Faculty Bibliography

Retrospective electrocardiogram-gated, 2D phase-contrast (PC) flow MRI is routinely used in clinical evaluation of valvular/vascular disease in pediatric patients with congenital heart disease (CHD). In patients not requiring general anesthesia, clinical standard PC is conducted with free breathing for several minutes per slice with averaging. In younger patients under general anesthesia, clinical standard PC is conducted with breath-holding. One approach to overcome this limitation is using either navigator gating or self-navigation of respiratory motion, at the expense of lengthening scan times. An alternative approach is using highly accelerated, free-breathing, real-time PC (rt-PC) MRI, which to date has not been evaluated in CHD patients. The purpose of this study was to develop a 38.4-fold accelerated 2D rt-PC pulse sequence using radial k-space sampling and compressed sensing with 1.5 × 1.5 × 6.0 mm³ nominal spatial resolution and 40 ms nominal temporal resolution, and evaluate whether it is capable of accurately measuring flow in 17 pediatric patients (aortic valve, pulmonary valve, right and left pulmonary arteries) compared with clinical standard 2D PC (either breath-hold or free breathing). For clinical translation, we implemented an integrated reconstruction pipeline capable of producing DICOMs of the order of 2 min per time series (46 frames). In terms of association, forward volume, backward volume, regurgitant fraction, and peak velocity at peak systole measured with standard PC and rt-PC were strongly correlated (R² > 0.76; P < 0.001). Compared with clinical standard PC, in terms of agreement, forward volume (mean difference = 1.4% (3.0% of mean)) and regurgitant fraction (mean difference = -2.5%) were in good agreement, whereas backward volume (mean difference = -1.1 mL (28.2% of mean)) and peak-velocity at peak systole (mean difference = -21.3 cm/s (17.2% of mean)) were underestimated by rt-PC. This study demonstrates that the proposed rt-PC with the said spatial resolution and temporal resolution produces relatively accurate forward volumes and regurgitant fractions but underestimates backward volumes and peak velocities at peak systole in pediatric patients with CHD.

BACKGROUND AND PURPOSE/OBJECTIVE:Conventional imaging frequently shows overlapping features between benign and malignant parotid neoplasms. We investigated dynamic contrast-enhanced MR imaging using golden-angle radial sparse parallel imaging in differentiating parotid neoplasms. MATERIALS AND METHODS/METHODS:= 32) combined semiquantitative time-intensity curve metrics with ADC values. RESULTS:< .001). CONCLUSIONS:Golden-angle radial sparse parallel MR imaging allows high spatial and temporal resolution permeability characterization of parotid neoplasms, with a high negative predictive value for malignancy prediction. Combining time-to-maximum and ADC improves pleomorphic adenoma prediction compared with either metric alone.

