Objective
To evaluate the use of automated volumetric assessment for stone surveillance and
compare the results with manual linear measurement.
Methods
We retrospectively reviewed patients seen in our stone clinic who had undergone 2
noncontrast computed tomography (NCCT) scans without stone intervention during the
interval between scans. Thirty patients met our inclusion criteria and underwent longitudinal
assessment for urolithiasis via NCCT (mean interval 583.2 days, range 122-2030). Fifty-two
discrete calculi were analyzed. Three board certified radiologists measured maximal
linear stone size in the axial plane using electronic calipers on soft tissue (ST)
and bone windows (BWs). Automated stone volume was also obtained by each reader using
a dedicated prototype software tool for stone evaluation.
Results
Mean stone linear size and volume was 4.9 ± 2.8 mm (ST), 4.5 ± 2.6 mm (BW), and 116.2
± 194.6 mm3 (window independent), respectively. Mean interobserver variability for linear size
measurement was 16.4 ± 10.5% (ST) and 20.3 ± 13.8% (BW). Interobserver variability
for volumetric measurement was 0%. Of the 52 persistent stones, the mean percent change
in linear stone size between CT studies was 39.3 ± 46.7% (ST) and 42.9 ± 53.1% (BW)
growth, compared with 171.4 ± 320.1% (window independent) growth for automated volume
measurement over a mean of 583.2 days. However, discordant results for increased vs
decreased interval size was seen between linear and volumetric assessment in 19/52
stones (36.5%).
Conclusion
Automated volumetric measurement of renal calculi via NCCT is independent of specific
reader and window settings. Volumetric assessment amplifies smaller linear changes
over time, whereas as much as one third of cases show linear-volume measurement discordance.
Volumetric assessment is therefore preferable, particularly for longitudinal surveillance
of renal calculi.
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Article info
Publication history
Published online: May 11, 2012
Accepted:
March 13,
2012
Received:
February 1,
2012
Footnotes
Financial Disclosure: The authors declare that they have no relevant financial interests.
Identification
Copyright
© 2012 Elsevier Inc. Published by Elsevier Inc. All rights reserved.
