Diffusion-weighted magnetic resonance imaging of the pancreas

Multi-parametric MRI combined with radiomics for the diagnosis and grading of endometrial fibrosis

PURPOSE

To evaluate the application of multi-parametric MRI (MP-MRI) combined with radiomics in diagnosing and grading endometrial fibrosis (EF).

METHODS

A total of 74 patients with severe endometrial fibrosis (SEF), 41 patients with mild to moderate fibrosis (MMEF) confirmed by hysteroscopy, and 40 healthy women of reproductive age were prospectively enrolled. The enrolled data were randomly stratified and divided into a train set (108 cases: 28 healthy women, 29 with MMEF, and 51 with SEF) and a test set (47 cases: 12 healthy women, 12 MMEF and 23 SEF) at a ratio of 7:3. All participants underwent T2 and DWI sequence scans. By freely delineating the volume of interest (VOI) of the endometrium in three subgroups, radiomic features were extracted and selected. Two feature selection methods and four machine learning (ML) classifiers were combined in pairs to establish five prediction models [model1 (T2 + ADC + clinical data), model2 (T2 + ADC), model3 (T2), model4 (ADC), and model5 (clinical data)], resulting in a total of 40 classification models. The predictive performance of all models was evaluated using the area under the curve (AUC), F1-score, and accuracy (ACC).

RESULTS

The "UFS-LR" model, which combined unsupervised feature selection (UFS) with the logistic regression (LR) classifier, performed the best, with an average AUC of 0.92 on the test set. Among the five models constructed via UFS-LR, model1 exhibited the best performance, with average AUC, F1-score, and ACC values of 0.92, 0.80, and 0.81, respectively. T2-related features were the most significant in distinguishing fibrosis levels, with T2_wavelet-LLL_gldm_DependenceVariance being the most important characteristic among them.

CONCLUSION

MP-MRI radiomics analysis using ML has excellent performance in grading EF. This approach is non-invasive and has the potential to reduce the reliance on hysteroscopy.

Intrapancreatic fat deposition is unrelated to liver steatosis in metabolic dysfunction-associated steatotic liver disease

Background & Aims

Individuals with obesity may develop intrapancreatic fat deposition (IPFD) and fatty pancreas disease (FPD). Whether this causes inflammation and fibrosis and leads to pancreatic dysfunction is less established than for liver damage in metabolic dysfunction-associated steatotic liver disease (MASLD). Moreover, the interrelations of FPD and MASLD are poorly understood. Therefore, we aimed to assess IPFD and fibro-inflammation in relation to pancreatic function and liver disease severity in individuals with MASLD.

Methods

Seventy-six participants from the Amsterdam MASLD-MASH cohort (ANCHOR) study underwent liver biopsy and multiparametric MRI of the liver and pancreas, consisting of proton-density fat fraction sequences, T1 mapping and intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI).

Results

The prevalence of FPD was 37.3%. There was a clear correlation between pancreatic T1 relaxation time, which indicates fibro-inflammation, and parameters of glycemic dysregulation, namely HbA1c (R = 0.59; p <0.001), fasting glucose (R = 0.51; p <0.001) and the presence of type 2 diabetes (mean 802.0 ms vs. 733.6 ms; p <0.05). In contrast, there was no relation between IPFD and hepatic fat content (R = 0.03; p = 0.80). Pancreatic IVIM diffusion (IVIM-D) was lower in advanced liver fibrosis (p <0.05) and pancreatic perfusion (IVIM-f), reflecting vessel density, inversely correlated to histological MASLD activity (p <0.05).

Conclusions

Consistent relations exist between pancreatic fibro-inflammation on MRI and endocrine function in individuals with MASLD. However, despite shared dysmetabolic drivers, our study suggests IPFD is a separate pathophysiological process from MASLD.

Impact and implications

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most common chronic liver disease worldwide and 68% of people with type 2 diabetes have MASLD. However, fat infiltration and inflammation in the pancreas are understudied in individuals with MASLD. In this cross-sectional MRI study, we found no relationship between fat accumulation in the pancreas and liver in a cohort of patients with MASLD. However, our results show that inflammatory and fibrotic processes in the pancreas may be interrelated to features of type 2 diabetes and to the severity of liver disease in patients with MASLD. Overall, the results suggest that pancreatic endocrine dysfunction in individuals with MASLD may be more related to glucotoxicity than to lipotoxicity.

Clinical trial number

NTR7191 (Dutch Trial Register).

Characterization and correction of cardiovascular motion artifacts in diffusion-weighted imaging of the pancreas

PURPOSE

To assess the effects of cardiovascular-induced motion on conventional DWI of the pancreas and to evaluate motion-robust DWI methods in a motion phantom and healthy volunteers.

METHODS

3T DWI was acquired using standard monopolar and motion-compensated gradient waveforms, including in an anatomically accurate pancreas phantom with controllable compressive motion and healthy volunteers (n = 8, 10). In volunteers, highly controlled single-slice DWI using breath-holding and cardiac gating and whole-pancreas respiratory-triggered DWI were acquired. For each acquisition, the ADC variability across volunteers, as well as ADC differences across parts of the pancreas were evaluated.

RESULTS

In motion phantom scans, conventional DWI led to biased ADC, whereas motion-compensated waveforms produced consistent ADC. In the breath-held, cardiac-triggered study, conventional DWI led to heterogeneous DW signals and highly variable ADC across the pancreas, whereas motion-compensated DWI avoided these artifacts. In the respiratory-triggered study, conventional DWI produced heterogeneous ADC across the pancreas (head: 1756 ± 173 × 10^-6 mm² /s; body: 1530 ± 338 × 10^-6 mm² /s; tail: 1388 ± 267 × 10^-6 mm² /s), with ADCs in the head significantly higher than in the tail (P < .05). Motion-compensated ADC had lower variability across volunteers (head: 1277 ± 102 × 10^-6 mm² /s; body: 1204 ± 169 × 10^-6 mm² /s; tail: 1235 ± 178 × 10^-6 mm² /s), with no significant difference (P ≥ .19) across the pancreas.

CONCLUSION

Cardiovascular motion introduces artifacts and ADC bias in pancreas DWI, which are addressed by motion-robust DWI.

Diffusion-Weighted Imaging in Oncology: An Update

To date, diffusion weighted imaging (DWI) is included in routine magnetic resonance imaging (MRI) protocols for several cancers. The real additive role of DWI lies in the "functional" information obtained by probing the free diffusivity of water molecules into intra and inter-cellular spaces that in tumors mainly depend on cellularity. Although DWI has not gained much space in some oncologic scenarios, this non-invasive tool is routinely used in clinical practice and still remains a hot research topic: it has been tested in almost all cancers to differentiate malignant from benign lesions, to distinguish different malignant histotypes or tumor grades, to predict and/or assess treatment responses, and to identify residual or recurrent tumors in follow-up examinations. In this review, we provide an up-to-date overview on the application of DWI in oncology.

