Average Computed Tomography Research Articles

Cement stress predictions after anatomic total shoulder arthroplasty are correlated with preoperative glenoid bone quality

We hypothesized that biomechanical parameters typically associated with glenoid implant failure after anatomic total shoulder arthroplasty (aTSA) would be correlated with preoperative glenoid bone quality. We developed an objective automated method to quantify preoperative glenoid bone quality in different volumes of interest (VOIs): cortical bone, subchondral cortical plate, subchondral bone after reaming, subchondral trabecular bone, and successive layers of trabecular bone. Average computed tomography (CT) numbers (in Hounsfield units [HU]) were measured in each VOI from preoperative CT scans. In parallel, we built patient-specific finite element models of simulated aTSAs to predict cement stress, bone-cement interfacial stress, and bone strain around the glenoid implant. CT measurements and finite element predictions were obtained for 20 patients undergoing aTSA for primary glenohumeral osteoarthritis. We tested all linear correlations between preoperative patient characteristics (age, sex, height, weight, glenoid bone quality) and biomechanical predictions (cement stress, bone-cement interfacial stress, bone strain). Average CT numbers gradually decreased from cortical (717 HU) to subchondral and trabecular (362 HU) bone. Peak cement stress (4-10 MPa) was located within the keel hole, above the keel, or behind the glenoid implant backside. Cement stress, bone-cement interfacial stress, and bone strain were strongly negatively correlated with preoperative glenoid bone quality, particularly in VOIs behind the implant backside (subchondral trabecular bone) but also in deeper trabecular VOIs. Our numerical study suggests that preoperative glenoid bone quality is an important parameter to consider in aTSA, which may be associated with aseptic loosening of the glenoid implant. These initial results should now be confronted with clinical and radiologic outcomes.

Size Measurement and T-staging of Lung Adenocarcinomas Manifesting as Solid Nodules ≤30 mm on CT: Radiology-Pathology Correlation

This study aimed to compare long-axis diameter to average computed tomography (CT) diameter measurements of lung adenocarcinomas manifesting as solid lung nodules ≤30 mm on CT, as referenced to pathologic measurements, and to determine the impact of the two CT measurement approaches on tumor (T)-staging of nodules. This institutional review board-approved study included all 274 radiologic solid adenocarcinomas resected at our institution over 10 years. Two observers measured long- and short-axis diameters on pre-resection chest CT in lung and mediastinal windows. T-stages were determined. CT measurements and T-stages were compared to pathology measurements and T-stages using Wilcoxon signed rank test and McNemar test. Inter- and intraobserver variability was determined with intraclass correlation coefficients (ICC) and Bland-Altman plots. For lung and mediastinal windows, nodule size was significantly larger using long-axis diameter rather than average diameter (16.93 vs. 14.92 mm, P <.001; and 14.02 vs. 12.17 mm, P <.001, respectively). The correlation of CT with pathologic measurements was stronger with long-axis than with average diameter (ICC 0.808 vs. 0.730; and 0.731 vs. 0.621, respectively). Lung window measurements correlated stronger with pathology than mediastinal window measurements. CT T-stages differed from pathology T-stages in more than 20% of nodules (P <.001). Inter- and intraobserver variability was small with long-axis and average diameter (ICC range 0.96-0.991, and 0.970-0.993, respectively), but long-axis diameter showed wider scatter on Bland-Altman plots. Long-axis CT diameter is preferable for T-staging because it better reflects the pathology T-stage. Average CT diameter might be used for longitudinal nodule follow-up because it shows less measurement variability and is more conservative in size assessment.

Investigating different computed tomography techniques for internal target volume definition.

The aim of this work was to evaluate the various computed tomography (CT) techniques such as fast CT, slow CT, breath-hold (BH) CT, full-fan cone beam CT (FF-CBCT), half-fan CBCT (HF-CBCT), and average CT for delineation of internal target volume (ITV). In addition, these ITVs were compared against four-dimensional CT (4DCT) ITVs. Three-dimensional target motion was simulated using dynamic thorax phantom with target insert of diameter 3 cm for ten respiration data. CT images were acquired using a commercially available multislice CT scanner, and the CBCT images were acquired using On-Board-Imager. Average CT was generated by averaging 10 phases of 4DCT. ITVs were delineated for each CT by contouring the volume of the target ball; 4DCT ITVs were generated by merging all 10 phases target volumes. Incase of BH-CT, ITV was derived by boolean of CT phases 0%, 50%, and fast CT target volumes. ITVs determined by all CT and CBCT scans were significantly smaller (P < 0.05) than the 4DCT ITV, whereas there was no significant difference between average CT and 4DCT ITVs (P = 0.17). Fast CT had the maximum deviation (-46.1% ± 20.9%) followed by slow CT (-34.3% ± 11.0%) and FF-CBCT scans (-26.3% ± 8.7%). However, HF-CBCT scans (-12.9% ± 4.4%) and BH-CT scans (-11.1% ± 8.5%) resulted in almost similar deviation. On the contrary, average CT had the least deviation (-4.7% ± 9.8%). When comparing with 4DCT, all the CT techniques underestimated ITV. In the absence of 4DCT, the HF-CBCT target volumes with appropriate margin may be a reasonable approach for defining the ITV.

