Lithiasis size estimation variability depending on image technical methodology

Abstract

lithiasis >0.5 cm, intact, and visible via simple radiography. A sample of 245 lithiases was obtained, with 87 rejected as they did not fulfill the inclusion criteria. Initially the three main actual diameters of each lithiasis were measured with a calibrator, then a plain X-ray and a CT scan were taken of the samples to determine the surface size in cm(2) for simple radiography; surface size and volume in cm(3) for CT scan, in bone window and soft tissue (Toshiba Aquillion 64, sections of 0.5 mm, 120 Kv, 250 mA). The tomographic area was calculated by employing the formula recommended by the European Association of Urology and scanner software. The actual, radiographic and tomographic measurements were taken by three different researchers who were unaware of the results obtained by the each other. The statistics program IBM SPSS Statistics(®) 19 was used. Differences were analyzed using the Wilcoxon sign test. The bone window CT scan slightly overestimated the actual lithiasic size (0.12 vs. 0.17 cm(3)), while in soft tissue window the actual volume was practically doubled (0.12 vs. 0.21 cm(3)) (p < 0.05). We did not find statistically significant differences in the comparison between actual surface size (0.39 cm(2)) and bone window CT scan size when using the EAU formula or scanner software (0.36/0.37 cm(2)). Resulting measurements in soft tissue window tended to significantly overestimate the surface size, although only slightly (0.42/0.44 cm(2)), whilst the plain radiography underestimated it slightly but significantly (0.37 cm(2)). CT scan, using the bone window, is the technical methodology with which the greatest in vitro accuracy in which actual lithiasis measurements can be estimated, although the craniocaudal diameter measurement will be overestimated. Using soft tissue window gives an overestimated size.

Influence of a Deep Learning Noise Reduction on the CT Values, Image Noise and Characterization of Kidney and Ureter Stones

“…Both methods are described in the literature [ 5 ], though they are known to provide different measurements. Usually, soft-tissue window settings tend to overestimate stone size, while bone window settings tend to slightly underestimate stone size [ 6 ]. Furthermore, the attenuation is influenced by the size of the measurement area (region of interest) and partial volume effects.…”

Computed tomography window affects kidney stones measurements

“…Other authors stressed the importance of standardization of making measurements on NCCT images (10). They demonstrated a larger variability for inter-reader (±1.3mm) than intra-reader (26). Narayan et al demonstrated that stone density measurements vary depending on window, plane and ROI technique.…”

“…Magnified bone window NCCT should be preferred for urinary stone evaluation due to better image quality for dense objects as it minimizes noise artifacts close to the stone limits (12, 25). In vitro study already demonstrated that soft tissue window overestimates stone size and bone window provides best accuracy (26). Clinically, it was shown that bone window allows a visual distinction between a stent and a stone (28, 29).…”

Comparison of ureteric stone size, on bone window versus standard soft-tissue window settings, on multi-detector non-contrast computed tomography

“…There is still significant controversy in size estimation using soft-tissue and bone windows. Argüelles Salido et al [4] whilst comparing actual surface size and bone window CT scan size when using the European Association of Urology formula or scanner software did not find a statistically significant difference. They also noted that measurements in the soft-tissue window tended to significantly overestimate the surface size, whilst the plain radiography underestimated it slightly but significantly.…”