Effectiveness of magnetic resonance imaging and spiral computed tomography in the staging and treatment prognosis of colorectal cancer

BACKGROUND Colorectal cancer(CRC)is a prevalent cancer type in clinical settings;its early signs can be difficult to detect,which often results in late-stage diagnoses in many patients.The early detection and diagnosis of CRC are crucial for improving treatment success and patient survival rates.Recently,imaging techniques have been hypothesized to be essential in managing CRC,with magnetic resonance imaging(MRI)and spiral computed tomography(SCT)playing a significant role in enhancing diagnostic and treatment approaches.AIM To explore the effectiveness of MRI and SCT in the preoperative staging of CRC and the prognosis of laparoscopic treatment.METHODS Ninety-five individuals admitted to Zhongshan Hospital Xiamen University underwent MRI and SCT and were diagnosed with CRC.The precision of MRI and SCT for the presurgical classification of CRC was assessed,and pathological staging was used as a reference.Receiver operating characteristic curves were used to evaluate the diagnostic efficacy of blood volume,blood flow,time to peak,permeability surface,blood reflux constant,volume transfer constant,and extracellular extravascular space volume fraction on the prognosis of patients with CRC.RESULTS Pathological biopsies confirmed the following CRC stages:23,23,32,and 17 at T1,T2,T3,and T4,respectively.There were 39 cases at the N0 stage,22 at N1,34 at N2,44 at M0 stage,and 51 at M1.Using pathological findings as the benchmark,the combined use of MRI and SCT for preoperative TNM staging in patients with CRC demonstrated superior sensitivity,specificity,and accuracy compared with either modality alone,with a statistically significant difference in accuracy(P<0.05).Receiver operating characteristic curve analysis revealed the predictive values for laparoscopic treatment prognosis,as indicated by the areas under the curve for blood volume,blood flow,time to peak,and permeability surface,blood reflux constant,volume transfer constant,and extracellular extravascular space volume fraction were 0.750,0.683,0.772,0.761,0.709,0.719,and 0.910,respectively.The corresponding sensitivity and specificity values were also obtained(P<0.05).CONCLUSION MRI with SCT is effective in the clinical diagnosis of patients with CRC and is worthy of clinical promotion.

Artificial Intelligence-Based Image Reconstruction for Computed Tomography: A Survey

Computed tomography has made significant advances since its intro-duction in the early 1970s,where researchers have mainly focused on the quality of image reconstruction in the early stage.However,radiation exposure poses a health risk,prompting the demand of the lowest possible dose when carrying out CT examinations.To acquire high-quality reconstruction images with low dose radiation,CT reconstruction techniques have evolved from conventional reconstruction such as analytical and iterative reconstruction,to reconstruction methods based on artificial intelligence(AI).All these efforts are devoted to con-structing high-quality images using only low doses with fast reconstruction speed.In particular,conventional reconstruction methods usually optimize one aspect,while AI-based reconstruction has finally managed to attain all goals in one shot.However,there are limitations such as the requirements on large datasets,unstable performance,and weak generalizability in AI-based reconstruction methods.This work presents the review and discussion on the classification,the commercial use,the advantages,and the limitations of AI-based image reconstruction methods in CT.

A machine learning-based strategy for predicting the mechanical strength of coral reef limestone using X-ray computed tomography

