Differentiation between pancreatic carcinoma and mass-forming chronic pancreatitis: usefulness of high b value diffusion-weighted imaging

Quantitative MR imaging biomarkers for distinguishing inflammatory pancreatic mass and pancreatic cancer-a systematic review and meta-analysis

OBJECTIVES

To evaluate the diagnostic performance of quantitative magnetic resonance (MR) imaging biomarkers in distinguishing between inflammatory pancreatic masses (IPM) and pancreatic cancer (PC).

METHODS

A literature search was conducted using PubMed, Embase, the Cochrane Library, and Web of Science through August 2023. Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) was used to evaluate the risk of bias and applicability of the studies. The pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio were calculated using the DerSimonian-Laird method. Univariate meta-regression analysis was used to identify the potential factors of heterogeneity.

RESULTS

Twenty-four studies were included in this meta-analysis. The two main types of IPM, mass-forming pancreatitis (MFP) and autoimmune pancreatitis (AIP), differ in their apparent diffusion coefficient (ADC) values. Compared with PC, the ADC value was higher in MFP but lower in AIP. The pooled sensitivity/specificity of ADC were 0.80/0.85 for distinguishing MFP from PC and 0.82/0.84 for distinguishing AIP from PC. The pooled sensitivity/specificity for the maximal diameter of the upstream main pancreatic duct (dMPD) was 0.86/0.74, with a cutoff of dMPD ≤ 4 mm, and 0.97/0.52, with a cutoff of dMPD ≤ 5 mm. The pooled sensitivity/specificity for perfusion fraction (f) was 0.82/0.68, and 0.82/0.77 for mass stiffness values.

CONCLUSIONS

Quantitative MR imaging biomarkers are useful in distinguishing between IPM and PC. ADC values differ between MFP and AIP, and they should be separated for consideration in future studies.

CLINICAL RELEVANCE STATEMENT

Quantitative MR parameters could serve as non-invasive imaging biomarkers for differentiating malignant pancreatic neoplasms from inflammatory masses of the pancreas, and hence help to avoid unnecessary surgery.

KEY POINTS

• Several quantitative MR imaging biomarkers performed well in differential diagnosis between inflammatory pancreatic mass and pancreatic cancer. • The ADC value could discern pancreatic cancer from mass-forming pancreatitis or autoimmune pancreatitis, if the two inflammatory mass types are not combined. • The diameter of main pancreatic duct had the highest specificity for differentiating autoimmune pancreatitis from pancreatic cancer.

Utility of MRI in detection of PET-CT proven local recurrence of pancreatic adenocarcinoma after surgery

The aim of this prospective study was to investigate the accuracy and inter-observer reliability of MRI in detection of local recurrence (LR) of pancreatic adenocarcinoma (PAC) after surgery, which was proved by PET-CT and access correlation between functional MRI and PET parameters. Forty-five patients who underwent PET-CT and MRI for follow-up purposes after radical operation of PAC were included. Twenty-three were PET positive (study group) and 22 negative for LR (control group). MR examination was performed within one month after PET-CT and three readers who were blind for PET-CT findings searched LR in T2W, 3D-dynamic post-contrast T1W-FS and DWI sequences, respectively. Sensitivity and specificity were calculated while inter-reader agreement was estimated by Cronbach's Alpha reliability coefficient (CARC). Apparent diffusion coefficient (ADC) of LR was correlated with the size (maximal diameter) and functional PET-CT parameters: mean and maximum standardized uptake values (SUVmean, SUVmax), metabolic tumor volume (MTV) and total lesion glycolysis (TLG), using Spearman's correlation coefficient (rS). Sensitivity and specificity among three readers in detecting the LR were 70% and 77-84% in T2W (CARC 0.806), 91-100% and 100% in 3D post-contrast T1W-FS (CARC 0.980), and both 100% in DWI sequences (CARC 1.000). Moderate inverse correlation was found between the ADC and SUVmean (rS = - 0.484), MTV (rS = - 0.494), TLG (rS = - 0.519) and lesion size (rS = - 0.567). MRI with DWI shows high diagnostic accuracy in detecting the LR of PAC in comparison to PET-CT as reference standard. ADC significantly inversely correlates with standard and advanced PET parameters and size of LR.

MRI features for differentiation of autoimmune pancreatitis from pancreatic ductal adenocarcinoma: A systematic review and meta-analysis

BACKGROUND AND AIMS

The accurate differential diagnosis between autoimmune pancreatitis (AIP) and pancreatic ductal adenocarcinoma (PDAC) is clinically important. We aimed to determine significant MRI features for differentiating AIP from PDAC, including assessment of diffusion-weighted imaging (DWI).

METHODS

We performed a systematic search using three databases. The pooled diagnostic odds ratio was calculated using a bivariate random effects model to determine significant MRI features for differentiating AIP from PDAC. The pooled sensitivity and specificity were calculated. The qualitative systematic review for DWI assessment was performed.

RESULTS

Of nine studies (775 patients), multiple main pancreatic duct (MPD) strictures, absence of upstream marked MPD dilatation, peripancreatic rim, and duct penetration sign were significant MRI features for differentiating AIP from PDAC. Absence of MPD dilatation had the highest pooled sensitivity (87%, 95% CI=68-96%), whereas peripancreatic rim had the highest pooled specificity (100%, 95% CI=88-100%). Of 12 studies evaluating DWI, seven reported statistically significant differences in apparent diffusion coefficient (ADC) values between AIP and PDAC; however, four reported lower ADC values in AIP than in PDAC, but three reported the opposite result.

CONCLUSION

The four significant MRI features can be useful to differentiate AIP from PDAC, but DWI assessment might be limited.

Development and validation of a novel model incorporating MRI-based radiomics signature with clinical biomarkers for distinguishing pancreatic carcinoma from mass-forming chronic pancreatitis

•

A novel model incorporating multiparametric MRI-based radiomic signature with clinically independent risk factors can greatly improve the non-invasive diagnostic accuracy in differentiating PC from MFCP.

•

The nomogram integrating rad-score and clinically independent risk factors had a better diagnostic performance than the mp-MRI and clinical models.

•

The mixed model may aid in formulating treatment strategies and help to avoid unnecessary surgical operations for doctors.

Purpose

It is difficult to make a clear differential diagnosis of pancreatic carcinoma (PC) and mass-forming chronic pancreatitis (MFCP) via conventional examinations. We aimed to develop a novel model incorporating an MRI-based radiomics signature with clinical biomarkers for distinguishing the two lesions.

Methods

A total of 102 patients were retrospectively enrolled and randomly divided into the training and validation cohorts. Radiomics features were extracted from four different sequences. Individual imaging modality radiomics signature, multiparametric MRI (mp-MRI) radiomics signature, and a final mixed model based on mp-MRI and clinically independent risk factors were established to discriminate between PC and MFCP. The diagnostic performance of each model and model discrimination were assessed in both the training and validation cohorts.

Results

ADC had the best predictive performance among the four individual radiomics models, but there were no significant differences between the pairs of models (all p > 0.05). Six potential radiomics features were finally selected from the 960 texture features to formulate the radiomics score (rad-score) of the mp-MRI model. In addition, the boxplot results of the distributions of rad-scores identified the rad-score as an independent predictive factor for the differentiation of PC and MFCP (p< 0.001). Notably, the nomogram integrating rad-score and clinically independent risk factors had a better diagnostic performance than the mp-MRI and clinical models. These results were further confirmed by the validation group.

Conclusion

The mixed model was developed and preliminarily validated to distinguish PC from MFCP, which may benefit the formulation of treatment strategies and nonsurgical procedures.

