Evaluation of postprocessing dual-energy quantitative computed tomography

CT scanners can be used to provide quantitative information on body composition. Its main application is for bone mineral content estimation within the lumbar vertebral body. This is usually done with a single-energy technique. The estimates obtained with this technique are influenced by the intravertebral fat content, which varies interindividually and with disease. Dual-energy techniques have been proposed to solve the fat-error, but their exact value is unknown. The aim of the studies presented in this thesis, is to evaluate different postprocessing dual-energy methods for quantitative computed tomography for bone mineral and fat content analysis within the trabecular region of the vertebral body. Comparison of these methods by transforming them to a standard set of equations, reveals that only two out of five methods would give optimal results (chapter 3). This is confirmed in phantom studies (chapter 4). In the phantom studies, two major problems for performing postprocessing DEQCT are encountered: 1) the accuracy of the tissue equivalence of reference materials or accuracy of tissue description and 2) the effective energy difference between the site of the vertebral body and the reference device. Using a patient simulation model, the influence of these disturbing factors on the accuracy of bone mineral and fat content estimation is evaluated for different clinical conditions (chapters 5 and 6). The precision of the bone mineral and fat content determination with postprocessing DEQCT is evaluated in chapter 7. In addition to an in vitro experiment, the precision is estimated using the patient simulation model. The results from chapters 5 through 7, show that postprocessing DEQCT can be of value in clinical practice. Postprocessing DEQCT should be used in longitudinal studies on bone mineral content changes, if significant changes in the bone marrow composition are anticipated. Furthermore, postprocessing DEQCT can be used for evaluation of fat content differences between groups of patients. Striking differences in the fat content estimates are seen in a number of patients with different metabolic disorders (chapter 8). It is concluded that the theoretical superb accuracy of bone mineral measurements obtained with postprocessing DEQCT, can be eliminated by practical problems such as improper tissue equivalence of the reference materials and energy differences between the region of interest and the reference device. More research is necessary to obtain an exact knowledge of the elemental compositions and mass densities of the various anatomical structures within the vertebral body, especially intravertebral fat tissue. Beam hardening corrections, implemented in the CT scanner, should be evaluated for their effect on OC

Total-liver-volume perfusion CT using 3-D image fusion to improve detection and characterization of liver metastases

The purpose of this study was to evaluate the feasibility of a totalliver- volume perfusion CT (CTP) technique for the detection and characterization of livermetastases. Twenty patients underwent helical CT of the total liver volume before and 11 times after intravenous contrast-material injection. To decrease distortion artifacts, all phases were co-registered using 3-D image fusion before creating blood-flow maps. Lesion-based sensitivity and specificity for liver metastases of first the conventional four phases (unenhanced, arterial, portal venous, and equilibrium) and later all 12 phases including blood-flow maps were determined as compared to intraoperative ultrasound and surgical exploration. Arterial and portal venous perfusion was calculated for normalappearing and metastatic liver tissue. Total-liver-volume perfusion values were comparable to studies using single-level CTP. Compared to fourphase CT, total -liver-volume CTP increased sensitivity to 89.2 from 78.4% (P=0.046) and specificity to 82.6 from 78.3% (P=0.074). Total - liver-volume CTP is a noninvasive, quantitative, and feasible technique. Preliminary results suggest an improved detection of liver metastases for CTP compared to four-phase CT

Accuracy and the influence of marrow fat on quantitative CT and dual-energy X-ray absorptiometry measurements of the femoral neck in vitro

Abstract Bone mineral measurements with quantitative computed tomography (QCT) and dual-energy X-ray absorptiometry (DXA) were compared with chemical analysis (ChA) to determine (1) the accuracy and (2) the influence of bone marrow fat. Total bone mass of 19 human femoral necks in vitro was determined with QCT and DXA before and after defatting. ChA consisted of defatting and decalcification of the femoral neck samples for determination of bone mineral mass (BmM) and amount of fat. The mean BmM was 4.49 g. Mean fat percentage was 37.2% (23.3%–48.5%). QCT, DXA and ChA before and after defatting were all highly correlated (r>0.96,p<0.0001). Before defatting the QCT values were on average 0.35 g less than BmM and the DXA values were on average 0.65 g less than BmM. After defatting, all bone mass values increased; QCT values were on average 0.30 g more than BmM and DXA values were 0.29 g less than BmM. It is concluded that bone mineral measurements of the femoral neck with QCT and DXA are highly correlated with the chemically determined bone mineral mass and that both techniques are influenced by the femoral fat content

Incremental prognostic value of hybrid [15O]H2O positron emission tomography-computed tomography: combining myocardial blood flow, coronary stenosis severity, and high-risk plaque morphology

AimsThis study sought to determine the prognostic value of combined functional testing using positron emission tomography (PET) perfusion imaging and anatomical testing using coronary computed tomography angiography (CCTA)-derived stenosis severity and plaque morphology in patients with suspected coronary artery disease (CAD).Methods and resultsIn this retrospective study, 539 patients referred for hybrid [15O]H2O PET-CT imaging because of suspected CAD were investigated. PET was used to determine myocardial blood flow (MBF), whereas CCTA images were evaluated for obstructive stenoses and high-risk plaque (HRP) morphology. Patients were followed up for the occurrence of all-cause death and non-fatal myocardial infarction (MI). During a median follow-up of 6.8 (interquartile range 4.8–7.8) years, 42 (7.8%) patients experienced events, including 23 (4.3%) deaths, and 19 (3.5%) MIs. Annualized event rates for normal vs. abnormal results of PET MBF, CCTA-derived stenosis, and HRP morphology were 0.6 vs. 2.1%, 0.4 vs. 2.1%, and 0.8 vs. 2.8%, respectively (P ConclusionPET-derived MBF, CCTA-derived stenosis severity, and HRP morphology were univariably associated with death and MI, whereas only stenosis severity and HRP morphology provided independent prognostic value.</div

Criteria for the selective use of chest computed tomography in blunt trauma patients

Item does not contain fulltextPURPOSE: The purpose of this study was to derive parameters that predict which high-energy blunt trauma patients should undergo computed tomography (CT) for detection of chest injury. METHODS: This observational study prospectively included consecutive patients (>or=16 years old) who underwent multidetector CT of the chest after a high-energy mechanism of blunt trauma in one trauma centre. RESULTS: We included 1,047 patients (median age, 37; 70% male), of whom 508 had chest injuries identified by CT. Using logistic regression, we identified nine predictors of chest injury presence on CT (age >or=55 years, abnormal chest physical examination, altered sensorium, abnormal thoracic spine physical examination, abnormal chest conventional radiography (CR), abnormal thoracic spine CR, abnormal pelvic CR or abdominal ultrasound, base excess or=1 positive predictors, 484 had injury on CT (95% of all 508 patients with injury). Of all 192 patients with no positive predictor, 24 (13%) had chest injury, of whom 4 (2%) had injuries that were considered clinically relevant. CONCLUSION: Omission of CT in patients without any positive predictor could reduce imaging frequency by 18%, while most clinically relevant chest injuries remain adequately detected.1 april 201