T1 relaxation times and MR elastography-derived stiffness: new potential imaging biomarkers for the assessment of chronic pancreatitis

Standardized pancreatic MRI-T1 measurement methods: comparison between manual measurement and a semi-automated pipeline with automatic quality control

OBJECTIVES

Scanner-referenced T1 (srT1) is a method for measuring pancreas T1 relaxation time. The purpose of this multi-centre study is 2-fold: (1) to evaluate the repeatability of manual ROI-based analysis of srT1, (2) to validate a semi-automated measurement method with an automatic quality control (QC) module to identify likely discrepancies between automated and manual measurements.

METHODS

Pancreatic MRI scans from a scan-rescan cohort (46 subjects) were used to evaluate the repeatability of manual analysis. Seven hundred and eight scans from a longitudinal multi-centre study of 466 subjects were divided into training, internal validation (IV), and external validation (EV) cohorts. A semi-automated method for measuring srT1 using machine learning is proposed and compared against manual analysis on the validation cohorts with and without automated QC.

RESULTS

Inter-operator agreement between manual ROI-based method and semi-automated method had low bias (3.8 ms or 0.5%) and limits of agreement [-36.6, 44.1] ms. There was good agreement between the 2 methods without automated QC (IV: 3.2 [-47.1, 53.5] ms, EV: -0.5 [-35.2, 34.2] ms). After QC, agreement on the IV set improved, was unchanged in the EV set, and the agreement in both was within inter-operator bounds (IV: -0.04 [-33.4, 33.3] ms, EV: -1.9 [-37.6, 33.7] ms). The semi-automated method improved scan-rescan agreement versus manual analysis (manual: 8.2 [-49.7, 66] ms, automated: 6.7 [-46.7, 60.1] ms).

CONCLUSIONS

The semi-automated method for characterization of standardized pancreatic T1 using MRI has the potential to decrease analysis time while maintaining accuracy and improving scan-rescan agreement.

ADVANCES IN KNOWLEDGE

We provide intra-operator, inter-operator, and scan-rescan agreement values for manual measurement of srT1, a standardized biomarker for measuring pancreas fibro-inflammation. Applying a semi-automated measurement method improves scan-rescan agreement and agrees well with manual measurements, while reducing human effort. Adding automated QC can improve agreement between manual and automated measurements.

SUMMARY STATEMENT

We describe a method for semi-automated, standardized measurement of pancreatic T1 (srT1), which includes automated quality control. Measurements show good agreement with manual ROI-based analysis, with comparable consistency to inter-operator performance.

Development and validation of a novel chronic pancreatitis pathological grade based on artificial intelligence

BACKGROUND

Effective chronic pancreatitis (CP) treatment requires accurate severity evaluation, but no histopathology grading system exists. This study aimed to develop and validate a novel CP pathological grade (Histopathology-derived CPpG) using quantified pathological and radiological characteristics through deep learning.

METHODS

Patients with pathologically/clinically confirmed CP or recurrent acute pancreatitis were retrospectively enrolled (2011-2023). Whole-slide CP images were automatically segmented and quantified via DeeplabV3+, followed by latent class analysis to develop Histopathology-derived CPpG. A deep learning radiomics score (DLRS) was created to predict Histopathology-derived CPpG using preoperative CT scans of patients with pathologically confirmed CP. CT-predicted CPpG was then validated in an independent group of patients with clinically confirmed CP and recurrent acute pancreatitis.

RESULTS

The study included 2054 patients with CP and recurrent acute pancreatitis, with 181 cases of pathologically confirmed CP. Histopathology-derived CPpG I had a higher proportion of acini, acinus-to-stroma ratio, acinus-to-islet ratio, islet-to-stroma ratio, and (acinus + islet)-to-stroma ratio, and a lower proportion of stroma and lymphocytes compared to CPpG II. The DLRS demonstrated high performance in the validation (AUC, 0.84; 95 % CI: 0.75-0.92) and test (AUC, 0.76; 95 % CI: 0.65-0.87) sets. In a large-scale clinical validation, CT-predicted grades were significantly associated with endocrine and exocrine function, as well as prognosis (P < .05).

