Recent technologic advances have markedly enhanced the clinical applications of computed tomography (CT). While the benefits of CT exceed the harmful effects of radiation exposure in patients, increasing radiation doses to the population have raised a compelling case for reduction of radiation exposure from CT. Strategies for radiation dose reduction are difficult to devise, however, because of a lack of guidelines regarding CT examination and scanning techniques. Various methods and strategies based on individual patient attributes and CT technology have been explored for dose optimization. It is the purpose of this review article to outline basic principles of CT radiation exposure and emphasize the need for CT radiation dose optimization based on modification of scanning parameters and application of recent technologic innovations.

Objective-To examine the association between body weight and measures of male reproductive potential. Design-Cross-sectional studySetting-Fertility clinic in an academic medical center.Patients-483 male partners of subfertile couples. Interventions-NoneMain outcome measures-Standard semen analysis, sperm DNA fragmentation and serum levels of reproductive hormones.Results-As expected, BMI was positively related to estradiol levels and inversely related to total testosterone and SHBG levels. There was also a strong inverse relation between BMI and inhibin B levels and a lower testosterone:LH ratio among men with a BMI ≥ 35kg/m 2 . BMI was unrelated to sperm concentration, motility or morphology. Ejaculate volume decreased steadily with increasing BMI levels. Further, men with BMI ≥ 35kg/m 2 had a lower total sperm count (concentration × volume) than normal weight men (Adjusted difference in the median [95% CI] = −86 × 10 6 sperm [−134, −37]). Sperm with high DNA damage were significantly more numerous in obese men than in normal weight men.Corresponding Author: Jorge E. Chavarro, MD, Department of Nutrition, Harvard School of Public Health, 665 Huntington Ave., Boston, MA 02115, Phone: 617-432-4584, Fax: 617-432-2435, jchavarr@hsph.harvard.edu. Capsule Body mass index was related to reproductive hormone levels and total sperm count but unrelated to sperm concentration, motility or morphology in a group of men attending a fertility clinic. Conclusions-These data suggest that despite major differences in reproductive hormone levels with increasing body weight, only extreme levels of obesity may negatively influence male reproductive potential. NIH Public Access

Introduction of slip-ring technology with subsequent development of single- and multi-detector row helical computed tomographic (CT) scanners have expanded the applications of CT, leading to a substantial increase in the number of CT examinations being performed. Owing to concerns about the resultant increase in associated radiation dose, many technical innovations have been introduced. One such innovation is automatic tube current modulation. The purpose of automatic tube current modulation is to maintain constant image quality regardless of patient attenuation characteristics, thus allowing radiation dose to patients to be reduced. This review discusses the principles, clinical use, and limitations of different automatic tube current modulation techniques.

Bisphenol A (BPA) impairs spermatogenesis in animals, but human studies are lacking. We measured urinary BPA concentrations, semen quality, and sperm DNA damage (comet assay) in 190 men recruited through an infertility clinic. BPA was detected in 89% of samples, with a median (interquartile range [IQR]) concentration of 1.3 (0.8 -2.5) ng/mL. Urinary BPA concentration was associated with slightly elevated, though not statistically significant, odds for below reference sperm concentration, motility, and morphology. When modeled as continuous dependent variables, an IQR increase in urinary BPA concentration was associated with declines in sperm concentration, motility, and morphology of 23% (95%CI -40%, -0.3%), 7.5% (-17%, +1.5%), and 13% (-26%, -0.1%), respectively, along with a 10% (0.03%, 19%) increase in sperm DNA damage measured as the percentage of DNA in comet tail. In conclusion, urinary BPA may be associated with declined semen quality and increased sperm DNA damage, but confirmatory studies are needed.