Role of diffusion-weighted MRI in diagnosis and post therapeutic follow-up of colorectal cancer

Background

The colorectal cancer (CRC) is one of the deadliest cancers in the world. Local tumor stage, vascular or lymphatic invasion, and tumor grade are essential for accurate management. The main imaging modality for initial assessment and therapeutic response evaluation of CRC is magnetic resonance imaging (MRI). The purpose of this prospective study was to illustrate the role of diffusion-weighted MRI (DWI) and apparent diffusion coefficient (ADC) value in initial assessment and grading of colorectal carcinoma as well as evaluation of its response to chemotherapy or combined chemoradiation.

Results

Restricted diffusion in DWI was found in 37 out of 40 patients with sensitivity of about 92.5%. In the studied group, the median ADC value was 1.21 (min 0.80, max 1.31) and the average ADC value was 1.14 ± 0.161. The mean ADC value in poorly differentiated tumors was 0.979 × 10−3mm2/s. The mean ADC value in moderately differentiated tumors was 1.112 × 10−3mm2/s. The mean ADC value in well-differentiated tumors was 1.273 × 10−3mm2/s. The sensitivity, specificity, PPV, NPV, and accuracy were higher with addition of DWI and ADC value to conventional MRI reaching 100%, 80%, 83.3%, 100%, and 90%, respectively.

Conclusion

Adding DW imaging with ADC value to conventional MRI yields better diagnostic accuracy than using conventional MR imaging alone in detection, correlation with tumor histologic grade, initial staging, and response evaluation to neoadjuvant chemoradiotherapy in patients with locally advanced colorectal cancer.

Qualitative and Quantitative Comparison of Respiratory Triggered Reduced Field-of-View (FOV) Versus Full FOV Diffusion Weighted Imaging (DWI) in Pancreatic Pathologies

RATIONALE AND OBJECTIVES

To investigate the effects of a reduced field-of-view (rFOV) acquisition in diffusion-weighted magnetic resonance imaging of the pancreas.

MATERIALS AND METHODS

We enrolled 153 patients who underwent routine clinical MRI work-up including respiratory-triggered diffusion-weighted single-shot echo-planar imaging (DWI) with full field-of-view (fFOV, 3 × 3 × 4 mm³ voxel size) and reduced field-of-view (rFOV, 2.5 × 2.5 × 3 mm³ voxel size) for suspected pancreatic pathology. Two experienced radiologists were asked to subjectively rate (Likert Scale 1-4) image quality (overall image quality, lesion conspicuity, anatomical detail, artifacts). In addition, quantitative image parameters were assessed (apparent diffusion coefficient, apparent signal to noise ratio, apparent contrast to noise ratio [CNR]).

RESULTS

All subjective metrics of image quality were rated in favor of rFOV DWI images compared to fFOV DWI images with substantial-to-high inter-rater reliability. Calculated ADC values of normal pancreas, pancreatic pathologies and reference tissues revealed no differences between both sequences. Whereas the apparent signal to noise ratio was higher in fFOV images, apparent CNR was higher in rFOV images.

CONCLUSION

rFOV DWI provides higher image quality and apparent CNR values, favorable in the analysis of pancreatic pathologies.

Accuracy of quantitative diffusion-weighted imaging for differentiating benign and malignant pancreatic lesions: a systematic review and meta-analysis

BACKGROUND

A variety of imaging techniques can be used to evaluate diffusion characteristics to differentiate malignant and benign pancreatic lesions. The diagnostic performance of diffusion parameters has not been systematic assessed.

PURPOSE

We aimed to investigate the diagnostic efficacy of quantitative diffusion-weighted imaging (DWI) for pancreatic lesions.

METHODS

A literature search was conducted using the PubMed, Embase, and Cochrane Library databases for studies from inception to March 30, 2020, which involves the quantitative diagnostic performance of diffusion-weighted imaging (DWI) and intravoxel incoherent motion (IVIM) in the pancreas. Studies were reviewed according to inclusion and exclusion criteria. The quality of articles was evaluated by the Quality Assessment of Diagnostic Accuracy Studies-2 (QUATAS-2). A bivariate random-effects model was used to evaluate pooled sensitivities and specificities. Univariable meta-regression analysis was used to test the effects of factors that contributed to the heterogeneity.

RESULTS

A total of 31 studies involving 1558 patients were ultimately eligible for data extraction. The lowest heterogeneity was found in specificity of perfusion fraction (f) with the I² value was 17.97% and Cochran p value was 0.28. However, high heterogeneities were found for the other parameters (all I² > 50%). There was no publication bias found in funnel plot (p = 0.30) for the apparent diffusion coefficient (ADC) parameter. The pooled sensitivities for ADC, f, pure diffusion coefficient (D), and pseudo diffusivity coefficient (D*) were 83%, 81%, 76%, and 84%, respectively. The pooled specificities for ADC, f, D, and D* were 87%, 83%, 69%, and 81% respectively. The areas under the curves for ADC, f, D, and D* were 0.92, 0.87, 0.79, and 0.87 respectively.

CONCLUSION

Quantitative DWI and IVIM have a good diagnostic performance for differentiating malignant and benign pancreatic lesions.

KEY POINTS

• IVIM has high sensitivity and specificity (84% and 83%, respectively) for differential diagnosis of pancreatic lesions, which is comparable to that of the ADC (83% and 87%, respectively). • The ADC has an excellent diagnostic performance for differentiating malignant from benign IPMNs (sensitivity, 0.83; specificity, 0.92); the f has the best diagnostic performance for differentiating pancreatic carcinoma from PNET (sensitivity, 0.85; specificity, 0.85). • For the ADC, using a maximal b value < 800 s/mm² has a higher diagnostic accuracy than ≥ 800 s/mm²; performing in a high field strength (3.0 T) system has a higher diagnostic accuracy than a low field strength (1.5 T) for pancreatic lesions.

Diagnostic performance of diffusion MRI for pancreatic ductal adenocarcinoma characterisation: A meta-analysis

PURPOSE

To assess the diagnostic performance of intravoxel incoherent motion (IVIM) and diffusion-weighted imaging (DWI) for characterising pancreatic ductal adenocarcinoma (PDAC).

METHOD

A literature search was performed through PubMed, Web of Science, the Cochrane Library, and Embase databases. The search date was updated to extend until 28 October 2020, with no starting time limitation. The pooled sensitivity and specificity were calculated using a bivariate random effects model. Summary receiver operating characteristic curves were constructed, and area under the curve (AUC) of each diffusion parameter was calculated. Subgroup and meta-regression analyses were performed to assess for heterogeneity. Study quality was assessed.

RESULTS

Twenty-nine studies involving 1579 participants were included, of which 26 evaluated the apparent diffusion coefficient (ADC) and eight evaluated IVIM, with five evaluating both ADC and IVIM. Pooled sensitivity and specificity of ADC were 83 % (95 % CI, 76 %-88 %, I² = 86 %) and 85 % (95 % CI, 79 %-90 %, I² = 77 %), respectively, and AUC was 0.91 (95 % CI, 0.88-0.93). The perfusion fraction had the highest diagnostic accuracy in the IVIM model; the pooled sensitivity, specificity, and AUC were 87 % (95 % CI, 81 %-92 %, I² = 45 %), 88 % (95 % CI, 77 %-94 %, I² = 57 %), and 0.93 (95 % CI, 0.91-0.95), respectively. The pooled sensitivity, specificity and AUC for the tissue diffusion coefficient were 74 % (95 % CI, 55 %-87 %, I² = 87 %), 69 % (95 % CI, 52 %-82 %, I² = 73 %), and 0.77 (95 % CI, 0.73-0.81), respectively. And the pooled sensitivity, specificity, and AUC for the pseudodiffusion coefficient were 89 % (95 % CI, 77 %-96 %, I² = 79 %), 74 % (95 % CI, 60 %-84 %, I² = 78 %), and 0.88(95 %CI,0.85-0.91), respectively. Meta-regression analyses revealed that study design (specificity, P＜0.01), region-of-interest delineation (sensitivity, P = 0.02;specificity, P = 0.03), field strength (sensitivity, P＜0.01), and thickness (sensitivity, P＜0.01; specificity, P = 0.01) were sources of ADC heterogeneity.