Thermal degradation of dynamic compressive strength for two mortars

Concrete-like materials are prone to simultaneous high temperature and blasting or impact load. Effects of thermally induced damage on the dynamic mechanical properties of concretes are thus paramount for hazard mitigation and blasting-proof design of concrete structures. We investigate the influence of thermally induced damage on the dynamic uniaxial compressive strength (UCS) of two mortars. The specimens were manufactured in cylindrical shape and heat-treated at 150°C, 250°C, 350°C, 450°C, 600°C and 850°C, before being tested at room temperature of 25°C with a split Hopkinson pressure bar (SHPB) apparatus. X-ray Computer Tomography (CT) scanning was used to quantify the thermally induced micro-cracks and chemical changes of two mortar specimens in terms of the average CT value. In addition, P-wave velocities and densities of two mortars were also measured before dynamic tests. The CT value, P-wave velocity and density decrease with the increase of the heat-treatment temperature. These observations are explained by the evolution of micro-structures such as the increase of micro-cracks and the undesirable chemical reactions in the mortar specimens. The results of dynamic tests show that the dynamic UCS increases with the loading rate and deceases with the increase of the heat-treatment temperature. The thermally induced damage is a combination of (a) the thermally induced micro-cracks and various chemical changes (which is characterized by the CT value), and (b) the deterioration of the binding property of reaction products. Thus the damage variable is introduced to quantify the thermally induced damage for two mortars. The formula for describing the dependence of the dynamic UCS on the thermal effect and the loading rate effect is established using the damage variable. The formula predicts the trend of the dynamic UCS for two mortars well.

Correlation of features of chest computed tomographic scans with histologic subtypes of thymoma according to the World Health Organisation classification in asymptomatic patients

Objective To assess the computed tomographic (CT) features of various subtypes of thymic epithelial neoplasms on the basis of the World Health Organization (WHO) classification especially in asymptomatic patients, and provide reference for the clinical treatment strategy of asymptomatic patients with thymoma. Methods We reviewed preoperative CT imaging and postoperative pathological results for 61 thymoma patients who had undergone thymectomy, and assessed the differences in CT features between the low-risk thymoma (type A, B) and the high-risk thymoma (type B1, B2, B3 and C). Results There were no significant differences between low-risk thymoma and high-risk thymoma in the gender (P=0.884), age (P=0.579), maximum diameter (P=0.851), mean diameter(P=0.904) or shape of tumor(P=0.437). However, there were significant differences between the two groups of thymoma in the average CT value on contrast-enhanced images (P=0.001), boundary (P=0.000), homogeneity (P=0.029), calcification (P=0.019), cystic degeneration or necrosis (P=0.000) and involvement of adjacent tissues (P=0.000). The receiver operating characteristic (ROC) curve analysis revealed an average CT value of 68.31 HU on contrast-enhanced images could produce 73.5% sensitivity and 77.8% specificity in determining low risk subtypes, and the area under the curve was 0.76 when the CT value reached this best cutoff point. Conclusion Some features of CT have a certain value in distinguishing low-risk thymoma and high-risk thymoma. A combined prediction using these variables will provide a reference for appropriate therapeutic strategies of TETs patients, especially the asymptomatic ones. Key words: Thymoma; CT imaging feature; World Health Organisation classification

Estimation of Postmortem Interval Using the Radiological Techniques, Computed Tomography: A Pilot Study