Different sedimentary zones in coral reefs lead to significant anisotropy in the pore structure of coral reef limestone(CRL),making it difficult to study mechanical behaviors.With X-ray computed tomography(CT),112 CRL samples were utilized for training the support vector machine(SVM)-,random forest(RF)-,and back propagation neural network(BPNN)-based models,respectively.Simultaneously,the machine learning model was embedded into genetic algorithm(GA)for parameter optimization to effectively predict uniaxial compressive strength(UCS)of CRL.Results indicate that the BPNN model with five hidden layers presents the best training effect in the data set of CRL.The SVM-based model shows a tendency to overfitting in the training set and poor generalization ability in the testing set.The RF-based model is suitable for training CRL samples with large data.Analysis of Pearson correlation coefficient matrix and the percentage increment method of performance metrics shows that the dry density,pore structure,and porosity of CRL are strongly correlated to UCS.However,the P-wave velocity is almost uncorrelated to the UCS,which is significantly distinct from the law for homogenous geomaterials.In addition,the pore tensor proposed in this paper can effectively reflect the pore structure of coral framework limestone(CFL)and coral boulder limestone(CBL),realizing the quantitative characterization of the heterogeneity and anisotropy of pore.The pore tensor provides a feasible idea to establish the relationship between pore structure and mechanical behavior of CRL.

Chronic pancreatitis:Pain and computed tomography/magnetic resonance imaging findings

Chronic pancreatitis(CP)is a fibroinflammatory disease characterized by irreversible destruction of pancreatic tissue.With the development of the disease,it may lead to exocrine and/or endocrine insufficiency.CP is one of the common diseases that cause abdominal pain,which will not get permanent spontaneous relief as the disease evolves.The American College of Gastroenterology clinical guidelines recommend computed tomography or magnetic resonance imaging as the first-line examination for the diagnosis of CP.CP common imaging findings include pancreatic atrophy,irregular dilatation of the pancreatic duct,calcification of pancreatic parenchyma,pancreatic duct stones,etc.In clinical practice,whether any correlations between CP-induced abdominal pain patterns(no pain/constant/intermittent pain)and corresponding imaging findings present are not well known.Therefore,this review aims to comprehensively sort out and analyze the relevant information by collecting lots of literature on this field,so as to construct a cross-bridge between the clinical manifestations and imaging manifestations of CP patients.Also,it provides an imaging basis and foundation for the classification and diagnosis of abdominal pain types in clinical CP patients.

Extravasated contrast volumetric assessment on computed tomography angiography in gastrointestinal bleeding:A useful predictor of positive angiographic findings

BACKGROUND Gastrointestinal bleeding(GIB)is a severe and potentially life-threatening condition,especially in cases of delayed treatment.Computed tomography angiography(CTA)plays a pivotal role in the early identification of upper and lower GIB and in the prompt treatment of the haemorrhage.AIM To determine whether a volumetric estimation of the extravasated contrast at CTA in GIB may be a predictor of subsequent positive angiographic findings.METHODS In this retrospective single-centre study,35 patients(22 men;median age 69 years;range 16-92 years)admitted to our institution for active GIB detected at CTA and further submitted to catheter angiography between January 2018 and February 2022 were enrolled.Twenty-three(65.7%)patients underwent endoscopy before CTA.Bleeding volumetry was evaluated in both arterial and venous phases via a semi-automated dedicated software.Bleeding rate was obtained from volume change between the two phases and standardised for unit time.Patients were divided into two groups,according to the angiographic signs and their concordance with CTA.RESULTS Upper bleeding accounted for 42.9%and lower GIB for 57.1%.Mean haemoglobin value at the admission was 7.7 g/dL.A concordance between positive CTA and direct angiographic bleeding signs was found in 19(54.3%)cases.Despite no significant differences in terms of bleeding volume in the arterial phase(0.55 mL vs 0.33 mL,P=0.35),a statistically significant volume increase in the venous phase was identified in the group of patients with positive angiography(2.06 mL vs 0.9 mL,P=0.02).In the latter patient group,a significant increase in bleeding rate was also detected(2.18 mL/min vs 0.19 mL/min,P=0.02).CONCLUSION In GIB of any origin,extravasated contrast volumetric analysis at CTA could be a predictor of positive angiography and may help in avoiding further unnecessary procedures.

