English: Diathermy treatment of elbow, 1945. Diathermy is the application of high frequency electric current to create deep heating in body tissues. An electronic oscillator(rear) produces a radio frequency current that passes through the wire wrapped around the patient's elbow. The current produces an oscillating magnetic field by electromagnetic induction that heats the tissue. "Long wave" diathermy using frequencies of 0.5-2 MHz was replaced by "short wave" diathermy at frequencies of 10-100 MHz around the 1930s.
This 1945 book would have the copyright renewed in 1973. Online page scans of the Catalog of Copyright Entries, published by the US Copyright Office can be found here. Search of the Renewals for 1972, 1973, and 1974 show no renewal entries for Electrotherapy and Light Therapy. Therefore the copyright was not renewed and it is in the public domain.
Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (70 years p.m.a.), Mainland China (50 years p.m.a., not Hong Kong or Macao), Germany (70 years p.m.a.), Mexico (100 years p.m.a.), Switzerland (70 years p.m.a.), and other countries with individual treaties.