effect of delivering compensating doses on the survival of F10B16 melanoma and 4T1 breast adenocarcinoma treated with prolonged radiation delivery time

Increasing the complexity in modern radiotherapy techniques have increased the delivery time lowering consequently the treatment efficacy. Through simulating the delivery time delay encountered in such techniques, its' effect on two cancer cell lines and the compensating doses given to prevent such effect was investigated. F10B16 and 4T1 cancer cell lines were exposed to simulated clinical fractionated radiotherapy procedures commonly used in complex techniques. The survival rate of the cells exposed to 2, 4, and 6 Gy of ionizing radiation with two equal subfractions given at various time intervals between the fractions [0.25-4 hours] were determined using the MTT assay. Then, relevant compensating doses were calculated and their efficacy in counterbalancing the time delay was assessed. The cells' survival was increased with prolonged treatment times in the fractionated groups being more significant at the lower time intervals [up to 2 hours] and for the higher radiosensitive cells [4T1]. Giving the compensated doses decreased the survival of the cells. Delivering appropriate compensating doses to the prolonged fractionated groups can counterbalance the effect of time delays encountered in complex radiotherapy techniques

Determination of organ doses in radioiodine therapy using medical internal radiation dosimetry [MIRD] method

Radioiodine therapy has proven to be an effective method in the treatment of patients with differentiated thyroid carcinoma after thyroidectomy. The scope of this study is to describe a method to obtain the dose of organs using medical internal radiation dosimetry [MIRD] method. At the end, the results of MIRD calculations were compared with thermoluminescent dosimeter [TLD-100]. The study was performed on 27 patients using TLD for thyroid, sternum and cervical vertebra. There were 5 TLDs for each organ which they were taken after 4, 8, 12, 20 and 24 hr. To calculate the amount of activity in the thyroid a head and neck phantom with a source of 10 mCi of 131I was used. A head and neck phantom was used to determine the absorbed dose. A source of 10 mCi of [131]I was putted on phantom. Several TLDs were placed on the surface of thyroid on phantom for 24 hr and then compared with the dose of phantom and patients followed by calculation of the activity in patient's thyroid. Finally, MIRD formula was used to calculate absorbed dose in cervical vertebra and sternum. The average of measurements of TLDs on phantom for 10 mCi of iodine was 33.3 cGy. The absorbed activity in thyroid in three groups for 100, 150 and 175 mCi administered 131I were 94.9, 104.6 and 108.8 mCi cumulated activity in 24 hrs. The absorbed dose obtained by MIRD calculations was found to be 419.9, 463.2, and 481.5 for thyroid, 288.9, 252.4 and 252.4 for sternum and 288.9, 252.4 and 252.4 for cervical vertebra. The results of MIRD method was similar to the results obtained experimentally. It was shown that 75% of absorbed dose calculated by the MIRD method is detectable by the TLD method

Shear bond strength of a veneering resin to a Ni-Cr alloy using two different surface treatment methods

A strong and stable bond between veneering materials and metal framework considerably promotes the aesthetic appearance and clinical longevity of a resin type restoration. Various adhesive metal primers have also been studied to enhance the bond strength of the composite resins to different metal surfaces. The purpose of the present study was to evaluate the shear bond strength of one laboratory composite resin bonded to a Ni-Cr alloy by means of two different methods. In this study, 24 wax disks were cast and divided into two equal groups. In the first group, a metal primer was applied to the casting surface, while an opaque porcelain material was used for the second group. After application of the veneering composite resin to the treated surfaces, the specimens were stored in a 37°C water bath for 15 days. At the end of this period, all the specimens were subjected to 1200 thermal cycles [5°C and 55 °C] and then tested for shear strength in a universal testing machine at a crosshead speed of 0.5 mm/min. Fractured specimens were examined, using a scanning electron microscope. The opaque porcelain group demonstrated higher bond strength [17.55 +/- 3.33 Mpa] in comparison to the metal primed surface [15 +/- 4.25 Mpa]. However, no statistically significant difference was found between the specimens treated with metal primer and those treated with opaque porcelain. The two alloy surface treatments exhibited mixed failures, however. While the nature of failure for opaque porcelain was predominately cohesive, the failure for the metal primed group was adhesive. It can be concluded that both techniques have potential to significantly improve resin-alloy shear bond strength

