Tissue perfusion in pathologies of the pancreas: assessment using 128-slice computed tomography

Quantitative evaluation of pancreatic neuroendocrine tumors utilizing dual-source CT perfusion imaging

OBJECTIVE

We aimed to quantitatively analyze the perfusion characteristics of pancreatic neuroendocrine tumors (pNETs) utilizing dual-source CT imaging.

METHODS

Dual-source CT perfusion scans were obtained from patients with pNETs confirmed by surgical or biopsy pathology. Perfusion parameters, including blood flow (BF), blood volume (BV), capillary permeability surface (PS), mean transit time (MTT), contrast transit time to the start (TTS), and contrast transit time to the peak (TTP), were statistically analyzed and compared with nearby healthy tissue. Time density curves (TDCs) were plotted to further understand the dynamic enhancement characteristics of the tumors. Additionally, receiver operating characteristic curves (ROCs) were generated to assess their diagnostic value.

RESULTS

Twenty patients with pNETs, containing 26 lesions, were enrolled in the study, including 6 males with 8 lesions and 14 females with 18 lesions. The average values of BF, BV, PS, MTT, TTP and TTS for the 26 lesions (336.61 ± 216.72 mL/100mL/min, 41.96 ± 16.99 mL/100mL, 32.90 ± 11.91 mL/100 mL/min, 9.44 ± 4.40 s, 19.14 ± 5.6 s, 2.57 ± 1.6 s) were different from those of the adjacent normal pancreatic tissue (44.32 ± 55.35 mL/100mL/min, 28.64 ± 7.95 mL/100mL, 26.69 ± 14.88 mL/100 mL/min, 12.89 ± 3.69 s, 20.33 ± 5.18 s, 2.69 ± 1.71 s). However, there were no statistical differences in PS and TTS between the lesions and the adjacent normal pancreatic tissue (P > 0.05). The areas under the ROC curve for BF, BV, and PS were all greater than 0.5, whereas the areas under the ROC curve for MTT, TTP, and TTS were all less than 0.5.

CONCLUSION

CT perfusion parameters such as BF, BV, MTT, and TTP can distinguish pNETs from healthy tissue. The area under the ROC curve for BF, BV, and PS demonstrates substantial differentiating power for diagnosing pNET lesions.

Perfusion Computed Tomography for Assessing Pancreas Graft Volumetric Perfusion After Simultaneous Pancreas and Kidney Transplantation

Background: There is paucity of data in the available medical literature regarding the parameters of the volumetric perfusion of pancreas grafts. Methods: From 5 February 2016 to 23 December 2021, we performed perfusion computed tomography in 41 patients at different times after simultaneous pancreas and kidney transplantation. The study group consisted of 18 men (44%) and 23 women (56%) with a long history of type 1 diabetes mellitus complicated by terminal chronic renal failure. The results of the perfusion computed tomography of the pancreas graft were studied, and the effects of post-transplantation timing and graft revascularization peculiarities on volumetric perfusion parameters were evaluated. Results: The median arterial blood flow, arterial blood volume, and permeability of the pancreas graft were 115.1 [99.7;130.3] mL/100 mL/min, 46.7 [37.4;56.9] mL/min, and 8.6 [4.1;11.4] mL/100 mL/min, respectively. No statistically significant differences in the averaged perfusion values were found in the head, body, and tail of the pancreas graft. The post-transplantation timing and the number of arteries involved in graft revascularization did not have a significant effect on the volumetric perfusion of the graft. Conclusion: The volumetric perfusion results of the pancreas graft correspond to those obtained in the study of pancreatic perfusion in healthy participants.

Sound speed and attenuation of human pancreas and pancreatic tumors and their influence on focused ultrasound thermal and mechanical therapies

BACKGROUND

There is increasing interest in using ultrasound for thermal ablation, histotripsy, and thermal or cavitational enhancement of drug delivery for the treatment of pancreatic cancer. Ultrasonic and thermal modelling conducted as part of the treatment planning process requires acoustic property values for all constituent tissues, but the literature contains no data for the human pancreas.

PURPOSE

This study presents the first acoustic property measurements of human pancreatic samples and provides examples of how these properties impact a broad range of ultrasound therapies.

METHODS

Data were collected on human pancreatic tissue samples at physiological temperature from 23 consented patients in cooperation with a hospital pathology laboratory. Propagation of ultrasound over the 2.1-4.5 MHz frequency range through samples of various thicknesses and pathologies was measured using a set of custom-built ultrasonic calipers, with the data processed to estimate sound speed and attenuation. The results were used in acoustic and thermal simulations to illustrate the impacts on extracorporeal ultrasound therapies for mild hyperthermia, thermal ablation, and histotripsy implemented with a CE-marked clinical system operating at 0.96 MHz.

RESULTS

The mean sound speed and attenuation coefficient values for human samples were well below the range of values in the literature for non-human pancreata, while the human attenuation power law exponents were substantially higher. The simulated impacts on ultrasound mediated therapies for the pancreas indicated that when using the human data instead of the literature average, there was a 30% reduction in median temperature elevation in the treatment volume for mild hyperthermia and 43% smaller volume within a 60°C contour for thermal ablation, all driven by attenuation. By comparison, impacts on boiling and intrinsic threshold histotripsy were minor, with peak pressures changing by less than 15% (positive) and 1% (negative) as a consequence of the counteracting effects of attenuation and sound speed.

CONCLUSION

This study provides the most complete set of speed of sound and attenuation data available for the human pancreas, and it reiterates the importance of acoustic material properties in the planning and conduct of ultrasound-mediated procedures, particularly thermal therapies.

Total-Body Perfusion Imaging with [11C]-Butanol

Tissue perfusion can be affected by physiology or disease. With the advent of total-body PET, quantitative measurement of perfusion across the entire body is possible. [11C]-butanol is a perfusion tracer with a superior extraction fraction compared with [15O]-water and [13N]-ammonia. To develop the methodology for total-body perfusion imaging, a pilot study using [11C]-butanol on the uEXPLORER total-body PET/CT scanner was conducted. Methods: Eight participants (6 healthy volunteers and 2 patients with peripheral vascular disease [PVD]) were injected with a bolus of [11C]-butanol and underwent 30-min dynamic acquisitions. Three healthy volunteers underwent repeat studies at rest (baseline) to assess test-retest reproducibility; 1 volunteer underwent paired rest and cold pressor test (CPT) studies. Changes in perfusion were measured in the paired rest-CPT study. For PVD patients, local changes in perfusion were investigated and correlated with patient medical history. Regional and parametric kinetic analysis methods were developed using a 1-tissue compartment model and leading-edge delay correction. Results: Estimated baseline perfusion values ranged from 0.02 to 1.95 mL·min-1·cm-3 across organs. Test-retest analysis showed that repeat baseline perfusion measurements were highly correlated (slope, 0.99; Pearson r = 0.96, P < 0.001). For the CPT subject, the largest regional increases were in skeletal muscle (psoas, 142%) and the myocardium (64%). One of the PVD patients showed increased collateral vessel growth in the calf because of a peripheral stenosis. Comorbidities including myocardial infarction, hypothyroidism, and renal failure were correlated with variations in organ-specific perfusion. Conclusion: This pilot study demonstrates the ability to obtain reproducible measurements of total-body perfusion using [11C]-butanol. The methods are sensitive to local perturbations in flow because of physiologic stressors and disease.