White paper on pancreatic ductal adenocarcinoma from society of abdominal radiology's disease-focused panel for pancreatic ductal adenocarcinoma: Part II, update on imaging techniques and screening of pancreatic cancer in high-risk individuals

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive gastrointestinal malignancy with a poor 5-year survival rate. Its high mortality rate is attributed to its aggressive biology and frequently late presentation. While surgical resection remains the only potentially curative treatment, only 10-20% of patients will present with surgically resectable disease. Over the past several years, development of vascular bypass graft techniques and introduction of neoadjuvant treatment regimens have increased the number of patients who can undergo resection with a curative intent. While the role of conventional imaging in the detection, characterization, and staging of patients with PDAC is well established, its role in monitoring treatment response, particularly following neoadjuvant therapy remains challenging because of the complex anatomic and histological nature of PDAC. Novel morphologic and functional imaging techniques (such as DECT, DW-MRI, and PET/MRI) are being investigated to improve the diagnostic accuracy and the ability to measure response to therapy. There is also a growing interest to detect PDAC and its precursor lesions at an early stage in asymptomatic patients to increase the likelihood of achieving cure. This has led to the development of pancreatic cancer screening programs. This article will review recent updates in imaging techniques and the current status of screening and surveillance of individuals at a high risk of developing PDAC.

Metachronous Pancreatic Ductal Adenocarcinoma with Adjacent Serous Cystadenoma that Was Preoperatively Diagnosed by EUS-FNA: A Case Report and Review of the Literature

Pancreatic serous cystic neoplasms (SCNs), such as serous cystadenoma (SCA), are generally recognized as benign because malignant counterparts of SCNs have been extremely rare. In clinical practice, pancreatic cystic neoplasms diagnosed as SCNs have been managed by conservative observation, as long as the patients remained asymptomatic. We herein report a case of metachronous ductal adenocarcinoma that was discovered during long-term follow-up of SCN and review the related literature. To our knowledge, this was the first reported case of the local presence of ductal adenocarcinoma adjacent to SCA that was preoperatively diagnosed by endoscopic ultrasound-guided fine-needle aspiration.

Quantitative pancreatic MRI: a pathology-based review

MRI plays an important role in the clinical management of pancreatic disorders and interpretation is reliant on qualitative assessment of anatomy. Conventional sequences capturing pancreatic structure can however be adapted to yield quantitative measures which provide more diagnostic information, with a view to increasing diagnostic accuracy, improving patient stratification, providing robust non-invasive outcome measures for therapeutic trials and ultimately personalizing patient care. In this review, we evaluate the use of established techniques such as secretin-enhanced MR cholangiopancreatography, diffusion-weighted imaging, T ₁, T ₂* and fat fraction mapping, but also more experimental methods such as MR elastography and arterial spin labelling, and their application to the assessment of diffuse pancreatic disease (including chronic, acute and autoimmune pancreatitis/IgG4 disease, metabolic disease and iron deposition disorders) and cystic/solid focal pancreatic masses. Finally, we explore some of the broader challenges to their implementation and future directions in this promising area.

DWI of Pancreatic Ductal Adenocarcinoma: A Pilot Study to Estimate the Correlation With Metastatic Disease Potential and Overall Survival

OBJECTIVE

The purpose of this study is to analyze the relationship between the apparent diffusion coefficient (ADC) of pancreatic ductal adenocarcinoma (PDAC) and the presence or development of metastasis and overall survival (OS).

MATERIALS AND METHODS

Of 290 consecutive patients with histopathologically proven PDAC from January 2013 to December 2014, staging DWI was performed for 124 patients. Image quality was adequate in 112 studies. Sixty-five patients were treatment naïve, but 17 of the 65 were excluded because of the presence of other associated pancreatic pathologic abnormalities. Data for the remaining 48 patients (24 men and 24 women; median age, 65.5 years; interquartile range, 56-77 years) were obtained during a 4-year follow-up period (mean [± SD], 397 ± 415.1 days). The correlation between ADC and the presence or development of metastasis was assessed using descriptive statistics. OS was determined and mortality analysis was performed using Pearson correlation and Kaplan-Meier curves.

RESULTS

Of 48 patients, 10 had metastases at staging MRI, and 12 later developed metastatic disease. Among the latter, the mean time from staging MRI to metastasis was 258 ± 274.1 days. Most (86%) metastases were hepatic (n = 19). During the follow-up period, the remaining 26 patients (54%) never developed metastases. Patients with metastatic disease (n = 22) had significantly lower mean ADCs than did those without metastases (1.27 × 10^-3 vs 1.43 × 10^-3 mm²/s; p = 0.047). The ADC of PDAC had a positive correlation with survival: patients with PDAC with lower ADCs (< 1.36 × 10^-3 mm²/s) had significantly worse 4-year OS rates than did patients with higher ADC values (p = 0.036).

CONCLUSION

Pretreatment ADC values of PDAC may be significantly lower in patients who have or will develop metastatic disease and may correlate with worse OS.

Guidelines for the Diagnostic Cross Sectional Imaging and Severity Scoring of Chronic Pancreatitis

The paper presents the international guidelines for imaging evaluation of chronic pancreatitis. The following consensus was obtained: Computed tomography (CT) is often the most appropriate initial imaging modality for evaluation of patients with suspected chronic pancreatitis (CP) depicting most changes in pancreatic morphology. CT is also indicated to exclude other potential intraabdominal pathologies presenting with symptoms similar to CP. However, CT cannot exclude a diagnosis of CP nor can it be used to exclusively diagnose early or mild disease. Here magnetic resonance imaging (MRI) and MR cholangiopancreatography (MRCP) is superior and is indicated especially in patients where no specific pathological changes are seen on CT. Secretin-stimulated MRCP is more accurate than standard MRCP in the depiction of subtle ductal changes. It should be performed after a negative MRCP, when there is still clinical suspicion of CP. Endoscopic ultrasound (EUS) can also be used to diagnose parenchymal and ductal changes mainly during the early stage of the disease. No validated radiological severity scoring systems for CP are available, although a modified Cambridge Classification has been used for MRCP. There is an unmet need for development of a new and validated radiological CP severity scoring system based on imaging criteria including glandular volume loss, ductal changes, parenchymal calcifications and parenchymal fibrosis based on CT and/or MRI. Secretin-stimulated MRCP in addition, can provide assessment of exocrine function and ductal compliance. An algorithm is presented, where these imaging parameters can be incorporated together with clinical findings in the classification and severity grading of CP.

Quantification of parenchymal calcifications in chronic pancreatitis: relation to atrophy, ductal changes, fibrosis and clinical parameters

OBJECTIVES

Parenchymal calcifications are considered a hallmark finding of chronic pancreatitis (CP), but little is known about its relation to the clinical presentation and other morphological features such as atrophy, fibrosis and ductal changes. The aim was to quantify the number and maximal size of parenchymal calcifications assessed on computed tomography (CT) and to explore the association with other CT and magnetic resonance imaging (MRI)-based pancreatic features and clinical parameters.

METHODS

A well-characterised cohort of 54 CP patients was included. CT measurements included number and size of parenchymal calcifications, gland diameter and ductal diameter. MRI measurements included gland volume, ductal diameter, fibrosis (diffusion) and fatty infiltration (Dixon). Clinical parameters included body mass index (BMI), CP duration and aetiology, M-ANNHEIM clinical stage, tobacco use, alcohol consumption, the presence of diabetes, faecal elastase, clinical pain score and quality of life.

