Charles Lester Leonard

Leonard was born on December 29, 1861, in Easthampton, Massachusetts, to Moses and Harriet (née Dibble) Leonard. He had two siblings; his brother, Frederick M. Leonard, became a prominent Philadelphia attorney. The family could trace its ancestry back to John Leonard, who left England in 1632 to settle in Springfield, Massachusetts, and to William Brewster, who came to the U.S. on the Mayflower.^{[1]: 43 [2]} Another of their forebears, Elijah Leonard, fought in the American Revolutionary War.^[1]: 43

Leonard grew up in Philadelphia, and he attended Rittenhouse Academy. He then earned bachelor's degrees at the University of Pennsylvania (1885) and Harvard University (1886). He received a medical degree from Penn in 1889, then went to Europe to observe some laboratory techniques. During his studies, Leonard was interested in photography and served as a model for Eadweard Muybridge's photographic study of human motion called Man Running.^[3]: 8–9

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Leonard took a position as an assistant instructor of clinical surgery at Penn, where he worked under surgeon J. William White. The university awarded him a Master of Arts in 1892 while he was already a faculty member.^[1]: 43 When Penn's William Pepper Clinical Laboratory opened in 1895, Leonard began conducting his laboratory work there.^[3]: 9 He became interested in photomicrography, which is the acquisition of photographic images from microscopes. He devised an electric lens-shutter that allowed him to capture microorganisms in different phases of their life cycles.^[4]: 1541

In 1895, Wilhelm Röntgen produced the first X-rays.^[5]: 565 Early on, X-rays were used mostly for surgical applications. Leonard already had interests in surgery and photography, so he was fascinated by the potential for X-rays. A Philadelphia physicist named Arthur Willis Goodspeed set up a radiography laboratory near University Hospital, and the hospital initially sent its patients there for X-rays, but it became impractical to transport a patient to this facility each time a study was required. In September 1896, Leonard began running a hospital-wide X-ray service out of the Pepper Laboratory. White had a separate X-ray laboratory, but it was used almost solely for teaching purposes.^[3]: 9

While Leonard's X-ray apparatus in the Pepper Laboratory was on the grounds of University Hospital, it still proved impractical to transport hospitalized patients there. Leonard's X-ray equipment was relocated in late 1897 to the Agnew Memorial Pavilion, a brand new wing of the hospital, but the decision to move it there came after the new wing was fully designed. Leonard had a single X-ray exam room near the surgical dispensary, and the darkroom was so small that no visitors or students could observe Leonard as he developed the X-ray plates. Leonard imaged 141 hospital patients in 1901, and the most common studies were of the abdomen and pelvis; the exposure time for each patient could be as long as several minutes.^[3]: 12

Leonard's influence in radiology quickly extended beyond University Hospital. In 1899, he was approached by Philadelphia General Hospital and asked to help a young physician, George E. Pfahler, with setting up an X-ray service at that hospital. Leonard advised Pfahler on the types of equipment to install, including a self-regulating X-ray tube that Leonard had success with from the Philadelphia-based James W. Queen & Company. Around this time, Leonard began conducting research and writing more extensively. He became interested in using X-rays to diagnose fractures and to locate foreign bodies in the eye.^[3]: 13

During his time at Penn, Leonard also opened a private X-ray office in Philadelphia's Center City, and he became the director of the X-ray laboratories at Philadelphia Polyclinic and Methodist Episcopal Hospital.^[3]: 14 Leonard was the first American physician to identify kidney stones on an X-ray. While he continued to do general X-ray work, he gained a wide reputation for his ability to diagnose kidney stones.^[4]: 1542

Leonard used an X-ray system consisting of accumulators and a Ruhmkorff coil with a low-voltage primary winding that excited a self-regulating X-ray tube. In 1936, radiologist Percy Brown wrote that Leonard's intricate setup "was a source of great interest and some surprise to his contemporaries, but will amaze radiologists of a later generation who now read of them for the first time."^[4]: 1542 Leonard examined more than 300 patients for kidney stones with this technique, and he said he had an error rate of three percent. He knew of 45 patients who had been taken to surgery despite no X-ray evidence of kidney stones, and he said that surgeons did not find kidney stones in any of those patients.^[4]: 1542 Leonard influenced the surgical management of ureteral stones by showing that the patient was usually able to pass small stones in this area by themselves.^[6]

Leonard was one of the first physicians to work with stereo-roentgenography, which used stereoscopy to produce three-dimensional X-ray images that allowed physicians to better determine the anatomic relationships between organs. Leonard used the technique to visualize a patient's small intestine.^[7] He may have been the first American radiologist to define a dosage unit for radiation, though it was not possible to measure dosage at that point. Commenting on the possibility of employing radiation therapy, he said that physicians needed to be able to deliver a controlled dose, and the unit should be defined as "the unit quantity of electricity passing across a unit gap in unit time under the influences of radiation at unit distance under standard conditions of barometer and temperature."^[4]: 1543

Leonard left Penn in 1902. Two things likely contributed to this decision: a busy schedule of other professional responsibilities and the onset of disabling tissue injuries from radiation exposure.^[3]: 15 He was heavily involved in the American Roentgen Ray Society, serving as its president for 1904–1905. He hosted a number of physicians at his office in 1905 to discuss their interest in radiology. This group became the Philadelphia Roentgen Ray Society, and Leonard was the organization's secretary until he died. He served as the American Medical Association (AMA) delegate to several international conferences on radiology, and he was an editor or associate editor for several medical journals.^[1]: 44

Leonard married Ruth Hodgson, and they had a daughter named Catherine Henrietta Lawson Leonard. Catherine married James Bennett Hance, a member of the Indian Medical Service, in Oxford in 1916. In his leisure time, Leonard enjoyed visiting the woods in Canada.^[6]