Micro-Computed Tomography Applications in Dentistry

Micro-computed tomography (MCT) encompasses two primary scanning options: ex-vivo and in-vivo imaging. Ex-vivo scanning involves the examination of extracted teeth or dental specimens, allowing for detailed analyses of the microarchitecture of mineralized tissue. By analyzing the microarchitecture of dental tissues, MCT can provide valuable information about bone density, porosity, and microstructural changes, contributing to a better understanding of disease progression and treatment outcomes. Moreover, MCT facilitates the quantification of dental parameters, such as bone volume, trabecular thickness, and connectivity density, which are crucial for evaluating the efficacy of dental interventions. This present study aims to comprehensively review and explore the applications of MCT in dentistry and highlight its potential in advancing research and clinical practice. The results depicted that the quantitative approach of MCT enhances the precision and reliability of dental research. Researchers and clinicians can make evidence-based decisions regarding treatment strategies and patient management, relying on quantifiable data provided by MCT. The applications of MCT in dentistry extend beyond research, with potential clinical implications in fields such as dental implantology and endodontics. MCT is expected to play an increasingly significant role in enhancing our understanding of dental pathologies, improving treatment outcomes, and ultimately, benefiting patient care in the field of dentistry.

Effects of combining multiple dose reduction techniques on coronary computed tomography angiography

BACKGROUND Coronary computed tomography angiography(CCTA)is the preferred noninvasive examination method for coronary heart disease.However,the radiation from computed tomography has become a concern since public awareness of radiation hazards continue to increase.AIM To explore the value of multiple dose reduction techniques for CCTA.METHODS Consecutive normal and overweight patients were prospectively divided into two groups:Group A1,patients who received multiple dose reduction scans(n=82);and group A2,patients who received conventional scans(n=39).The scan parameters for group A1 were as follows:Isocentric scan,tube voltage=80 kV,and tube current control using 80%smart milliampere.The scan parameters for group A2 were as follows:Normal position,tube voltage=100 kV,and smart milliampere.RESULTS The average effective doses(EDs)for groups A1 and A2 were 1.13±0.35 and 3.36±1.30 mSv,respectively.There was a statistically significant difference in ED between the two groups(P<0.01).Furthermore,noise was significantly lower,and both signal-to-noise ratio and contrast signal-to-noise ratio were higher in group A2 when compared to group A1(P<0.01).Moreover,the subjective image quality(IQ)scores were excellent in both groups,in which there was no significant difference in subjective IQ score between the two groups(P=0.12).CONCLUSION Multiple dose reduction scan techniques can significantly decrease the ED of patients receiving CCTA examinations for clinical diagnosis.

Application of CD34 expression combined with three-phase dynamic contrast-enhanced computed tomography scanning in preoperative staging of gastric cancer

