Vein of Marshall visualization in cardiac computed tomography

The oblique vein of the left atrium (vein of Marshall) is a small vessel that descends obliquely on the back of the left atrium and ends in the coronary sinus near the area where great cardiac vein continues into the coronary sinus. Its cannulation can be useful, e.g. before selected electrophysiology procedures such as paroxysmal focal atrial fibrillation ablation. Because the vein of Marshall should also be avoided at the site of the implantation of the left ventricle lead, knowledge about its existence, position or diameters could be useful. There is a lack of complex data about the possibilities of visualizing the vein of Marshall in cardiac computed tomography. Methods 354 patients were included into the research. Cardiac computed tomography (Aquilion 64, Toshiba: 64 slices, 0.5 mm; retrospective gating; contrast enhanced) was performed for all of the patients. A precise retrospective analysis of the CT data in all phases (every 10%) of the cardiac cycle during post processing was performed including searching for the target vein by using Vitrea workstations (Vital Images). Both multi planar reformatted reconstructions (MPR) and 3D volume renderings were used. The analyses were performed by two experienced researchers (more than 200 coronary venous system analyses previously performed). Results The vein of Marshall was found in 66 of the 354 patients (16.6%). An example of the visualization is presented in the figure below (MPR and 3D volume rendering). Its ostium to coronary sinus was found an average of 42.6±10.8 mm from the coronary sinus ostium to the right atrium. This value was statistically higher (p=0.0082) in the men (45.3±11.2) compared to the women (38.5±9.7). The vein of Marshall is a small vessel; its average diameter was 1.8±0.8 mm and length of the visible vessel that was measured was 8.7±7.5 mm. It was visualized statistically more frequently (p=0.0009) in the end-systolic phases (30–40–50% RR; 68.85% cases) compared to the end-diastolic phases (70–80% RR; 21.31% cases). Occasionally, it was optimally visualized in the other phases (9.83%). Conclusion It is possible to visualize the vein of Marshall using cardiac computed tomography. Because it exists in about 20% of population, during visualization, special attention needs to paid to obtaining quality images in CT especially in the end-systolic phases. Vein of Marshall imaging (VR, MPR) Funding Acknowledgement Type of funding source: None

Coregistration and Spatial Compounding of Optoacoustic Cardiac Images via Fourier Analysis of Four-Dimensional Data

Volumetric optoacoustic tomography has been shown to provide unprecedented capabilities for ultrafast imaging of cardiovascular dynamics in mice. Three-dimensional imaging rates in the order of 100 Hz have been achieved, which enabled the visualization of transient cardiac events such as arrhythmias or contrast agent perfusion without the need for retrospective gating. The fast murine heart rates (400–600 beats per minute) yet impose limitations when it comes to compounding of multiple frames or accurate registration of multi-spectral data. Herein, we investigate on the capabilities of Fourier analysis of four-dimensional data for coregistration of independent volumetric optoacoustic image sequences of the heart. The fundamental frequencies and higher harmonics of respiratory and cardiac cycles could clearly be distinguished, which facilitated efficient retrospective gating without additional readings. The performance of the suggested methodology was successfully demonstrated by compounding cardiac images acquired by raster-scanning of a spherical transducer array as well as by unmixing of oxygenated and deoxygenated hemoglobin from multi-spectral optoacoustic data.

Motion compensation

This chapter introduces the different methods used to synchronize pulse sequences with both cardiac and respiratory motions, to suppress motion-related blurring and image artefacts. A single frame or a series of images (cine imaging) can be acquired at different time points (cardiac phases) throughout the cardiac cycle by detecting the patient’s heart rate, usually by using an electrocardiogram (ECG) or, in case of poor ECG signals, a pulse oximeter signal. Fast single-shot and segmented k-space acquisition techniques are introduced, and for segmented cine imaging, both prospective and retrospective gating techniques are described. To suppress breathing motion artefacts, acquisitions use respiratory motion techniques. For short acquisition durations, breath-holding is the easiest method to stop the patient’s breathing during data collection. However, for long scans, respiratory gating or respiratory navigated techniques can be used. The principles of these techniques and their applications are presented.