Purpose or Case Report: MRI scans are long, and scan durations are unpredictable. Combined with challenges of inter-departmental coordination, this leads to poorer operational efficiency, increased need for sedation (especially in a pediatric population), increased wait time, and overall poorer patient care. There is a need for active, automatic tracking of scan log in a MRI machine to 1) determine operational efficiency, 2)disease specific scan information, 3) identifying patient specific scan metrics.Currently, there exist no customizable open-source solution that can automatically obtain information from MRI scanners. The purpose of this study is to demonstrate implementation of a novel, customizable QI tool that can automatically extract scan log data from a MRI scanner in a pediatric setting. Methods & Materials: 'LogServer' (https://urldefense.proofpoint.com/v2/url?u=https- 3A__yarra.rocks_doc_server_yarralogserver_&d=DwIBAg&c=j5oPpO0eBH1iio48DtsedeElZfc04rx3ExJHeII ZuCs&r=Vk3H8b3- Ln6FkaEcmPdAL_q5c3LYlceRekv38KQMQsQ&m=Tb1QWQ0Q507Fc3Dh_QTwkGuxccnOSDM2YwFar1Khjs w&s=PhuhMD2zw-zB71kInlTbMr387L46mQGBa5ITaQLBNBc&e=) was developed for use in Siemens MRI machines. This uses the 'Yarra' framework-an open source framework for complex MRI reconstructions. 'LogServer' monitors sequences, parses MRI sequences into discrete exams, generates 'EPIC-formatted' patient names, monitors scanner health, and tags exams with body region information. All extracted data were stored in 'PostgreSQL'-an open source database. 'ReDASH', an open source dashboard, was used to create customizable dashboards. In this study, for a clinical MRI scanner, we looked at 1) Daily scanner efficiency, defined as ratio of total hours scanner unused time to total hours (8am-7pm workday), and 2) Scan efficiency, defined as time when scanner was running to total time when the patient was on table.
Result(s): 'LogServer' was successfully able to automatically extract scan logs from MRI machines on an hourly basis, extract all relevant information, and visualize them in needed format using a remote PHI secure web browser. Figure 1 (https://urldefense.proofpoint.com/v2/url?u=https-3A__drive.google.com_open-3Fid- 3D1fvyrSjq96EcHaAv9GenX1&d=DwIBAg&c=j5oPpO0eBH1iio48DtsedeElZfc04rx3ExJHeIIZuCs&r=Vk3H8b 3- Ln6FkaEcmPdAL_q5c3LYlceRekv38KQMQsQ&m=Tb1QWQ0Q507Fc3Dh_QTwkGuxccnOSDM2YwFar1Khjs w&s=nrP1MlFbOaNtb6QumtVnX4lmEegx9lV5WKKnySkiBi8&e= v4b070tFP3l) demonstrates the scanner schedule for any given day. Figure 2 (https://urldefense.proofpoint.com/v2/url?u=https-3A__drive.google.com_open-3Fid- 3D1O7fxAIhWrAeqFVr3qRW&d=DwIBAg&c=j5oPpO0eBH1iio48DtsedeElZfc04rx3ExJHeIIZuCs&r=Vk3H8b 3- Ln6FkaEcmPdAL_q5c3LYlceRekv38KQMQsQ&m=Tb1QWQ0Q507Fc3Dh_QTwkGuxccnOSDM2YwFar1Khjs w&s=oPNXA1NYelrynP08LY1m5MRqoqIgTNPRYaeuh40P1xI&e= 5QyMGaN3F0mnX) shows the scan metrics for a selected patient, including total scan time, idle time during a scan session, as well time for adjustments in scanner. Our daily scanner efficiency for a week was 64% while scan efficiency was 76.3 +/- 10%.
Conclusion(s): We demonstrated a robust customizable QI tool that lets continuous automatic monitoring of MRI scanner. This is a useful tool for hospital administrators, clinical managers, clinical leaders in their informed decision making

PURPOSE/OBJECTIVE:Magnetic resonance imaging protocols for the assessment of quantitative information suffer from long acquisition times since multiple measurements in a parametric dimension are required. To facilitate the clinical applicability, accelerating the acquisition is of high importance. To this end, we propose a model-based optimization framework in conjunction with undersampling 3D radial stack-of-stars data. THEORY AND METHODS/UNASSIGNED:maps are generated from subsampled data by employing model-based reconstruction combined with a regularization functional, coupling information from the spatial and parametric dimension, to exploit redundancies in the acquired parameter encodings and across parameter maps. To cope with the resulting non-linear, non-differentiable optimization problem, we propose a solution strategy based on the iteratively regularized Gauss-Newton method. The importance of 3D-spectral regularization is demonstrated by a comparison to 2D-spectral regularized results. The algorithm is validated for the variable flip angle (VFA) and inversion recovery Look-Locker (IRLL) method on numerical simulated data, MRI phantoms, and in vivo data. RESULTS:maps from accelerated 3D in vivo measurements, e.g. 1.8 s/slice with the VFA method, are in high accordance with fully sampled reference reconstructions. CONCLUSIONS:from highly undersampled radial data by exploiting structural similarities in the imaging volume and across parameter maps.

PURPOSE/OBJECTIVE:MRI methods that have reduced sensitivity to motion are attractive in pediatric applications. In spine imaging, physiologic motion such as respiration and cerebrospinal fluid pulsation can hamper diagnostic image quality. We compare a 3D T1-weighted non-Cartesian radial acquisition with a conventional Cartesian 2D turbo-spin-echo (TSE) acquisition in axial post-contrast spine imaging at 3T. METHODS:Thirty-two patients (mean age 12.2 ± 5.3 years) scheduled for routine clinical spine exams with contrast were enrolled. Three pediatric neuroradiologists compared the two sequences and assessed the presence of motion, the conspicuity of nerve roots, and whether one of the sequences was preferred in visualizing pathology using Likert scales. RESULTS:The Fleiss' kappa statistic for inter-rater agreement was 0.29 (95% confidence interval, 0.15-0.43) for the presence of motion, 0.30 (0.21-0.38) for conspicuity, and 0.37 (0.19-0.55) for sequence preference. Radial images were less sensitive to motion than TSE (p < 0.01). Motion and consequent artifacts were present in all TSE cases, while it was absent in 51% of the radial cases. In depicting nerve roots, radial images were superior in the cervical (p < 0.05), thoracic (p < 0.01), and lumbar spines (p < 0.01). Lastly, in 28 of the 32 patients who demonstrated contrast-enhancing pathology, radial images were preferred in 51% of the cases, while both sequences were equally preferred in 41% of the cases. CONCLUSION/CONCLUSIONS:We demonstrate the potential utility of radial MRI in post-contrast spine imaging. The free-breathing method is robust in generating diagnostic image quality and is superior in visualizing nerve roots and extramedullary metastases than traditional Cartesian TSE acquisitions.