BACKGROUND Accurate preoperative staging of gastric cancer(GC),a common malignant tumor worldwide,is critical for appropriate treatment plans and prognosis.Dynamic three-phase enhanced computed tomography(CT)scanning for preoperative staging of GC has limitations in evaluating tumor angiogenesis.CD34,a marker on vascular endothelial cell surfaces,is promising in evaluating tumor angiogenesis.We explored the value of their combination for preoperative staging of GC to improve the efficacy and prognosis of patients with GC.Medical records of 106 patients with GC treated at the First People's Hospital of Lianyungang between February 2021 and January 2023 were retrospectively studied.All patients underwent three-phase dynamic contrast-enhanced CT scanning before surgery,and CD34 was detected in gastroscopic biopsy specimens.Using surgical and pathological results as the gold standard,the diagnostic results of three-phase dynamic contrast-enhanced CT scanning at different T and N stages were analyzed,and the expression of CD34-marked microvessel density(MVD)at different T and N stages was determined.The specificity and sensitivity of three-phase dynamic contrast-enhanced CT and CD34 in T and N staging were calculated;those of the combined diagnosis of the two were evaluated in parallel.Independent factors affecting lymph node metastasis were analyzed using multiple logistic regression.RESULTS The accuracy of three-phase dynamic contrast-enhanced CT scanning in diagnosing stages T1,T2,T3 and T4 were 68.00%,75.00%,79.41%,and 73.68%,respectively,and for diagnosing stages N0,N1,N2,and N3 were 75.68%,74.07%,85.00%,and 77.27%,respectively.CD34-marked MVD expression increased with increasing T and N stages.Specificity and sensitivity of three-phase dynamic contrast-enhanced CT in T staging were 86.79%and 88.68%;for N staging,89.06%and 92.86%;for CD34 in T staging,64.15%and 88.68%;and for CD34 in N staging,84.38%and 78.57%,respectively.Specificity and sensitivity of joint diagnosis in T staging were 55.68%and 98.72%,and N staging were 75.15%and 98.47%,respectively,with the area under the curve for diagnosis improving accordingly.According to multivariate analysis,a longer tumor diameter,higher pathological T stage,lower differ-entiation degree,and higher expression of CD34-marked MVD were independent risk factors for lymph node metastasis in patients with GC.CONCLUSION With high accuracy in preoperatively determining the invasion depth and lymph node metastasis of GC,CD34 expression and three-phase dynamic contrast-enhanced CT can provide a reliable basis for surgical resection.

Does the use of computed tomography scenogram alone enable diagnosis in cases of bowel obstruction?

BACKGROUND Ileus is a pathological condition of the abdomen that presents as a medical emergency.It is characterized by potential complications such as perforation and ischemia,which can lead to significant morbidity and mortality if not promptly addressed.The successful management of ileus relies heavily on the timely and precise identification of the condition.While conventional radiography(CR)is commonly used as the primary diagnostic tool,its accuracy in identifying obstructions ranges from 46%to 80%.Furthermore,the diagnostic accuracy of identifying the location and etiology of intestinal obstruction by CR is limited,therefore making computed tomography(CT)the ideal imaging modality in this regard.AIM To determine the presence of acute bowel obstruction(BO)on abdominal CT scenogram images and the accuracy of determining its possible location,taking into account the experience of the observers.METHODS A retrospective screening was conducted on an ensemble of 46 individuals who presented to the emergency department between January 2021 and January 2022 with severe abdominal pain and were subsequently monitored for suspected ileus.The abdominal CT scans of these patients were assessed by three radiologists with varying levels of experience(1,3,and 10 years)at different intervals(1 mo apart).The evaluation focused on determining the presence or absence of BO,as well as identifying the potential location of the obstruction(small bowel or large bowel).The study employed Kappa statistics to assess inter observer variances,while the McNamer test was used to evaluate obstruction and segmentation discrepancies between observations.A significance level of P<0.05 was determined to indicate statistical significance.RESULTS Out of the total sample size of 46 patients,15 individuals(32.6%)were identified as female,while the remaining 31 individuals(67.4%)were identified as male.The ultimate diagnosis of 42 instances(91.3%)indicated ileus resulting from mechanical obstruction(MO).Among these patients,14(33%)experienced obstruction in the large bowel(LB),while 28(66%)experienced obstruction in the small bowel(SB).The initial evaluation yielded sensitivity rates of 76.19%,83.31%,and 83.33%,and diagnostic accuracy rates of 69.56%,76.08%,and 80.43%for the detection of BO among the three observers.The initial study revealed that the average sensitivity of three observers in detecting the presence of ileus caused by MO was 80.94%,while the diagnostic accuracy was 75.35%.Based on the first evaluation,the senior observer demonstrated the highest sensitivity(85.71%),negative predictive value(92.60%),and diagnostic accuracy(80.43%)when accurately estimating the thick and thin segmentation,as per the final diagnosis.There was no statistically significant disparity observed in the sensitivities pertaining to the identification of ileus during the second assessment,as well as the precise determination of the segment level inside the LB or SB,when comparing the second and third observers.Nevertheless,although there was no statistically significant alteration in the detection rate of ileus by the first observer,there was a notable rise in the accuracy rate of segment estimating(73.91%).The senior assessor had a higher level of accuracy in assessing the existence of ileus and segmentation compared to the other evaluators in both evaluations.CONCLUSION The findings of our study indicate that the sensitivity and accuracy rates of abdominal CT scenogram scans in diagnosing acute MOs are similar to or greater than those of CR.Additionally,the study revealed that radiologists with more experience demonstrated a higher likelihood of accurately predicting the existence and potential localization of MO compared to their less experienced counterparts.