CONCLUSIONS

DWI and IVIM have comparable diagnostic power and good diagnostic performance for characterising PDAC.

Pancreatitis and PDAC: association and differentiation

The discrimination of mass-forming chronic pancreatitis (MFCP) from pancreatic ductal adenocarcinoma (PDAC) is a central diagnostic dilemma. It is important to differentiate these entities since they have markedly different prognoses and management. Importantly, the appearance of these two entities significantly overlaps on a variety of imaging modalities. However, there are imaging features that may be suggestive of one entity more than the other. MFCP and PDAC may show different enhancement patterns on perfusion computed tomography (CT) and/or dynamic contrast-enhanced MRI (DCE-MRI). The duct-penetrating sign on magnetic resonance cholangiopancreatography (MRCP) is more often associated with MFCP, whereas abrupt cutoff with upstream dilatation of the main pancreatic duct and the double-duct sign (obstruction/cutoff of both the common bile duct and pancreatic duct) are more often associated with PDAC. Nevertheless, tissue sampling is the most reliable method to differentiate between these entities and is currently generally necessary for management.

Optimizing b-values for accurate depiction of pancreatic cancer with tumor-associated pancreatitis on computed diffusion-weighted imaging

PURPOSE

To determine the optimal b-value for accurate depiction of pancreatic cancer (PC) in patients with active tumor-associated pancreatitis (TAP), using computed diffusion-weighted imaging (cDWI) with a range of b-values up to 3000 s/mm².

METHODS

The study protocol was approved by the institutional review board. We retrospectively analyzed 34 consecutive PC cases with active TAP who underwent pancreatectomy without preoperative therapy. Four cDWI datasets with b-values of 1500-3000 s/mm² (cDWI₁₅₀₀-cDWI₃₀₀₀) were generated from the original DWI datasets with b-values of 0 and 1000 s/mm² obtained using a 3-T scanner. Two board-certified radiologists evaluated images qualitatively (tumor conspicuity and total image quality), and another two board-certified radiologists placed regions of interest for quantitative evaluations (apparent diffusion coefficient [ADC] values of both lesions, contrast ratio [CR] of PC to active TAP, and volume ratio [VR] of PC to surgical specimen).

RESULTS

As the b-value increased, tumor conspicuity improved significantly in cDWI₂₀₀₀ and cDWI₂₅₀₀ (P = 0.0121 and 0.0015, respectively), although total image quality decreased in all cDWIs compared with DWI₁₀₀₀ (P < 0.0001). Significantly lower ADC values were seen in PC (P < 0.0001). All cDWI groups showed positive correlation between the tumor conspicuity and ADC difference between PC and TAP. CR increased with the b-value, while VR decreased. Significant equivalence of VR to the surgical specimen was seen on cDWI₂₀₀₀ (P = 0.0031).

CONCLUSION

Accurate depiction of PC was optimal with cDWI₂₀₀₀ in the presence of active TAP.

Effect of region of interest on ADC and interobserver variability in thyroid nodules

BACKGROUND

To determine the effect of region of interest (ROI) on tumor's apparent diffusion coefficient (ADC) and interobserver variability in thyroid nodules.

METHODS

Thirty-three individuals with 45 pathologically-confirmed thyroid nodules were assessed by preoperative diffusion-weighted imaging (DWI) with b values of 0 and 400 s/mm², respectively. Two readers evaluated the ADC values of lesions based on three ROI techniques: whole-volume, single-slice and small solid-sample groups. Interobserver variability was analyzed for all ROI techniques, and the mean ADCs of benign and cancerous thyroid nodules were compared.

RESULTS

For the mean ADCs of non-cancerous thyroid nodules, average differences and limits of agreement (LOAs) between readers were 0.00 [- 0.17-0.17] × 10^- 3 mm²/s for whole-volume ROI (ICC = 0.967), 0.00 [- 0.26-0.26] × 10^- 3 mm²/s for single-slice ROI (ICC = 0.932) and - 0.02 [- 0.38-0.41] × 10^- 3 mm²/s for small solid-sample ROI (ICC = 0.823). For the mean ADCs of cancerous thyroid nodules, average differences and LOAs between readers were - 0.05 [- 0.23-0.13] × 10^- 3 mm²/s (ICC = 0.885), 0.01 [- 0.23-0.25] × 10^- 3 mm²/s (ICC = 0.839) and - 0.07 [- 0.52-0.39] × 10^- 3 mm²/s (ICC = 0.579) for the three ROI methods, respectively. The mean ADC values were more scattered in the small solid-sample ROI group in comparison with the whole-volume and single-slice groups, in noncancerous and cancerous specimens. Of all three ROI techniques, whole-volume ROI-determined ADC had the highest combined sensitivity (80.0%), specificity (88.3%) and Youden index (0.683), with a cut-off of 1.84 × 10^- 3 mm²/s.

CONCLUSIONS

The ROI method overtly affects ADC measurements in benign and cancerous thyroid nodules. Small solid-sample ROI yielded the worst interobserver variability of average ADC measurements.

The Challenge of Autoimmune Pancreatitis: A Portrayal From the Pediatric Perspective

Autoimmune pancreatitis (AIP) is a rare disorder characterized by prompt clinical response to corticosteroids. Lost tolerance to a variety of pancreatic antigens and subsequent development of autoantibodies are presumably involved in the initiation of AIP. Even pediatric patients have been reported with features of AIP, and awareness of this disorder is increasing among different clinicians. The terms lymphoplasmacytic sclerosing pancreatitis and idiopathic duct-centric pancreatitis refer to the different histologic patterns of AIP, named type 1 and type 2, respectively. A combination of serologic, radiologic, and histologic investigations is needed to assess diagnosis of AIP and rule out neoplastic disorders. In addition, type 1 AIP can be distinguished by raised levels of serum immunoglobulin G4 and should be considered as part of systemic immunoglobulin G4-related disease. Conversely, type 2 AIP is frequently reported in younger patients and has less clear immune-mediated pathogenetic mechanisms. The natural history of pediatric AIP is obscure, and the diagnostic usefulness of different autoimmune abnormalities found in adults with AIP is limited for children. Tips to manage pediatric patients with AIP have been recently drafted through a set of recommendation statements. This review describes the current data about AIP and the pathogenic contribution of specific autoantibodies expressly in the pediatric population.

Diagnosis and Detection of Pancreatic Cancer

Computed tomography is the first-line imaging modality for suspected pancreatic cancer. Magnetic resonance cholangiopancreatography is a second-line modality for suspected pancreatic cancer and is usually reserved for equivocal cases. Both computed tomography and MR are highly sensitive in the detection of pancreatic cancer, with up to 96% and 93.5% sensitivity, respectively. Computed tomography is superior to MR in the assessment of tumor resectability, with accuracy rates of up to 86.8% and 78.9%, respectively. Close attention to secondary signs of pancreatic cancer, such as pancreatic duct dilatation, abrupt pancreatic duct caliber change, and parenchymal atrophy, are critical in the diagnosis of pancreatic cancer. Emerging techniques such as radiomics and molecular imaging have the potential of identifying malignant precursors and lead to earlier disease diagnosis. The results of these promising techniques need to be validated in larger clinical studies.

