Peripheral Blood Flow Responses to Electromagnetic Energy

Inclusion Criteria: * Participants will be healthy subjects over the age of 18. * Men and women will be recruited for participation. * All ethnicities will be included in this study. Exclusion Criteria: Exclusionary criteria include: * age under 18 years and those over 60 years of age, * those who are unable to understand the consent process, * those who cannot read or speak English, * a history of cancer, * peripheral artery disease, * diabetes mellitus, * active pregnancy, * hypersensitivity to perflutren contrast agents, * pulmonary hypertension, * chronic kidney disease, * active tobacco or drug use, * blood pressure over 160/90, BMI\>30, * sickle cell disease, or * history of intracardiac shunt. Additional exclusion criteria include: * a history of coronary artery disease, * heart failure, * the presence of an implanted defibrillator or pacemaker, * a history of heart murmur or rhythm disorder (atrial fibrillation, atrial tachycardia, or ventricular tachycardia), * neurological diseases such as stroke, and * any uncontrolled medical conditions.