Estimation of postmortem interval (PMI) has been an important and difficult subject in the forensic study. It is a primary task of forensic work, and it can help guide the work in field investigation. With the development of computed tomography (CT) technology, CT imaging techniques are now being more frequently applied to the field of forensic medicine. This study used CT imaging techniques to observe area changes in different tissues and organs of rabbits after death and the changing pattern of the average CT values in the organs. The study analyzed the relationship between the CT values of different organs and PMI with the imaging software Max Viewer and obtained multiparameter nonlinear regression equation of the different organs, and the study provided an objective and accurate method and reference information for the estimation of PMI in the forensic medicine. In forensic science, PMI refers to the time interval between the discovery or inspection of corpse and the time of death. CT, magnetic resonance imaging, and other imaging techniques have become important means of clinical examinations over the years. Although some scholars in our country have used modern radiological techniques in various fields of forensic science, such as estimation of injury time, personal identification of bodies, analysis of the cause of death, determination of the causes of injury, and identification of the foreign substances of bodies, there are only a few studies on the estimation of time of death. We detected the process of subtle changes in adult rabbits after death, the shape and size of tissues and organs, and the relationship between adjacent organs in three-dimensional space in an effort to develop new method for the estimation of PMI. The bodies of the dead rabbits were stored at 20°C room temperature, sealed condition, and prevented exposure to flesh flies. The dead rabbits were randomly divided into comparison group and experimental group. The whole-body CT scans were performed on the experimental group of rabbits at different PMIs. NeuViz dual-slice spiral CT scanner (made by Neusoft Medical in China, 2 mm × 10 mm high-speed rare earth ceramic detector) is a 360° scan that could obtain two images, capable of providing a wide range of high-speed continuous spiral scan. Max Viewer (Version: 1.0.0131, Neusoft, Shenyang, China) is a CT image viewing software developed by Neusoft Medical. The software can be used to view and process images in various common methods and to measure a number of parameters, such as length, area, angle, and CT values. Statistical analysis was performed using SPSS1 Statistics 19.0 (SPSS, Inc., Chicago, IL, USA). A P ≤ 0.05 was considered statistically significant. We obtained the binomial regression equation of the CT values and the related coefficient (R2). In the future, we suggests that comprehensive analyses of various indicators of different organs could establish a diversified pattern to remedy the deficiencies and make the study of PMI estimation more scientific and enhance the operability.

Impact of moving target on measurement accuracy in 3D and 4D PET imaging—a phantom study

PurposeThe purpose of this study was to evaluate the impact of tumor motion on maximum standardized uptake value (SUVmax) and metabolic tumor volume (MTV) measurements in both 3-dimensional and respiratory-correlated, 4-dimensional positron emission tomography (PET) imaging. We also evaluated the effect of implementing different attenuation correction methods in 4-dimensional PET image reconstruction on SUVmax and MTV. Methods and materialsAn anthropomorphic thorax phantom with a spherical ball as a surrogate for a tumor was used. Different types of motion were imposed on the ball to mimic a patient's breathing motion. Three-dimensional PET imaging of the phantom without tumor motion was performed and used as the reference. The ball was then set in motion with different breathing motion traces and imaged with both 3- and 4-dimensional PET methods. The clinical 4-dimensional PET imaging protocol was modified so that 3 different types of attenuation correction images were used for reconstructions: the same free-breathing computed tomography (CT) for all PET phases, the same average intensity projection CT for all PET phases, and 4-dimensional CT for phase-matched attenuation correction. Tumor SUVmax and MTV values that were measured from the moving phantom were compared with the reference values. ResultsSUVmax that was measured in 3-dimensional PET imaging was different from the reference value by 20.4% on average for the motions that were investigated; this difference decreased to 2.6% with 4-dimensional PET imaging. The measurement of MTV in 4-dimensional PET also showed a similar magnitude of reduction of deviation compared with 3-dimensional PET. Four-dimensional PET with use of phase-matched 4-dimensional CT for attenuation correction showed less variation in SUVmax and MTV among phases compared with 4-dimensional PET with free-breathing CT or average intensity projection CT for attenuation correction. ConclusionsFour-dimensional PET imaging reduces the impact of motion on measured SUVmax and MTV when compared with 3-dimensional PET imaging. Clinical 4-dimensional PET imaging protocols should consider phase-matched 4-dimensional CT imaging for attenuation correction to achieve more accurate measurements.

The findings of CT and MRI in patients with metanephric adenoma.

BackgroundMetanephric adenoma (MA) is a benign renal tumor that is difficult to distinguish from a malignant tumor via traditional radiography. The diagnosis of MA is often dependent on postsurgical histopathological examination. In the present report, the imaging features of MA on computer tomography (CT) and magnetic resonance imaging (MRI) were retrospectively evaluated.MethodsEight MA patients, 17–67 years of age, were pathologically confirmed and recruited between April 2009 and November 2014. Four of the eight patients were female. All patients underwent CT scanning, and one patient underwent MRI scanning. Three patients underwent CTA of the renal arteries. All patients underwent resection surgery (radical nephrectomy in five and nephron-sparing surgery in three patients).ResultsThe average tumor size was 44.0 ± 23.6 mm. The lesions in 87.5 % cases were located both in the renal cortex and medulla and exhibited exophytic growth. Plain CT showed that MA tumors were solid, and the average CT value was 37.9 ± 6.7 HU. Dynamic contrast-enhanced CT revealed that enhanced degrees of MA tumors in the renal cortex, renal parenchymal, and pelvic phase were all lower than that of normal renal parenchyma. A slight enhancement in the renal cortex phase and an even higher enhancement in the renal parenchymal phase were observed in seven of the cases. Progressive enhancement in the pelvic phase was found in five cases and a slight decreased enhancement in the pelvic phase in two cases. MRI revealed that MA tumor was isointense on T1WI and isointense on T2WI with some slightly hyperintense areas in the center. CTA of the renal arteries revealed the nutrient artery in one patient and no nutrient artery in two. Immunohistochemical experiments demonstrated that most tumor cells were positive for vimentin, CK, and EMA.ConclusionsMA is a rare benign renal neoplasm. Detailed knowledge of the CT and MRI characteristics of MA plays an important role in MA diagnosis and treatment.

