Normal pancreatic thickness values in healthy children: an MRI study

Pancreas volumes in pediatric patients following index acute pancreatitis and acute recurrent pancreatitis

BACKGROUND/OBJECTIVES

Pancreas volume derived from imaging may objectively reveal volume loss relevant to identifying sequelae of acute pancreatitis (AP) and ultimately diagnosing chronic pancreatitis (CP). The purposes of this study were to: (1) quantify pancreas volume by imaging in children with either (a) a single episode of AP or (b) acute recurrent pancreatitis (ARP), and (2) compare these volumes to normative volumes.

METHODS

This retrospective study was institutional review board approved. A single observer segmented the pancreas (3D Slicer; slicer.org) on n = 30 CT and MRI exams for 23 children selected from a prospective registry of patients with either an index attack of AP or with ARP after a known index attack date. Patients with CP were excluded. Segmented pancreas volumes were compared to published normal values.

RESULTS

Mean pancreas volumes normalized to body surface area (BSA) in the index AP and ARP groups were 38.2 mL/m2 (range: 11.8-73.5 mL/m2) and 27.9 mL/m2 (range: 8.0-69.2 mL/m2) respectively. 43 % (6/14) of patients post-AP had volumes below the 25th percentile, 1 (17 %) of which was below the 5th percentile (p = 0.3027 vs. a normal distribution). Post-ARP, 44 % (7/16) of patients had volumes below the 5th percentile (p < 0.001).

CONCLUSIONS

A significant fraction (40 %) of children with ARP have pancreas volumes <5th percentile for BSA even in the absence of CP. A similar, but not statistically significant, fraction have pancreas volumes <25th percentile after an index attack of AP. Pancreatic parenchymal volume deserves additional investigation as an objective marker of parenchymal damage from acute pancreatitis and of progressive pancreatitis in children.

Are the thickness and ADC values reliable to evaluate pancreas in children? A retrospective MRI study

PURPOSE

To define the pancreatic thickness on the transverse plane and apparent diffusion coefficient (ADC) values at multiple anatomical locations in the normal pancreas of children and to evaluate inter-rater and intra-rater reliability.

METHODS

Two reviewers measured the thickness and ADC values of the pancreas at four locations obtained from two different 1,5 Tesla MRI scanners [MAGNETOM Symphony (Siemens Medical Systems, Erlangen, Germany) and Signa HDxt(GE Healthcare, Milwaukee, WI, USA)]. Measurements were made based on 190 retrospective MRI examinations. Patients were distributed among ten age groups for thickness measurements and three age groups for ADC measurements between 0 and 18 years.

RESULTS

The thickness measurements from each segment of the pancreas were significantly correlated with patient age, height and weight (p < 0.01). Inter-rater agreement was excellent for pancreatic head (intraclass correlation coefficient (ICC): 0.837) and good for pancreatic neck, body and tail (ICC: 0.646, 0.632 and 0.678, respectively). We also defined the mean ADC values for three age groups. There was significant difference in the mean ADC value of the head and body by both the vendor and age group (p < 0.05). The mean ADC values and mean ranks of the Signa HDxt were significantly higher and the frequencies were lower than those of the MAGNETOM Symphony at all locations (p < 0.001).

CONCLUSION

The thickness of the pancreatic head is more reliable than that at other locations. Pancreatic body and tail measurements are not as reliable as head or neck measurements due to discrepancies between published studies and low interobserver agreement. ADC values of the normal pancreas can be significantly different among vendors; therefore, ADC comparison on follow-up should be performed using same MRI machine.

Pancreas volumes and predictive factors in healthy children

BACKGROUND

Pancreas volume might be a quantitative metric of pancreas health and function in children.

OBJECTIVE

To establish normative pancreas volumes and determine factors associated with pancreas volume.