Biliary complications after liver transplantation:A computed tomography and magnetic resonance imaging pictorial review

Biliary complications are the most common complications after liver transplantation.Computed tomography(CT)and magnetic resonance imaging(MRI)are cornerstones for timely diagnosis of biliary complications after liver transplantation.The diagnosis of these complications by CT and MRI requires expertise,mainly with respect to identifying subtle early signs to avoid missed or incorrect diagnoses.For example,biliary strictures may be misdiagnosed on MRI due to size mismatch of the common ducts of the donor and recipient,postoperative edema,pneumobilia,or susceptibility artifacts caused by surgical clips.Proper and prompt diagnosis of biliary complications after transplantation allows the timely initiation of appropriate management.The aim of this pictorial review is to illustrate various CT and MRI findings related to biliary complications after liver transplantation,based on time of presentation after surgery and frequency of occurrence.

Surgical complications after pancreatic transplantation:A computed tomography imaging pictorial review

Pancreatic transplantation is considered by the American Diabetes Association and the European Association for the Study of Diabetes an acceptable surgical procedure in patients with type 1 diabetes also undergoing kidney transplantation in pre-final or end-stage renal disease if no contraindications are present.Pancreatic transplantation,however,is a complex surgical procedure and may lead to a range of postoperative complications that can significantly impact graft function and patient outcomes.Postoperative computed tomography(CT)is often adopted to evaluate perfusion of the transplanted pancreas,identify complications and as a guide for interventional radiology procedures.CT assessment after pancreatic transplantation should start with the evaluation of the arterial Y-graft,the venous anastomosis and the duodenojejunostomy.With regard to complications,CT allows for the identification of vascular complications,such as thrombosis or stenosis of blood vessels supplying the graft,the detection of pancreatic fluid collections,including pseudocysts,abscesses,or leaks,the assessment of bowel complications(anastomotic leaks,ileus or obstruction),and the identification of bleeding.The aim of this pictorial review is to illustrate CT findings of surgical-related complications after pancreatic transplantation.The knowledge of surgical techniques is of key importance to understand postoperative anatomic changes and imaging evaluation.Therefore,we first provide a short summary of the main techniques of pancreatic transplantation.Then,we provide a practical imaging approach to pancreatic transplantation and its complications providing tips and tricks for the prompt imaging diagnosis on CT.

Impact of random and scattered coincidences from outside of field of view on positron emission tomography/computed tomography imaging with different reconstruction protocols

Image quality in positron emission tomography(PET)is affected by random and scattered coincidences and reconstruction protocols.In this study,we investigated the effects of scattered and random coincidences from outside the field of view(FOV)on PET image quality for different reconstruction protocols.Imaging was performed on the Discovery 690 PET/CT scanner,using experimental configurations including the NEMA phantom(a body phantom,with six spheres of different sizes)with a signal background ratio of 4:1.The NEMA phantom(phantom I)was scanned separately in a one-bed position.To simulate the effect of random and scatter coincidences from outside the FOV,six cylindrical phantoms with various diameters were added to the NEMA phantom(phantom II).The 18 emission datasets with mean intervals of 15 min were acquired(3 min/scan).The emission data were reconstructed using different techniques.The image quality parameters were evaluated by both phantoms.Variations in the signal-to-noise ratio(SNR)in a 28-mm(10-mm)sphere of phantom II were 37.9%(86.5%)for ordered-subset expectation maximization(OSEM-only),36.8%(81.5%)for point spread function(PSF),32.7%(80.7%)for time of flight(TOF),and 31.5%(77.8%)for OSEM+PSF+TOF,respectively,indicating that OSEM+PSF+TOF reconstruction had the lowest noise levels and lowest coefficient of variation(COV)values.Random and scatter coincidences from outside the FOV induced lower SNR,lower contrast,and higher COV values,indicating image deterioration and significantly impacting smaller sphere sizes.Amongst reconstruction protocols,OSEM+PSF+TOF and OSEM+PSF showed higher contrast values for sphere sizes of 22,28,and 37 mm and higher contrast recovery coefficient values for smaller sphere sizes of 10 and 13 mm.