RESULTS

There were no correlations between the number and size of parenchymal calcifications and any of the other morphological CT and MRI parameters (all p > .05), except for larger size of calcifications in patients with high number of calcifications (p < .001). The number of parenchymal calcifications was negatively correlated with BMI (r = -0.35, p = .0088). The number and size of parenchymal calcifications did not correlate with any of the other clinical parameters (all p > .2).

CONCLUSION

Our findings could indicate the existence of parenchymal calcifications as an independent pathophysiological process involved in the development of CP. Translational impact: Quantifications of calcifications could, in combination with other imaging biomarkers, be a useful imaging marker relevant for characterising CP.

Pancreatic Cancer Diagnosis and Management: Has the Time Come to Prick the Bubble?

Pancreatic cancer (PC) is associated with poor prognosis and very dismal survival rates. The most effective possibility of cure is tumor resection, which is only possible in about 15% of patients diagnosed at early stages of disease progression. Recent whole-genome sequencing studies pointed genetic alterations in 12 core signaling pathways in PC. These observations hint at the possibility that the initial mutation in PC might appear nearly 20 years before any symptoms occur, suggesting that a large window of opportunity may exist for early detection. Biomarkers with the potential to identify pre-neoplastic disease or very early stages of cancer are of great promise to improve patient survival. The concept of liquid biopsy refers to a minimally invasive sampling and analysis of liquid biomarkers that can be isolated from body fluids, primarily blood, urine and saliva. A myriad of circulating molecules may be useful as tumor markers, including cell-free DNA (cfDNA), cell-free RNA (cfRNA), circulating tumor cells (CTC), circulating tumor proteins, and extracellular vesicles, more specifically exosomes. In this review, we discuss with more detail the potential role of exosomes in several aspects related to PC, from initiation to tumor progression and its applicability in early detection and treatment. Exosomes are small circulating extracellular vesicles of 50-150 nm in diameter released from the plasma membrane by almost all cells and exhibit some advantages over other biomarkers. Exosomes are central players of intercellular communication and they have been implicated in a series of biological process, including tumorigenesis, migration and metastasis. Several exosomal microRNAs and proteins have been observed to distinguish PC from benign pancreatic diseases and healthy controls. Besides their possible role in diagnosis, understanding exosomes functions in cancer has clarified the importance of microenvironment in PC progression as well as its influence in proliferation, metastasis and resistance to chemotherapy. Increasing knowledge on cancer exosomes provides valuable insights on new therapeutic targets and can potentially open new strategies to treat this disease. Continuous research is needed to ascertain the reliability of using exosomes and their content as potential biomarkers, so that, hopefully, in the near future, they will provide the opportunity for early diagnosis, treatment intervention and increase survival of PC patients.

Value of diffusion-weighted magnetic resonance imaging in predicting World Health Organization grade in G1/G2 pancreatic neuroendocrine tumors

The present study aimed to investigate the value of diffusion-weighted magnetic resonance imaging (DWI) in the grading of well-differentiated pancreatic neuroendocrine tumors (PanNETs). A total of 44 patients with histologically proven well-differentiated PanNET [grade 1 (G1) and grade 2 (G2) according to the World Health Organization (WHO) criteria] underwent pretreatment magnetic resonance imaging (MRI), which was retrospectively analyzed. The location, size, cystic or solid appearance, boundary, presence or absence of tumor contrast enhancement, and MRI signal of the tumor were assessed. Apparent diffusion coefficients (ADCs) within the primary tumor were measured on ADC maps. Receiver operating characteristic curves were used to determine ADC cut-off values and the sensitivity and specificity of the grade prediction. Spearman's rank correlation was utilized to probe the association between ADC value and PanNET grade or pathological parameters. G1 tumors exhibited a well-circumscribed border more often than G2 tumors. No marked differences were observed between PanNET G1 and PanNET G2 for cystic or solid appearance, enhancement, and T1- and T2-weighted imaging signals. Marked hyperintensities were more common in PanNET G2 tumors than in PanNET G1 tumors (P<0.01). The mean ADC values were statistically different between the normal pancreas and G1 and G2 tumors (P<0.01), and between PanNET G1 and PanNET G2 (P<0.05). Correlation analysis showed that ADC value was negatively correlated with PanNET grade, mitotic count and Ki-67 proliferation index (P<0.05). The cut-off ADC value was 0.930×10^-3 mm²/sec, which identified G2 tumors with 82.4% sensitivity and 79.5% selectivity. ADC value therefore represents a non-invasive and valuable imaging parameter in predicting the WHO grade of tumors in well-differentiated PanNET.

Pancreatic hardness: Correlation of surgeon’s palpation, durometer measurement and preoperative magnetic resonance imaging features

AIM

To evaluate the correlation between subjective assessments of pancreatic hardness based on the palpation, objective measurements using a durometer, and magnetic resonance imaging (MRI) findings for assessing pancreatic hardness.

METHODS

Eighty-three patients undergoing pancreatectomies were enrolled. An experienced surgeon subjectively evaluated the pancreatic hardness in the surgical field by palpation. The pancreatic hardness was also objectively evaluated using a durometer. Preoperative MRI findings were evaluated by a radiologist in terms of the apparent diffusion coefficient (ADC) values, the relative signal intensity decrease (RSID) of the pancreatic parenchyma, and the diameter of the pancreatic parenchyma and duct. Durometer measurement results, ADC values, RSID, pancreatic duct and parenchyma diameters, and the ratio of the diameters of the duct and parenchyma were compared between pancreases judged to be soft or hard pancreas on the palpation. A correlation analysis was also performed between the durometer and MRI measurements.

RESULTS

The palpation assessment classified 44 patients as having a soft pancreas and 39 patients as having a hard pancreas. ADC values were significantly lower in the hard pancreas group. The ductal diameter and duct-to-pancreas ratio were significantly higher in the hard pancreas group. For durometer measurements, a correlation analysis showed a positive correlation with the ductal diameter and the duct-to-pancreas ratio and a negative correlation with ADC values.

CONCLUSION

Hard pancreases showed lower ADC values, a wider pancreatic duct diameter and a higher duct-to-pancreas ratio than soft pancreases. Additionally, the ADC values, diameter of the pancreatic duct and duct-to-pancreas ratio were closely correlated with the durometer results.

Pancreatic cancer

Pancreatic cancer is a highly lethal disease, for which mortality closely parallels incidence. Most patients with pancreatic cancer remain asymptomatic until the disease reaches an advanced stage. There is no standard programme for screening patients at high risk of pancreatic cancer (eg, those with a family history of pancreatic cancer and chronic pancreatitis). Most pancreatic cancers arise from microscopic non-invasive epithelial proliferations within the pancreatic ducts, referred to as pancreatic intraepithelial neoplasias. There are four major driver genes for pancreatic cancer: KRAS, CDKN2A, TP53, and SMAD4. KRAS mutation and alterations in CDKN2A are early events in pancreatic tumorigenesis. Endoscopic ultrasonography and endoscopic ultrasonography-guided fine-needle aspiration offer high diagnostic ability for pancreatic cancer. Surgical resection is regarded as the only potentially curative treatment, and adjuvant chemotherapy with gemcitabine or S-1, an oral fluoropyrimidine derivative, is given after surgery. FOLFIRINOX (fluorouracil, folinic acid [leucovorin], irinotecan, and oxaliplatin) and gemcitabine plus nanoparticle albumin-bound paclitaxel (nab-paclitaxel) are the treatments of choice for patients who are not surgical candidates but have good performance status.