Prognostic Performance of Prospective versus Retrospective Electrocardiographic Gating in Coronary Computed Tomographic Angiography

Coronary computed tomographic angiography (CCTA) with prospective electrocardiographic gating reduces radiation exposure, but its prognostic power for predicting cardiovascular risk in patients with suspected CAD has not been fully validated. To determine whether prospective gating performs as well as retrospective gating in this population, we compared these scan modes in patients undergoing 64-slice CCTA. From January 2009 through September 2011, 1,407 patients underwent CCTA; of these, 915 (mean age, 57.8 ± 13.5 yr; 54% male) had suspected coronary artery disease at the time of CCTA and were included in the study. Prospective gating was used in 195 (21%) and retrospective gating in 720 (79%). The mean follow-up duration was 2.4 ± 0.9 years. Overall, 390 patients (42.6%) had normal results on CCTA, 382 (41.7%) had nonobstructive coronary artery disease, and 143 (15.6%) had obstructive disease. Major adverse cardiac events occurred in 32 patients (3.5%): 11 cardiac deaths, 15 late revascularizations, and 6 nonfatal myocardial infarctions. Total event occurrences were similar in both groups (retrospective, 3.8%; prospective, 2.6%; P=0.42), as were the occurrences of each type of event. On adjusted multivariate analysis, nonobstructive (P=0.015) and obstructive (P <0.001) coronary artery disease were independently associated with major adverse cardiac events. Scan mode was not a predictor of outcome. The mean effective radiation dose was 4 ± 2 mSv for prospective compared with 12 ± 4 mSv for retrospective gating (P <0.01). The prognostic value of CCTA with prospective electrocardiographic gating compares favorably with that of retrospective gating, and it involves significantly less radiation exposure.

Designing a compact MRI motion phantom

Even today, dealing with motion artifacts in magnetic resonance imaging (MRI) is a challenging task. Image corruption due to spontaneous body motion complicates diagnosis. In this work, an MRI phantom for rigid motion is presented. It is used to generate motion-corrupted data, which can serve for evaluation of blind motion compensation algorithms. In contrast to commercially available MRI motion phantoms, the presented setup works on small animal MRI systems. Furthermore, retrospective gating is performed on the data, which can be used as a reference for novel motion compensation approaches. The motion of the signal source can be reconstructed using motor trigger signals and be utilized as the ground truth for motion estimation. The proposed setup results in motion corrected images. Moreover, the importance of preprocessing the MRI raw data, e.g. phase-drift correction, is demonstrated. The gained knowledge can be used to design an MRI phantom for elastic motion.

Absorbed Radiation Dose in Radiosensitive Organs Using 64- and 320-Row Multidetector Computed Tomography: A Comparative Study

Aim. To determine absorbed radiation dose (ARD) in radiosensitive organs during prospective and full phase dose modulation using ECG-gated MDCTA scanner under 64- and 320-row detector modes.Methods. Female phantom was used to measure organ radiation dose. Five DP-3 radiation detectors were used to measure ARD to lungs, breast, and thyroid using the Aquilion ONE scanner in 64- and 320-row modes using both prospective and dose modulation in full phase acquisition. Five measurements were made using three tube voltages: 100, 120, and 135 kVp at 400 mA at heart rate (HR) of 60 and 75 bpm for each protocol. Mean acquisition was recorded in milligrays (mGy).Results. Mean ARD was less for 320-row versus 64-row mode for each imaging protocol. Prospective EKG-gated imaging protocol resulted in a statistically lower ARD using 320-row versus 64-row modes for midbreast (6.728 versus 19.687 mGy,P<0.001), lung (6.102 versus 21.841 mGy,P<0.001), and thyroid gland (0.208 versus 0.913 mGy;P<0.001). Retrospective imaging using 320- versus 64-row modes showed lower ARD for midbreast (10.839 versus 43.169 mGy,P<0.001), lung (8.848 versus 47.877 mGy,P<0.001), and thyroid gland (0.057 versus 2.091 mGy;P<0.001). ARD reduction was observed at lower kVp and heart rate.Conclusions. Dose reduction to radiosensitive organs is achieved using 320-row compared to 64-row modes for both prospective and retrospective gating, whereas 64-row mode is equivalent to the same model 64-row MDCT scanner.

A LabVIEW Platform for Preclinical Imaging Using Digital Subtraction Angiography and Micro-CT

CT and digital subtraction angiography (DSA) are ubiquitous in the clinic. Their preclinical equivalents are valuable imaging methods for studying disease models and treatment. We have developed a dual source/detector X-ray imaging system that we have used for both micro-CT and DSA studies in rodents. The control of such a complex imaging system requires substantial software development for which we use the graphical language LabVIEW (National Instruments, Austin, TX, USA). This paper focuses on a LabVIEW platform that we have developed to enable anatomical and functional imaging with micro-CT and DSA. Our LabVIEW applications integrate and control all the elements of our system including a dual source/detector X-ray system, a mechanical ventilator, a physiological monitor, and a power microinjector for the vascular delivery of X-ray contrast agents. Various applications allow cardiac- and respiratory-gated acquisitions for both DSA and micro-CT studies. Our results illustrate the application of DSA for cardiopulmonary studies and vascular imaging of the liver and coronary arteries. We also show how DSA can be used for functional imaging of the kidney. Finally, the power of 4D micro-CT imaging using both prospective and retrospective gating is shown for cardiac imaging.