Evaluation of the PET component of simultaneous [(18)F]choline PET/MRI in prostate cancer: comparison with [(18)F]choline PET/CT

PURPOSE

The aim of this study was to evaluate the positron emission tomography (PET) component of [(18)F]choline PET/MRI and compare it with the PET component of [(18)F]choline PET/CT in patients with histologically proven prostate cancer and suspected recurrent prostate cancer.

METHODS

Thirty-six patients were examined with simultaneous [(18)F]choline PET/MRI following combined [(18)F]choline PET/CT. Fifty-eight PET-positive lesions in PET/CT and PET/MRI were evaluated by measuring the maximum and mean standardized uptake values (SUVmax and SUVmean) using volume of interest (VOI) analysis. A scoring system was applied to determine the quality of the PET images of both PET/CT and PET/MRI. Agreement between PET/CT and PET/MRI regarding SUVmax and SUVmean was tested using Pearson's product-moment correlation and Bland-Altman analysis.

RESULTS

All PET-positive lesions that were visible on PET/CT were also detectable on PET/MRI. The quality of the PET images was comparable in both groups. Median SUVmax and SUVmean of all lesions were significantly lower in PET/MRI than in PET/CT (5.2 vs 6.1, p<0.05 and 2.0 vs 2.6, p<0.001, respectively). Pearson's product-moment correlation indicated highly significant correlations between SUVmax of PET/CT and PET/MRI (R=0.86, p<0.001) as well as between SUVmean of PET/CT and PET/MRI (R=0.81, p<0.001). Bland-Altman analysis revealed lower and upper limits of agreement of -2.77 to 3.64 between SUVmax of PET/CT vs PET/MRI and -1.12 to +2.23 between SUVmean of PET/CT vs PET/MRI.

CONCLUSION

PET image quality of PET/MRI was comparable to that of PET/CT. A highly significant correlation between SUVmax and SUVmean was found. Both SUVmax and SUVmean were significantly lower in [(18)F]choline PET/MRI than in [(18)F]choline PET/CT. Differences of SUVmax and SUVmean might be caused by different techniques of attenuation correction. Furthermore, differences in biodistribution and biokinetics of [(18)F]choline between the subsequent examinations and in the respective organ systems have to be taken into account.

Cardiac MRI: T2-Mapping Versus T2-Weighted Dark-Blood TSE Imaging for Myocardial Edema Visualization in Acute Myocardial Infarction

PURPOSE

To assess the diagnostic accuracy of T2 mapping for the detection of myocardial edema in acute myocardial infarction (AMI), and to compare this diagnostic accuracy with that of the current standard for myocardial edema imaging, which is T2w dark-blood TSE imaging.

MATERIALS AND METHODS

29 patients with AMI were examined at 1.5 T. For the visualization of myocardial edema, T2 maps, calculated from three T2w SSFP images, and T2w dark-blood TSE images were acquired in standard short- and long-axis views. Cine SSFP images were acquired for the analysis of left ventricular (LV) function and late gadolinium enhancement images (LGE) for the visualization of myocardial necrosis. The T2 maps as well as the T2w dark-blood TSE images were evaluated twice independently from the cine SSFP and LGE images. The presence or absence of myocardial edema was rated visually for each LV segment. As the standard of reference, the infarct zone was defined based on the cine SSFP and the LGE images.

RESULTS

In this segment-based analysis, T2 mapping showed a sensitivity of 82 % and a specificity of 94 % for the detection of edema in the infarct zone. T2w dark-blood TSE imaging revealed a sensitivity of 50 % and a specificity of 98 %. T2 mapping showed a higher intra-rater agreement compared to T2w dark-blood TSE imaging (κ: 0.87 vs. 0.76).

CONCLUSIONS

T2 mapping allows for the visualization of myocardial edema in AMI with a high sensitivity and specificity, and features better diagnostic accuracy in terms of a higher sensitivity compared to T2w dark-blood TSE imaging. Citation Format: • Naßenstein K, Nensa F, Schlosser T et al. Cardiac MRI: T2-Mapping Versus T2-Weighted Dark-Blood TSE Imaging for Myocardial Edema Visualization in Acute Myocardial Infarction. Fortschr Röntgenstr 2014; 186: 166 - 172.