Evaluation of the Added Value of Diffusion-Weighted Imaging to Conventional Magnetic Resonance Imaging in Pancreatic Neuroendocrine Tumors and Comparison With 68Ga-DOTANOC Positron Emission Tomography/Computed Tomography

OBJECTIVES

The aims of this study were to investigate the added value of diffusion-weighted imaging (DWI) in pancreatic neuroendocrine tumor (pNET) evaluation and to compare magnetic resonance imaging (MRI) to Ga-DOTANOC positron emission tomography/computed tomography (PET/CT) results.

METHODS

Morphological MRI (T2-weighted [T2-w] + contrast-enhanced [CE] T1-w) and DWI (T2-w + DWI) and Ga-DOTANOC PET/CT in 25 patients/30 pNETs were retrospectively evaluated. Per-patient and per-lesion detection rates (pDR and lDR, respectively) were calculated. Apparent diffusion coefficient values were compared among pNET and surrounding and normal pancreas (control group, 18 patients). Apparent diffusion coefficient and standardized uptake value (SUV) values were compared among different grading and staging groups.

RESULTS

No statistically significant differences in PET/CT and MRI session detection rates were found (morphological MRI and DW-MRI, 88% pDR and 87% lDR; combined evaluation, 92% pDR and 90% lDR; Ga-DOTANOC PET/CT, 88% pDR and 80% lDR). Consensus reading (morphological/DW-MRI + PET/CT) improved pDR and lDR (100%). Apparent diffusion coefficient mean value was significantly lower compared with surrounding and normal parenchyma (P < 0.01). The apparent diffusion coefficient and SUV values of pNETs among different grading and staging groups were not statistically different.

CONCLUSIONS

Conventional MRI, DW-MRI + T2-w sequences, and Ga-DOTANOC PET/CT can be alternative tools in pNET detection. Diffusion-weighted MRI could be valuable in patients with clinical suspicion but negative conventional imaging findings. However, the consensus reading of the 3 techniques seems the best approach.

The Correlation Between Diffusion-Weighted Imaging at 3.0-T Magnetic Resonance Imaging and Histopathology for Pancreatic Ductal Adenocarcinoma

PURPOSE

The aim of this study was to discuss the correlation between diffusion-weighted imaging (DWI) at 3.0-T magnetic resonance and histopathology for pancreatic ductal adenocarcinoma (PDA).

MATERIALS AND METHODS

Twenty-eight patients with histopathologically proven PDA were included in this study after 108 cases of suspected pancreatic tumors had been performed with DWI. The sequences of DWI included respiratory-triggered DWI and breath-hold DWI, which were performed with 2 b values (0 and 500 s/mm; 0 and 1000 s/mm), respectively. According to magnetic resonance images, wax blocks and slices were selected and stained with hematoxylin-eosin for anti-vascular endothelial growth factor (VEGF), anti-CD34, and anti-Ki-67 (Mib-1). The relationship between tumor apparent diffusion coefficient (ADC) and tumor fibrosis, as well as the expression of tumor VEGF, Ki-67, and multivessel density (MVD), were studied.

RESULTS

The ADC values of PDA of different grades of differentiation and fibrosis grade did not show statistically significant difference. The ADC values of PDA did not show the statistically significant correlation with the grades of differentiation, fibrosis grade, Ki-67 expression, and expression of VEGF and MVD.

CONCLUSIONS

The ADC of PDA cannot be used to reflect grades of differentiation, degree of tumor fibrosis, the expression of VEGF, the expression of Ki-67, and the tumor MVD.

Reduced Field-of-View Diffusion-Weighted Magnetic Resonance Imaging of the Pancreas: Comparison with Conventional Single-Shot Echo-Planar Imaging

Objective

To investigate the image quality (IQ) and apparent diffusion coefficient (ADC) of reduced field-of-view (FOV) di-ffusion-weighted imaging (DWI) of pancreas in comparison with full FOV DWI.

Materials and Methods

In this retrospective study, 2 readers independently performed qualitative analysis of full FOV DWI (FOV, 38 × 38 cm; b-value, 0 and 500 s/mm²) and reduced FOV DWI (FOV, 28 × 8.5 cm; b-value, 0 and 400 s/mm²). Both procedures were conducted with a two-dimensional spatially selective radiofrequency excitation pulse, in 102 patients with benign or malignant pancreatic diseases (mean size, 27.5 ± 14.4 mm). The study parameters included 1) anatomic structure visualization, 2) lesion conspicuity, 3) artifacts, 4) IQ score, and 5) subjective clinical utility for confirming or excluding initially considered differential diagnosis on conventional imaging. Another reader performed quantitative ADC measurements of focal pancreatic lesions and parenchyma. Wilcoxon signed-rank test was used to compare qualitative scores and ADCs between DWI sequences. Mann Whitney U-test was used to compare ADCs between the lesions and parenchyma.

Results

On qualitative analysis, reduced FOV DWI showed better anatomic structure visualization (2.76 ± 0.79 at b = 0 s/mm² and 2.81 ± 0.64 at b = 400 s/mm²), lesion conspicuity (3.11 ± 0.99 at b = 0 s/mm² and 3.15 ± 0.79 at b = 400 s/mm²), IQ score (8.51 ± 2.05 at b = 0 s/mm² and 8.79 ± 1.60 at b = 400 s/mm²), and higher clinical utility (3.41 ± 0.64), as compared to full FOV DWI (anatomic structure, 2.18 ± 0.59 at b = 0 s/mm² and 2.56 ± 0.47 at b = 500 s/mm²; lesion conspicuity, 2.55 ± 1.07 at b = 0 s/mm² and 2.89 ± 0.86 at b = 500 s/mm²; IQ score, 7.13 ± 1.83 at b = 0 s/mm² and 8.17 ± 1.31 at b = 500 s/mm²; clinical utility, 3.14 ± 0.70) (p < 0.05). Artifacts were significantly improved on reduced FOV DWI (2.65 ± 0.68) at b = 0 s/mm² (full FOV DWI, 2.41 ± 0.63) (p < 0.001). On quantitative analysis, there were no significant differences between the 2 DWI sequences in ADCs of various pancreatic lesions and parenchyma (p > 0.05). ADCs of adenocarcinomas (1.061 × 10^-3 mm²/s ± 0.133 at reduced FOV and 1.079 × 10^-3 mm²/s ± 0.135 at full FOV) and neuroendocrine tumors (0.983 × 10^-3 mm²/s ± 0.152 at reduced FOV and 1.004 × 10^-3 mm²/s ± 0.153 at full FOV) were significantly lower than those of parenchyma (1.191 × 10^-3 mm²/s ± 0.125 at reduced FOV and 1.218 × 10^-3 mm²/s ± 0.103 at full FOV) (p < 0.05).

Conclusion

Reduced FOV DWI of the pancreas provides better overall IQ including better anatomic detail, lesion conspicuity and subjective clinical utility.

