Abdominal Radiology

, Volume 44, Issue 1, pp 227–233 | Cite as

Ultra-low-dose limited renal CT for volumetric stone surveillance: advantages over standard unenhanced CT

  • Virginia B. PlanzEmail author
  • Natasza M. Posielski
  • Meghan G. Lubner
  • Ke Li
  • Guang-Hong Chen
  • Stephen Y. Nakada
  • Perry J. Pickhardt



To describe and validate a novel CT approach using volumetric analysis for renal stone surveillance.

Materials and methods

This prospective trial consisted of a standard low-dose non-contrast CT (SLD) of the abdomen and pelvis, immediately followed by an ultra-low-dose non-contrast CT (ULD) with reconstruction limited to the kidneys. A novel dedicated software tool was applied that automates stone volume, density, and maximum linear size. Manual linear stone size was measured by a radiology fellow and urology resident for comparison. CT dose and clinical charges were considered.


Twenty-eight stones in 16 patients were analyzed. Mean effective dose of ULD CT was 0.57 mSv, an average 92% lower than the SLD CT dose. For SLD, mean size ± SD (range) (mm) was 7.9 ± 6.2 (2.6–30.5) for Reader 1, 7.3 ± 6 (2.4–30.7) for Reader 2, and 9.3 ± 6.4 (3.7–33.1) for the automated software. For ULD, mean size ± SD (range) (mm) was 7.3 ± 6 (2.5–30.5) for Reader 1, 7.2 ± 6.1 (2.1–30.7) for Reader 2, and 9.1 ± 6.4 (4.2–32.8) for the automated software. Automated stone diameters were larger than manual diameters for 27/28 stones (mean difference, 23%); difference was ≥ 2 mm in 30%. Average variability between manual measurements was 8.6% (SLD) and 7.8% (ULD), but was 0% for the automated technique. Our institutional charge for ULD renal CT is slightly less than renal US, and > 4× less than SLD CT. The Medicare global fee for the ULD renal CT is less than the SLD CT of the abdomen and pelvis.


This focused stone surveillance CT protocol is lower cost and lower dose compared to the standard CT approach. Automated assessment of stone burden provides improved reproducibility over manual linear measurement and offers the advantages of 3D measurements and volumetry. We now offer and perform this protocol in routine clinical practice for stone surveillance.


Computed tomography Urolithiasis Ultra-low-dose Volumetry 


Compliance with ethical standards


This study was funded by NIH grant R01 CA169331-01.

Conflict of interest

Pickhardt is co-founder of VirtuoCTC; consultant for Bracco and Check-Cap; and shareholder in Elucent, SHINE, and Cellectar. Lubner receives grant funding from Philips and Ethicon. Nakada is a consultant for Boston Scientific. Planz, Posielski, Li, and Chen declare that they have no conflict of interest.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed consent

Informed consent was obtained from all individual participants included in the study.


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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  • Virginia B. Planz
    • 1
    Email author
  • Natasza M. Posielski
    • 2
  • Meghan G. Lubner
    • 1
  • Ke Li
    • 3
  • Guang-Hong Chen
    • 3
  • Stephen Y. Nakada
    • 2
  • Perry J. Pickhardt
    • 1
  1. 1.Department of RadiologyUniversity of Wisconsin School of Medicine and Public HealthMadisonUSA
  2. 2.Department of UrologyUniversity of Wisconsin School of Medicine and Public HealthMadisonUSA
  3. 3.Department of Medical PhysicsUniversity of Wisconsin School of Medicine and Public HealthMadisonUSA

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