Assessment of Chronic Pancreatitis: Use of Whole Pancreas Perfusion With 256-Slice Computed Tomography

Pancreatic fibrosis assessment and association with pancreatic cancer: comparison with the extracellular volume fraction

AIMS

To compare the iodine washout rate (IWR) from multiphasic contrast-enhanced computed tomography (CT) with the extracellular volume fraction (fECV) for assessing pancreatic fibrosis and its association with pancreatic cancer.

MATERIALS AND METHODS

The study included 51 individuals (33 men; median age: 69 years; 21 with pancreatic cancer, 30 with other diseases) who underwent multiphasic contrast-enhanced CT and histological evaluation for fibrotic changes in pancreas. The histological pancreatic fibrosis fraction (HPFF) was assessed on Azan-stained sections. Pancreatic parenchymal enhancement values were measured to calculate IWR and fECV. Statistical methods, such as Spearman's rho and Mann-Whitney U-test, were used. Linear regression models using IWR and fECV were constructed to predict HPFF, with the performance expressed as root mean squared error (RMSE) and Akaike information criterion (AIC).

RESULTS

HPFF correlated with all CT parameters at the estimated transection line, strongest for IWRPPP-EP (r=-0.69, P<0.01). HPFF and fECV values were higher in the pancreatic cancer group than in controls (30% vs. 12.5%, P<0.01; 40.3% vs. 33.0%, P<0.01), whereas IWR values were lower (IWRPPP-EP: 43.3% vs. 55.0%, P<0.01; IWRPVP-EP: 25.0% vs. 33.5%, P<0.01). Linear regression models combining IWRPPP-EP + fECV and IWRPVP-EP + fECV were superior for predicting HPFF, with lower RMSE (9.23-9.35) and AIC (379.38-380.72) values than models with IWR or fECV alone.

CONCLUSION

IWRPPP-EP, IWRPVP-EP, and fECV were reliable biomarkers for noninvasively assessing pancreatic fibrosis and were associated with pancreatic cancer risk. Linear regression combining these variables showed enhanced predictive accuracy for pancreatic fibrosis.

Dynamic Contrast-Enhanced MRI Assessing Antifibrotic Therapeutic Effects of Pancreatic Fibrosis with Curcumin - An Experimental Study at 11.7 T

RATIONALE AND OBJECTIVES

Pancreatic fibrosis is the hallmark of chronic pancreatitis (CP), which is associated with microcirculatory disturbance. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) can assess the perfusion and permeability of the pancreas by providing information about microcirculation. We hypothesize that DCE-MRI parameters can be utilized to assess pancreatic fibrosis and may furthermore provide an opportunity to evaluate response to antifibrotic treatment with curcumin. Our study was to evaluate the feasibility of quantitative DCE-MRI in assessing pancreatic fibrosis and the antifibrotic effect of curcumin in a rat model of CP.

MATERIALS AND METHODS

Pancreatic fibrosis was induced by injecting dibutyltin dichloride (DBTC). Seventy rats were randomized to five groups: the control group (n = 10); DBTC for 2 weeks (n = 15); DBTC for 4 weeks (n = 15); DBTC + curcumin for 2 weeks (n = 15); DBTC + curcumin for 4 weeks (n = 15). DCE-MRI was performed at an 11.7 T MR scanner. DCE-MRI quantitative parameters (Ktrans, Ve, and Vp) were derived from an extended Tofts model. Fibrosis content and DCE-MRI parameters were compared among the above groups (one-way analysis of variance). The correlations between DCE-MRI parameters and pancreatic fibrosis content as well as the expression of α-SMA were computed by Spearman correlation coefficients.

