- Measuring tumors by volume and not by length aids in detecting tumors accurately
- Water in a disposable diaper closely resembles the structure of a tumor
- The volumetric approach outperformed RECIST method with the improved diaper phantoms
Using diaper 'phantoms' show that the tumors can be detected accurately by measuring volume and not length, reveals a new study.
Detecting cancer early can lead to successful treatment. X-ray computed tomography (CT) is a common screening practice that measures the growth of the tumor growth, which takes a series of cross-section images of the body.
Previously, they have been used in the clinics. The research team tests multiple CT imaging techniques with standard objects called "phantoms." Phantoms were designed to mimic real tumors accurately.
Improved Tumor Measurements
In a pursuit of finding better tumor measurements, the research team at the National Institute of Standards and Technology (NIST) found a practical and unconventional solution such as injecting water into disposable diapers.
"It may sound strange, but it turns out that water in a disposable diaper closely resembles the structure of a tumor in tissue," explained NIST physicist Zachary Levine, the lead author of a new report published in the NIST Journal of Research.
Moreover, these tumors can be grown precisely like the real ones by just adding more water, revealed the research team.
A decade-long question can now be resolved with these ordinary ingredients. The problem as to which is the best way of interpreting CT images is whether by measuring the length of the tumor or volume?
The length approach is widely used by a standard measurement called RECIST (Response Evaluation Criteria in Solid Tumors), which was initially proposed in 2000.
Measuring the Tumor by Length
The size of the tumor in any CT slice is determined by its largest measured length when using RECIST., regarding that, a change in size means a change in length. This method has come from early X-ray CT, where two-dimensional images were shown onto film, and various other features were measured by hand.
On the other hand, volumetric measurement combines all the two-dimensional slices to form a three-dimensional volume and hidden structures can be revealed within this volume.
This is a novel approach, and the research team is still investigating as to how accurate this method is at measuring tumor mass while comparing it to other techniques.
The NIST team loaded many diapers with small amounts of water to compare both the methods and imaged each diaper with X-ray CT.
After which, more water was repeatedly injected and the team re-scanned each diaper, weighing them both before and after to determine the amount of water that has been added.
Later, the water mass was estimated at each step by using both volumetric measurements and RECIST.
Measuring the Tumor by Volume
With the improved diaper phantoms, it was found that the volumetric approach outperformed RECIST by at least a factor out of five in estimating the water mass for each phantom.
The results show that for real tumors, rather than RECIST length, measuring the volume could be a more reliable predictor of mass.
The research team hopes to show that volumetric measurements are convincingly better by the next review of RECIST, said Levine.
Adopting more accurate methods enables physician's to screen early for tumors and also instantly determine if the treatment is working or not.
- Zachary H. Levine1, H. Heather Chen-Mayer, Adele P. Peskin, and Adam L. Pintar. Comparison of One-Dimensional and Volumetric Computed Tomography Measurements of Injected-Water Phantoms. Journal of Research of National Institute of Standards and Technology (2017).