MATERIALS AND METHODS

We conducted a retrospective study of 140 healthy children (balanced from 0 to 18 years, stratified by age and gender) who underwent contrast-enhanced CT of the abdomen. Pancreas volume was manually segmented by a single reviewer using 3D Slicer and corrected by a pediatric radiologist. We used Bland-Altman difference analysis to quantify differences in initial and refined segmented pancreas volume, and the Mann-Whitney U test to compare continuous variables. We used Pearson correlation for univariate associations. To determine predictors, we used multivariable regression. Finally, we generated quantile regression equations to determine pancreas volume based on age or body surface area (BSA).

RESULTS

Pancreas volume for the study sample ranged from 2 mL to 99 mL. Age (r=0.90, P<0.0001), body mass index (BMI) (r=0.66, P<0.0001), BSA (r=0.94, P<0.0001), height (r=0.91, P<0.0001) and weight (r=0.90, P<0.0001) were all positively correlated with pancreas volume on univariate analysis. On multivariable analysis, BSA (+36 mL/m², P<0.0001) and female gender (-2.8 mL, P=0.062) were significant independent predictors of pancreas volume. The mean difference between initial and refined segmentation was 0.80 mL (95% limits of agreement: -7.9 mL to 9.5 mL).

CONCLUSION

We report pancreas volumes for healthy children. We found that age, BMI, BSA, height and weight were each significantly, positively correlated with pancreas volume in univariate analyses, while BSA and female gender were significant independent predictive factors on multivariable analysis.

Interobserver Agreement for CT and MRI Findings of Chronic Pancreatitis in Children: A Multicenter Ancillary Study Under the INSPPIRE Consortium

BACKGROUND. Imaging findings represent key criteria for diagnosing chronic pancreatitis in children. Understanding radiologists' agreement for imaging findings is critical to standardizing and optimizing diagnostic criteria. OBJECTIVE. The purpose of this study is to evaluate the interobserver agreement among experienced pediatric radiologists for subjective, quantitative, and semiquantitative imaging findings of chronic pancreatitis in children. METHODS. In this retrospective study, CT or MRI examinations performed in children with chronic pancreatitis were submitted by six sites participating in the INSPPIRE (International Study Group of Pediatric Pancreatitis: In Search for a Cure) Consortium. One pediatric radiologist from each of the six sites reviewed examinations; three of the radiologists independently reviewed all CT examinations, and the other three radiologists independently reviewed all MRI examinations. Reviewers recorded 13 categoric imaging findings of chronic pancreatitis and measured pancreas thickness and pancreatic duct diameter. Agreement was assessed using kappa coefficients for the categoric variables and intraclass correlation coefficients (ICCs) for the continuous variables. RESULTS. A total of 76 CT and 80 MRI examinations performed in 110 children (65 girls and 45 boys; mean age, 11.3 ± 4.6 [SD] years) were reviewed. For CT, kappa coefficients for categoric findings ranged from -0.01 to 0.81, with relatively high kappa coefficients noted for parenchymal calcifications (κ = 0.81), main pancreatic duct dilatation (κ = 0.63), and atrophy (κ = 0.52). ICCs for parenchymal thickness measurements ranged from 0.57 in the pancreas head to 0.80 in the body and tail. The ICC for duct diameter was 0.85. For MRI, kappa coefficients for categoric findings ranged from -0.01 to 0.74, with relatively high kappa coefficients noted for main duct irregularity (κ = 0.74), side branch dilatation (κ = 0.70), number of dilated side branches (κ = 0.65), and main duct dilatation (κ = 0.64); kappa coefficient for atrophy was 0.52. ICCs for parenchymal thickness measurements ranged from 0.53 for the neck and body individually to 0.68 in the tail. ICC for duct diameter was 0.77. CONCLUSION. Interobserver agreement was fair to moderate for most CT and MRI findings of chronic pancreatitis in children. CLINICAL IMPACT. This study highlights challenges for the imaging diagnosis of pediatric chronic pancreatitis. Standardized and/or objective criteria are needed given the importance of imaging in diagnosis.