Mean Relative Enhancement Ratio Research Articles

Relative Enhancement Ratio of Portal Venous Phase to Unenhanced CT in the Diagnosis of Lipid-poor Adrenal Adenomas.

Background The development of an accurate, practical, noninvasive, and widely available diagnostic approach to characterize lipid-poor adrenal lesions (greater than 10 HU at unenhanced CT) remains an ongoing demand. Purpose To investigate whether combined assessment of unenhanced and portal venous phase CT allows for the differentiation of lipid-poor adrenal adenomas from nonadenomas. Materials and Methods Patients with lipid-poor adrenal lesions who underwent unenhanced and portal venous phase CT with a single-energy scanner between January 2016 and March 2020 were identified retrospectively. For each lesion, the unenhanced and contrast-enhanced attenuation were measured; the absolute enhancement (contrast-enhanced minus unenhanced attenuation [HU]) and relative enhancement ratio ([absolute enhancement divided by unenhanced attenuation] × 100%) were calculated. The sensitivity achieved at 95% specificity to distinguish adenomas from nonadenomas was determined with receiver operating characteristic curve analysis and compared among parameters with use of the McNemar test. Results A total of 220 patients (mean age ± standard deviation, 66 years ± 12; 134 men) with 131 lipid-poor adenomas and 89 nonadenomas were analyzed. The sensitivity (achieved at 95% specificity) of the relative enhancement ratio (86% [113 of 131 adenomas; 95% CI: 79, 92] at a threshold of >210%) was higher than that of unenhanced attenuation (50% [66 of 131 adenomas; 95% CI: 42, 59] at a threshold of ≤21 HU), contrast-enhanced attenuation (3% [four of 131 adenomas; 95% CI: 1, 8] at a threshold of >120 HU), and absolute enhancement (24% [32 of 131 adenomas; 95% CI: 17, 33] at a threshold of >74 HU; all P < .001). The sensitivities of the relative enhancement ratio were 100% (58 of 58 adenomas; 95% CI: 94, 100), 83% (52 of 63 adenomas; 95% CI: 71, 91), and 30% (three of 10 adenomas; 95% CI: 7, 65) for adenomas measuring unenhanced attenuation of more than 10 HU up to 20 HU, 21-30 HU, and more than 30 HU, respectively. Conclusion A relative enhancement ratio threshold of greater than 210%, measured at unenhanced and portal venous phase CT, accurately differentiated lipid-poor adenomas from nonadenomas, particularly for lesions with unenhanced attenuation of 10-30 HU. © RSNA, 2021 Online supplemental material is available for this article.

Oxygen-enhanced MRI for patients with connective tissue diseases: Comparison with thin-section CT of capability for pulmonary functional and disease severity assessment

PurposeTo prospectively and directly compare oxygen-enhanced (O2-enhanced) MRI with thin-section CT for pulmonary functional loss and disease severity assessment in connective tissue disease (CTD) patients with interstitial lung disease (ILD). Materials and methodsThin-section CT, O2-enhanced MRI, pulmonary function test and serum KL-6 were administered to 36 CTD patients with ILD (23 men, 13 women; mean age: 63.9 years) and nine CTD patients without ILD (six men, and three women; mean age: 62.0 years). A relative-enhancement ratio (RER) map was generated from O2-enhanced MRI and mean relative enhancement ratio (MRER) for each subject was calculated from all ROI measurements. CT-assessed disease severity was evaluated with a visual scoring system from each of the thin-section CT data. MRER and CT-assessed disease severities of CTD patients with and without ILD were then statistically compared. To assess capability for pulmonary functional loss and disease severity assessment in CTD patients, correlations of MRER and CT-assessed disease severity with pulmonary functional parameters and serum KL-6 in all subjects were statistically determined. ResultsMRER and CT-assessed disease severity showed significant differences between CTD patients with (MRER: 0.15±0.08, CT-assessed disease severity: 13.0±7.4%) and without ILD (MRER: 0.25±0.06, p=0.0011; CT-assessed disease severity: 1.6±1.6%, p<0.0001). MRER and CT-assessed disease severity correlated significantly with pulmonary functional parameters and serum KL-6 in all subjects (0.61≤r≤0.79, p<0.05). ConclusionO2-enhanced MRI was found to be as useful as thin-section CT for pulmonary functional loss and disease severity assessment of CTD patients with ILD.