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.

Management of computed tomography scan detected hemothorax in blunt chest trauma:What computed tomography scan measurements say?

AIM To investigate the hemothorax size for which tube thoracostomy is necessary.METHODS Over a 5-year period, we included all patients who were admitted with blunt chest trauma to our level 1 trauma center. Focus was placed on identifying the hemothorax size requiring tube thoracostomy.RESULTS A total number of 274 hemothoraces were studied. All patients with hemothoraces measuring above 3 cm received a chest tube. The 50% predicted probability of tube thoracostomy was 2 cm. Pneumothorax was associated with odds of receiving tube thoracostomy for hemothoraces below 2 cm(Odds Ratio:4.967, 95%CI: 2.225-11.097, P < 0.0001).CONCLUSION All patients with a hemothorax size greater than 3% underwent tube thoracostomy. Prospective studies are warranted to elucidate the clinical outcome of patients with smaller hemothoraces.

Advantages of preoperative planning using computed tomography scan for treatment of malleolar ankle fractures

Malleolar ankle fractures have been classified using plain radiographs,and there is no consensus regarding the role of computed tomography(CT)scans in preoperative planning.We analyzed critical aspects,such as limits of standard radiographs,types of injury,classification methods and cost/benefit evaluations.CT scans allow a 3 D analysis of the fracture to be obtained and consequently assess the indication for surgical procedure,surgical access and the type of fixation devices required.This exam is useful for detecting lesions that may go unnoticed on radiographs and will help surgeons to clarify the pathoanatomy of ankle fractures.According to Arbeitsgemeinschaft fur Osteosynthesefragen/Orthopaedic Trauma Association(AO/OTA)classification,CT scan is recommended in medial malleolar fractures with vertical rim,type 44 B fractures with posterior malleolar involvement and all type 44 C fractures(according to AO/OTA).Also Tillaux-Chaput fractures(43-B1 according to AO/OTA),malleolar fractures in the presence of distal tibial fractures(43 according to AO/OTA)and distal tibia fractures in adolescents should be studied with CT scans.

128-slice Dual-source Computed Tomography Coronary Angiography in Patients with Atrial Fibrillation: Image Quality and Radiation Dose of Prospectively Electrocardiogram-triggered Sequential Scan Compared with Retrospectively Electrocardiogram-gated Spiral