CONCLUSION

This study developed a novel pathological classification, Histopathology-derived CPpG, which accurately reflects disease severity. Additionally, the non-invasive DLRS shows great potential for dynamically monitoring CP severity and evaluating pancreatic endocrine and exocrine function, as well as prognosis.

Non-invasive liver fibrosis markers are increased in obese individuals with non-alcoholic fatty liver disease and the metabolic syndrome

The need for early non-invasive diagnostic tools for chronic liver fibrosis is growing, particularly in individuals with obesity, non-alcoholic fatty liver disease (NAFLD), and the metabolic syndrome (MetS) since prevalence of these conditions is increasing. This case-control study compared non-invasive liver fibrosis markers in obesity with NAFLD and MetS (NAFLD-MetS, n = 33), in obese (n = 28) and lean (n = 27) control groups. We used MRI (T1 relaxation times (T1) and liver stiffness), circulating biomarkers (CK18, PIIINP, and TIMP1), and algorithms (FIB-4 index, Forns score, FNI, and MACK3 score) to assess their potential in predicting liver fibrosis risk. We found that T1 (892 ± 81 ms vs. 818 ± 64 ms, p < 0.001), FNI (15 ± 12% vs. 9 ± 7%, p = 0.018), CK18 (166 ± 110 U/L vs. 113 ± 41 U/L, p = 0.019), and MACK3 (0.18 ± 0.15 vs. 0.05 ± 0.04, p < 0.001) were higher in the NAFLD-MetS group compared with the obese control group. Moreover, correlations were found between CK18 and FNI (r = 0.69, p < 0.001), CK18 and T1 (r = 0.41, p < 0.001), FNI and T1 (r = 0.33, p = 0.006), MACK3 and FNI (r = 0.79, p < 0.001), and MACK3 and T1 (r = 0.50, p < 0.001). We show that liver fibrosis markers are increased in obese individuals with NAFLD and MetS without clinical signs of liver fibrosis. More studies are needed to validate the use of these non-invasive biomarkers for early identification of liver fibrosis risk.

Magnetic resonance imaging T1 mapping of the liver, pancreas and spleen in children

PURPOSE

To characterize T1 relaxation times of the pancreas, liver, and spleen in children with and without abdominal pathology.

METHODS

This retrospective study included pediatric patients (< 18-years-old). T1 mapping was performed with a Modified Look-Locker Inversion Recovery sequence. Patients were grouped based on review of imaging reports and electronic medical records. The Kruskal-Wallis test with Dunn's multiple comparison was used to compare groups.

RESULTS

220 participants were included (mean age: 11.4 ± 4.2 years (1.5 T); 10.9 ± 4.5 years (3 T)). Pancreas T1 (msec) was significantly different between subgroups at 1.5 T (p < 0.0001). Significant pairwise differences included: normal (median: 583; IQR: 561-654) vs. acute pancreatitis (731; 632-945; p = 0.0024), normal vs. chronic pancreatitis (700; 643-863; p = 0.0013), and normal vs. acute + chronic pancreatitis (1020; 897-1099; p < 0.0001). Pancreas T1 was also significantly different between subgroups at 3 T (p < 0.0001). Significant pairwise differences included: normal (779; 753-851) vs. acute pancreatitis (1087; 910-1259; p = 0.0012), and normal vs. acute + chronic pancreatitis (1226; 1025-1367; p < 0.0001). Liver T1 was significantly different between subgroups only at 3 T (p = 0.0011) with pairwise differences between normal (818, 788-819) vs. steatotic (959; 848-997; p = 0.0017) and normal vs. other liver disease (882; 831-904; p = 0.0455). Liver T1 was weakly correlated with liver fat fraction at 1.5 T (r = 0.39; 0.24-0.52; p < 0.0001) and moderately correlated at 3 T (r = 0.64; 0.49-0.76; p < 0.0001). There were no significant differences in splenic T1 relaxation times between subgroups.