Gadolinium enhanced MRI in patients with left ventricular apical ballooning syndrome implicates myocarditis as an etiology

Aims: Left ventricular apical ballooning syndrome (LVABS) is a clinical condition of unknown etiology, characterized by acute onset of atypical apical wall motion and absence of coronary artery disease. Gadolinium-enhanced cardiac magnetic resonance imaging (Gd-MRI) may be used to identify patients with myocarditis. Using cardiac MRI, we evaluated whether acute myocarditis may be an etiology that underlies LVABS. Methods and Results: Consecutive patients who presented with LVABS during a three-year period were included. Demographic data was recorded and echocardiography, coronary angiography, and hemodynamic assessment performed. Gd-MRI was performed in all patients. The study was deemed consistent with myocarditis when global myocardial to skeletal muscle enhancement ratio was ≥3.5. Regional Gd-MRI analysis was also performed. Patients (n = 11) were female (100%) and of mean age 72 years (72 ± 11). Preceding febrile illness occurred in 4 (36.3%) and leukocytosis in 6 (54.4%) patients. Initial mean left ventricular ejection fraction (41% ± 12%) improved (70.2% ± 8%) upon follow-up (39 ± 43 days). Global MRI analysis was positive in 5/11 (45.5%) (mean relative enhancement ratio 4.8 ± 1.4). Regional MRI analysis was positive in 4/6 further patients (overall: 9/11 (82%)). Conclusions: Gadolinium enhanced MRI imaging in LVABS implicates myocarditis as a possible etiology. Regional MRI analysis adds sensitivity to global cardiac MRI evaluation.

Oxygen-Enhanced MRI, Thin-Section MDCT, and Perfusion SPECT/CT: Comparison of Clinical Implications to Patient Care for Lung Volume Reduction Surgery

The purpose of our study was to prospectively and directly compare capability of O2-enhanced MRI, MDCT, and perfusion SPECT/CT to clinical outcome measurements in candidates for lung volume reduction surgery (LVRS). Twenty-five consecutive candidates for LVRS (20 men and five women; age range, 45-76 years) underwent MDCT, O2-enhanced MRI, and perfusion SPECT/CT before and after LVRS. Clinical outcomes for each candidate were evaluated in terms of differences between pre- and postoperative percentage forced expiratory volume in 1 second (%FEV1), Pao2, and 6-minute walking distance. Quantitatively assessed upper/lower lung ratios on O2-enhanced MRI, MDCT, and SPECT/CT were calculated from regional relative enhancement ratios, functional lung volumes, and radioisotope uptakes between upper and lower lungs. Qualitatively assessed upper/lower lung ratios on O2-enhanced MRI, MDCT, and SPECT/CT were estimated using visual scoring systems. To evaluate the correlation for individual upper/lower lung ratios and clinical outcomes, all upper/lower lung ratios were correlated with clinical outcomes. Improvements in mean relative enhancement ratio were directly correlated with clinical outcomes to assess the capability of O2-enhanced MRI to assess therapeutic effect. All quantitatively (-0.63≤r≤-0.47, p<0.05) and qualitatively (0.41≤r≤0.57, p<0.05) assessed upper/lower lung ratios showed moderate and statistically significant correlation with clinical outcomes, and improvement in mean relative enhancement ratio showed moderate or good correlation, both statistically significant (-0.44≤r≤0.71, p<0.05). O2-enhanced MRI shows potential for more accurate evaluation of postoperative clinical outcome for LVRS candidates than SPECT/CT and can be considered at least as reliable as MDCT.

Comparison of capability of dynamic O2-enhanced MRI and quantitative thin-section MDCT to assess COPD in smokers

The purpose of this study was to directly and prospectively compare the capability of dynamic O(2)-enhanced MRI and quantitatively assessed thin-section MDCT to assess smokers' COPD in a large prospective cohort. The GOLD criteria for smokers were used to classify 187 smokers into four clinical stage groups as follows: smokers without COPD (n=56) and with mild (n=54), moderate (n=52) and severe or very severe COPD (n=24). All smokers underwent dynamic O(2)-enhanced MRI, MDCT and pulmonary function tests. Mean relative enhancement ratio and mean wash-in time on MRI and CT-based functional lung volume (CT-based FLV) as well as the ratio of airway wall area to total airway area on MDCT were computationally calculated. Then, all indexes were significantly correlated with functional parameters. To determine the efficacy of all indexes for clinical stage classification, the indexes for the four clinical groups were statistically compared by using Tukey's honestly significant difference multiple comparison test. All indexes had significant correlations with functional parameters (p<0.0001). All indexes except CT-based FLV in all groups had significant differences each other (p<0.05). Dynamic O(2)-enhanced MRI for assessment of COPD in smokers is potentially as efficacious as quantitatively assessed thin-section MDCT.