Objective To evaluate the image quality (IQ) and radiation dose of 128-slice dual-source computed tomography (DSCT) coronary angiography using prospectively electrocardiogram (ECG)-triggered sequential scan mode compared with ECG-gated spiral scan mode in a population with atrial fibrillation. Methods Thirty-two patients with suspected coronary artery disease and permanent atrial fibrillation referred for a second-generation 128-slice DSCT coronary angiography were included in the prospective study. Of them, 17 patients (sequential group) were randomly selected to use a prospectively ECG-triggered sequential scan, while the other 15 patients (spiral group) used a retrospectively ECG-gated spiral scan. The IQ was assessed by two readers independently, using a four-point grading scale from excellent (grade 1) to non-assessable (grade 4), based on the American Heart Association 15-segment model. IQ of each segment and effective dose of each patient were compared between the two groups. Results The mean heart rate (HR) of the sequential group was 96±27 beats per minute (bpm) with a variation range of 73±25 bpm, while the mean HR of the spiral group was 86±22 bpm with a variationrange of 65±24 bpm. Both of the mean HR (t=1.91, P=0.243) and HR variation range (t=0.950, P=0.350) had no significant difference between the two groups. In per-segment analysis, IQ of the sequential group vs. spiral group was rated as excellent (grade 1) in 190/244 (78%) vs. 177/217 (82%) by reader1 and 197/245 (80%) vs. 174/214 (81%) by reader2, as non-assessable (grade 4) in 4/244 (2%) vs. 2/217 (1%) by reader1 and 6/245 (2%) vs. 4/214 (2%) by reader2. Overall averaged IQ per-patient in the sequential and spiral group showed equally good (1.27±0.19 vs. 1.25±0.22, Z=-0.834, P=0.404). The effective radiation dose of the sequential group reduced significantly compared with the spiral group (4.88±1.77 mSv vs. 10.20±3.64 mSv; t=-5.372, P=0.000). Conclusion Compared with retrospectively ECG-gated spiral scan, prospectively ECG-triggered sequential DSCT coronary angiography provides similarly diagnostically valuable images in patients with atrial fibrillation and significantly reduces radiation dose.

Conception the Fluid Flow Behavior within Oil Reservoir Rock by Using Computed Tomography(CT)Scan

The behavior of fluid flow has been studied during the different flow media over the past decades.In addition,the behavior of the flow of fluid through porous media has garnered much research interest.This paper sheds light on fissured rocks of oil reservoir media(as one of the porous media domain),and the effect of these fissured on fluid flow.In this article,the Finite Volume Method(FVM)has been used to visualize the behavior of single-phase fluid flow in an actual core according to the dual-porosity dual permeability model.The study was conducted in two parts,the first was the image processing for one of the real oil reservoir fractured rock images,where the image was processed and simulated by ANSYS-CFX software,and the results showed a complete visualizing of the fluid behavior during this domain.As for the other side,a simulation of a real reservoir rock belonging to the Al-Nour field in Iraq/Misan was made.The X-ray Computed Tomography(CT)scan has been used to convert the real fractured core to a dynamic domain.ANSYS-CFX program has been used and the results illustrated the pressure counter,the velocity counter,the velocity streamline,and the velocity vectors for the studied model in three dimensions.A comparison was made between the productivity index for fractured and non-fractured rock and the results explained that the presence of fracture can improve the productivity index to about 5.74%.

Three-dimensional finite element simulation and reconstruction of jointed rock models using CT scanning and photogrammetry

The geometry of joints has a significant influence on the mechanical properties of rocks.To simplify the curved joint shapes in rocks,the joint shape is usually treated as straight lines or planes in most laboratory experiments and numerical simulations.In this study,the computerized tomography (CT) scanning and photogrammetry were employed to obtain the internal and surface joint structures of a limestone sample,respectively.To describe the joint geometry,the edge detection algorithms and a three-dimensional (3D) matrix mapping method were applied to reconstruct CT-based and photogrammetry-based jointed rock models.For comparison tests,the numerical uniaxial compression tests were conducted on an intact rock sample and a sample with a joint simplified to a plane using the parallel computing method.The results indicate that the mechanical characteristics and failure process of jointed rocks are significantly affected by the geometry of joints.The presence of joints reduces the uniaxial compressive strength (UCS),elastic modulus,and released acoustic emission (AE) energy of rocks by 37%–67%,21%–24%,and 52%–90%,respectively.Compared to the simplified joint sample,the proposed photogrammetry-based numerical model makes the most of the limited geometry information of joints.The UCS,accumulative released AE energy,and elastic modulus of the photogrammetry-based sample were found to be very close to those of the CT-based sample.The UCS value of the simplified joint sample (i.e.38.5 MPa) is much lower than that of the CT-based sample (i.e.72.3 MPa).Additionally,the accumulative released AE energy observed in the simplified joint sample is 3.899 times lower than that observed in the CT-based sample.CT scanning provides a reliable means to visualize the joints in rocks,which can be used to verify the reliability of photogrammetry techniques.The application of the photogrammetry-based sample enables detailed analysis for estimating the mechanical properties of jointed rocks.

