Radiotherapy errors can occur at many points along the planning and treatment timeline, making quality control and QA more necessary now than ever. QA has also become more effective and efficient, with an ever-increasing number of tests and measurements used to assure patient safety, which have grown more sophisticated and complex over time. However, QA technologies for radiotherapy dose monitoring haven't kept up with advances in radiotherapy.

Examples of reported radiotherapy errors include:
• Devices for shaping or modulating radiation beams being used improperly or even left out, resulting in beams not reaching the target.
• Dosage miscalculation errors, sometimes merely arising from misreading instructions.
• Data errors resulting from problems such as corrupted software files, and misunderstanding of how the data are derived.
• Incorrect patient positioning: correct equipment set-up and calibration doesn't protect patients from radiation beams hitting the wrong tissue if they are positioned incorrectly, move slightly or if internal organ motion interferes with beam-targeting.
• Devastating problems due to pure carelessness such as patient record mix-ups resulting in treatment of the wrong patient or body part. Thankfully, such errors are extremely rare.

It's clear that radiation physicists, therapists, oncologists and manufacturers must work together to reduce errors. While finger-pointing about who is to blame for errors isn't productive, studies of what is to blame have led to recent improvements.

Qualitative QA research

Over the past 18 months, ScandiDos, a Swedish provider of dosimetry and QA products, has conducted qualitative research to investigate which QA characteristics are most important to radiation centres and how these centres evaluate QA systems. At the end of 2013, Opticom International Research conducted a qualitative survey on behalf of ScandiDos.

In late 2014/early 2015, further research was carried out to update the earlier survey. This involved discussions with a medical physicist: Alonso N Gutierrez, assistant professor at the University of Texas Health Science Center at San Antonio, and an oncologist: Björn Zackrisson, radiotherapy professor at Umeâ University Hospital in Sweden.

The research showed that professionals view new technology as both a challenge and an opportunity, and expect future challenges from continued high workloads. Radiation therapy's complexity is expected to increase, bringing greater need for thorough QA, possibly driven by increased regulations. Participants cited high workloads as a factor that slows the speed of adopting new technology, and picked faster QA per patient as the main opportunity for near-future development.

In the interviews with Guttierrez and Zackrisson, two major areas of concern and need for improvement in radiation therapy QA emerged: the inability to verify the actual radiation dose delivered to the patient during the procedure; and inadequate staffing at radiation therapy centres. Both expressed concerns about the lack of technology available to verify the delivered radiation dose in real time. This shortfall is exacerbated by factors that can alter the way radiation beams reach the target: daily consistency of patient positioning; motion by the patient or the organs; and physical changes in the patient such as weight loss.

Guttierrez thought that the biggest challenge faced at his centre is the ability to adapt to patients' anatomical positions every day. "Medical physicists need technology to verify new plans created on a daily basis to account for anatomical changes, which current MRI-based imaging systems can't do," he said.

Zackrisson concurred: "Handling uncertainties concerning variation in the position, size and motion of target volumes and organs-at-risk is a very important task for the radiotherapy community. Modern radiation delivery systems allow highly conformal treatments, but the systems' capabilities may not be fully utilized due to uncertainties."

Dose delivery dilemma

The concerns of Guttierrez and Zackrisson were reflected by the Opticom survey responses. In answer to the question "what are the major concerns when you are treating the patient, to ensure safe, accurate treatment?" the second, third and fourth most frequent responses were patient position, movement and physical changes. However, the biggest concern expressed by the clinicians surveyed was "the actual delivery".

In explaining his concern about not being able to verify the actual delivered dose, Guttierrez referred to the use of conventional X-ray-based cone-beam CT in the current process of adaptive radiotherapy and said that he hoped real-time volumetric imaging would be possible in the future. "MR-based radiotherapy devices will be the pathway to that goal," he said. "Because we're adapting plans, we must find a way of verifying correct dose delivery."

Guttierrez and Zackrisson both expressed interested in equipment that can verify radiation dose delivered during treatment. Zackrisson said that such equipment would be a significant step towards true adaptive radiotherapy. "I would be eager to explore such a system, and so would my physicist colleagues," he said.

Guttierrez's ideal specifications for this kind of equipment include the ability to verify plan parameters and check the radiation beam shape, gantry position and geometry of the patient's anatomy, as well as to measure the quantity of radiation being delivered, all on a daily basis. "The holy grail is the ability to assess when deviations are large enough to require adjustment of treatment parameters," he said.

He noted that radiation teams verify pre-treatment plans with a QA device, but during treatment, most centres just assume correct dose delivery. "Some large research centres use the EPID [electronic portal imaging device] for exit-dose dosimetry, which can potentially reconstruct the delivered dose," he said. "Researchers preach that's how to do it, but it requires resources that most centres don't have."

Lack of human resources – inadequate staffing – was a recurrent theme in the research. "Reimbursement cuts have made most radiation therapy centres extremely cost-conscious and efficiency-oriented," said Guttierrez. He noted that the goal for new equipment should be to improve quality for better efficiency, but most new equipment improves quality but not efficiency. "It takes time to understand the system, creating a lag time before quality improves. Many events in treating patients have arisen from insufficient equipment training."

In the Opticom survey, workload was the biggest challenge cited by the highest number of medical physicists surveyed, reinforcing Guttierrez's opinion about inadequate staffing.

Asked whether the many different pieces of equipment and screens at the control desk create a confusing working environment for radiation therapists, Zackrisson said: "The more complex the environment, the larger risk for errors. User interfaces are not always intuitive, increasing the risk."

On a practical note, Guttierrez remarked on the role of reimbursement in equipment purchase decisions. "Many of our tools require a high capital investment. We'd all like the ability to check every fraction every day, but if there's no reimbursement model for using the equipment to do that, it's hard to justify the expense."

Looking ahead

ScandiDos' research reveals that radiation oncology professionals are positive about the future. They see opportunities for better QA technology to improve the quality of radiotherapy, increase patient safety and/or improve the clinic workflow. The research also highlights a need for – and a strong interest in – QA systems that measure the delivered radiation dose.

As such, ScandiDos has been working to address this challenge with the development of new technology. "ScandiDos has expanded its Delta4 dosimetry system to include Delta4 Discover," reported Görgen Nilsson, president and CEO of ScandiDos. "This new system employs 3D and 4D volumetric dosimetry and monitors the delivered dose to patients." The new equipment is currently being evaluated by clinics in the US, Europe and the Asia-Pacific region. ScandiDos expects to launch Delta4 Discover to the market this spring, and pending regulatory approvals, it will be available worldwide.

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