Effects of carbonation and freeze-thaw cycles on microstructure of concrete

The hydraulic concrete durability under the alternation of freeze-thaw and carbonation has been systematically investigated in this work, where both the micro part and the microscopic characteristics of concrete interface were analyzed based on computed tomography (CT) test and scanning electron microscopy (SEM). Average CT numbers of each section, declined at water-cement ratio of 0.35, increased at 0.45, and changed a little at 0.55. The specimen in the absence of fly ash exhibited less types of hydration products and the surface was observed to be a needle-like ettringite, with a relatively dense overall structure. However, with the increase of fly ash content, pores and micro-cracks of specimen structure increased. Hexagonal flake calcium hydroxide, present in the specimen after the first carbonation, was negligible in the test pieces of the first freezethaw where the main hydration products were ettringite and calcium silicate gel. Regular hexagonal plates of calcium hydroxide exhibited in the interior of the specimen in which charring first occurred but calcium hydroxide rarely existed in the interior of the specimen in which freeze-thaw first occurred.

MO-FG-BRA-04: A Novel Time Weighted Density Correction for Stereotactic Lung Radiotherapy: A Phantom Study

Purpose: Conventional treatment plans for lung radiotherapy are created using either the free breathing (FB) scheme which represents the tumor at an arbitrary breathing phase of the patient's respiratory cycle, or the average computed tomography (ACT) intensity projection over 10-binned phases. Neither method is entirely accurate because of the absence of time dependence of tumor movement. In the present “Hybrid” method, the HU of tumor in 3D space is determined by relative weighting of the HU of the tumor and lung in proportion to the time they spend at that location during the entire breathing cycle. Methods: A Quasar respiratory motion phantom was employed to simulate lung tumor movement. Utilizing 4DCT image scans, volumetric modulated arc therapy (VMAT) plans were generated for three treatment planning scenarios which included conventional FB and ACT schemes, along with a third alternative Hybrid approach. Our internal target volume (ITV) hybrid structure was created using Boolean operation in Eclipse (ver. 11) treatment planning system, where independent sub-regions created by the gross tumor volume (GTV) overlap from the 10 motion phases were each assigned a time weighted CT value. The dose-volume-histograms (DVH) for each scheme were compared and analyzed. Results: Using our hybrid technique, we have demonstrated a reduction of 1.9% – 3.4% in total monitor units with respect to conventional treatment planning strategies, along with a 6 fold improvement in high dose spillage over the FB plan. The higher density ACT and Hybrid schemes also produced a slight enhancement in target conformity and reduction in low dose spillage. Conclusion: All treatment plans created in this study exceeded RTOG protocol criteria. Our results determine the free breathing approach yields an inaccurate account of the target treatment density. A significant decrease in unnecessary lung irradiation can be achieved by implementing Hybrid HU method with ACT method second best.

X‐ray CT‐Derived Soil Characteristics Explain Varying Air, Water, and Solute Transport Properties across a Loamy Field

Core Ideas We used CT‐derived parameters to explain solute, water, and air transport at field scale. CTmatrix was found to be the best parameter to explain solute transport. Limiting macroporosity gave the highest correlations with water and air transport. Combining macroporosity and CTmatrix improved the relationships of water and air flow. The characterization of soil pore space geometry is important for explaining fluxes of air, water, and solutes through soil and understanding soil hydrogeochemical functions. X‐ray computed tomography (CT) can be applied for this characterization, and in this study CT‐derived parameters were used to explain water, air, and solute transport through soil. Forty‐five soil columns (20 by 20 cm) were collected from an agricultural field in Estrup, Denmark, and subsequently scanned using a medical CT scanner. Nonreactive tracer leaching experiments were performed in the laboratory along with measurements of air permeability (Ka) and saturated hydraulic conductivity (Ksat). The CT number of the matrix (CTmatrix), which represents the moist bulk density of the soil matrix, was obtained from the CT scans as the average CT number of the voxels in the grayscale image excluding macropores and stones. The CTmatrix showed the best relationships with the solute transport characteristics, especially the time by which 5% of the applied mass of tritium was leached, known as the 5% arrival time (t0.05). The CT‐derived macroporosity (pores &gt;1.2 mm) was correlated with Ka and log10(Ksat). The correlation improved when the limiting macroporosity (the minimum macroporosity for every 0.6‐mm layer along the soil column) was used, suggesting that soil layers with the narrowest macropore section restricted the flow through the whole soil column. Water, air, and solute transport were related with the CT‐derived parameters by using a best subsets regression analysis. The regression coefficients improved using CTmatrix, limiting macroporosity, and genus density, while the best model for t0.05 used CTmatrix only. The scanning resolution and the time for soil structure development after mechanical activities could be factors that increased the uncertainty of the relationships. Nevertheless, the results confirmed the potential of X‐ray CT visualization techniques for estimating fluxes through soil at the field scale.