[Extensive left ventricular myocardial fat deposition detected by cardiac MRI]

Although it is well known from pathological studies that intramyocardial fat deposition frequently occurs after left ventricular myocardial infarction, a left ventricular fat deposition is rarely diagnosed in the clinical routine. We report the case of extensive fat deposition in the left ventricular myocardium which was detected by routine cardiac magnetic resonance imaging.

Depiction and characterization of liver lesions in whole body [¹⁸F]-FDG PET/MRI

OBJECTIVES

To assess the value of PET/MRI with [(18)F]-FDG using a whole body protocol for the depiction and characterization of liver lesions in comparison to PET/CT.

METHODS

70 patients (31 women, 39 men) with solid tumors underwent [(18)F]-FDG PET/CT and followed by an additional PET/MRI using an integrated scanner. Two readers rated the datasets (PET/CT; PET/MRI) regarding conspicuity of hepatic lesions (4-point ordinal scale) and diagnostic confidence (5-point ordinal scale). Median scores for lesion conspicuity and diagnostic confidence were compared using Wilcoxon's rank sum test. Prior examinations, histopathology and clinical follow-up (116 ± 54 days) served as standard of reference.

RESULTS

36 of 70 (51%) patients showed liver lesions. Using PET/CT and PET/MRI all patients with liver metastases could correctly be identified. A total of 97 lesions were found (malignant n=26; benign n=71). For lesion conspicuity significantly higher scores were obtained for PET/MRI in comparison to PET/CT (p<0.001). Significantly better performance for diagnostic confidence was observed in PET/MRI, both for malignant as for benign lesions (p<0.001).

CONCLUSIONS

PET/MRI, even in the setting of a whole body approach, provides higher lesion conspicuity and diagnostic confidence compared to PET/CT and may therefore evolve as an attractive alternative in oncologic imaging.

Correlation of the apparent diffusion coefficient (ADC) with the standardized uptake value (SUV) in hybrid 18F-FDG PET/MRI in non-small cell lung cancer (NSCLC) lesions: initial results

PURPOSE

To compare the apparent diffusion coefficient (ADC) in non-small cell lung cancer lesions with standardized uptake values (SUV) derived from combined 18F-fluoro-deoxy-glucose-positron emission tomography/magnetic resonance imaging (FDG-PET/MRI) and those derived from FDG-PET/CT.

MATERIALS AND METHODS

In 18 consecutive patients with histologically proven NSCLC (17 men, 1 woman; mean age, 61 ± 12 years), whole-body FDG-PET/MRI was performed after whole-body FDG-PET/CT. Regions of interest (ROI) encompassing the entire primary tumor were drawn into FDG-PET/CT and FDG-PET/MR images to determine the maximum and mean standardized uptake value (SUVmax; SUVmean) and into ADC parameter maps to assess mean ADC values. Pearson's correlation coefficients were calculated to compare SUV and ADC values.

RESULTS

The SUVmax of NSCLC was 12.3 ± 4.8 [mean ±SD], and the SUVmean was 7.2 ± 2.8 as assessed by FDG-PET/MRI. The SUVmax and SUVmean derived from FDG-PET/CT and FDG-PET/MRI correlated well (R = 0.93; p < 0.001 and R = 0.92; p < 0.001, respectively). The ADCmean of the pulmonary tumors was 187.9 ± 88.8 × 10-5 mm²/s [mean ± SD]. The ADCmean exhibited a significant inverse correlation with the SUVmax (R = -0.72; p < 0.001) as well as with the SUVmean assessed by FDG-PET/MRI (R = -0.71; p < 0.001).

CONCLUSION

This simultaneous PET/MRI study corroborates the assumed significant inverse correlation between increased metabolic activity on FDG-PET and restricted diffusion on DWI in NSCLC.Citation Format:

Association of aneurysms and variation of the A1 segment

BACKGROUND AND PURPOSE

Previous studies have described a correlation between variants of the circle of Willis and pathological findings, such as cerebrovascular diseases. Moreover, anatomic variations of the anterior cerebral artery (ACA) seem to correspond to the prevalence of aneurysms in the anterior communicating artery (ACoA). The aim of this study was to assess the prevalence of aneurysms in patients with anatomical/morphological variations of the circle of Willis.

