This article provides a brief review of aspects of biophysical modelling in radiation biology. A major concern of radiation biology in the past half century has been the quantification of the health hazards of ionising radiations of different qualities and extrapolation of human cancer risks at high dose and dose rates to low dose and dose rates (UNSCEAR 1993). In the past decade with the accelerated progress in molecular biology techniques and advances in theoretical methods attention has become more focused on mechanistic studies and interpretation of effects of ionising radiation. To this end, track structure has provided a theoretical tool to investigate those parameters of ionising radiation that predominantly determine the nature and magnitude of the final effect (Vogelstein and Kinzler 1998).

Sperm dna contributes half of the offspring genomic material and any abnormalities of chromatin/dna can lead to failures in reproductive process. Despite association between dna damage and male infertility, there is a detectable level of dna damage in spermatozoa of fertile men. The causes of these anomalies, much like those of male infertility, are multifactorial and may be attributed to intra or extra-testicular factors. The exact mechanisms by which chromatin abnormalities/dna damage arise in human spermatozoa are not exactly understood, but four main theories have been proposed at molecular level, namely defective sperm chromatin packaging, apoptosis, oxidative stress and genetic lesions. A variety of several etiological factors including intra-testicular, post-testicular, and external factors, have been correlated with increased levels of human sperm dna damage, and in turn, can affect the potential of male fertility. Varicocele, cigarette smoking, exposure to xenobiotics, leucocytes and infections, thermal stresses, different kind of sperm preparation protocols, cancer, chemotherapy and radiotherapy, spinal cord injury, hormonal insufficiency particularly in the axis of pituitary-testis, ethanol consumption, environmental Pollution and aging are recently known as main etiologies for sperm chromatin and dna damages influencing male fertility.In the cases of inadequate repair capacity of oocyte, fertilization failure, early embryogenesis abnormalities, implantation failure and finally pregnancy loss will be seen. Six chief strategies regarding the problem of raised sperm dna damage have been recommended recently: Using surgically-retrieved testicular spermatozoa instead of ejaculated ones, using ejaculated spermatozoa after at least two months of oral antioxidant therapy, micro-injection (ICSI) with spermatozoa selected with the use of a high-magnification optical system (high-magnification ICSI), suitable preparation of the semen samples, in-vitro culture conditions and finally the selected type of ART programs.