How We Do It: Volumetric Imaging in Pediatric Radiology

Since its very first days as a small pediatric hospital in Arizona, Phoenix Children’s has fostered a culture of ingenuity and invention. Today, as one of the largest pediatric health systems in the country, innovation continues to touch each corner of our enterprise. From launching the nation’s first pediatric clinically integrated organization to taking the reins of the Pediatric Consortium of Cancer Moonshot 2020, Phoenix Children’s commitment to progress and improvement can be seen in every aspect of patient care.

This ethic is very much evident within Phoenix Children’s division of pediatric imaging. Our physicians, nurses and technologists work exclusively with pediatric patients and are specially trained to identify and treat childhood diseases and anomalies. We continue to seek new opportunities to improve protocols and technologies for safer, faster and more accurate test results for children.

For example, Phoenix Children’s 3-D Innovation Lab is transforming the way physicians approach diagnosis and treatment across all medical disciplines. We are among the first in pediatric hospitals to marry 3-D printing and advanced post-processing technologies, allowing our providers to create accurate models of orthopedic fractures, injured internal organs, congenital heart defects and even tumors.

We utilize the lab in a variety of ways, but perhaps most promising is our method for measuring the size of malignant tumors. Tumors are notoriously difficult to measure given their unusual sizes and shapes. Current protocols call for measuring tumors using length, width and height—or XYZ—data. This method is problematic because the margin of error can be as high as 200% to 300%, creating a significant challenge in determining appropriate therapies in patients with malignant tumors. At best, XYZ provides a guesstimate of a tumor’s true volume.

Finding a better way

At Phoenix Children’s Hospital, we set out to find a better way to measure tumors and minimize (or better yet, eliminate) the margin of error. Our hope was to provide oncologists with precise measurements that would allow them to identify the most appropriate treatments for patients fighting life-threatening cancers. In our pilot study, we charged four radiologists with measuring tumors in the brain and body using XYZ data. Meanwhile, three staff technologists measured the same tumors using 3-D data. Then, we created a 3-D printed rendering of each tumor to find the actual shape, size and volume.

Given the extensive training and expertise of our radiologists, we anticipated their measurements would be close to accurate, but the opposite was true. There was a significant degree of variation among the radiologists’ measurements, yet the technologists’ results all were nearly identical, and with only a tiny margin of error.

If XYZ data is variable and unreliable, as this pilot study suggests, then the risk of making errors in measurement is high. Moreover, if the data isn’t reliable, oncologists cannot make informed treatment decisions for their patients. Considering the fact that cancer kills more children than any other disease, reliable data is critically important in identifying the most viable course of treatment, and may even mean the difference between life and death.

 While a large perspective study on the differences between XYZ and 3-D volume measurement has yet to be completed, it is easy to extrapolate from our pilot program: More accurate measurement will lead to more informed treatment decisions, ultimately improving outcomes for kids whose very lives are at risk.

We believe the superior precision and capability of 3-D volume measurement will create a sea change in radiology practice in the treatment of pediatric cancer. Oncologists rely heavily on the protocols set forth by the Children’s Oncology Group (COG), which has identified the treatments that yield the highest rate of survival and serves as an invaluable resource to physicians and their patients. While the COG currently uses the XYZ method in tumor measurement, we are hopeful that 3-D volume measurement will become the new standard.

Into practice

Working in tandem with our pediatric oncologists, we have already begun using this method to benefit Phoenix Children’s patients and hope to bring it into common practice. In one recent case, the difference between the XYZ and 3-D volume measurement of a patient’s tumor crossed a treatment threshold; the oncologist used the more accurate volume measurement to determine the appropriate therapy.

Harnessing 3-D data also allows us to identify subtle changes in tumor size or shape over time. This has become a valuable tool in determining whether chemotherapy or other treatments

are shrinking a patient’s tumor. Not only does this measurement provide precise feedback to physicians about the effectiveness of treatment, the data also can serve as evidence to payors that treatments are working and must be continued—especially in cases where changes are difficult to measure. Given the costly nature of many cancer treatments, payors must know the money is being well spent and therapies are making a meaningful difference.

In addition, volumetric imaging makes sense operationally. The measurement can be completed by radiologists or technologists with 3-D training. At Phoenix Children’s Hospital, our technologists head up this charge, as it is less costly and their results have proven more reliable. Moreover, the work does not require a special 3-D Innovation Lab like the one in use at our hospital. With the right imaging equipment, 3-D measurement can be performed on a scanner console or offline by technologists or radiologists.

From a cost perspective, expenses are limited to imaging equipment and other dedicated computers, hardware and software. There is a small charge for some 3-D work that is performed offline.

The cost and operational considerations are nominal when weighed against the benefits. The opportunity for true precision in tumor measurement—and the promise of improving pediatric practice in cancer and across all medical conditions—serves as a powerful motivator here at Phoenix Children’s.