John Rowland Mallard OBE FRSE FREng (14 January 1927[1] – 25 February 2021)[2] was an English physicist and professor of Medical Physics at the University of Aberdeen from 1965 until his retirement in 1992.

He was known for setting up and leading the team that developed the first magnetic resonance imaging (MRI) full body scanner and, in particular, positron emission tomography (PET).

[8] He joined Hammersmith Hospital and Post Graduate Medical School in 1953,[7] and in 1959 Mallard developed the first whole-body isotope scanner (homemade) in the UK, used for detecting a brain tumour, with C. J.

[10] In 1965 he was appointed the first chair of Medical Physics at the University of Aberdeen, predicting at his first lecture that positron emission tomography (PET) would become one of the most important tools for diagnosis and studying of diseases.

[10] Mallard brought to Scotland its first PET scanner, leading a national fundraising campaign and agreeing to bring a second-hand research machine from London.