Oxygen-enhanced Magnetic Resonance Imaging versus Computed Tomography

Oxygen-enhanced magnetic resonance imaging (MRI) has been proposed as a useful tool for assessing regional morphological and functional changes in chronic obstructive pulmonary disease (COPD). To prospectively and directly compare the efficacy of O(2)-enhanced MRI and quantitative computed tomography (CT) for smoking-related pulmonary functional loss assessment and clinical stage classification of smoking-related COPD. One hundred sixty smokers were classified into four age- and gender-matched groups by using the GOLD criteria for smokers: Smokers without COPD (n = 40), Mild COPD (n = 40), Moderate COPD (n = 40), and Severe or Very Severe COPD (n = 40). All smokers underwent O(2)-enhanced MRI, multidetector-row CT, and pulmonary function test. Mean relative enhancement ratio on O(2)-enhanced MRI and CT-based functional lung volume (FLV) on quantitative CT were calculated. To compare the efficacy of O(2)-enhanced MRI and quantitative CT for pulmonary functional loss assessment, both indexes were correlated with pulmonary functional parameters. To determine the efficacy of two methods for clinical stage classification, the four clinical groups' mean relative enhancement ratio and CT-based FLV were statistically compared. Correlations of both indexes with pulmonary functional parameters were significant (P < 0.0001). Pulmonary functional parameters and mean relative enhancement ratio for the four clinical groups showed significant differences (P < 0.05). CT-based FLVs of smokers without COPD and mild COPD were significantly different from those for moderate COPD and severe or very severe COPD (P < 0.05). O(2)-enhanced MRI is effective for pulmonary functional loss assessment and clinical stage classification of smoking-related COPD and quantitative CT.

Dynamic Oxygen-Enhanced MRI Versus Quantitative CT: Pulmonary Functional Loss Assessment and Clinical Stage Classification of Smoking-Related COPD

The purpose of the present study is to prospectively compare the capability of dynamic oxygen-enhanced MRI and quantitative CT for pulmonary functional loss assessment and clinical stage classification of smoking-related chronic obstructive pulmonary disease (COPD). Ten nonsmoking and 61 consecutive smoking-related COPD subjects underwent dynamic oxygen-enhanced MRI, CT, and pulmonary function tests. COPD subjects were classified into four clinical stages on the basis of the ATS-ERS guidelines. Wash-in time and relative enhancement ratio maps were generated by pixel-by-pixel analyses. Mean wash-in time and relative enhancement ratio were determined as averages of region of interest (ROI) measurements. CT-based functional lung volumes were measured on quantitative CT using the density-masked CT technique. For comparison of assessment capability for smoking-related functional loss, the three parameters were correlated with the percentage predicted forced expiratory volume in 1 second (%FEV1) and the percentage predicted diffusing capacity of the lung for carbon monoxide corrected for alveolar volume (%DL(CO)/VA). To determine the clinical stage classification capability, these parameters were statistically compared for nonsmoking subjects and all clinical stages of smoking-related COPD subjects. Correlation between mean wash-in time and %FEV1 (r = -0.74, p < 0.0001) and between mean relative enhancement ratio and %DL(CO)/VA (r = 0.66, p < 0.0001) was better than that between CT-based functional lung volume and either %FEV1 (r = 0.61, p < 0.0001) or %DL(CO)/VA (r = 0.56, p < 0.0001). Mean wash-in time showed a significant difference between nonsmoking and smoking-related COPD subjects at all clinical stages (p < 0.05). Dynamic oxygen-enhanced MRI has potential for pulmonary functional loss assessment and clinical stage classification of smoking-related COPD as does quantitative CT.

Solitary pulmonary nodules: potential role of dynamic MR imaging in management initial experience.

