CAD: New Methods
Xingmin Guan, PhD
Postdoctoral Fellow
Indiana University School of Medicine
San Diego, California, United States
Xingmin Guan, PhD
Postdoctoral Fellow
Indiana University School of Medicine
San Diego, California, United States
Xingmin Guan, PhD
Postdoctoral Fellow
Indiana University School of Medicine
San Diego, California, United States
Hsin-Jung Yang, PhD
Assistant Professor
Cedars-Sinai Medical Center
Los Angeles, California, United States
Jane Sykes
Academic Researcher
Lawson Health Research Institute, Ontario, Canada
.jpg "Xinheng Zhang, MSc photo")
Xinheng Zhang, MSc
Ph.D. Candidate
Indiana University School of Medicine
Indianapolis, Indiana, United States
Richard LQ. Tang, MD
Faculty
Indiana University School of Medicine, California, United States
Anthony G. Christodoulou, PhD
Assistant Professor
Cedars-Sinai Medical Center
Los Angeles, California, United States
Behzad Sharif, PhD
Associate Professor of Medicine
Indiana University School of Medicine
Indianapolis, Indiana, United States
Debiao Li, PhD
Professor
Cedars-Sinai Medical Center
Los Angeles, California, United States
Frank S Prato, PhD
Professor
Lawson Health Research Institute, Ontario, United States
Rohan Dharmakumar, PhD
Professor of Medicine, Radiology & Imaging Sciences, Anatomy, Cell Biology & Physiology
Krannert Cardiovascular Research Center, Indiana University School of Medicine
Indianapolis, Indiana, United States
T2* CMR is widely used for detecting hemorrhagic myocardial infarction (MI). However, the conventional T2* CMR (2D breath-held, ECG-gated, multi-gradient-echo) can suffer from limited spatial resolution and motion artifacts. We have recently developed a time-efficient, fully ungated, free breathing, 3D T2* approach using a low-rank tensor (LRT) framework to address the above issues. In this study we investigated the capability of our 3D T2* approach for detecting and characterizing hemorrhagic MI.
Methods:
The proposed LRT approach was built using the previously described low-rank tensor framework1,2. Hemorrhagic MIs were created in canines (n=5) by 3 hours of LAD occlusion, followed by reperfusion. CMR scans were performed in acute phase of MI. Short-axis, conventional 2D and proposed 3D (resolution-matched and two-fold higher resolution) T2*-weighted images, followed by LGE images were acquired in a clinical 3T CMR system. Whole heart acquisition times for conventional 2D, proposed 3D matched resolution and 2-fold higher resolution were approximately 10min, 5min and 10min, respectively. Spatial resolution of conventional 2D and resolution-matched 3D T2* images were: 1.6x1.6x6 mm3; and for higher-resolution 3D were: 1.6x1.6x3 mm3. All images were acquired with 8 echoes from 1.41ms to 15.44 ms. Subsequently, hearts were explanted for validation and ex-vivo images were acquired at an isotropic spatial resolution of 1.0 mm. Intramyocardial hemorrhage (IMH) extent was determined based on mean-2SD criteria and represented as %LV volume.
Results:
Figure 1 shows representative T2* images, along with LGE image for reference. Image scoring performed by two experts on 1 to 5 scale (1 – poor; and 5 - excellent), showed the following: 3.5 ± 0.5 (conventional 2D), which was lower than that observed with proposed 3D approach with matched spatial resolution (3.8 ± 0.3, p< 0.05). The highest image quality scores were found with 2-fold higher-resolution 3D T2* with a score of 3.9 ± 0.5 (p < 0.05). Results of IMH extent measured from different imaging approaches, along with regression analysis, are shown in Fig. 2. Sensitivity and specificity determined using the ex-vivo T2* scans as the ground truth are shown in Fig. 3. Area-under-the-curves from ROC analysis were: 0.67 (conventional 2D); 0.76 (3D LRT) and high-resolution 3D LRT (0.79). Our findings show that the proposed 3D T2* approach provides significant improvement in image quality; and that the inferior image quality of 2D T2* maps was attributable in large part to motion artifacts (unsuccessful breath-holds, poor ECG gating), which was overcome by the 3D proposed approach.
Conclusion:
The proposed 3D T2* mapping can provide much needed improvement in image quality of conventional 2D T2* CMR used for hemorrhage detection without the need for breath holding or cardiac gating, both of which are known problems in acute MI patients. Further studies are needed to directly evaluate the benefits of the proposed approach in clinical setting.