Computed tomographic evaluation of pancreatic perfusion in 10 dogs with acute pancreatitis

Severe canine acute pancreatitis can be fatal; imaging features that can predict the clinical course of disease are useful for clinicians. On computed tomography (CT), both pancreatic heterogeneous contrast enhancement and portal vein thrombosis have been correlated with poorer outcome. Perfusion CT is used in human medicine to evaluate pancreatic microcirculation to predict the future development of severe sequela to pancreatitis; this technology has yet to be explored in dogs with acute pancreatitis. The objective of this prospective, case-control study is to evaluate pancreatic perfusion using contrast-enhanced CT in dogs with acute pancreatitis and compare it with previously established values obtained in healthy dogs. Ten client-owned dogs preliminarily diagnosed with acute pancreatitis received a full abdominal ultrasound, specific canine pancreatic lipase (Spec cPL), and perfusion CT. Computer software calculated pancreatic perfusion, peak enhancement index, time to peak enhancement, and blood volume for 3-mm and reformatted 6-mm slices. The data was analyzed using Shapiro-Wilk test, linear mixed model, and Spearman's rho. Values for 3-mm slices were similar to 6-mm slices (all P < 0.05). Dogs with acute pancreatitis had a faster time to peak enhancement than healthy dogs (P = 0.04-0.06). Dogs with acute pancreatitis and homogeneous pancreatic enhancement had higher perfusion, faster time to peak enhancement, and greater blood volume compared to healthy dogs and dogs with acute pancreatitis and heterogeneous pancreatic enhancement (all P = / < 0.05). Pancreatic perfusion decreased with increased pancreatitis severity. No correlation was identified between Spec cPL and pancreatic perfusion (all P > 0.05). These findings preliminarily support perfusion CT in dogs with acute pancreatitis.

Pancreatic CT perfusion: quantitative meta-analysis of disease discrimination, protocol development, and effect of CT parameters

BACKGROUND

This study provides a quantitative meta-analysis of pancreatic CT perfusion studies, investigating choice of study parameters, ability for quantitative discrimination of pancreatic diseases, and influence of acquisition and reconstruction parameters on reported results.

METHODS

Based on a PubMed search with key terms 'pancreas' or 'pancreatic,' 'dynamic' or 'perfusion,' and 'computed tomography' or 'CT,' 491 articles published between 1982 and 2020 were screened for inclusion in the study. Inclusion criteria were: reported original data, human subjects, five or more datasets, measurements of pancreas or pancreatic pathologies, and reported quantitative perfusion parameters. Study parameters and reported quantitative measurements were extracted, and heterogeneity of study parameters and trends over time are analyzed. Pooled data were tested with weighted ANOVA and ANCOVA models for differences in perfusion results between normal pancreas, pancreatitis, PDAC (pancreatic ductal adenocarcinoma), and non-PDAC (e.g., neuroendocrine tumors, insulinomas) and based on study parameters.

RESULTS

Reported acquisition parameters were heterogeneous, except for contrast agent amount and injection rate. Tube potential and slice thickness decreased, whereas tube current time product and scan coverage increased over time. Blood flow and blood volume showed significant differences between pathologies (both p < 0.001), unlike permeability (p = 0.11). Study parameters showed a significant effect on reported quantitative measurements (p < 0.05).

CONCLUSIONS

Significant differences in perfusion measurements between pathologies could be shown for pooled data despite observed heterogeneity in study parameters. Statistical analysis indicates most influential parameters for future optimization and standardization of acquisition protocols.

CRITICAL RELEVANCE STATEMENT

Quantitative CT perfusion enables differentiation of pancreatic pathologies despite the heterogeneity of study parameters in current clinical practice.

Intravenous and oral whole body ketone dosimetry, biodistribution, metabolite correction and kinetics studied by (R)-[1-11C]β-hydroxybutyrate ([11C]OHB) PET in healthy humans

BACKGROUND

Ketones are increasingly recognized as an important and possibly oxygen sparing source of energy in vital organs such as the heart, the brain and the kidneys. Drug treatments, dietary regimens and oral ketone drinks designed to deliver ketones for organ and tissue energy production have therefore gained popularity. However, whether ingested ketones are taken up by various extra-cerebral tissues and to what extent is still largely unexplored. It was therefore the aim of this study to use positron emission tomography (PET) to explore the whole body dosimetry, biodistribution and kinetics of the ketone tracer (R)-[1-¹¹C]β-hydroxybutyrate ([¹¹C]OHB). Six healthy subjects (3 women and 3 men) underwent dynamic PET studies after both intravenous (90 min) and oral (120 min) administration of [¹¹C]OHB. Dosimetry estimates of [¹¹C]OHB was calculated using OLINDA/EXM software, biodistribution was assessed visually and [¹¹C]OHB tissue kinetics were obtained using an arterial input function and tissue time-activity curves.

RESULTS

Radiation dosimetry yielded effective doses of 3.28 [Formula: see text]Sv/MBq (intravenous administration) and 12.51 [Formula: see text]Sv/MBq (oral administration). Intravenous administration of [¹¹C]OHB resulted in avid radiotracer uptake in the heart, liver, and kidneys, whereas lesser uptake was observed in the salivary glands, pancreas, skeletal muscle and red marrow. Only minimal uptake was noted in the brain. Oral ingestion of the tracer resulted in rapid radiotracer appearance in the blood and radiotracer uptake in the heart, liver and kidneys. In general, [¹¹C]OHB tissue kinetics after intravenous administration were best described by a reversible 2-tissue compartmental model.

CONCLUSION

The PET radiotracer [¹¹C]OHB shows promising potential in providing imaging data on ketone uptake in various physiologically relevant tissues. As a result, it may serve as a safe and non-invasive imaging tool for exploring ketone metabolism in organs and tissues of both patients and healthy individuals. Trial registration Clinical trials, NCT0523812, Registered February 10th 2022, https://clinicaltrials.gov/ct2/show/NCT05232812?cond=NCT05232812&draw=2&rank=1 .

A physiologically based pharmacokinetic model for [68Ga]Ga-(HA-)DOTATATE to predict whole-body distribution and tumor sink effects in GEP-NET patients

BACKGROUND

Little is known about parameters that have a relevant impact on (dis)similarities in biodistribution between various ⁶⁸Ga-labeled somatostatin analogues. Additionally, the effect of tumor burden on organ uptake remains unclear. Therefore, the aim of this study was to describe and compare organ and tumor distribution of [⁶⁸Ga]Ga-DOTATATE and [⁶⁸Ga]Ga-HA-DOTATATE using a physiologically based pharmacokinetic (PBPK) model and to identify factors that might cause biodistribution and tumor uptake differences between both peptides. In addition, the effect of tumor burden on peptide biodistribution in gastroenteropancreatic (GEP) neuroendocrine tumor (NET) patients was assessed.

METHODS

A PBPK model was developed for [⁶⁸Ga]Ga-(HA-)DOTATATE in GEP-NET patients. Three tumor compartments were added, representing primary tumor, liver metastases and other metastases. Furthermore, reactions describing receptor binding, internalization and recycling, renal clearance and intracellular degradation were added to the model. Scan data from GEP-NET patients were used for evaluation of model predictions. Simulations with increasing tumor volumes were performed to assess the tumor sink effect.

RESULTS

Data of 39 and 59 patients receiving [⁶⁸Ga]Ga-DOTATATE and [⁶⁸Ga]Ga-HA-DOTATATE, respectively, were included. Evaluations showed that the model adequately described image-based patient data and that different receptor affinities caused organ uptake dissimilarities between both peptides. Sensitivity analysis indicated that tumor blood flow and blood volume impacted tumor distribution most. Tumor sink predictions showed a decrease in spleen uptake with increasing tumor volume, which seemed clinically relevant for patients with total tumor volumes higher than ~ 550 mL.

CONCLUSION

The developed PBPK model adequately predicted tumor and organ uptake for this GEP-NET population. Relevant organ uptake differences between [⁶⁸Ga]Ga-DOTATATE and [⁶⁸Ga]Ga-HA-DOTATATE were caused by different affinity profiles, while tumor uptake was mainly affected by tumor blood flow and blood volume. Furthermore, tumor sink predictions showed that for the majority of patients a tumor sink effect is not expected to be clinically relevant.

