Detection of pulmonary embolism on computed tomography: improvement using a model-based iterative reconstruction algorithm compared with filtered back projection and iterative reconstruction algorithms.

PURPOSE: The purpose of the study was to determine whether a model-based iterative reconstruction (MBIR) technique improves diagnostic confidence and detection of pulmonary embolism (PE) compared with hybrid iterative reconstruction (HIR) and filtered back projection (FBP) reconstructions in patients undergoing computed tomography pulmonary angiography. MATERIALS AND METHODS: The study was approved by our institutional review board. Fifty patients underwent computed tomography pulmonary angiography at 100 kV using standard departmental protocols. Twenty-two of 50 patients had studies positive for PE. All 50 studies were reconstructed using FBP, HIR, and MBIR. After image randomization, 5 thoracic radiologists and 2 thoracic radiology fellows graded each study on a scale of 1 (very poor) to 5 (ideal) in 4 subjective categories: diagnostic confidence, noise, pulmonary artery enhancement, and plastic appearance. Readers assessed each study for the presence of PE. Parametric and nonparametric data were analyzed with repeated measures and Friedman analysis of variance, respectively. RESULTS: For the 154 positive studies (7 readers × 22 positive studies), pooled sensitivity for detection of PE was 76% (117/154), 78.6% (121/154), and 82.5% (127/154) using FBP, HIR, and MBIR, respectively. PE detection was significantly higher using MBIR compared with FBP (P = 0.016) and HIR (P = 0.046). Because of nonsignificant increase in FP studies using HIR and MBIR, accuracy with MBIR (88.6%), HIR (87.1%), and FBP (87.7%) was similar. Compared with FBP, MBIR led to a significant subjective increase in diagnostic confidence, noise, and enhancement in 6/7, 6/7, and 7/7 readers, respectively. Compared with HIR, MBIR led to significant subjective increase in diagnostic confidence, noise, and enhancement in 5/7, 5/7, and 7/7 readers, respectively. MBIR led to a subjective increase in plastic appearance in all 7 readers compared with both FBP and HIR. CONCLUSIONS: MBIR led to significant increase in PE detection compared with FBP and HIR. MBIR led to qualitative improvements in diagnostic confidence, perceived noise, and perceived enhancement compared with FBP and HIR.

Improved accuracy of pulmonary embolism computer-aided detection using iterative reconstruction compared with filtered back projection.

OBJECTIVE: The purpose of this study was to determine whether use of iterative reconstruction (IR) can improve performance of a pulmonary embolism computer-aided detection (PE CAD) prototype. MATERIALS AND METHODS: Images were collected from 40 consecutive pulmonary CT angiographic examinations in which PE was found and 26 studies in which it was not found for use as control cases. All images were reconstructed with filtered back projection (FBP) and six levels of a hybrid IR algorithm. The studies were evaluated with a prototype PE CAD system, and its performance was comparatively assessed on the basis of reconstruction type on a per-embolus and a per-study basis. RESULTS: Use of the hybrid IR algorithm led to a significant and progressive decrease in false-positive marks made by PE CAD compared with those made by radiologists on FBP reconstructions (239 false-positive marks for FBP and 154, 136, 125, 116, 107, and 98 false-positive marks for the six hybrid IR [HIR] levels). Specificity improved with increasing HIR level (45.6% for level 6; 30.3% for FBP). However, compared with FBP, increasing levels of HIR resulted in a progressive decrease in per-embolism sensitivity (70.3% for FBP; 55.4% for HIR level 6) and, with the exception of HIR level 4, a progressive decrease in per-study sensitivity (97.5% for FBP; 85.0% for HIR level 6). Overall accuracy was highest for HIR level 1 (77.3%). CONCLUSION: The use of IR leads to a significant reduction in false-positive marks by PE CAD at a cost of decreasing sensitivity. Very high levels of IR, which had the lowest sensitivities, should be avoided if being used concomitantly with PE CAD.

Patient anatomy predicts operative time in robotic totally endoscopic coronary artery bypass surgery.