Rare finding of primary aortoduodenal fistula on single-photon emission computed tomography/computed tomography of gastrointestinal bleeding: A case report

BACKGROUND Primary aortoduodenal fistula is a rare cause of gastrointestinal(GI)bleeding consisting of abnormal channels between the aorta and GI tract without previous vascular intervention that results in massive intraluminal hemorrhage.CASE SUMMARY A 67-year-old man was hospitalized for coffee ground vomiting,tarry stools,and colic abdominal pain.He was repeatedly admitted for active GI bleeding and hypovolemic shock.Intermittent and spontaneously stopped bleeders were undetectable on multiple GI endoscopy,angiography,computed tomography angiography(CTA),capsule endoscopy,and ^(99)mTc-labeled red blood cell(RBC)scans.The patient received supportive treatment and was discharged without signs of rebleeding.Thereafter,he was re-admitted for bleeder identification.Repeated CTA after a bleed revealed a small aortic aneurysm at the renal level contacting the fourth portion of the duodenum.A ^(99)mTc-labeled RBC singlephoton emission CT(SPECT)/CT scan performed during bleeding symptoms revealed active bleeding at the duodenal level.According to his clinical symptoms(intermittent massive GI bleeding with hypovolemic shock,dizziness,dark red stool,and bloody vomitus)and the abdominal CTA and ^(99)mTc-labeled RBC SPECT/CT results,we suspected a small aneurysm and an aortoduodenal fistula.Subsequent duodenal excision and duodenojejunal anastomosis were performed.A 7-mm saccular aneurysm arising from the anterior wall of the abdominal aorta near the left renal artery was identified.Percutaneous intravascular stenting of the abdominal aorta was performed and his symptoms improved.CONCLUSION Our findings suggest that ^(99)mTc-labeled RBC SPECT/CT scanning can aid the diagnosis of a rare cause of active GI bleeding.

Evaluation of response to gemcitabine plus cisplatin-based chemotherapy using positron emission computed tomography for metastatic bladder cancer

BACKGROUND The purpose of the present study was to examine retrospectively the contribution of 18Fluorodeoxyglucose positron emission tomography computed tomography(18FDG-PET/CT)to the evaluation of response to first-line gemcitabine plus cispla-tin-based chemotherapy in patients with metastatic bladder cancer.AIM To evaluate the response to Gemcitabine plus Cisplatin-based chemotherapy using 18FDG-PET/CT imaging in patients with metastatic bladder cancer.METHODS Between July 2007 and April 2019,79 patients underwent 18FDG-PET/CT imaging with the diagnosis of Metastatic Bladder Carcinoma(M-BCa).A total of 42 pa-tients(38 male,4 female)were included in the study,and all had been admi-nistered Gemcitabine plus Cisplatin-based chemotherapy.After completion of the therapy,the patients underwent a repeat 18FDG-PET/CT scan and the results were compared with the PET/CT findings before chemotherapy according to European Organisation for the Research and treatment of cancer criteria.Mean age was 66.1 years and standard deviation was 10.7 years(range:41–84 years).RESULTS Of the patients,seven(16.6%)were in complete remission,17(40.5%)were in partial remission,six(14.3%)had a stable disease,and 12(28.6%)had a pro-gressive disease.The overall response rate was 57.1 percent.CONCLUSION 18FDG-PET/CT can be considered as a successful imaging tool in evaluating response to first-line chemotherapy for metastatic bladder cancer.Anatomical and functional data obtained from PET/CT scans may be useful in the planning of secondline and thirdline chemotherapy.

