Quantification of skin dose increase and photon beam attenuation for a commercial couch top and breast board using dosimetric and Monte Carlo methods

Background: to study attenuation and increased skin dose for the iBEAM Standard couchtop, and attenuation of the BreastSTEP board, for an Elekta Compact 6 MV accelerator

Materials and Methods: couchtop attenuation were measured for the range of gantry angles 125degree-180degree and field sizes 5×5-20×8 cm2. H and N extension and the BreastSTEP attenuations measured in an 8×8 cm2 field. The couchtop effect on percentage depth-dose [PDD] measured by an EFD diode for field sizes 5×5- 20×20 cm2 and compared with that produced by a Co-60 beam passing through a 'tennis-racket' couch insert. A Monte Carlo [MC] model of the couchtop produced to provide more superficial PDDs. [PDDs that are more superficial]

Results: maximum couchtop attenuation [7.6%] measured for the 135° gantry and 5×5 cm2 field. Couch extension attenuation was 1.5% lower. Adding BreastSTEP increased attenuation by 2.4%. MC attenuation results agreed with measurements to within 0.2%. The couchtop removed the dose buildup effect almost completely and increased the PDD at 0.4 mm depth by 60.6%-74.6%. MC-calculated PDDs at the depth range of skin basal cell layer [0.1-0.4 mm] increased by 55.3%-63.2%. The couch insert in the Co-60 beam increased the dose at 0.4 mm depth by 18.1%. For the same dose prescription at 10 cm depth, the insert in the Co-60 beam produced a skin dose 49.7% lower than the couchtop at 6 MV

Conclusion: these results provide useful practical data on attenuation and skin dose increase applicable to many centers. The accelerator couchtop combination creates a greater skin dose increase than a tennis-racket insert on a Co-60 unit

Human amniotic membrane effect on colorectal anastomosis in dogs undergoing radiotherapy with/without diverting stoma: an experimental preliminary study

Background: Radiotherapy is an important factor which results in increase of anastomosis leakage. Diverting loop ileostomy has been usually performed after colorectal anastomosis with history of neo-adjuvant radiotherapy to decrease the chance of leakage. Considering this effect, we assessed the feasibility and outcome of human amniotic membrane in rectal anastomosis in dogs previously treated by high-dose radiotherapy

Materials and Methods: Twelve cross-breed male dogs with the age of 6-8 months and weighting 10-15 kg were randomly divided into four groups. Groups 1 and 2 received radiotherapy and 4 weeks later, single layer end to end anastomosis was performed for all the dogs; also, diverting loop ileostomy was placed in groups 1 and 3. Four weeks later, the anastomosis site was resected and sent for pathologic wound healing scoring. Data were analyzed by SPSS 16 software using Mann- Whitney test

Results: Two dogs [of group 1 and 2] died of peritonitis due to anastomosis leakage during the 2[nd] post operation week. There was no statistically significant difference in wound healing between the case and control groups [P-Value: 0.01]

Conclusion: HAM had a protective role in colorectal anastomosis after neo-adjuvant radiation in cases without loop diverting ileostomy. It can be concluded that HAM placement is a feasible technique instead of diverting loop ileostomy in cases with neo-adjuvant radiotherapy and also in the benign colorectal diseases with high risk anastomoses

Rectal wall dose estimation in intracavitary brachytherapy: a preliminary comparison of an in-house rectal wire versus ICRU 38 recommendations

In intracavitary brachytherapy for gynecological cancers, various techniques are used to locate the anterior rectal wall nearest to the sources but there is no consensus on the best method to do so. This study aimed to compare a technique used routinely in some centers that employs a wire marker to locate the position of the maximum rectal dose point, versus the method recommended by the ICRU Report 38. In a preliminary prospective study on 34 intracavitary insertions for patients with cervical or endometrial cancer, treated at our center based on the Manchester system, the dose distributions were obtained from a treatment planning system following the input of scanned orthogonal anteroposterior and lateral radiographs. For each case, an in-house marked wire was inserted in the rectal lumen and the doses were calculated on several points along the wire seen on the radiographs, to obtain the maximum dose. For the same insertions, the ICRU method was also applied by considering the rectal wall hot spot as a point 0.5 cm posterior to the posterior vaginal wall [visualized on the radiographs by vaginal packing material containing contrast medium]. Averaged over all insertions, mean rectal wall hot spot dose calculated using the positional information obtained by the wire technique was lower by 28.6% than that given by the ICRU method [P < 0.001]. Our initial results add evidence to the suggestion that the wire technique underestimates the rectal wall hot spot dose significantly compared to the ICRU method

[Designing of human cartilage tissue, by differentiation of adipose-derived stem cells with BMP-6 in alginate scaffold]

In the present study the effect of BMP-6 was investigated on chondrogenesis of adipose-derived stem cells. Mesenchymal stem cells derived from subcutaneous adipose tissue were cultured on alginate scaffold to induce chondrogenesis in experimental group, with chondrogenic medium having BMP-6 growth factor for 3weeks. In control group medium without BMP-6 was applied. The harvested constructs were examined with immunohistochemical and RT-PCR methods for assessment of cartilage-specific characteristics. The results of immunohistochemical method revealed the presence of typical cartilage extracellular matrix components such as type II collagen and aggrecan in constructs induced by BMP-6 growth factor on alginate scaffold. In addition evaluation of the results of RT-PCR analysis confirmed the expression of cartilage- specific genes, such as type II collagen and aggrecan, in the differentiated cells under the influence of growth factor BMP-6. It can be concluded that BMP-6 promotes chondrogenesis of ADSC in 3-D and adipose-derived stem cells could be used for cartilage tissue engineering

in - vitro study on the effect of Iranian soft drinks on enamel microhardness of primary teeth

Diet is the most important etiologic factor in dental erosion. Erosion of dietary origin in children is frequently related to carbonated drinks and acidic foods. The aim of this study was to evaluate the effects of some acidic soft drinks on enamel micro-hardness of primary teeth. This interventional in vitro study was performed on 40 healthy deciduous teeth. Enamel blocks were prepared and were polished on their external surfaces using water and sand paper. The baseline hardness was measured using Vickers microhardness measuring apparatus. The enamel blocks were then immersed in 20[cc] Coca Cola, Zam Zam, Pepsi and Ab-Ali yoghurt-drink for 5 and their microhardness was assessed. The data were analyzed using co-variance and paired sample t-tests. The baseline hardness in primary teeth, was 378.4 +/- 31.65 [kg/mm[2]] for Coca Cola, 373.57 +/- 30.31 [kg/mm[2]] for Zam Zam, 378.38 +/- 21.92 [kg/mm[2]] for Pepsi and 385.43 +/- 34.79 [kg/mm[2]] for Ab-Ali yoghurt-drink, before being placed in the experimental soft drinks, After immersion [second hardness], these values decreased to 333.02 +/- 32.15 [kg/mm[2]], 339.65 +/- 20.91 [kg/mm[2]], 342.27 +/- 28.01 [kg/mm[2]] and 341.46 +/- 32.34 [kg/mm[2]] for Coca Cola, Zam Zam, Pepsi and Ab-Ali yoghurt soft drinks, respectively. The reduction in microhardness was statistically significant for each of the tested soft drinks but a statistically significant difference was not observed between the study groups. The intake of soft drinks such as Coca Cola, Zam Zam, Pepsi and Ab-Ali yoghurt-drink can reduce enamel microhardness in primary teeth