New developed cylindrical TM010 mode EPR cavity for X-band in vivo tooth dosimetry.

EPR tooth in vivo dosimetry is an attractive approach for initial triage after unexpected nuclear events. An X-band cylindrical TM010 mode resonant cavity was developed for in vivo tooth dosimetry and used in EPR applications for the first time. The cavity had a trapezoidal measuring aperture at the exact position of the cavity's cylindrical wall where strong microwave magnetic field H1 concentrated and weak microwave electric field E1 distributed. Theoretical calculations and simulations were used to design and optimize the cavity parameters. The cavity features were evaluated by measuring DPPH sample, intact incisor samples embed in a gum model and the rhesus monkey teeth. The results showed that the cavity worked at designed frequency and had the ability to make EPR spectroscopy in relative high sensitivity. Sufficient modulation amplitude and microwave power could be applied into the aperture. Radiation induced EPR signal could be observed remarkably from 1 Gy irradiated intact incisor within only 30 seconds, which was among the best in scan time and detection limit. The in vivo spectroscopy was also realized by acquiring the radiation induced EPR signal from teeth of rhesus monkey whose teeth was irradiated by dose of 2 Gy. The results suggested that the cavity was sensitive to meet the demand to assess doses of significant level in short time. This cavity provided a very potential option for the development of X-band in vivo dosimetry.

Microdosimetric calculation of spherical cells and ellipsoidal red blood cells in an extremely low frequency electromagnetic field / 军事医学

Objective To calculate the electric field intensity and transmembrane voltage of spherical cells and ellipsoi -dal red blood cells ( RBC) in an extremely low frequency electromagnetic field .Through this calculation , we can provide reference to the search for interaction targets and mechanics between the extremely low frequency electromagnetic field and organisms.Methods The Finite Element Method was used in the numerical computation for the spherical cell model and the ellipsoidal RBC model .Results The electric field intensity of the two types of cells on the cellular membrane was both significantly higher than the applied electric field strength , and the values of the induced field strength and transmembrane voltage varied with the direction of the electric field periodically .Conclusion The cell shape and direction of the applied electric field are not the main determinants of the cellular membrane electric field intensity and the transmembrane voltage compared with electromagnetic parameters .The distribution of the electric field intensity and transmembrane voltage are re-lated to the direction of the applied electric field.

An efficiency calibration method without a radioactive source using BOMAB phantom and Monte Carlo simulation for Inspector 2000 gamma spectroscopy system / 中华放射医学与防护杂志

Objective To establish an efficiency calibration method without a radioactive source for Inspector 2000 gamma spectroscopy system.Methods At the fwst step,geometry parameters of the detector were properly specified by comparisons of FEPE(Full Energy Peak Efficiency)between Monte Carlo(MC)calculations and the average measured values of HPGe and NaI detectors using point sources(137 Cs).The differences between calculations and measurements were generally within ±10% for gamma rays.Then,Monte Carlo simulation was used to evaluate the counting efficiency of Nal(TI)and HPGe detectors for BOMAB phantoms.Corresponding efficiency curves and functions were fitted.Results The counting efficiency received from the fitted efficiency functions had a good agreement with those from MC simulation.The bias for Nal detector ranged from-19% to 18%,while the bias for HPGe detector ranged from-11% to 17%.The above errors were totally acceptable in the on-site deployment during nuclear and radiological emergency events.Conclusions Monte Carlo method is simple,time and laborsaving in determing the counting efficiency of gamma spectroscopy system.

The EM energy absorption in different rat model exposed to microwave irradiation / 中华放射医学与防护杂志

Objective To find out the relationship between the weight and whole body averaged SAR. and the relationship between the weight and the EM energy absorption in rat model exposed to 3 GHz microwave irradiation.Methods Based on 3D rat NMR images,a rat EM model consisting of 45 tissues was established, then by changing the size of model cell,16 models of which the sizes varied from 9 cm to 24 cm, and the weights from 16 g tO 334 g correspondingly were established too.Using FDTD method,the induced electric fields in these rat models were calculated,and then SAR and EM energy absorption have been obtained accordingly.Results The relationship between the weight and the whole body averaged SAR of rat model exposed to 3 GHz microwave irradiation can be divided into three sections,and each of them can be fitted into one line.In small rat section, SAR changed sharply;in middle rat section,SAR changed moderately;in large rat section,SAR changed litflely.The relationship between the weight and the EM energy absorption of rat model were fitted into one quadratic polynomial curve.The EM energy absorption was almost identical when the model is small,with the increasing of the weight,the EM energy absorption also increases,but the increasing ratio of the energy is less than that of the weight.Conclusions Larger rat absorbs more EM energy,but gets less SAR.Exposed to the same irradiation,the dose differences of larger rat is much less than that of smaller rat because of the changes in body weight,so the larger rat is to be recommended.

Pathologic foundation and clinical value for extrabiliary malignant tumor inducing bile duct stenosis / 重庆医科大学学报

0.05).Conclusion:Infiltrating throuth the wall of bile duct and into biliary lumen is the pathologic foundation for extrabiliary malignant tumor inducing bile duct stenosis.

Hypothyroidism after partial thyroidectomy:a report of 41 cases / 中国普通外科杂志

Objective To demonstrate the incidence and relative factors of hypothyroidism after partial thyroidectomy (PTC). Methods The records of all euthyroidsm patients who underwent hemithyroidectomy from 1988 to 2000 were reviewed to determine the incidence of postoperative hypothyroidism and the predisposing factors. All the patients age, gender, serum TSH TGA and TPO levels,and the weight of resected thyroid tissue were evaluated. Hypothyroidsm patients were evaluated for the symptoms , timing of diagnosis , and thyroxine therapy. Results Hypothyroidism was diagnosed in 41(3.4%) of 1 210 patients ,inclnding subclinical hypothyroidsm in 28 and overt in 13.The mean postoperative serum TSH level was (9.22?3.36)mU/L. The mean preoperative serum TSH level was (3.14?1.05)mU/L in hypothyroidsm patients but in euthyroid patients was (1.07?0.72)mU/L(P