Performance assessment and uncertainty evaluation of a portable NaI-based detection system used for thyroid monitoring

This work aims at assessing the performance of a portable detection system, equipped with an NaI(Tl) scintillation detector for in vivo thyroid monitoring, which was properly calibrated using an anthropomorphic neck phantom. The anthropomorphic physical phantoms commonly used for the efficiency calibration of in vivo counters often present certain limitations regarding the geometry and the activity distribution. Therefore, the feasibility of these detection systems for in vivo monitoring should be assessed whenever possible. To accomplish this assessment, patients to whom (99m)Tc and (123)I marked radiopharmaceuticals have been administered in the framework of nuclear medicine diagnostic procedures were monitored. As the biokinetic models of the administered radiopharmaceuticals are known, the time-dependent activity functions in the critical organs after administration are easily quantified. The measured activities in the thyroid using the NaI(Tl) scintillation detector were compared with the estimated activities using the biokinetic models, in order to reach conclusion about the applicability of the portable scintillation counter for in vivo thyroid monitoring. The state-of-the-art Monte Carlo computer program PENELOPE and two voxel phantoms (male and female) were used to evaluate the overall uncertainties influencing the thyroid monitoring. A computational parametric study was performed to quantify the influence of several parameters in the activity quantification (neck-detector distance, thyroid shape, thyroid size and overlying tissue thickness), which allowed one to gain insight and to better understand the discrepancies between the calculated and measured activities.

Monte Carlo modeling and simulations of the High Definition (HD120) micro MLC and validation against measurements for a 6 MV beam

PURPOSE

The most recent Varian(®) micro multileaf collimator (MLC), the High Definition (HD120) MLC, was modeled using the BEAMNRC Monte Carlo code. This model was incorporated into a Varian medical linear accelerator, for a 6 MV beam, in static and dynamic mode. The model was validated by comparing simulated profiles with measurements.

METHODS

The Varian(®) Trilogy(®) (2300C/D) accelerator model was accurately implemented using the state-of-the-art Monte Carlo simulation program BEAMNRC and validated against off-axis and depth dose profiles measured using ionization chambers, by adjusting the energy and the full width at half maximum (FWHM) of the initial electron beam. The HD120 MLC was modeled by developing a new BEAMNRC component module (CM), designated HDMLC, adapting the available DYNVMLC CM and incorporating the specific characteristics of this new micro MLC. The leaf dimensions were provided by the manufacturer. The geometry was visualized by tracing particles through the CM and recording their position when a leaf boundary is crossed. The leaf material density and abutting air gap between leaves were adjusted in order to obtain a good agreement between the simulated leakage profiles and EBT2 film measurements performed in a solid water phantom. To validate the HDMLC implementation, additional MLC static patterns were also simulated and compared to additional measurements. Furthermore, the ability to simulate dynamic MLC fields was implemented in the HDMLC CM. The simulation results of these fields were compared with EBT2 film measurements performed in a solid water phantom.

RESULTS

Overall, the discrepancies, with and without MLC, between the opened field simulations and the measurements using ionization chambers in a water phantom, for the off-axis profiles are below 2% and in depth-dose profiles are below 2% after the maximum dose depth and below 4% in the build-up region. On the conditions of these simulations, this tungsten-based MLC has a density of 18.7 g cm(- 3) and an overall leakage of about 1.1 ± 0.03%. The discrepancies between the film measured and simulated closed and blocked fields are below 2% and 8%, respectively. Other measurements were performed for alternated leaf patterns and the agreement is satisfactory (to within 4%). The dynamic mode for this MLC was implemented and the discrepancies between film measurements and simulations are within 4%.

CONCLUSIONS

The Varian(®) Trilogy(®) (2300 C/D) linear accelerator including the HD120 MLC was successfully modeled and simulated using the Monte Carlo BEAMNRC code by developing an independent CM, the HDMLC CM, either in static and dynamic modes.

Hemoptysis--etiology, evaluation and treatment in a university hospital

OBJECTIVE

Evaluate patients admitted for hemoptysis, its etiology, use of diagnostic tests, treatment and outcome.

METHODS

A retrospective analysis was done, checking clinical files of patients admitted for hemoptysis, between 1st January 2004 and 31st December 2008.

RESULTS

Two hundred and thirty seven patients were included in this study, with a mean age of 57.9 years. In patients under 18 years, the most frequent diagnoses were Bronchiectasis and Congenital Cardiopathy. In adults, Pulmonary Tuberculosis Sequelae and Bronchiectasis were the dominant diagnoses (22.2 % and 15.8 %, respectively), followed by Lung Cancer. Active infection was responsible for bleeding in 51 patients, especially Pulmonary Tuberculosis, Pneumonia and Tracheobronchitis. The etiology of hemoptysis was not established in 6.3 %. All patients performed chest X-Ray. Chest CT was performed in 81.4 % of patients and Fiberoptic bronchoscopy in 52.7 %, the latter locating the source of bleeding in 38.4 % and establishing a final diagnosis in 17.6 %. In most patients, effective control of bleeding was achieved by medical treatment (90.7 %). During these 5 years, arterial embolization was performed in 11.8 % of patients. The main reason for embolization was recurrence prevention. There were 14 deaths (5.9 %), being identified as poor prognostic factors, hemodynamic instability and malignancy.

CONCLUSION

Hemoptysis is still a frequent symptom, being chronic infection sequelae and lung cancer their main causes. In this study, factors associated with a worse prognosis were hemodynamic instability and malignancy.

