Possibilities of the exposure reduction of hands during the preparation and application of radiopharmaceuticals.

BACKGROUND: The current routinely used methods of estimating the skin equivalent dose relies on the finger dosimetry which usually largely underestimates the real maximum exposure and thus appropriate correction factors have to be used. METHODS: The group under the investigation consisted of 10 workers preparing and 5 workers administering radiopharmaceuticals labelled with 18F. The monitoring was carried out using 12 pairs of thermoluminiscent dosimeters (TLDs) placed on each hand of the worker. A total of 46 measurements were completed. The maximum exposure of the skin of hands, defined in terms of the quantity of the personal dose equivalent Hp(0.07), was related to the unit activity of radiopharmaceutical with which the worker came into the contact during the measurement. RESULTS: The exposure of the hands of workers handling 18F-labelled radiopharmaceuticals showed significant inhomogeneity. Out of 15 workers, in 53 % of cases, the maximum skin exposure was observed on the tip of their index finger. It was estimated that in about 60 % of the cases (during the preparation and administration of radiopharmaceuticals), the exposure may exceed the 3/10 of the annual dose limit. Moreover, in 40 % of all cases, the exposure may even be higher than this dose limit. The established relevant correction factors reached the values up to 8 (as for preparations) and 13 (as for administrations). CONCLUSIONS: The study resulted in the establishment of the appropriate correction factors and in the recommendations of procedures aimed at the further reduction of the exposure of extremities (Tab. 3, Fig. 2, Ref. 17).

ASSESSMENT OF THE LOCAL EXPOSURE OF SKIN ON HANDS OF NUCLEAR MEDICINE WORKERS HANDLING 18F-LABELLED RADIOPHARMACEUTICALS: PRELIMINARY CZECH STUDY.

The article summarises some preliminary results of the assessment of the exposure of hands of workers manipulating 18F-labelled radiopharmaceuticals based on personal monitoring at two nuclear medicine clinics in the Czech Republic. The measurements were carried out using special thermoluminescence dosemeters the readings of which could be interpreted in terms of the personal dose equivalent Hp(0.07) approximating the equivalent dose to the skin at various locations on the surface of both hands. The results have shown that out of 21 workers monitored, ∼43 % (preparation and applications of radiopharmaceuticals) may reach an exposure equal to three-tenth of the annual dose limit to the skin. At the same time, it can also be concluded that in ∼10 % cases of workers, the relevant dose limit may be exceeded.

Occupational exposure control: the problem of quantities in radiation protection.

The paper explores the quantities and units used in radiation protection with special emphasis on their applications in occupational exposure control. An overview of the current situation reveals that there seem to be too many different quantities associated with the same unit. Some of these quantities are defined in a quite complicated manner and, therefore, may cause some confusion in their interpretation and practical use in the field. Some suggestions towards the simplification of the present system are also proposed.

Assessment of the total effective dose of miners in the underground Rozná Uranium Mine in the Czech Republic during the period 2004-2009.

The paper discusses the situation in the Czech Republic regarding past and present uranium mining activities with emphasis on the evaluation of the exposure of underground miners in the Rozná Uranium Mine, which is currently the only active mine in the country and practically in the entire European Union. The total effective dose has been summarised taking into account all three major components, namely radon short-lived decay products, long-lived alpha emitters in ore dust and penetrating external gamma radiation. The average and maximum values of the effective dose as well as the collective effective dose of underground miners are also presented. The purpose of the paper is to document the miners' exposures during a period of 6 years in a uranium mine where conditions including the ore grade and methods of mining showed recently some changes that may affect the individual components of the total effective dose.

Estrogen replacement therapy after breast cancer: a 12-year follow-up.