Exploratory Study of 4D versus 3D Robust Optimization in Intensity Modulated Proton Therapy for Lung Cancer

The purpose of this study was to compare the impact of uncertainties and interplay on 3-dimensional (3D) and 4D robustly optimized intensity modulated proton therapy (IMPT) plans for lung cancer in an exploratory methodology study. IMPT plans were created for 11 nonrandomly selected non-small cell lung cancer (NSCLC) cases: 3D robustly optimized plans on average CTs with internal gross tumor volume density overridden to irradiate internal target volume, and 4D robustly optimized plans on 4D computed tomography (CT) to irradiate clinical target volume (CTV). Regular fractionation (66 Gy [relative biological effectiveness; RBE] in 33 fractions) was considered. In 4D optimization, the CTV of individual phases received nonuniform doses to achieve a uniform cumulative dose. The root-mean-square dose-volume histograms (RVH) measured the sensitivity of the dose to uncertainties, and the areas under the RVH curve (AUCs) were used to evaluate plan robustness. Dose evaluation software modeled time-dependent spot delivery to incorporate interplay effect with randomized starting phases of each field per fraction. Dose-volume histogram (DVH) indices comparing CTV coverage, homogeneity, and normal tissue sparing were evaluated using Wilcoxon signed rank test. 4D robust optimization plans led to smaller AUC for CTV (14.26 vs 18.61, respectively; P=.001), better CTV coverage (Gy [RBE]) (D95% CTV: 60.6 vs 55.2, respectively; P=.001), and better CTV homogeneity (D5%-D95% CTV: 10.3 vs 17.7, respectively; P=.002) in the face of uncertainties. With interplay effect considered, 4D robust optimization produced plans with better target coverage (D95% CTV: 64.5 vs 63.8, respectively; P=.0068), comparable target homogeneity, and comparable normal tissue protection. The benefits from 4D robust optimization were most obvious for the 2 typical stage III lung cancer patients. Our exploratory methodology study showed that, compared to 3D robust optimization, 4D robust optimization produced significantly more robust and interplay-effect-resistant plans for targets with comparable dose distributions for normal tissues. A further study with a larger and more realistic patient population is warranted to generalize the conclusions.

Optimization of scan timing for aortic computed tomographic angiography using the test bolus injection technique.

With fast computed tomography (CT), it is possible for the scanning to outpace the contrast medium bolus during aortic CT angiography (CTA). To evaluate the effectiveness of a new method for reducing the risk of outpacing in which the scan start timing (ST) and speed can be estimated from the peak enhancement time measured at the femoral artery using a single test-bolus injection (femoral artery test injection method [FTI method]). In 30 cases of aortic CTA, we measured the time to peak enhancement at the femoral artery (TPF) and the ascending aorta (TPA) with test-bolus injection performed twice in each examination. From the resultant linear relationship between TPF and transit time (TT = TPF - TPA), we developed a method for determining the ST and TT from TPF. One hundred patients were assigned to two groups: FTI and bolus tracking (BT), each with 50 patients. CT values were measured in main vessels (ascending aorta, descending aorta, femoral artery). The CT values of the vessels and the rate of cases with more than 300 HU (good cases) were compared between the two groups. The enhancement in the FTI method was significantly higher than that of the BT method (average CT values: FTI, 388.3 ± 52.4; BT, 281.2 ± 59.1; P < 0.001). The rates of good cases for FTI and BT were 86.0% and 46.0%, respectively. The FTI method was very effective in reducing the risk of outpacing of the contrast medium transit in aortic CTA without the need for an additional contrast medium dose.

Radiologic Predictors for Clinical Stage IA Lung Adenocarcinoma with Ground Glass Components: A Multi-Center Study of Long-Term Outcomes.

