Needle Free Assessment of Myocardial Oxygenation in Healthy Subjects

Inclusion Criteria: 1. Adults ≥ 45 years of age 2. No known cardiac disease Exclusion Criteria: 1. Low blood pressure (systolic blood pressure \< 100 mmHg) 2. Inability to voluntarily increase their breathing rate if prompted to do so 3. Persons with the inability to lie supine for 30-40 minutes 4. Persons who are pregnant, nursing, or implanted with intrauterine devices (IUD's) 5. Persons with significant neurological, pulmonary, renal or hepatic disease 6. Persons who have an abnormal cardiac rhythm or resting heart rate \>100/min 7. Inability or unwillingness to provide informed consent