Coronary arteries are the blood vessels supplying oxygen-rich blood to the heart muscles. Coronary artery calcium (CAC), which is the total amount of calcium deposited in these arteries, indicates the presence or the future risk of coronary artery diseases. Quantification of CAC is done by using computed tomography (CT) scan which uses attenuation of x-ray by different tissues in the body to generate three-dimensional images. Calcium can be easily spotted in the CT images because of its higher opacity to x-ray compared to that of the surrounding tissue. However, the arteries cannot be identified easily in the CT images. Therefore, a second scan is done after injecting a patient with an x-ray opaque dye known as contrast material which makes different chambers of the heart and the coronary arteries visible in the CT scan. This procedure is known as computed tomography angiography (CTA) and is performed to assess the morphology of the arteries in order to rule out any blockage in the arteries. The CT scan done without the use of contrast material (non-contrast-enhanced CT) can be eliminated if the calcium can be quantified accurately from the CTA images. However, identification of calcium in CTA images is difficult because of the proximity of the calcium and the contrast material and their overlapping intensity range. In this dissertation first we compare the calcium quantification by using a state-of-the-art non-contrast-enhanced CT scan method to conventional methods suggesting optimal quantification parameters. Then we develop methods to accurately quantify calcium from the CTA images. The methods include novel algorithms for extracting centerline of an artery, calculating the threshold of calcium adaptively based on the intensity of contrast along the artery, calculating the amount of calcium in mixed intensity range, and segmenting the artery and the outer wall. The accuracy of the calcium quantification from CTA by using our methods is higher than the non-contrast-enhanced CT thus potentially eliminating the need of the non-contrast-enhanced CT scan. The implications are that the total time required for the CT scan procedure, and the patient's exposure to x-ray radiation are reduced.

Purpose: To evaluate the diagnostic performance of Coronary Computed Tomography Angiography (CCTA) in predicting Myocardial Perfusion Scintigraphy (MPS) perfusion defects in low likelihood patients with End Stage Renal Disease (ESRD) awaiting transplant. Materials and Methods: In total, 131 consecutive patients with ESRD awaiting transplant were prospectively enrolled in this study (86 men; 54±9years). All patients underwent MPS as per standard of care and in addition non-enhanced CT for calcium scoring (CAC score) and Coronary Computed Tomography Angiography (CCTA). Results: The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of CAC score in predicting MPS perfusion defects were 88%, 35%, 28% and 92%, respectively. The sensitivity, specificity, PPV and NPV of CCTA in predicting MPS perfusion defects at the patient level were 55%, 87%, 57% and 87%, respectively, and 48%, 92%, 41% and 94% at the vessel level. The diagnostic performance of CCTA in predicting MPS perfusion defects improved when patients with CAC score higher than 1000 (15/70, 21%) were excluded from the analysis. In patients with positive CAC score up to 1000 sensitivity, specificity, PPV and NPV at the patient level were 60%, 93%, 75% and 86% respectively. These were 53%, 91%, 36% and 95%, respectively, at the vessel level. Conclusion: Non-enhanced CT for CAC score and CCTA can be considered useful diagnostic tools in the ESRD population, particularly in identifying patients without coronary artery disease. This approach however had limitations in the presence of high CAC score.

Coronary artery disease (CAD) is associated with significant morbidity and mortality. Coronary artery calcification (CAC) indicates presence of CAD. Absence of CAC is associated with very low risk of having CAD but not equal to zero. In this study, we aim at developing a clinical prediction tool to predict presence of obstructive CAD among patients with zero calcium score. We developed two models. A full prespecified model with 7 variables based on input from clinical experts, and a reduced model with 4 variables based on univariate screening. Both models showed an acceptable performance (c-statistics of 0.68 for both). Both models performed well when validated, externally for the full model and internally for the reduced one. We derived a clinical risk score of 20 points from the full model. We found that a score threshold of ≥ 14 is associated with presence of obstructive CAD with positive likelihood ratio of 5.5.

