Maximum Slope Method Research Articles

Short-term PET-derived kinetic estimation for the diagnosis of hepatocellular carcinoma: a combination of the maximum-slope method and dual-input three-compartment model

BackgroundKinetic estimation provides fitted parameters related to blood flow perfusion and fluorine-18-fluorodeoxyglucose (18F-FDG) transport and intracellular metabolism to characterize hepatocellular carcinoma (HCC) but usually requires 60 min or more for dynamic PET, which is time-consuming and impractical in a busy clinical setting and has poor patient tolerance.MethodsThis study preliminarily evaluated the equivalence of liver kinetic estimation between short-term (5-min dynamic data supplemented with 1-min static data at 60 min postinjection) and fully 60-min dynamic protocols and whether short-term 18F-FDG PET-derived kinetic parameters using a three-compartment model can be used to discriminate HCC from the background liver tissue. Then, we proposed a combined model, a combination of the maximum-slope method and a three-compartment model, to improve kinetic estimation.ResultsThere is a strong correlation between the kinetic parameters K1 ~ k3, HPI and {{varvec{V}}}_{{varvec{b}}} in the short-term and fully dynamic protocols. With the three-compartment model, HCCs were found to have higher k2, HPI and k3 values than background liver tissues, while K1, k4 and {{varvec{V}}}_{{varvec{b}}} values were not significantly different between HCCs and background liver tissues. With the combined model, HCCs were found to have higher HPI, K1 and k2, k3 and {{varvec{V}}}_{{varvec{b}}} values than background liver tissues; however, the k4 value was not significantly different between HCCs and the background liver tissues.ConclusionsShort-term PET is closely equivalent to fully dynamic PET for liver kinetic estimation. Short-term PET-derived kinetic parameters can be used to distinguish HCC from background liver tissue, and the combined model improves the kinetic estimation.Clinical relevance statementShort-term PET could be used for hepatic kinetic parameter estimation. The combined model could improve the estimation of liver kinetic parameters.Graphical

A Progressive Plane Detection Filtering Method for Airborne LiDAR Data in Forested Landscapes

Ground filtering is necessary in processing airborne light detection and ranging (LiDAR) point clouds for forestry applications. This study proposes a progressive plane detection filtering (PPDF) method. First, the method uses multi-scale planes to characterize terrain, i.e., the local terrain with large slope variations is represented by small-scale planes, and vice versa. The planes are detected in local point clouds by the random sample consensus method with decreasing plane sizes. The reliability of the planes to represent local terrain is evaluated and the planes with optimal sizes are selected according to evaluation results. Then, ground seeds are identified by selecting the interior points of the planes. Finally, ground points are iteratively extracted based on the reference terrain, which is constructed using evenly distributed neighbor ground points. These neighbor points are identified by selecting the nearest neighbor points of multiple subspaces, which are divided from the local space with an unclassified point as center point. PPDF was tested in six sites with various terrain and vegetation characteristics. Results showed that PPDF was more accurate and robust compared to the classic filtering methods including maximum slope, progressive morphology, cloth simulation, and progressive triangulated irregular network densification filtering methods, with the smallest average total error and standard deviation of 3.42% and 2.45% across all sites. Moreover, the sensitivity of PPDF to parameters was low and these parameters can be set as fixed values. Therefore, PPDF is effective and easy-to-use for filtering airborne LiDAR data.

LAI-Based Phenological Changes and Climate Sensitivity Analysis in the Three-River Headwaters Region