Radiation Dose Survey of Pediatric Chest Computed Tomography Examinations: A Local Diagnostic Reference Levels Approach to Patient Safety

Objectives: The aim of this work was to initially establish both age and weight driven pediatric diagnostic reference levels (DRLs) for chest computed tomography (CT) examinations performed at tertiary care medical institution. Another aim was to compare the presented data with internationally published ones. This initial data shall serve as basis for establishing a national DRLs values for pediatric diagnostic CT examinations. Methods: Dosimetric indexes were collected for the chest examination for 93 patients during the past 2 years in a tertiary care medical city. Results: The results are within and below the international reported levels for chest CT in several countries. Conclusion: Continuous monitoring of the radiation doses received by the patients in computed tomography is continuous and ongoing process in order to ensure compliance and to optimize clinical imaging protocols. More extensive data acquisition and analysis are required to allow better understanding of the contributing factors leading to less patient radiation dose while preserving the clinical image quality. .

Accuracy of colon tumor localization:Computed tomography scanning as a complement to colonoscopy

AIM:To determine the utility of computed tomography(CT) scanning in localizing colon tumors.METHODS:At a single tertiary care teaching hospital,a retrospective chart review was conducted on patients who underwent surgery for colon malignancies between January 2004 and May 2006.One hundred and four charts containing all of the following data were reviewed:preop erative colonoscopy report,preoperative CT report,surgical operative report,tumor pathology report.The colon was divided into five segments from the cecum to the sigmoid and the location of the lesions was categorized into one of these areas.The tumor location was considered "erroneous" if its location determined during surgery differed from the location determined by colonoscopy or CT.RESULTS:Over all,tumor location was accurately determined via colonoscopy in 83/104 cases(79.8%) and erroneously in 21/104(20.2%) of cases.CT scan accurately localized colon tumors in 52/104(50.0%) of cases,incorrectly localized tumors in 18/104(17.3%) of cases,and did not detect known tumors in 34/104(32.7%) of cases.Of the 21 tumors erroneously located by colonoscopy,11(52.4%) were accurately localized by CT scan.The average tumor size for all patients in this study was 5.72(+/-3.11) cm.The average size of tumors properly located by colonoscopy and CT was 5.39(+/-3.34) cm and 6.79(+/-3.48) cm,respectively.The average size of the tumors not detected by CT was 3.98(+/-1.75) cm.CONCLUSION:CT scanning may be used in concert with colonoscopy to help localize colon tumors.

Perfusion characterization of liver metastases from endocrine tumors:Computed tomography perfusion

AIM:To assess prospectively parameters of computed tomography perfusion(CT p) for evaluation of vascularity of liver metastases from neuroendocrine tumors.METHODS:This study was approved by the hospital's institutional review board.All 18 patients provided informed consent.There were 30 liver metastases from neuroendocrine tumors.Patients were divided into three groups depending on the appearance of the liver metastases at the arterial phase of morphological CT(hyperdense,hypodense and necrotic).Sequential acquisition of the liver was performed before and for 2 min after intravenous injection of 0.5 mg/kg contrast medium,at 4 mL/s.Data were analyzed using deconvolution analysis to calculate blood flow(BF),blood volume(BV),mean transit time(MTT),hepatic arterial perfusion index(HAPI) and a bi-compartmental analysis was performed to obtain vascular permeability-surface area product(PS).Post-treatment analysis was performed by a radiologist and regions of interest were plotted on the metastases,normal liver,aorta and portal vein.RESULTS:At the arterial phase of the morphological CT scan,the aspects of liver metastases were hyperdense(n=21),hypodense(n=7),and necrotic(n=2).In cases of necrotic metastases,none of the CT p parameters were changed.Compared to normal liver,a significant difference in all CT p parameters was found in cases of hyperdense metastases,and only for HAPI and MTT in cases of hypodense metastases.No significant difference was found for MTT and HAPI between hypo-and hyperdense metastases.A significant decrease of PS,BV and BF was demonstrated in cases of patients with hypodense lesions PS(23±11.6 mL/100 g per minute) compared to patients with hyperdense lesions;PS(13.5±10.4 mL/100 g per minute),BF(93.7±75.4 vs 196.0±115.6mL/100 g per minute) and BV(9.7±5.9 vs 24.5 10.9 mL/100 g).CONCLUSION:CT p provides additional information compared to the morphological appearance of liver metastases.

