Tomographic reconstruction using tilted Laue analyser-based X-ray phase-contrast imaging

Analyser-based phase-contrast imaging (ABPCI) is a highly sensitive phase-contrast imaging method that produces high-contrast images of weakly absorbing materials. However, it is only sensitive to phase gradient components lying in the diffraction plane of the analyser crystal [i.e. in one dimension (1-D)]. In order to accurately account for and measure phase effects produced by the wavefield-sample interaction, ABPCI and other 1-D phase-sensitive methods must achieve 2-D phase gradient sensitivity. An inclined geometry method was applied to a Laue geometry setup for X-ray ABPCI through rotation of the detector and object about the optical axis. This allowed this traditionally 1-D phase-sensitive phase-contrast method to possess 2-D phase gradient sensitivity. Tomographic datasets were acquired over 360° of a multi-material phantom with the detector and sample tilted by 8°. The real and imaginary parts of the refractive index were reconstructed for the phantom.

How accurate is cardiac magnetic resonance in quantitation of primary mitral regurgitation?

Background Since evaluation of mitral regurgitation (MR) in patients with mitral prolapse by echo may be challenging, cardiac MRI (CMR) has been used for identification of patients with severe valve disease. Little is known about potential factors influencing accuracy of this approach. Purpose To study the impact of left ventricular (LV) contouring methods and interobserver variability on quantitation of MR severity. Methods A total of 50 asymptomatic patients with echocardiographically moderate or severe MR were included to LV-REGURGE study and evaluated with CMR by two independent reviewers. LV volumes were calculated on SSFP short axis stack including or excluding intracavitary myocardium into/from the LV volume (“including” or “excluding” method, respectively). Aortic flow volumes were obtained using phase contrast method. Mitral regurgitant volume (RegVol) was calculated by subtracting forward aortic volume from LV stroke volume. Severe MR was diagnosed when RegVol >60mL and/or RegVol/LV stroke volume (RF) >40%. Agreement between MR grading into severe and non-severe, obtained by different tracing methods and different reviewers was assessed using kappa coefficient. Results Left ventricular and mitral regurgitant volumes obtained by “including” method were significantly larger as compared with “excluding” method, see table. “Including” method identified severe MR in 68% while “excluding” method in 57% of cases. Overall agreement between the methods was present in 84% of cases, meaning a substantial rate of agreement (κ 0.67). Within respective methods, interobserver agreement was present in 77% of cases, interpreted as a moderate rate of agreement (κ 0.48–0.54) Conclusion “Including” trabeculae and papillary muscles into the LV cavity volume substantially increases rate of recognizing severe MR, due to larger LV volumes, particularly LV ESV, comparing with the “excluding” method. Moreover, inter-observer variability in similar extent as tracing method seems to impact differentiation between severe and non-severe MR. Funding Acknowledgement Type of funding source: None

NI-08 TRIAL AND PROBLEM OF USING ASL IN INTRAOPERATIVE MRI

INTRODUCTION Magnetic resonance perfusion imaging is considered to be available as grading of brain tumor and follow-up of brain treatment. One of the methods, arterial spin labeling (ASL), is a test that is useful for patients with renal impairment and contrast agent allergy and has low invasiveness because it does not use a contrast agent. However, there have been no reports of ASL in intraoperative MRI (iMRI). PURPOSE In this hospital iMRI (1.5T), it was examined whether ASL could be used to evaluate residual tumor in patients under general anesthesia. CASE STUDY A 75-year-old woman with right temporal lobe Glioblastoma. 43-year-old man, left temporal lobe Diffuse astrocytoma. All performed ASL at the time of MRI imaging for navigation before induction of anesthesia just before surgery and iMRI. In all cases, the blood pressure at iMRI was maintained, and Post Label Delay (PLD) calculated the optimal PLD from the carotid artery velocity measured by iMRI, and defined it as 1800–2200 ms, and performed ASL. RESULTS Actually, imaging by iMRI was almost difficult to visualize, and reflux was not recognized not only in the tumor but also in the gray matter. DISCUSSION The blood flow velocity measurement in the internal carotid artery is performed by the phase contrast method by intraoperative MRI, and the CBF decreases because propofol used during the operation decreases the CBF and also the brain metabolism. However, it has been suggested that it is one of the factors that make evaluation with ASL difficult. Although the iMRI of our hospital is 1.5 T, which is also a subject of investigation, it is thought that there is a limit to ASL imaging in the case of general anesthesia with propofol even from the calculated PLD. CONCLUSION ASL in iMRI at our hospital was not useful.

CSF flowmetry: an innovative technique in diagnosing normal pressure hydrocephalus

Background: Normal pressure hydrocephalus is a very gloomy entity. The objective of this study is to analyse aqueductal velocity parameters by phase contrast MRI CSF flowmetry in Idiopathic Normal pressure hydrocephalus patients (NPH).Methods: This study consists of 72 participants which included 36 patients and 36 matched healthy controls. The study stretched over three years in multicentre tertiary research hospitals using 3T MRI scanner. Both normal MRI sequences and phase contrast CSF flowmetry was done for both group of patients and result analysed using SPSS 17 software.Results: Mean age of patients in our study is 61.07 years. The most common clinical symptom was gait unsteadiness in our study. Most common conventional MRI finding was ventriculomegaly with transependymal seepage of CSF. Amongst CSF flowmetry parameters Aqueductal stroke volume, peak systolic velocity, mean systolic velocity, forward flow volume and backward flow volume were statistically significant in differentiating cases from controls.Conclusions: MRI CSF flowmetry using phase contrast method is an advanced imaging parameter which can non-invasively and reliably detect NPH. Also, it can be used to follow the response to treatment following shunting and can act as a prognostic marker.