Effects of human tissue acoustic properties, abdominal wall shape, and respiratory motion on ultrasound-mediated hyperthermia for targeted drug delivery to pancreatic tumors

Background

PanDox is a Phase-1 trial of chemotherapeutic drug delivery to pancreatic tumors using ultrasound-mediated hyperthermia to release doxorubicin from thermally sensitive liposomes. This report describes trial-related hyperthermia simulations featuring: (i) new ultrasonic properties of human pancreatic tissues, (ii) abdomen deflections imposed by a water balloon, and (iii) respiration-driven organ motion.

Methods

Pancreas heating simulations were carried out using three patient body models. Pancreas acoustic properties were varied between values found in the literature and those determined from our human tissue study. Acoustic beam distortion was assessed with and without balloon-induced abdomen deformation. Target heating was assessed for static, normal respiratory, and jet-ventilation-controlled pancreas motion.

Results

Human pancreatic tumor attenuation is 63% of the literature values, so that pancreas treatments require commensurately higher input intensity to achieve adequate hyperthermia. Abdominal wall deformation decreased the peak field pressure by as much as 3.5 dB and refracted the focal spot by as much as 4.5 mm. These effects were thermally counteracted by sidelobe power deposition, so the net impact on achieving mild hyperthermia was small. Respiratory motion during moving beam hyperthermia produced localized regions overheated by more than 8.0 °C above the 4.0 °C volumetric goal. The use of jet ventilation reduced this excess to 0.7 °C and yielded temperature field uniformity that was nearly identical to having no respiratory motion.

Conclusion

Realistic modeling of the ultrasonic propagation environment is critical to achieving adequate mild hyperthermia without the use of real time thermometry for targeted drug delivery in pancreatic cancer patients.

Quantitative CT perfusion imaging in patients with pancreatic cancer: a systematic review

Pancreatic ductal adenocarcinoma (PDAC) is the third leading cause of cancer-related death with a 5-year survival rate of 10%. Quantitative CT perfusion (CTP) can provide additional diagnostic information compared to the limited accuracy of the current standard, contrast-enhanced CT (CECT). This systematic review evaluates CTP for diagnosis, grading, and treatment assessment of PDAC. The secondary goal is to provide an overview of scan protocols and perfusion models used for CTP in PDAC. The search strategy combined synonyms for 'CTP' and 'PDAC.' Pubmed, Embase, and Web of Science were systematically searched from January 2000 to December 2020 for studies using CTP to evaluate PDAC. The risk of bias was assessed using QUADAS-2. 607 abstracts were screened, of which 29 were selected for full-text eligibility. 21 studies were included in the final analysis with a total of 760 patients. All studies comparing PDAC with non-tumorous parenchyma found significant CTP-based differences in blood flow (BF) and blood volume (BV). Two studies found significant differences between pathological grades. Two other studies showed that BF could predict neoadjuvant treatment response. A wide variety in kinetic models and acquisition protocol was found among included studies. Quantitative CTP shows a potential benefit in PDAC diagnosis and can serve as a tool for pathological grading and treatment assessment; however, clinical evidence is still limited. To improve clinical use, standardized acquisition and reconstruction parameters are necessary for interchangeability of the perfusion parameters.

Computed tomography perfusion imaging evaluation of angiogenesis in patients with pancreatic adenocarcinoma

BACKGROUND

Pancreatic adenocarcinoma is one of the most common malignant tumors of the digestive system. More than 80% of patients with pancreatic adenocarcinoma are not diagnosed until late stage and have distant or local metastases.

AIM

To investigate the value of computed tomography (CT) perfusion imaging in the evaluation of angiogenesis in pancreatic adenocarcinoma patients.

METHODS

This is a retrospective cohort study. Patients with pancreatic adenocarcinoma and volunteers without pancreatic diseases underwent CT perfusion imaging from December 2014 to August 2017 in Huashan Hospital, Fudan University Shanghai, China.

RESULTS

A total number of 35 pancreatic adenocarcinoma patients and 33 volunteers were enrolled. The relative blood flow (rBF), and relative blood volume (rBV) were significantly lower in patients with pancreatic adenocarcinoma than in the control group (P < 0.05). Conversely, the relative permeability in patients with pancreatic adenocarcinoma was significantly higher than that in controls (P < 0.05). In addition, rBF, rBV, and the vascular maturity index (VMI) were significantly lower in grade III-IV pancreatic adenocarcinoma than in grade I-II pancreatic adenocarcinoma (P < 0.05). Vascular endothelial growth factor (VEGF), CD105-MVD, CD34-MVD, and angiogenesis rate (AR) were significantly higher in grade III-IV pancreatic adenocarcinoma than in grade I-II pancreatic adenocarcinoma (P < 0.05). Significant correlations between rBF and VEGF, CD105-MVD, AR, and VMI (P < 0.01) were observed. Moreover, the levels of rBV were statistically significantly correlated with those of VEGF, CD105-MVD, CD34-MVD, and VMI (P < 0.01).

CONCLUSION

Perfusion CT imaging may be an appropriate approach for quantitative assessment of tumor angiogenesis in pancreatic adenocarcinoma.

A Systematic Review on the Role of the Perfusion Computed Tomography in Abdominal Cancer

Background and purpose

Perfusion Computed Tomography (CTp) is an imaging technique which allows quantitative and qualitative evaluation of tissue perfusion through dynamic CT acquisitions. Since CTp is still considered a research tool in the field of abdominal imaging, the aim of this work is to provide a systematic summary of the current literature on CTp in the abdominal region to clarify the role of this technique for abdominal cancer applications.

Materials and Methods

A systematic literature search of PubMed, Web of Science, and Scopus was performed to identify original articles involving the use of CTp for clinical applications in abdominal cancer since 2011. Studies were included if they reported original data on CTp and investigated the clinical applications of CTp in abdominal cancer.

Results

Fifty-seven studies were finally included in the study. Most of the included articles (33/57) dealt with CTp at the level of the liver, while a low number of studies investigated CTp for oncologic diseases involving UGI tract (8/57), pancreas (8/57), kidneys (3/57), and colon–rectum (5/57).

Conclusions

Our study revealed that CTp could be a valuable functional imaging tool in the field of abdominal oncology, particularly as a biomarker for monitoring the response to anti-tumoral treatment.

Computed Tomography Perfusion Analysis of Pancreatic Adenocarcinoma using Deconvolution, Maximum Slope, and Patlak Methods - Evaluation of Diagnostic Accuracy and Interchangeability of Cut-Off Values

PURPOSE

 The goal of this study was to evaluate the diagnostic accuracy of perfusion computed tomography (CT) parameters obtained by different mathematical-kinetic methods for distinguishing pancreatic adenocarcinoma from normal tissue. To determine cut-off values and to assess the interchangeability of cut-off values, which were determined by different methods.

MATERIALS AND METHODS

 Perfusion CT imaging of the pancreas was prospectively performed in 23 patients. 19 patients with histopathologically confirmed pancreatic adenocarcinoma were included in the study. Blood flow (BF), blood volume (BV) and permeability-surface area product (PS) were measured in pancreatic adenocarcinoma and normal tissue with the deconvolution (BF, BV, PS), maximum slope (BF), and Patlak methods (BV, PS). The interchangeability of cut-off values was examined by assessing agreement between BF, BV, and PS measured with different mathematical-kinetic methods.

RESULTS

 Bland-Altman analysis demonstrated poor agreement between perfusion parameters, measured with different mathematical-kinetic methods. According to receiver operating characteristic (ROC) analysis, PS measured with the Patlak method had the significantly lowest diagnostic accuracy (area under ROC curve = 0.748). All other parameters were of high diagnostic accuracy (area under ROC curve = 0.940-0.997), although differences in diagnostic accuracy were not statistically different. Cut-off values for BF of ≤ 91.83 ml/100 ml/min and for BV of ≤ 5.36 ml/100 ml, both measured with the deconvolution method, appear to be the most appropriate cut-off values to distinguish pancreatic adenocarcinoma from normal tissue.

CONCLUSION

 Perfusion parameters obtained by different methods are not interchangeable. Therefore, cut-off values, which were determined using different methods, are not interchangeable either. Perfusion parameters can help to distinguish pancreatic adenocarcinoma from normal tissue with high diagnostic accuracy, except for PS measured with the Patlak method.

