Faculty Bibliography

BACKGROUND:7T cardiac magnetic resonance imaging (MRI) introduces several advantages, as well as some limitations, compared to lower-field imaging. The capabilities of ultra-high field (UHF) MRI have not been fully exploited in cardiac functional imaging. AIM/OBJECTIVE:scans using a multi-channel transceiver modular coil. METHODS:We investigated the effects of adding a dielectric pad at different locations next to the imaged region of interest on improving image quality in subjects with different body habitus. We also investigated the effects of adjusting the imaging flip angle in cine and tagging sequences on improving image quality, B1 field homogeneity, signal-to-noise ratio (SNR), blood-myocardium contrast-to-noise ratio (CNR), and tagging persistence throughout the cardiac cycle. RESULTS:The results showed the capability of achieving improved image quality with high spatial resolution (0.75 mm × 0.75 mm × 2 mm), high temporal resolution (20 ms), and increased tagging persistence (for up to 1200 ms cardiac cycle duration) at 7T cardiac MRI after adjusting scan set-up and imaging parameters. Adjusting the imaging flip angle was essential for achieving optimal SNR and myocardium-to-blood CNR. Placing a dielectric pad at the anterior left position of the chest resulted in improved B1 homogeneity compared to other positions, especially in subjects with small chest size. CONCLUSION/CONCLUSIONS:Improved regional and global cardiac functional imaging can be achieved at 7T MRI through simple scan set-up adjustment and imaging parameter optimization, which would allow for more streamlined and efficient UHF cardiac MRI.

OBJECTIVE:Left ventricular hypertrophy (LVH) is a frequent problem in clinical practice and can be caused by diverse conditions including hypertension, aortic stenosis, hypertrophic cardiomyopathy, athletic training, infiltrative heart muscle disease, storage and metabolic disorders. Identification of the precise etiology can be challenging and is a common cause of referral for cardiac MRI (CMR). In this article, CMR findings in various causes of LVH will be reviewed with an emphasis on determination of etiology and emerging role of CMR in risk stratification. CONCLUSIONS:In patients with LVH, CMR allows precise determination of the severity and distribution of hypertrophy, evaluation of ventricular function, and tissue characterization. The information obtained from CMR enables identification of the etiology of LVH and may aid in determining prognosis and therapy.

Blunt cardiac injuries range from myocardial concussion (commotio cordis) leading to fatal ventricular arrhythmias to myocardial contusion, cardiac chamber rupture, septal rupture, pericardial rupture, and valvular injuries. Blunt injuries account for one-fourth of the traumatic deaths in the United States. Chest radiography, transthoracic echocardiography, CT chest with and without contrast, and CT angiography are usually appropriate as the initial examination in patients with suspected blunt cardiac injury who are both hemodynamically stable and unstable. Transesophageal echocardiography and CT heart may be appropriate as examination in patients with suspected blunt cardiac injuries. This publication of blunt chest trauma-suspected cardiac injuries summarizes the literature and makes recommendations for imaging based on the available data and expert opinion. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

OBJECTIVE. Patients with cardiac implantable electronic devices (CIEDs) require cardiac MRI (CMRI) for a variety of reasons. The purpose of this study is to review and evaluate the value and safety of CMRI for patients with in situ CIEDs. CONCLUSION. Late gadolinium enhancement CMRI is the reference standard for assessing myocardial viability in patients with ventricular tachycardia before ablation of arrhythmogenic substrates. The use of late gadolinium enhancement CMRI for patients with CIEDs is safe as long as an imaging protocol is in place and precaution measures are taken.

OBJECTIVE. A spectrum of pathophysiologic mechanisms can lead to the development of myocardial disorders including ischemia, genetic abnormalities, and systemic disorders. Cardiac MRI identifies different myocardial disorders, provides prognostic information, and directs therapy. In comparison with other imaging modalities, cardiac MRI has the advantage of allowing both functional assessment and tissues characterization in a single examination without the use of ionizing radiation. Newer cardiac MRI techniques including mapping can provide additional information about myocardial disease that may not be detected using conventional techniques. Emerging techniques including MR spectroscopy and finger printing will likely change the way we understand the pathophysiology mechanisms of the wide array of myocardial disorders. CONCLUSION. Imaging of myocardial disorders encompasses a large variety of conditions including both ischemic and nonischemic diseases. Cardiac MRI sequences, such as balanced steady-state free precession and late gadolinium enhancement, play a critical role in establishing diagnosis, determining prognosis, and guiding therapeutic management. Additional sequences-including perfusion imaging, T2*, real-time cine, and T2-weighted sequences-should be performed in specific clinical scenarios. There is emerging evidence for the use of mapping in imaging of myocardial disease. Multiple other new techniques are currently being studied. These novel techniques will likely change the way myocardial disorders are understood and diagnosed in the near future.

RATIONALE AND OBJECTIVES:The journal impact factor (JIF) is often used to assess the prestige of scientific journals. Citations from original articles and reviews as well as citations from noncitable items contribute to the numerator in these calculations. However, since noncitable articles are not included in the denominator, the JIF may be skewed by the types of articles and not accurately reflect the prestige of the journal. The purpose of our study was to develop an alternative and complementary metric by which journals may be assessed. This "adjusted citation rate metric" is based on citations that originate only from citable items in the journal. MATERIAL AND METHODS:We tabulated the number of citations and citable items for original articles from the Web of Science Core Collection for 5 consecutive years (2010-2014) for 20 general radiology journals. The adjusted citation rates (CR) per original article and reviews were calculated using only citations that originated from citable items. RESULTS:The adjusted CR in 2015 was similar to the JIF in 14 of the 20 journals, higher in four journals, and lower in two journals. Using this system, Radiology, Investigative Radiology, and European Radiology remained first, second, and third respectively among journals published in the field of general radiology. To allow for equal distribution of original articles vs reviews among general radiology journals, we calculated the adjusted CR where the standard distribution of original articles is 50%. CONCLUSION:Adjusted citation rate is an objective index for assessing journal impact that can serve as an alternative and complementary metric with which to measure the journal impact.