RESULTS

Fifty-three rats survived and underwent MR imaging. Ktrans in rats 4 weeks after DBTC injection was significantly lower than DBTC 2 weeks rats and control rats (0.30 ± 0.06 min vs 0.49 ± 0.09 vs 0.62 ± 0.09, respectively). Vp in DBTC 4 weeks rats was also significantly lower than control rats (0.048 ± 0.010 min-1 vs 0.065 ± 0.011 min-1, respectively). Ktrans and Vp significantly correlated with fibrosis content of pancreas (r = -0.619 and -0.450, all P < 0.001), and the expression of α-SMA (r = -0.688 and -0.402, all P < 0.01). Ktrans and Vp in rats with daily curcumin treatment for 4 weeks were significantly higher than DBTC 4 weeks rats (Ktrans, 0.51 ± 0.09 vs 0.30 ± 0.06; Vp, 0.064 ± 0.015 vs 0.048 ± 0.010).

CONCLUSION

DCE-MRI parameters (Ktrans and Vp) have the potential to noninvasively assess pancreatic fibrosis and the antifibrotic treatment response of curcumin.

Comparative analysis of two mathematical algorithms for the calculation of computed tomography perfusion parameters in the healthy and diseased pancreas

BACKGROUND

The maximum slope (MS) and deconvolution (DC) algorithms are commonly used to post-process computed tomography perfusion (CTP) data. This study aims to analyze the differences between MS and DC algorithms for the calculation of pancreatic CTP parameters.

METHODS

The pancreatic CTP data of 57 patients were analyzed using MS and DC algorithms. Two blinded radiologists calculated pancreatic blood volume (BV) and blood flow (BF). Interobserver correlation coefficients were used to evaluate the consistency between two radiologists. Paired t-tests, Pearson linear correlation analysis, and Bland-Altman analysis were performed to evaluate the correlation and consistency of the CTP parameters between the two algorithms.

RESULTS

Among the 30 subjects with normal pancreas, the BV values in the three pancreatic regions were higher in the case of the MS algorithm than in the case of the DC algorithm (t = 39.35, p < 0.001), and the BF values in the three pancreatic regions were slightly higher for the MS algorithm than for the DC algorithm (t = 2.19, p = 0.031). Similarly, among the 27 patients with acute pancreatitis, the BV values obtained using the MS methods were higher than those obtained using the DC methods (t = 54.14, p < 0.001). Furthermore, the BF values were higher with the MS methods than the DC methods (t = 8.45, p < 0.001). Besides, Pearson linear correlation and Bland-Altman analysis showed that the BF and BV values showed a good correlation and a bad consistency between the two algorithms.

CONCLUSIONS

The BF and BV values measured using MS and DC algorithms had a good correlation but were not consistent.

New advances in CT imaging of pancreas diseases: a narrative review

Computed tomography (CT) plays a pivotal role as a diagnostic tool in many diagnostic and diffuse pancreatic diseases. One of the major limits of CT is related to the radiation exposure of young patients undergoing repeated examinations. Besides the standard CT protocol, the most recent technological advances, such as low-voltage acquisitions with high performance X-ray tubes and iterative reconstructions, allow for significant optimization of the protocol with dose reduction. The variety of CT tools are further expanded by the introduction of dual energy: the production of energy-selective images (i.e., virtual monochromatic images) improves the image contrast and lesion detection while the material-selective images (e.g., iodine maps or virtual unenhanced images) are valuable for lesion detection and dose reduction. The perfusion techniques provide diagnostic and prognostic information lesion and parenchymal vascularization and interstitium. Both dual energy and perfusion CT have the potential for pushing the limits of conventional CT from morphological evaluation to quantitative imaging applied to inflammatory and oncological diseases. Advances in post-processing of CT images, such as pancreatic volumetry, texture analysis and radiomics provide relevant information for pancreatic function but also for the diagnosis, management and prognosis of pancreatic neoplasms. Artificial intelligence is promising for optimization of the workflow in qualitative and quantitative analyses. Finally, basic concepts on the role of imaging on screening of pancreatic diseases will be provided.