KEY POINTS

  · Perfusion CT parameters showed high diagnostic accuracy in differentiating between pancreatic adenocarcinoma and normal tissue.. · Only PS measured with the Patlak method showed a significantly lower diagnostic accuracy.. · Perfusion parameters measured with different mathematical-kinetic methods are not interchangeable.. · A specific cut-off value must be determined for each method and each perfusion parameter..

CITATION FORMAT

· Koell M, Klauss M, Skornitzke S et al. Computed Tomography Perfusion Analysis of Pancreatic Adenocarcinoma with the Deconvolution, Maximum Slope, and Patlak Methods - Evaluation of Diagnostic Accuracy and Interchangeability of Cut-Off Values. Fortschr Röntgenstr 2021; 193: 1062 - 1073.

Pancreatic perfusion imaging method that reduces radiation dose and maintains image quality by combining volumetric perfusion CT with multiphasic contrast enhanced-CT

OBJECTIVES

The aim of this study is to propose and evaluate a new method of volumetric perfusion computed tomography (PCT) incorporated into pancreatic multiphasic contrast enhanced (CE)-CT in the clinical setting.

METHODS

In this ethically approved study, PCT was incorporated into our existing scanning protocol in 17 patients and effective doses related to PCT were evaluated. CT values and signal-to-noise ratio (SNR) of anatomical structure were compared in diagnostic images that were acquired using 320-detector volumetric scan mode and 64-detector helical scan mode. In addition, focal lesion depiction was qualitatively assessed in the two groups. Perfusion parameters in normal pancreas were measured by two radiologists and the interobserver-reliability was assessed.

RESULTS

The effective dose of PCT was 5.1 ± 0.3 mSv. The actual effective dose (AED) including the dose used in volumetric scans for diagnostic imaging was 22.8 ± 5.3 mSv and the putative effective dose (PED) was 21.9 ± 9.1 mSv on average. There was no significant difference between AED and PED (p = 0.404). Compared with conventional helical scans, volumetric scans did not decrease CT values or SNR, but rather significantly increased those of the aorta in the arterial phase. Both groups had acceptable qualitatively assessed image quality with no significant difference in the depiction of each structure. There was almost perfect interobserver agreement in the measurement of perfusion parameters (mean ICCs > 0.9).

CONCLUSIONS

Our scanning protocol for pancreatic perfusion CT provides high-quality images while requiring lower radiation doses than conventional methods.

Bridging the gap between micro- and macro-scales in medical imaging with textural analysis - A biological basis for CT radiomics classifiers?

INTRODUCTION

Studies suggest there is utility in computed tomography (CT) radiomics for pancreatic disease; however, the precise biological interpretation of its features is unclear. In this manuscript, we present a novel approach towards this interpretation by investigating sub-micron tissue structure using digital pathology.

METHODS

A classification-to attenuation (CAT) function was developed and applied to digital pathology images to create sub-micron linear attenuation maps. From these maps, grey level co-occurrence matrix (GLCM) features were extracted and compared to pathology features. To simulate the spatial frequency loss in a CT scanner, the attenuation maps were convolved with a point spread function (PSF) and subsequently down-sampled. GLCM features were extracted from these down-sampled maps to assess feature stability as a function of spatial frequency loss.

RESULTS

Two GLCM features were shown to be strongly and positively correlated (r = 0.8) with underlying characteristics of the tumor microenvironment, namely percent pimonidazole staining in the tumor. All features underwent marked change as a function of spatial frequency loss; progressively larger spatial frequency losses resulted in progressively larger inter-tumor standard deviations; two GLCM features exhibited stability up to a 100 µm pixel size.

CONCLUSION

This work represents a necessary step towards understanding the biological significance of radiomics. Our preliminary results suggest that cellular metrics of pimonidazole-detectable hypoxia correlate with sub-micron attenuation coefficient texture; however, the consistency of these textures in face of spatial frequency loss is detrimental for robust radiomics. Further study in larger data sets may elucidate additional, potentially more robust features of biologic and clinical relevance.

Computed tomography perfusion study evaluating the curative effect of tibial transverse transport in patients with severe diabetic foot

Background

The clinical treatment of patients with severe diabetic foot (DF) is difficult. Recently, the First Affiliated Hospital of Guangxi Medical University began to apply tibial transverse transport (TTT) in patients with DF. This treatment has achieved significant effects, but its mechanism of action is unclear. Recently, microcirculation and the pathogenesis of diabetes have become the foci of research in this field. The evaluation of the possible mechanism of microcirculation reconstruction requires relevant indicators. The aim of this study was to investigate the value of computed tomography perfusion in evaluations of the curative effects of TTT and establish corresponding quantitative evaluation indicators.

Methods

Twelve patients with DF treated with TTT were recruited as the research participants. All diabetic feet were divided into the transport foot (TF) group and nontransport foot (NTF) group according to whether the patients underwent TTT. All patients underwent CT shuttle scanning preoperatively and 8 weeks after surgery. The shuttle scan data were transferred to Siemens VPCT body software and postprocessed with Customized Tumor2. We chose the TF posterior tibial artery from a distance of approximately 15 cm to the bifurcation of the plantar medial artery and the lateral plantar artery as the input artery. We selected the centre of the bilateral medial plantar muscle group on the coronal and axial regions of interest. We applied a deconvolution approach to obtain data from both sides of the plantar tissue perfusion. Skin temperature (ST) detection was performed with an ST gun to measure the average ST values in the dorsal and plantar areas, the first and fifth heads of the phalanges, and the medial and lateral malleolus points of both feet of patients with DF preoperatively and 8 weeks after surgery.

Results

The preoperative and postoperative ST values of the patients in the TF group were 30.73 ± 1.86 °C and 32.22 ± 1.51 °C, respectively. The preoperative and postoperative ST values for the patients in the NTF group were 30.93 ± 2.65 °C and 32.07 ± 2.09 °C, respectively. There were significant differences in the preoperative and postoperative data between the TF (P = 0.001) and NTF (P = 0.013) groups. In the patients with DF who underwent TTT, there were both preoperative and postoperative differences inside the medial plantar muscle group in the relative blood volume (rBV) value and relative mean transit time (rMTT) (P = 0.027, P = 0.026, respectively). The postoperative BV in the NTF group was increased compared with the preoperative BV (P = 0.006).

Conclusion

There were significant differences in relative BV, relative mean transit time, and ST between the two groups before and after surgery, and the postoperative BV in the NTF group and ST values in the two groups were increased compared with the preoperative values. The BV in the NTF group and the ST values in the two groups were effective indicators in evaluating the changes between preoperative and postoperative perfusion. These results indicate that TTT could increase plantar tissue perfusion as assessed by BV and ST; this increase was among the reasons for the surface healing of severe DF ulcers.

Translational potential of this article

Preoperative CT perfusion evaluation can provide relevant information of blood vessels and microcirculation for clinical operation, and postoperative CT perfusion evaluation can provide postoperative efficacy evaluation for clinical operation. All patients received information about the study and signed a specific informed consent. Approval for this study was granted by the regional ethics committee [Regional Ethics Committee of the First Affiliated Hospital of Guangxi Medical University, China [(2018-(KY-E-069].

Can Disturbed Liver Perfusion Revealed in p-CT on the First Day of Acute Pancreatitis Provide Information about the Expected Severity of the Disease?

Background

The aim of the study was to evaluate the prognostic properties of perfusion parameters of liver parenchyma based on computed tomography (CT) of patients with acute pancreatitis (AP) made on the first day of onset of symptoms, to assess their usefulness in identifying patients with increased risk of the development of severe AP.

Methods

79 patients with clinical symptoms and biochemical criteria indicative of AP underwent perfusion computed tomography (p-CT) within 24 hours after onset of the symptoms. Perfusion parameters in 41 people who developed a severe form of AP were compared with parameters in 38 patients in whom the course of AP was mild.

