Recently in ASTRO Annual Meeting 2006 Category

Next stop LA

Unlike Britney and soon-to-be ex-husband K-Fed (see "Medical physics: the pick of the ASTRO papers", posted November 8), all the talking, pitching and schmoozing at the 48th annual ASTRO meeting is already last week's news. For the more than 11,000 delegates and 200+ exhibiting organizations, however, the hard graft of following up on those key contacts, potential collaborators and sales leads is only just beginning. Meanwhile, your correspondent in Philadelphia is once again your correspondent in Bristol, UK, and the task this end is to close the circle on medicalphysicsweb's ASTRO event blog. With that in mind, I've dredged through my notes and associated product literature to recap some of the other significant announcements to feature at the ASTRO trade exhibition last week:

• Accuray, US, and Siemens Medical Solutions, Germany, signed a collaboration agreement on the development of advanced imaging and software products for use in both radiosurgery and radiotherapy. The two companies will jointly focus on the integration and optimization of Siemens' CT imaging technology with Accuray's CyberKnife Robotic Radiosurgery System. They will also work towards the integration of Accuray's targeting techniques into Siemens radiotherapy product line. For more on Accuray at ASTRO, see "Different takes on image guidance" (posted November 9).

• Philips of the Netherlands announced a tie-up with the University of Florida (Gainesville, FL) on the development of proton-therapy planning software. The two partners will work closely with a consortium of clinical proton-therapy centres to guide the definition and preclinical testing phases of the project. In addition to the University of Florida Proton Therapy Institute, consortium members include Massachusetts General Hospital (Boston, MA), MD Anderson Cancer Center (Houston, TX), Paul Scherrer Institute (Switzerland) and Indiana University's Midwest Proton Radiotherapy Institute. In a separate announcement, Philips and RaySearch Medical (Stockholm, Sweden) signed an agreement to expand their current IMRT optimization OEM relationship to focus on areas such as biologically- and image-guided adaptive radiation therapy.

• IBA of Belgium unveiled a new concept, dubbed the Two-Step Particle Therapy System, which it claims will enable hospitals to begin administering proton therapy and gradually bring carbon and light-ion therapies online within the same facility. One of the key innovations is a 400 MeV cyclotron for accelerating carbon and other light ions in the clinical environment. The design also includes a proprietary ion-source switching system that allows at least eight ion species to be utilized, changing sources in less than 1 min. "At this stage, all major uncertainties have been cleared, and several major hospitals have expressed an interest," claimed Pierre Mottet, IBA's CEO. "[However], there remain regulatory and reimbursement decisions yet to be taken. Our two-step approach helps mitigate these risks, allowing an institution to get started, gain experience and financial viability with proton therapy as the first step, and add carbon therapy capability some years later – when regulatory requirements have been met and appropriate reimbursement established." For more on IBA at ASTRO, see "Astro intro" (posted November 5).

• Nucletron of the Netherlands announced the commercial launch of IPSA, an anatomy-based inverse planning algorithm that, it claims, will streamline brachytherapy planning. IPSA (or Inverse planning simulated annealing algorithm) was developed by Etienne Lesard and colleagues at the University of California, San Francisco (see also Algorithm streamlines brachytherapy planning on medicalphysicsweb). The product has been designed for 3D image-guided brachytherapy treatment planning and is available for permanent prostate implants as well as for high-dose-rate brachytherapy. According to the technical specs, optimization is guided by organ-specific dose objectives. IPSA takes into account multiple targets and multiple organs at risk (urethra, rectum, bladder, etc). The adjustment of weighting factors sets the relative importance of dose objectives for each organ and between dose conformality and dose homogeneity. IPSA automatically selects the active dwell positions and optimizes the dwell times to fulfil those objectives.

• Varian Medical Systems, US, unveiled new motion-management capabilities for its Eclipse radiotherapy treatment-planning system, "enabling clinicians to increase treatment precision for tumours in mobile areas of the body, such as the lung", according to a press statement. "The system enables clinicians to see and assess the extent of any tumour motion, and to design treatment strategies that take the motion into account so that radiation doses can be concentrated more closely on the tumour even as it moves," said Jeff Amacker, director, treatment planning systems at Varian.