Imaging of pancreatic neoplasms

Ductal adenocarcinoma accounts for 85% to 90% of all solid pancreatic neoplasms, is increasing in incidence, and is the fourth leading cause of cancer-related deaths. There are currently no screening tests available for the detection of ductal adenocarcinoma. The only chance for cure in pancreatic adenocarcinoma is surgery. Imaging has a crucial role in the identification of the primary tumor, vascular variants, identification of metastases, disease response assessment to treatment, and prediction of respectability. Pancreatic neuroendocrine neoplasms can have a distinctive appearance and pattern of spread, which should be recognized on imaging for appropriate management of these patients.

Diffusion-weighted magnetic resonance imaging indicates the severity of acute pancreatitis

PURPOSE

To test the use of diffusion-weighted magnetic resonance imaging (DW-MRI) to differentiate between different degrees of severity of acute pancreatitis (AP).

METHOD

Thirty-six patients who underwent DW-MRI and magnetic resonance cholangiopancreatography were divided into patients with mild AP (mAP, n = 15), patients with necrotizing AP (nAP, n = 8), and patients with a normal pancreas (nP, n = 15; controls). The pancreas was divided into head, body, and tail, and each segment was classified according to image features: pattern 1, normal; pattern 2, mild inflammation; and pattern 3, necrosis. Apparent diffusion coefficients (ADCs) were measured in each segment and correlated with clinical diagnoses.

RESULTS

A total of 108 segments was assessed (three segments per patient). Segments classified as pattern 1 in the nP and mAP groups showed similar ADC values (P = 0.29). ADC values calculated for the pancreatic segments grouped according to the different image patterns (1-3) were significantly different (P < 0.001). Comparisons revealed significant differences in signal intensity between all three patterns (P < 0.05).

CONCLUSIONS

DW-MRI was a compatible and safe image option to differentiate tissue image patterns in patients with mAP, nAP, and nP, mainly in those with contraindications to contrast-enhanced MRI (which is classically required for determining the presence of necrosis) or computed tomography. ADC measures allowed precise differentiation between patterns 1, 2, and 3.

Quantified ADC histogram analysis: a new method for differentiating mass-forming focal pancreatitis from pancreatic cancer

BACKGROUND

As their prognosis and management are different, differentiation of mass-forming focal pancreatitis (FP) from pancreatic adenocarcinoma (PC) is important. However, the similar clinical presentations and imaging features of these conditions, along with inconclusive biopsy results can make such differentiation difficult.

PURPOSE

To determine whether apparent diffusion coefficient (ADC) histogram analysis can discriminate between a normal pancreas, FP, and PC.

MATERIAL AND METHODS

In a retrospective study, 25 PC patients, 14 FP patients, and 25 subjects with a normal pancreas underwent breath-hold diffusion-weighted imaging (DWI) on a 3.0 T magnetic resonance (MR) scanner. Regions of interest (ROIs) were drawn on the normal pancreases and on the entire focal lesions of both PC and FP. The ADC value was averaged from the lowest to 10th, 30th, 50th, and 100th percentile of the histogram (i.e. ADC10, ADC30, ADC50, and ADC100, respectively), and the results were analyzed statistically.

RESULTS

There were no significant differences among the head, body, and tail of normal pancreases for any of the mean ADC values (P > 0.05). ADC10, ADC30, and ADC50 values demonstrated significant differences between lesion and non-lesion areas of both PC (P < 0.05) and FP (P < 0.05). Differences in lesion areas between PC and FP were found with ADC50 and ADC100 values (P < 0.05), and helped differentiate a normal pancreas from FP and PC, and FP from PC.

CONCLUSION

Quantified ADC histogram can specifically reflect tissue heterogeneity and help differentiate a normal pancreas from FP and PC.

Diffusion-weighted magnetic resonance imaging of the pancreas: diagnostic benefit from an intravoxel incoherent motion model-based 3 b-value analysis

OBJECTIVES

The objective of this study was to evaluate the diagnostic benefit of an intravoxel incoherent motion (IVIM) model-based characterization of pancreatic masses from diffusion-weighted imaging (DWI) with 3 b values.

MATERIALS AND METHODS

This retrospective study had an approval from the institutional review board, and informed patient consent was waived. The 1.5-T DWI data of 42 patients with or without pancreatic disease, acquired by a respiratory-gated spin-echo echo-planar imaging sequence with 3 b values (0, 50, 800 s/mm²), were retrospectively analyzed. The IVIM-related parameters D', which is the apparent diffusion coefficient [ADC(50,800)], and f', as well as ADC(0,50), and conventional ADC(0,800) were calculated voxelwise. Regions of interest were analyzed in pancreatic adenocarcinomas (CAs, n = 12), neuroendocrine pancreatic tumors (NETs, n = 9), and chronic pancreatitis (CPs, n = 11), not affected tissue of each pathologic group, and in the head, body, and tail of the healthy pancreas (n = 10).

RESULTS

By ADC(0,800) and D', CAs could hardly be distinguished from neuroendocrine pancreatic tumors and chronic pancreatitis. However, CAs revealed very low ADC(0,50) and f' values, which differed significantly from all other groups. In the healthy pancreas, ADC(0,800) and D' values were significantly higher for the head than for the body and tail, but no significant differences were found for ADC(0,50) and f'.

CONCLUSIONS

The determination of IVIM-based microcirculation-sensitive parameter maps from DWI with 3 b values significantly improved the discrimination of CAs from NETs, CPs, and the healthy tissue.

Characterization and correction of eddy-current artifacts in unipolar and bipolar diffusion sequences using magnetic field monitoring

Diffusion tensor imaging (DTI) of moving organs is gaining increasing attention but robust performance requires sequence modifications and dedicated correction methods to account for system imperfections. In this study, eddy currents in the "unipolar" Stejskal-Tanner and the velocity-compensated "bipolar" spin-echo diffusion sequences were investigated and corrected for using a magnetic field monitoring approach in combination with higher-order image reconstruction. From the field-camera measurements, increased levels of second-order eddy currents were quantified in the unipolar sequence relative to the bipolar diffusion sequence while zeroth and linear orders were found to be similar between both sequences. Second-order image reconstruction based on field-monitoring data resulted in reduced spatial misalignment artifacts and residual displacements of less than 0.43 mm and 0.29 mm (in the unipolar and bipolar sequences, respectively) after second-order eddy-current correction. Results demonstrate the need for second-order correction in unipolar encoding schemes but also show that bipolar sequences benefit from second-order reconstruction to correct for incomplete intrinsic cancellation of eddy-currents.

Staging accuracy of MR for pancreatic neuroendocrine tumor and imaging findings according to the tumor grade

PURPOSE

To investigate staging accuracy of MR for pancreatic neuroendocrine neoplasms (PNETs) and imaging findings according to the tumor grade.

MATERIALS AND METHODS

Our study consisted of 39 patients with PNET G1 (n = 24), PNET G2 (n = 12), and pancreatic neuroendocrine carcinoma (PNEC) (n = 3). All underwent preoperative MRI. Two radiologists retrospectively reviewed MR findings including tumor margin, SI on T2WI, enhancement patterns, degenerative change, duct dilation, and ADC value. They also assessed T-stage, N-stage, and tumor size. Statistical analyses were performed using Chi square tests, ROC analysis, and Fisher's exact test.