CONCLUSION

Pancreas T1 relaxation times are higher at 1.5 T and 3 T in children with pancreatitis and liver T1 relaxation times are higher in children with steatotic and non-steatotic chronic liver disease at 3 T.

Intra-pancreatic fat deposition and its relation to obesity: a magnetic resonance imaging study

OBJECTIVES

Intra-pancreatic fat deposition (IPFD) is suspected to be associated with various medical conditions. This study aimed to assess pancreatic fat content in lean and obese individuals, characterize obese individuals with and without IPFD, and explore the underlying mechanisms.

MATERIALS AND METHODS

Sixty-two obese individuals without diabetes and 35 lean controls underwent magnetic resonance imaging (MRI) using proton density fat fraction (PDFF) maps to evaluate pancreatic and hepatic fat content, and visceral adipose tissue (VAT) content. Pancreatic fibrosis was explored by T1 relaxation time and MR elastography (MRE) measurements. Associations between pancreatic fat, measures of obesity and metabolic syndrome were examined using uni- and multivariate regression analyses.

RESULTS

Pancreatic PDFF was higher in obese than in lean controls (median 8.0%, interquartile range (6.1;13.3) % vs 2.6(1.7;3.9)%, p < 0.001). Obese individuals with IPFD (PDFF ≥6.2%) had higher waist circumference (114.0 ± 12.5 cm vs 105.2 ± 8.7 cm, p = 0.007) and VAT (224.9(142.1; 316.1) cm2 vs 168.2(103.4; 195.3) cm2, p < 0.001) than those without. In univariate analysis, pancreatic PDFF in obese individuals correlated with BMI (r = 0.27, p = 0.03), waist circumference (r = 0.44, p < 0.001), VAT (r = 0.37, p = 0.004), hepatic PDFF (r = 0.25, p = 0.046) and diastolic blood pressure (r = 0.32, p = 0.01). However, in multivariate analysis, only VAT was associated to pancreatic fat content. MRI measures of pancreatic fibrosis indicated no evident fibrosis in relation to increased pancreatic fat content.

CONCLUSIONS

Pancreatic fat content was increased in obese individuals compared with lean controls and predominantly correlated with the amount of visceral adipose tissue. Pancreatic fat content was not clearly linked to measures of pancreatic fibrosis.

Single Breath-Hold MR Elastography for Fast Biomechanical Probing of Pancreatic Stiffness

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) stromal disposition is thought to influence chemotherapy efficacy and increase tissue stiffness, which could be quantified noninvasively via MR elastography (MRE). Current methods cause position-based errors in pancreas location over time, hampering accuracy. It would be beneficial to have a single breath-hold acquisition.

PURPOSE

To develop and test a single breath-hold three-dimensional MRE technique utilizing prospective undersampling and a compressed sensing reconstruction (CS-MRE).

STUDY TYPE

Prospective.

POPULATION

A total of 30 healthy volunteers (HV) (31 ± 9 years; 33% male) and five patients with PDAC (69 ± 5 years; 80% male).

FIELD STRENGTH/SEQUENCE

3-T, GRE Ristretto MRE.

ASSESSMENT

First, optimization of multi breath-hold MRE was done in 10 HV using four combinations of vibration frequency, number of measured wave-phase offsets, and TE and looking at MRE quality measures in the pancreas head. Second, viscoelastic parameters delineated in the pancreas head or tumor of CS-MRE were compared against (I) 2D and (II) 3D four breath-hold acquisitions in HV (N = 20) and PDAC patients. Intrasession repeatability was assessed for CS-MRE in a subgroup of healthy volunteers (N = 15).

STATISTICAL TESTS

Tests include repeated measures analysis of variance (ANOVA), Bland-Altman analysis, and coefficients of variation (CoVs). A P-value <.05 was considered statistically significant.