Can diffusion-weighted imaging serve as a biomarker of fibrosis in pancreatic adenocarcinoma?

PURPOSE

To assess the relationship between diffusion-weighted imaging (DWI) and intravoxel incoherent motion (IVIM)-derived quantitative parameters (apparent diffusion coefficient [ADC], perfusion fraction [f], Dslow , diffusion coefficient [D], and Dfast , pseudodiffusion coefficient [D*]) and histopathology in pancreatic adenocarcinoma (PAC).

MATERIALS AND METHODS

Subjects with suspected surgically resectable PAC were prospectively enrolled in this Health Insurance Portability and Accountability Act (HIPAA)-compliant, Institutional Review Board-approved study. Imaging was performed at 1.5T with a respiratory-triggered echo planar DWI sequence using 10 b values. Two readers drew regions of interest (ROIs) over the tumor and adjacent nontumoral tissue. Monoexponential and biexponential fits were used to derive ADC2b , ADCall , f, D, and D*, which were compared to quantitative histopathology of fibrosis, mean vascular density, and cellularity. Two biexponential IVIM models were investigated and compared: 1) nonlinear least-square fitting based on the Levenberg-Marquardt algorithm, and 2) linear fit using a fixed D* (20 mm2 /s). Statistical analysis included Student's t-test, Pearson correlation (P < 0.05 was considered significant), intraclass correlation, and coefficients of variance.

RESULTS

Twenty subjects with PAC were included in the final cohort. Negative correlation between D and fibrosis (Reader 2: r = -0.57 P = 0.01; pooled P = -0.46, P = 0.04) was observed with a trend toward positive correlation between f and fibrosis (r = 0.44, P = 0.05). ADC2b was significantly lower in PAC with dense fibrosis than with loose fibrosis ADC2b (P = 0.03). Inter- and intrareader agreement was excellent for ADC, D, and f.

CONCLUSION

In PAC, D negatively correlates with fibrosis, with a trend toward positive correlation with f suggesting both perfusion and diffusion effects contribute to stromal desmoplasia. ADC2b is significantly lower in tumors with dense fibrosis and may serve as a biomarker of fibrosis architecture.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;46:393-402.

The role of magnetic resonance cholangiopancreatography and diffusion-weighted imaging for the differential diagnosis of obstructive biliary disorders

Background: Although endoscopic retrograde cholangiopancreatography (ERCP) is accepted as the gold standard, there is a place for magnetic resonance cholangiopancreatography (MRCP) and diffusion-weighted imaging (DWI) in the diagnosis of obstructive biliary disorders.Aim: To compare the findings of MRCP with ERCP in patients with obstructive biliary disorders and to investigate the diagnostic efficacy of MRCP combined with DWI.Study design: Retrospective, analytic, cross-sectional study.Methods: The MRCP images of 126 patients who underwent both MRCP and ERCP owing to biliary obstruction were reviewed. Nine patients were excluded because of incomplete diagnostic workup or a long period (>3 months) between MRCP and ERCP. Ninety-two patients underwent DWI, which was also evaluated. The sensitivity, specificity and accuracy of MRCP and DWI were analysed.Results: The sensitivity, specificity and accuracy of MRCP according to ERCP results as the gold standard was 97%, 71% and 93% for assessment of biliary dilatation; 100%, 94.7% and 97.5% for the diagnosis of choledocholithiasis; 93.7%, 100% and 99% for the identification of benign strictures; 100%, 100% and 100% for the diagnosis of malignant tumours; and 100%, 100% and 100% for the detection of complicated hydatid cysts; respectively. The sensitivity and specificity of DWI for the diagnosis of malignant tumour was 100%. In the detection of choledocholithiasis, the sensitivity and specificity of DWI was 70.8% and 100%.Conclusions: MRCP is an alternative, non-invasive, diagnostic modality, comparable with ERCP for the evaluation of pancreaticobiliary diseases. DWI can be helpful for diagnosis of choledocholithiasis and tumours.

Optimized ROI size on ADC measurements of normal pancreas, pancreatic cancer and mass-forming chronic pancreatitis

Objectives

To investigate the effects of region of interest (ROI) sizes on apparent diffusion coefficient (ADC) measurements for the differentiation of normal pancreas (NP), pancreatic ductal adenocarcinoma (PDAC) and mass-forming chronic pancreatitis (MFCP).

Results

There were no significant differences for the mean ADCs measured by 12 different-size ROIs for MFCP, or PDAC and NP (P = 0.858–1.0). With the increase of ROI size (≥ 55 mm²), ADCs of PDAC were significantly lower than those of NP (all P < 0.05), but there was no difference of the accuracy in ADC for differentiating the two groups only at a ROI size of 214 mm². When ROI size was above 99 mm², ADCs of MFCP were significantly lower than those of NP (all P < 0.05). There were no significant differences for any of the mean ADCs measured by 12 different-size ROIs between PDAC and MFCP (P > 0.05).

Materials and Methods

Diffusion-weighted imaging (DWI) was performed on 89 participants: 64 with PDAC, 7 with MFCP, as well as 18 healthy volunteers. ADC maps were created using mono-exponential model. A homemade software was used to measure the mean ADC values of 12 concentric round ROIs (areas: 15, 46, 55, 82, 99, 121, 134, 152, 161, 189, 214, 223, and 245 mm²) for the mass of lesions and the NP tissue.

Conclusions

In ADC measurements, the optimized ROI size is 214 mm² for the differentiation of PDAC and NP; ROI size of ≥ 99 mm² is recommended to differentiate between MFCP and NP. ADC was not useful for the differentiation of PDAC and MFCP.

Imaging modalities for characterising focal pancreatic lesions

BACKGROUND

Increasing numbers of incidental pancreatic lesions are being detected each year. Accurate characterisation of pancreatic lesions into benign, precancerous, and cancer masses is crucial in deciding whether to use treatment or surveillance. Distinguishing benign lesions from precancerous and cancerous lesions can prevent patients from undergoing unnecessary major surgery. Despite the importance of accurately classifying pancreatic lesions, there is no clear algorithm for management of focal pancreatic lesions.

OBJECTIVES

To determine and compare the diagnostic accuracy of various imaging modalities in detecting cancerous and precancerous lesions in people with focal pancreatic lesions.

SEARCH METHODS

We searched the CENTRAL, MEDLINE, Embase, and Science Citation Index until 19 July 2016. We searched the references of included studies to identify further studies. We did not restrict studies based on language or publication status, or whether data were collected prospectively or retrospectively.

SELECTION CRITERIA

We planned to include studies reporting cross-sectional information on the index test (CT (computed tomography), MRI (magnetic resonance imaging), PET (positron emission tomography), EUS (endoscopic ultrasound), EUS elastography, and EUS-guided biopsy or FNA (fine-needle aspiration)) and reference standard (confirmation of the nature of the lesion was obtained by histopathological examination of the entire lesion by surgical excision, or histopathological examination for confirmation of precancer or cancer by biopsy and clinical follow-up of at least six months in people with negative index tests) in people with pancreatic lesions irrespective of language or publication status or whether the data were collected prospectively or retrospectively.

