Utilizing Arterial Spin Labeling MRI For Serial Monitoring in Pediatric Patients with Pulmonary Embolisms (RF_SA_483)

Presenting Author(s)

• LT

  Lauren Thai, MD

  Cardiac Fellow
  UT Southwestern Medical Center

Primary Author(s)

• LT

  Lauren Thai, MD

  Cardiac Fellow
  UT Southwestern Medical Center

Co-Author(s)

• PD

  Pezad Doctor, MD

  Pediatric Cardiac MRI/CT fellow
  UT Southwestern Medical Center
• QZ

  Qing Zou, PhD

  CMR Physics
  UT Southwestern
• 

  Joshua Greer, PhD

  MRI Physicist
  Philips Healthcare
• 

  Mansi Gaitonde, MD

  Assistant Professor
  The University of Texas Southwestern Medical Center
• MF

  Munes Fares, MD

  Assistant Professor
  UT Southwestern
• LG

  Lasya Gaur, MD

  Associate Professor, Pediatric Cardiology
  Children's health-University of Texas Southwestern Medical Center
• AZ

  Ayesha Zia, MD

  Associate Profesor,
  Children's health-University of Texas Southwestern Medical Center
• 

  Gerald Greil, MD, PhD

  Professor
  UT Southwestern Medical Center
• 

  Tarique Hussain, MD, PhD

  Professor
  UT Southwestern

Background: Pulmonary embolism (PE) in the pediatric population can cause significant morbidity and mortality.  The gold standard for diagnosing PE is computed tomography pulmonary angiogram (CTPA), which utilizes iodized contrast agents to visualize segmental pulmonary arteries. Although CTPA is readily available, has short acquisition times, and excellent accuracy, the risk of recurrent radiation exposure makes long-term assessment and monitoring with serial CTPAs is difficult to justify.  Arterial spin labeling (ASL) MRI is a free-breathing, radiation-free technique used to measure tissue perfusion in various organs. It has broad utility in neuroimaging but there is a paucity of data in the literature describing ASL imaging in pediatric patients with PE. Our study aims to describe the use of ASL imaging in pediatric patients with PE at our institution.

Methods: Prospective, single center study conducted between 05/2022 and 05/2024 where cardiovascular magnetic resonance (CMR) with ASL imaging was performed on patients ≤ 18 years with CTPA-confirmed PE. Sagittal ASL images were acquired using the Multi-Slice Flow-sensitive Alternating Inversion Recovery (MS-FAIR) technique. The images had 5-8 slices across each lung with 15mm slice thickness and were acquired during free-breathing with four non-selective FOCI (frequency offset corrected inversion) pulses for background suppression to reduce respiratory motion artifacts. No selection of labeling plane is required for this process. These images were analyzed for qualitative and quantitative perfusion deficits and were reviewed by two separate readers. Data were described using standard summary statistics.

Results: From 05/2022 to 05/2024, 27 patients (median age 16.6 years, IQR 15-17, male 48%), met our inclusion criteria. The time between obtaining the CTPA and CMR with ASL imaging ranged from within 5 days to 1 year of the initial diagnosis (median 3 months, IQR 1.8). Twenty-two patients (81%) received their CMR with ASL imaging within 3 months from their CTPA. Of these patients, 11 patients (50%) had a positive CTPA and CMR result that also demonstrated a qualitative perfusion defect in the same location. ASL imaging also allowed for quantitative perfusion data for each segmental lobe. The remaining 11 patients had negative CMR (no perfusion defects), which may be due to the timing and resolution of PE. The 5 remaining patients who had a CMR with ASL imaging >3 months from their initial diagnosis had normal ASL imaging.

Conclusion: In this study, CMR with ASL imaging showed findings that were congruent with CTPA results within a 3-month period. Using ASL imaging is a promising, radiation-free alternative to CTPA for serial monitoring and surveillance in pediatric patients with PE.

Figure 1. A 17-year-old patient diagnosed with left lower lobe pulmonary embolism undergoes imaging with both CTPA (1A) and CMR with arterial spin labeling (1B). The CMR with arterial spin labeling was obtained 2 months after the initial diagnosis, but still demonstrates a perfusion deficit in the same region as seen on CTPA.