Global climate changes have a great impact on terrestrial ecosystems. Vegetation is an important component of ecosystems, and the impact of climate changes on ecosystems can be determined by studying vegetation phenology. Vegetation phenology refers to the phenomenon of periodic changes in plants, such as germination, flowering and defoliation, with the seasonal change of climate during the annual growth cycle, and it is considered to be one of the most efficient indicators to monitor climate changes. This study collected the global land surface satellite leaf area index (GLASS LAI) products, meteorological data sets and other auxiliary data in the Three-River headwaters region from 2001 to 2018; rebuilt the vegetation LAI annual growth curve by using the asymmetric Gaussian (A-G) fitting method and extracted the three vegetation phenological data (including Start of Growing Season (SOS), End of Growing Season (EOS) and Length of Growing Season (LOS)) by the maximum slope method. In addition, it also integrated Sen’s trend analysis method and the Mann-Kendall test method to explore the temporal and spatial variation trends of vegetation phenology and explored the relationship between vegetation phenology and meteorological factors through a partial correlation analysis and multiple linear regression models. The results of this study showed that: (1) the SOS of vegetation in the Three-River headwaters region is concentrated between the beginning and the end of May, with an interannual change rate of −0.14 d/a. The EOS of vegetation is concentrated between the beginning and the middle of October, with an interannual change rate of 0.02 d/a. The LOS of vegetation is concentrated between 4 and 5 months, with an interannual change rate of 0.21 d/a. (2) Through the comparison and verification with the vegetation phenological data observed at the stations, it was found that the precision of the vegetation phonology extracted by the A-G method and the maximum slope method based on GLASS LAI data is higher (MAE is 7.6 d, RMSE is 8.4 d) and slightly better than the vegetation phenological data (MAE is 9.9 d, RMSE is 10.9 d) extracted based on the moderate resolution imaging spectroradiometer normalized difference vegetation index (MODIS NDVI) product. (3) The correlation between the SOS of vegetation and the average temperature in March–May is the strongest. The SOS of vegetation is advanced by 1.97 days for every 1 °C increase in the average temperature in March–May; the correlation between the EOS of vegetation and the cumulative sunshine duration in August–October is the strongest. The EOS of vegetation is advanced by 0.07 days for every 10-h increase in the cumulative sunshine duration in August–October.

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

BackgroundThe maximum slope (MS) and deconvolution (DC) algorithms are commonly used to post‐process computed tomography perfusion (CTP) data. This study aims to analyze the differences between MS and DC algorithms for the calculation of pancreatic CTP parameters.MethodsThe pancreatic CTP data of 57 patients were analyzed using MS and DC algorithms. Two blinded radiologists calculated pancreatic blood volume (BV) and blood flow (BF). Interobserver correlation coefficients were used to evaluate the consistency between two radiologists. Paired t‐tests, Pearson linear correlation analysis, and Bland–Altman analysis were performed to evaluate the correlation and consistency of the CTP parameters between the two algorithms.ResultsAmong the 30 subjects with normal pancreas, the BV values in the three pancreatic regions were higher in the case of the MS algorithm than in the case of the DC algorithm (t = 39.35, p < 0.001), and the BF values in the three pancreatic regions were slightly higher for the MS algorithm than for the DC algorithm (t = 2.19, p = 0.031). Similarly, among the 27 patients with acute pancreatitis, the BV values obtained using the MS methods were higher than those obtained using the DC methods (t = 54.14, p < 0.001). Furthermore, the BF values were higher with the MS methods than the DC methods (t = 8.45, p < 0.001). Besides, Pearson linear correlation and Bland–Altman analysis showed that the BF and BV values showed a good correlation and a bad consistency between the two algorithms.ConclusionsThe BF and BV values measured using MS and DC algorithms had a good correlation but were not consistent.

Congestion Area of the Right Lobe Graft in Living Donor Liver Transplantation: Quantitative Evaluation of Hemodynamics Using Computed Tomography Perfusion

The hemodynamics of congestion areas in the right lobe graft after living donor liver transplantation (LDLT) remains unclear. The aim of this study was to elucidate the hemodynamics of congestion areas in the right lobe graft after LDLT using computed tomography (CT) perfusion imaging and the dual-input maximum slope method. Sixteen recipients underwent CT perfusion of the liver and portal phase abdominal to pelvic CT 1week after LDLT using a right lobe graft. The attenuation of segments V and VIII on the portal venous phase abdominal to the pelvic CT scan was classified into 3 categories: hyperattenuation, iso-attenuation, and hypoattenuation. Mean arterial blood flow (AF, mL/min/100 mL tissue), portal blood flow (PF, mL/min/100 mL tissue), and perfusion index (%) [PI=AF/(AF+PF)×100] were compared between the hyperattenuation group and iso-attenuation group. The independent t test was used for these statistical analyses. On the portal phase abdominal scan, 15 segments, 16 segments, and 1 segment showed hyperattenuation, iso-attenuation, and hypoattenuation, respectively. The mean AF and PI of the hyperattenuation group (44.4 ± 24.4, 30.2 ± 13.5) were significantly higher than those of the iso-attenuation group (28.0 ± 7.8, 19.9 ± 6.2) (P < .05, P < .05). The congested liver segments showed high AF and high PI on CT perfusion imaging. This method enables the feasible quantification of the hemodynamics and the description of focal hemodynamic change in the graft after LDLT.