Remember, this report and the posts preceding it don't pretend to be the last word on the 48th annual ASTRO meeting. As noted in the November 5 introduction to ASTRO, "there's going to be a lot of talking about a lot of stuff" - and that certainly proved to be the case. Hopefully, though, this blog goes some way towards helping readers gain a structured perspective on the more important headline themes to emerge from all that talking last week, whether in the research, clinical or industrial context.

By way of sign off, it's worth pointing out that if you attended the ASTRO meeting, either as a conference delegate or as an exhibitor, then we'd love to hear your take on the event - especially any big stories that you think really should have featured in our coverage. To fill in the blanks, just drop us a note along with some supporting details via the easy-to-use commenting facility within the blog.

Verify and localize

07.31 Friday ET: Time to round off those snapshots of IGRT strategies featured at the ASTRO trade exhibition. Resonant Medical (Montreal, Canada), for example, was leading on Restitu, a 3D ultrasound system that allows clinicians to compare 3D ultrasound images taken at both the planning and treatment stages of IGRT. The company, which was spun out of McGill University (also in Montreal), claims that this capability enables "accurate intramodality comparison for tumour-position volume verification and localization, as well as fast and accurate patient alignment".

Before each treatment session, 3D ultrasound patient data are acquired and compared with the original 3D reference ultrasound acquired in the CT-Sim room at the planning stage. "This is the first time this has been possible, as conventional ultrasound-based IGRT compares daily ultrasound images with a planning CT image," claimed Tony Falco, Resonant's chief technology officer.

In a booth presentation, Tammy Newell, radiation therapy supervisor at The Concord Hospital (Concord, NH), told attendees how Restitu's 3D ultrasound capability has been exploited at the hospital's Payson Center for Cancer Care, a facility that offers IMRT treatment to prostate-cancer patients. Newell explained that Restitu resides in both the CT-Sim and treatment rooms and calculates prostate misalignment by comparing 3D ultrasound images of the prostate acquired at both planning and treatment stages.

The key questions with IGRT, she noted, are "How do you know what you know, and how do we know this [treatment] system is doing what it is expected to do?" She added: "We have found the Restitu system to be a reliable and time-efficient IGRT device for prostate localization and an invaluable aid in GTV [gross tumour volume] definition."

Real-time surveillance

By way of closure on this theme, here are a few more technical details on AlignRT from Vision RT of the UK. This 3D imaging system for patient set-up and real-time surveillance featured briefly in the November 5 report from ASTRO. According to James Turner, the company's product support manager, AlignRT employs two ceiling-mounted 3D camera units to image the patient during simulation or treatment. The procedure is nonivasive and does not require the use of any LED markers on the chest.

At each treatment session, the AlignRT images the current patient position instantaneously. What's more, says Turner, "the unit is able to gate its image capture so that 3D data are acquired at a reproducible point in the breathing cycle." Surface-matching software subsequently registers these data to the reference surface within seconds. Couch shifts are displayed (to show inconsistencies between existing and ideal treatment positions) and new co-ordinates for the optimal couch position are displayed and may be applied.

• The final round-up of ASTRO news and views will be published Monday 13 November by 6pm ET.

16.22 Thursday ET: The battle for America is over - at least for a day or two until the Democrat and Republican fund-raising bandwagons start rolling for the 2008 presidential election. Here in Philadelphia, meanwhile, the battle for scientific kudos and equipment sales at the 48th annual ASTRO meeting is also done and dusted, with the final few conference sessions having concluded this morning and the miniature city that was the trade exhibition now being dismantled and packed away in readiness for shipping. Yet while all the talking and all the networking are done, there's still unfinished business when it comes to the write-up...

Following on from yesterday's introductory post on IGRT, today's report and Friday's will feature some of the companies who majored on the image guidance theme at the ASTRO trade show. The coverage is by no means comprehensive, but rather intended to be illustrative of the range of alternatives out there in the market. So if you're one of the vendors that hasn't made the cut, remember it was just me versus 200+ exhibitors versus the clock. In any case, don't get mad, get even - and you can do that by adding your own perspective on IGRT via the easy-to-use commenting facility within this blog.