RESULTS

Specific findings for PNEC or PNET G2 were ill-defined borders (P = 0.001) and hypo-SI on venous- and delayed-phase (P = 0.016). ADC value showed significant difference between PNET G1 and G2 (P = 0.007). The Az of ADC value for differentiating PNET G1 from G2 was 0.743. Sensitivity and specificity were 70% and 86%. Accuracy for T-staging was 77% (n = 30) and 85% (n = 33), and for N-staging was 92% (n = 36) and 87% (n = 34) with moderate agreement. T-stage showed significant difference according to tumor grade (P < 0.001), although there was no significant difference in tumor size or N-stage.

CONCLUSION

Ill-defined borders and hypo-SI on venous- and delayed-phase imaging are common findings of higher grade PNET, and ADC value is helpful for differentiating PNET G1 from G2. MR is useful for preoperative evaluation of T-, N-stage. Tumor size of PNET and T-stage showed significant difference according to tumor grade.

Diagnostic evaluation of solid pancreatic masses

Determining the etiology of a solid pancreatic lesion is a critical first step toward developing an appropriate treatment plan for patients with a benign or malignant pancreatic mass. Technological advances in cross-sectional and endoscopic imaging modalities offer pancreatic imaging options with degrees of resolution that were not available even 15-20 years ago. In most cases, the nature of a solid pancreatic mass can be determined using computerized tomography, magnetic resonance imaging, and endoscopic ultrasound with fine-needle aspiration. Knowledge about the basics of these modalities, as well as their strengths and limitations, plays an important role in understanding how patients with solid pancreatic masses should be evaluated.

Use of diffusion-weighted MRI to differentiate chronic pancreatitis from pancreatic cancer

OBJECTIVE

The purpose of this study was to compare diffusion-weighted MRI (DWI) and conventional (non-DWI) MRI sequences in differentiating mass-forming chronic pancreatitis from pancreatic cancer.

MATERIALS AND METHODS

A retrospective cohort study included 36 patients who underwent pancreatic resection for pancreatic cancer (n = 13) and chronic pancreatitis (n = 23) after preoperative MRI with DWI. Two independent reviewers assessed the DW images for signal intensity and apparent diffusion coefficient (ADC) values. Four weeks later, they reviewed the other MR images for size of mass, double-duct sign, pancreatic duct cutoff, and perivascular soft-tissue cuffing. A score for conventional MRI was given with 1 meaning definitely benign and 5 meaning definitely malignant. Univariate and multivariate analyses and receiver operating characteristic (ROC) curve analysis were performed with surgical pathologic examination as the reference standard.

RESULTS

The only finding that differentiated the two groups was the presence of a well-defined mass, favoring the diagnosis of cancer (p = 0.02, p < 0.01). There was no significant difference between the two groups in signal intensity on DW images (p = 0.82, p = 0.85) or ADC (p = 0.51, p = 0.76). Double-duct sign, pancreatic duct cutoff, and perivascular soft-tissue cuffing were not useful in differentiating the two groups. The areas under the ROC curve were 0.873 and 0.878 for the conventional MRI scores, compared with 0.602 and 0.552 for ADC measurements (p = 0.02, p = 0.008).

CONCLUSION

The addition of DWI to conventional MRI does not facilitate differentiation of pancreatic cancer from chronic pancreatitis.

Pain and chronic pancreatitis: A complex interplay of multiple mechanisms

Despite multiple theories on the pathogenesis of pain in chronic pancreatitis, no uniform and consistently successful treatment strategy exists and abdominal pain still remains the dominating symptom for most patients and a major challenge for clinicians. Traditional theories focussed on a mechanical cause of pain related to anatomical changes and evidence of increased ductal and interstitial pressures. These observations form the basis for surgical and endoscopic drainage procedures, but the outcome is variable and often unsatisfactory. This underscores the fact that other factors must contribute to pathogenesis of pain, and has shifted the focus towards a more complex neurobiological understanding of pain generation. Amongst other explanations for pain, experimental and human studies have provided evidence that pain perception at the peripheral level and central pain processing of the nociceptive information is altered in patients with chronic pancreatitis, and resembles that seen in neuropathic and chronic pain disorders. However, pain due to e.g., complications to the disease and adverse effects to treatment must not be overlooked as an additional source of pain. This review outlines the current theories on pain generation in chronic pancreatitis which is crucial in order to understand the complexity and limitations of current therapeutic approaches. Furthermore, it may also serve as an inspiration for further research and development of methods that can evaluate the relative contribution and interplay of different pain mechanisms in the individual patients, before they are subjected to more or less empirical treatment.

Morphological and functional evaluation of chronic pancreatitis with magnetic resonance imaging

Magnetic resonance imaging (MRI) techniques for assessment of morphology and function of the pancreas have been improved dramatically the recent years and MRI is very often used in diagnosing and follow-up of chronic pancreatitis (CP) patients. Standard MRI including fat-suppressed T1-weighted and T2-weighted imaging techniques reveal decreased signal and glandular atrophy of the pancreas in CP. In contrast-enhanced MRI of the pancreas in CP the pancreatic signal is usually reduced and delayed due to decreased perfusion as a result of chronic inflammation and fibrosis. Thus, morphological changes of the ductal system can be assessed by magnetic resonance cholangiopancreatography (MRCP). Furthermore, secretin-stimulated MRCP is a valuable technique to evaluate side branch pathology and the exocrine function of the pancreas and diffusion weighted imaging can be used to quantify both parenchymal fibrotic changes and the exocrine function of the pancreas. These standard and advanced MRI techniques are supplementary techniques to reveal morphological and functional changes of the pancreas in CP. Recently, spectroscopy has been used for assessment of metabolite concentrations in-vivo in different tissues and may have the potential to offer better tissue characterization of the pancreas. Hence, the purpose of the present review is to provide an update on standard and advanced MRI techniques of the pancreas in CP.

Fibrosis, atrophy, and ductal pathology in chronic pancreatitis are associated with pancreatic function but independent of symptoms

OBJECTIVES

More knowledge into the pathophysiology underlying pain and other complications in chronic pancreatitis (CP) is needed. The aim was to associate advanced imaging information of the pancreas with etiology and clinical and laboratory parameters of CP.

METHODS

Magnetic resonance cholangiopancreatography including diffusion-weighted imaging was obtained in 23 patients with painful CP and 17 controls. Apparent diffusion coefficients, ductal pathology, and pancreas atrophy were assessed. Etiology of CP and clinical and laboratory parameters including pain scores were correlated with the imaging findings.

RESULTS

The patients had restricted apparent diffusion coefficients, that is, fibrotic changes, compared with the controls (P = 0.0003). The diffusion coefficients were not associated with atrophy- or ductal-related parameters (all P > 0.7). The fibrotic changes as well as atrophy- and ductal-related parameters were not associated with pain or any other symptom parameters (all P > 0.05). Alcoholic etiology was associated with ductal pathology (both P = 0.02). Furthermore, atrophy- and ductal-related parameters were associated with vitamin D, phosphate, hemoglobin, and glycated hemoglobin levels (all P < 0.03).