RESULTS

Optimization of the four breath-hold acquisitions resulted in 40 Hz vibration frequency, five wave-phases, and echo time (TE) = 6.9 msec as the preferred method (4BH-MRE). CS-MRE quantitative results did not differ from 4BH-MRE. Shear wave speed (SWS) and phase angle differed significantly between HV and PDAC patients using 4BH-MRE or CS-MRE. The limits of agreement for SWS were [-0.09, 0.10] m/second and the within-subject CoV was 4.8% for CS-MRE.

DATA CONCLUSION

CS-MRE might allow a single breath-hold MRE acquisition with comparable SWS and phase angle as 4BH-MRE, and it may still enable to differentiate between HV and PDAC.

LEVEL OF EVIDENCE

2 Technical Efficacy Stage: 2.

Co-existence of hepatic and pancreatic fibrosis in chronic pancreatitis patients including associated risk factors: a magnetic resonance elastography study

OBJECTIVES

To investigate the co-existence of hepatic and pancreatic fibrosis using magnetic resonance elastography (MRE) in chronic pancreatitis (CP), including the association between hepatic and pancreatic MRE-derived stiffness and exploration of potential etiological risk factors.

MATERIALS AND METHODS

Fifty-four CP patients and 35 healthy controls underwent hepatic and pancreatic MRE with measurements of tissue stiffness. Clinical parameters including stage (probable or definite CP), etiology of CP, the presence of diabetes or exocrine insufficiency, and previous history of common bile duct stenosis were assessed. Uni- and multivariate regression models were used to investigate risk factors associated with hepatic fibrosis/stiffness in CP patients.

RESULTS

Fifteen percent of CP patients and none of the controls had abnormal liver stiffness (>2.5 kPa), p = 0.02. 5.6% of CP patients had liver stiffness indicating F1 fibrosis (>2.93 kPa). However, hepatic stiffness was not higher in patients than in healthy controls (2.20 ± 0.41 vs 2.08 ± 0.21 kPa, p = 0.10). In patients, a positive association was seen between hepatic and pancreatic stiffness (r = 0.270, p = 0.048). In the multivariate analysis (adjusted for age, gender and BMI), liver stiffness was significantly associated with alcoholic etiology of CP (p = 0.029). In contrast, stage of CP, history of common bile duct stenosis, and the presence of diabetes or exocrine insufficiency were not associated with liver stiffness (all p > 0.14).

CONCLUSIONS

Only a modest co-existence of hepatic and pancreatic fibrosis was observed in CP. However, the positive association between hepatic and pancreatic stiffness indicates some level of common pathophysiology. Especially, alcoholic etiology of CP was related to increased hepatic stiffness.

Relationship of Iron Intake, Ferritin, and Hepcidin with the Transverse Relaxation Rate of Water Protons in the Pancreas

(1) Background: There is a paucity of markers of iron metabolism in health and disease. The aim was to investigate the associations of iron metabolism with pancreas transverse water proton relaxation rate (R2water) in healthy individuals and people after an attack of pancreatitis. (2) Methods: All participants underwent a 3.0 T magnetic resonance imaging of the abdomen on the same scanner. High-speed T2-corrected multi-echo (HISTO) acquisition at single-voxel magnetic resonance spectroscopy and inline processing were used to quantify pancreas R2water. Habitual dietary intake of iron was determined using the EPIC-Norfolk food frequency questionnaire. Circulating levels of ferritin and hepcidin were measured. Generalised additive models were used, adjusting for age, sex, body mass index, and haemoglobin A1c. (3) Results: A total of 139 individuals (47 healthy individuals, 54 individuals after acute pancreatitis, and 38 individuals after chronic pancreatitis) were included. Total dietary intake of iron was significantly associated with pancreas R2water, consistently in healthy individuals (p < 0.001), individuals after acute pancreatitis (p < 0.001), and individuals after chronic pancreatitis (p < 0.001) across all the statistical models. Ferritin was significantly associated with pancreas R2water, consistently in healthy individuals (p < 0.001), individuals after acute pancreatitis (p < 0.001), and individuals after chronic pancreatitis (p = 0.01) across all adjusted models. Hepcidin was significantly associated with pancreas R2water in individuals after acute pancreatitis (p < 0.001) and individuals after chronic pancreatitis (p = 0.04) in the most adjusted model. (4) Conclusions: Pancreas R2water, corrected for T2, is related to iron metabolism in both health and pancreatitis. This non-invasive marker could be used for automated in vivo identification of intra-pancreatic iron deposition.