Results

Statistical differences in the liver perfusion parameters between the group of patients with mild and severe AP were shown. The permeability-surface area product was significantly lower, and the hepatic arterial fraction was significantly higher in the group of patients with progression of AP.

Conclusions

Based on the results, it seems that p-CT performed on the first day from the onset of AP is a method that, by revealing disturbances in hepatic perfusion, can help in identifying patients with increased risk of the development of severe AP.

Density and enhancement of the pancreatic tail on computer tomography predicts acinar score and pancreatic fistula after pancreatoduodenectomy

BACKGROUND

Acinar score calculated at the pancreatic resection margin is associated with postoperative pancreatic fistula (POPF) after pancreatoduodenectomy (PD). The present study evaluates the association between (i) computed tomography (CT) density of the pancreas and the acinar score of the pancreatic resection margin, and (ii) CT density of the pancreas and POPF after PD.

METHODS

Consecutive patients who underwent PD were included for analysis. CT densities of the pancreatic head, neck, body and tail were measured in non-contrast (NC), arterial (ART) and portal venous (PV) phases. Histologic slides of the pancreatic resection margin were scored for acinar cell density.

RESULTS

Ninety patients were included for analysis. Non-contrast density of the pancreatic tail was a good predictor of POPF (AUROC 0.704, p = 0.036), and a cut-off value of >40 Hounsfield units predicted POPF with 70.0% sensitivity and 73.4% specificity. The ratio of densities between PV and NC phases in the pancreatic tail was also a good predictor of POPF (AUROC 0.712, p = 0.030), and a cut-off value of <2.29 predicted POPF with 70.9% sensitivity and 80% specificity.

CONCLUSION

Non-contrast CT density of the pancreatic tail correlates with acinar cell density of the pancreatic resection margin and predicts the development of POPF after PD.

Intra- and interobserver reproducibility of pancreatic perfusion by computed tomography

The aim of this study was to measure intra- and interobserver agreement among radiologists in the assessment of pancreatic perfusion by computed tomography (CT). Thirty-nine perfusion CT scans were analyzed. The following parameters were measured by three readers: blood flow (BF), blood volume (BV), mean transit time (MTT) and time to peak (TTP). Statistical analysis was performed using the Bland-Altman method, linear mixed model analysis, and intraclass correlation coefficient (ICC). There was no significant intraobserver variability for the readers regarding BF, BV or TTP. There were session effects for BF in the pancreatic body and MTT in the pancreatic tail and whole pancreas. There were reader effects for BV in the pancreatic head, pancreatic body and whole pancreas. There were no effects for the interaction between session and reader for any perfusion parameter. ICCs showed substantial agreement for the interobserver measurements and moderate to substantial agreement for the intraobserver measurements, with the exception of MTT. In conclusion, satisfactory reproducibility of measurements was observed for TTP in all pancreatic regions, for BF in the head and BV in the tail, and these parameters seem to ensure a reasonable estimation of pancreatic perfusion.

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.

Contrast-enhanced ultrasonography of the pancreas shows impaired perfusion in pancreas insufficient cystic fibrosis patients

Background

Perfusion assessment of the pancreas is challenging and poorly evaluated. Pancreatic affection is a prevalent feature of cystic fibrosis (CF). Little is known about pancreatic perfusion in CF. We aimed to assess pancreatic perfusion by contrast-enhanced ultrasound (CEUS) analysed in the bolus-and-burst model and software.

Methods

We performed contrast enhanced ultrasound of the pancreas in 25 CF patients and 20 healthy controls. Perfusion data was analysed using a dedicated perfusion model providing the mean capillary transit-time (MTT), blood flow (BF) and blood-volume (BV). CF patients were divided according to exocrine function.

Results

The pancreas insufficient CF patients had longer MTT (p ≤ 0.002), lower BF (p < 0.001) and lower BV (p < 0.05) compared to the healthy controls and sufficient CF patients. Interrater analysis showed substantial agreement for the analysis of mean transit time.

Conclusion

The bolus-and-burst method used on pancreatic CEUS-examinations demonstrates reduced perfusion in CF patients with pancreas affection. The perfusion model and software requires further optimization and standardization to be clinical applicable for the assessment of pancreatic perfusion.

Electronic supplementary material

The online version of this article (10.1186/s12880-018-0259-3) contains supplementary material, which is available to authorized users.

Dynamic non-invasive ASL perfusion imaging of a normal pancreas with secretin augmented MR imaging

OBJECTIVES

To investigate prospectively the repeatability of pancreatic perfusion measurements using arterial spin labelling (ASL) and to determine the increase in perfusion due to secretin stimulation.

MATERIAL AND METHODS

An (FAIR)-TrueFISP ASL sequence was applied to determine the perfusion of the pancreatic head in a 3T MRI scanner. Ten healthy volunteers (four men, six women: mean age 28.5 ± 4.6 years; age range 25-40 years) were investigated twice within 1 week. The inter-individual variability was calculated using the standard deviation. Intra-individual agreement between the first and second scan was estimated using the Pearson correlation coefficient. A paired Wilcoxon rank-sum test was used to compare perfusion at baseline (BL) and during secretin stimulation.

RESULTS

The mean BL perfusion of the pancreatic head was 285 ± 96 mL/100 g/min with an intra-individual correlation coefficient of 0.67 (strong) for repeated measurements. Secretin stimulation led to a significant increase (by 81%) in perfusion of the pancreatic head to 486 ±156 mL/100 g/min (p=0.002) with an intra-individual correlation of 0.29 (weak). A return to BL values was observed after 239 ± 92 s with a moderate intra-individual correlation coefficient of 0.42 for repeat measurements.

CONCLUSION

Dynamic non-invasive ASL imaging of the pancreas permitted quantification of pancreatic perfusion in a clinically applicable setting.

KEY POINTS

• ASL imaging of the pancreas permitted quantification of pancreatic perfusion • Secretin stimulation led to a significant increase in pancreatic perfusion • The intra-individual correlation coefficient for baseline perfusion was strong for repeated measurements.

Theoretical investigation of transgastric and intraductal approaches for ultrasound-based thermal therapy of the pancreas

Background

The goal of this study was to theoretically investigate the feasibility of intraductal and transgastric approaches to ultrasound-based thermal therapy of pancreatic tumors, and to evaluate possible treatment strategies.

Methods

This study considered ultrasound applicators with 1.2 mm outer diameter tubular transducers, which are inserted into the tissue to be treated by an endoscopic approach, either via insertion through the gastric wall (transgastric) or within the pancreatic duct lumen (intraductal). 8 patient-specific, 3D, transient, biothermal and acoustic finite element models were generated to model hyperthermia (n = 2) and ablation (n = 6), using sectored (210°–270°, n = 4) and 360° (n = 4) transducers for treatment of 3.3–17.0 cm³ tumors in the head (n = 5), body (n = 2), and tail (n = 1) of the pancreas. A parametric study was performed to determine appropriate treatment parameters as a function of tissue attenuation, blood perfusion rates, and distance to sensitive anatomy.

Results

Parametric studies indicated that pancreatic tumors up to 2.5 or 2.7 cm diameter can be ablated within 10 min with the transgastric and intraductal approaches, respectively. Patient-specific simulations demonstrated that 67.1–83.3% of the volumes of four sample 3.3–11.4 cm³ tumors could be ablated within 3–10 min using transgastric or intraductal approaches. 55.3–60.0% of the volume of a large 17.0 cm³ tumor could be ablated using multiple applicator positions within 20–30 min with either transgastric or intraductal approaches. 89.9–94.7% of the volume of two 4.4–11.4 cm³ tumors could be treated with intraductal hyperthermia. Sectored applicators are effective in directing acoustic output away from and preserving sensitive structures. When acoustic energy is directed towards sensitive structures, applicators should be placed at least 13.9–14.8 mm from major vessels like the aorta, 9.4–12.0 mm from other vessels, depending on the vessel size and flow rate, and 14 mm from the duodenum.