Diagnostic value for extrahepatic metastases of hepatocellular carcinoma in positron emission tomography/computed tomography scan

AIM: To evaluated the value of 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) scan in diagnosis of hepatocellular carcinoma (HCC) and extrahepatic metastases. METHODS: A total of 138 patients with HCC who had both conventional imaging modalities and 18F-FDG PET/CT scan done between November 2006 and March 2011 were enrolled. Diagnostic value of each imaging modality for detection of extrahepatic metastases was evaluated. Clinical factors and tumor characteristics including PET imaging were analyzed as indicative factors for metastases by univariate and multivariate methods. RESULTS: The accuracy of chest CT was significantly superior compared with the accuracy of PET imaging for detecting lung metastases. The detection rate of metastatic pulmonary nodule ≥ 1 cm was 12/13 (92.3%), when < 1 cm was 2/10 (20%) in PET imaging. The accuracy of PET imaging was significantly superior compared with the accuracy of bone scan for detecting bone metastases. In multivariate analy- sis, increased tumor size (≥ 5 cm) (P = 0.042) and increased average standardized uptake value (SUV) uptake (P = 0.028) were predictive factors for extrahepatic metastases. Isometabolic HCC in PET imaging was inversely correlated in multivariate analysis (P = 0.035). According to the receiver operating characteristic curve, the optimal cutoff of average SUV to predict extrahepatic metastases was 3.4. CONCLUSION: 18F-FDG PET/CT scan is invaluable for detection of lung metastases larger than 1 cm and bone metastases. Primary HCC having larger than 5 cm and increased average SUV uptake more than 3.4 should be considered for extrahepatic metastases.

Experiences and benefits of positron emitted tomography-computed tomography (PET-CT) combined with video-assisted thoracoscopic surgery (VATS) in the diagnosis of Stage 1 sarcoidosis

Background: The purpose of this study was to describe our experiences and analyze the benefits of video-assisted thoracoscopic surgery (VATS) combined with positron emitted tomography (PET)-computed tomography (CT) in the diagnosis of patients with early (Stage 1) sarcoidosis. Methods: From 1995 to 2006, seven patients (two males, five females), with ages ranging from 26 to 58 years, were impressed with Stage 1 sarcoidosis (mediastinal or hilar lymph nodes involvements without lung in- volvement) by histological examination of intrathoracic lymph nodes (LNs) and/or lung parenchyma taken from VATS biopsy. Three of them received PET or PET-CT evaluation. VATS was approached from the right and left side in one and six patients, respectively, according to the locations of their lesions. Results: All the VATS biopsied LNs or lung specimens were adequate for establishing diagnosis. Mediastinal LNs were taken from Groups 3, 4 in four, Group 7 in two, and Groups 5, 6 in one of them. Hilar LNs biopsies were performed in four cases. Lung biopsy was performed in all but two cases. All of them were expressed pathologically or radiologically as Stage 1 sarcoidosis. PET-CT revealed high emission signals over these affected LNs. These patients received oral steroid treatment or follow up only. All of them were followed up from 5 months to 11 years with satis- factory results. Conclusion: VATS biopsy is a minimally invasive, safe and effective procedure. It can be used as a diagnostic alternative of transbronchial lung biopsy (TBLB), and can harvest larger and more areas of specimens than mediastinoscopy for staging patients with sarcoidosis. PET-CT can provide us more accurate information about the characteristics and localization of these lesions before biopsy. VATS combined with PET-CT can provide more accurate and earlier diagnosis of patients with unknown intrathoracic lesions, including the sarcoidosis.