OBJECTIVE. An important application of late gadolinium enhancement (LGE) cardiac MRI is accurate assessment of myocardial scar before ablation. However, this is often limited in patients with cardiac implantable electronic devices (CIEDs) because of metal device-induced artifacts. The purpose of this study was to determine whether a modified wideband inversion recovery (IR) LGE MRI technique decreases artifact volume to allow the assessment of myocardial scar. SUBJECTS AND METHODS. Fifty patients (17 women and 33 men; mean age ± SD, 61 ± 12 years; mean ejection fraction ± SD, 35.9% ± 13.3%) with CIEDs underwent cardiac MRI using conventional and modified wideband IR LGE techniques before ablation. The volume of device-induced artifact was quantified and stratified by tertiles on mild, moderate, and severe. Ordinal logistic regression analysis assessed the association between artifact volume on conventional and wideband images adjusted for patients' demographics. RESULTS. Conventional LGE MRI resulted in device-induced hyperintense artifacts that obscured ventricular segments in 32 of 50 (64%) cases. Wideband LGE MRI significantly reduced severe artifact volume (p < 0.0001) and completely resolved all mild and most moderate artifacts. Overall, wideband techniques resulted in a 56% reduction in total artifact volume for the cohort (p < 0.0001). The wideband LGE MRI sequence minimized artifacts in the most commonly obscured segments on the conventional LGE MRI sequence, with persistent artifacts in seven, eight, and four of 32 cases at the basal anterior, midventricular anterior, and midventricular anteroseptal segments, respectively. CONCLUSION. The modified wideband IR technique completely resolves mild and moderate device-induced hyperintense artifacts and significantly reduces the volume of severe artifact to allow accurate identification of myocardial scar in patients with CIEDs before ablation.

Cardiac MRI tagging is a valuable technique for evaluating regional heart function. Currently, there are a number of different techniques for analyzing the tagged images. Specifically, k-space-based analysis techniques showed to be much faster than image-based techniques, where harmonic-phase (HARP) and sine-wave modeling (SinMod) stand as two famous techniques of the former group, which are frequently used in clinical studies. In this study, we compared HARP and SinMod and studied inter-observer variability between the two techniques for evaluating myocardial strain and apical-to-base torsion in numerical phantom, nine healthy controls, and thirty diabetic patients. Based on the ground-truth numerical phantom measurements (strain = -20% and rotation angle = -4.4°), HARP and SinMod resulted in overestimation (in absolute value terms) of strain by 1% and 5% (strain values), and of rotation angle by 0.4° and 2.0°, respectively. For the in-vivo results, global strain and torsion ranges were -10.6% to -35.3% and 1.8°/cm to 12.7°/cm in patients, and -17.8% to -32.7% and 1.8°/cm to 12.3°/cm in volunteers. On average, SinMod overestimated strain measurements by 5.7% and 5.9% (strain values) in the patients and volunteers, respectively, compared to HARP, and overestimated torsion measurements by 2.9°/cm and 2.5°/cm in the patients and volunteers, respectively, compared to HARP. Location-wise, the ranges for basal, mid-ventricular, and apical strain in patients (volunteers) were -8.4% to -31.5% (-11.6% to -33.3%), -6.3% to -37.2% (-17.8% to -33.3%), and -5.2% to -38.4% (-20.0% to -33.2%), respectively. SinMod overestimated strain in the basal, mid-ventricular, and apical slices by 4.7% (5.7%), 5.9% (5.5%), and 8.9% (6.8%), respectively, compared to HARP in the patients (volunteers). Nevertheless, there existed good correlation between the HARP and SinMod measurements. Finally, there were no significant strain or torsion measurement differences between patients and volunteers. There existed good inter-observer agreement, as all measurement differences lied within the Bland-Altman ± 2 standard-deviation (SD) difference limits. In conclusion, despite the consistency of the results by either HARP or SinMod and acceptable agreement of the generated strain and torsion patterns by both techniques, SinMod systematically overestimated the measurements compared to HARP. Under current operating conditions, the measurements from HARP and SinMod cannot be used interchangeably.

Virtual reality (VR) systems can offer benefits of improved ergonomics, but their resolution may currently be limited for the detection of small features. For detection of lung nodules, we compared the performance of VR versus standard picture archiving and communication system (PACS) monitor. Four radiologists and 1 novice radiologist reviewed axial computed tomography (CTs) of the thorax using standard PACS monitors (SM) and a VR system (HTC Vive, HTC). In this study, 3 radiologists evaluated axial lung-window CT images of a Lungman phantom. One radiologist and the novice radiologist reviewed axial lung-window patient CT thoracic images (32 patients). This HIPAA-compliant study was approved by the institutional review board. Detection of 227 lung nodules on patient CTs did not result in different sensitivity with SM compared with VR. Detection of 23 simulated Lungman phantom lung nodules on CT with SM resulted in statistically greater sensitivity (78.3%) than with VR (52.2%, P = .041) for 1 of 3 radiologists. The trend was similar but not significant for the other radiologists. There was no significant difference in the time spent by readers reviewing CT images with VR versus SM. These findings indicate that performance of a commercially available VR system for detection of lung nodules may be similar to traditional radiology monitors for assessment of small lung nodules on CTs of the thorax for most radiologists. These results, along with the potential of improving ergonomics for radiologists, are promising for the future development of VR in diagnostic radiology.