Conclusions

This study demonstrated the feasibility of generating shaped or conformal ablative or hyperthermic temperature distributions within pancreatic tumors using transgastric or intraductal ultrasound.

Insulinoma Detection With MDCT: Is There a Role for Whole-Pancreas Perfusion?

OBJECTIVE

The purpose of this study is to investigate the role of whole-pancreas perfusion in detecting insulinomas with the use of MDCT.

MATERIALS AND METHODS

From January 2011 to December 2011, a total of 70 consecutive patients (33 men and 37 women; mean age, 46 years; range, 17-73 years) who underwent biphasic contrast-enhanced CT and whole-pancreas CT perfusion for suspected insulinomas were identified retrospectively. Patients were monitored for at least 3 years. Two radiologists who were blinded to the clinical and surgical data independently evaluated the images, first assessing only the biphasic contrast-enhanced CT images to detect tumor and assess diagnostic confidence on a 5-point scale. Next, perfusion parametric maps were evaluated and pancreatic perfusion parameters measured, and the presence of tumor was reidentified using a combination of the biphasic CT and perfusion image sets. A ROC curve was generated to compare the diagnostic accuracy of the two image sets.

RESULTS

The mean blood flow (BF) values of both the insulinomas and the insulinoma-harboring regions were statistically significantly higher (p < 0.01, for both) than the BF value of tumor-free pancreatic parenchyma. For the detection of insulinoma, biphasic CT had a sensitivity of 88.1%, a specificity of 85.7%, a positive predictive value of 91.1%, and a negative predictive value of 81.4%, whereas combined biphasic CT and perfusion had a sensitivity of 94.6%, a specificity of 94.7%, a positive predictive value of 96.7%, and a negative predictive value of 91.5%. The mean area under the ROC curve increased from 0.939 with biphasic CT to 0.999 with the addition of perfusion. Nine of 46 tumors (19.6%) for which findings were negative (n = 2) or indeterminate (n = 7) on biphasic CT were correctly diagnosed with the addition of perfusion.

CONCLUSION

The addition of pancreatic perfusion to biphasic contrast-enhanced CT may improve the detection of insulinomas.

Multidetector computer tomography in the pancreatic adenocarcinoma assessment: an update

Ductal adenocarcinoma of the pancreas is one of the most aggressive forms of cancer, with only a minority of cases being resectable at the moment of their diagnosis. The accurate detection and characterization of pancreatic carcinoma is very important for patient management. Multidetector-row computed tomography (MDCT) has become the cross-sectional modality of choice in the diagnosis, staging, treatment planning, and follow-up of patients with pancreatic tumors. However, approximately 11% of ductal adenocarcinomas still remain undetected at MDCT because of the lack of attenuation gradient between the lesion and the adjacent pancreatic parenchyma. In this systematic literature review we investigate the current evolution of the CT technique, limitations, and perspectives in the evaluation of pancreatic carcinoma.

Perfusion CT - Can it resolve the pancreatic carcinoma versus mass forming chronic pancreatitis conundrum?

OBJECTIVES

To evaluate the utility of perfusion CT (PCT) in differentiating pancreatic adenocarcinoma from mass forming chronic pancreatitis (MFCP).

METHODS

In this ethically approved study, PCT was performed in 122 patients with pancreatic masses of which 42 patients had pancreatic adenocarcinoma and 13 had MFCP on histopathology. Perfusion parameters studied included blood flow (BF), blood volume (BV), permeability surface area product (PS), time to peak (TTP), peak enhancement intensity (PEI) and mean transit time (MTT). Twenty five controls with no pancreatic pathology were also studied.

RESULTS

Amongst the perfusion parameters BF and BV were found to be the most reliable for differentiating between adenocarcinoma and mass forming pancreatitis. Although they were reduced in both pancreatic adenocarcinoma (BF- 16.6 ± 13.1 ml/100 ml/min and BV- 5 ± 3.5 ml/100 ml) and MFCP (BF- 30.4 ± 8.7 ml/100 ml/min and BV- 8.9 ± 3.1 ml/100 ml) as compared to normal controls (BF- 94.1 ± 24 ml/100 ml/min and BV- 36 ± 10.7 ml/100 ml) but the extent of reduction was greater in pancreatic adenocarcinoma than in MFCP. Based on ROC analysis cut off values of 19.1 ml/100 ml/min for BF and 5 ml/100 ml for BV yielded optimal sensitivity and specificity for differentiating pancreatic adenocarcinoma from MFCP.

CONCLUSIONS

PCT may serve as an additional paradigm for differentiating pancreatic adenocarcinoma from mass forming chronic pancreatitis and a useful tool for detecting masses which are isodense on conventional CT.

Imaging approaches to assess the therapeutic response of gastroenteropancreatic neuroendocrine tumors (GEP-NETs): current perspectives and future trends of an exciting field in development

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are a family of neoplasms with a complex spectrum of clinical behavior. Although generally more indolent than carcinomas, once they progress beyond surgical resectability, they are essentially incurable. Systemic treatment options have substantially expanded in recent years for the management of advanced disease. Imaging plays a major role in new drug development, as it is the main tool used to objectively evaluate response to novel agents. However, current standard response criteria have proven suboptimal for the assessment of the antiproliferative effect of many targeted agents, particularly in the context of slow-growing tumors such as well-differentiated NETs. The aims of this article are to discuss the advantages and limitations of conventional radiological techniques and standard response assessment criteria and to review novel imaging modalities in development as well as alternative cancer- and therapy-specific criteria to assess drug efficacy in the field of GEP-NETs.

Dynamic Contrast-Enhanced CT in Patients with Pancreatic Cancer

The aim of this systematic review is to provide an overview of the use of Dynamic Contrast-enhanced Computed Tomography (DCE-CT) in patients with pancreatic cancer. This study was composed according to the PRISMA guidelines 2009. The literature search was conducted in PubMed, Cochrane Library, EMBASE, and Web of Science databases to identify all relevant publications. The QUADAS-2 tool was implemented to assess the risk of bias and applicability concerns of each included study. The initial literature search yielded 483 publications. Thirteen articles were included. Articles were categorized into three groups: nine articles concerning primary diagnosis or staging, one article about tumor response to treatment, and three articles regarding scan techniques. In exocrine pancreatic tumors, measurements of blood flow in eight studies and blood volume in seven studies were significantly lower in tumor tissue, compared with measurements in pancreatic tissue outside of tumor, or normal pancreatic tissue in control groups of healthy volunteers. The studies were heterogeneous in the number of patients enrolled and scan protocols. Perfusion parameters measured and analyzed by DCE-CT might be useful in the investigation of characteristic vascular patterns of exocrine pancreatic tumors. Further clinical studies are desired for investigating the potential of DCE-CT in pancreatic tumors.

Thermal therapy of pancreatic tumours using endoluminal ultrasound: Parametric and patient-specific modelling

PURPOSE

The aim of this study is to investigate endoluminal ultrasound applicator configurations for volumetric thermal ablation and hyperthermia of pancreatic tumours using 3D acoustic and biothermal finite element models.

MATERIALS AND METHODS

Parametric studies compared endoluminal heating performance for varying applicator transducer configurations (planar, curvilinear-focused, or radial-diverging), frequencies (1-5 MHz), and anatomical conditions. Patient-specific pancreatic head and body tumour models were used to evaluate feasibility of generating hyperthermia and thermal ablation using an applicator positioned in the duodenal or stomach lumen. Temperature and thermal dose were calculated to define ablation (> 240 EM(43 °C)) and moderate hyperthermia (40-45 °C) boundaries, and to assess sparing of sensitive tissues. Proportional-integral control was incorporated to regulate maximum temperature to 70-80 °C for ablation and 45 °C for hyperthermia in target regions.

