[Effective Techniques to Reduce Radiation Exposure to Medical Staff during Assist of X-ray Computed Tomography Examination].

Medical staffs like radiological technologists, doctors, and nurses are at an increased risk of exposure to radiation while assisting the patient in a position or monitor contrast medium injection during computed tomography (CT). However, methods to protect medical staff from radiation exposure and protocols for using radiological protection equipment have not been standardized and differ among hospitals. In this study, the distribution of scattered X-rays in a CT room was measured by placing electronic personal dosimeters in locations where medical staff stands beside the CT scanner gantry while assisting the patient and the exposure dose was measured. Moreover, we evaluated non-uniform exposure and revealed effective techniques to reduce the exposure dose to medical staff during CT. The dose of the scattered X-rays was the lowest at the gantry and at the examination table during both head and abdominal CT. The dose was the highest at the trunk of the upper body of the operator corresponding to a height of 130 cm during head CT and at the head corresponding to a height of 150 cm during abdominal CT. The maximum dose to the crystalline lens was approximately 600 µSv during head CT. We found that the use of volumetric CT scanning and X-ray protective goggles, and face direction toward the gantry reduced the exposure dose, particularly to the crystalline lens, for which lower equivalent dose during CT scan has been recently recommended in the International Commission on Radiological Protection Publication 118.

A novel approach to predict acute radiation dermatitis in patients with head and neck cancer using a model based on Bayesian probability.

PURPOSE: In this study, we aimed to establish a method for predicting the probability of each acute radiation dermatitis (ARD) grade during the head and neck Volumetric Modulated Arc Therapy (VMAT) radiotherapy planning phase based on Bayesian probability. METHODS: The skin dose volume >50 Gy (V50), calculated using the treatment planning system, was used as a factor related to skin toxicity. The empirical distribution of each ARD grade relative to V50 was obtained from the ARD grades of 119 patients (55, 50, and 14 patients with G1, G2, and G3, respectively) determined by head and neck cancer specialists. Using Bayes' theorem, the Bayesian probabilities of G1, G2, and G3 for each value of V50 were calculated with an empirical distribution. Conversely, V50 was obtained based on the Bayesian probabilities of G1, G2, and G3. RESULTS: The empirical distribution for each graded patient group demonstrated a normal distribution. The method predicted ARD grades with 92.4 % accuracy and provided a V50 value for each grade. For example, using the graph, we could predict that V50 should be ≤24.5 cm3 to achieve G1 with 70 % probability. CONCLUSIONS: The Bayesian probability-based ARD prediction method could predict the ARD grade at the treatment planning stage using limited patient diagnostic data that demonstrated a normal distribution. If the probability of an ARD grade is high, skin care can be initiated in advance. Furthermore, the V50 value during treatment planning can provide radiation oncologists with data for strategies to reduce ARD.

Rapid and automated analytical methods for redox species based on potentiometric flow injection analysis using potential buffers.

Two analytical methods, which prove the utility of a potentiometric flow injection technique for determining various redox species, based on the use of some redox potential buffers, are reviewed. The first is a potentiometric flow injection method in which a redox couple such as Fe(III)-Fe(II), Fe(CN)(6) (3-)-Fe(CN)(CN)(6) (4-), and bromide-bromine and a redox electrode or a combined platinum-bromide ion selective electrode are used. The analytical principle and advantages of the method are discussed, and several examples of its application are reported. Another example is a highly sensitive potentiometric flow injection method, in which a large transient potential change due to bromine or chlorine as an intermediate, generated during the reaction of the oxidative species with an Fe(III)-Fe(II) potential buffer containing bromide or chloride, is utilized. The analytical principle and details of the proposed method are described, and examples of several applications are described. The determination of trace amounts of hydrazine, based on the detection of a transient change in potential caused by the reaction with a Ce(IV)-Ce(III) potential buffer, is also described.

Examination of a dose evaluation method for floor-mounted kV X-ray image-guided radiation therapy systems.

Floor-mounted kV X-ray image-guided radiation therapy systems (such as ExacTrac) are used to treat tumors in movable body regions such as the head and neck. ExacTrac requires exposure dose control based on image acquisition. However, placement of the aluminum plate perpendicular to the dosimeter is difficult due to the oblique X-ray beam path. This study provides an evaluation of the entrance surface, organ, and effective doses delivered to the head and neck during image-guided radiation therapy. A semiconductor detector (Unfors Xi) and radiophotoluminescent glass dosimeter (RPLD) were used as dosimeters with entrance surface dose calculation (Sdec) and exposure estimation (PCXMC) software. When the Unfors Xi was placed in front of the flat panel detector (FPD), an accurate entrance surface dose was obtained by considering the X-ray attenuation due to the influence of the distance from X-ray tube to FPD.The couch absorption was 32% and incident air kerma at the patient entrance point was 0.094 mGy for Unfors Xi. The entrance surface doses were 0.12 and 0.122 mGy for the Sdec and RPLD, respectively. The thyroid organ doses were 0.044 and 0.058 mGy for the RPLD and PCXMC, respectively. The effective doses of PCXMC for ExacTrac and cone-beam computed tomography were 0.0068 and 0.31 mSv, respectively. The exposure dose of ExacTrac was approximately 2% of that of cone-beam computed tomography. The results demonstrated that the proposed software-based method is effective for the assessment and management of ExacTrac exposure.

