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

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

Colorectal liver metastases: Surgery versus thermal ablation (COLLISION) - a phase III single-blind prospective randomized controlled trial

Background: Radiofrequency ablation (RFA) and microwave ablation (MWA) are widely accepted techniques to eliminate small unresectable colorectal liver metastases (CRLM). Although previous studies labelled thermal ablation inferior to surgical resection, the apparent selection bias when comparing patients with unresectable disease to surgical candidates, the superior safety profile, and the competitive overall survival results for the more recent reports mandate the setup of a randomized controlled trial. The objective of the COLLISION trial is to prove non-inferiority of thermal ablation compared to hepatic resection in patients with at least one resectable and ablatable CRLM and no extrahepatic disease. Methods: In this two-arm, single-blind multi-center phase-III clinical trial, six hundred and eighteen patients with at least one CRLM (≤3cm) will be included to undergo either surgical resection or thermal ablation of appointed target lesion(s) (≤3cm). Primary endpoint is OS (overall survival, intention-to-treat analysis). Main secondary endpoints are overall disease-free survival (DFS), time to progression (TTP), time to local progression (TTLP), primary and assisted technique efficacy (PTE, ATE), procedural morbidity and mortality, length of hospital stay, assessment of pain and quality of life (QoL), cost-effectiveness ratio (ICER) and quality-adjusted life years (QALY). Discussion: If thermal ablation proves to be non-inferior in treating lesions ≤3cm, a switch in treatment-method may lead to a reduction of the post-procedural morbidity and mortality, length of hospital stay and incremental costs without compromising oncological outcome for patients with CRLM. Trial registration:NCT03088150 , January 11th 2017