METHODS

We retrospectively analyzed 223 patients who underwent cerebral angiography between January 2002 and December 2010 for aneurysm of the ACoA. Diagnostic imaging was reviewed and statistically evaluated to detect circle of Willis anomalies, aneurysm size, and rupture. 204 patients with an unrelated diagnosis served as the control group.

RESULTS

Variations of the A1 segment occurred significantly more frequently in the aneurysm group than in the control group. Mean aneurysm size in patients with grades I and III hypoplasia or aplasia was 6.58 mm whereas in patients with grade II hypoplasia it was 7.76 mm.

CONCLUSIONS

We found that variations in the A1 segment of the ACAs are correlated with a higher prevalence of ACoA aneurysms compared with patients with a symmetric circle of Willis.

Assessment of airway hyperresponsiveness: comparison of spirometry and body plethysmography

While methacholine (MCH) testing is commonly used in the clinical diagnosis of asthma, the detection of airway narrowing often relies on either spirometry or body plethysmography, however comparative studies are rare. In this study we performed MCH testing in 37 patients with variable shortness of breath at work and in 37 patients with no history of airway disease. The inclusion criteria were: no acute respiratory infection within 6 weeks, no severe diseases, normal baseline specific airway resistance (sR(aw)), normal baseline forced expiratory volume in 1 s (FEV(1)), Tiffeneau index >70%, no previous treatment with steroids within 14 days and no short acting bronchodilators within 24 h. Cumulative doses of 0.003, 0.014, 0.059, 0.239 and 0.959 mg MCH were inhaled by a dosimeter method. A FEV(1) decrease of ≥20% from baseline and a 100% increase of sR(aw) to ≥2.0 kPa/s was defined as end-of-test-criterion. Provocation doses were calculated by interpolation. Performance of lung function parameters was compared using receiver-operating-characteristic (ROC) analysis. ROC analysis resulted in an area under the ROC curve (AUC) of 0.74 for FEV(1) vs. 0.82 for sR(aw). The corresponding Youden Indices (J) were 0.46 for FEV(1) and 0.57 for sR(aw). The Youden Index of sR(aw) was higher and sensitivity and specificity (73%/84%) were rather well-balanced, in contrast to FEV(1) (54%/92%). In conclusion, in cumulative MCH challenges sR(aw) was found to be the overall most useful parameter for the detection of bronchial hyperresponsiveness. Body plethysmography yielded a balanced sensitivity-specificity ratio with higher sensitivity than spirometry, but comparable specificity.

Assessment of airway hyperreactivity: comparison of forced spirometry and body plethysmography for methacholine challenge tests

INTRODUCTION

Bronchial challenge tests by inhalation of aerosolized methacholine (MCH) are commonly used in the clinical diagnosis of airway hyperresponsiveness (AHR). While the detection of airway narrowing relies on the patient's cooperation performing forced spirometry, body plethysmographic measurements of airway resistance are less depending on the patient's cooperation and do not alter the respiratory tract by maximal maneuvers. Hence we compared both methods concerning their clinical value and correlation during MCH challenges in patients with asthma.

MATERIAL AND METHODS

Cumulative MCH challenges test, consisting of up to 5 steps, evaluated with body plethysmography on each step were performed in 155 patients with bronchial asthma. Airway responses were recorded at each step of MCH application (MasterScreen Body, Cardinal Health, Höchberg). At the baseline test and after crossing the provocation dose (PD) threshold in body plethysmography (PD+100 sReff), forced expirations were performed and FEV(1), FVC, and FEV(1) %FVC were measured. Using regression analysis of the airway parameters and taking the MCH dose as the covariate, we could extrapolate to missing spirometric values and interpolate the estimated MCH dose when crossing the PD threshold (PD-20 FEV(1)) between two consecutive measurements. The administered PD+100 MCH doses for specific airway resistance, sRtot, and sReff were compared with resistance parameters Rtot and Reff, and to PD-20 of FEV(1) and FEV(1) %FVC.

RESULTS

Regarding sReff we found a mild, moderate, or severe AHR in 114 patients (75%), but only 50 (32%) according to FEV1. A statistical analysis showed strongly linear correlated parameters of airway resistance, but no significant correlation between the results of body plethysmography and forced spirometry.

CONCLUSIONS

Using MCH challenges, we found specific airway resistance to be the most sensitive parameter to detect AHR. Raw is largely independent of height and gender facilitating the interpretation of measurements carried out longitudinally.