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    Robert Gilkeson

    Aim Human Immunodeficiency Virus (HIV) patients commonly experience dyspnea for which an immediate cause may not be always apparent. In this prospective cohort study of HIV patients with exercise limitation, we use cardiopulmonary... more
    Aim Human Immunodeficiency Virus (HIV) patients commonly experience dyspnea for which an immediate cause may not be always apparent. In this prospective cohort study of HIV patients with exercise limitation, we use cardiopulmonary exercise testing (CPET) coupled with exercise cardiovascular magnetic resonance (CMR) to elucidate etiologies of dyspnea. Methods and results Thirty-four HIV patients on antiretroviral therapy with dyspnea and exercise limitation (49.7 years, 65% male, mean absolute CD4 count 700) underwent comprehensive evaluation with combined rest and maximal exercise treadmill CMR and CPET. The overall mean oxygen consumption (VO2) peak was reduced at 23.2 ± 6.9 ml/kg/min with 20 patients (58.8% of overall cohort) achieving a respiratory exchange ratio > 1. The ventilatory efficiency (VE)/VCO2 slope was elevated at 36 ± 7.92, while ventilatory reserve (VE: maximal voluntary ventilation (MVV)) was within normal limits. The mean absolute right ventricular (RV) and lef...
    At our institution, we are using dual-energy digital radiography (DEDR) as a cost-effective screening tool for the detection of cardiac calcification. We are evaluating DEDR using CT as the gold standard. We are developing image... more
    At our institution, we are using dual-energy digital radiography (DEDR) as a cost-effective screening tool for the detection of cardiac calcification. We are evaluating DEDR using CT as the gold standard. We are developing image projection methods for the generation of digitally reconstructed radiography (DRR) from CT image volumes. Traditional visualization methods include maximum intensity projection (MIP) and average-based projection (AVG) that have difficulty to show cardiac calcification. Furthermore, MIP can over estimate the calcified lesion as it displays the maximum intensity along the projection rays regardless of tissue types. For AVG projection, the calcified tissue is usually overlapped with bone, lung and mediastinum. In order to improve the visualization of calcification on DRR images, we developed a Gaussian-weighted projection method for this particular application. We assume that the CT intensity values of calcified tissues have a Gaussian distribution. We then use...
    ABSTRACT
    ABSTRACT
    ABSTRACT
    We are investigating image processing and analysis techniques to improve the ability of dual-energy digital radiography (DR) for the detection of cardiac calcification. Computed tomography (CT) is an established tool for the diagnosis of... more
    We are investigating image processing and analysis techniques to improve the ability of dual-energy digital radiography (DR) for the detection of cardiac calcification. Computed tomography (CT) is an established tool for the diagnosis of coronary artery diseases. Dual-energy digital radiography could be a cost-effective alternative. In this study, we use three-dimensional (3D) CT images as the "gold standard" to evaluate the DR X-ray images for calcification detection. To this purpose, we developed an automatic registration method for 3D CT volumes and two-dimensional (2D) X-ray images. We call this 3D-to-2D registration. We first use a 3D CT image volume to simulate X-ray projection images and then register them with X-ray images. The registered CT projection images are then used to aid the interpretation dual-energy X-ray images for the detection of cardiac calcification. We acquired both CT and X-ray images from patients with coronary artery diseases. Experimental resul...
    We are investigating three-dimensional (3D) to two-dimensional (2D) registration methods for computed tomography (CT) and dual-energy digital radiography (DR) for the detection of coronary artery calcification. CT is an established tool... more
    We are investigating three-dimensional (3D) to two-dimensional (2D) registration methods for computed tomography (CT) and dual-energy digital radiography (DR) for the detection of coronary artery calcification. CT is an established tool for the diagnosis of coronary artery diseases (CADs). Dual-energy digital radiography could be a cost-effective alternative for screening coronary artery calcification. In order to utilize CT as the "gold standard" to evaluate the ability of DR images for the detection and localization of calcium, we developed an automatic intensity-based 3D-to-2D registration method for 3D CT volumes and 2D DR images. To generate digital rendering radiographs (DRR) from the CT volumes, we developed three projection methods, i.e. Gaussian-weighted projection, threshold-based projection, and average-based projection. We tested normalized cross correlation (NCC) and normalized mutual information (NMI) as similarity measurement. We used the Downhill Simplex me...
    A 26-year old female had an incidental finding of a cystic mediastinal mass (10.8 × 9.4 × 10.0 cm) in the inferior-anterior mediastinum. It had compressed the superior vena cava, right atrium and right ventricle, and additional imaging... more
    A 26-year old female had an incidental finding of a cystic mediastinal mass (10.8 × 9.4 × 10.0 cm) in the inferior-anterior mediastinum. It had compressed the superior vena cava, right atrium and right ventricle, and additional imaging studies could not exclude right heart involvement. She underwent exploration via right thoracoscopy (video-assisted thoracoscopy), and the right groin vessels were isolated for bypass, if needed. Examination of the mass revealed its extrapericardial origin from the thymus. Complete resection was achieved with minimally invasive techniques through a 2.5-cm incision using a three-port approach. She was discharged on postoperative day one. The interdisciplinary planning and cooperation in this case avoided thoracotomy or sternotomy and allowed for a safe and complete minimally invasive resection.