Exercise training decreases proinflammatory profile in Zucker diabetic (type 2) fatty rats

OBJECTIVE

In the present study we evaluated the effect of exercise on the plasma levels of proinflammatory cytokines, interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha), and the anti-inflammatory molecule uric acid in the Zucker diabetic fatty (ZDF) rats that are more prone to develop type 2 diabetes mellitus.

METHODS

Sixteen obese ZDF (Gmi fa/fa) rats (8 wk old, 228.40 +/- 4.05 g) were randomly assigned to one of two groups (n = 8 each): an exercise-trained group and a sedentary one. In addition, 16 lean ZDF (Gmi +/+) rats (8 wk old, 199.00 +/- 3.50 g) were subjected to identical sedentary and exercise conditioning (n = 8 each). Initially, rats swam 15 min/d (5 d/wk) in a 36 degrees C bath. The exercise protocol was gradually increased by 15 min/d until a swimming period of 1 h/d (1 wk) was attained. Thereafter, rats swam 1 h/d, 3 d/wk, for an additional period of 11 wk. Rats were sacrificed 48 h after the last training period and the blood and pancreas were collected. Circulating levels of glucose, glycosylated hemoglobin, total cholesterol, triglycerides, insulin, uric acid, IL-6, and TNF-alpha were assessed. The concentrations of proinflammatory cytokines in the pancreas were also evaluated.

RESULTS

In the diabetic ZDF (fa/fa) rats, exercise decreased hyperuricemia (-37.3%) and IL-6 and TNF-alpha levels (-16.9% and -12.7% respectively) and maintained the weight of the pancreas at near normal. Immunohistochemistry revealed a marked decrease in the expression of TNF-alpha and IL-6 in the pancreatic islet cells of ZDF (fa/fa) rats.

CONCLUSION

These results indicate that aerobic exercise is anti-inflammatory in nature.

Results of radiation protection programmes on mammography

In this paper, we present the results of mammography quality control tests related to the work with Portuguese mammography equipment, either in conventional or in digital mammography computed radiography, showing the main differences in the tested equipments. Quality control in mammography is a very special area of quality control in radiology, which demands relatively high knowledge on physics. Digital imaging is changing the standards of the radiographic imaging. Regarding mammography, this is yet a controversial issue owing to some limitations of the digital detectors, like the resolution for instance. A complete set of results regarding radiation protection of the patients submitted to mammography diagnosis is presented. A discussion of the quality image parameters and its interpretation in conventional and digital mammography is presented. In conclusion, we present a sample of results that can be considered as characteristics of mammography equipment in Portugal.

Expression of mRNA encoding insulin-like growth factors I and II by uterine tissues and placenta during pregnancy in the rat

The uterus and the placenta synthesize insulin-like growth factors (IGFs) and insulin-like binding proteins (IGFBPs). These growth factors are implicated in processes of proliferation and differentiation that occur in the uterus. To determine the patterns of expression of IGFs during rat pregnancy we used in situ hybridization with digoxigenin labeled probes on uterus from day 7 to day 16 of pregnancy. In early gestation days (7-8) both IGF mRNAs showed similar tissue distribution with relative abundance in the stroma and circular muscle layer. On days 11 and 12 expression for IGF-I mRNA was found in the mesometrial decidua and metrial gland and in the ectoplacental cone while clear expression of IGF-II mRNA could only be found in the latter. On days 13 and 14, expression for IGF-I mRNA could be detected in the mesometrial decidua and metrial gland but no expression was observed for IGF-II mRNA. A gradient of IGF-I mRNA expression could be observed in the placenta on day 16, with the trophoblastic cells of the basal zone expressing the signal with stronger intensity than in the labyrinthine zone. For IGF-II mRNA the highest expression was associated with the labyrinthine zone. Endovascular trophoblast was positive for both mRNAs. The spatial and temporal patterns of expression suggests a role for IGFs in the process of decidualization as well as in the establishment, growth and differentiation of the various trophoblast cells of the placenta.

Expression of mRNA encoding decidualization-associated protein, a variant of acute-phase alpha 2 macroglobulin, by rat uterine tissues during pregnancy and pseudopregnancy

The patterns of expression of mRNA encoding decidualization-associated protein (DAP) in the rat uterus from early, mid-, and late stages of pregnancy were examined by in situ hybridization to provide an insight into the function of DAP during pregnancy. Parallel studies were performed on rat uteri during the oestrous cycle and oil-induced deciduomata. DAP transcripts were absent in virgin uteri and during the day of implantation (day 5), low in early gestation tissues (days 8, 9) and high during midgestation (days 10-14). Expression of mRNA encoding DAP was first detected on day 8 of pregnancy in decidual cells of the lateral decidual glycogen wing areas. On day 9, mRNA encoding DAP was found in the same area as on day 8 as well as in the outer layer of cells in the antimesometrial decidua adjacent to the myometrium termed the fibrinoid capsula. On days 11 and 12, expression appeared in the decidual cells of the mesometrial decidua, and was particularly strong around the ectoplacental cone and blood vessels that were invaded by the trophoblast. By day 13 and throughout the remainder of pregnancy, expression occurred in the mesometrial decidua and metrial gland. No signal was observed in granulated metrial gland cells. mRNA encoding DAP was also found in the smooth circular muscle coat adjacent to the mesometrial decidua. A similar pattern and cellular localization of expression of mRNA encoding DAP expression was detected during the development of the deciduomata, artificially induced in the absence of a conceptus. The spatial and temporal patterns of expression correlated with a possible role for DAP in mediating fetal-maternal interactions and the establishment of the placental structure.