ObjectiveThis study was to define preoperative predictors from radiologic findings for the pathologic risk groups based on long-term surgical outcomes, in the aim to help guide individualized patient management.MethodsWe retrospectively reviewed 321 consecutive patients with clinical stage IA lung adenocarcinoma with ground glass component on computed tomography (CT) scanning. Pathologic diagnosis for resection specimens was based on the 2011 IASLC/ATS/ERS classification of lung adenocarcinoma. Patients were classified into different pathologic risk grading groups based on their lymph node status, local regional recurrence and overall survival. Radiologic characteristics of the pulmonary nodules were re-evaluated by reconstructed three-dimension CT (3D-CT). Univariate and multivariate analysis identifies independent radiologic predictors from tumor diameter, total volume (TV), average CT value (AVG), and solid-to-tumor (S/T) ratio. Receiver operating characteristic curves (ROC) studies were carried out to determine the cutoff value(s) for the predictor(s). Univariate cox regression model was used to determine the clinical significance of the above findings.ResultsA total of 321 patients with clinical stage IA lung adenocarcinoma with ground glass components were included in our study. Patients were classified into two pathologic low- and high- risk groups based on their distinguished surgical outcomes. A total of 134 patients fell into the low-risk group. Univariate and multivariate analyses identified AVG (HR: 32.210, 95% CI: 3.020–79.689, P<0.001) and S/T ratio (HR: 12.212, 95% CI: 5.441–27.408, P<0.001) as independent predictors for pathologic risk grading. ROC curves studies suggested the optimal cut-off values for AVG and S/T ratio were-198 (area under the curve [AUC] 0.921), 2.9 (AUC 0.996) and 54% (AUC 0.907), respectively. The tumor diameter and TV were excluded for the low AUCs (0.778 and 0.767). Both the cutoff values of AVG and S/T ratio were correlated with pathologic risk classification (p<0.001). Univariate Cox regression model identified clinical risk classification (RR: 3.011, 95%CI: 0.796–7.882, P = 0.095) as a good predictor for recurrence-free survival (RFS) in patients with clinical stage IA lung adenocarcinoma. Statistical significance of 5-year OS and RFS was noted among clinical low-, moderate- and high-risk groups (log-rank, p = 0.024 and 0.010).ConclusionsThe AVG and the S/T ratio by reconstructed 3D-CT are important preoperative radiologic predictors for pathologic risk grading. The two cutoff values of AVG and S/T ratio are recommended in decision-making for patients with clinical stage IA lung adenocarcinoma with ground glass components.

Percutaneous cryoablation of renal masses under CT fluoroscopy: radiation doses to the patient and interventionalist.

Computed tomographic (CT) fluoroscopy-guided percutaneous cryoablation is an effective therapeutic method used to treat focal renal masses. The purpose of this study is to quantify the radiation dose to the patient and interventional radiologist during percutaneous cryoablation of renal masses using CT fluoroscopic guidance. Over a 1-year period, the CT fluoroscopy time during percutaneous cryoablation of renal masses was recorded in 41 patients. The level of complexity of each procedure was designated as simple, intermediate, or complex. Patient organ radiation doses were estimated using an anthropomorphic model. Dose to the interventional radiologist was estimated using ion chamber survey meters. The average CT fluoroscopy time for technically simple cases was 47s, 126s for intermediate cases, and 264s for complex cases. The relative risk of hematologic stomach and liver malignancy in patients undergoing this procedure was 1.003-1.074. The lifetime attributable risk of cancer ranged from 2 to 58, with the highest risk in younger patients for developing leukemia. The estimated radiation dose to the interventionalist without lead shielding was 390mR (3.9mGy) per year of cases. The radiation risk to the patient during CT fluoroscopy-guided percutaneous renal mass cryoablation is, as expected, related to procedure complexity. Quantification of patient organ radiation dose was estimated using an anthropomorphic model. This information, along with the associated relative risk of malignancy, may assist in evaluating risks of the procedure, particularly in younger patients. The radiation dose to the interventionist is low regardless of procedure complexity, but highlights the importance of lead shielding.

Posterior C2 Instrumentation in the Management of Trauma: Accuracy and Risks Associated with Four Techniques

Introduction Posterior instrumentation of C2 is important in treating occipitocervical, atlanto-axial, and subaxial spinal injuries. The variable C2 anatomy can make instrumentation challenging and prone to potentially severe and even life-threatening complications. The goal of this study was to (1) evaluate a large series of posterior C2 screws to determine accuracy as assessed by computed tomography (CT) scan, (2) assess dimensions of “safe bony windows” with CT, and (3) assess the perioperative complication rate related to errant screw placement. We hypothesize that the evolution of a greater variety of options for C2 fixation and the ability to tailor these techniques to patients' specific anatomy has resulted in decreased complications and increased accuracy. Material and Methods A retrospective review of a single Level I trauma center spine database was assessed to identify all patients with operative management for traumatic conditions with C2 instrumentation between December 2002 and September 2008. Radiographic analysis included evaluation of pre- and postoperative CT scans to quantify the patients' bony anatomy as well as to classify the accuracy of C2 screw placement. All C2 screws were graded using the following definitions: Type I: Screw threads completely within the bony cortex. Type II: Less than half the diameter of the screw violates the surrounding cortex. Type III: Clear violation of the transverse foramen or spinal canal. Results A total of 169 patients (99 males and 70 females) underwent posterior C2 screw fixation for traumatic conditions of the spine, including 23 atlanto-occipital dissociations, 16 unstable C1 ring injuries, 79 dens fractures, 9 Hangman fractures, 8 other C2 fractures, 3 C2 hyperextension injuries, 4 C2–C3 flexion–distraction injuries, 14 subaxial injuries, and 19 odontoid nonunions. Average CT measurements of pedicle height, axial width, and laminar width were 8.1 mm (standard deviation 2.1 mm), 5.8 mm (1.9 mm), and 5.7 mm (1.5 mm), respectively, with males having larger pedicle height ( p &lt; 0.001), pedicle width ( p &lt; 0.001), and laminar width ( p &lt; 0.022). A total of 324 screws underwent CT analysis and chart review. A total of 169 pedicle, 85 trans-articular, 50 laminar, and 20 short pars screws were placed with 80.6, 84.4, 96, and 94.4% accuracy rates (Grade I vs. II and III), respectively. Overall 85% of the screws were rated as being in the ideal location. There were no cases of known vertebral artery injury at the time of surgery. Two pedicle screws were unacceptably placed (Grade III). Both patients had screws encroaching on the vertebral artery foramen: one patient had a vertebral artery occlusion and the other had a Grade I dissection documented on CT angiogram without clinical signs of stroke or emboli as measured on transcranial Doppler. No neurological injuries resulted from instrumentation. Conclusion Our findings demonstrate a lower than previously reported incidence of complications associated with posterior C2 screw placement. In the management of 169 patients with 324 screws, only 2 patients had vascular injuries, neither of whom had any sequelae. The multiple techniques of posterior C2 fixation that are currently available allow for unprecedented flexibility in determining which technique is best suited for a given patient's anatomy.