Virtual monoenergetic reconstructions of dynamic DECT acquisitions for calculation of perfusion maps of blood flow: Quantitative comparison to conventional, dynamic 80 kVp CT perfusion

PURPOSE

Investigation of potential improvements in dynamic CT perfusion measurements by exploitation of improved visualization of contrast agent in virtual monoenergetic reconstructions of images acquired with dual-energy computed tomography (DECT).

METHOD

For 17 patients with pancreatic carcinoma, dynamic dual-source DECT acquisitions were performed at 80kVp/Sn140kVp every 1.5 s over 51 s. Virtual monoenergetic images (VMI) were reconstructed for photon energies between 40 keV and 150 keV (5 keV steps). Using the maximum-slope model, perfusion maps of blood flow were calculated from VMIs and 80kVp images and compared quantitatively with regard to blood flow measured in regions of interest in healthy tissue and carcinoma, standard deviation (SD), and absolute-difference-to-standard-deviation ratio (ADSDR) of measurements.

RESULTS

On average, blood flow calculated from VMIs increased with increasing energy levels from 114.3 ± 37.2 mL/100 mL/min (healthy tissue) and 45.6 ± 25.3 mL/100 mL/min (carcinoma) for 40 keV to 128.6 ± 58.9 mL/100 mL/min (healthy tissue) and 75.5 ± 49.8 mL/100 mL/min (carcinoma) for 150 keV, compared to 114.2 ± 37.4 mL/100 mL/min (healthy tissue) and 46.5 ± 26.6 mL/100 mL/min (carcinoma) for polyenergetic 80kVp. Differences in blood flow between tissue types were significant for all energies. Differences between perfusion maps calculated from VMIs and 80kVp images were not significant below 110 keV. SD and ADSDR were significantly better for perfusion maps calculated from VMIs at energies between 40 keV and 55 keV than for those calculated from 80kVp images. Compared to effective dose of dynamic 80kVp acquisitions (4.6 ± 2.2mSv), dose of dynamic DECT/VMI acquisitions (8.0 ± 3.7mSv) was higher.

CONCLUSIONS

Perfusion maps of blood flow based on low-energy VMIs between 40 keV and 55 keV offer improved robustness and quality of quantitative measurements over those calculated from 80kVp image data (reference standard), albeit at increased patient radiation exposure.

Optimum imaging of chronic pancreatitis

Chronic pancreatitis is an inflammatory process of the pancreas characterized by progressive parenchyma destruction, resulting in pain and exocrine and endocrine insufficiency. In the advanced stages the diagnosis by imaging is usually straightforward, while in the early phases of the disease there can be a paucity of findings at imaging, thus making an early diagnosis challenging. Different imaging modalities can have a role in the initial diagnosis and in the longitudinal follow-up of patients affected by chronic pancreatitis, also enabling to assess the complications of the disease. Radiography, Ultrasonography, CT and MRI can all provide morphological information, and MRI with the administration of secretin can also provide functional information. The use of an appropriate technique is fundamental for optimizing the examination to the clinical question.

Advanced imaging techniques for chronic pancreatitis

MRI and MRCP play an important role in the diagnosis of chronic pancreatitis (CP) by imaging pancreatic parenchyma and ducts. MRI/MRCP is more widely used than computed tomography (CT) for mild to moderate CP due to its increased sensitivity for pancreatic ductal and gland changes; however, it does not detect the calcifications seen in advanced CP. Quantitative MR imaging offers potential advantages over conventional qualitative imaging, including simplicity of analysis, quantitative and population-based comparisons, and more direct interpretation of detected changes. These techniques may provide quantitative metrics for determining the presence and severity of acinar cell loss and aid in the diagnosis of chronic pancreatitis. Given the fact that the parenchymal changes of CP precede the ductal involvement, there would be a significant benefit from developing MRI/MRCP-based, more robust diagnostic criteria combining ductal and parenchymal findings. Among cross-sectional imaging modalities, multi-detector CT (MDCT) has been a cornerstone for evaluating chronic pancreatitis (CP) since it is ubiquitous, assesses primary disease process, identifies complications like pseudocyst or vascular thrombosis with high sensitivity and specificity, guides therapeutic management decisions, and provides images with isotropic resolution within seconds. Conventional MDCT has certain limitations and is reserved to provide predominantly morphological (e.g., calcifications, organ size) rather than functional information. The emerging applications of radiomics and artificial intelligence are poised to extend the current capabilities of MDCT. In this review article, we will review advanced imaging techniques by MRI, MRCP, CT, and ultrasound.