An algorithm for computed tomography image reconstruction from limited-view projections

With the development of the compressive sensing theory, the image reconstruction from the projections viewed in limited angles is one of the hot problems in the research of computed tomography technology. This paper develops an iterative algorithm for image reconstruction, which can fit the most cases. This method gives an image reconstruction flow with the difference image vector, which is based on the concept that the difference image vector between the reconstructed and the reference image is sparse enough. Then the l1-norm minimization method is used to reconstruct the difference vector to recover the image for flat subjects in limited angles. The algorithm has been tested with a thin planar phantom and a real object in limited-view projection data. Moreover, all the studies showed the satisfactory results in accuracy at a rather high reconstruction speed.

Monochromatic energy computed tomography image for active intestinal hemorrhage:A model investigation

AIM: To investigate the value of computed tomography(CT) spectral imaging in the evaluation of intestinal hemorrhage.METHODS: Seven blood flow rates were simulated in vitro.Energy spectral CT and mixed-energy CT scanswere performed for each rate(0.5,0.4,0.3,0.2,0.1,0.05 and 0.025 m L/min).The detection rates and the contrast-to-noise ratios(CNRs) of the contrast agent extravasation regions were compared between the two scanning methods in the arterial phase(AP) and the portal venous phase(PVP).Comparisons of the CNR values between the PVP and the AP were made for each energy level and carried out using a completely random t test.A χ2 test was used to compare the detection rates obtained from the two scanning methods.RESULTS: The total detection rates for energy spectral CT and mixed-energy CT in the AP were 88.57%(31/35) and 65.71%(23/35),respectively,and the difference was significant(χ2 = 5.185,P = 0.023); the total detection rates in the PVP were 100.00%(35/35) and 91.4%(32/35),respectively,and the difference was not significant(χ2 = 1.393,P = 0.238).In the AP,the CNR of the contrast agent extravasation regions was 3.58 ± 2.09 on the mixed-energy CT images,but the CNRs were 8.78 ± 7.21 and 8.83 ± 6.75 at 50 and 60 keV,respectively,on the single-energy CT images,which were significantly different(3.58 ± 2.09 vs 8.78 ± 7.21,P = 0.031; 3.58 ± 2.09 vs 8.83 ± 6.75,P = 0.029).In the PVP,the differences between the CNRs at 40,50 and 60 keV different monochromatic energy levels and the polychromatic energy images were significant(19.35 ± 10.89 vs 11.68 ± 6.38,P = 0.010; 20.82 ± 11.26 vs 11.68 ± 6.38,P = 0.001; 20.63 ± 10.07 vs 11.68 ± 6.38,P = 0.001).The CNRs at the different energy levels in the AP and the PVP were significantly different(t =-2.415,-2.380,-2.575,-2.762,-2.945,-3.157,-3.996 and-3.189).CONCLUSION: Monochromatic energy imaging spectral CT is superior to polychromatic energy images for the detection of intestinal hemorrhage,and the detection was easier in the PVP compared with the AP.

Optimization-based image reconstruction in x-ray computed tomography by sparsity exploitation of local continuity and nonlocal spatial self-similarity

The additional sparse prior of images has been the subject of much research in problems of sparse-view computed tomography（CT） reconstruction. A method employing the image gradient sparsity is often used to reduce the sampling rate and is shown to remove the unwanted artifacts while preserve sharp edges, but may cause blocky or patchy artifacts.To eliminate this drawback, we propose a novel sparsity exploitation-based model for CT image reconstruction. In the presented model, the sparse representation and sparsity exploitation of both gradient and nonlocal gradient are investigated.The new model is shown to offer the potential for better results by introducing a similarity prior information of the image structure. Then, an effective alternating direction minimization algorithm is developed to optimize the objective function with a robust convergence result. Qualitative and quantitative evaluations have been carried out both on the simulation and real data in terms of accuracy and resolution properties. The results indicate that the proposed method can be applied for achieving better image-quality potential with the theoretically expected detailed feature preservation.