CONCLUSIONS

Patients with CP have fibrosis, atrophy, and ductal pathology. Although changes in atrophy- and ductal-related parameters were, to some degree, associated with exocrine and endocrine insufficiency, pain and other symptoms seem to have a more complex pathogenesis independent of imaging pathology.

Multimodality imaging of pancreatic cancer-computed tomography, magnetic resonance imaging, and positron emission tomography

Pancreatic adenocarcinoma continues to have a dismal prognosis, with curative surgery (resection with negative margins) possible in only a small percentage of patients. Not only does radiological imaging play a major role in diagnosing the primary lesion at presentation, but it is also crucial for staging of locoregional disease and distant metastases, both of which are critical for selecting appropriate candidates for surgery. Over the last 2 decades, computed tomography has become the dominant imaging modality for both the diagnosis and staging of pancreatic cancer, with advances in multidetector computed tomography technology improving the ability to identify small tumors and demonstrate subtle degrees of vascular involvement by tumor. However, magnetic resonance imaging and positron emission tomography are now playing an increasing role in pancreatic cancer imaging. These 3 imaging modalities each have specific strengths and benefits and should be used in a complementary fashion.

Diffusion-weighted MRI of the abdomen: current value in clinical routine

Magnetic resonance imaging (MRI) provides high tissue contrast without ionizing radiation exposure and unenhanced images are often diagnostic. Therefore, MRI is especially an attractive tool for patients with allergies for gadolinium-based contrast agents or renal failure. Technical advantages have led to the increasing use of diffusion-weighted (DW) MRI in abdominal imaging, which provides qualitative and quantitative information of tissue cellularity and the integrity of cellular membranes. This review article presents the current status of noncontrast MRI with the focus of DW-MRI. Technical background and clinical applications are explained and discussed.

MRI of the pancreas: problem solving tool

Advances in MR hardware and pulse sequence design over the years have improved the quality and robustness of MR imaging of the pancreas. Today, MRI is an indispensible tool for studying the pancreas and can provide useful information not attainable with other noninvasive or minimally invasive imaging techniques. In the present review, specific cases are reviewed where the strengths of MRI demonstrate the utility of this imaging modality as a problem solving tool.

Added value of diffusion-weighted imaging to MR cholangiopancreatography with unenhanced mr imaging for predicting malignancy or invasiveness of intraductal papillary mucinous neoplasm of the pancreas

PURPOSE

To investigate the added value of diffusion-weighted imaging (DWI) to magnetic resonance cholangiopancreatography (MRCP) with unenhanced MR imaging for predicting the malignancy or invasiveness of intraductal papillary mucinous neoplasms (IPMNs).

MATERIALS AND METHODS

Following Institutional Review Board (IRB) approval, this retrospective study included 52 patients with surgically resected IPMNs and who underwent MRCP, unenhanced MRI, and DWI. Three blinded radiologists evaluated the two image sets, ie, MRCP with unenhanced MR images vs. the combined set with MRCP, unenhanced MR images, and DWI, and scored their confidence for malignancy or for invasiveness of IPMNs. The mean apparent diffusion coefficient (ADC) values of benign IPMNs and of intraductal mucinous carcinomas (IPMCs) were compared. The diagnostic accuracy was calculated using receiver operating characteristic (ROC) curve analysis.

RESULTS

The mean ADC of malignant IPMNs (2.05 ± 0.66 × 10(-3) mm(2) /sec) was significantly lower than that of benign IPMNs (2.95 ± 0.32 × 10(-3) mm(2) /sec, P < 0.0001). Invasive IPMCs (1.51 ± 0.32 × 10(-3) mm(2) /sec) showed significantly lower ADC than that of noninvasive IPMCs (2.67 ± 0.23 × 10(-3) mm(2) /sec, P = 0.0003). The area of diffusion restriction was more frequently seen in malignant IPMNs than in benign IPMNs (P < 0.00001). The addition of DWI to MRCP with unenhanced MRI did not show a significant improvement for predicting malignant IPMN (P> 0.05), but resulted in a tendency to improve the diagnostic accuracy for the prediction of invasive IPMN in two observers (P = 0.072, P = 0.085).

CONCLUSION

The addition of DWI to MRCP with unenhanced MRI may improve the diagnosis of malignant IPMN and further increase the prediction of invasive IPMC.

Update of exocrine functional diagnostics in chronic pancreatitis

Diagnostics of pancreatic insufficiency rely mainly on tests of pancreatic exocrine function based on either measurement of pancreatic secretion or the secondary effects resulting from lack of digestive enzymes or imaging modalities. These methods have been developing rapidly over the last decades, and the aims of this review were to describe exocrine functional testing and imaging of the pancreas in chronic pancreatitis..

Differentiation of an intrapancreatic accessory spleen from a small (<3-cm) solid pancreatic tumor: value of diffusion-weighted MR imaging

PURPOSE

To evaluate the value of diffusion-weighted (DW) imaging in differentiation of an intrapancreatic accessory spleen (IPAS) from a small (<3 cm) solid pancreatic tumor.

MATERIALS AND METHODS

This retrospective study was approved by the institutional review board, and informed consent was waived. Twenty patients with IPAS and 22 patients with small solid pancreatic tumors were included. All patients underwent abdominal magnetic resonance (MR) imaging with DW and gadoxetic acid-enhanced imaging. Qualitative (signal intensity) and quantitative (signal intensity and apparent diffusion coefficient [ADC]) evaluations were performed by two observers. Fisher exact test and Mann-Whitney U test were used for comparing groups.

RESULTS

Compared with the spleen, the IPAS showed isointensity more frequently than did small pancreatic tumors on T2-weighted images (95% [19 of 20] vs 41% [nine of 22]), arterial phase images (100% [20 of 20] vs 18% [four of 22]), portal phase images (100% [20 of 20] vs 23% [five of 22]), late phase images (100% [20 of 20] vs 41% [nine of 22]), and DW images with b value of 0 sec/mm(2) (100% [20 of 20] vs 9% [two of 22]), b value of 100 sec/mm(2) (95% [19 of 20] vs 27% [six of 22]), and b value of 800 sec/mm(2) (100% [20 of 20] vs 27% [six of 22]), with significant differences (P < .01). The means of the absolute value of relative signal intensity and ADC ratio on DW images of IPAS were significantly lower and closer to zero than those of pancreatic tumors (P < .05). Visual assessment of the similarity between pancreatic lesion and spleen on DW images for diagnosis of IPAS yielded diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of 95% (40 of 42), 100% (20 of 20), 91% (20 of 22), 91% (20 of 22), and 100% (20 of 20), respectively, for observer 1 and 90% (38 of 42), 95% (19 of 20), 86% (19 of 22), 86% (19 of 22), and 95% (19of 20), respectively, for observer 2.

CONCLUSION

In addition to conventional morphologic MR imaging, DW imaging can be used as a tool for differentiating IPAS from solid pancreatic tumors.

SUPPLEMENTAL MATERIAL

http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12112765/-/DC1.

Diffusion-weighted imaging of the healthy pancreas: ADC values are age and gender dependent

PURPOSE

To investigate the healthy pancreas with diffusion-weighted imaging (DWI) for characterization of age and gender-related differences in apparent diffusion coefficient (ADC) values.