Ischemic colitis: spectrum of CT findings, sites of involvement and severity.

To summarize the frequency of findings on IV contrast, enhanced computer tomography (CT) in 335 patients with pathologically proven ischemic colitis (IC) determine the most frequent locations and patterns of involvement and establish the correlation of these findings with the severity of IC. 231 patients were excluded for not having a concomitant CT or for having underlying comorbidities. 104 cases were analyzed. Scans were evaluated for abnormal wall enhancement (AE), bowel wall thickening (BWT), bowel dilatation (DIL), mesenteric fat stranding (FS), venous engorgement (VE), pericolonic free fluid (FF), and pneumatosis (PN) and portomesenteric venous gas. Segmental versus pancolonic involvement was noted. Severity was determined by histopathology criteria. Data obtained are as follows: female to male incidence, 69% (70) vs. 31% (34); average age, 64.5; and positive CT, 102/104 (98.1%). The most frequent findings include FS (88%), BWT (88%), and AE (82%) regardless of severity of involvement. Statistically significant increased risk ratio and likelihood of severe ischemia for PN, DIL, and FF individually. BWT, DIL, FS, FF, VE, and PN together have a probability for severe IC of 91.8%. A correlation between fewer findings and milder IC was found (R (2) = 0.6771). The most frequently involved segments: descending (64%) and sigmoid colon (54%). Splenic flexure (SF) was infrequently involved (n = 8, 7.84%). Females had two times higher incidence of IC. The most frequent CT findings in IC are FS, BWT, and AE regardless of the severity. PN is suggestive of severe IC. Segmental involvement is the predominant pattern. The distal colon is more frequently involved. SF contrary to the conventional literature is not disproportionately involved in IC.

Clinical evaluation of respiration-induced attenuation uncertainties in pulmonary 3D PET/CT.

BackgroundIn contemporary positron emission tomography (PET)/computed tomography (CT) scanners, PET attenuation correction is performed by means of a CT-based attenuation map. Respiratory motion can however induce offsets between the PET and CT data. Studies have demonstrated that these offsets can cause errors in quantitative PET measures. The purpose of this study is to quantify the effects of respiration-induced CT differences on the attenuation correction of pulmonary 18-fluordeoxyglucose (FDG) 3D PET/CT in a patient population and to investigate contributing factors.MethodsFor 32 lung cancer patients, 3D-CT, 4D-PET and 4D-CT data were acquired. The 4D FDG PET data were attenuation corrected (AC) using a free-breathing 3D-CT (3D-AC), the end-inspiration CT (EI-AC), the end-expiration CT (EE-AC) or phase-by-phase (P-AC). After reconstruction and AC, the 4D-PET data were averaged. In the 4Davg data, we measured maximum tumour standardised uptake value (SUV)max in the tumour, SUVmean in a lung volume of interest (VOI) and average SUV (SUVmean) in a muscle VOI. On the 4D-CT, we measured the lung volume differences and CT number changes between inhale and exhale in the lung VOI.ResultsCompared to P-AC, we found −2.3% (range −9.7% to 1.2%) lower tumour SUVmax in EI-AC and 2.0% (range −0.9% to 9.5%) higher SUVmax in EE-AC. No differences in the muscle SUV were found. The use of 3D-AC led to respiration-induced SUVmax differences up to 20% compared to the use of P-AC.SUVmean differences in the lung VOI between EI-AC and EE-AC correlated to average CT differences in this region (ρ = 0.83). SUVmax differences in the tumour correlated to the volume changes of the lungs (ρ = −0.55) and the motion amplitude of the tumour (ρ = 0.53), both as measured on the 4D-CT.ConclusionsRespiration-induced CT variations in clinical data can in extreme cases lead to SUV effects larger than 10% on PET attenuation correction. These differences were case specific and correlated to differences in CT number in the lungs.