BACKGROUND: In the United States, estrogen replacement therapy (ERT) is discouraged in breast cancer survivors because of concerns that hormones may reactivate the disease. Because ERT can improve quality of life and decrease morbidity from osteoporosis and cardiovascular disease, however, this policy is increasingly being challenged. METHODS: From February to August 1995, 607 breast cancer survivors were interviewed concerning ERT usage. Sixty-four patients indicated they received some form of ERT after their breast cancer diagnosis. Medical records for these patients were analyzed for disease stage, surgical treatment, adjuvant treatment, estrogen and progesterone receptor status, date of initiation of ERT, type of ERT, recurrence, and final outcome. Patients receiving ERT were followed prospectively. RESULTS: Eight patients were excluded because they had used only vaginal cream ERT. The remaining 56 received ERT as conjugated estrogens, an estradiol patch, estropipate, or birth control pills. The median follow-up from diagnosis was 12.8 years (range, 4.7-38.9 years). The median time on ERT since diagnosis was 6.4 years (range, 1.0-20.9 years); 38% of the patients initiated ERT within 2 years of diagnosis. Estrogen receptors were positive in 28 (74%) of the 38 cases with available information. Pathological disease stage at time of diagnosis and treatment was 0 in 15 cases (27%), I in 27 (48%), and II in 14 (25%). Twenty-six patients (47%) received adjuvant chemotherapy or hormonal therapy. One local recurrence and one contralateral breast cancer occurred during the follow-up period (13.5 and 9.6 years, respectively), with no regional or distant recurrences, for a 15-year actuarial disease-free survival rate of 92.5%. There were no breast cancer deaths. CONCLUSIONS: Use of ERT in a cohort of breast cancer survivors with tumors of generally good prognosis was not associated with increased breast cancer events compared with non-ERT users, even over a long follow-up period.

A Monte Carlo study of x-ray fluorescence in x-ray detectors.

Advances in digital x-ray detector systems have led to a renewed interest in the performance of x-ray phosphors and other detector materials. Indirect flat panel x-ray detector and charged coupled device (CCD) systems require a more technologically challenging geometry, whereby the x-ray beam is incident on the front side of the scintillator, and the light produced must diffuse to the back surface of the screen to reach the photoreceptor. Direct detector systems based on selenium have also enjoyed a growing interest, both commercially and academically. Monte Carlo simulation techniques were used to study the x-ray scattering (Rayleigh and Compton) and the more prevalent x-ray fluorescence properties of seven different x-ray detector materials, Gd2O2S, CsI, Se, BaFBr, YTaO4, CaWO4, and ThO2. The redistribution of x-ray energy, back towards the x-ray source, in a forward direction through the detector, and lateral reabsorption in the detector was computed under monoenergetic conditions (1 keV to 130 keV by 1 keV intervals) with five detector thicknesses, 30, 60, 90, 120, and 150 mg/cm2 (Se was studied from 30 to 1000 mg/cm2). The radial distribution (related to the point spread function) of reabsorbed x-ray energy was also determined. Representative results are as follows: At 55 keV, more (31.3%) of the incident x-ray energy escaped from a 90 mg/cm2Gd2O2S detector than was absorbed (27.9%). Approximately 1% of the total absorbed energy was reabsorbed greater than 0.5 mm from the primary interaction, for 90 mg/cm2 CsI exposed at 100 kVp. The ratio of reabsorbed secondary (fluorescence + scatter) radiation to the primary radiation absorbed in the detectors (90 mg/cm2) (S/P) was determined as 10%, 16%, 2%, 12%, 3%, 3%, and 0.3% for a 100 kVp tungsten anode x-ray spectrum, for the Gd2O2S, CsI, Se, BaFBr, YTaO4, CaWO4, and ThO2 detectors, respectively. The results indicate significant x-ray fluorescent escape and reabsorption in common x-ray detectors. These findings suggest that x-ray fluorescent radiation redistribution should be considered in the design of digital x-ray imaging systems.

Dietary glycotoxins: inhibition of reactive products by aminoguanidine facilitates renal clearance and reduces tissue sequestration.