RESULTS

Parametric studies indicated that 1-3 MHz planar transducers are the most suitable for volumetric ablation, producing 5-8 cm(3) lesion volumes for a stationary 5-min sonication. Curvilinear-focused geometries produce more localised ablation to 20-45 mm depth from the GI tract and enhance thermal sparing (T(max) < 42 °C) of the luminal wall. Patient anatomy simulations show feasibility in ablating 60.1-92.9% of head/body tumour volumes (4.3-37.2 cm(3)) with dose < 15 EM(43 °C) in the luminal wall for 18-48 min treatment durations, using 1-3 applicator placements in GI lumen. For hyperthermia, planar and radial-diverging transducers could maintain up to 8 cm(3) and 15 cm(3) of tissue, respectively, between 40-45 °C for a single applicator placement.

CONCLUSIONS

Modelling studies indicate the feasibility of endoluminal ultrasound for volumetric thermal ablation or hyperthermia treatment of pancreatic tumour tissue.

Perfusion-CT--Can We Predict Acute Pancreatitis Outcome within the First 24 Hours from the Onset of Symptoms?

PURPOSE

Severe acute pancreatitis (AP) is still a significant clinical problem which is associated with a highly mortality. The aim of this study was the evaluation of prognostic value of CT regional perfusion measurement performed on the first day of onset of symptoms of AP, in assessing the risk of developing severe form of acute pancreatitis.

MATERIAL AND METHODS

79 patients with clinical symptoms and biochemical criteria indicative of acute pancreatitis (acute upper abdominal pain, elevated levels of serum amylase and lipase) underwent perfusion CT within 24 hours after onset of symptoms. The follow-up examinations were performed after 4-6 days to detect progression of the disease. Perfusion parameters were compared in 41 people who developed severe form of AP (pancreatic and/or peripancreatic tissue necrosis) with parameters in 38 consecutive patients in whom course of AP was mild. Blood flow, blood volume, mean transit time and permeability surface area product were calculated in the three anatomic pancreatic subdivisions (head, body and tail). At the same time the patient's clinical status was assessed by APACHE II score and laboratory parameters such as CRP, serum lipase and amylase, AST, ALT, GGT, ALP and bilirubin were compared.

RESULTS

Statistical differences in the perfusion parameters between the group of patients with mild and severe AP were shown. Blood flow, blood volume and mean transit time were significantly lower and permeability surface area product was significantly higher in patients who develop severe acute pancreatitis and presence of pancreatic and/or peripancreatic necrosis due to pancreatic ischemia. There were no statistically significant differences between the two groups in terms of evaluated on admission severity of pancreatitis assessed using APACHE II score and laboratory tests.

CONCLUSIONS

CT perfusion is a very useful indicator for prediction and selection patients in early stages of acute pancreatitis who are at risk of developing pancreatic and/or peripancreatic necrosis already on the first day of the onset of symptoms and can be used for treatment planning and monitoring of therapy of acute pancreatitis. Early suspicion of possible pancreatic necrosis both on the basis of scores based on clinical status and laboratory tests have low predictive value.

Perfusion CT: can it predict the development of pancreatic necrosis in early stage of severe acute pancreatitis?

PURPOSE

Pancreatic necrosis is an important determinant of patient outcome in severe acute pancreatitis (SAP). This prospective study was conducted to evaluate if perfusion CT (PCT) can predict the development of necrosis at an early stage in SAP.

METHODS

PCT was performed within 72 h of abdominal pain in 57 consecutive admitted patients of acute pancreatitis, out of which four patients were excluded. Thirty-two patients were classified as SAP and 21 as mild acute pancreatitis (MAP) on the basis of APACHE II or SIRS criteria or presence of organ failure. All patients underwent a follow-up CECT at 3 weeks to look for pancreatic necrosis.

RESULTS

Out of 32 patients of SAP, 14 patients showed perfusion defects. The mean blood flow (BF) in these areas was 11.47 ± 5.56 mL/100 mL/min and median blood volume (BV) was 3.92 mL/100 mL (0.5-8.49 mL/100 mL). All these patients developed necrosis on follow-up scan. Two patients who did not show perfusion defects also developed necrosis. Remaining 37 patients (16 SAP and 21 MAP) did not show perfusion defect and did not develop necrosis on follow-up. All regions showing BF less than ≤23.45 mL/100 mL/min and BV ≤8.49 mL/100 mL developed pancreatic necrosis. The values of perfusion parameters may vary with the scanner, mathematical model and protocol used. The sensitivity and specificity of PCT for predicting pancreatic necrosis were 87.5% and 100%, respectively. The cut off values of BF and BV for predicting the development of pancreatic necrosis were 27.29 mL/100 mL/min and 8.96 mL/100 mL, respectively, based on ROC curve. PCT is a reliable tool for early prediction of pancreatic necrosis, which may open new avenues to prevent this ominous complication.

Reproducibility of VPCT parameters in the normal pancreas: comparison of two different kinetic calculation models

RATIONALE AND OBJECTIVES

To assess the reproducibility of volume computed tomographic perfusion (VPCT) measurements in normal pancreatic tissue using two different kinetic perfusion calculation models at three different time points.

MATERIALS AND METHODS

Institutional ethical board approval was obtained for retrospective analysis of pancreas perfusion data sets generated by our prospective study for liver response monitoring to local therapy in patients experiencing unresectable hepatocellular carcinoma, which was approved by the institutional review board. VPCT of the entire pancreas was performed in 41 patients (mean age, 64.8 years) using 26 consecutive volume measurements and intravenous injection of 50 mL of iodinated contrast at a flow rate of 5 mL/s. Blood volume(BV) and blood flow (BF) were calculated using two mathematical methods: maximum slope + Patlak analysis versus deconvolution method. Pancreas perfusion was calculated using two volume of interests. Median interval between the first and the second VPCT was 2 days and between the second and the third VPCT 82 days. Variability was assessed with within-patient coefficients of variation (CVs) and Bland-Altman analyses. Interobserver agreement for all perfusion parameters was calculated using intraclass correlation coefficients (ICCs).

RESULTS

BF and BV values varied widely by method of analysis as did within-patient CVs for BF and BV at the second versus the first VPCT by 22.4%/50.4% (method 1) and 24.6%/24.0% (method 2) measured in the pancreatic head and 18.4%/62.6% (method 1) and 23.8%/28.1% (method 2) measured in the pancreatic corpus and at the third versus the first VPCT by 21.7%/61.8% (method 1) and 25.7%/34.5% (method 2) measured also in the pancreatic head and 19.1%/66.1% (method 1) and 22.0%/31.8% (method 2) measured in the pancreatic corpus, respectively. Interobserver agreement measured with ICC shows fair-to-good reproducibility.

CONCLUSIONS

VPCT performed with the presented examinational protocol is reproducible and can be used for monitoring purposes. Best reproducibility was obtained with both methods for BF and with method 2 also for BV data for both follow-up studies.

Perfusion CT estimates photosensitizer uptake and biodistribution in a rabbit orthotopic pancreatic cancer model: a pilot study

RATIONALE AND OBJECTIVES

It was hypothesized that perfusion computed tomography (CT), blood flow (BF), blood volume (BV), and vascular permeability surface area (PS) product parameters would be predictive of therapeutic anticancer agent uptake in pancreatic cancer, facilitating image-guided interpretation of human treatments. The hypothesis was tested in an orthotopic rabbit model of pancreatic cancer, by establishing the model, imaging with endoscopic ultrasound (EUS) and contrast CT, and spatially comparing the perfusion maps to the ex vivo uptake values of the injected photosensitizer, verteporfin.

MATERIALS AND METHODS

Nine New Zealand white rabbits underwent direct pancreas implantation of VX2 tumors, and CT perfusion or EUS was performed 10 days postimplantation. Verteporfin was injected during CT imaging, and the tissue was removed 1 hour postinjection for frozen tissue fluorescence scanning. Region-of-interest comparisons of CT data with ex vivo fluorescence and histopathologic staining were performed.

RESULTS

Dynamic contrast-enhanced CT showed enhanced BF, BV, and PS in the tumor rim and decreased BF, BV, and PS in the tumor core. Significant correlations were found between ex vivo verteporfin concentration and each of BF, BV, and PS.