A Curve Fitting Approach Using ANN for Converting CT Number to Linear Attenuation Coefficient for CT-based PET Attenuation Correction

Energy-mapping, the conversion of linear attenuation coefficients ( $\mu $ ) calculated at the effective computed tomography (CT) energy to those corresponding to 511 keV, is an important step in CT-based attenuation correction (CTAC) for positron emission tomography (PET) quantification. The aim of this study was to implement energy-mapping step by using curve fitting ability of artificial neural network (ANN). Eleven digital phantoms simulated by Geant4 application for tomographic emission (GATE) and 12 physical phantoms composed of various volume concentrations of iodine contrast were used in this study to generate energy-mapping curves by acquiring average CT values and linear attenuation coefficients at 511 keV of these phantoms. The curves were built with ANN toolbox in MATLAB. To evaluate the effectiveness of the proposed method, another two digital phantoms (liver and spine-bone) and three physical phantoms (volume concentrations of 3%, 10% and 20%) were used to compare the energy-mapping curves built by ANN and bilinear transformation, and a semi-quantitative analysis was proceeded by injecting 0.5 mCi FDG into a SD rat for micro-PET scanning. The results showed that the percentage relative difference (PRD) values of digital liver and spine-bone phantom are 5.46% and 1.28% based on ANN, and 19.21% and 1.87% based on bilinear transformation. For 3%, 10% and 20% physical phantoms, the PRD values of ANN curve are 0.91%, 0.70% and 3.70%, and the PRD values of bilinear transformation are 3.80%, 1.44% and 4.30%, respectively. Both digital and physical phantoms indicated that the ANN curve can achieve better performance than bilinear transformation. The semi-quantitative analysis of rat PET images showed that the ANN curve can reduce the inaccuracy caused by attenuation effect from 13.75% to 4.43% in brain tissue, and 23.26% to 9.41% in heart tissue. On the other hand, the inaccuracy remained 6.47% and 11.51% in brain and heart tissue when the bilinear transformation was used. Overall, it can be concluded that the bilinear transformation method resulted in considerable bias and the newly proposed calibration curve built by ANN could achieve better results with acceptable accuracy.

Vascular calcification and bone mineral density in recurrent kidney stone formers.

Recent epidemiologic studies have provided evidence for an association between nephrolithiasis and cardiovascular disease, although the underlying mechanism is still unclear. Vascular calcification (VC) is a strong predictor of cardiovascular morbidity and the hypothesis explored in this study is that VC is more prevalent in calcium kidney stone formers (KSFs). The aims of this study were to determine (1) whether recurrent calcium KSFs have more VC and osteoporosis compared with controls and (2) whether hypercalciuria is related to VC in KSFs. This is a retrospective, matched case-control study that included KSFs attending an outpatient nephrology clinic of the Royal Free Hospital (London, UK) from 2011 to 2014. Age- and sex-matched non-stone formers were drawn from a list of potential living kidney donors from the same hospital. A total of 111 patients were investigated, of which 57 were KSFs and 54 were healthy controls. Abdominal aortic calcification (AAC) and vertebral bone mineral density (BMD) were assessed using available computed tomography (CT) imaging. The prevalence, severity, and associations of AAC and CT BMD between KSFs and non-stone formers were compared. Mean age was 47±14 years in KSFs and 47±13 in non-stone formers. Men represented 56% and 57% of KSFs and non-stone formers, respectively. The prevalence of AAC was similar in both groups (38% in KSFs versus 35% in controls, P=0.69). However, the AAC severity score (median [25th percentile, 75th percentile]) was significantly higher in KSFs compared with the control group (0 [0, 43] versus 0 [0, 10], P<0.001). In addition, the average CT BMD was significantly lower in KSFs (159±53 versus 194 ±48 Hounsfield units, P<0.001). A multivariate model adjusted for age, sex, high BP, diabetes, smoking status, and eGFR confirmed that KSFs have higher AAC scores and lower CT BMD compared with non-stone formers (P<0.001 for both). Among stone formers, the association between AAC score and hypercalciuria was not statistically significant (P=0.86). This study demonstrates that patients with calcium kidney stones suffer from significantly higher degrees of aortic calcification than age- and sex-matched non-stone formers, suggesting that VC may be an underlying mechanism explaining reported associations between nephrolithiasis and cardiovascular disease. Moreover, bone demineralization is more prominent in KSFs. However, more data are needed to confirm the possibility of potentially common underlying mechanisms leading to extraosseous calcium deposition and osteoporosis in KSFs.