Evidence indicates that the metabolic turnover of food-derived reactive orally absorbed advanced glycation end products (AGEs) or glycotoxins (GTs) is delayed, possibly contributing to the tissue damage induced by endogenous AGEs, especially in patients with diabetes and kidney disease. The aim of this study was to explore whether pharmacologic inhibition of dietary AGE bioreactivity by aminoguanidine (AG) can improve turnover and renal excretion of these substances. Normal Sprague-Dawley rats were fed single-labeled [14C]AGE-ovalbumin, double-labeled [14C-125I]AGE-ovalbumin, or control 125I-labeled ovalbumin diet plus free [14C]glucose, with or without AG (0.2% in water). [14C]AGE- and 125I-labeled peptide-associated radioactivity (RA) were compared with AGE immunoreactivity (by enzyme-linked immunosorbent assay) in tissues, serum, and 72-h urine samples. The effect of AG on dietary AGE bioreactivity was assessed by monitoring the inhibition of covalent complex formation between fibronectin (FN) peptide fragments and serum components, after a meal of labeled dietary AGE with or without AG. The radiolabeled AGE diet produced serum absorption and urinary excretion peaks kinetically distinct from those of free [14C]glucose or [125I]ovalbumin. Some 26% of the orally absorbed AGE-ovalbumin was excreted in the urine, whereas after AG treatment, urinary excre-tion of dietary AGEs increased markedly (to >50% of absorbed). More than 60% of tissue-bound RA was found covalently deposited in kidneys and liver, whereas after treatment with AG, tissue AGE deposits were reduced to <15% of the amount found in untreated AGE-fed controls. Sera enriched for dietary GTs formed covalently linked complexes with FN, a process completely inhibitable by AG cotreatment. Amelioration of dietary GT bioreactivity by AG improves renal elimination and prevents tissue deposition of food GTs. This may afford a novel and potentially protective use of AG against excessive tissue AGE toxicity in diabetic patients with renal disease.

Concurrent administration of vinorelbine with recombinant human granulocyte colony-stimulating factor: an effective method of increasing dose intensity.

Thirty-three patients with incurable neoplasms resistant to standard therapy received vinorelbine 8 mg/m2 to 10 mg/m2 per day by continuous infusion with concurrent administration of recombinant human granulocyte colony-stimulating factor 5 microm/m2 per day. The duration of the vinorelbine infusion was individualized; the infusion was continued until early evidence of hematopoietic toxicity was noted. The concurrent administration of recombinant human granulocyte colony-stimulating factor permitted a substantial increase in dose intensity of the anticancer agent without a corresponding increase in drug toxicity. There was no evidence that the antitumor effect of vinorelbine was compromised by the concurrent administration of recombinant human granulocyte colony-stimulating factor.

Control of industrial discharges to the public sewerage system

El artículo trata sobre los problemas que acarrea la descarga de efluentes industriales en el sistema de alcantarillado municipal, y el tratamiento junto al de las aguas residuales. Se analizan los efectos que producen los efluentes sobre la red de alcantarillado y sobre las plantas de tratamiento, criterios legislativos a tener en cuenta, el control de calidad y volumen de los efluentes, entre otros aspectos

Autostrangulation of the vermiform appendix. An unusual mechanism of acute appendicitis.

A 23-year-old woman presented with acute appendicitis. At laparoscopy the appendix appeared to be strangulating itself. The pathologic evaluation demonstrated mucosal coagulation necrosis, confirming the early ischemic changes of the infarctive process visualized laparoscopically.

Scintillating fiber optic screens: a comparison of MTF, light conversion efficiency, and emission angle with Gd2O2S:Tb screens.

The widespread effort in developing digital imaging systems has led to large area high pixel density photodetectors such as charge coupled devices (CCDs), amorphous silicon photodiode arrays, and complementary metal oxide semiconductor (CMOS) imagers. These photodetectors have different capabilities, characteristics, and requirements than conventional silver-halide-based film, and this fact had led to a new generation of exotic scintillators, including fiber optic screens made from scintillating glass. The scintillator performance characteristics of five different scintillating fiber optic screens and two conventional Gd2O2S:Tb screens (one 34 mg/cm2 and the other 60 mg/cm2) were measured and compared. The measurements that were made included the angular dependence of light emission relative to the normal, the modulation transfer function (MTF), and the absolute effective conversion efficiency (light photons per absorbed x-ray photon). It was found that the light emission of scintillating fiber optic screens is markedly forward peaked (depending on the sample) compared to conventional screens or Lambertian emitters. The MTFs of the five scintillating fiber optic screens measured were comparable and fell approximately midway between the two conventional screen MTFs. One of the scintillating fiber optic screens demonstrated light efficiency similar to the thick (60 mg/cm2) conventional screen, another had light output capabilities similar to the thin (34 mg/cm2) conventional screen, and the three others were less efficient than the thin screen. The non-Lambertian characteristics of the fiber optic scintillators will cause errors of up to 75% in lens efficiency calculations if a Lambertian source is assumed. The conventional screens were found to conform within about 5% of an ideal Lambertian emitter.