OBJECTIVES: The influence of patient thoracic anatomy on operative times in robotic total endoscopic coronary artery bypass (TECAB) has not been well described. The aim of this study was to determine whether patient anatomy correlates with intraoperative time required to complete various procedural steps and overall operative time in TECAB. METHODS: Preoperative multislice computed tomographic scans of the chest from 107 consecutive patients who underwent single-vessel TECAB were reviewed to measure a series of thoracic dimensions and relations. Measurements were correlated with time to complete various intraoperative procedural tasks as well as overall operative time. RESULTS: There was a significant correlation between left internal mammary artery (LIMA) harvest time and depth of subcutaneous tissue at the level of the nipple (r = 0.24, P = 0.018). Pericardial fat pad thickness was associated with longer resection times (r = 0.266, P = 0.008). LIMA to left anterior descending artery anastomotic time was inversely correlated with the distance from the left heart border to the chest wall (r = -0.241, P = 0.016). Total operative time was also inversely correlated with this distance (r = -0.275, P = 0.005). CONCLUSIONS: Anatomical measurements made on preoperative computed tomography in patients undergoing robotic TECAB can predict time requirements for various procedural steps. A shorter distance between the chest wall and the heart predicts longer anastomotic and total operative times. This information could assist the TECAB surgeon with surgical planning and help guide the TECAB trainee in patient selection.

Missed pulmonary emboli on CT angiography: assessment with pulmonary embolism-computer-aided detection.

OBJECTIVE: The purpose of this study is to assess the use of a pulmonary embolism (PE)- computer-aided detection (CADx) program in the detection of PE missed in clinical practice. MATERIALS AND METHODS: Pulmonary CT angiography (CTA) studies (n = 6769) performed between January 2009 and July 2012 were retrospectively assessed by a thoracic radiologist. In studies that were positive for PE, all prior contrast-enhanced pulmonary CTA studies were reviewed. Missed PE was deemed to have occurred if PE was not described in the final interpretation. The presence, proximal extent, and number of PEs were agreed on by three thoracic radiologists. Studies with missed acute PE and available slice thickness of 2 mm or less were assessed with a prototype PE-CADx program. False-positive PE-CADx marks were analyzed. Outcomes of missed acute PEs were assessed in patients with both follow-up imaging and clinical data. RESULTS: Fifty-three studies with overlooked acute PE met our inclusion criteria for PE-CADx assessment. The PE-CADx program identified at least one PE in 77.4% of instances (41/53). PE-CADx correctly marked at least one PE in 23 of 23 cases (100%) with multiple PEs and 18 of 30 (60%) cases with a solitary PE (p < 0.001). PE-CADx per-study sensitivity was significantly higher for segmental (65.5%) than for subsegmental (91.7%) PEs (p = 0.002). PE-CADx averaged 3.8 false-positive marks per case (range, 0-23 marks). Fourteen patients with missed PE who were not receiving anticoagulation therapy developed new PEs, including nine with an isolated subsegmental PE on the initial CT scan. CONCLUSION: PE-CADx correctly identified 77.4% of cases of acute PE that were previously missed in clinical practice.

Cyclic strain stimulates proliferative capacity, alpha2 and alpha5 integrin, gene marker expression by human articular chondrocytes propagated on flexible silicone membranes.

Chondrocytes comprise less than 10% of cartilage tissue but are responsible for sensing and responding to mechanical stimuli imposed on the joint. However, the effect of mechanical signals at the cellular level is not yet fully defined. The purpose of this study was to test the hypothesis that mechanical stimulation in the form of cyclic strain modulates proliferative capacity and integrin expression of chondrocytes from osteoarthritic knee joints. Chondrocytes isolated from articular cartilage during total knee arthroplasty were propagated on flexible silicone membranes. The cells were subjected to cyclic strain for 24 h using a computer-controlled vacuum device, with replicate samples maintained under static conditions. Our results demonstrated increase in proliferative capacity of the cells subjected to cyclic strain compared with cells maintained under static conditions. The flexed cells also exhibited upregulation of the chondrocytic gene markers type II collagen and aggrecan. In addition, cyclic strain resulted in increased expression of the alpha2 and alpha5 integrin subunits, as well as an increased expression of vimentin. There was also intracellular reconfiguration of the enzyme protein kinase C. Our findings suggest that these molecules may play a role in the signal transduction pathway, eliciting cellular response to mechanical stimulation.