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Probably the last word on IGRT (this week)
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.”
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.