Computed Tomography Perfusion Analysis of Pancreatic Adenocarcinoma using Deconvolution, Maximum Slope, andPatlakMethods - Evaluation of Diagnostic Accuracy andInterchangeability of Cut-Off Values.

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. 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. 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. 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. · 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.. · 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.

Proposed resilience index of water lifeline systems

PurposeWater distribution networks (WDNs) must deliver water to its customers 24/7. Disruption of this important service after a strong seismic event impedes post-disaster activities and poses health and sanitation problems. Hence, WDNs must be able to quickly restore services after the occurrence of a major seismic event. This ability to return the water service can be a metric for resilience. The purpose of this paper is to quantify the resilience by developing a framework that translates various restoration strategies into an improved resilience measure for a multisource WDN.Design/methodology/approachThis paper used a quantitative risk assessment method in developing the framework for the resilience quantification of WDN. Prim’s algorithm, Horn’s algorithm and maximum slope method are used for the restoration analysis conducted in this study.FindingsThis paper provides resilience indices of the WDN for each repair scenarios. Then, the resilience indices are used to determine the most efficient and optimized repair scenario to restore the hypothetically damaged WDN owing to Level 1 and Level 2 seismic events.Research limitations/implicationsThe developed framework of this study only focuses on the robustness, rapidity and resourcefulness properties of resilience.Practical implicationsThis study aims to help the water district in the maintenance, repair and evaluation of WDN against seismic events. The results from the study can be used in preparing the disaster management plan of the local water district to repair possible pipelines. This study also serves as a starting point to more complex and comprehensive research about the resilience quantification of WDNs with the consideration of optimal restoration sequence in the future.Originality/valueThe developed framework in the resilience quantification of WDN is original, as it uses optimal restoration strategies to represent the rapidity property of resilience.

Estimating regional pulmonary blood flow in EIT with regularized deconvolution with a Tikhonov regularization

Abstract Electrical Impedance Tomography (EIT) is a clinically used tool for bed-side monitoring of ventilation. Previous work also showed a high potential for lung perfusion monitoring with indicator-enhanced EIT. However, many research questions have yet to be answered before it can be broadly applied in clinical everyday life. The goal of this work is to evaluate a new method to improve EIT perfusion measurements. Pulmonary hemodynamic transfer functions were estimated using regularized deconvolution with Tikhonov regularization to estimate spatial perfusion parameters. The final comparison between EIT images and PET scans showed a median correlation of 0.897 for the images which were reconstructed using the regularized deconvolution. In comparison the previously used maximum slope method led to a median correlation of 0.868.

Effect of contrast medium injection rate on computed tomography-derived renal perfusion estimates obtained with the maximum slope method in healthy.

OBJECTIVE To evaluate the effect of contrast medium injection rate on CT-derived renal perfusion estimates obtained with the maximum slope method in healthy small dogs. ANIMALS 6 healthy sexually intact male purpose-bred Beagles. PROCEDURES All dogs underwent CT perfusion analysis 3 times in a crossover design, receiving a different contrast medium injection rate (1.5, 3.0, and 4.5 mL/s) each time, with a 1-week interval between imaging sessions. All CT images were obtained at the level of the left renal hilus. The time to peak aortic enhancement (TPAE) and time to initial renal venous enhancement (TIRVE) were measured from time-attenuation curves. The renal CT perfusion estimates (blood flow and blood volume) were estimated by use of the maximum slope method, which assumes no venous outflow of contrast medium during CT perfusion analysis. RESULTS The TPAE occurred at or before the TIRVE at all injection rates. Median values of estimated blood flow and blood volume did not differ significantly among injection rates. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that the assumption of no venous outflow of contrast medium during renal CT perfusion analysis with the maximum slope method was satisfied for all 3 contrast medium injection rates in the evaluated dogs. A low injection rate may be more practical than higher injection rates that require large catheters for CT perfusion analysis in small dogs such as Beagles.

