disorders. However, late enhancement might help in differentiation which is essential for guiding therapy.

Evaluation of response in malignant tumors treated with the multitargeted tyrosine kinase inhibitor sorafenib: a multitechnique imaging assessment.

OBJECTIVE: The purpose of this article is to illustrate the characteristic changes induced in different tumor types by the multitargeted tyrosine kinase inhibitor sorafenib. CONCLUSION: Sorafenib reduces tumor perfusion and thereby induces necrosis and often hemorrhage. Malignant tumors treated with sorafenib undergo both morphologic and functional changes; however, the morphologic changes are less frequent and inadequate for early evaluation of response. Therefore, imaging tools accurately assessing hemorrhage and decrease in tumor perfusion with subsequent necrosis should be the mainstay in monitoring targeted therapy agents.

Non-invasive assessment and quantification of liver steatosis by ultrasound, computed tomography and magnetic resonance.

Hepatic steatosis is the most prevalent liver disorder in the developed world. It is closely associated with features of metabolic syndrome, especially insulin resistance and obesity. The two most common conditions associated with fatty liver are alcoholic liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD). Liver biopsy is considered the gold standard for the assessment of liver fat, but there is a need for less invasive diagnostic techniques. New imaging modalities are emerging, which could provide more detailed information about hepatic tissue or even replace biopsy. In the present review, available imaging modalities (ultrasound, computed tomography, magnetic resonance imaging and proton magnetic resonance spectroscopy) are presented which are employed to detect or even quantify the fat content of the liver. The advantages and disadvantages of the above-mentioned imaging modalities are discussed. Although none of these techniques is able to differentiate between microvesicular and macrovesicular steatosis and to reveal all features visible using histology, the proposed diagnostic modalities offer a wide range of additional information such as anatomical and morphological information non-invasively. In particular, magnetic resonance imaging and proton magnetic resonance spectroscopy are able to quantify the hepatic fat content hence avoiding exposure to radiation. Except for proton magnetic resonance spectroscopy, all modalities offer additional information about regional fat distribution within the liver. MR elastography, which can estimate the amount of fibrosis, also appears promising in the differentiation between simple steatosis and steatohepatitis.

Diagnostic performance of contrast-enhanced computed tomography in the immediate assessment of radiofrequency ablation success in colorectal liver metastases.

BACKGROUND: To determine the accuracy of contrast-enhanced multislice computed tomography (CT) in the assessment of treatment success immediately after CT-guided radiofrequency (RF) ablation. METHODS: 26 patients with 38 Colorectal liver metastasis (CRM) were treated by CT-guided RF ablation. Pre-contrast and portal phase CT features before and immediately after ablation were retrospectively evaluated quantitatively and qualitatively: Influence of attenuation characteristics, safety margin, congruency between tumor and coagulation, and morphological criteria (shape, margin distinction, margin configuration, and margin continuity) were investigated. Findings were statistically analyzed with regard to local tumor progression. RESULTS: Mean observation period for follow-up scans was 6.4 months (range: 3-40 months). Attenuation characteristics, safety margin, and congruency had no significant effect on the probability of local tumor progression. Coagulations whose margin was categorized as "discontinuous" were significantly more often associated with local recurrence (p = 0.038). No significant influence on local recurrence could be detected regarding coagulation shape, margin distinction, and configuration. CONCLUSION: Computed tomography imaging immediately after RF ablation allows for morphological characterization of the coagulation and provides a valid baseline status for follow-up imaging. However, in CRM, morphological image criteria and attenuation characteristics have limited predictive value for immediate detection of persistent tumor.