Australian centers boost SBRT and VMAT capabilities

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Three New South Wales centers upgrade linear accelerators with Elekta’s Agility MLC and advanced imaging software

Along a 500 km coastal stretch of Australia’s most populous state, New South Wales (NSW), are three radiation oncology centers that are leading the way in cancer management. The centers – representing two NSW health districts – opted to supercharge their six linear accelerators with key upgrades in 2015-2016. These included integrating the Agility™ MLC, acquiring XVI 5.0, including XVI imaging tools, and implementing the latest Integrity™ control system hardware. The three clinics in Coffs Harbour, Lismore and Port Macquarie also switched their treatment planning from XiO® to Monaco®.

The overall benefits have been better plans, more conformal dose distributions and faster treatment delivery.

From May 2007 to October 2011, the Northern New South Wales Local Health District (Lismore) and Mid North Coast Local Health District (Coffs Harbour, Port Macquarie) jointly installed Elekta Synergy® systems, two at each center, launching a new era of advanced radiation therapy in the region.

“When we were going clinical with Lismore’s and Port Macquarie’s second linacs, I was very keen to purchase an Agility MLC for those systems,” says Stuart Greenham, Radiation Therapy Manager for the Mid North Coast Local Health District. “We realized that we could gain better beam-shaping capabilities and speed with Agility. The software upgrades that had been released for Elekta Synergy over the preceding four years would also bring us new clinical advantages, most notably improved VMAT capabilities. We’ve been on a constant quest to extract the maximum performance out of the linacs, so the upgrade seemed like it would give us that a lot earlier versus waiting for a linac replacement down the line.”

By March 2016, all six of the districts’ Elekta Synergy systems had been upgraded. Greenham adds that there was no loss of service at either of the health districts during the upgrades, because patients were simply transferred to each site’s second Elekta Synergy, which ran extended hours to compensate.

Agility increases patient throughput – among other clinical advantages

The transition from MLCi2 to Agility has yielded significant benefits at the three centers, reports Andy Kovendy, Director of Medical Physics, North Coast Cancer Institute.

“The 160 5 mm interdigitating leaves of Agility enable us to more closely conform to the target shape, especially small tumors close to organs-at-risk,” he says. “In addition, the 6.5 cm per second leaf speed not only makes it feasible to easily treat larger targets, but also to fully exploit the speed of VMAT delivery. This has been particularly noticeable when combining Agility with Elekta’s continuously variable dose rate [CVDR].

Port Macquarie radiation therapist Gareth Livingston adds that having the same 5 mm leaf width across the entire 40 X 40 cm treatment field has been advantageous.

“It means we don’t have to limit highly conformal treatments to tumors in small fields – we can provide them for all of our patients,” he says. “The Agility leaf transmission also is extremely low – less than 0.5 percent – which means we can decrease the beams’ lateral spread and reduce the dose to healthy organs and tissues.”

“The clinical staff told me that with Agility they have seen some nice gains in our dosimetry, everything else being equal,” Greenham adds.

Across the three NSW centers, the combination of Agility, CVDR and a complete hardware change to the control subsystem has resulted in an approximately 50 percent increase in the use of VMAT, with a concomitant increase in daily throughput.

“Our ability to deliver VMAT for more cases has boosted the maximum achievable patient volumes by 10 to 20 percent,” he says. “That means more people treated and treated on time with a higher quality dose distribution. Most treatments done with traditional IMRT and are now VMAT, but VMAT has paved the way for a new group of patients with different conditions to benefit.”

XVI imaging tools focus on better targeting

Since the upgrade of their Synergy systems, the districts’ radiation therapy centers have been exploiting key software innovations comprising Elekta’s XVI advanced imaging tools, specifically for respiratory motion management (4D CBCT) and critical structure avoidance.

