3D images aid radiotherapy planning

22 Nov 2006

An innovative imaging system could enable radiation therapists to target tumours more effectively.

A study led by researchers at Rush University Medical Center on Chicago, US, has concluded that a novel 3D imaging system could help medical teams to optimize the effectiveness of radiation therapy. The PerspectaRAD system, developed by Actuality Systems of Bedford, Massachusetts, combines radiation therapy software with a hologram-like display to create 3D images of the treatment area.

Radiation therapy is most effective when high radiation doses are concentrated on tumours, while minimizing the dose to surrounding critical organs. But many of the planning tasks -- such as beam placement, volume delineation and plan evaluation -- are 3D in nature, while the displays used to evaluate the imaging data are 2D.

The PerspectaRAd system solves this problem by producing 10-inch diameter 3D images inside a transparent dome. The images are created by using high-speed electronics to project nearly 6000 images per second onto a screen that's spinning at more than 900 rotations per minute.

This spinning screen creates a detailed, full-colour holographic image that can be viewed and manipulated from any vantage point around the dome, and by any number of users. By projecting CT scan images onto the screen, the system can reveal the exact location of tumours in true 3D space.

With this in mind, the Rush University researchers set up a study to evaluate the potential of the 3D display device. Theyreplanned existing treatment plans (12 previously treated brain-cancer patients, plus one lung-cancer and one breast-cancer patient) with and without PerspectaRAD.

The replanned data were then reviewed by four physicians who were unaware of which planning device had been used. They judged the PerspectaRAD plans to be superior for both the lung-cancer and the breast-cancer patients. Of the 12 brain-cancer patients, four PerspectaRAD-guided plans were considered equivalent to the rival plans, six were judged as better, and two were considered worse (owing to increased doses to the optic nerve and brainstem with no improvement in target coverage).

All of the reviewers felt that the holographic imaging device enabled them to appreciate the 3D relationships of anatomical and dose distribution data better than images from a flat-screen display. The location and size of over- or underdosed regions were also easier to identify using PerspectaRAD.

According to the research paper, which was presented at the annual meeting of the American Society for Therapeutic Radiology and Oncology (ASTRO) in Philadelphia, "these data demonstrate that PerspectaRAD has potential to achieve better plan quality in radiation treatment planning, even though it does not yet improve planning efficiency".

Michael Goldstein, Actuality's president and chief executive officer, told medicalphysicsweb that many other imaging technology developments in the pipeline. These include an ultrahigh-speed physics engine designed to cut computation time for treatment planning; a 3D holographic workstation for diagnostic imaging; a 5000 × 4000 pixel, film-quality display for mammography; and an image-guided surgery system for breast surgery. "These 3D systems also work well for the visualization of structures in molecular engineering," he added.

Crystal ball The PerspectaRAD Spatial 3D System creates 10 inch-diameter holographic images with a 360° field of view. Photo courtesy of Actuality Systems. Colour coded Multicolour volumetric data of a CT scan displayed on the PerspectaRAD. Photo courtesy of Actuality Systems.