Low-intensity Shockwave Therapy (LiST) for the Treatment of Mild and Mild-to-moderate Vasculogenic Erectile Dysfunction

Inclusion Criteria: 1. Consent to participate. 2. Age 40-70 years. 3. Sexually active in a stable, heterosexual relationship of more than three months duration. 4. Presence of Erectile Dysfunction for at least 6 months. 5. At Screening, diagnosed as Vasculogenic erectile dysfunction based on sexual history 6. PDE5i users and report some or good response to PDE5i. Last reported PDE5i use must be within 30 days of Screening Visit. 7. Agree to suspend all other ED therapies, except the assigned study treatments, for the duration of the study. 8. Agree to attempt sexual intercourse at least 4 times during the last 4 weeks prior to Visit 2/Randomization, 1-month Follow Up, 3-month Follow-Up and 6-month Follow-Up without being under the influence of alcohol or recreational drugs. Agree to document the outcome using the Sexual Encounter Profile (SEP) diary. 9. IIEF-EF score 17-25 at Visit 2 (after PDE5i washout) 10. At Visit 2 (after PDE5i washout), SEP Q2, "Were you able to insert your penis into your partner's vagina?" answered "YES" 50% - 100% of the time. 11. At Visit 2, SEP Q3, "Did your erection last long enough for you to have successful intercourse?" answered "YES" \< 100% of the time. Exclusion Criteria: 1. Previous major pelvic surgery or pelvic trauma that could impact erectile function, such as radical prostatectomy, radical cystectomy, rectal surgery. Patients with previous TURP surgery without sequelae of iatrogenic ED, may be included. 2. Previous penile surgery of any kind except circumcision and condyloma removal, such as penile lengthening, penile cancer surgery, penile plication, grafting. 3. Previous history of priapism or penile fracture 4. Previous radiation therapy to pelvis. 5. Abnormal serum testosterone level defined as a value lower than 300 ng/dL (indicative of untreated hypogonadism), or greater than 1197 ng/dL. 6. Current or previous hormone usage, other than prescribed testosterone, clomiphene or thyroid medication. Subjects with prior or current use of hormonal treatment for prostate cancer are also excluded. 7. ED due primarily to psychogenic factors. 8. Peyronie's Disease or penile curvature that negatively influences sexual activity. 9. Patients with cardiac or non-cardiac electrical devices implanted. 10. Open wounds, or any anatomical or neurological abnormalities in the treatment area. 11. Uncontrolled diabetes mellitus with glucose \>200 mg/dL (once or more times/week during the last month prior to recruitment, or during screening blood test). 12. Patients with generalized polyneuropathy, or neurological conditions irrespective of cause, such as severe diabetes, multiple sclerosis or Parkinson's Disease. 13. Refusal to suspend alternative ED therapy for duration of study. Subjects who are using Tadalafil as a treatment for BPH (Benign Prostatic Hyperplasia) will also be excluded. 14. Men deemed not healthy enough to participate in sexual activity. 15. Any condition or behavior that indicates to the Principal Investigator that the subject is unlikely to be compliant with study procedures and visits. 16. Any health history or laboratory result that indicates to the Principal Investigator that the subject has a significant medical condition and should not participate in the study. 17. Known allergy to ultrasound gel. 18. History of consistent treatment failure with PDE5 inhibitors for therapy of ED. 19. Any history of significant psychiatric disease, such as bipolar disorder or psychosis, greater than one lifetime episode of major depression, current depression of moderate or greater severity. Patients who are currently using SSRI or psychotropic medications e.g., Citalopram (Celexa), Escitalopram (Lexapro, Cipralex), Paroxetine (Paxil, Seroxat), Fluoxetine (Prozac), Fluvoxamine (Luvox, Faverin),Sertraline (Zoloft, Lustral), Clonazepam (Klonopin), Alprazolam (Xanax), Aripiprazole (Ambilify), Clozapine (Clozaril), Risperidone (Risperdal), Quetiapine (Seroquel), Olanzapine (Zyprexa) are also excluded. 20. Partners who are \< 18 years of age, who are nursing, who are known to be pregnant at screening, who wish to become pregnant during the study period, who have any gynecologic problems, sexual dysfunction, or major medical conditions that would limit participation in sexual intercourse. 21. History of adverse events in response to tadalafil, which would prevent the patient from being blinded to his group allocation, and/or prevent patient compliance to the study protocol.