Determination Of Heat Transfer Characteristics Employing Modified Maximum Slope Method For Porous Media Heat Exchanger Using Al2O3–Water Nanofluids

It has been well documented in many literature that porous media and nanofluid can augment heat transfer in many engineering system. However the combined usage of these two media has not been given much attention in literature. The objective of the present work is to experimentally investigate porous media heat exchanger using Al2O3/water nanofluids. The heat transfer characteristics is determined using transient testing method wherein, only one fluid stream flows steadily throughthe test core, then a transient perturbation in the inlet fluid temperature is induced and the outletfluid temperature variation is measured continuously. The measured data is evaluated using the maximum slope method to obtain the heat transfer characteristics. The results show an increase in Nusselt number values with the use of nanofluids in porous media heat exchanger compared to water

CT Perfusion in Patients with Lung Cancer: Squamous Cell Carcinoma and Adenocarcinoma Show a Different Blood Flow

Objectives To characterize tumour baseline blood flow (BF) in two lung cancer subtypes, adenocarcinoma (AC) and squamous cell carcinoma (SCC), also investigating those “borderline” cases whose perfusion value is closer to the group mean of the other histotype. Materials and Methods 26 patients (age range 36-81 years) with primary Non-Small Cell Lung Cancer (NSCLC), subdivided into 19 AC and 7 SCC, were enrolled in this study and underwent a CT perfusion, at diagnosis. BF values were computed according to the maximum-slope method and unreliable values (e.g., arising from artefacts or vessels) were automatically removed. The one-tail Welch's t-test (p-value <0.05) was employed for statistical assessment. Results At diagnosis, mean BF values (in [mL/min/100g]) of AC group [(83.5 ± 29.4)] are significantly greater than those of SCC subtype [(57.0 ± 27.2)] (p-value = 0.02). However, two central SCCs undergoing artefacts from vena cava and pulmonary artery have an artificially increased mean BF. Conclusions The different hemodynamic behaviour of AC and SCC should be considered as a biomarker supporting treatment planning to select the patients, mainly with AC, that would most benefit from antiangiogenic therapies. The significance of results was achieved by automatically detecting and excluding artefactual BF values.

Dynamic flow imaging using 320-detector row CT and motion coherence analysis in coronary aneurysms associated with Kawasaki disease.

Six patients with Kawasaki disease and coronary aneurysms associated (26.7 years old) and six controls were enrolled. Dynamic coronary CT angiography with 320-row CT was continuously performed at mid-diastole throughout 15-25 cardiac cycles with prospective Electrocardiogram gating after injection of contrast media. Dynamic data sets of 15-25 cycles were computed into 90-100 data sets by motion coherence image processing. Next, time-density curves for coronary arteries were calculated for all the phases. On the basis of the maximum slope method, coronary flow index was defined as the ratio of the maximum upslope of the attenuation of coronary arteries to the upslope of the attenuation of ascending aorta on the time-density curves. Coronary flow indexes for the proximal and distal sites of coronary arteries and intra-aneurysm were measured.

Aeromagnetic mapping of basement relief features in parts of Lower Benue Trough (Afikpo – Ugep): Implications on hydrocarbon prospectivity south – east, Nigeria

Two (2) aeromanetic maps on a scale of 1:100,000 covering parts of the Lower Benue Trough (Afikpo sheet 313 and Ugep sheet314) were digitized manually along a total of 70 profiles lines to obtain 5422 data points. The digitized values were contoured to obtain the total magnetic field intensity map of the study area.The merged data was processed and filtered using diferent softwares to perform anomaly separation techniques to obtain the residual fields,petters half width and maximum slope methods were analysed to obtain depths to basements, also lineaments trend and 3-D surface plots were analsed. The results indicate a dominant NE-SW orientation, four faults were also identified mostly at the edges of sediments- basement contacts. The depth to magnetic basement map reveals two identified sub-basins within two structural highs. The Afikpo area has a structural high (afikpo anticlinorium) with depth ranging from 0.8km – 1.8km which is flanked by a depression (graben) 2.0km – 4.0km, this sub-basin extends between Abanwan to Amagu (ebonyi state) and extents to Biakpan (cross river state).also another structural high occurs between Iyamoyong and Okumeritit (cross river state) 0.8km -1.8km as horst, this is flanked by another depression (graben) within the Mkpani – Ugep area (cross river state) 2.0km -3.0 km in sediments thickness. Hydrocarbon prospectivity within the study area should be within the identified Grabens that has shown greater sediments accumulation while the areas identified as horst has less potentials for hydrocarbon prospectively.Keywords: Lineaments, sub-basin, basement, aeromagnetic, digitized.