Low-radiation and high image quality coronary computed tomography angiography in “real-world” unselected patients

AIM To determine the radiation dose and image quality in coronary computed tomography angiography(CCTA)using state-of-the-art dose reduction methods in unselected"real world"patients.METHODS In this single-centre study,consecutive patients in sinus rhythm underwent CCTA for suspected coronary artery disease(CAD)using a 320-row detector CT scanner.All patients underwent the standard CT acquisition protocol at our institute(Morriston Hospital)a combination of dose saving advances including prospective electrocardiogram-gating,automated tube current modulation,tube voltage reduction,heart rate reduction,and the most recent novel adaptive iterative dose reconstruction 3D(AIDR3D)algorithm.The cohort comprised real-world patients for routine CCTA who were not selected on age,body mass index,or heart rate.Subjective image quality was graded on a 4-point scale(4=excellent,1=non-diagnostic).RESULTS A total of 543 patients were included in the study with a mean body weight of 81±18 kg and a pre-scan mean heart rate of 70±11 beats per minute(bpm).When indicated,patients received rate-limiting medication with an oral beta-blocker followed by additional intravenous beta-blocker to achieve a heart rate below 65 bpm.The median effective radiation dose was 0.88 mSv(IQR,0.6-1.4 mSv)derived from a Dose Length Product of61.45 mGy.cm(IQR,42.86-100.00 mGy.cm).This also includes what we believe to be the lowest ever-reported radiation dose for a routine clinical CCTA(0.18 mSv).The mean image quality(SD)was 3.65±0.61,with a subjective image quality score of 3("good")or above for 93%of patient CCTAs.CONCLUSION Combining a low-dose scan protocol and AIDR3D with a 320-detector row CT scanner can provide high quality images at exceptionally low radiation dose in unselected patients being investigated for CAD.

Assessment of tumor vascularization with functional computed tomography perfusion imaging in patients with cirrhotic liver disease

BACKGROUND:Hepatocellular carcinoma(HCC)is a common malignant tumor in China,and early diagnosis is critical for patient outcome.In patients with HCC,it is mostly based on liver cirrhosis,developing from benign regenerative nodules and dysplastic nodules to HCC lesions,and a better understanding of its vascular supply and the hemodynamic changes may lead to early tumor detection.Angiogenesis is essential for the growth of primary and metastatic tumors due to changes in vascular perfusion,blood volume and permeability.These hemodynamic and physiological properties can be measured serially using functional computed tomography perfusion(CTP)imaging and can be used to assess the growth of HCC.This study aimed to clarify the physiological characteristics of tumor angiogenesis in cirrhotic liver disease by this fast imaging method. METHODS:CTP was performed in 30 volunteers without liver disease(control subjects)and 49 patients with liver disease (experimental subjects:27 with HCC and 22 with cirrhosis). All subjects were also evaluated by physical examination, laboratory screening and Doppler ultrasonography of the liver. The diagnosis of HCC was made according to the EASL criteria. All patients underwent contrast-enhanced ultrasonography, pre-and post-contrast triple-phase CT and CTP study.A mathematical deconvolution model was applied to provide hepatic blood flow(HBF),hepatic blood volume(HBV), mean transit time(MTT),permeability of capillary vessel surface(PS),hepatic arterial index(HAI),hepatic arterial perfusion(HAP)and hepatic portal perfusion(HPP)data. The Mann-Whitney U test was used to determine differences in perfusion parameters between the background cirrhotic liver parenchyma and HCC and between the cirrhotic liver parenchyma with HCC and that without HCC.RESULTS:In normal liver,the HAP/HVP ratio was about 1/4. HCC had significantly higher HAP and HAI and lower HPP than background liver parenchyma adjacent to the HCC.The value of HBF at the tumor rim was significantly higher than that in the controls.HBF,HBV,HAI,HAP and HPP,but not MTT and PS,were significantly higher in the cirrhotic liver parenchyma involved with HCC than those of the controls. Perfusion parameters were not significantly different between the controls and the cirrhotic liver parenchyma not involved with HCC. CONCLUSIONS:CTP can clearly distinguish tumor from cirrhotic liver parenchyma and controls and can provide quantitative information about tumor-related angiogenesis, which can be used to assess tumor vascularization in cirrhotic liver disease.

