Willi Kalender (1949–2024)

Medical physicist Willi Kalender died on October 20 at the age of 75. Kalender was an inventor of spiral computed tomography. Russ Hobbie and I describe spiral CT in Chapter 16 of Intermediate Physics for Medicine and Biology.

Figure 16.25 shows the evolution of the detector and source configurations [of CT]. The third generation configuration is the most popular. All of the electrical connections are made through slip rings. This allows continuous rotation of the gantry and scanning in a spiral as the patient moves through the machine. Interpolation in the direction of the axis of rotation (the z axis) is used to perform the reconstruction for a particular value of z. This is called spiral CT or helical CT. Kalender (2011) discusses the physical performance of CT machines, particularly the various forms of spiral machines.

Computed Tomography,
by Willi Kalender.

The citation is to Kalender’s well-known textbook Computed Tomography: Fundamentals, System Technology, Image Quality and Applications. According to Google Scholar, it has been cited over 1800 times. Russ and I reference it often.

Kalender obtained his PhD in 1979 from the University of Wisconsin’s famous medical physics program. He then went to the University of Tübingen in Germany. There, according to Wikipedia, “he took and successfully completed all courses in the pre-clinical medicine curriculum.” This is interesting, because just a few years earlier Russ Hobbie did the same thing in Minnesota.

Between 1971 and 1973 I audited all the courses medical students take in their first 2 years at the University of Minnesota. I was amazed at the amount of physics I found in these courses and how little of it is discussed in the general physics course.

Kalender was much loved in the radiology community. The European Society of Radiology wrote

With deep sadness, the ESR announces the passing of Prof. Willi Kalender on October 20, 2024 at the age of 75. A pioneering figure in diagnostic imaging and medical physics, Prof. Kalender significantly influenced the field through his groundbreaking research and leadership.

You can find a memorial page with many more tributes to Kalender here: https://www.kudoboard.com/boards/xqZwpoWO

Prof. Willi Kalender — Dedicated Breast CT — Interview at RSNA 2013

https://www.youtube.com/watch?v=9Ay-Ry6a8C0