Unlike women, men only have two choices right now when it comes to birth control—condoms or a vasectomy. Three, if you count abstinence. But after resurrecting research from the 1970s, researchers may have found another non-invasive—and reversible—option. By using ultrasound treatments—the kind used in physical therapy—on rats, researchers were able to stop the production of sperm in the testes. This “significantly reduced” the sperm count of the rats, rendering them infertile. The best results occurred when two 15-minute ultrasound treatments—two days apart—were applied through warm salt water. Researchers tested the treatment only on rats, but the earlier study did include men scheduled for removal of their testicles. They reported that the “procedure was pain-free, only creating a gentle feeling of warmth.” In the earlier study, infertility was also temporary, something researchers did not test in the current study. Other studies have shown the treatment to be effective and safe on other animals, such as monkeys and dogs. This method, however, is not yet ready for prime time. Lead researcher Dr James Tsuruta told the BBC: "Further studies are required to determine how long the contraceptive effect lasts and if it is safe to use multiple times." Researchers will also need to determine if there are unexpected or long-term effects of the treatments. While this method is not effective at protecting you from sexually-transmitted diseases, it could provide a viable birth control alternative for men, and their dogs.