Computed tomography based scoring system in a prospectively ascertained cohort of patients with chronic pancreatitis

OBJECTIVE

No standardized system is currently used to report the presence or severity of parenchymal and ductal features of chronic pancreatitis (CP) on CT scan. We report a modification to the previously proposed Cambridge classification to serve this purpose.

METHODS

Contrast-enhanced CT scans of 158 well-phenotyped patients with CP enrolled in the North American Pancreatitis Studies (NAPS2) during 2000-2014 from the University of Pittsburgh were retrospectively reviewed by a subspecialty trained abdominal radiologist. Presence and severity (score scale 0-4) of pancreatic duct (PD) dilation, obstruction and contour irregularity, pancreatic calcifications, atrophy and extent of pancreatic involvement were recorded to grade the morphological severity of CP and stratify patients into distinct morphologic patterns. Findings were also correlated with clinical features.

RESULTS

Pancreatic atrophy, calcifications, PD dilation and PD irregularity were observed in 80%, 68%, 65%, 58% cases, respectively. An obstructive stone or PD stricture was present in 63%, and 86% had diffuse pancreatic involvement. Using these features, CP was noted to be moderate or severe in 61%, and classified morphologically as obstructive with/without calcifications, calcific but non-obstructive and non-calcific/non-obstructive in 65%, 20%, 15%, respectively. Functional abnormalities but not the presence of pain generally correlated with imaging findings.

CONCLUSION

A structured scoring system can provide qualitative and quantitative assessment of imaging findings in CP and an opportunity for adoption into clinical practice and research for initial evaluation and longitudinal follow-up. Our findings need validation in a prospective cohort before widespread adoption.

Evaluation of Pancreatic VMAT2 Binding with Active and Inactive Enantiomers of [18F]FP-DTBZ in Healthy Subjects and Patients with Type 1 Diabetes

PURPOSE

Previous studies demonstrated the utility of [¹⁸F]fluoropropyl-(+)-dihydrotetrabenazine ([¹⁸F]FP-(+)-DTBZ) as a positron emission tomography (PET) radiotracer for the vesicular monoamine transporter type 2 (VMAT2) to quantify beta cell mass in healthy control (HC) and type 1 diabetes mellitus (T1DM) groups. Quantification of specific binding requires measurement of non-displaceable uptake. Our goal was to identify a reference tissue (renal cortex or spleen) to quantify pancreatic non-specific binding of [¹⁸F]FP-(+)-DTBZ with the inactive enantiomer, [¹⁸F]FP-(-)-DTBZ. This was the first human study of [¹⁸F]FP-(-)-DTBZ.

PROCEDURES

Six HCs and four T1DM patients were scanned on separate days after injection of [¹⁸F]FP-(+)-DTBZ or [¹⁸F]FP-(-)-DTBZ. Distribution volumes (V_T) and standardized uptake values (SUVs) were compared between groups. Three methods for calculation of non-displaceable uptake (V_ND) or reference SUV were applied: (1) use of [¹⁸F]FP-(+)-DTBZ reference V_T as V_ND, assuming V_ND is uniform across organs; (2) use of [¹⁸F]FP-(-)-DTBZ pancreatic V_T as V_ND, assuming that V_ND is uniform between enantiomers in the pancreas; and (3) use of a scaled [¹⁸F]FP-(+)-DTBZ reference V_T as V_ND, assuming that a ratio of non-displaceable uptake between organs is uniform between enantiomers. Group differences in V_T (or SUV), binding potential (BP_ND), or SUV ratio (SUVR) were estimated using these three methods.