Background: Cerebrovascular injury (CVI) is a potentially devastating complication of gunshot wounds to the head (GSWH), with yet unclear incidence and prognostic implications. Few studies have also attempted to define CVI risk factors and their role in patient outcomes. We aimed to describe 10 years of CVI from GSWH and characterize these injury patterns. Methods: Single-institution data from 2009 to 2019 were queried to identify patients presenting with dural-penetrating GSWH. Patient records were reviewed for GSWH characteristics, CVI patterns, management, and follow-up. Results: Overall, 63 of 297 patients with GSWH underwent computed tomography angiography (CTA) with 44.4% showing CVI. The middle cerebral artery (22.2%), dural venous sinuses (15.9%), and internal carotid artery (14.3%) were most frequently injured. Arterial occlusion was the most prominent injury type (22.2%) followed by sinus thrombosis (15.9%). One fifth of patients underwent delayed repeat CTA, with 20.1% showing new/previously unrecognized CVI. Bihemispheric bullet tracts were associated with CVI occurrence (P = 0.001) and mortality (P = 0.034). Dissection injuries (P = 0.013), injuries to the vertebrobasilar system (P = 0.036), or the presence of ≥2 concurrent CVIs (P = 0.024) were associated with increased risk of mortality. Of patients with CVI on initial CTA, 30% died within the first 24 hours. Conclusions: CVI was found in 44.4% of patients who underwent CTA. Dissection and vertebrobasilar injuries are associated with the highest mortality. CTA should be considered in any potentially survivable GSWH. Longitudinal study with consistent CTA use is necessary to determine the true prevalence of CVI and optimize the use of imaging modalities.

Background: Cerebrovascular injury (CVI) is a potentially devastating complication of gunshot wounds to the head (GSWH), with yet unclear incidence and prognostic implications. Few studies have also attempted to define CVI risk factors and their role in patient outcomes. We aimed to describe 10 years of CVI from GSWH and characterize these injury patterns. Methods: Single-institution data from 2009 to 2019 were queried to identify patients presenting with dural-penetrating GSWH. Patient records were reviewed for GSWH characteristics, CVI patterns, management, and follow-up. Results: Overall, 63 of 297 patients with GSWH underwent computed tomography angiography (CTA) with 44.4% showing CVI. The middle cerebral artery (22.2%), dural venous sinuses (15.9%), and internal carotid artery (14.3%) were most frequently injured. Arterial occlusion was the most prominent injury type (22.2%) followed by sinus thrombosis (15.9%). One fifth of patients underwent delayed repeat CTA, with 20.1% showing new/previously unrecognized CVI. Bihemispheric bullet tracts were associated with CVI occurrence (P = 0.001) and mortality (P = 0.034). Dissection injuries (P = 0.013), injuries to the vertebrobasilar system (P = 0.036), or the presence of ≥2 concurrent CVIs (P = 0.024) were associated with increased risk of mortality. Of patients with CVI on initial CTA, 30% died within the first 24 hours. Conclusions: CVI was found in 44.4% of patients who underwent CTA. Dissection and vertebrobasilar injuries are associated with the highest mortality. CTA should be considered in any potentially survivable GSWH. Longitudinal study with consistent CTA use is necessary to determine the true prevalence of CVI and optimize the use of imaging modalities.

abstract: Coronary computed tomography angiography (CTA) has a high negative predictive value for ruling out coronary artery disease with non-invasive evaluation of the coronary arteries. My work has attempted to provide metrics that could increase the positive predictive value of coronary CTA through the use of dual energy CTA imaging. After developing an algorithm for obtaining calcium scores from a CTA exam, a dual energy CTA exam was performed on patients at dose levels equivalent to levels for single energy CTA with a calcium scoring exam. Calcium Agatston scores obtained from the dual energy CTA exam were within ±11% of scores obtained with conventional calcium scoring exams. In the presence of highly attenuating coronary calcium plaques, the virtual non-calcium images obtained with dual energy CTA were able to successfully measure percent coronary stenosis within 5% of known stenosis values, which is not possible with single energy CTA images due to the presence of the calcium blooming artifact. After fabricating an anthropomorphic beating heart phantom with coronary plaques, characterization of soft plaque vulnerability to rupture or erosion was demonstrated with measurements of the distance from soft plaque to aortic ostium, percent stenosis, and percent lipid volume in soft plaque. A classification model was developed, with training data from the beating heart phantom and plaques, which utilized support vector machines to classify coronary soft plaque pixels as lipid or fibrous. Lipid versus fibrous classification with single energy CTA images exhibited a 17% error while dual energy CTA images in the classification model developed here only exhibited a 4% error. Combining the calcium blooming correction and the percent lipid volume methods developed in this work will provide physicians with metrics for increasing the positive predictive value of coronary CTA as well as expanding the use of coronary CTA to patients with highly attenuating calcium plaques. / Dissertation/Thesis / Ph.D. Bioengineering 2013

