BACKGROUND AND OBJECTIVE: In radiobiology, the most important physical radiation quantity to predict the effect of IRRADIATION of a biological specimen is the absorbed dose to the tissue of interest. In this project an IRRADIATION set up was designed and verification of set up and dosimetry procedure was performed to deliver a precise X-ray dose to the small field of rat cervical SPINAL CORD.METHODS: AAPM-TG61 (American association & physician in medicine radiation therapy committee task group 61) protocol was used for dose measurement and we tailored a rat like phantom from polyethylene for dosimetry verification. The ionization chamber in this study was a farmer type and the X-ray generator was an orthovoltage Siemens machine working at 200 KVp potential. Dosimetry was done in air and phantom. An special jig was also built to fix the animals during IRRADIATION which could help the treatments to be reproducible. Simulation and portal films were obtained to verify the IRRADIATION field.FINDINGS: The average value of dose rate in specified geometries by measurement was 146.54 cGy/min (SD= 0.109). While the dose determined by calculation was 95.145 cGy/min (SD= 0.105), the comparison between these two methods shown a small discrepancy of 0.50% (p<0.001), which lies within the error limit of ± 5.3% as mentioned by ICRU.CONCLUSION: Using protocol of AAPM TG-61 can provide an accurate dosimetry with minimum ambiguity. Application of appropriate correction factors and protocols can increase the accuracy and decrease the IRRADIATION errors in radiobiological studies

Radiation causes serious damages in SPINAL CORD and few agents are used for protection. In this study, Considered neuro-radioprotective effect of melatonin on the cervical SPINAL CORD.32 male adult. Wistar albino rats weighing 200-250 g were used. They were divided into four groups of 6 animals consisted of control, melatonin (30 mg/kg per day), radiation (single Gamma dose of l0 Gy) and the group that received radiation plus melatonin. After 72 hours, all rats were sacrificed fbr histopathological and analysis of malondialdehyde, glutathione and protein biochemicals.Malondialdehyde and protein levels u'ere decreased after melatonin treatment while glutathione level, was Increased (p<0.005). Overall histopathological changes were markedly decreased after rnelatonin treatment in comparison to radiation group (p<0.05). ln conclusion melatonin may be useful in preventing the SPINAL CORD against radiation toxicity due to its Potential of free oxygen radical scavenging.

Effect of low-energy GaAlas laser IRRADIATION With wave length of 830 nm on histologic repair of compressional SPINAL CORD injury in rats, resulting in muscular paralysis, was tested Compressional injury was caused using Holtz method (putting 35g weight on the middle thorasic part of SPINAL CORD about 5 minutes).The animals were divided into treatment and control groups. The control group was maintained in exprimental condition for 14 days .The treatment group was also irradicted with 9 joules energy every day. In the day fifteenth after the injury, both groups were assessed histologically to evaluate the effect of laser IRRADIATION on SPINAL CORD injury.Results showed that the rate of angiogenesis and number of motor neurons were relatively higher in the treatment group in comparison with the control group.But presence of hemorrhage resulted from RBC accumulation in the location of injury, indicates that the injury has not been repaired in the control group.Regarding the mentioned above results, it seems that IRRADIATION of low-energy laser causes histologic repair in SPINAL CORD injury.