Reactive lymphoid hyperplasia of the liver:Perinodular enhancement on contrast-enhanced computed tomography and magnetic resonance imaging

We report the case of a 69-year-old woman with reactive lymphoid hyperplasia(RLH) of the liver.She underwent partial hepatectomy under a preoperative diagnosis of hepatocellular carcinoma; however,histopathological analysis revealed RLH.The liver nodule showed the imaging feature of perinodular enhancement in the arterial dominant phase on contrast-enhanced computed tomography and magnetic resonance imaging,which could be a useful clue for identifying RLH in the liver.Histologically,the perinodular enhancement was compatible with prominent sinusoidal dilatation surrounding the liver nodule.

Use of high-resolution X-ray computed tomography and 3D image analysis to quantify mineral dissemination and pore space in oxide copper ore particles

Mineral dissemination and pore space distribution in ore particles are important features that influence heap leaching performance. To quantify the mineral dissemination and pore space distribution of an ore particle, a cylindrical copper oxide ore sample (I center dot 4.6 mm x 5.6 mm) was scanned using high-resolution X-ray computed tomography (HRXCT), a nondestructive imaging technology, at a spatial resolution of 4.85 mu m. Combined with three-dimensional (3D) image analysis techniques, the main mineral phases and pore space were segmented and the volume fraction of each phase was calculated. In addition, the mass fraction of each mineral phase was estimated and the result was validated with that obtained using traditional techniques. Furthermore, the pore phase features, including the pore size distribution, pore surface area, pore fractal dimension, pore centerline, and the pore connectivity, were investigated quantitatively. The pore space analysis results indicate that the pore size distribution closely fits a log-normal distribution and that the pore space morphology is complicated, with a large surface area and low connectivity. This study demonstrates that the combination of HRXCT and 3D image analysis is an effective tool for acquiring 3D mineralogical and pore structural data.

Application value analysis of magnetic resonance imaging and computed tomography in the diagnosis of intracranial infection after craniocerebral surgery

BACKGROUND Intracranial infection is a common clinical disease.Computed tomography(CT)and magnetic resonance imaging(MRI)have certain sensitivity and have good diagnostic efficacy.AIM To study the application value of MRI and CT in the diagnosis of intracranial infection after craniocerebral surgery.METHODS We selected 82 patients who underwent craniocerebral surgery(including 40 patients with intracranial infection and 42 patients without infection)during the period from April 2016 to June 2019 in our hospital.All 82 patients received CT and MRI examinations,and their clinical data were reviewed.A retrospective analysis was performed,and the coincidence rate of positive diagnosis and the overall diagnosis coincidence rate of different pathogenic infection types were measured with the two examination methods.The diagnostic sensitivity and specificity as well as the positive and negative predictive values of the two examination methods were compared.RESULTS For all types of pathogenic infections(Staphylococcus aureus,Staphylococcus hemolyticus,Staphylococcus epidermidis,and others),MRI scans had higher positive diagnostic coincidence rates than CT scans;the overall diagnostic coincidence rate,sensitivity,specificity,positive predictive value,and negative predictive values were significantly higher with MRI examinations than with CT examinations,and the differences were statistically significant(P<0.05).CONCLUSION MRI examination can accurately diagnose intracranial infection after clinical craniocerebral surgery.Compared with CT,MRI had higher diagnostic efficiency.The diagnostic sensitivity and specificity,the diagnostic coincidence rate,and the positive and negative predictive values were significantly higher with MRI than with conventional CT,which can be actively promoted.

