Put simply, IGRT is all about real-time imaging meets real-time adjustment of therapeutic radiation beams. Talking to the equipment makers at the ASTRO exhibition, it's clear there are plenty of variations on the theme out there - too many to do justice to in our show blog. Equally, it's evident that all of the techniques have one significant thing in common: each of the vendors in question is claiming a fundamentally better approach than the next one when it comes to IGRT. They can't all be right, though.

Fact is, with the marketing machinery in full swing, the task of figuring out the fact from the fiction in this emerging and fast-moving technology area becomes doubly difficult for hard-pressed radiation oncologists, hospital administrators, medical physicists and other technical staff with inputs into big-ticket capital-expenditure decisions. (For the record, it isn't any easier for technology journalists trying to make an objective call on this stuff.)

For those in need of enlightenment, the panel session "Optimization, imaging for target volume specification and assessment" at the conference did yield some useful tips on deconstructing the whole area of image guidance in radiotherapy. In the opening presentation, James Dempsey, from the department of radiation oncology at the University of Florida (Gainesville, FL), went back to basics with the three fundamental questions to be answered when imaging the patient at the planning stage and on the treatment couch:

• What to shoot - i.e. what is the target?
• What not to shoot - i.e. where does the target end?
• Did we hit what we were shooting at?

Put another way, radiation-therapy imaging is all about quantitative measurements that deliver a reliable picture of the tumour's spatial fidelity and extent. Trouble is, as Dempsey pointed out, "patients are soft and squishy - they move, breathe, shrink and grow." And herein lies the problem. "Accurate target identification remains one of the greatest areas for improvement in radiation-therapy planning," he told delegates. "Multimodality imaging [including CT, PET, PET-CT and MRI] is a valuable tool in this process and its use in radiation oncology is increasing."

Indeed the same point is made by Steve Webb, professor of radiological physics at the University of London, UK, in the latest Talking Point article on medicalphysicsweb (see Tumour motion: many solutions to one problem). "Advances in computer and detector technology mean that IGRT is now a reality," he writes. "Three-dimensional imaging apparatus for kilovoltage and megavoltage cone-beam tomography, together with the exploratory use of ultrasound, linac-linked MRI and a variety of optical techniques, form the basis of such IGRT."

Have your say
Check out our ASTRO blog for further reports on IGRT, as well as a round-up of significant advances in IMRT, molecular imaging, particle therapy and plenty more besides featured at the ASTRO meeting. While you're at it, the publishing team here at medicalphysicsweb would love to hear any feedback you might have on the blog format and how we might improve it. In other words, your input can help us to tailor our coverage of leading conferences/exhibitions like ASTRO in 2007 and beyond.

So far, reader response to our daily ASTRO coverage has ranged from the positive - "Believe me, we found it the day it was posted and it has already been circulated around the company....Thanks again for the great blog" - to the sceptical - "Jury is out here with respect to mix of informal asides (on Britney and election) with the reporting...This also dates." Certainly there are some things we've got to do better: "If medicalphysicsweb does this again, then regular subscribers have to get a daily email with a link. Otherwise your finely scripted words simply aren't going to get the readership that they could," noted one reader. Fair point...

You can let us know what you think of the blog format via the commenting tools at the end of this article. Alternatively, just drop me an email, in confidence, to joe.mcentee@iop.org.