Accuracy of combined PET/CT in image-guided interventions of liver lesions: An ex-vivo study

AIM： Positioning of interventional devices in liver lesions is a challenging task if only CT is available. We investigated the potential benefit of combined PET/CT images for localization of interventional devices in interventional liver studies. METHODS： Thirty lesions each of hyperdense, isodense and hypodense attenuation compared to normal liver parenchyma were injected into 15 ex-vivo pig livers. All lesions were composed of the same amounts of gelatine containing 0.5 MBq of ^18F-FDG. Following lesion insertion, an interventional needle was placed in each lesion under CT-guidance solely. After that, a PET/CT study was performed. The localization of the needle within the lesion was assessed for CT alone and PET/CT and the root mean square （RMS） was calculated. Results were compared with macroscopic measurements after lesion dissection serving as the standard of reference. RESULTS： In hypo- and isodense lesions PET/CT proved more accurate in defining the position of the interventional device when compared with CT alone. The mean RMS for CT and PET/CT differed significantly in isodense and hypodense lesions. No significant difference was found for hyperdense lesions. CONCLUSION： Combined FDG-PET/CT imaging provides more accurate information than CT alone concerning the needle position in FDG-PET positive liver lesions. Therefore combined PET/CT might be potentially beneficial not only for localization of an interventional device, but may also be beneficial for guidance in interventional liver procedures.

Integrated Assessment of Cardiac PET/MRI: Co-Registered PET and MRI Polar Plots by Mutual MR-Based Segmentation of the Left Ventricular Myocardium

Background: In the present study, we sought to describe a procedure for the creation of co-registered positron emission tomography (PET) and magnetic resonance imaging (MRI) polar plots of cardiac PET/MRI examinations, validate the resulting plots against available standard methods in patients with myocardial infarction and provide examples that demonstrate the advantage of the novel approach over existing standards. Methods: Co-registered LGE and PET short-axis images were transformed into polar maps based on a radial sampling pattern. LGE was automatically detected using an automated thresholding algorithm (ATA). In 20 PET/MRI examinations in patients with acute myocardial infarction, agreement between manual LGE assessment and the ATA classification was calculated. Also agreement between MRI-segmentation based PET polar plots and standard PET polar plots (created with the Corridor4DM software package) was assessed. Results: No statistically significant difference in infarct sizes between manual and ATA segmentation was found (p = 0.12). Both methods were highly correlated (Pearson’s r = 0.96, p Conclusion: A straightforward software approach for the creation of co-registered PET and MRI polar plots was described and successfully demonstrated in PET/MRI studies of myocardial infarction and inflammation.

Definition of retrosternal thyroid growth

The diagnosis of a retrosternal thyroid growth (RTG) causes extended surgical exploration and a different surgical treatment planning (partial sternotomy, thoracotomy) and is usually made by the help of thyroid scintigraphy and ultrasonography. But both examinations have problems in determining the retrosternal thyroid extend in the complex anatomy of sternal bone and often pathologically altered manubrioclavicular joints (MCJ). This study evaluates the variation of anatomical structures in the upper sternal region, the position of the sternal markers during scintigraphy, and the frequency of enhanced bone metabolism of the MCJs. For this aim, the positions of the upper edges of the MCJs were measured by X-ray fluoroscopy in 50 consecutive patients. To prove the exactness of an external marker as used in thyroid scintigraphy, the variation of the marker position was also determined. The activity in the MCJs was measured semiquantitatively with bone scintigraphy in further 100 patients (mean age: 62.3 yrs, SD: 14.2 yrs). As results, the upper edges of the medial clavicular edges exceed the upper margin of the sternal edge up to 2.7 cm. The distance between the medial clavicular edges ranged from 2.3 - 5.6 cm. The position of the sternal marker was correct in the horizontal deviation (mean: 0.1 cm, SD: 0.48 cm) but too high in the vertical position (mean: 2.2 cm, SD: 0.67 cm). During bone scintigraphy, the MCJs showed no enhanced activitity in 75/200 joints, medium activity in 96/200 joints, and strong enhanced activity in 29/200 joints. In consequence, a high variability in the position of the anatomical structures has to be considered together with a high amount of degenerative alterations. The position of the sternal marker was inappropriate in the vertical direction and overestimated a possible retrosternal growth.