Quantitative synthetic MRI for predicting locally advanced rectal cancer response to neoadjuvant chemoradiotherapy

OBJECTIVES

To investigate the value of pre-treatment quantitative synthetic MRI (SyMRI) for predicting a good response to neoadjuvant chemoradiotherapy (nCRT) in patients with locally advanced rectal cancer.

METHODS

This prospective study enrolled 63 patients with locally advanced rectal cancer scheduled to undergo preoperative chemoradiotherapy from January 2019 to June 2021. T1 relaxation time (T1), T2 relaxation time (T2), proton density (PD) from synthetic MRI, and apparent diffusion coefficient (ADC) from diffusion-weighted imaging (DWI) were measured. Independent-sample t-test, the Mann-Whitney U test, the Delong test, and receiver operating characteristic curve (ROC) analyses were used to predict the pathologic complete response (pCR) and T-downstaging.

RESULTS

Among the 63 patients, 19 (30%) achieved pCR and 44 (70%) did not, and 24 (38%) achieved T-downstaging, while 44 (62%) did not. The mean T1 and T2 values were significantly lower in the pCR group compared with those in the non-pCR group and in the T-downstage group compared with those in the non-T-downstage group (all p < 0.05). There were no significant differences in the PD and ADC values between the two groups. There were no significant differences between the mean values of T1 and T2 for predicting pCR after CRT (AUC, 0.767 vs. 0.831, p = 0.37). There were no significant differences between the AUC values of T1 and T2 values for the assessment of post-CRT T-downstaging (AUC, 0.746 vs. 0.820, p = 0.506).

CONCLUSIONS

In patients with locally advanced rectal cancer, the synthetic MRI-derived T1 relaxation time and T2 relaxation time values are promising imaging markers for predicting a good response to neoadjuvant chemoradiotherapy.

KEY POINTS

• Mean T1 and T2 values were significantly lower in the pathologic complete response group and the T-downstage group. • There were no significant differences in the proton density and apparent diffusion coefficient values between the two groups.

Quantification of parenchymal fibrosis in chronic pancreatitis: relation to atrophy and pancreatic function

BACKGROUND

Non-invasive modalities for assessing chronic pancreatitis (CP) are needed in clinical practice.

PURPOSE

To investigate the correlation between magnetic resonance elastography (MRE)-derived stiffness and T1 relaxation times (as proxies of fibrosis) and explore their relationships to gland volume and pancreatic functions in patients with CP and healthy controls (HCs).

MATERIAL AND METHODS

In 49 patients with CP and 35 HCs, pancreatic stiffness, T1 relaxation times, and gland volume were assessed. Fecal elastase and the presence of diabetes were used to evaluate pancreatic exocrine and endocrine functions. Uni- and multivariable linear regression models were used to analyze correlations between imaging parameters.

RESULTS

There was a positive correlation between MRE-derived stiffness and T1 relaxation times in patients with CP (R² = 0.42; P < 0.001) and HCs (R² = 0.14; P = 0.028). There was no correlation between MRE-derived stiffness and gland volume in patients (R² = 0.007; P = 0.065) or HCs (R² = 0.010; P = 0.57). T1 relaxation time was correlated to gland volume (R² = 0.19; P = 0.002) in patients with CP but not in the HCs (P = 0.056). Severity of pancreatic functional impairment was reflected by increased fibrosis-related parameters in patients without functional impairment, followed by a further increase in fibrosis-related parameters and reduction in gland volume in patients with pancreatic functional impairments.

