Effects of Non Contact Low Frequency Ultrasound in Healing Venous Leg Ulcers

Inclusion Criteria: * Lower extremity full thickness venous ulcer of \> 30 days duration * Subject's wound must be between 4 cm² and 50 cm² at screening * Documented ABI that is between 0.8 and 1.2 on the study limb or transcutaneous partial pressure oxygen (TcpO2) \> 40 mmHG; or a toe pressure \> 40 mmHG; or a Doppler waveform consistent with adequate flow in the foot (biphasic or triphasic waveforms) at time of screening * Biopsy for wounds \> 6 months duration * Documented index wound etiology of venous stasis with reflux and /or incompetent valves Exclusion Criteria: * Index ulcer wound that is less than 1 cm in distance from another ulcer wound * \> 5 ulcers on the index leg * Index ulcer wound has exposed tendons, ligaments, muscle, or bone * Index ulcer wound presents with clinical signs of acute infection, suspected or known * Subjects with evidence of osteomyelitis or cellulitis or gangrene in the study limb * Subjects with amputation above a Trans Metatarsal Amputation (TMA) in the study limb * Subjects with active malignancy on the study limb except non-melanoma skin cancer * Index ulcer that is of arterial disease etiology * Index ulcer of other primary etiology (ie. vasculitis, arterial, pyoderma) * Subjects with planned vascular surgery, angioplasty or thrombolysis procedures within the study treatment phase * Subjects with planned surgical procedure during the study treatment phase for the index wound including skin flap or skin graft * Subjects within 6 weeks postoperatively of a vascular o skin graft procedure. * Subject has had prior skin replacement, negative pressure therapy, or traditional ultrasound therapy applied to the index wound in the 14 days prior to screening * Subject has had ultrasound treatment (including MIST Therapy) of the index wound. * Subject has received growth factor therapy (e.g., autologous platelet-rich plasma gel, becaplermin, bilayered cell therapy, dermal substitute, extracellular matrix) within 14 days of screening date. * Subject is currently receiving or has received radiation or chemotherapy within 3 months of randomization. * Female subjects that are pregnant or refuse to utilize adequate contraceptive methods and are of childbearing age during the trial. * Subject has one or more medical condition(s), uncontrolled diabetes (i.e. HbA1c \> 12), renal, hepatic, hematologic, neurologic, or immune disease that in the opinion of the investigator would make the subject an inappropriate study candidate * Subject's wound would require ultrasound near an electronic implant or prosthesis * Subject is known to be suffering from a disorder or other situation that the subject or investigator feels would interfere with compliance or other study requirements * Subject is currently enrolled or has been enrolled in the last 30 days in another investigational device or drug trial