DATA COLLECTION AND ANALYSIS

Two review authors independently searched the references to identify relevant studies and extracted the data. We planned to use the bivariate analysis to calculate the summary sensitivity and specificity with their 95% confidence intervals and the hierarchical summary receiver operating characteristic (HSROC) to compare the tests and assess heterogeneity, but used simpler models (such as univariate random-effects model and univariate fixed-effect model) for combining studies when appropriate because of the sparse data. We were unable to compare the diagnostic performance of the tests using formal statistical methods because of sparse data.

MAIN RESULTS

We included 54 studies involving a total of 3,196 participants evaluating the diagnostic accuracy of various index tests. In these 54 studies, eight different target conditions were identified with different final diagnoses constituting benign, precancerous, and cancerous lesions. None of the studies was of high methodological quality. None of the comparisons in which single studies were included was of sufficiently high methodological quality to warrant highlighting of the results. For differentiation of cancerous lesions from benign or precancerous lesions, we identified only one study per index test. The second analysis, of studies differentiating cancerous versus benign lesions, provided three tests in which meta-analysis could be performed. The sensitivities and specificities for diagnosing cancer were: EUS-FNA: sensitivity 0.79 (95% confidence interval (CI) 0.07 to 1.00), specificity 1.00 (95% CI 0.91 to 1.00); EUS: sensitivity 0.95 (95% CI 0.84 to 0.99), specificity 0.53 (95% CI 0.31 to 0.74); PET: sensitivity 0.92 (95% CI 0.80 to 0.97), specificity 0.65 (95% CI 0.39 to 0.84). The third analysis, of studies differentiating precancerous or cancerous lesions from benign lesions, only provided one test (EUS-FNA) in which meta-analysis was performed. EUS-FNA had moderate sensitivity for diagnosing precancerous or cancerous lesions (sensitivity 0.73 (95% CI 0.01 to 1.00) and high specificity 0.94 (95% CI 0.15 to 1.00), the extremely wide confidence intervals reflecting the heterogeneity between the studies). The fourth analysis, of studies differentiating cancerous (invasive carcinoma) from precancerous (dysplasia) provided three tests in which meta-analysis was performed. The sensitivities and specificities for diagnosing invasive carcinoma were: CT: sensitivity 0.72 (95% CI 0.50 to 0.87), specificity 0.92 (95% CI 0.81 to 0.97); EUS: sensitivity 0.78 (95% CI 0.44 to 0.94), specificity 0.91 (95% CI 0.61 to 0.98); EUS-FNA: sensitivity 0.66 (95% CI 0.03 to 0.99), specificity 0.92 (95% CI 0.73 to 0.98). The fifth analysis, of studies differentiating cancerous (high-grade dysplasia or invasive carcinoma) versus precancerous (low- or intermediate-grade dysplasia) provided six tests in which meta-analysis was performed. The sensitivities and specificities for diagnosing cancer (high-grade dysplasia or invasive carcinoma) were: CT: sensitivity 0.87 (95% CI 0.00 to 1.00), specificity 0.96 (95% CI 0.00 to 1.00); EUS: sensitivity 0.86 (95% CI 0.74 to 0.92), specificity 0.91 (95% CI 0.83 to 0.96); EUS-FNA: sensitivity 0.47 (95% CI 0.24 to 0.70), specificity 0.91 (95% CI 0.32 to 1.00); EUS-FNA carcinoembryonic antigen 200 ng/mL: sensitivity 0.58 (95% CI 0.28 to 0.83), specificity 0.51 (95% CI 0.19 to 0.81); MRI: sensitivity 0.69 (95% CI 0.44 to 0.86), specificity 0.93 (95% CI 0.43 to 1.00); PET: sensitivity 0.90 (95% CI 0.79 to 0.96), specificity 0.94 (95% CI 0.81 to 0.99). The sixth analysis, of studies differentiating cancerous (invasive carcinoma) from precancerous (low-grade dysplasia) provided no tests in which meta-analysis was performed. The seventh analysis, of studies differentiating precancerous or cancerous (intermediate- or high-grade dysplasia or invasive carcinoma) from precancerous (low-grade dysplasia) provided two tests in which meta-analysis was performed. The sensitivity and specificity for diagnosing cancer were: CT: sensitivity 0.83 (95% CI 0.68 to 0.92), specificity 0.83 (95% CI 0.64 to 0.93) and MRI: sensitivity 0.80 (95% CI 0.58 to 0.92), specificity 0.81 (95% CI 0.53 to 0.95), respectively. The eighth analysis, of studies differentiating precancerous or cancerous (intermediate- or high-grade dysplasia or invasive carcinoma) from precancerous (low-grade dysplasia) or benign lesions provided no test in which meta-analysis was performed.There were no major alterations in the subgroup analysis of cystic pancreatic focal lesions (42 studies; 2086 participants). None of the included studies evaluated EUS elastography or sequential testing.

AUTHORS' CONCLUSIONS

We were unable to arrive at any firm conclusions because of the differences in the way that study authors classified focal pancreatic lesions into cancerous, precancerous, and benign lesions; the inclusion of few studies with wide confidence intervals for each comparison; poor methodological quality in the studies; and heterogeneity in the estimates within comparisons.

Differentiation of pancreatic carcinoma and mass-forming focal pancreatitis: qualitative and quantitative assessment by dynamic contrast-enhanced MRI combined with diffusion-weighted imaging

Differentiation between pancreatic carcinoma (PC) and mass-forming focal pancreatitis (FP) is invariably difficult. For the differential diagnosis, we qualitatively and quantitatively assessed the value of dynamic contrast-enhanced MRI (DCE-MRI) and diffusion-weighted imaging (DWI) in PC and FP in the present study. This study included 32 PC and 18 FP patients with histological confirmation who underwent DCE-MRI and DWI. The time-signal intensity curve (TIC) of PC and FP were classified into 5 types according to the time of reaching the peak, namely, type I, II, III, IV, and V, respectively, and two subtypes, namely, subtype-a (washout type) and subtype-b (plateau type) according to the part of the TIC profile after the peak. Moreover, the mean and relative apparent diffusion coefficient (ADC) value between PC and FP on DWI were compared. The type V TIC was only recognized in PC group (P < 0.01). Type IV b were more frequently observed in PC (P = 0.036), while type- IIa (P < 0.01), type- Ia (P = 0.037) in FP. We also found a significant difference in the mean and relative ADC value between PC and FP. The combined image set of DCE-MRI and DWI yielded an excellent sensitivity, specificity, and diagnostic accuracy (96.9%, 94.4%, and 96.0%). The TIC of DCE-MRI and ADC value of DWI for pancreatic mass were found to provide reliable information in differentiating PC from FP, and the combination of DCE-MRI and DWI can achieve a higher sensitivity, specificity, and diagnostic accuracy.

Differentiation of mass-forming focal pancreatitis from pancreatic ductal adenocarcinoma: value of characterizing dynamic enhancement patterns on contrast-enhanced MR images by adding signal intensity color mapping

OBJECTIVES

To evaluate the value of dynamic enhancement patterns on contrast-enhanced MR images by adding signal intensity colour mapping (SICM) to differentiate mass-forming focal pancreatitis (MFFP) from pancreatic ductal adenocarcinoma (PDAC).

METHODS

Forty-one clinicopathologically proven MFFPs and 144 surgically confirmed PDACs were enrolled. Laboratory and MR imaging parameters were used to differentiate MFFP from PDAC. In particular, enhancement patterns on MR images adding SICM were evaluated. By using classification tree analysis (CTA), we determined the predictors for the differentiation of MFFP from PDAC.