Practical application of a scan-rotate equalization geometry to mammography.

The presence of dense fibroglandular tissue within the breast is the most significant cause of failure to detect breast cancer with mammography. The dense tissue often produces a range of exposure which exceeds the useful dynamic range of film-screen mammography. It has been shown that equalization radiography overcomes the latitude limitations of film-screen imaging. Equalization compensates for regional variations in x-ray transmission within the patient through spatial modulation of the entrance exposure. We have proposed rotary scanning equalization radiography (RSER), a scan-rotate geometry for efficient equalization radiography. In RSER the image receptor is exposed by repeated scans of a source-modulated fan beam. The fan beam is rotated with respect to the patient between scans. Numerical simulations and theoretical analysis have shown that the superposition of exposure from appropriately modulated fan beams at a variety of angles is an entrance exposure that effectively equalizes the film exposure. The design and characteristics of a prototype RSER imaging system are described. Anthropomorphic breast phantom images are used to determine the improvement in image contrast obtained with RSER, the expected tube loading, and the presence of artifacts. RSER increases the fraction of the breast imaged with high contrast (at least 90% of peak gradient) from 46% (conventional mammography) to 80%. Subjective examination of the phantom images show that RSER achieves image quality very similar to that of much less efficient equalization geometries with only 2.7 times greater tube loading than conventional mammography. As predicted by theoretical analysis of exposure artifacts in RSER, the prototype RSER system is relatively immune to artifacts. Exposure artifacts were demonstrated for extreme variations in x-ray transmission within the patient. These results show that RSER is an efficient, practical means of overcoming the latitude limitations of film-screen mammography, and improving the detection of breast cancer.

Analytical description of the high and low contrast behavior of a scan-rotate geometry for equalization mammography.

Many solutions have been proposed to overcome the problem of imaging the radiographically dense breast with high contrast mammographic film of limited dynamic range. In previous works, we have proposed utilizing a modulated fan-beam in a scan-rotate geometry RSER (Rotary Scanning Equalization Radiography), as an efficient method for producing exposure equalized mammograms. The image quality of RSER is similar to that attained with the inefficient single beam, raster scanning SER (Scanning Equalization Radiography) geometry. RSER has the potential to be a practical, efficient method for improving the detection of cancer in the dense breast. In this work, we present a theoretical analysis of the imaging properties of the RSER geometry in two regimes defined by the variation of x-ray transmission within the object. For low contrast objects, the imaging geometry was analyzed as a linear system, whereas the high contrast regime was studied by determining the contrast limit at which RSER requires nonphysical (negative) exposure modulation for a breast-like object. The low contrast transfer function of the RSER system is shown to be very similar to that of the SER geometry. We show that RSER enables the use of wide scanning beam of approximately 4 cm and thereby significantly reduces x-ray tube heat loading. Analysis of the high contrast behavior shows that a wide range of object contrasts and sizes can be equalized. For example, RSER can equalize a region of 100% glandular tissue within a 4.0 cm thick compressed breast composed of 100% adipose tissue. Thus, the RSER geometry produces images very similar to the more inefficient SER geometry, and is able to produce entrance exposure distributions appropriate for equalization of the range of contrast typically encountered in mammography.

A method for practical equalization mammography of the radiographically dense breast.

