Deformable registration QA ups planning accuracy

Mirada Medical launched RegistrationQX, a tool for quantitative quality assessment (QA) of deformable image registration. "Deformable image registration is increasingly used in radiotherapy planning to combine multiple imaging modalities in order to define targets and critical structures," said Mirada's Paul Meskell. "The more accurate the registration is, the more accurate the treatment planning is." Registration accuracy is typically checked qualitatively using fusion overlays and visual inspection of the deformation field. But this subjective approach results in significant inter-user variability.

To address this limitation, RegistrationQX offers quantitative QA. In a demonstration of the new software, senior research scientist Mark Gooding explained how the tool examines three aspects of the registration: the biological plausibility of the deformation fields; the local similarity between the two images and the numerical robustness of the solution. It then calculates the percentage of voxels considered acceptable, produces numerical scores for each anatomical structure and automatically generates a report, flagging any errors that need checking.

RegistrationQX will become part of Mirada's RTx product, and will be available with the next major release. "As RegistrationQX gives quantitative scores, it provides an objective measure of how trustworthy the registration is," Gooding told medicalphysicsweb.

Dual balloon keeps brachytherapy on target

Best Medical showcased its Best Dual-Balloon Breast Brachytherapy Applicator. According to Michael Cutrer, director of business development, the applicator's key differentiator is its ability to move the treatment sources away from the centre of the device. "Existing balloon-based products have the treatment catheters in the middle," he explained. "The challenge is to get away from the central region, to better conform the dose to the treatment target while avoiding overdose of critical structures."

To do this, the new applicator uses a dual-balloon design, with one central treatment catheter and four surrounding catheters. Once placed in a lumpectomy cavity, the outer balloon is expanded to reshape the resection cavity and then the inner balloon can be inflated independently. This allows the physician to position the four outer catheters to provide the best dose distribution according to the individual tumour location.

Cutrer notes that the applicator uses the same 1 cm incision as other brachytherapy products. "This device can go through a 1 cm incision, but can then be expanded beyond 1 cm," he said. "And at the end of the treatment, it is collapsed down and can be removed." Best Medical plans to launch the applicator (which already has FDA 510(k) approval) for clinical use in late-July or August. Future developments will include 1 cm smaller and 1 cm larger versions, as well as adaptation of the dual-balloon concept for other treatment sites such as the rectum or bladder.

Software update enhances brachytherapy planning

Varian Medical Systems introduced a faster version of VariSeed, its brachytherapy treatment planning software. VariSeed is a well-established product, with around 1600 systems installed in more than 40 countries worldwide. This newest version is said to help improve workflow, speed up the planning process and enhance the precision of low-dose-rate (LDR) brachytherapy planning.

"The latest release of VariSeed also offers a new VariPath module for transperineal ultrasound-guided prostate biopsies," Varian's Geneviève Lafrenière told medicalphysicsweb. She explained that the biopsy needles are tracked so that the exact locations of the biopsy sites are known, and this information is imported back into the system. The data and images from the biopsy can then be exported for use in external-beam or brachytherapy planning, with the additional option of fusing the findings with MR images.

Another new feature is that VariSeed can now be used for planning other treatments, such as LDR breast brachytherapy, for example. "It's not just for prostate any more, it can be used for other sites," said Lafrenière.

QA accessory speeds CyberKnife checks

Standard Imaging released a host of new products, including an accessory for use with the CyberKnife radiosurgery system. The new device – called the Cutting Board – enables daily quality assurance (QA) of the CyberKnife using the company's QA BeamChecker Plus (QABC+), a self-contained daily QA device. The QABC+ fits precisely onto the new accessory, which contains implanted fiducials that enable accurate alignment using the CyberKnife Treatment Localization System (TLS).

Andy Simon, product marketing manager at Standard Imaging, explained that previously, CyberKnife QA took more than half an hour and required a complex ionization chamber system. With the new accessory, an accurate daily verification of beam output can be performed in just eight minutes (from setup to breakdown). He noted that daily output QA can performed by therapists, without requiring any manual manipulation of the CyberKnife robot.

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