RESULTS

In the CTA, with all parameters except enhancement pattern on SICM images, ductal obstruction grade and T1 hypointensity grade of the pancreatic lesion were the first and second splitting predictor for differentiation of MFFP from PDAC, in order. By adding an enhancement pattern on the SICM images to CTA, the enhancement pattern was the only splitting predictor to differentiate MFFP from PDAC. The CTA model including enhancement pattern on SICM images has sensitivity of 78.0 %, specificity of 99.3 %, and accuracy of 94.6 % for differentiating MFFP from PDAC.

CONCLUSION

The characterization of enhancement pattern for pancreatic lesions on contrast-enhanced MR images adding SICM would be helpful to differentiate MFFP from PDAC.

KEY POINTS

• SICM was useful to characterize enhancement pattern. • Enhancement pattern on SICM was the only splitting predictor on CTA. • This model may be useful for differentiating MFFP from PDAC.

Various diffusion magnetic resonance imaging techniques for pancreatic cancer

Pancreatic cancer is one of the most common malignant tumors and remains a treatment-refractory cancer with a poor prognosis. Currently, the diagnosis of pancreatic neoplasm depends mainly on imaging and which methods are conducive to detecting small lesions. Compared to the other techniques, magnetic resonance imaging (MRI) has irreplaceable advantages and can provide valuable information unattainable with other noninvasive or minimally invasive imaging techniques. Advances in MR hardware and pulse sequence design have particularly improved the quality and robustness of MRI of the pancreas. Diffusion MR imaging serves as one of the common functional MRI techniques and is the only technique that can be used to reflect the diffusion movement of water molecules in vivo. It is generally known that diffusion properties depend on the characterization of intrinsic features of tissue microdynamics and microstructure. With the improvement of the diffusion models, diffusion MR imaging techniques are increasingly varied, from the simplest and most commonly used technique to the more complex. In this review, the various diffusion MRI techniques for pancreatic cancer are discussed, including conventional diffusion weighted imaging (DWI), multi-b DWI based on intra-voxel incoherent motion theory, diffusion tensor imaging and diffusion kurtosis imaging. The principles, main parameters, advantages and limitations of these techniques, as well as future directions for pancreatic diffusion imaging are also discussed.

Diffusion-weighted magnetic resonance imaging for non-neoplastic conditions in the hepatobiliary and pancreatic regions: pearls and potential pitfalls in imaging interpretation

Potentially, diffusion-weighted magnetic resonance imaging (DWI) can assess the functional information on concerning the status of tissue cellularity, because increased cellularity is associated with impeded diffusion. DWI in the hepatobiliary and pancreatic regions has demonstrated the usefulness to detect malignant lesions and differentiate them from benign lesions. However, it has been shown more recently that there is some overlap in ADC values for benign and malignant neoplasms. Moreover, some non-neoplastic lesions in the hepatobiliary and pancreatic regions exhibit restricted diffusion on DWI, because of pus, inflammation, or high cellularity. Focal eosinophilic liver disease, hepatic inflammatory myofibroblastic tumor, granulomatous liver disease, acute cholecystitis, xanthogranulomatous cholecystitis, focal pancreatitis, or autoimmune pancreatitis frequently exhibit restricted diffusion on DWI, which may be confused with malignancy in the hepatobiliary and pancreatic regions. Thus, DWI should not be interpreted in isolation, but in conjunction with other conventional images, to avoid the diagnostic pitfalls of DWI. Nevertheless, the presence of diffusion restriction in the non-neoplastic lesions sometimes provides additional information regarding the diagnosis, in problematic patients where conventional images have yielded equivocal findings. DWI may help differentiate hepatic abscess from malignant necrotic tumors, gallbladder empyema from dense bile or sludge in the gallbladder, and pylephlebitis from bland thrombosis in the portal vein. Therefore, knowledge of DWI findings to conventional imaging findings of diffusion-restricted non-neoplastic conditions in the hepatobiliary and pancreatic regions helps establishing a correct diagnosis.

Comparison of preoperative evaluation of malignant low-level biliary obstruction using plain magnetic resonance and coronal liver acquisition with volume acceleration technique alone and in combination

Background

To evaluate the clinical value of plain magnetic resonance (MR) imaging (including magnetic resonance cholangiopancreatography, MRCP) and coronal liver acquisition with volume acceleration (LAVA) technique in the diagnosis and preoperative assessment of malignant low-level biliary obstruction.

Methods

Forty-one patients with confirmed malignant low-level biliary obstruction were examined by plain MR, MRCP and coronal LAVA techniques. Group 1, plain MR (including MRCP); group 2, coronal LAVA; group 3, plain MR and coronal LAVA. Assessments included positioning, qualitative diagnosis and preoperative evaluation. The results were compared with pathological, endoscopic retrograde cholangiopancreatography or percutaneous transhepatic cholangiography results.

Results

There were 14 pancreatic adenocarcinoma, 12 distal common bile duct carcinoma, 10 ampullary carcinoma, and 5 duodenal carcinoma cases. There was no significant difference in accuracy of the three groups’ positioning diagnoses, 87.8, 90.2, and 92.7 %, respectively. The accuracy of the qualitative diagnoses was lower in group 1 at 78.0 %, but not significantly different in groups 2 and 3 at 92.7 and 95.1 %, respectively (P = 0.031, and 0.039, group 1 vs groups 2 and 3, respectively). Thirty-three patients underwent open surgery. There were 19 adjacent organ involvements, 9 vascular involvements, 13 lymph node metastases and 6 liver metastases. 22 patients were verified surgically and histologically for resectable lesions. Plain MR with coronal LAVA imaging showed 85.4 % accuracy, 90.9 % sensitivity, 78.9 % specificity, 83.3 % positive and 88.2 % negative predictive value for resectability.

Conclusions

Plain MR and coronal LAVA techniques are potential noninvasive tools for diagnosis and preoperative assessment of malignant low-level biliary obstruction.

Electronic supplementary material

The online version of this article (doi:10.1186/s40001-015-0188-3) contains supplementary material, which is available to authorized users.

Diffusion-weighted imaging of pancreatic cancer

Magnetic resonance imaging (MRI) is a reliable and accurate imaging method for the evaluation of patients with pancreatic ductal adenocarcinoma (PDAC). Diffusion-weighted imaging (DWI) is a relatively recent technological improvement that expanded MRI capabilities, having brought functional aspects into conventional morphologic MRI evaluation. DWI can depict the random diffusion of water molecules within tissues (the so-called Brownian motions). Modifications of water diffusion induced by different factors acting on the extracellular and intracellular spaces, as increased cell density, edema, fibrosis, or altered functionality of cell membranes, can be detected using this MR sequence. The intravoxel incoherent motion (IVIM) model is an advanced DWI technique that consent a separate quantitative evaluation of all the microscopic random motions that contribute to DWI, which are essentially represented by molecular diffusion and blood microcirculation (perfusion). Technological improvements have made possible the routine use of DWI during abdominal MRI study. Several authors have reported that the addition of DWI sequence can be of value for the evaluation of patients with PDAC, especially improving the staging; nevertheless, it is still unclear whether and how DWI could be helpful for identification, characterization, prognostic stratification and follow-up during treatment. The aim of this paper is to review up-to-date literature data regarding the applications of DWI and IVIM to PDACs.

Apparent diffusion coefficient (ADC) measurements in pancreatic adenocarcinoma: A preliminary study of the effect of region of interest on ADC values and interobserver variability

PURPOSE

To assess the influence of region of interest (ROI) on tumor apparent diffusion coefficient (ADC) measurements and interobserver variability in pancreatic ductal adenocarcinoma (PDAC).

