Despite the dosimetric and possibly biological advantages of ion therapy with its more confirmed dose distributions and higher ionization density, the lack of appropriate image guidance remains a major obstacle to overcome. Finding new ways of imaging the patient for treatment planning to provide accurate range prediction and before treatment to detect any changes from the time of planning remains a number one goal in furthering ion therapy. Existing imaging solutions are mostly photon-based and have major drawbacks. In this one-hour talk I will describe how, as a radiation oncologist working in the hospital-based proton treatment center I became aware of this burning lack of image guidance more than 20 years ago and then set out as a physicist to find the right partners in high-energy physics to solve it with proton CT (pCT). Meanwhile there are other existing developments in image guidance that could be married with pCT to finally create the technology that will take ion therapy out of the shadow of photon therapy's advantage.

Argonne Physics Division Colloquium Schedule