Visualization of Spatial Distribution of Spermatogenesis in Mouse Testes Using Creatine Chemical Exchange Saturation Transfer Imaging.

BACKGROUND When determining treatment strategies for male infertility, it is important to evaluate spermatogenesis and its spatial distribution in the testes. PURPOSE To investigate the usefulness of creatine chemical exchange saturation transfer (CrCEST) imaging for evaluating spermatogenesis and its spatial distribution. STUDY TYPE Prospective. ANIMAL MODEL C57BL/6 control mice (n = 5) and model mice of male infertility induced by whole testis X-ray irradiation (n = 11) or localized X-ray irradiation to lower regions of testes (n = 3). FIELD STRENGTH/SEQUENCE A 11.7-T vertical-bore magnetic resonance imaging (MRI)/segmented fast low-angle shot acquisition for CEST. ASSESSMENT The magnetization transfer ratio for the CrCEST effect (MTRCr* ) was calculated in each testis of the control mice and X-ray irradiation model mice at 10, 15, 20, and 30 days after irradiation. Correlation analysis was performed between MTRCr* and Johnsen's score, a histological score for spermatogenesis. In the localized X-ray irradiation model, regional MTRCr* and Johnsen's score were calculated for correlation analysis. STATISTICAL TESTS Unpaired t-test, one-way analysis of variance with Tukey's HSD test and Pearson's correlation analysis. A P value < 0.05 was considered statistically significant. RESULTS In the irradiation model, CrCEST imaging revealed a significant linear decrease of MTRCr* after irradiation (control, 8.7 ± 0.6; 10 days, 7.9 ± 0.8; 15 days, 6.5 ± 0.6; 20 days, 5.4 ± 1.0; 30 days, 4.4 ± 0.8). A significant linear correlation was found between MTRCr* and Johnsen's score (Pearson's correlation coefficient (r) = 0.79). In the localized irradiation model, CrCEST imaging visualized a significant regional decrease of MTRCr* in the unshielded region (shielded, 6.9 ± 0.7; unshielded, 4.9 ± 1.0), and a significant linear correlation was found between regional MTRCr* and Johnsen's score (r = 0.78). DATA CONCLUSION Testicular CrCEST effects correlated well with spermatogenesis. CrCEST imaging was useful for evaluating spermatogenesis and its spatial distribution. EVIDENCE LEVEL 2 TECHNICAL EFFICACY: Stage 2.