Think robotic, think radiosurgery
First port of call was Accuray, the US company which has pioneered the CyberKnife System for robotic radiosurgery. Among the new products featured on its ASTRO roster was the Xsight Lung Tracking System. One of a suite of products for the treatment of peripheral lung tumours, Xsight Lung works in combination with CyberKnife to track, detect and compensate for the motion of the tumour and patient during the breathing cycle. What's more, it does so non-invasively without the need for gating or breath-hold techniques.

During lung radiosurgery, "the major challenge is motion compensation", explained Omar Dawood, Accuray's senior manager, clinical programmes, in a booth presentation. Xsight Lung initially references on the patient's bony anatomy to set up the patient globally. It then uses sophisticated image processing and registration techniques to directly lock onto and track the tumour throughout radiosurgery treatment.

The end game here for Accuray is a motion-tracking and compensation scheme that eliminates the need for invasive placement of gold fiducials in the lung tumour - a procedure which has been associated with a high risk of pneumothorax and chest-tube placement.

"This [Xsight Lung] is a big breakthrough, with shorter time to treatment," added Dawood. "Evaluation of clinical data demonstrates that it works well for peripheral lung tumours greater than 15 mm in size, with a targeting accuracy better than 1.5 mm."

Accuray's previous generation of motion-compensating technology is called the Synchrony Respiratory Tracking System. Launched in 2004, Synchrony uses LED markers on the chest and implanted gold fiducials to visualize the tumour internally through treatment. According to Dawood, "Xsight Lung incorporates the benefits of Synchrony without requiring fiducial markers."

Also debuting at ASTRO were Accuray's
• Xchange Robotic Collimator Changer, which has the automated ability to change secondary collimators during CyberKnife treatment. This eliminates the need to re-enter the treatment room and helps to minimize related delays.
• 4D Treatment Optimization and Planning System, which takes into account not only the movement of the tumour, but also the movement and deformation of tissue. The aim is to enable clinicians to better deliver the prescribed radiation dose to the targeted area while minimizing damage to surrounding healthy tissue.

True stories
A few booths away and another take on image guidance was being pushed by TomoTherapy (Madison, WI). Here the emphasis was not just on image guidance - and accuracy in daily patient set-up - but also on adaptation (i.e. what the clinician is able to do with the images acquired during the course of treatment).

First some context. TomoTherapy's flagship product, the Hi.Art conformal radiotherapy system, comprises a linac mounted on a rigid ring gantry (as opposed to a C-arm). The technology was pioneered by company founders Thomas "Rock" Mackie and Paul Reckwerdt at the University of Wisconsin-Madison in the early 1990s. The result of this innovation: 360 degree helical delivery of IMRT with integrated megavoltage (MV) CT imaging (think of it as IG-IMRT).

Think adaptive

Unveiled at ASTRO, CTrue is the latest iteration of TomoTherapy's CT imaging technology for IMRT. In a product presentation on the company's booth, Liz Frisch, TomoTherapy's clinical applications manager, called CTrue "the gold standard for IGRT", allowing "you to image your patients every day if you want" for comparison with the kV CT image obtained at the treatment planning stage. In a related press announcement, Mackie was even more bullish: "If you don't have CTrue technology, you cannot use images to quantitatively assess the progress of treatment and, when necessary, to provide adaptation during the course of radiotherapy. And adaptive radiotherapy is all about maintaining accuracy and precision throughout the whole course of treatment."

To sum up: CTrue equates to MV CT imaging for all anatomical locations - and with very low delivered dose - to ensure accurate delivery of helical IMRT. Subsequent quantitative analysis using the company's Planned Adaptive software provides the logical extension of that capability: "You can also adapt the plan throughout the course of treatment to maintain the doctor's prescription," added Frisch.

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.

Places to go

07.44 Wednesday ET: That authentic US election-night experience flagged up in the last blog posting turned out to be a somewhat pedestrian affair - i.e. pepperoni pizza and a couple of beers at the bar in Pietro's (a top-notch Italian restaurant on the corner of Walnut and 17th Street). After a coffee from Starbucks, it was back to the hotel for another full-on assault from CNN, a channel which, over the past few days, has clearly decided that all other news bar the mid-term elections is cancelled. Though it's worth noting that producers did make space for a breaking news flash Tuesday afternoon about pop babe Britney Spears filing for divorce from husband Kevin Federline (the subject of some debate among tired reporters and staff in the ASTRO press office yesterday evening). Seizmic shenanigans like this apart, the ASTRO meeting rolled on relentlessly...

