Production of a datolite-based heavy concrete for shielding nuclear reactors and megavoltage radiotherapy rooms

Biological shielding of nuclear reactors has always been a great concern and decreasing the complexity and expense of these installations is of great interest. In this study, we used datolite and galena [DaGa] minerals for production of a high performance heavy concrete. Datolite and galena minerals which can be found in many parts of Iran were used in the concrete mix design. To measure the gamma radiation attenuation of the DaGa concrete samples, they were exposed to both narrow and wide beams of gamma rays emitted from a cobalt-60 radiotherapy unit. An Am-Be neutron source was used for assessing the shielding properties of the samples against neutrons. To test the compression strengths, both types of concrete mixes [DaGa and ordinary concrete] were investigated. The concrete samples had a density of 4420-4650 kg/m[3] compared to that of ordinary concrete [2300-2500 kg/m[3]] or barite high density concrete [up to 3500 kg/m[3]]. The measured half value layer thickness of the DaGa concrete samples for cobalt-60 gamma rays was much less than that of ordinary concrete [2.56 cm compared to 6.0 cm]. Furthermore, the galena concrete samples had a significantly higher compressive strength as well as 20% more neutron absorption. The DaGa concrete samples showed good shielding/ engineering properties in comparison with other reported samples made, using high-density materials other than depleted uranium. It is also more economic than the high-density concretes. DaGa concrete may be a suitable option for shielding nuclear reactors and megavoltage radiotherapy rooms

Standard calibration of ionization chambers used in radiation therapy dosimetry and evaluation of uncertainties

Absolute dosimetry of external beam radiotherapy is carried out by the use of ionization chambers. These chambers must be calibrated at a standard dosimetry laboratory before any use in clinical dosimetry. The secondary standard dosimetry laboratory of Iran [SSDL] has the duty of calibrating the ionization chambers used in radiotherapy centers in Iran. The present work has described traceability of SSDL radiation measurement standards to relevant international standards, and calibration of therapy level ionization chambers in terms of air kerma and absorbed dose to water against [60]Co gamma radiation, as well as uncertainty evaluation of calibration coefficients. The expanded uncertainties in the determination of air kerma and absorbed dose to water are estimated to be 2% and 2.3% at approximately 95% confidence level, respectively. In order to maintain the requirement of +/- 5% accuracy in the dose delivery, the combined standard uncertainty of the other factors in the dose delivery; i.e., dose measurement set-up, dose calculations, treatment planning, patient set-up, etc, should be less than 2.3%

CT cavernosography: a new method for evaluating venous incompetence in impotent patients

Cavernosography is traditionally recognized as an imaging modality for evaluation of venous leakage in impotent men. We introduce CT cavernosography as a novel method for demonstrating leaking veins. Sixty-seven patients diagnosed as venous incompetence by Doppler study, and eight normal subjects were enrolled into the study. After intracavernosal injection of papaverine, normal saline was injected into the corpora cavernosa and the injection rate was gradually increased and the penis was observed to obtain the injection rate causing erection. Then contrast media was injected into the corpus cavernosum with obtained injection rate followed by CT scan of the penis and pelvis. In the first group, 63 patients [94%] had venous leakage by CT cavernosography. In this group, full erection was observed at the rate of 36 ml/min of saline injection in three patients and 24 ml/min in one patient. In 46 patients [73%], erection was induced with saline injection at the rates of 48-120 ml/min, and in 17 patients [27%] no full erection was demonstrated even at the injection rate of 120 ml/min. In the 2nd group we observed full erection after saline injection at the rates of 36 ml/min and 24 ml/min in five and three patients, respectively. Beside the capability of CT source images in precise visualization of all leaking veins without superimposition of bony structures, different techniques of two- or three- dimensional reformation enable us to demonstrate the anatomy of the penis and the leaking veins elegantly for further surgical planning

Implantation of bladder cancer into the abdominal wall; a case report

Implantation of high grade and invasive bladder carcinoma into the abdominal wall Is not common and can occur as side effects of urinary bladder interventions and surgical procedures, including perforation of bladder wall during transurethral resection of the tumor. Herein, we present a case of implantation of bladder transitional cell carcinoma into abdominal wall into an incisional hernia of a previous small bowel operation; three years after the bladder tumor had been diagnosed and treated. In evaluating any mass lesion in the abdominal wall, it is important to consider the possibility of bladder tumor implantation