The fish (IMRT) needs a bicycle (MLC)? The bicycle factories seem flourishing; not so the goldfish-bowl factories

In this brief Letter the arguments of Sherouse in 2002, that the delivery of intensity-modulated radiation therapy (IMRT) does not necessarily require a multileaf collimator (MLC), are extended with specific reference to the possibility to use the jaws-only (JO) of an accelerator or some moving mask. With reference to the work in the last decade to develop JO IMRT the argument is made that it is not just the limitations of JO that are precluding its commercial development but also the commercial/business and reimbursement situations. A new moving-mask-IMRT technique that has high monitor-unit (MU) efficiency, but low MU per component, is illustrated. The Letter is intended to stimulate debate and is not a criticism by the author of current MLC-based IMRT.