4D CBCT image guidance accurately positions mobile lung tumors, enabling better targeting of these lesions and treatment is delivered with a continuous, non-gated radiation beam while the patient breathes freely. In addition to respiratory motion, the imaging tool helps manage baseline shift – the tumor’s intra-fraction migration from the original planned position.

Clinicians at the three centers also have been using critical structure avoidance to ensure that not only is the tumor’s position accurately accounted for, but also the position of nearby critical structures.

“The dual registration capability allows us to set tolerances for organs-at-risk to avoid putting critical structures in the radiation beam’s path,” says Tom Shakespeare, MD, medical director of the three New South Wales centers. “We use dual registration in a number of clinical settings, including dual target mono-isocenter techniques, thoracic soft tissue alignment – with a second clip-box registration around the spinal cord – and in cases in which a target abuts a prosthesis.”

Port Macquarie radiation oncologist Andrew Last, MD, adds that dual registration has reduced the guesswork in certain clinical scenarios and can help answer questions about whether OAR or target misalignment is acceptable, or whether a compromise between the two is suitable.

“The XVI advanced imaging tools – especially dual registration – gave us more confidence to go into that space,” he says. “We’ve done more lungs with VMAT than ever before and we use 4D CBCT for all of our SBRT cases. Some people are a bit nervous about IMRT in motion, but the information we get from imaging gives us the assurance we need, all for the cost of 30 or 40 seconds of imaging time.”

Upgrade to XVI 5.0 streamlines workflows

The centers also upgraded to XVI 5.0, which features improved 2D kV imaging workflows, in addition to distributed imaging and treatment. The latter enables patient data to be easily moved between XVI workstations, without the need to recreate or reapprove the registration parameter settings in XVI. XVI reference data distribution is available throughout the department via MOSAIQ®, with images automatically associated in the EMR.

“We were already struggling as a spread out site with the requirement to load data at the imaging console, so distributed imaging and treatment is certainly an easy win we gained by having that remote loading capability,” Greenham says. “It is just a more effective use of peoples’ time and they can load data from elsewhere using MOSAIQ as well.”

All three centers have been using MOSAIQ since the very beginning in 2007, making them filmless and paperless since day one.

Monaco provides high performance, high precision planning

The NSW centers had been using the XiO treatment planning system from 2007 until early 2016, at which time they fully decommissioned electron treatments. The clinics have been 100 percent Monaco photons for approximately a year.

“Soon after upgrading to Monaco 5.1, we essentially went to 3D CRT,” Greenham recalls. “In the last six months we’ve also commissioned the electron Monte Carlo, so now we’re completely Monaco and keeping XiO only for plan review.”

According to Kovendy, the increase accuracy provided by the Monte Carlo algorithm has been very important, particularly for thoracic [air] and head-and-neck cases.

“Monaco also gives us more and superior cost functions, which translates into more control over the dosimetry and likely improved plans as well.”

He adds, “And the system is equipped with great, user-friendly optimization tools, which means fewer user-defined structures need to be created.”

Greenham observes that Monaco has allowed the NSW centers to integrate its 4D software with the primary TPS, making 4D procedures “less cumbersome.”

“Also, now that we have Monaco, we have pretty much 0 percent physics failures,” he says. “The result has been that fewer plans have to be re-done to pass pre-treatment QA.”

A new tradition of progress

As much as the original installation of six Elekta Synergy systems at the NSW radiotherapy centers in Coffs Harbour, Lismore and Port Macquarie was a major step for the territory and the health districts, the recent upgrades of these systems were equally significant. With enhanced beam-shaping and target imaging capabilities, in addition to more effective treatment planning and streamlined workflows, clinicians are providing their patients with the highest standard of cancer treatment.

“The original Synergy systems essentially brought radiation therapy capabilities to New South Wales where none existed before,” Greenham says. “Their upgrade with Agility and advanced imaging tools, in addition to Monaco planning, has really brought the districts’ radiotherapy services to world-class cancer care and is an investment for the future.”

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