Patient without liver metastases.

<p>PET/CT with a false positive result showing a hypodense pseudolesion with a diameter 9 mm in the CT dataset without correlate in PET. In the later acquired PET/MRI (C-E) no correlate in PET nor in the morphological datasets (D: T1w VIBE portal-venous phase; E: T2w TSE fs).</p

Receiver operating characteristic (ROC) curve for PET/CT and PET/MRI for reader 1 (left), reader 2 (middle) and both readers (right).

<p>Significantly higher accuracy (area under the curve, AUC) for PET/MRI (p<0.01 for reader 1 and 2; p<0.001 overall).</p

Patient with uveal melanoma.

<p>cePET/CT (A+B) shows a hypodense liver lesion of 10 mm in diameter without elevated tracer uptake which is therefore rated as indeterminate. In PET/MRI (C-F) the lesion is hyperintense in T2w TSE (D) and shows signs of restricted diffusion (E: b1000; F: ADC map). Therefore, based on PET/MRI the lesion is rated as metastasis. Based on T2w imaging additional 4 metastases are visualized in PET/MRI in the contralateral lobe.</p

Liver metastases not visible in PET/CT: detection rate in different MR-sequences.

<p>Liver metastases not visible in PET/CT: detection rate in different MR-sequences.</p

Further characterization of benign liver lesions.

<p>Further characterization of benign liver lesions.</p

Sensitivity, Specificity, Accuracy (area under the curve, AUC), PPV, NPV with 95% CI for each reader as well as in combination.

<p>Significant differences between PET/CT and PET/MRI are indicated (*: p<0.05; **: p<0.01, ***:p<0.001).</p

Patient with breast cancer.

<p>Both PET/CT (A,B) as well as PET/MRI (C; D; VIBE, portal venous phase) show a lesion with elevated FDG-uptake and ill-defined lesion borders as well as central contrast enhancement as signs of malignancy. Based on these findings the lesion was correctly identified as metastasis in both modalities.</p

Figure 5 shows an anatomic variability of the upper abdomen in one healthy subject with a tall, centrally arranged liver and partially inverted situs, by means of mirrored location of spleen and stomach in the right upper abdomen.

<p>In this subject residual B₁-artifacts strongly impaired the conspicuity of central liver vessels in 2D and 3D FLASH imaging (stars in Figure A). Yet, being the sequence to be least impaired, TOF imaging allowed for a high-quality assessment of portal vein (arrow) and the left hepatic artery (dashed arrow). Figure B shows high quality delineation of the splenic artery and several small branches at the splenic hilus in all three sequences (arrows).</p

Accuracy of [¹⁸F]FDG PET/MRI for the Detection of Liver Metastases

<div><p>Background</p><p>The aim of this study was to compare the diagnostic accuracy of [¹⁸F]FDG-PET/MRI with PET/CT for the detection of liver metastases.</p><p>Methods</p><p>32 patients with solid malignancies underwent [¹⁸F]FDG-PET/CT and subsequent PET/MRI of the liver. Two readers assessed both datasets regarding lesion characterization (benign, indeterminate, malignant), conspicuity and diagnostic confidence. An imaging follow-up (mean interval: 185±92 days) and/-or histopathological specimen served as standards of reference. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for both modalities. Accuracy was determined by calculating the area under the receiver operating characteristic (ROC) curve. Values of conspicuity and diagnostic confidence were compared using Wilcoxon-signed-rank test.</p><p>Results</p><p>The standard of reference revealed 113 liver lesions in 26 patients (malignant: n = 45; benign: n = 68). For PET/MRI a higher accuracy (PET/CT: 82.4%; PET/MRI: 96.1%; p<0.001) as well as sensitivity (67.8% vs. 92.2%, p<0.01) and NPV (82.0% vs. 95.1%, p<0.05) were observed. PET/MRI offered higher lesion conspicuity (PET/CT: 2.0±1.1 [median: 2; range 0–3]; PET/MRI: 2.8±0.5 [median: 3; range 0–3]; p<0.001) and diagnostic confidence (PET/CT: 2.0±0.8 [median: 2; range: 1–3]; PET/MRI 2.6±0.6 [median: 3; range: 1–3]; p<0.001). Furthermore, PET/MRI enabled the detection of additional PET-negative metastases (reader 1: 10; reader 2: 12).</p><p>Conclusions</p><p>PET/MRI offers higher diagnostic accuracy compared to PET/CT for the detection of liver metastases.</p></div

Qualitative analysis of image quality and presence of artifacts (5-point scales) for all analyzed liver vessel segments in all three sequences.

<p>(PHA  =  proper hepatic artery, RHA = 2^nd order branch of right hepatic artery, PV  =  main portal vein, RPV = 1^st order branch of right portal vein, IVC  =  inferior vena cava, MHV  =  middle hepatic vein).</p