MATERIALS AND METHODS

Twenty-two patients recruited with pathology-proven PDAC underwent diffusion-weighted imaging (DWI, 3.0T) prior to the surgical resection. Two independent readers measured tumor ADCs according to three ROI methods: whole-volume, single-slice, and small solid sample of tumor. Minimum and mean ADCs were obtained. The interobserver variability for each of the three methods was analyzed using interclass correlation coefficient (ICC) and Bland-Altman analysis. The minimum and mean ADCs among the ROI methods were compared using nonparametric tests.

RESULTS

The single-slice ROI method showed the best reproducibility in the minimum ADC measurements (mean difference ± limits of agreement between two readers were 0.025 ± 0.25 × 10(-3) mm2 /s; ICC, 0.92) among the three ROI methods. For the solid tumor sample ROI, both minimum ADC and mean ADC measurements reproducibility were the worst, with limits of agreement up to ±0.50 × 10(-3) mm2 /s and ±0.32 × 10(-3) mm2 /s, respectively (ICCs, 0.41/0.58). Both the minimum and mean ADCs demonstrated significant differences among the three ROI methods (both P < 0.001). The post-hoc analyses results showed no significant difference with regard to the mean ADCs between whole-volume and single-slice ROI methods (P = 0.14).

CONCLUSION

The ROI method had a considerable influence on both the minimum and mean ADC values and the interobserver variability in PDAC. The worst interobserver variability was observed for both the minimum and mean ADCs derived from small solid-sample ROI.

Differential diagnosis of pancreatic cancer by single-shot echo-planar imaging diffusion-weighted imaging

AIM: To investigate the diagnostic ability of single-shot echo-planar imaging (EPI) diffusion-weighted imaging (DWI) to differentiate between malignant and benign pancreatic lesions.

METHODS: A computerized search was performed on PubMed, MEDLINE and EMBASE up to August 2014. Nine studies (10 sets of data) with a total of 304 malignant pancreatic lesions and 188 benign pancreatic lesions were included. The characteristics of each study included the study name, year of publication, magnetic resonance modalities used, patient population, strength of field, pulse time, repetition time, echo time (TE), maximum b factor, mean age, mean body weight, fat suppression, number of benign and malignant lesions, and true positive, true negative, false positive and false negative results. All analyses were performed using Meta-DiSc and Stata 11.0.

RESULTS: The pooled sensitivity and specificity of single-shot EPI DWI were 0.83 (95%CI: 0.79-0.87) and 0.77 (95%CI: 0.70-0.83), respectively. The positive likelihood ratio and negative likelihood ratio were 5.09 (95%CI: 2.19-11.84) and 0.23 (95%CI: 0.15-0.36), respectively. The P value for the χ² heterogeneity for all pooled estimates was < 0.05. From the fitted summary receiver operating characteristic curve, the area under the curve and Q* index were 0.89 and 0.82, respectively. Publication bias was not present (t = 0.58, P = 0.58). Meta-regression analysis indicated that fat suppression, mean age, TE, and maximum b factor were not sources of heterogeneity (all P > 0.05).

CONCLUSION: Single-shot EPI DWI is useful to differentiate between malignant and benign pancreatic lesions. Lesion size ≥ 2 cm is the limit for the diagnosis of early lesions.

Meta-analysis of quantitative diffusion-weighted MR imaging in differentiating benign and malignant pancreatic masses

There have been numerous studies done to explore the diagnostic performance of quantitative diffusion-weighted (DW) MR imaging to differentiate between benign and malignant pancreatic masses. However, the results have been inconsistent. We performed a meta-analysis to investigate whether DW-MR imaging can differentiate between these two diseases. Databases including MEDLINE, EMBASE and Cochrane Library were utilized to find relevant articles published between January 2001 and January 2014. A Stata version 12.0 and a Meta-Disc version 1.4 were used to describe primary results. Twelve studies with 594 patients, which fulfilled the inclusion criteria, were enrolled for the analysis. The pooled sensitivity and specificity of DW imaging was 0.91 (95% CI: 0.84, 0.95) and 0.86 (95% CI: 0.76, 0.93) respectively. The area under the curve of the summary receiver operating characteristic was 0.95 (95% CI: 0.93, 0.96). The results indicated that DW imaging might be a valuable tool for differentiating benign and malignant pancreatic masses.

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.

Early diagnosis of pancreatic cancer

Pancreatic cancer is a common malignancy of the pancreas, with about 90% originating in the glandular epithelium. As a highly malignant gastrointestinal tumor, pancreatic cancer is difficult to diagnose and treat. The silent nature of the clinical manifestations and the difficulty of early diagnosis lead to a poor prognosis. In recent years, the incidence rate and mortality rate have increased significantly, with the 5-year survival rate being less than 1%. It is evident that early diagnosis is an effective strategy to improve the prognosis and therefore has become a hotspot of research. This article reviews the progress in early diagnosis of pancreatic cancer in terms of imageological diagnosis, serological examinations and genomic testing as well as the screening of high-risk populations.

Current options for the diagnosis of chronic pancreatitis

The diagnostic options for chronic pancreatitis have evolved over recent years. The previous gold standard references for structural imaging and exocrine pancreatic function testing have both been supplanted and redesigned. Endoscopic retrograde pancreatography has now been overtaken by endoscopic ultrasound and magnetic resonance cholangiopancreatography, whilst the old technique for Dreiling tube pancreatic function testing has now been replaced by the endoscopic pancreatic function test. New advances in endoscopic ultrasound elastography have also extended the options for evaluating pancreatic masses to differentiate mass-forming chronic pancreatitis from malignancy. Genetic contribution to chronic pancreatitis is also now more widely recognized than ever before.

High resolution diffusion weighted magnetic resonance imaging of the pancreas using reduced field of view single-shot echo-planar imaging at 3 T

Diffusion weighted magnetic resonance imaging (DWI) has been mostly acquired using single-shot echo-planar imaging (ss EPI) to minimize motion induced artifacts. The spatial resolution, however, is inherently limited in ss EPI especially for abdominal imaging, even with the advances in parallel imaging. A novel method of reduced Field of View ss EPI (rFOV ss EPI) has achieved high resolution DWI in human carotid artery, spinal cord with reduced blurring and higher spatial resolution than conventional ss EPI, but it has not been used to pancreas imaging. In the work, comparisons between the full FOV ss-DW EPI and rFOV ss-DW EPI in image qualities and ADC values of pancreatic tumors and normal pancreatic tissues were performed to demonstrate the feasibility of pancreatic high resolution rFOV DWI. There were no significant differences in the mean ADC values between full FOV DWI and rFOV DWI for the 17 subjects using b=600s/mm(2) (P=0.962). However, subjective scores of image quality was significantly higher at rFOV ss DWI (P=0.008 and 0.000 for b-value=0s/mm(2) and 600s/mm(2) respectively). The spatial resolution of DWI for pancreas was increased by a factor of over 2.0 (from almost 3.0mm/pixel to 1.25mm/pixel) using rFOV ss EPI technique. Reduced FOV ss EPI can provide good DW images and is promising to benefit applications for pancreatic diseases.

The effect of gadolinium chelate contrast agent on diffusion-weighted imaging of pancreatic ductal adenocarcinoma

BACKGROUND

There are only two studies that discuss the effect of a gadolinium chelate contrast agent on pancreatic diffusion-weighted imaging (DWI). However, both studies only included normal pancreas and/or pancreas with pancreatitis and did not include pancreatic ductal adenocarcinoma (PDA).