    We demonstrate a minimally-invasive thoracoscopic approach [video-assisted thoracic surgery (VATS)] for removal of a retained pericardial suture needle after standard coronary artery bypass grafting (CABG) surgery. A 46-year-old male... more
    We demonstrate a minimally-invasive thoracoscopic approach [video-assisted thoracic surgery (VATS)] for removal of a retained pericardial suture needle after standard coronary artery bypass grafting (CABG) surgery. A 46-year-old male presented with unstable angina. His workup demonstrated significant coronary artery disease for which he underwent a six vessel CABG, including entering the left chest for preparation of the left internal mammary artery (LIMA). At seven weeks, a postoperative chest X-ray demonstrated a foreign body (suture needle) present in the cardiac silhouette. Further computed tomography (CT)-scan imaging confirmed the suture needle to be localized in the left inferior-posterior pericardium. The patient underwent a left VATS exploration for removal of the suture needle. The pericardial suture needle was successfully retrieved thoracoscopically. The chest tube was removed on the first postoperative day and the patient was discharged to home on the second postoperati...
    Hilar cholangiocarcinoma is associated with a dismal prognosis; however, curative resection may offer a chance of cure. Various factors should be considered in the surgical planning for curative resection. These factors include extent of... more
    Hilar cholangiocarcinoma is associated with a dismal prognosis; however, curative resection may offer a chance of cure. Various factors should be considered in the surgical planning for curative resection. These factors include extent of bile duct involvement, relationship between portal vein and tumor involvement, diffuse hepatoduodenal ligament infiltration, vascular invasion, lymph node metastasis, peritoneal seeding, and hepatic volume. Using high-quality volume data from multidetector-row computed tomography (MDCT) and adequate postprocessing images, radiologists can provide various types of information, imperative for curative resection of a hilar cholangiocarcinoma. This review illustrates the role of MDCT in the preoperative workup of hilar cholangiocarcinoma.
    Continuous improvement in multislice computed tomography technology has further enabled advances in coronary artery bypass graft imaging. Multidetector platforms and retrospective electrocardiography gating have enabled sensitivities and... more
    Continuous improvement in multislice computed tomography technology has further enabled advances in coronary artery bypass graft imaging. Multidetector platforms and retrospective electrocardiography gating have enabled sensitivities and specificities in the 95% to 99% range while avoiding the morbidity associated with invasive catheter angiography. Identification of bypass graft stenoses and bypass graft aneurysms/pseudoaneurysms is important in evaluation of these patients. Recognition of coronary artery bypass graft anatomy is particularly important to minimize the complications associated with reoperative cardiac surgery. The 3-dimensional demonstration of chest wall anatomy and its relationships to these coronary bypass grafts makes multislice computed tomography a superior technology in this patient population. Confident evaluation and assessment of the patient after coronary artery bypass graft surgery will become an increasingly important tool to the practicing radiologist.
    We are investigating three-dimensional (3D) to two-dimensional (2D) registration methods for computed tomography (CT) and dual-energy digital radiography (DR) for the detection of coronary artery calcification. CT is an established tool... more
    We are investigating three-dimensional (3D) to two-dimensional (2D) registration methods for computed tomography (CT) and dual-energy digital radiography (DR) for the detection of coronary artery calcification. CT is an established tool for the diagnosis of coronary artery diseases (CADs). Dual-energy digital radiography could be a cost-effective alternative for screening coronary artery calcification. In order to utilize CT as the “gold standard ” to evaluate the ability of DR images for the detection and localization of calcium, we developed an automatic intensity-based 3D-to-2D registration method for 3D CT volumes and 2D DR images. To generate digital rendering radiographs (DRR) from the CT volumes, we developed three projection methods, i.e. Gaussian-weighted projection, threshold-based projection, and average-based projection. We tested normalized cross correlation (NCC) and normalized mutual information (NMI) as similarity measurement. We used the Downhill Simplex method as t...
    A 63-year-old female with a history of invasive ductal breast carcinoma presented to the emergency department with symptoms characteristic of myocardial infarction. Electrocardiography showed sinus tachycardia and ST elevations in leads... more
    A 63-year-old female with a history of invasive ductal breast carcinoma presented to the emergency department with symptoms characteristic of myocardial infarction. Electrocardiography showed sinus tachycardia and ST elevations in leads II, III, and aVF, consistent with inferior wall myocardial infarction. A computed tomography (CT) scan of the chest, abdomen, and pelvis with intravenous contrast demonstrated widespread intrathoracic metastatic disease. Cardiac magnetic resonance imaging (MRI) with contrast revealed obstruction of the left ventricular (LV) outflow tract by an LV mass. Cardiac MRI enabled detection of a rare case of myocardial infarction secondary to tumor emboli and intracavitary LV metastasis. This case report emphasizes the role of cross-sectional imaging including CT and cardiac MRI for unusual causes of myocardial infarction, particularly when associated with neoplastic processes.

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