RESULTS

[¹⁸F]FP-(-)-DTBZ V_T values were different among organs, and V_T(+) and V_T(-) were also different in the renal cortex and spleen. Method 3 with the spleen to estimate V_ND (or reference SUV) gave the highest non-displaceable uptake and the largest HC vs. T1DM group differences. Significant group differences were also observed in V_T (or SUV) with method 1 using spleen. SUV was affected by differences in the input function between groups and between enantiomers.

CONCLUSIONS

Non-displaceable uptake was different among organs and between enantiomers. Use of scaled spleen V_T values for V_ND is a suitable method for quantification of VMAT2 in the pancreas.

Functional imaging in pancreatic disease

In addition to the classical morphological evaluation of pancreatic disease, the constant technological advances in imaging techniques based fundamentally on computed tomography and magnetic resonance imaging have enabled the quantitative functional and molecular evaluation of this organ. In many cases, this imaging-based information results in substantial changes to patient management and can be a fundamental tool for the development of biomarkers. The aim of this article is to review the role of emerging functional and molecular techniques based on computed tomography and magnetic resonance imaging in the evaluation of pancreatic disease.

Advances in Pancreatic CT Imaging

OBJECTIVE

The purpose of this article is to discuss the advances in CT acquisition and image postprocessing as they apply to imaging the pancreas and to conceptualize the role of radiogenomics and machine learning in pancreatic imaging.

CONCLUSION

CT is the preferred imaging modality for assessment of pancreatic diseases. Recent advances in CT (dual-energy CT, CT perfusion, CT volumetry, and radiogenomics) and emerging computational algorithms (machine learning) have the potential to further increase the value of CT in pancreatic imaging.

Computed Tomographic Angiography of the Pancreas in Cats with Chronic Diabetes Mellitus Compared to Normal Cats

Background

Diabetes mellitus (DM) is a common endocrinopathy in cats. No known diagnostic test or patient characteristic at the time of diagnosis can predict likely disease course, unlike in people in whom computed tomographic angiography (CTA) is used. No published data exist regarding the CTA appearance of the pancreas in cats with DM, and thus, it is unknown what if any CTA variables should be further assessed for associations with pancreatic endocrine function.

Hypothesis/Objectives

A significant difference in pancreatic attenuation, volume, and size will be identified between normal cats and those with chronic DM on CTA.

Animals

Ten healthy control cats and 15 cats with naturally occurring DM present for >12 months.

Methods

Prospective cross‐sectional study comparing pancreatic attenuation, enhancement pattern, size, volume, pancreatic volume‐to‐body weight ratio (V:BW), pancreatic arterial: portal phase ratio (A:P), time‐to‐arterial enhancement, and time‐to‐peak portal enhancement on CTA between sedated healthy control cats and those with chronic DM.

Results

The pancreas in cats with chronic DM was significantly larger, had higher volume, higher V:BW, and shorter time‐to‐peak portal enhancement on CTA when compared to normal cats.

Conclusions and Clinical Importance

Peak portal enhancement time, pancreatic size, pancreatic volume, and V:BW can be used to differentiate normal sedated cats from those with chronic DM by CTA. These variables warrant further investigation to identify possible associations with endocrine function.

JOG Technique Versus Nonspiral Axial Scan in Pancreatic Perfusion Computed Tomography Imaging and Their Preliminary Application

OBJECTIVE

The aim of this study was to investigate the advantages and disadvantages of JOG technique in pancreatic perfusion computed tomography (CT) imaging.

METHODS

First, 40 male patients with nonpancreatic diseases, aged 40 to 60 years, were averagely assigned into 2 groups (A and B). Patients in group A and B underwent nonspiral axial perfusion and JOG technique CT scans of the pancreas, respectively. Second, 23 patients with pancreatic masses were randomly assigned into nonspiral axial scan and JOG groups.