MATERIALS AND METHODS

Sixty six volunteers were prospectively enrolled (33 male, 33 female; range 1.4 to 83.7 years of age) and echo-planar DWI of the pancreas was performed. ADC values were measured in the pancreas head, body, and tail using a pixel-by-pixel approach. Effects of age and gender on ADC values were analyzed using a two-factorial multivariate analysis of variance (MANOVA).

RESULTS

ADC values correlated inversely with the age of the volunteers. The mean global pancreatic ADC values (× 10(-3) mm(2)/s) in the age groups 0-20 years, 21-40 years, and > 40 years were 1.18 ± 0.19, 1.07 ± 0.13, and 0.99 ± 0.18, respectively. Female individuals had higher mean global ADC values than male (1.13 ± 0.14 versus 1.02 ± 0.18 × 10(-3) mm(2)/s). MANOVA showed significant effects of age (P value 0.022, eta(2) = 0.13) and gender (P value 0.001, eta(2) = 0.28) on ADC values.

CONCLUSION

Pancreatic ADC values decline with ageing and show significant gender differences with higher mean values in females. The awareness of baseline values adjusted to age and gender will be important for correct interpretation of individual cases and design of future studies.

The role of pancreatic imaging in monogenic diabetes mellitus

In neonatal diabetes mellitus resulting from mutations in EIF2AK3, PTF1A, HNF1B, PDX1 or RFX6, pancreatic aplasia or hypoplasia is typical. In maturity-onset diabetes mellitus of the young (MODY), mutations in HNF1B result in aplasia of pancreatic body and tail, and mutations in CEL lead to lipomatosis. The pancreas is not readily accessible for histopathological investigations and pancreatic imaging might, therefore, prove important for diagnosis, treatment, and research into these β-cell diseases. Advanced imaging techniques can identify the pancreatic features that are characteristic of inherited diabetes subtypes, including alterations in organ size (diffuse atrophy and complete or partial pancreatic agenesis), lipomatosis and calcifications. Consequently, in patients with suspected monogenic diabetes mellitus, the results of pancreatic imaging could help guide the molecular and genetic investigation. Imaging findings also highlight the critical roles of specific genes in normal pancreatic development and differentiation and provide new insight into alterations in pancreatic structure that are relevant for β-cell disease.

Usefulness of diffusion-weighted imaging of breast tumors: quantitative and visual assessment

PURPOSE

We evaluated the usefulness of quantitative and visual assessment of diffusion-weighted imaging (DWI) of breast tumors to distinguish malignant from benign tumors.

MATERIALS AND METHODS

The DWI findings of 106 breast lesions (15 benign, 91 malignant) were retrospectively analyzed. The mean apparent diffusion coefficient (ADC) value for each lesion was calculated using b values of 250, 500, 750, and 1000 s/mm(2) as a quantitative assessment. We visually evaluated the signal intensity of each breast lesion on the basis of a spinal signal intensity in DWI (b = 1000 s/mm(2)) and compared the mean ADC values using a threshold mean ADC +1.65 × standard deviation (SD) for malignant and benign breast lesions. Obviously strong signal intensity of the lesion relative to that of the spinal cord on DWI signifies malignancy.

RESULTS

The mean ADC value for benign lesions (1.50 ± 0.38 × 10(-3) mm(2)/s) was significantly higher than that for malignant lesions (0.98 ± 0.19 × 10(-3) mm(2)/s), with 94.5% sensitivity, 80% specificity, and 92.5% accuracy. Sensitivity for visual assessment was 91.5%, specificity was 33.3%, and total accuracy was 82.5%.

CONCLUSION

ADC values, but not visual assessment, may be useful for differentiating benign and malignant breast tumors.

Diffusion-weighted magnetic resonance imaging in the upper abdomen: technical issues and clinical applications

Recent technological achievements have enabled the transposition of diffusion-weighted imaging (DWI) with good diagnostic quality into other body regions, especially the abdomen and pelvis. Many emerging and established applications are now being evaluated on the upper abdomen, the liver being the most studied organ. This article discusses imaging strategies for DWI on the upper abdomen, describes the clinical protocol, and reviews the most common clinical applications of DWI on solid abdominal organs.

Chronic pancreatitis

Chronic pancreatitis is a progressive fibroinflammatory disease that exists in large-duct (often with intraductal calculi) or small-duct form. In many patients this disease results from a complex mix of environmental (eg, alcohol, cigarettes, and occupational chemicals) and genetic factors (eg, mutation in a trypsin-controlling gene or the cystic fibrosis transmembrane conductance regulator); a few patients have hereditary or autoimmune disease. Pain in the form of recurrent attacks of pancreatitis (representing paralysis of apical exocytosis in acinar cells) or constant and disabling pain is usually the main symptom. Management of the pain is mainly empirical, involving potent analgesics, duct drainage by endoscopic or surgical means, and partial or total pancreatectomy. However, steroids rapidly reduce symptoms in patients with autoimmune pancreatitis, and micronutrient therapy to correct electrophilic stress is emerging as a promising treatment in the other patients. Steatorrhoea, diabetes, local complications, and psychosocial issues associated with the disease are additional therapeutic challenges.

Enhancing pancreatic adenocarcinoma delineation in diffusion derived intravoxel incoherent motion f-maps through automatic vessel and duct segmentation

Diffusion-based intravoxel incoherent motion imaging has recently gained interest as a method to detect and characterize pancreatic lesions, especially as it could provide a radiation- and contrast agent-free alternative to existing diagnostic methods. However, tumor delineation on intravoxel incoherent motion-derived parameter maps is impeded by poor lesion-to-pancreatic duct contrast in the f-maps and poor lesion-to-vessel contrast in the D-maps. The distribution of the diffusion and perfusion parameters within vessels, ducts, and tumors were extracted from a group of 42 patients with pancreatic adenocarcinoma. Clearly separable combinations of f and D were observed, and receiver operating characteristic analysis was used to determine the optimal cutoff values for an automated segmentation of vessels and ducts to improve lesion detection and delineation on the individual intravoxel incoherent motion-derived maps. Receiver operating characteristic analysis identified f = 0.28 as the cutoff for vessels (Area under the curve (AUC) = 0.901) versus tumor/duct and D = 1.85 μm(2) /ms for separating duct from tumor tissue (AUC = 0.988). These values were incorporated in an automatic segmentation algorithm and then applied to 42 patients. This yielded clearly improved tumor delineation compared to individual intravoxel incoherent motion-derived maps. Furthermore, previous findings that indicated that the f value in pancreatic cancer is strongly reduced compared to healthy pancreatic tissue were reconfirmed.

Abdominal magnetic resonance imaging at 3 T: oncological applications

The gain in signal-to-noise ratio at 3 T magnetic resonance (MR) imaging produces many benefits for abdominal imaging applications, including the capability to reduce acquisition times and/or improve spatial resolution for a variety of pulse sequences, the potential for broader application of parallel imaging techniques, and an increased sensitivity to gadolinium-based contrast media. These advances have the potential of improving the accuracy of MR imaging in the detection, staging, treatment planning, and follow-up of patients with abdominal tumors. At the same time, because certain high-field-strength-related drawbacks could not be compensated for, abdominal 3 T MR imaging should be clinically implemented with caution in some patients (eg, patients with massive ascites).