OBJECTIVE:The purpose of this study is to increase the value of MRI by reengineering the MRI workflow at a new imaging center to shorten the interval (i.e., turnaround time) between each patient examination by at least 5 minutes. MATERIALS AND METHODS/METHODS:The elements of the MRI workflow that were optimized included the use of dockable tables, the location of patient preparation rooms, the number of doors per scanning room, and the storage location and duplication of coils. Turnaround times at the new center and at two existing centers were measured both for all patients and for situations when the next patient was ready to be brought into the scanner room after the previous patient's examination was completed. RESULTS:Workflow optimizations included the use of dockable tables, dedicated patient preparation rooms, two doors in each MRI room, positioning the scanner to provide the most direct path to the scanner, and coil storage in the preparation rooms, with duplication of the most frequently used coils. At the new imaging center, the median and mean (± SD) turnaround times for situations in which patients were ready for scanning were 115 seconds (95% CI, 113-117 seconds) and 132 ± 72 seconds (95% CI, 129-135 seconds), respectively, and the median and mean turnaround times for all situations were 141 seconds (95% CI, 137-146 seconds) and 272 ± 270 seconds (95% CI, 263-282 seconds), respectively. For existing imaging centers, the median and mean turnaround times for situations in which patients were ready for scanning were 430 seconds (95% CI, 424-434 seconds) and 460 ± 156 seconds (95% CI, 455-465 seconds), respectively, and the median and mean turnaround times for all situations were 481 seconds (95% CI, 474-486 seconds) and 537 ± 219 seconds (95% CI, 532-543 seconds), respectively. CONCLUSION/CONCLUSIONS:The optimized MRI workflow resulted in a mean time savings of 5 minutes 28 seconds per patient.

BACKGROUND:T1-weighted post-contrast MRI is essential in brain protocols. We demonstrate the feasibility and utility of a 3D non-Cartesian radial acquisition in children. PURPOSE/OBJECTIVE:To compare bulk motion artifacts, image quality, and lesion conspicuity in 3D T1-weighted post-contrast brain MRI between a new fat-suppressed radial gradient-echo and a traditional non-fat-suppressed inversion-recovery Cartesian gradient-echo sequence. MATERIAL AND METHODS/METHODS:Images from 53 patients acquired at 3 Tesla were compared. Three radiologists rated the images in three categories, including the presence of bulk motion and whether it impacted diagnosis, whether one sequence was preferred over the other in overall image quality and conspicuity of vascular structures and lesions, and whether diagnosis was possible if only the new fat-suppressed radial acquisition was obtained. RESULTS:The Fleiss' kappa for inter-rater agreement was 0.67 for bulk motion and 0.54 for sequence preference. Of the 53 cases, 56% were identified to have significant motion on conventional imaging, while only 13% had motion artifacts on the radial acquisition (p < 0.05). There were no cases where motion was seen on the radial acquisition but not on conventional imaging. Both sequences were equally preferred in 87% of the cases. All radiologists agreed that the radial approach had lower gray-white matter contrast than the conventional inversion-recovery method, but preferred the former for making diagnosis in uncooperative patients. CONCLUSION/CONCLUSIONS:We demonstrate the potential utility of a fat-suppressed 3D T1-weighted post-contrast brain gradient-echo sequence in children. The technique is useful in non-sedate pediatric imaging due to its reduced sensitivity to bulk motion.

PURPOSE/OBJECTIVE:-weighted images from a single scan and allows for free-breathing acquisition. THEORY AND METHODS/UNASSIGNED:-weighted gradient-echo (GRE) data. Improved robustness is achieved by extracting a respiratory signal from the GRE data and using it for motion-weighted reconstruction. RESULTS:-weighted Dixon acquisition is possible. CONCLUSION/CONCLUSIONS:-weighted imaging in a single scan. In addition to free-breathing abdominal examination, it promises value for clinical applications that are frequently affected by motion artifacts.