Dual Energy CT – Renal Stone Composition
The following question has been sent by Dr. Ravi Mahal, Radiologist, Boca Radiology Group, USA:
We have been using the DECT for Urinary stone composition for the past 6 months. Recently I had a case where a patient had 2 stones of different compositions; a right uric acid stone and a left CaOx stone. The composition was \’confirmed\’ with HU Overlay values using the syNgro software. Was wondering if this is even physiologically possible? Have you run into patients with 2 different stone compositions?
Savvas Nicolaou, MD, University of British Columbia, Canada:
Yes it is possible to have stones with different composition.
We have seen the same stone have a combination of calcium and uric acid that was confirmed pathologically
thank you
Dr Savvas Nicolaou
Keywords:
is there any documentation regarding the analysis of gallstones with dual energy?
Regarding DECT in the characterization of gallstones, there is not much work out there. There is some preliminary work and I have included an abstract from the RSNA 2006 please see below, hope this answers your question.
SESSION: Gastrointestinal (Dual Energy, Innovations)
Dual-source CT Characterization of Gallstones Using a Dual-Energy Analysis
DATE: Wednesday, November 29 2006
PURPOSE
Standard treatment for symptomatic and non-symptomatic cholecystolithiasis is cholecystectomy. Non-invasive approaches such as oral litholysis are mainly limited to patient with pure cholesterol stones, which often is difficult to assess when using either ultrasound or conventional CT. This study examines the possibility of a novel clinically available dual-source CT using two tubes mounted in the gantry applying dual energy technique to non-invasively characterize gallstones in vitro (DECT).
METHOD AND MATERIALS
Pathology provided 40 randomly selected gallstones excised during cholecystectomy. They were individually embedded in ultrasound gel. Scanner settings were: 2 x 64 slices per rotation, collimation 0.6 mm, tube 1: 80 kV, 175 mAs and tube 2: 140 kV, 170 mAs. Pitch 1.4, reconstruction slice with 1.0 mm, recon increment 1.0 mm. For comparison scans were repeated using the same scanner setting using monoenergetic scans at either 80 kV as well as 140 kV. Dual energy analysis was performed image based. Gold standard was pathological classification.
RESULTS
Pathological analysis revealed 7 calcified stones, 15 pigmented stones, 7 pure cholesterol stones 6 mixed cholesterol stones and 5 mixed pigmented stones. Dual energy analysis was able to distinctively differentiate between all subtypes. Moreover DECT was able to differentiate between two different subtypes of cholesterol. One subgroup had 4 cholesterol stones that were not visible in conventional 140kV monoenergetic CT and had a lesser density. Pathology differentiated these types by surface analysis. The non-visible group had a smooth surface whereas the other group had a structured surface. This other group was visible at both energy levels.
CONCLUSION
These primary results indicate that DECT permits subtle characterization of gallstones in vitro using a clinically available dual source CT. It also allows for detection of primarily non radio opaque cholesterol stones at 140kV, an energy level often used for obese patients.
CLINICAL RELEVANCE/APPLICATION
Reliable detection and characterization of cholesterol stones could permit better treatment decision for obese patients at elevated risk during surgery, whether to undergo oral litholysis or surgery.