Determination of absorbed dose of organs [thyroid, sternum, cervical vertebra] in thyroid cancer patients following radioiodine therapy

In patients with thyroid carcinoma, radiation absorbed doses of the thyroid and surrounding tissues is important to weigh risk and benefit considerations. In nuclear medicine, the accuracy of absorbed dose of internally distributed radionuclides is estimated by different methods such as MIRD and direct method using TLD. The aim of this study is using TLD and a phantom to determine the amount of cumulated activity in thyroid and surrounding tissues. Thermoluminescent dosimeter [TLD] measurements were performed on 27 patients on the skin over the thyroid, sternum and cervical vertebra. There were 5 TLDs for each organ which they were taken after 4, 8, 12, 20 and 24 hr. To calculate the amount of activity in the thyroid a head and neck phantom with a source of 10 mCi of [131] I was used. Several TLDs were placed putted on the surface of thyroid on phantom [similar to patients] for 24 hr and then compared the dose of phantom and patients followed by calculation of the activity in patient's thyroid. TLD measurements showed cumulated radiation absorbed doses [cGy] of 315.6, 348.1 and 361.9 for thyroid with administration of 100, 150 and 175 mCi of [131] I, respectively. For sternum the values found to be 201.5 cGy, 275.2 cGy and 242.6 cGy. For cervical vertebra results were 311.5 cGy, 184.1 cGy and 325.9 cGy. The average of measurements was 33.3 cGy using of TLDs on phantom and absorbed activity in thyroid were 94.9, 104.6 and 108.8 mCi in 24 hr for mentioned doses administration. In this work a method to obtain the absorbed activity in the thyroid and other surrounding tissues is described. By this method, the amount of [131] I needed for each patient also could be determined. The results of this work can be used in estimation of absorbed dose in thyroid and other organs using of MIRD method

Double mandibular foramina and canal: report of a case with interactive CT-based planning software

The identification of the mandibular canal and its anatomic variations is of great importance in many branches of dentistry, especially in implant dentistry and prior to endosteal implant insertion. This knowledge is even more demanding when the mandible has been compromised by different degrees of atrophy and bone resorption. In this study we describe a rare case of double mandibular canal identified by three-dimensional imaging techniques during the process of diagnosis. It is concluded that mandibular canals may often be undetected during the diagnosing phase of implant treatment, and tomographic imaging is the only way to identify some of these distinctive features

[Efficacy of stabilization splint therapy in temporomandibular disorders]

In clinical practice it is commonly assumed that occlusal splints have therapeutic value in the treatment of temporomandibular disorders [TMD], however there is still lack of sufficient evidence to support this claim. The purpose of this double-blind study was to evaluate the short-term [8-week] efficacy of a stabilization splint in subjects with temporomandibular disorders seeking treatment. Seventeen TMD patients were treated with stabilization splints for eight weeks. In addition to filling out questionnaires, all patients underwent a preoperative and postoperative clinical-functional investigation of the masticatory system. Qualitative data were analyzed using Fisher exact and Chi-square tests and Wilcoxon signed ranks test was applied to report quantitative data. A statistically significant decrease was observed postoperatively in the Helkimo clinical dysfunction index [P=0.000] as well as the anamnestic dysfunction index [P=0.020]. In addition there was a statistically significant decrease in muscle tenderness, after treatment [P=.002]. The results of this study indicate that the use of a stabilization splint is beneficial in treatment of the signs and symptoms of TMD, and especially has a positive effect on muscle tenderness