CONCLUSIONS

The efficacy of verteporfin delivery in tumors is estimated by perfusion CT, providing a noninvasive method of mapping photosensitizer dose.

Temporal assessment of pancreatic blood flow and perfusion following secretin stimulation using noninvasive MRI

PURPOSE

To dynamically quantify pancreatic perfusion and flow within the arteries supplying the pancreas in response to secretin stimulation.

MATERIALS AND METHODS

Twelve healthy male subjects were scanned at 1.5T with arterial spin labeling to measure tissue perfusion and phase contrast magnetic resonance imaging (MRI) to measure vessel flow. Superior mesenteric (SMA), gastroduodenal (GDA), common hepatic (HA), and splenic (SA) arterial flow and pancreatic perfusion were serially measured for 50 minutes following 1 IU/kg intravenous secretin. The significance of differences between timepoints was tested using a repeated measures one-way analysis of variance (ANOVA).

RESULTS

Baseline blood flow (mean ± SEM or median [IQR]) for SMA, HA, SA, and GDA was 7.6 ± 1.3, 4.0 ± 0.5, 8.2 ± 0.8, and 0.9 (0.8-1.4) ml/s, respectively. Baseline pancreatic perfusion was 200 ± 25 ml/100g/min. Blood flow increased in the SMA (234%, P < 0.0001) and GDA (155%, P = 0.015) immediately after secretin injection. Reduced HA blood flow was observed after 10 minutes (P = 0.066) with no change in SA flow (P = 0.533). Increased pancreatic perfusion was maintained for 40 minutes after injection with a maximal increase at 5 minutes (16.8%, P = 0.025).

CONCLUSION

Intravenous secretin resulted in significant temporal changes in pancreatic perfusion and arterial blood flow.

Quantitative contrast-enhanced ultrasonographic assessment of naturally occurring pancreatitis in dogs

BACKGROUND

Quantitative contrast-enhanced ultrasonography (CEUS) can detect pancreatic perfusion changes in experimentally induced canine pancreatitis. However, its usefulness in detecting perfusion changes in naturally occurring pancreatitis is unclear.

HYPOTHESIS/OBJECTIVES

To determine the feasibility of using CEUS to detect pancreatic and duodenal perfusion changes in naturally occurring canine pancreatitis.

ANIMALS

Twenty-three client-owned dogs with pancreatitis, 12 healthy control dogs.

METHODS

Dogs diagnosed with pancreatitis were prospectively included. CEUS of the pancreas and duodenum were performed. Time-intensity curves were created from regions of interest in the pancreas and duodenum. Five perfusion parameters were obtained for statistical analyses: time to initial up-slope, peak time (Tp), time to wash-out (TTW), peak intensity (PI), and area under the curve (AUC).

RESULTS

For the pancreas, Tp of the pancreatitis group was prolonged when compared to controls (62 ± 11 seconds versus 39 ± 13 seconds; P < .001). TTW also was prolonged but not significantly (268 ± 69 seconds versus 228 ± 47 seconds; P = .47). PI and AUC were increased when compared to controls (95 ± 15 versus 78 ± 13 MPV; P = .009 and 14,900 ± 3,400 versus 11,000 ± 2,800 MPV*s; P = .013, respectively). For the duodenum, PI and AUC were significantly increased in the pancreatitis group when compared to controls.

CONCLUSIONS AND CLINICAL IMPORTANCE

Contrast-enhanced ultrasonography can detect pancreatic perfusion changes in naturally occurring canine pancreatitis characterized by delayed peak with prolonged hyperechoic enhancement of the pancreas on CEUS. Additionally, duodenal perfusion changes secondary to pancreatitis were observed.

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.

A solid pancreatic mass: tumour or inflammation?

The prognosis for pancreatic cancer is poor, and early diagnosis is essential for surgical management. By comparison with its classic form, the presence of acute or chronic inflammatory signs will hinder its detection and delay its diagnosis. The atypical forms of acute pancreatitis need to be known in order to detect patients who require additional morphological investigations to search for an underlying tumour. In contrast, pseudotumoral forms of inflammation (chronic pancreatitis, cystic dystrophy in heterotopic pancreas, autoimmune pancreatitis) may simulate a cancer, and make up 5-10% of the surgical procedures for suspected cancer. Faced with these pseudotumoral masses, interpretation relies on various differentiating signs and advances in imaging.

Solid pancreatic lesions: characterization by using timing bolus dynamic contrast-enhanced MR imaging assessment--a preliminary study

PURPOSE

To assess the feasibility of postprocessing dynamic contrast material-enhanced (DCE) magnetic resonance (MR) imaging timing bolus data by using a three-dimensional radial gradient-echo technique with k-space-weighted image contrast (KWIC) for the characterization of solid pancreatic diseases.

MATERIALS AND METHODS

This retrospective study was approved by the institutional review board, and informed consent was waived. A total of 45 patients suspected of having biliary or pancreatic disease underwent pancreatic MR examination with a 3.0-T imager with a low-dose (2 mL gadopentetate dimeglumine) timing bolus by using the radial KWIC technique. There were 24 patients with pancreatic cancers, eight with pancreatic neuroendocrine tumors (PNETs), three with chronic pancreatitis, and 10 with a normal pancreas. By using a dedicated postprocessing software program for DCE MR imaging, the following perfusion parameters were measured for tumor and nontumorous parenchyma: volume transfer coefficient (K(trans)) and extracellular extravascular volume fraction; the rate constant (k(ep)) and initial area under the concentration curve in 60 seconds (iAUC) were then generated. The perfusion parameters acquired on DCE MR images were compared among the groups by using the analysis of variance test.

RESULTS

K(trans), k(ep), and iAUC values in patients with pancreatic cancer (0.042 min(-1) ± 0.023 [standard deviation], 0.761 min(-1) ± 0.529, and 2.841 mmol/sec ± 1.811, respectively) were significantly lower than in patients with a normal pancreas (0.387 min(-1) ± 0.176, 6.376 min(-1) ± 2.529, and 7.156 mmol/sec ± 3.414, respectively) (P < .05 for all). In addition, k(ep) values of PNETs and normal pancreas also differed (P < .0001), and K(trans), k(ep), and iAUC values of pancreatic cancers and PNETs differed significantly (P < .0001, P = .038, and P < .0001, respectively).

CONCLUSION

Results of timing bolus DCE MR imaging with the radial KWIC sequence from routine examinations can be postprocessed to yield potentially useful perfusion parameters for the characterization of pancreatic diseases.

Empirical mathematical model for dynamic manganese-enhanced MRI of the murine pancreas for assessment of β-cell function

Autoimmune ablation of pancreatic β-cells and alteration of its microvasculature may be a predictor of Type I diabetes development. A dynamic manganese-enhanced MRI (MEMRI) approach and an empirical mathematical model were developed to monitor whole pancreatic β-cell function and vasculature modifications in mice. Normal and streptozotocin-induced diabetic FVB/N mice were imaged on a 9.4T MRI system using a 3D magnetization prepared rapid acquisition gradient echo pulse sequence to characterize low dose manganese kinetics in the pancreas head, body and tail. Average signal enhancement in the pancreas (head, body, and tail) as a function of time was fit by a novel empirical mathematical model characterizing contrast uptake/washout rates and yielding parameters describing peak signal, initial slope, and initial area under the curve. Signal enhancement from glucose-induced manganese uptake was fit by a linear function. The results demonstrated that the diabetic pancreatic tail had a significantly lower contrast uptake rate, smaller initial slope/initial area under the curve, and a smaller rate of Mn uptake following glucose activation (p<0.05) compared to the normal pancreatic tail. These observations parallel known patterns of β-cell loss and alteration in supportive vasculature associated with diabetes. Dynamic MEMRI is a promising technique for assessing β-cell functionality and vascular perfusion with potential applications for monitoring diabetes progression and/or therapy.