Proton beam dosimetry by CR-39 track-etched detector

High and intermediate energy protons are not able to form a track in a solid state nuclear track detector [SSNTD] directly. However, such tracks can be formed through secondary particles created during primary radiation nuclear reactions in a SSNTD. The protons with primary energies of 9.6 and 30 MeV available at the cyclotron accelerator with corresponding low LETs of 5.87 and 2.40 keV/ micro m were taken into consideration. The nuclear tracks etch rate ratio V in CR-39 were measured and transformed into LET spectra for the absorbed and equivalent dose measurements. The optimum etching condition of 6 N NaOH solutions at 65 to 70 ?C over a 6-hour period for the CR-39 were found initially. The corresponding bulk etching rate reached a steady rate of about 0.62 to 1.3 um/h after nine hours for an optimum etching condition. Although the LET was low, but the energy range seemed sufficient enough to create secondary particles with much higher LET through the nuclear reactions in CR-39. The relative absorbed dose contribution of the created secondary particles to the primary particles for the 9.6 and 30 MeV protons in CR-39 at 1 Gy entrance dose were 7.5 and 29.6%, respectively. The contribution of the secondary particle increased relatively with the proton energy decrease. This phenomenon could modify the characteristics of the energy transfer process due to secondary particles when such particles are used for radiobiological studies and/or for radiotherapy

[Postoperative analgesia after laminectomy with dexamethasone: intravenous versus epidural injection]

Background: according to sever pain of laminectomy operation, this double blind clinical trial study was done for accompany postoperative analgrsia with preoperative IV dexamethasone and postoperative epidural dexamethasone in patients

Materials and methods: two 45 patients groups that candidated for elective laminectomy under general anesthesia, according to double blind clinical trial study were randomly divided into two groups, one group received preoperative IV dexamethasone and second group received postoperative epidural dexamethasone and then data were gathered, analyzed with Chi - square and Mann-Whitney U and T-Student tests by spss software

Results: two groups were similar with demographic parameres as age, weigh and sex[p>0.05]. In the postoperative epidural dexamethasone severity of postoperative pain was lower [p<0.05]. The time of free pain period in the postoperative epidural dexamethasone group was longer [p<0.05]

Conclusion: usage of postoperative epidural dexamethasone in laminectomy operation can decrease of severity of pain and cause longer free pain period in patients

Preparation, distribution, stability and tumor imaging properties of [62 Zn] bleomycin complex in normal and tumor - bearing mice

Bleomycin [BLM] has been labeled with radioisotopes and widely used in therapy and diagnosis. In this study BLM was labeled with [62Zn] zinc chloride for oncologic PET studies. The complex was obtained at the pH=2 in normal saline at 90°C in 60 min. Radio-TLC showed an overall radiochemical yield of 95-97% [radiochemical purity > 97%]. Stability of complex was checked in vitro in mice and human plasma/urine. Preliminary in vivo studies performed to determine complex stability and distribution of [62Zn] BLM in normal and fibrosarcoma-bearing mice. [62Zn] BLM accumulated significantly in induced fibrosarcoma tumors in mice according to bio-distribution/imaging studies. [62Zn] BLM can be used in PET oncology studies due to its suitable physico-chemical properties as a diagnostic complex in vitro and in vivo. Further studies should be performed for evaluation of the complex behavior in higher animals