Utilidad de la resonancia magnética testicular con espectroscopía en el análisis cuantitativo de la infertilidad

Resumo

PURPOSE: To determine the role of MRI and MR spectroscopy (MRSI) in the diagnosis of infertility. To stablish normal values of the metabolites involved in the spermatogenesis (choline, creatine, and lipids) and to quantify the infertility and describe their causes by combining these values. MATERIAL AND METHODS: This study included 27 consecutive patients attending the urologist 24 with fertility problems and 3 healthy patients. A total of 50 testes were evaluated at 1.5T magnetic resonance. Standard MRI examination and spectroscopy were performed. The variables: testicular volume measured, using the empiric formula of Lambert and by the voxel-count method, the presence of testicular pathology on MRI, infertility, values of metabolites detected by spectroscopy: choline, creatine, lipids and choline/lipids ratio were analyzed. All parameters were expressed as mean±standard deviation. Predictive capacity of different variables has been evaluated from the estimated areas under the ROC (Receiver Operating Characteristic) curves. RESULTS: The mean testicular volume measured by the empiric formula of Lambert was (25.3 ±9.2 cm3) cm3 and (18.1 ±7.6 cm3) by the “voxel-count method”. Lambert´s Formula calculated values systematically overestimated the volume compared with the “voxel-count method”. Testicular volume led us to discriminate between healthy and pathological testes with a sensitivity and specificity of 72.2% with a cut-off point of 16.4 cm3 for “voxel-count method” and 71.5 with Lambert´s formula with a cut-off point of 22.5 cm3. Regarding spectroscopy detected metabolites, mean values of choline, lipids and creatine were respectively (0.91 ±0.62), (1.47 ±1.42) y (0.40 ± 0.27). Meanwhile (0.80 ±0.5) value for choline/lipids ratio. There was a statistically significant relationship between choline value and testicular volume (p=0.001). Mean values of choline for pretesticular and testicular infertility were (0.09 ±0.001) and (0.60 ±0.54) respectively and for postesticular causes: (1,16 ±0,41). Choline and choline / lipids ratio were able to discriminate between healthy and diseased testes and presence/absence of infertility in patients. The area under ROC curves for choline and choline / lipids ratio was 0.9 and 0.83 respectively when presence of testicular pathology was analyzed by MRI. For the variable “infertility”, the area under the curve was 0.763 for choline and 0.70 for choline / lipids ratio. Creatine and lipids values have not been sufficient to discriminate between presence/absence of infertility or testicular pathology on MRI. In conclusion, values of choline bellow 0.65 can depict testicular pathology with a sensibility and specificity of 80 % and values of choline bellow 1.17 can detect infertility patients with a sensibility and specificity of 75%. CONCLUSIONS: Magnetic resonance spectroscopic technique allows us to identify the diseases and risk factors for male infertility or those that contribute to it, allowing a quantification of spermatogenic activity. Choline values discriminate with high sensitivity and specificity both, presence of infertility and testicular pathology. Due to the differences obtained in the mean values of choline, we can obtain information about infertility classification as pre-testicular, testicular or post-testicular. Presence of different choline peaks between obstructive and non-obstructive azoespermias, avoid unnecessary biopsies. Also, we can build maps of metabolic activity (maps of choline) to identify the localization of highest spermatogenic activity and perform targeted biopsy.