PET insights on hypoxia
For this correspondent, Tuesday kicked off with a plenary session featuring the top three physics papers at this week's conference. First up, Kelin Wang from the department of medical physics at Sloan-Kettering Cancer Center (New York, NY) presented the results of an 18FMISO-PET study in which he and his colleagues modelled transient and chronic tumour hypoxia (a low-oxygen state that makes tumours more resistant to chemo- and radiotherapies). The work secured Wang the resident clinical/basic science award from ASTRO's scientific committee.

The New York team performed serial 18FMISO-PET pretreatment scans on 20 patients to ascertain possible changes in hypoxia distribution. Their conclusion: "These results, for the first time, provide information concerning the partition of chronic and transient hypoxia in human cancers, and as to how they may influence hypoxia imaging using PET."

In a neat touch, and one that other scientific conferences could learn from, the ASTRO committee asked independent experts to provide brief supporting commentaries on each of the three plenary papers. The discussant on Wang's paper, Mark Dewhirst (Duke University Medical Center, Durham, NC), noted that the work shows "intermittent hypoxia has a complex frequency distribution over time [and that] spatial distribution data suggest large networks of vessels are involved."

Radiation sensitivity in the liver
Next, Yue Cao from the University of Michigan (Ann Arbor, MI) presented results of a study to predict radiation-induced liver dysfunction (RILD) using a local dose and regional venous-perfusion model. "We have shown that high dose conformal radiation combined with chemotherapy appears to prolong the survival of patients with unresectable intrahepatic cancers," note Cao and her co-workers in their ASTRO paper. However, they add that "the ability to safely deliver higher doses is primarily limited by the development of RILD, characterized venous occlusion".

During their research, Cao and colleagues developed a hypothesis that early monitoring of venous perfusion would have the potential to select patients with preclinical signs of perfusion changes prior to the onset of symptomatic radiation-induced injury. Preliminary data suggest that their local dose and regional venous perfusion model does indeed have the potential to "predict individual sensitivity to radiation". Cao described the work as "the first step toward developing a method to delivery of higher and potentially more curative radiation doses to the patients who can safely receive those higher doses".

In her supporting commentary on Cao's talk, Laura Dawson (Princess Margaret Hospital, Toronto, ON, Canada) explained that the work is useful because it will help "to improve understanding of radiotherapy liver toxicity, with an ability to measure regional injury". The challenge now, she says, is "correlation of perfusion with clinically important liver function [and] reproducibility of dose-dependent perfusion in larger patient populations".

Radiation toxicity in the brain
The third plenary paper in the physics session was presented by Vijaya Nagesh from the department of radiation oncology at the University of Michigan. Using diffusion-tensor MRI, Nagesh and colleagues carried out a quantitative characterization of radiation-dose-dependent changes in normal-appearing white matter of patients with cerebral tumours. The study group comprised 20 patients who underwent 3D conformal radiotherapy.

The work is significant because radiation can have a number of effects on normal brain tissue, manifesting in neuroinflammation, demyelination and disruption of the blood-brain barrier. There can also be delayed neurological problems caused by white-matter necrosis. Yet these effects are poorly described so far, plus there may be multiple compounding factors (e.g. use of steroids, addition of chemotherapy, tumour recurrence and even the use of anti-epileptics).

Nagesh and her team found that quantitative diffusion-tensor MRI revealed acute and sub-acute effects of radiation in normal-appearing white matter (specifically, the genu of the corpus callosum). They conclude: "The decreased anisotropy of water diffusion indicates [a] reduction in restriction of water in the direction perpendicular to the fibre axis, possibly due to demyelination. The increase in mean diffusivity suggests overall structural degradation of white-matter fibre."

In summary, Nagesh's work shows that the ability of diffusion-tensor MRI to evaluate the susceptibility of white matter to radiation injury may well be valuable for predicting delayed neurological dysfunction. What's more, as MRI technology improves, greater resolution may well lead to a more detailed understanding of cause and effect.

• Sharp-eyed readers of Monday's blog post might be wondering what happened to the article on image guidance in radiotherapy. It's still a work in progress. I have to catch up with a couple of vendors at the exhibition today, after which there'll be a round-up of different approaches being pursued in IGRT later on this week.