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Seeking guidance on image guidance
16.51 Wednesday ET: If there’s one stand-out theme at the ASTRO conference and exhibition this week it’s image guidance - more specifically, image-guided radiation therapy (IGRT), also known as 4D radiotherapy.
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 this 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 guy when it comes to IGRT (which I guess is what they’d be expected to do). 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 suffering information overload on the fourth day of the show.)
For those in need of enlightenment, the panel session “Optimization, imaging for target volume specification and assessment” at the conference this afternoon 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 current Talking Point article on medicalphysicsweb (see Tumour motion: many solutions to one problem). “Advances in computer and detector technology mean that image-guided radiation therapy (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.”
• Meanwhile, back in the press room today, talk among the assembled medical press and staff turned to further seizmic shifts beyond the walls of the convention centre. Britney and Kevin, it seems, have been trumped. Today was all about the resignation of defence secretary Donald “The Teflon Don” Rumsfeld, who fell on his sword after the Republican party took what President George Bush described as a thumpin’ at the polls Tuesday.
