Intraindividual comparison of image quality using retrospective and prospective respiratory gating for the acquisition of thin sliced four dimensional multidetector CT of the thorax in a porcine model

Clinical implementations of 4D pencil beam scanned particle therapy: Report on the 4D treatment planning workshop 2016 and 2017

In 2016 and 2017, the 8th and 9th 4D treatment planning workshop took place in Groningen (the Netherlands) and Vienna (Austria), respectively. This annual workshop brings together international experts to discuss research, advances in clinical implementation as well as problems and challenges in 4D treatment planning, mainly in spot scanned proton therapy. In the last two years several aspects like treatment planning, beam delivery, Monte Carlo simulations, motion modeling and monitoring, QA phantoms as well as 4D imaging were thoroughly discussed. This report provides an overview of discussed topics, recent findings and literature review from the last two years. Its main focus is to highlight translation of 4D research into clinical practice and to discuss remaining challenges and pitfalls that still need to be addressed and to be overcome.

Combined Electrocardiography- and Respiratory-Triggered CT of the Lung to Reduce Respiratory Misregistration Artifacts between Imaging Slabs in Free-Breathing Children: Initial Experience

Objective

Cardiac and respiratory motion artifacts degrade the image quality of lung CT in free-breathing children. The aim of this study was to evaluate the effect of combined electrocardiography (ECG) and respiratory triggering on respiratory misregistration artifacts on lung CT in free-breathing children.

Materials and Methods

In total, 15 children (median age 19 months, range 6 months–8 years; 7 boys), who underwent free-breathing ECG-triggered lung CT with and without respiratory-triggering were included. A pressure-sensing belt of a respiratory gating system was used to obtain the respiratory signal. The degree of respiratory misregistration artifacts between imaging slabs was graded on a 4-point scale (1, excellent image quality) on coronal and sagittal images and compared between ECG-triggered lung CT studies with and without respiratory triggering. A p value < 0.05 was considered significant.

Results

Lung CT with combined ECG and respiratory triggering showed significantly less respiratory misregistration artifacts than lung CT with ECG triggering only (1.1 ± 0.4 vs. 2.2 ± 1.0, p = 0.003).

Conclusion

Additional respiratory-triggering reduces respiratory misregistration artifacts on ECG-triggered lung CT in free-breathing children.

Early time-related course of image findings in postmortem MRI: Typical findings and observer agreement in a porcine model

PURPOSE

To assess early time-related image findings in postmortem magnetic resonance imaging (MRI) and to evaluate observer agreement in a porcine model.

MATERIAL AND METHODS

Three pigs were examined by MRI at 15 different time points in the first 36h after death. Two observers independently recorded the postmortem interval (PMI) to the appearance of fluid collection (pleural space, interlobar and interlobular pulmonary fissures and hepatic interlobar fissures), gas accumulation (intrahepatic and intracardial) and blood clotting (aorta and intrahepatic venous vessels). Cohen's Kappa statistics and intraclass correlation coefficient (ICC) were used to evaluate intra- and interobserver agreement.

RESULTS

Intrahepatic gas was evident after 12, 17 and 30h. Also, intracardiac gas was present in all animals. However, no chronological appearance has been observed. Blood clotting in the hepatic vein was observed within 3min, aortic clotting with a delay of 2-12h after death. Interlobular pulmonary fluid (median PMI: 2h, range 2-2h), pleural effusion (median PMI: 10.5h, range 9-12h) and hepatic interlobar fissure fluid (median PMI: 11.5h, range 11-12h) displayed a chronological appearance pattern. Qualitative and quantitative detection of most postmortem findings showed excellent intra- and interobserver agreement with Kappa values>0.8 or ICC>0.75.

CONCLUSION

Pulmonary and hepatic fissural fluid collection as well as intravasal gas accumulation are early time-related image findings in postmortem MRI. The chronological appearance of these findings can be assessed with excellent observer agreement in a porcine model.