title: In vitro MR imaging of renal stones with an ultra-short echo time magnetic resonance imaging sequence.
abstract: OBJECTIVE
  To characterize the magnetic resonance (MR) relaxation times (ie, T1 and T2 relaxation times) of a variety of kidney stone specimens using an ultra-short echo time (UTE) sequence and to correlate these values to their size and composition based on chemical analysis.
  
  
  METHODS
  This was an institutional review board-approved, Health Insurance Portability and Accountability Act-compliant study with waiver of informed consent. Between April 2009 and September 2009, stones from 36 patients underwent 1.5T MR imaging with two UTE pulse sequences to measure: 1) T2 relaxation times (repetition time [TR] = 1 second and multiple echo times [TEs] ranging from 0.1 ms up to 2 ms); 2) T1 relaxation times (TE = 0.1 ms and multiple TRs ranging from 500 ms to 2.5 seconds). A tube containing a solution of water and hydroxyapatite crystals near the stones served as reference standard. Results were compared to previous data obtained from experiments measuring the T1 and T2 of pure calcium oxalate and hydroxyapatite crystals suspended in water. Stones were submitted for chemical analysis. The stone size and composition was correlated to the relaxation time, and signal intensity.
  
  
  RESULTS
  The average stone size was 0.86 cm (range 0.1-3.3 cm). Twenty-one stones were visible by MR. The average size of MR-visible stones was 1.1 cm (range 0.15-3.3 cm) compared to 0.46 cm (range 0.1-0.9) for nonvisible stones. The mean T1 and T2 of MR-visible stones were 950 ms (range 138-3000 ms) and 3.12 ms (range 0.27-12 ms), respectively. The T1 (mean 1143, range 740-1583) and T1 (mean 8.31, range 4.6-12) values of calcium phosphate were longer than that for other stone compositions T1 (mean 953, range 138-3000) and T2 (mean 2.58, range 0.27-5.8; P < .05).
  
  
  CONCLUSIONS
  The T1- and T2-relaxation times of kidney stones are variable and depend on their composition and the size of the stones. UTE MR allows for visualization of renal stones in vitro.
authors.affiliation: Department of Radiology, Faculty of Medicine, Ain Shams University, Cairo, Egypt.
authors.forename: Aya
authors.initials: A
authors.lastname: Yassin
authors.forename: Ivan
authors.initials: I
authors.lastname: Pedrosa
authors.forename: Michael
authors.initials: M
authors.lastname: Kearney
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Genega
authors.forename: Neil M
authors.initials: NM
authors.lastname: Rofsky
authors.forename: Robert E
authors.initials: RE
authors.lastname: Lenkinski
mesh_terms: D002129:Calcium Oxalate / Q000032:analysis; D002130:Calcium Phosphates / Q000032:analysis; D017886:Durapatite / Q000032:analysis; D006801:Humans; D066298:In Vitro Techniques; D007669:Kidney Calculi / Q000737:chemistry / Q000175:diagnosis*; D017616:Magnesium Compounds / Q000032:analysis; D008279:Magnetic Resonance Imaging / Q000379:methods*; D010710:Phosphates / Q000032:analysis; D000069877:Struvite; D014527:Uric Acid / Q000032:analysis
chemical_list: D002130:Calcium Phosphates; D017616:Magnesium Compounds; D010710:Phosphates; D002129:Calcium Oxalate; D014527:Uric Acid; D017886:Durapatite; D000069877:Struvite