Type:
Educational Exhibit
Keywords:
Not applicable, Calcifications / Calculi, Surgery, Lithotripsy, CT, Urinary Tract / Bladder, Kidney, Genitourinary
Authors:
A. Kanwar, S. Mehra; New Delhi/IN
DOI:
10.26044/ecr2020/C-10892
Background
Urolithiasis is a common disease worldwide and affects various population groups, irrespective of race or geographic boundaries.In the past few decades, there has been an increasing incidence of urinary stone disease both in developed and developing nations due to changes in life style.[1] Appropriate management of renal stones is important as it can lead to complications such as sepsis, chronic kidney disease leading to renal failure.
DECT improves the characterization of renal stone by giving stone composition in addition to their basic identification, thereby tailoring treatment options to individual patients’ needs.
DECT involves imaging at two distinctly different energies, one high and one low e.g. 140 and 80 kVp respectively to obtain additional information regarding tissue composition using the concept of photoelectric effect. Energy of incident photon is absorbed by matter which causes an electron to be emitted from the innermost shell of atom i.e. K-shell. Its place is then filled by an electron from the next higher shell, which emits an X-rays in the process called as photoelectric effect. The binding energyof K-shell determines the probability of occurrence of photoelectric effect. As energy of the incident photon increases and approaches the K-shell binding energy the effect is more prominent. The K-shell binding energy is different for various elements and rises with higher atomic numbers. A sudden increase of attenuation, termed “K-edge,” is observed as energy of incident photon reaches just above the K-shell binding energy due to increased photoelectric effect. [2]
DECT scanners with the help of software utilize this concept to create attenuation profiles at higher and lower energy levels and calculate dual energy ratios for renal stones to know their composition.Fig. 1 Software assigns different colours to different materials on DECT. Fig. 2 and Fig. 3
Knowledge of the composition of urinary tract stones is a fundamental part of the preoperative patient evaluation, influences treatment plans and prevention of recurrence. [3] These parameters are helpful in not only planning an appropriate management for patient but also in predicting the success of various procedures like extracorporeal shock wave lithotripsy (ESWL), flexible ureterorenoscopy, or percutaneous nephrolithotomy (PCNL).Systemic and familial metabolic diseases can be suspected in patients with certain stone compositions, moreover specific dietary measures to reduce the risk of recurrence can be offered if the stone composition is known.