A universal parameterized gradient-based method for photon beam field size determination.

To propose a universal, parameterized gradient-based method (PGM) for radiation field size determination. The PGM locates the beam profile's edge by parameterizing its penumbra region with a modified sigmoid function where the inflection point can be determined in a closed form. The parametrization was validated with filter-flattened (FF), flattening-filter-free (FFF) and wedged profiles measured on two Elekta linac models (Synergy and Versa HD). Gamma analysis with the delta dose function set to zero was used to quantitatively assess the parameterization accuracy. Field sizes of FF beams were calculated with the PGM and the full width at half maximum (FWHM) methods for comparison. To assess the consistency of the PGM and the FWHM method with geometric scaling across different depths, the calculated field size at a reference depth was scaled to other depths and compared with the field sizes calculated from the measured profiles. The method was also validated against a maximum-slope method (MSM) with wedge and FFF profiles. We also evaluated the robustness of the three methods with respect to measurement noise, varying scanning step sizes, detector characteristics, and beam energy/modality. Small distance-to-agreement (0.02±0.02mm) between the measured and parameterized penumbra region was observed for all profiles. The differences between the field sizes calculated with the FWHM method and the PGM were consistent (0.9±0.3mm), with the FWHM method yielding larger values. With geometrical scaling, the PGM and the FWHM method produced maximum differences of 0.26 and 1.16mm, respectively. For wedge and FFF beams, the mean differences relative to FF fields were 0.15±0.09mm and 0.57±0.91mm for the PGM and the MSM, respectively. The PGM was also found to produce more consistent results than the FWHM method and the MSM when measurement noise, scanning step size, detector characteristics, and beam energy/modality changed. The proposed PGM is universally applicable to all beam modalities (FF, wedge and FFF) for accurate field size determination. Compared to the FWHM and the MSM, it is more robust to variations in measurement condition and detection system.

Computed Tomography Perfusion Following Transarterial Chemoembolization of Hepatocellular Carcinoma: A Feasibility Study in the Early Period.

The aim of this study was to assess the feasibility of computed tomography (CT) perfusion in early follow-up after transarterial chemoembolization (TACE) of hepatocellular carcinoma (HCC). Fifteen patients with a total of 16 HCC who were referred to our institution for TACE were included in the study. Computed tomography perfusion was performed within 1 to 3 days before and 4 to 7 days after TACE. Multiphase contrast-enhanced CT was performed 35 (SD, 20) days after TACE. Hepatic arterial blood flow and portal venous blood flow, as well as the perfusion index (PI), were calculated for each HCC using the dual input maximum slope method. Visual grading of the PI and visual grading of the amount of deposition of embolic material within the HCC were performed using a 6-step scale. Differences in perfusion before and after TACE and correlation of perfusion before TACE with the amount of embolization material depositions 1 week and 1 month after TACE were tested. No statistically significant correlation was found between pre-TACE perfusion parameters and the amount of embolization material deposition in the post-TACE studies. There was no statistically significant difference between pre- and post-TACE arterial blood flow and portal venous blood flow, whereas PI was significantly lower after TACE. Congruently, visual grading of PI was statistically significantly lower after TACE. There was no statistically significant difference in quantitative pre-TACE and post-TACE PI between tumors, which showed hypervascularization in the multiphase follow-up CT and tumors that did not show hypervascularization. However, tumors that showed hypervascularization in the multiphase follow-up CT had significantly higher visual grading of PI after TACE than tumors that did not show hypervascularization. Our findings indicate that visual interpretation of the PI of HCC derived from dual-input maximum slope CT perfusion may be an early predictor of response to TACE.