It has been shown that equalization radiography can overcome the well-known problem of limited film latitude encountered in mammography of the radiographically dense breast. Current equalization geometries based on single scanning beam (SER) or multiple-beam techniques approach the heat-loading limits of mammographic x-ray sources and require excessively long scan times. The authors have proposed an alternative geometry for equalization mammography, rotary scanning equalization radiography (RSER), which uses a slot beam in a translate-rotate geometry. RSER provides the simplicity of a single-beam geometry while offering improved tube efficiency over multiple-beam geometries. Numerical simulations and a prototype imaging system are used to show that equalized mammograms exhibiting high contrast throughout the breast can be obtained with a large scanning beam translated over the image at only four scanning angles. These results indicate that RSER is an efficient, simple, and practical means of imaging the dense breast.

The value of vocal function exercises in the practice regimen of singers.

The purpose of this study was to investigate the effects of isometric-isotonic vocal function exercises, practiced regularly for 4 weeks, on parameters of voice production in the healthy singer. A total of 20 university graduate-level voice majors of similar age and vocal training were divided into experimental and control groups, each containing 3 men and 7 women. Each group continued their regular singing practice regimen and the experimental group added the vocal function exercise program. Assessment included acoustic and aerodynamic measures, videostroboscopic ratings, and subjective evaluations. Experimental subjects demonstrated significant improvements in posttest aerodynamic measures of flow rate, phonation volume, and maximum phonation times, suggesting an increase in glottal efficiency.

Role of equalisation mammography of dense breasts.

Parenchymal patterns characteristic of dense breasts are known to degrade the mammographic detection of small breast cancers and microcalcifications. This arises from large variations in exposure of the film, resulting in reduced image contrast over areas of suboptimal exposure. Based on sensitometric measurements of mammograms from a typical patient population, it is shown that over 60% of a typical mammogram in Wolfe's DY classification was found to be exposed suboptimally, suggesting a significant margin for improving mammography for these patients. In order to address this problem, a prototype mammographic version of scanning equalisation radiography (MSER) has been developed, which delivers a patient-specific spatially non-uniform distribution of breast exposure, adjusted to maintain optimal film exposure and contrast over the entire mammogram. Anthropomorphic phantom MSER images show a marked improvement in subjective image quality relative to conventional mammograms, while exhibiting a similar radiation risk. The detection of small microcalcifications and fibrils over clinically significant breast densities is found to be improved by factors eight and four, respectively. Such a system may be clinically practical through the use of multiple-beam equalisation methods with available X-ray tube technology.

Monitoring of 222Rn in Taiwanese hot spring spa waters using a modified electret ion chamber method.

222Rn concentrations in some Taiwanese hot spring spa waters have been monitored using commercially available electret ion chambers (EIC). The use of two EIC units for measuring radon concentrations in the air phase and voltage dependent correction factors for subtracting gamma contributions resulted in improved accuracy.

Long-term effects of instilled mineral dusts on pulmonary surfactant isolated from monkeys.

Experiments were carried out to determine the long-term effect of instillation of 500 mg of generic bituminous, anthracite, quartz, or titanium dioxide (TiO2) dust on the composition of pulmonary surfactant. Dust was instilled in the caudal lobe of the right lungs of female pigtailed macaque monkeys (Macaca nemestrina). The composition of surfactant isolated from cell-free bronchoalveolar lavage (CF-BAL) samples obtained from right lungs (dust exposed) at various times over the following year was compared with that of surfactant isolated from CF-BAL from left lungs (dust free). Little change was seen in the amount of surfactant-associated lipid phosphorus as a result of exposure to dust. Exposure to quartz, anthracite, or TiO2 dust induced a significant increase in the total amount of protein in the surfactant-enriched fraction. The relative amount of specific proteins was also altered: surfactant-associated protein A decreased, and the amount of the heavy and light chains of immunoglobulin molecules (identified by NH2-terminal amino acid sequence analysis) increased. These changes were visible more than a year after instillation of quartz and at least 3 months after instillation of anthracite dust. Despite variation in the responses of the individual animals, the changes observed might serve as an indicator of the severity of the effect of exposure of the lung to mineral dust and/or to pathogens.