Ischemic heart disease is currently the leading cause of death globally. Coronary artery bypass grafting (CABG) is considered the best treatment for many patients and its success depends on the long-term patency of the conduits. Greater use of arterial grafts has been advocated because of their higher long-term patency compared to saphenous vein grafts (SVGs). Despite this, SVGs account for up to 80% of all grafts used in CABG. Consequently, the long-term patency of the saphenous vein (SV) is one of the most crucial challenges in cardiovascular surgery. The no-touch (NT) SV in CABG has shown a superior patency rate, slower progression of atherosclerosis, and better clinical outcome compared to conventional veins up to 8.5 years postoperatively. The aim of this thesis was to study the long-term angiographic, echocardiographic, and clinical aspects of CABG patients receiving either NT or conventional vein grafts and to investigate the health-related quality of life (HRQoL) in this patient group. Studies I-II report a randomized trial between NT and conventional veins where 74 patients were followed-up at a mean of 16 years postoperatively. Study III is a prospective cohort trial in which 97 patients with NT vein grafts anastomosed to the left anterior descending artery (LAD) were included and followed-up at a mean of 6 years postoperatively. Study IV included 257 patients in whom HRQoL and graft patency were studied during the same follow-up visit. Overall, NT vein grafts showed a higher patency compared to conventional veins at a mean of 16 years, 83% vs. 64% (p=0.03), which was similar to the patency of the left internal thoracic artery, 88%. The NT group had a better left ventricular ejection fraction compared to the conventional group, 57.9% vs. 49.4% (p=0.011). After a mean of 6 years, the patency rate of NT SVs to the LAD was 95.6% and to non-LAD targets, 93.9%. Graft patency was an independent predictor of HRQoL in CABG patients. These patients reported a function and wellbeing similar to that of the Swedish population and clearly higher health status than those in the same disease group in the general population.

Aims: Noninvasive fractional flow reserve (FFR) measurement with computed tomography (FFRCT) is a newly described method for assessing functional significance of coronary disease. The objective of this metaanalysis is to determine the diagnostic performance of FFRCTin the assessment of hemodynamically significant coronary artery stenosis. Methods: PubMed and the Cochrane Center Register of Controlled Trials were searched from January 2000 through February 2015. Six original studies were found comparing FFRCTto invasive FFR in evaluating hemodynamic significance of coronary lesions (1354 vessels; 812 patients). Lesions were considered hemodynamically significant if invasive FFR was 0.80 or less. FFRCTused the same cutoff as invasive FFR to be considered as a positive test. Sensitivity, specificity, positive and negative likelihood ratios, and diagnostic odds ratio were calculated. Results: One-third of the lesions (n=443) were hemodynamically significant. The pooled per-vessel analysis showed that the sensitivity, specificity, negative and positive likelihood ratios, and diagnostic odds ratio of FFRCTto diagnose hemodynamically significant coronary disease were 0.84 [95% confidence interval (CI):0.80-0.87], 0.76 (95% CI: 0.73-0.79), 0.22 (95% CI: 0.17-0.29), 3.48 (95% CI: 2.21-5.47), and 16.82 (95% CI: 8.20-34.49), respectively. Conclusion: The results of this meta-analysis demonstrate that FFRCTresults correlate closely with invasive coronary angiography and FFR measurement. It is a feasible noninvasive method to assess hemodynamic significance of coronary lesions in patients with stable coronary artery disease.

