T1 signal intensity ratio correlation with T1 mapping in pediatric pancreatitis

Consensus Reporting Standards for CT, MRI, and MRCP of Pediatric Chronic Pancreatitis

Chronic pancreatitis is a fibro-inflammatory syndrome of the pancreas with a prevalence in children of approximately 6 per 100,000. Diagnosis of chronic pancreatitis in a child depends on the presence of imaging findings of chronic pancreatitis in the context of specific clinical features. Currently, a standardized reporting system for imaging findings of chronic pancreatitis in children is lacking, and imaging-based thresholds for abnormality have not been defined. Standardized reporting elements were defined for adults in 2019. Not all of these criteria are directly applicable to children due to recognized changes in the pancreas with normal growth and development. To address the lack of accepted pediatric chronic pancreatitis reporting standards and encourage standardized communication of imaging findings, we convened a group of experienced pediatric radiologists and pediatric gastroenterologists with expertise in pancreatology and interventional endoscopy to define consensus reporting elements and interpretive criteria for findings of pediatric chronic pancreatitis. Based on the existing literature and panel opinion, while leveraging a modified Delphi approach, we propose reporting standards for CT, MRI, and MRCP of pediatric chronic pancreatitis.

T1 signal intensity ratio variability based on sampling strategies in the pancreas of children and young adults

PURPOSE

T1-weighted signal intensity ratios (SIR) comparing pancreas to spleen (SIRps) or muscle (SIRpm) can semiquantitatively assess T1 signal change associated with pancreatitis. However, there is no standardized methodology for generating these ratios. We set out to determine the impact of MRI sequence as well as region of interest (ROI) location, shape, and size on T1 SIR.

METHODS

Retrospective analysis of T1-weighted MR images from 118 patients acquired 2018-2023. A single observer placed ovoid ROIs in the pancreas body/tail and head/uncinate, spleen, and left erector spinae muscle and large irregular ROIs in the pancreas tail and spleen. ROIs were placed on images from two sequences: 3D radial 2 point mDIXON RF spoiled gradient recalled echo sequence (radial) and breath-hold 3D 2-point mDIXON RF spoiled gradient echo (BH). T1 SIR were calculated from mean signal intensity, and agreement was calculated with intraclass correlations coefficients (ICC) and Bland-Altman difference analyses.

RESULTS

118 participants, 57 (48%) female, with mean age 13.7 ± 5.6 years (48%) were included. Agreement was good for SIRps based on irregular versus round ROIs (radial: ICC = 0.90; BH: ICC = 0.91). Agreement was moderate for SIR based on sampling the pancreas body/tail versus head/uncinate (ICC = 0.67-0.76) and poor to moderate based on reference organ (muscle vs. spleen) (ICC = 0.41-0.61). Between sequences, agreement was moderate (ICC = 0.55-0.72, mean difference 0.04-0.09).

CONCLUSION

The size and shape of the ROI used to sample the pancreas does not meaningfully change T1 SIR but the location sampled, the reference organ used, and the MRI sequence used meaningfully change T1 SIR, potentially impacting disease diagnosis and staging.

Practical approach to quantitative liver and pancreas MRI in children

Quantitative abdominal magnetic resonance imaging (MRI) offers non-invasive, objective assessment of diseases in the liver, pancreas, and other organs and is increasingly being used in the pediatric population. Certain quantitative MRI techniques, such as liver proton density fat fraction (PDFF), R2* mapping, and MR elastography, are already in wide clinical use. Other techniques, such as liver T1 mapping and pancreas quantitative imaging methods, are emerging and show promise for enhancing diagnostic sensitivity and treatment monitoring. Quantitative imaging techniques have historically required a breath-hold, making them more difficult to implement in the pediatric population. However, technological advances, including free-breathing techniques and compressed sensing imaging, are making these techniques easier to implement. The purpose of this article is to review current liver and pancreas quantitative techniques and to provide a practical guide for implementing these techniques in pediatric practice. Future directions of liver and pancreas quantitative imaging will be briefly discussed.