Consideration of the Protection Curtain's Shielding Ability after Identifying the Source of Scattered Radiation in the Angiography.

To decrease radiation exposure to medical staff performing angiography, the dose distribution in the angiography was calculated in room using the particle and heavy ion transport code system (PHITS), which is based on Monte Carlo code, and the source of scattered radiation was confirmed using a tungsten sheet by considering the difference shielding performance among different sheet placements. Scattered radiation generated from a flat panel detector, X-ray tube and bed was calculated using the PHITS. In this experiment, the source of scattered radiation was identified as the phantom or acrylic window attached to the X-ray tube thus, a protection curtain was placed on the bed to shield against scattered radiation at low positions. There was an average difference of 20% between the measured and calculated values. The H*(10) value decreased after placing the sheet on the right side of the phantom. Thus, the curtain could decrease scattered radiation.

Complete mineralization of propyzamide in aqueous solution containing TiO2 particles and H2O2 by the simultaneous irradiation of light and ultrasonic waves.

Environmental problems arise from the pollution of ground water and soil by propyzamide, 3,5-dichloro-N-(3-methyl-1-butyn-3-yl) benzamide, which is a popular herbicide. To decompose propyzamide, aqueous solutions containing propyzamide and TiO2 particles was irradiated by light. The photocatalytic decomposition was accelerated when the solution temperature and pH were high. The temperature dependence was due to the adsorption processes of propyzamide on the TiO2 particles. The decomposition was further promoted by addition of H2O2 because of its effective electron-trapping and generated *OH which was available to decompose propyzamide. Although no propyzamide was detected in the solution after the irradiation time of about 20 min, the decomposed intermediate compounds still remained. In order to mineralize completely propyzamide, simultaneous irradiation by light and ultrasonic waves was carried out. The hybrid effect of the irradiation by light and ultrasonic waves in conjunction with H2O2 was first confirmed to achieve the complete mineralization of propyzamide.

Potentiometric determination of bromate using an Fe(III)-Fe(II) potential buffer by circulatory flow-injection analysis.

A method for the potentiometric determination of bromate by circulatory flow injection analysis (CFIA) is described. The procedure involves the use of an Fe(III)-Fe(II) potential buffer solution, which is recycled via a reservoir. The analytical method is based on a linear relationship between the concentration of bromate and a very transient potential change in the electrode potential due to the generation of intermediate bromine during the reaction of bromate with the Fe(III)-Fe(II) potential buffer solution, which also contains NaBr, (NH4)6Mo7O24 and H2SO4. An aliquot (5 microl) of a bromate sample solution was injected into the stream of the potential buffer solution, 100 ml of which was circulated at a flow rate of 1 ml/min; the potential buffer solution stream was then returned to the reservoir after passing through a flow-through redox electrode detector. A potential change due to the reaction of the injected sample with the potential buffer in a reaction coil was measured with the detector in the form of a peak signal. The effects of the bromide, sulfuric acid and Fe(III)-Fe(II) concentrations in the potential buffer, and length of the reaction coil on the peak heights were examined in order to optimize the proposed CFIA method. The analytical sensitivities to bromate were 5.6 mV/microM for 1 x 10(-2) M and 30.9 mV/microM for 1 x 10(-3) M in the concentration of Fe(III)-Fe(II) in a potential buffer solution containing 0.35 M NaBr, 0.2% (NH4)6Mo7O24 and 1 M H2SO4. The detection limit of bromate obtained by a 1 x 10(-3) M Fe(III)-Fe(II) potential buffer solution was 0.02 microM (2.5 ppb). The numbers of repetitive determinations in which the relative sensitivities within 5% were regarded as being tolerated were ca. 4000 and 2000 for the use of only 100 ml of 1 x 10(-2) M and 1 x 10(-3) M Fe(III)-Fe(II) potential buffer solution, respectively.

[Usefulness of the opposite direction for Stenvers' method].

In otorthinolaryngology, Stenvers' method is employed in radiography of the pyramid (internal acoustic meatus and semicircular canals). However, in cases of dizziness, where the prone position is difficult to achieve, we occasionally use the opposite Stenvers' method instead of the conventional one. This makes it possible to perform radiography with the patient in the supine position. Compared with the conventional Stenvers' method, the problems of this method were increases not only in the rate of magnification but also in lens dose. In this study, we evaluated these problems by employing computed tomography (CT) and a glass dosimeter with phantom as well as by clinical evaluation. The results showed no statistically significant difference between Stenvers' method and the opposite Stenvers' method in both the rate of magnification and the clinical evaluation. The increase in lens dose with the opposite Stenvers' method was not significant. We concluded that the opposite Stenvers' method was useful.