Characterization of microstructure evolution of cement paste by micro computed tomography

Micro computed tomography (Micro-CT) was applied to obtain three-dimensional images of the microstructure of cement paste (water-to-cement mass ratio of 0.5) at different ages. By using the Amira software, component phases of the cement paste such as pores, hydration products, and unhydrated clinker particles were segmented from each other based on their 3D image grey levels; their relative contents were also calculated with the software, and the data are 61.2%, 0% and 38.8% at the beginning of hydration and 11.8%, 78.5% and 9.7% at 28 d age, respectively. The hydration degree of cement paste at different ages was compared with the experimental data acquired by loss on ignition (LOI) tests. The results show that the calculated and measured data reasonably agree with each other, which indicates that micro-CT is a useful and reliable approach to characterize the micro structure evolution of hydrating cement paste.

Multi-detector computed tomography in the diagnosis and management of acute aortic syndromes

Acute aortic syndrome(AAS) is a spectrum of conditions, which may ultimately progress to potentially life-threatening aortic rupture. This syndrome encompasses aortic dissection(AD), intramural haematoma, penetrating atherosclerotic ulcer and unstable thoracic aortic aneurysms. Multi-detector CT(MDCT) is crucial for the diagnosis of AAS, especially in the emergency setting due to its speed, accuracy and ready availability. This review attends to the value of appropriate imaging protocols in obtaining good quality images that can permit a confident diagnosis of AAS. AD is the most commonly encountered AAS and also the one with maximum potential to cause catastrophic outcome if not diagnosed and managed promptly. Hence, this review briefly addresses certain relevant clinical perspectives on this condition. Differentiating the false from the true lumen in AD is often essential; a spectrum of CT findings, e.g., "beak sign", aortic "cobwebs" that allows such differentiation have been described with explicit illustrations. The value of non enhanced CT scans, especially useful in the diagnosis of an intramural hematoma has also been illustrated. Overlap in the clinical and imaging features of the various conditions presenting as AAS is not unusual. However, on most instances MDCT enables the rightdiagnosis. On select occasions MRI or trans-esophageal echocardiography may be required as a problem solving tool.

Relation between Epicardial Adipose Tissue Thickness Assessed by Multidetector Computed Tomography and Significance of Coronary Artery Disease

Objective: To evaluate the relation between epicardial adipose tissue (EAT) thickness and also pericoronary fat assessed by Multidetector Computed Tomography (MDCT) with both calcium score and significance of coronary artery disease. Background: Epicardial adipose tissue (the visceral fat of the heart present under the visceral layer of the pericardium) has the same origin of abdominal visceral fat, which is known to be strongly related to the development of coronary artery atherosclerosis. Multidetector CT (MDCT) provides an accurate and reproducible quantification of EAT due to its high spatial and temporal resolution. Patients and Methods: The current study included 70 patients with low-intermediate probability of coronary artery disease. All patients were subjected to 256 Multidetectors CT to assess EAT thickness, the mean thickness of the pericoronary fat surrounding the three coronary arteries and coronary calcium score. Also coronary CT angiography was done and patients were then divided into 3 groups according to significance of coronary atherosclerosis: Group 1: No atherosclerosis (20 patients), Group 2: Non obstructive atherosclerosis (luminal narrowing less than 50% in diameter) (25 patients), Group3: Obstructive atherosclerosis (luminal narrowing ≥ 50%) (25 patients). Results: The mean EAT thickness and the mean pericoronary fat thickness were significantly higher in patients with obstructive coronary artery disease (CAD) with stenosis > 50% (group 3) compared to other groups with normal coronaries or non obstructive (CAD). ROC curve was used to define the best cut off value of the thickness of both EAT and pericoronary fat in predicting the obstructive CAD group which was ≥7.2 and 12.6 mm for epicardial and pericoronary fat respectively. Also there is a positive correlation between both epicardial adipose tissue and pericoronary fat thickness and the coronary calcium score. Conclusion: EAT thickness and pericoronary fat thickness can be used in predicting the significance of coronary artery disease.