PURPOSE

To investigate the effect of gadolinium chelate contrast agent on DWI of PDA.

MATERIAL AND METHODS

Twenty-two patients (13 men, 9 women; mean age 62 years) with histopathologically proven PDA were included in this study. DWI was acquired before and after administration of gadopentetate dimeglumine (Magnevist) with two b-values: 0 and 1000 s/mm(2). The signal intensity (SI), signal-to-noise ratio (SNR), and the apparent diffusion coefficient (ADC) of the lesion were recorded for comparison.

RESULTS

The mean time interval between the initiation of contrast administration and the start of the postcontrast DWI series was 393 s (range, 350-510 s). The SIs and SNRs of lesions of b1000 and b0 images of enhanced images were significantly higher than non-enhanced images (P < 0.001, P < 0.001 for b1000 s/mm(2); P = 0.001, P = 0.001 for b0 s/mm(2)). The ADC of all PDAs revealed no statistically significant difference between non-enhanced and enhanced images (P = 0.709). There was also no significant difference between non-enhanced and enhanced images in subgroups based on grades of differentiation and locations of lesion.

CONCLUSION

With increasing SI and SNR of PDA, intravenous contrast administration does not result in a significant difference in quantitative ADC measurements when comparing precontrast to postcontrast DWI when acquired approximately 6-7 min after administration.

[Diffusion-weighted MR imaging; the significance of ADC and perfusion values in the differential diagnosis of pancreatic adenocarcinoma and mass forming pancreatitis]

Despite the increasing diagnostic accuracy of cross sectional imaging modalities, the correct differentiation between pancreatic adenocarcinoma and mass forming pancreatitis has remained a challenge.

AIM

Based on their 2 and ½ -year experience, the aim of the authors was to assess the clinical utility of diffusion-weighted magnetic resonance imaging in the diagnosis and discernment of pancreatic adenocarcinoma and mass forming pancreatitis.

METHODS

3 b-values diffusion-weighted magnetic resonance examinations were performed in 19 patients suffering from adenocarcinoma and in 8 patients with pancreatitis. 12 healthy patients were examined as reference. Apparent diffusion coefficient and perfusion values were calculated. Malignancy was verified by pathology in all cases. An inflammatory disease was diagnosed on the basis of previous medical history, changes in laboratory values, follow-up computer tomographic examinations and improvement in the patients' condition.

RESULTS

Comparison of the apparent diffusion coefficient and perfusion values revealed significant differences between healthy pancreatic tissues and those affected by inflammation or tumor. The highest apparent diffusion coefficient and perfusion values were detected in the normal pancreas. Mass forming pancreatitis had diminished the apparent diffusion coefficient and perfusion values, whereas these values were the lowest in tumorous tissues.

CONCLUSION

In agreement with literature data, the authors conclude that diffusion-weighted magnetic resonance imaging is a promising differential-diagnostic imaging tool in the distinction of circumscribed pancreatic lesions.

Advances in magnetic resonance molecular and functional imaging to diagnose pancreatic cancer

Pancreatic cancer has a high mortality rate, which is generally related to the initial diagnosis coming at late stage disease combined with a lack of effective diagnostic techniques. Over the past few years, molecular-functional imaging, which can be defined as the in vivo characterization and measurement of biologic processes at the molecular and gene levels, has developed rapidly and allows diagnosing pancreatic cancer more early and specifically. Magnetic resonance (MR) imaging is widely used for molecular imaging because of the high spatial resolution. This paper reviews recent advances in MR molecular and functional imaging to diagnose pancreatic cancer.

Early detection of pancreatic cancer: a possibility in some cases but not a reality in most

Pancreatic cancer is notoriously difficult to diagnose until a late stage when curative options are no longer available. Owing to its relatively low incidence and the lack of sensitivity of current diagnostic tool, screening of pancreatic cancer in the general population is not recommended. However, in high-risk individuals, especially those with well-described genetic syndromes and a strong family history of pancreatic cancer, screening can be carried out. Detection of a lesion of the diameter < 1 cm without lymph node involvements and subsequent removal of the tumor results in long-term cure of the cancer. Endoscopic ultrasound (EUS) is the only diagnostic tool that is able to detect such small lesions. EUS is often combined with endoscopic retrograde cholangiography to augment the diagnostic yield. The conundrum in clinical practice is to differentiate between a malignant and a benign lesion. Resection of the pancreas constitutes major surgery with a high morbidity and mortality. The need continues, therefore, to find even more accurate imaging modalities to diagnose small pancreatic cancers with confidence.

Apparent diffusion coefficient measurements in the differentiation between benign and malignant lesions: a systematic review

Objectives

To systematically review the value of apparent diffusion coefficient (ADC) measurement in the differentiation between benign and malignant lesions.

Methods

A systematic search of the Medline/Pubmed and Embase databases revealed 109 relevant studies. Quality of these articles was assessed using the Quality Assessment of the Studies of Diagnostic Accuracy Included in Systematic Reviews (QUADAS) criteria. Reported ADC values of benign and malignant lesions were compared per organ.

Results

The mean quality score of the reviewed articles was 50%. Comparison of ADC values showed marked variation among studies and between benign and malignant lesions in various organs. In several organs, such as breast, liver, and uterus, ADC values discriminated well between benign and malignant lesions. In other organs, such as the salivary glands, thyroid, and pancreas, ADCs were not significantly different between benign and malignant lesions.

Conclusion

The potential utility of ADC measurement for the characterisation of tumours differs per organ. Future well-designed studies are required before ADC measurements can be recommended for the differentiation of benign and malignant lesions. These future studies should use standardised acquisition protocols and provide complete reporting of study methods, to facilitate comparison of results and clinical implementation of ADC measurement for tumour characterisation.

Electronic supplementary material

The online version of this article (doi:10.1007/s13244-012-0175-y) contains supplementary material, which is available to authorized users.

Value of diffusion-weighted imaging for the discrimination of pancreatic lesions: a meta-analysis

OBJECTIVE

We aimed to explore the role of diffusion-weighted imaging (DWI) in the discrimination of pancreatic lesions through meta-analysis.

METHODS

The MEDLINE, EMBASE, Cancerlit, and Cochrane Library databases, from January 2001 to August 2011, were searched for studies evaluating the diagnostic performance of DWI in the discrimination of pancreatic lesions. We determined sensitivities and specificities across studies, calculated positive and negative likelihood ratios (LR+ and LR-), and constructed summary receiver operating characteristic curves.

RESULTS

A total of 11 studies with 586 patients, who fulfilled all of the inclusion criteria, were considered for the analysis. No publication bias was found. The pooled sensitivity of DWI was 0.86 [95% (confidence interval (CI), 0.78, 0.91] and the pooled specificity was 0.91 (95% CI, 0.81, 0.96). Overall, LR+ was 9.8 (95% CI, 4.1, 23.3) and LR- was 0.15 (95% CI, 0.09, 0.26). The area under the curve of the summary receiver operating characteristic was 0.94 (95% CI, 0.91-0.96). In subgroup analysis, prospectively designed studies had the highest pooled sensitivity (0.87, 95% CI 0.75, 0.94) and specificity (0.96, 95% CI 0.91, 0.99) (P<0.05). Study sensitivity was not correlated with the prevalence of pancreatic lesions (R=0.1076, P=0.3247).

CONCLUSION

A limited number of small studies suggest that DWI is a potentially technically feasible measure to differentiate malignant from benign pancreatic lesions. However, it is still controversial and is limited in that it can only distinguish certain lesions. High-quality prospective studies on DWI for the discrimination of pancreatic lesions still need to be conducted.