Quarter regular dose non-enhanced CT for urinary stone: added value of adaptive statistical iterative reconstruction

Diagnostic performance of advanced modeled iterative reconstruction applied images for detecting urinary stones on submillisievert low-dose computed tomography

Background Repeated computed tomography (CT) scans may be an issue in young adults with urinary stones. Therefore, it is important to know how far the dose can be reduced while maintaining the diagnostic performance. Purpose To generate a hypothesis that it is feasible to decrease the radiation dose to a sub-millisievert (mSv) level with the addition of advanced modeled iterative reconstruction (ADMIRE) while maintaining the sensitivity to standard-dose CT (SDCT) for the detection of urinary stones. Material and Methods Ninety-two consecutive patients with urinary stones underwent non-enhanced CT that consisted of standard (120 kVp, 200 mAs) and lose-dose (LDCT) (80 kVp, 60 mAs). The LDCT images were reconstructed separately with five different strengths of ADMIRE (hereafter, S1-S5) and filtered back projection (FBP). Two blinded radiologists independently recorded a number of urinary stones in the six LDCT datasets and SDCT. The sensitivity of each set for detecting urinary stones was compared using the McNemar test. Results A total of 240 urinary stones were analyzed. The sensitivities of the six LDCT datasets showed no difference (FBP, S1-S5, for reader 1: 78%, 79%, 79%, 80%, 80%, and 80%; for reader 2: 64%, 63%, 64%, 64%, 65%, and 66%, P > 0.05, respectively), which were lower than those of SDCT for both readers (reader 1: 88%; reader 2: 81%, P < 0.0001, respectively). Conclusion Despite the addition of ADMIRE, it may not be feasible to decrease the radiation dose to a sub-mSv level while maintaining the sensitivity to SDCT for the detection of urinary stones.

Imaging for Urinary Stones: Update in 2015

CONTEXT

Imaging is essential for the diagnosis and the clinical decision-making process of patients with urinary stones.

OBJECTIVE

To assess the benefits and limitations of various imaging techniques by specifically focusing on different phases of stone patients' management.

EVIDENCE ACQUISITION

PubMed and Web of Science databases were used to identify studies published in the last 10 yr on this argument. Search terms included 'urolithiasis', nephrolithiasis', or 'urinary stones' in combination (AND) with the terms 'imaging', 'computer tomography', 'ultrasonography', 'intravenous pyelogram', or 'radiation exposure'. Study selection was based on an independent peer-review process of all the authors after the structured data search.

EVIDENCE SYNTHESIS

Noncontrast-enhanced computer tomography (CT) provides the highest value of diagnostic accuracy for urinary stones. Stone composition can be specifically assessed through the use of dual-energy CT. When information about the anatomy of the renal collecting system is required or alternative pathologies are suspected, CT with contrast injection is recommended. Low-dose protocols allowed a drastic reduction of the effective dose administered to the patient, thus limiting the biological risk due to ionising radiations. Other strategies to contain the radiation exposure include the dual-split bolus dual energy CT and the adaptive statistical image reconstruction. Abdomen ultrasound may be a valid alternative as an initial approach since it does not change the outcome of patients compared with CT, and should be the imaging of choice in children and pregnant women.

CONCLUSIONS

Noncontrast-enhanced CT is the most accurate imaging technique to identify urinary stones. Abdomen ultrasound seems to be a valid alternative in the initial evaluation of urinary colic. New low-dose protocols and strategies have been developed to contain radiation exposure, which is a major issue especially in specific circumstances.

PATIENT SUMMARY

Noncontrast-enhanced computer tomography has been increasingly used for the diagnosis and management of urinary stones. Low-dose protocols as well as alternative imaging should be considered by clinicians in specific circumstances to minimise radiation exposure.