Clinical results of definitive chemoradiotherapy for patients with synchronous head and neck squamous cell carcinoma and esophageal cancer.

OBJECTIVES: To assess the efficacy and toxicity of radical chemoradiotherapy for patients with synchronous head and neck squamous cell carcinoma (HNSCC) and esophageal cancer (EC). METHODS: Thirty-four patients with synchronous HNSCC and EC were treated mainly with radical chemoradiotherapy at the same time. Median external radiation dose for HNSCC and EC was 70 Gy (range, 60-70.5 Gy), except for 2 patients with tongue cancer, who underwent brachytherapy and 60 Gy (range, 45-70 Gy), respectively. Thirty-one patients were treated with concurrent chemoradiotherapy with cisplatin and/or 5-fluorouracil or TS-1 (oral anticancer agent that combines tegafur, a metabolically activated prodrug of 5-fluorouracil, with 5-chloro-2, 4-dihydoroxypyridine, and potassium oxonate). RESULTS: Thirty-three patients completed the intended treatment. The response rate was 94%, with 26 complete responses (76%) and 6 partial responses (18%). At a median follow-up of 17.3 months, 2-year rates of overall survival, cause-specific survival, and disease-free survival were 44%, 52%, and 33%, respectively. Initial failure patterns were local failure in 14 patients (63%), regional progression in 3 patients (13%), and distant metastasis in 6 patients (27%). The most common acute toxicity was myelosuppression, with 8 patients experiencing grade 3-4 toxicity. Three patients experienced grade 3 mucositis and pharyngitis. No patients experienced late morbidity of grade 3 or higher. CONCLUSIONS: Definitive chemoradiotherapy for patients with synchronous HNSCC and EC is feasible with a low mortality rate and acceptable morbidity.

Treatment outcomes of radiotherapy for patients with stage I esophageal cancer: a single institute experience.

OBJECTIVES: To evaluate the effectiveness of radiotherapy for patients with stage I esophageal cancer. METHODS: From 1995 to 2005, 34 patients with superficial thoracic esophageal squamous cell carcinoma without lymph node metastasis were treated with radiotherapy at our institute. Patient characteristics were as follows: median age, 68 years; range, 47 to 84 years; male:female, 33:1; performance status, 0/1/2/3 = 23/9/1/1; T1a/T1b = 4/30. Median fraction and total doses of external irradiation given were 2.0 Gy and 60 Gy, respectively. Twenty-three patients had local irradiation to the primary lesion only; the remaining 11 patients received regional field irradiation, including one or 2 regional lymph node areas. Only one patient received adjuvant intracavitary radiotherapy after radiotherapy. Thirty of the patients received concurrent chemotherapy, most of the regimens of which included cisplatin and 5-fluorouracil. Adjuvant chemotherapy was performed in 5 patients. Fifteen patients (44%) had coexisting malignancies. The median follow-up was 38 months (range, 8-107 months). RESULTS: The 5-year overall, cause-specific, and local-progression-free survival rates were 50.4%, 91.2%, and 81.1%, respectively. Of the 34 patients, 6 had in-field local recurrence, and one had recurrence in the esophagus outside of the irradiated field. Two patients experienced regional lymph node metastasis outside of the irradiated field, and one had distant metastasis. Two patients received salvage surgery, and 4 patients received salvage intracavitary radiotherapy after local recurrence. A late toxicity greater than grade 2 was not observed in any patient. CONCLUSIONS: Radiotherapy is an effective treatment modality for patients with stage I esophageal cancer.

Potentiometric flow injection determination of manganese(II) by using a hexacyanoferrate(III)-hexacyanoferrate(II) potential buffer.

A highly sensitive potentiometric flow injection analysis method for the determination of manganese(II), utilizing a redox reaction with hexacyanoferrate(III) in near neutral media containing ammonium citrate is described. The analytical method is based on the detection of the change in potential of a flow-through type redox electrode detector, resulting from the composition change of an [Fe(CN)(6)](3-)-[Fe(CN)(6)](4-) potential buffer solution. A linear relationship between the potential change (peak height) and the concentration of manganese(II) was found. Manganese(II) in a wide concentration range from 10(-4) to 10(-7) M could be determined by appropriately altering the concentration of the potential buffer from 10(-3) to 10(-5) M. The lower detection limit of manganese(II) was determined to be 1x10(-7) M. The sampling rate and relative standard deviation were 20 h(-1) and 1.9% (n=8) for 6x10(-6) M manganese(II), respectively. The proposed method was successfully applied to the determination of manganese(II) in actual soil samples obtained from tea fields. Analytical results obtained by the proposed method were in good agreement with those obtained by an atomic absorption spectrophotometric method.