RESUMEN
This study proposes an approach based on the gamma-ray transmission technique to accurately determine the thickness of material plates using a low-activity source. For this purpose, we have set up an experimental configuration without collimators for both source and detector. Besides, a Monte Carlo simulation model using MCNP6 code has been created with the same geometric parameters as the empirical one. The calibration curves of thickness measurement were constructed for various energies of the incident gamma rays in the range of 123-661.7 keV and two materials of aluminum and copper using Monte Carlo simulation data. The thickness of the material plate was determined by applying experimental data to a known calibration curve. For a given material and gamma energy, the measurable thickness range (MTR) was estimated by investigating the dependence of the expected relative error on the thickness of the material plate. The obtained results show that the approach is feasible with the relative deviation between the measured and reference thicknesses of mostly less than 2% and the relative uncertainty of less than 3%. Such an approach could suggest a practical and cost-effective evaluation tool for optimizing the configuration to achieve a given accuracy corresponding to each type of material.
RESUMEN
PURPOSE: Severe chordee with hypospadias may require repair by ventral corporoplasty with a free graft before urethroplasty. We report an 11 year experience with one-stage and two-stage hypospadias repair using dermal grafts. MATERIALS AND METHODS: From 12/1997 to 12/2008, 47 hypospadias with severe chordee were repaired using a ventral dermal graft to correct the chordee. Forty cases were repaired in two stages; the remaining seven patients had adequate preputial skin and were repaired in one stage. In 28 cases the neourethra was covered with both tunica vaginalis and penile dartos flap while 12 were covered only with penile dartos flap. Patients ranged from 12 to 152 months of age. Follow-up ranged from 6 months to 4 years. RESULTS: 28 patients with both tunica vaginalis and dartos flap had 7 urethral fistulas and 2 developed meatal stenosis. 12 patients with only penile dartos flap had 3 fistulas and 2 had meatal regression. The seven patients who underwent a one-stage repair had good results with a straight penis and no evidence of urethral fistula or urethral stenosis. CONCLUSIONS: Dermal graft can be performed in one or two stage hypospadias repair. Complication rates are similar to other standard repairs for proximal hypospadias.