Myocardial perfusion imaging and infarct characterization using multidetector cardiac computed tomography

Until recently, computed tomography coronary angiography was restricted to the anatomical assessment of coronary stenosis, whereas the functional significance of coronary lesions remained outside of its scope. Nevertheless, the kinetics of iodinated contrast is similar to gadolinium-diethylenetriamine pentaacetic acid used in contrast-enhanced magnetic resonance imaging, allowing assessment of myocardial perfusion and viability by cardiac computed tomography.

Femoroacetabular impingement with chronic acetabular rim fracture- 3D computed tomography, 3D magnetic resonance imaging and arthroscopic correlation

Femoroacetabular impingement is uncommonly associated with a large rim fragment of bone along the superolateral acetabulum. We report an unusual case of femoroacetabular impingement(FAI) with chronic acetabular rim fracture. Radiographic, 3D computed tomography, 3D magnetic resonance imaging and arthroscopy correlation is presented with discussion of relative advantages and disadvantages of various modalities in the context of FAI.

Imaging features of intraductal papillary mucinous neoplasms of the pancreas in multi-detector row computed tomography

AIM:To retrospectively evaluate the imaging features of pancreatic intraductal papillary mucinous neoplasms (IPMNs) in multi-detector row computed tomography (MDCT).METHODS: A total of 20 patients with pathologically-confirmed intraductal papillary mucinous neoplasms (IPMNs) were included in this study. Axial MDCT images combined with CT angiography (CTA) and multiplanar volume reformations (MPVR) or curved reformations (CR) were preoperatively acquired. Two radiologists (Tan L and Wang DB) reviewed all the images in consensus using an interactive picture archiving and communication system. The disputes in readings were resolved through consultation with a third experienced radiologist (Chen KM). Finally, the findings and diagnoses were compared with the pathologic results.RESULTS: The pathological study revealed 12 malignant IPMNs and eight benign IPMNs. The diameters of the cystic lesions and main pancreatic ducts (MPDs) were significantly larger in malignant IPMNs compared with those of the benign IPMNs (P<0.05). The combined-type IPMNs had a higher rate of malignancy than the other two types of IPMNs (P<0.05). Tumors with mural nodules and thick septa had a significantly higher incidence of malignancy than tumors without these features (P<0.05). Communication of side-branch IPMNs with the MPD was present in nine cases at pathologic examination. Seven of them were identified from CTA and MPVR or CR images. From comparison with the pathological diagnosis, the sensitivity, specificity, and accuracy of MDCT in characterizing the malignancy of IPMN of the pancreas were determined to be 100%, 87.5% and 95%, respectively.CONCLUSION: MDCT with CTA and MPVR or CR techniques can elucidate the imaging features of IPMNs and help predict the malignancy of these tumors.

Evaluation of a rabbit rectal VX2 carcinoma model using computed tomography and magnetic resonance imaging

AIM: To establish a rabbit rectal VX2 carcinoma model for the study of rectal carcinoma. METHODS: A suspension of VX2 cells was injected into the rectum wall under the guidance of X-ray fluoroscopy. Computed tomography (CT) and magnetic resonance imaging (MRI) were used to observe tumor growth and metastasis at different phases. Pathological changes and spontaneous survival time of the rabbits were recorded. RESULTS: Two weeks after VX2 cell implantation, the tumor diameter ranged 4.1-5.8 mm and the success implantation rate was 81.8%. CT scanning showed low-density foci of the tumor in the rectum wall, while enhanced CT scanning demonstrated asymmetrical intensification in tumor foci. MRI scanning showed a low signal of the tumor on T1-weighted imaging and a high signal of the tumor on T2-weighted imaging. Both types of signals were intensified with enhanced MRI. Metastases to the liver and lung could be observed 6 wk after VX2 cell implantation, and a large area of necrosis appeared in the primary tumor. The spontaneous survival time of rabbits with cachexia and multiple organ failure was about 7 wk after VX2 cell implantation. CONCLUSION: The rabbit rectal VX2 carcinoma model we established has a high stability, and can be used in the study of rectal carcinoma.