Dynamic contrast-enhanced perfusion area-detector CT assessed with various mathematical models: Its capability for therapeutic outcome prediction for non-small cell lung cancer patients with chemoradiotherapy as compared with that of FDG-PET/CT

PurposeTo directly compare the capability of dynamic first-pass contrast-enhanced (CE-) perfusion area-detector CT (ADCT) and PET/CT for early prediction of treatment response, disease progression and overall survival of non-small cell carcinoma (NSCLC) patients treated with chemoradiotherapy. Materials and methodsFifty-three consecutive Stage IIIB NSCLC patients who had undergone PET/CT, dynamic first-pass CE-perfusion ADCT, chemoradiotherapy, and follow-up examination were enrolled in this study. They were divided into two groups: 1) complete or partial response (CR+PR) and 2) stable or progressive disease (SD+PD). Pulmonary arterial and systemic arterial perfusions and total perfusion were assessed at targeted lesions with the dual-input maximum slope method, permeability surface and distribution volume with the Patlak plot method, tumor perfusion with the single-input maximum slope method, and SUVmax, and results were averaged to determine final values for each patient. Next, step-wise regression analysis was used to determine which indices were the most useful for predicting therapeutic effect. Finally, overall survival of responders and non-responders assessed by using the indices that had a significant effect on prediction of therapeutic outcome was statistically compared. ResultsThe step-wise regression test showed that therapeutic effect (r2=0.63, p=0.01) was significantly affected by the following three factors in order of magnitude of impact: systemic arterial perfusion, total perfusion, and SUVmax. Mean overall survival showed a significant difference for total perfusion (p=0.003) and systemic arterial perfusion (p=0.04). ConclusionDynamic first-pass CE-perfusion ADCT as well as PET/CT are useful for treatment response prediction in NSCLC patients treated with chemoradiotherapy.

The single-blow transient testing technique for offset and wavy fins of compact plate-fin heat exchangers

A single-blow transient test technique is employed to measure the Colburn j factor versus Reynolds number characteristics of high efficiency compact heat exchanger surfaces having offset and wavy fins. Using the experimental data, the NTU values are estimated for 5 types of fins. The measured data is evaluated using the maximum slope method to obtain the corresponding heat transfer coefficient in terms of Colburn j factor, and then is compared with the available correlations of theoretical steady state CFD model. In this analysis, the effects of non-adiabatic side walls and longitudinal heat conduction on the exit fluid temperature response and NTU values are discussed. The test core pressure drops are also measured, and the pressure drop components of entrance, acceleration, core friction and exit losses are compared with the CFD results.

Low-dose volume perfusion computed tomography (VPCT) for diagnosis of solitary pulmonary nodules

ObjectiveTo characterize solitary pulmonary nodules (SPN) in terms of perfusion parameters using low-dose volume perfusion computed tomography (VPCT) and two different calculation methods, compare their results, look for interobserver agreement of measurements and investigate the feasibility of low-dose VPCT. Materials and methodsThis study was approved by the local Institutional Review Board and all patients provided written informed consent. Seventy-one patients (mean age 60.8 years ±9.6) with solitary pulmonary nodules were enrolled. Low-dose VPCT was performed for 38.63s covering the involved lung (70kV, 120mAs, 22 consecutive volume measurements, 50mL iodinated contrast, flow rate 4mL/s). Mean blood flow (BF), blood volume (BV) and k-trans were determined both with the maximum slope+Patlak vs. deconvolution method. Additionally, the difference of VPCT parameters between different type lesions and normal tissue was analyzed. Interobserver agreement for all perfusion parameters was calculated using intraclass correlation coefficients (ICC). The effective radiation dose of the VPCT and the total CT scan protocol were recorded. All CT findings were histologically confirmed by surgical intervention. ResultsThe mean lesion size was 18.6mm. Interobserver agreement measure with ICC shows high agreement between the measurements (κ=0.85). The effective radiation dose of the VPCT was 9.3mSv. The mean perfusion values for BF, BV and k-trans of 120.6mL/100g tissue/’, 11.6mL/100g tissue/’, and 18.5mL/100g tissue/’ for the deconvolution method, and 50.1mL/100g tissue/’, 11.6mL/100g tissue/’ and 24.3mL/100g tissue/’ for the maximum slope+Patlak method, which were significantly higher than those of normal muscle (20.7mL/100g tissue/’, 2.6mL/100g tissue/’, and 7.6mL/100g tissue/’ for the deconvolution method and 10.9mL/100g tissue/’, 3.1mL/100g tissue/’ and 8.1mL/100g tissue/’ for the maximum slope method). The best overall correlation between calculation methods was achieved for measurements of BF. ConclusionThe low-dose volume perfusion CT of the solitary pulmonary nodules can effectively reduce the radiation dose and non-invasively assess perfusion of SPN within the entire lesion volume.