CONCLUSION

Pancreatic MRE-derived stiffness and T1 relaxation times might reflect early pathophysiological changes in CP. The dynamic correlation with pancreatic function suggests that these parameters may be useful for the non-invasive and early identification of CP.

Single- and multiparameter magnetic resonance imaging for diagnosing and severity grading of chronic pancreatitis

PURPOSE

The study aimed to determine the performance of advanced magnetic resonance imaging (MRI), including a multiparametric MRI-index, for diagnosing and severity grading of chronic pancreatitis (CP) at various functional stages with focus on detection of CP with preserved pancreatic function.

METHODS

Fifty-four CP patients and 35 healthy controls underwent MRI including assessment of pancreatic volume, main pancreatic duct (MPD) diameter, T1 relaxation time, magnetic resonance elastography (MRE) derived stiffness, and intravoxel incoherent motion (IVIM) diffusion-weighted imaging. Patients were categorized into three subgroups: Preserved pancreatic function (n = 14), partial pancreatic insufficiency (exocrine insufficiency or diabetes, n = 25), and complete pancreatic insufficiency (exocrine insufficiency and diabetes, n = 15). A multiparametric MRI-index was based on ordinal logistic regression analysis. Diagnostic performances of MRI parameters for diagnosing CP at different functional stages were determined using receiver operating characteristic (ROC) analysis.

RESULTS

All MRI parameters differed across CP subgroups and healthy controls (all P < 0.001), except for IVIM. T1 relaxation time (ROC area under the curve (ROC-AUC) 0.82), MRE (ROC-AUC 0.88), and MRI-index (ROC-AUC 0.86) showed the highest performance for detecting patients with preserved pancreatic function (early CP) vs. healthy controls. For detecting preserved pancreatic function vs. partial insufficiency, pancreatic volume, MRI-index, and T1 relaxation time performed best (all ROC-AUC > 0.75), with the MRI-index tending to outperform MRE (ROC-AUC 0.77 vs. 0.63; P = 0.10).

CONCLUSION

Quantitative assessments of T1 relaxation time and MRE-derived stiffness seem promising for diagnosing CP at different functional stages and may together with multiparametric MRI-index be used for early identification, staging and monitoring of CP.

Between early and established chronic pancreatitis: A proposal of "acinar-ductal hybrid mechanism"

BACKGROUND/OBJECTIVES

The recently proposed "new mechanistic definition of chronic pancreatitis (CP)" categorized early CP as a reversible condition. However, there is no clear explanation regarding the pathological condition of early CP, the reason for the development of the disease in only a small portion of the patients with risk factors, and the mechanism for transition from a reversible pathological condition to an irreversible one.

METHODS

Based on the available information, a mechanism that could provide answers to the queries associated with CP was proposed.

RESULTS

Acinar-ductal coordination is very important for the physiological secretion of pancreatic juice. Inflammation originating from acinar cells undermines the function of proximal ducts and leads to a vicious cycle of sustained inflammation by increasing the viscosity and decreasing the alkalinity of pancreatic juice. Persistent elevation of ductal pressure due to stagnation of pancreatic juice caused by protein plugs, stones, or fibrous scar of ducts converts the reversible pathological condition of early CP to an irreversible one. Diagnostic criteria for early CP proposed by Japanese researchers have enabled to the recognition of patients showing a progression from early to established CP. However, most patients diagnosed with early CP do not experience progression of the disease, suggesting the inadequate specificity of the criteria.

CONCLUSION

The "acinar-ductal hybrid mechanism" may explain the pathological condition and progression of early CP. To diagnose early CP more accurately, it is essential to discover specific biomarkers that can discriminate "early CP" from "acute pancreatitis (AP)/recurrent acute pancreatitis (RAP)" and "established CP." Therapeutic intervention in clinical practices through various new approaches is expected to improve the prognosis of patients with CP.