RESULTS

There were no significant differences in all perfusion parameters among the pancreatic head, body, and tail within groups (P > 0.05). Perfusion and time to peak of the pancreatic head, body, and tail differed significantly between groups A and B (P < 0.05). There were significant differences in perfusion parameter values between pancreatic carcinoma tissue and normal pericarcinoma tissue in the nonspiral axial scan group. In the JOG group, perfusion and time to peak differed significantly (P < 0.05).

CONCLUSIONS

The JOG technique should be cautiously selected on pancreatic perfusion CT scans.

Surgical approaches to chronic pancreatitis: indications and imaging findings

Chronic pancreatitis (CP) is an irreversible, inflammatory process characterized by progressive fibrosis of the pancreas that can result in abdominal pain, exocrine insufficiency, and diabetes. Inadequate pain relief using medical and/or endoscopic therapies is an indication for surgery. The surgical management of CP is centered around three main operations including pancreaticoduodenectomy (PD), duodenum-preserving pancreatic head resection (DPPHR) and drainage procedures, and total pancreatectomy with islet autotransplantation (TPIAT). PD is the method of choice when there is a high suspicion for malignancy. Combined drainage and resection procedures are associated with pain relief, higher quality of life, and superior short-term and long-term survival in comparison with the PD. TPIAT is a reemerging treatment that may be promising in subjects with intractable pain and impaired quality of life. Imaging examinations have an extensive role in pre-operative and post-operative evaluation of CP patients. Pre-operative advanced imaging examinations including CT and MRI can detect hallmarks of CP such as calcifications, pancreatic duct dilatation, chronic pseudocysts, focal pancreatic enlargement, and biliary ductal dilatation. Post-operative findings may include periportal hepatic edema, pneumobilia, perivascular cuffing and mild pancreatic duct dilation. Imaging can also be useful in the detection of post-operative complications including obstructions, anastomotic leaks, and vascular lesions. Imaging helps identify unique post-operative findings associated with TPIAT and may aid in predicting viability and function of the transplanted islet cells. In this review, we explore surgical indications as well as pre-operative and post-operative imaging findings associated with surgical options that are typically performed for CP patients.

Pancreatic perfusion data and post-pancreaticoduodenectomy outcomes

BACKGROUND

Precise risk assessment for postoperative pancreatic fistula (POPF) after pancreaticoduodenectomy (PD) may be facilitated using imaging modalities. Computed tomography perfusion (CTP) of the pancreas may represent histologic findings. This study aimed to evaluate the utility of CTP data for the risk of POPF after PD, in relation to histologic findings.

METHODS

Twenty patients who underwent preoperative pancreatic CTP measurement using 320-detector row CT before PD were investigated. Clinicopathologic findings, including CTP data, were analyzed to assess the occurrence of POPF. In addition, the correlation between CTP data and histologic findings was evaluated.

RESULTS

POPF occurred in 11 cases (grade A, 6; grade B, 5; and grade C, 0). In CTP data, both high arterial flow (AF) and short mean transit time (MTT) were related to POPF occurrence (P = 0.001, P = 0.001). AF was negatively correlated with fibrosis in the pancreatic parenchyma (r = -0.680), whereas MTT was positively correlated with fibrosis (r = 0.725). AF >80 mL/min/100 mL and MTT <16 s showed high sensitivity, specificity, positive predictive value, and negative predictive value (80.0%, 100.0%, 100.0%, and 83.3%, respectively) for the occurrence of POPF.

CONCLUSIONS

CTP data for the pancreas were found to be correlated with the occurrence of POPF after PD. Alterations in the blood flow to the remnant pancreas may reflect histological changes, including fibrosis in the pancreatic stump, and influence the outcome after PD. CTP may thus facilitate objective and quantitative risk assessment of POPF after PD.

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..