Quantification of coronary flow using dynamic angiography with 320-detector row CT and motion coherence image processing: Detection of ischemia for intermediate coronary stenosis

ObjectivesAnatomical coronary stenosis is not always indicative of functional stenosis, particularly for intermediate coronary lesions. The purpose of this study is to propose a new method for quantifying coronary flow using dynamic CT angiography for the whole heart (heart-DCT) and investigate its ability for detecting ischemia from intermediate coronary stenosis. MethodsParticipants comprised 36 patients with coronary artery disease who underwent heart-DCT using 320-detector CT with tube voltage of 80kV and myocardial perfusion scintigraphy (MPS). Heart-DCT was continuously performed at mid-diastole throughout 15–25 cardiac cycles with prospective ECG-gating after bolus injection of contrast media (12–24ml). Dynamic datasets were computed into 90–100 data sets by motion coherence image processing (MCIP). Next, time-density curves (TDCs) for coronary arteries with a diameter >3mm were automatically calculated for all phases using MCIP. On the basis of the maximum slope method, coronary flow index (CFI) was defined as the ratio of the maximum upslope of coronary artery attenuation to the upslope of ascending aorta attenuation on the TDC, and was used to quantify coronary flow. CFIs for the proximal and distal sites of coronary arteries with mild-to-moderate stenosis were calculated. Coronary territories were categorized as non-ischemic or ischemic by MPS. Receiver-operating-characteristic (ROC) analysis was performed to determine the optimal cutoff for CFI to detect ischemia. ResultsDistal CFI was significantly lower for ischemia (0.26±0.08) than for non-ischemia (0.50±0.17, p<0.0001). No significant difference in proximal CFI was seen between ischemia (0.55±0.23) and non-ischemia (0.62±0.24). ROC analysis revealed 0.39 as the optimal cutoff for distal CFI to detect ischemia, with C-statistics of 0.91, 100% sensitivity, and 75% specificity. ConclusionsThis novel imaging technique allows coronary flow quantification using heart-DCT. Distal CFI can detect myocardial ischemia derived from intermediate coronary stenosis.

Dynamic contrast-enhanced perfusion area detector CT for non-small cell lung cancer patients: Influence of mathematical models on early prediction capabilities for treatment response and recurrence after chemoradiotherapy

PurposeTo determine the capability and influence of the mathematical method on dynamic contrast-enhanced (CE-) perfusion area detector CT (ADCT) for early prediction of treatment response as well as progression free and overall survival (PFS and OS) of non-small cell lung cancer (NSCLC) patients treated with chemoradiotherapy. Materials and methodsSixty-six consecutive stage III NSCLC patients underwent dynamic CE-perfusion ADCT examinations, chemoradiotherapy and follow-up examinations. Response Evaluation Criteria in Solid Tumors (RECIST) criteria were used to divide all patients into responders and non-responders. Differences in each of the indices for all targeted lesions between measurements obtained 2 weeks prior to the first and the third course of chemotherapy were determined for all patients. ROC analyses were employed to determine the capability of perfusion indices as markers for distinguishing RECIST responders from non-responders. To evaluate their capability for early prediction of therapeutic effect, OS of perfusion index-based responders and non-responders were compared by using the Kaplan–Meier method followed by log-rank test. ResultsArea under the curve (Az) for total perfusion by means of the dual-input maximum slope method was significantly larger than that of pulmonary arterial perfusion using the same method (p=0.007) and of perfusion with the single-input maximum slope method (p=0.007). Mean OS demonstrated significantly difference between responder- and non-responder groups for total perfusion (p=0.02). ConclusionMathematical models have significant influence on assessment for early prediction of treatment response, disease progression and overall survival using dynamic CE-perfusion ADCT for NSCLC patients treated with chemoradiotherapy.