To evaluate the utility of dynamic magnetic resonance (MR) imaging in the management of solitary pulmonary nodules (SPNs). Fifty-eight patients with 58 pathologic analysis-proved SPNs (diameter < 30 mm) underwent dynamic 1.5-T MR imaging. The 58 SPNs were classified into three groups at pathologic analysis: malignant SPNs (n = 38), active infections (n = 10), or benign SPNs (n = 10). From signal intensity-time curves generated after the bolus injection of contrast material, the maximum relative enhancement ratio and slope of enhancement were calculated and statistically compared among the three groups. Threshold values of these two dynamic MR indexes were determined on the basis of positive differentiations. The mean relative enhancement ratio and mean slope of enhancement for the malignant SPN group were significantly higher than those for the benign SPN group and significantly lower than those for the active infection group (P <.05). With 0.15 as the threshold maximum relative enhancement ratio for distinguishing the malignant SPN and active infection groups from the benign SPN group, the sensitivity, specificity, and accuracy were 100%, 70%, and 95%, respectively. With 0.025/sec as the threshold slope of enhancement, all SPNs with malignancy and active infection were clearly distinguished from benign SPNs. Dynamic MR indexes were useful in the differentiation between SPNs that necessitated further evaluation or treatment (malignancy and active infection) and SPNs that did not necessitate further evaluation or treatment (benign nodules).

Dynamic oxygen-enhanced MRI reflects diffusing capacity of the lung.

The purpose of this study was to demonstrate the feasibility of dynamic oxygen-enhanced MRI in a clinical setting. We hypothesized that dynamic oxygen enhancement can reflect the regional diffusing capacity of the lung. Ten patients with pulmonary emphysema and seven healthy volunteers were examined with a respiratory-synchronized inversion recovery single-shot turbo spin-echo sequence (TR = 3200-5000 ms, TE = 16 ms, TI = 720 ms, ETS = 4 ms) following 100% oxygen inhalation, using a 1.5 T whole-body scanner. Maximum mean relative enhancement ratios calculated by averaging six defined regions of interest (ROIs) in both lungs were statistically compared between healthy volunteers and patients, and were correlated with diffusing lung capacity (%DL(CO)). In patients with pulmonary emphysema, maximum mean relative enhancement ratios were significantly decreased compared to those in healthy volunteers (P = 0.0008). Maximum mean relative enhancement ratio had excellent correlation with % DL(C0) (r(2) = 0.83). Dynamic oxygen-enhanced MRI may reflect the diffusing capacity of the lung; therefore, imaging of oxygen enhancement with MRI may provide maps of the diffusing capacity.

Oxygen-enhanced MR ventilation imaging of the lung: preliminary clinical experience in 25 subjects.

The purpose of this study was to show the feasibility of oxygen-enhanced MR ventilation imaging in a clinical setting with correlation to standard pulmonary function tests, high-resolution CT, and (81m)Kr ventilation scintigraphy. Seven healthy volunteers, 10 lung cancer patients, and eight lung cancer patients with pulmonary emphysema were studied. A respiratory synchronized inversion-recovery single-shot turbo-spin-echo sequence (TE, 16; inversion time, 720 msec; interecho spacing, 4 msec) was used for data acquisition. The following paradigm of oxygen inhalation was used: 21% oxygen (room air), 100% oxygen, 21% oxygen. MR imaging data including maximum mean relative enhancement ratio and mean slope of relative enhancement were correlated with forced expiratory volume in 1 sec, diffusing lung capacity, high-resolution CT emphysema score, and mean distribution ratio of (81m)Kr ventilation scintigraphy. Oxygen-enhanced MR ventilation images were obtained in all subjects. Maximum mean relative enhancement ratio and mean slope of relative enhancement of lung cancer patients were significantly decreased compared with those of the healthy volunteers (p < 0.0001, p < 0.0001). The mean slope of relative enhancement in lung cancer patients with pulmonary emphysema was significantly lower than that of lung cancer patients without pulmonary emphysema (p < 0.0001). Maximum mean relative enhancement ratio (r(2) = 0.81) was excellently correlated with diffusing lung capacity. Mean slope of relative enhancement (r(2) = 0.74) was strongly correlated with forced expiratory volume in 1 sec. Maximum mean relative enhancement had good correlation with the high-resolution CT emphysema score (r(2) = 0.38). The maximum mean relative enhancement had a strong correlation with the distribution ratio (r(2) = 0.77). Oxygen-enhanced MR ventilation imaging in human subjects showed regional changes in ventilation, thus reflecting regional lung function.