The objective of this study is to determine the diagnostic performance of computed tomography perfusion (CTP) with and without computed tomography angiography (CTA) in assessment of hemodynamically significant coronary artery lesions in comparison to invasive fractional flow reserve (FFR). Materials and Methods PubMed and Cochrane Center Register of Controlled Trials from January 2010 searched through December 2014. Nine original studies were selected evaluating the diagnostic performance of CTP with and without CTA to invasive coronary angiography in evaluation of hemodynamic significance of coronary lesions (n = 951). Results The sensitivity, specificity, LR+ and LR- and DOR of CTA+CTP were 0.85 [95% confidence interval (CI: 0.79-0.89)] 0.94 (CI: 0.91-0.97), 15.8 (CI: 7.99-31.39), 0.146 (CI: 0.08-0.26), and 147.2 (CI: 69.77-310.66). Summary Receiver Operating Characteristics (SROC) results showed area under the curve (AUC) of 0.97 indicating that CTA+CTP may detect hemodynamically significant coronary artery lesions with high accuracy. The sensitivity, specificity, LR+ and LR- and DOR of CTP were 0.83 (CI: 0.78-0.87), 0.84 (CI: 0.80-0.87) 5.26 (CI: 2.93-9.43), 0.209 (CI: 0.12-0.36), and 31.97 (CI: 11.59-88.20). Conclusions This result suggests that CTP with CTA significantly improves diagnostic performance of coronary artery lesions compared to CTA alone and closely comparable with invasive FFR.

Kepenų arterijų anatominiai variantai yra dažni. Viena dažniausių aberantinių (netipiškai atsišakojančių) kepenų arterijų atsišakojimo vietų yra viršutinė pasaito arterija. Pastarosios arterijos kraujotaka yra įtakojama daugybės fiziologinių ir patologinių veiksnių. Literatūroje taip pat aprašyti pavieniai atvejai apie iš viršutinės pasaito arterijos atsišakojančios aberantinės kepenų arterijos įtaką viršutinės pasaito arterijos hemodinamikai, tačiau didesnės apimties įrodymais pagrįstų tyrimų šioje srityje iki šiol nebuvo atlikta. Todėl šio tyrimo tikslas buvo įvertinti, ar aberantinė kepenų arterija, atsišakojanti iš viršutinės pasaito arterijos, reikšmingai įtakoja pastarosios kraujagyslės hemodinamiką. Šiame tyrime kompiuterinės tomografijos angiografijos pagalba įvertinti kepenų arterijų anatominiai variantai, atrinkti pacientai doplerio ultragarso tyrimams. Pastaruoju metodu tirta viršutinės pasaito arterijos kraujotaka pacientams, kurių vieni turėjo aberantinę kepenų arteriją, atsišakojančią iš viršutinės pasaito arterijos, o kiti turėjo įprastą kepenų arterijų anatomiją. Vertinta aberantinės kepenų arterijos, atsišakojančios iš viršutinės pasaito arterijos, įtaka pastarosios arterijos hemodinamikai (rezistentiškumui). Remiantis tyrimo duomenimis nustatyta, kad kepenų arterijų anatominiai variantai yra dažni. Aberantinė kepenų arterija, atsišakojanti iš viršutinės pasaito arterijos, reikšmingai mažina pastarosios arterijos rezistentiškumą. Pateiktos praktinės... [toliau žr. visą tekstą] / Anatomical variants of hepatic arteries are frequent. One of the most common origins of aberrant (atypically branching) hepatic arteries is superior mesenteric artery. Many physiologic and pathologic features influence hemodynamics of the latter artery. There were some sporadic cases in literature about the influence of aberrant hepatic artery arising from superior mesenteric artery to the hemodynamics of the latter artery, but no evidence based large extent studies were performed. Therefore the aim of this study was to evaluate how significant the aberrant hepatic artery branching from the superior mesenteric artery influences the hemodynamics of superior mesenteric artery. Anatomical variants of the hepatic arteries were evaluated by computed tomography angiography also the candidates for Doppler ultrasound were selected. Doppler ultrasound was used to evaluate the hemodynamics of the superior mesenteric artery in patients with aberrant hepatic artery arising from the superior mesenteric artery and in those with typical hepatic artery anatomy. The influence of the aberrant hepatic artery arising from superior mesenteric artery to the hemodynamics (resistance) of the superior mesenteric artery was assessed. The results of the investigation show that anatomical variants of the hepatic arteries are frequent. The aberrant hepatic artery arising from superior mesenteric artery significantly lowers resistance of the superior mesenteric artery. Practical recommendations were set... [to full text]