Absorbed radiation dose during lateral cephalometric radiography: comparison of screen-film systems and field-size combinations

Various methods have been proposed and investigated in order to reduce radiation exposure in cephalometric radiography. The aim of this study was to determine the radiation dose absorbed by nine specific superficial anatomical regions of the head and neck, in children aged 9 to 17 years, by the use of three combinations of intensifying screens and films and different field sizes. A dental X-ray unit (Ortho Phos, Siemens) was used for the radiographic exposures and the absorbed doses were measured via thermoluminescence dosemeters. The mean doses corresponding to the anatomical regions in question were higher with the first than with the other two techniques (p < 0.05) without the thyroid gland (p > 0.05) and in the third technique were lower than the doses of the other two techniques (p < 0.05) without the thyroid gland and the tip of the nose (p > 0.05).     

A study of absorbed x-ray doses and protection to critical organs of the head and neck during siaglography]

A tissue equivalent phantom was used in the study and absored x-ray doses.It measuring for some important organs of head and neck by four routive sialography methods (panoramic conventional x-ray radioagraphy,tomography,fluoroscope,CT) and also the X-ray absorbed doses of thyroid and len when lead containing loop and spectacles of head containing glass were used for prevention.All the data were processed statistically and a compartive study of absorbed x-ray doses of four sialography methods:Doses of submandibular gland were higher in CT,tomography and fluoroscope among them,CT was the highest indicating that it was superior to other methods for accurately locating that it was superior to other methods for accurately locating the within-gland tumor.Fluoroscope will be use more frequently in clinic,because it can observe the living gland panoramic and normal radiography can be used routinely because they had the minimum doses in measured organs.2.The absorbed x-ray doses of len and thyroid decreased by 93%-% when prevention was taken in CT or fluoroscope,65%-85% doses was decreased in normal radiography or panoramic with prevention.     

Exposure distribution, absorbed doses, and energy imparted for panoramic radiography using Orthopantomograph model OP 5

The absorbed doses and energy imparted for the Orthopantomograph model OP 5 using two different collimators (0.9-1.3 X 33 mm2 and 0.6-0.9 X 39.5 mm2, respectively) were examined at 70 and 75 kV. The absorbed doses were estimated by thermoluminescence dosimetry in a sectioned phantom and by the energy imparted from measurements of areal exposure using a plane parallel transmission ionization chamber. The exposure distribution was surveyed on radiographic film. The anterior part of the parotid glands received the highest absorbed doses (2.4-3.2 mGy) when the wider collimator was used, with a decrease of two to three times when the narrower collimator was used. Other areas received absorbed doses of about 1.0 to 1.5 mGy or below. An increase of the kV from 70 to 75 had a minor influence. The energy imparted for the wider collimator was 0.6-0.8 and for the narrower collimator, 0.4-0.6 mJ.     

Reduction of body doses in rotational panoramic radiography by means of reduced beam width in combination with rare earth intensifying screens

Abstract – The absorbed doses in the body of a Rando-Alderson phantom were measured in rotational panoramic radiography (OP-5) with LiF-700 crystals using conventional intensifying screens and standard collimator, as well as rare earth intensifying screens and a collimator slit of reduced width. The reduction of the absorbed doses obtained by using the latter combination was calculated. The reduction range in different regions was 0–50%. The greatest reduction was obtained in the cranial part of the phantom. In the caudal part little or no reduction was observed, probably because leakage radiation contributes substantially to the absorbed doses in this area. The average dose equivalent was calculated for organs in which measurements were made in several locations. The reduction was about 50% for these organs except for the gonads (8%). Compared to the estimated average annual dose equivalent originating from the natural background radiation sources, the dose equivalent resulting from this X-ray examination was very small except in the thyroid gland. In this organ the dose equivalent from one exposure corresponded to 36 days of natural background radiation, but it could be reduced to 18 days by using rare earth intensifying screens in combination with reduced beam width.     

Reduction of body doses in rotational panoramic radiography by means of reduced beam width in combination with rare earth intensifying screens

The absorbed doses in the body of a Rando-Alderson phantom were measured in rotational panoramic radiography (OP-5) with LiF-700 crystals using conventional intensifying screens and standard collimator, as well as rare earth intensifying screens and a collimator slit of reduced width. The reduction of the absorbed doses obtained by using the latter combination was calculated. The reduction range in different regions was 0-50%. The greatest reduction was obtained in the cranial part of the phantom. In the caudal part little or no reduction was observed, probably because leakage radiation contributes substantially to the absorbed doses in this area. The average dose equivalent was calculated for organs in which measurements were made in several locations. The reduction was about 50% for these organs except for the gonads (8%). Compared to the estimated average annual dose equivalent originating from the natural background radiation sources, the dose equivalent resulting from this X-ray examination was very small except in the thyroid gland. In this organ the dose equivalent from one exposure corresponded to 36 days of natural background radiation, but it could be reduced to 18 days by using rare earth intensifying screens in combination with reduced beam width.     

Dose reduction by field size trimming in rotational panoramic radiography

A substantial dose reduction may be obtained for patients in need of frequent retakes with rotational panoramic radiography by reducing the width and height of the film area irradiated. An electronic timer was connected to the circuit of an Orthopantomograph 5 (Siemens) whereby exposure times could easily be selected in the range 5-15 s. Vertical extracollimation was provided. With the field size reduced to encompass the developing dentition only, about 60% reduction in integral absorbed dose was obtained using standard (Siemens special) screens. With rare earth (Titan HS) screens a reduction of 85% was obtained in integral absorbed dose and absorbed doses to the thyroid gland and eye lens were reduced by 70-79% and 80-89%, respectively. The doses thus obtained were equal to or less than those reported with a single dental film in speed Group D.     

Dose reduction by field size trimming in rotational panoramic radiography

A substantial dose reduction may be obtained for patients in need of frequent retakes with rotational panoramic radiography by reducing the width and height of the film area irradiated. An electronic timer was connected to the circuit of an Orthopantomograph 5 (Siemens) whereby exposure limes could easily be selected in the range 5-15 s. Vertical extracollimation was provided. With the field size reduced to encompass the developing dentition only, about 60% reduction in integral absorbed dose was obtained using standard (Siemens special) screens. With rare earth (Titan HS) screens a reduction of 85% was obtained in integral absorbed dose and absorbed doses to the thyroid gland and eye lens were reduced by 70-79% and 80-89%, respectively. The doses thus obtained were equal to or less than those reported with a single dental film in speed Group D.     

Red bone marrow doses, integral absorbed doses, and somatically effective dose equivalent from four maxillary occlusal projections

Phantom measurements of red bone marrow (RBM) doses, integral absorbed doses, and somatically effective dose equivalent (SEDE) from four different maxillary occlusal projections are presented. For each projection, different combinations of focus-skin distances and tube potentials were compared with regard to the patient's radiation load. The axial incisal view produced the highest patient exposures, with a maximum red bone marrow dose of 122.5 microGy/exposure, integral absorbed dose of 8.6 mJ/exposure, and SEDE values of 39.6 microSv/exposure. The corresponding values from the frontal, lateral occlusal, and tuber views ranged between 4% and 44% of the axial incisal view values for the integral absorbed dose and SEDE values, and between 0.3% and 3% for the red bone marrow doses. Increasing the focus-skin distance from 17.5 cm to 27 cm is accompanied by a 24% to 30% reduction in integral absorbed dose. Increasing the tube potential from 50 kV to 65 kV likewise results in a 23% reduction in absorbed energy.     

拍摄全口根尖片患者吸收X线剂量的研究

目的 测定拍摄全口牙片时人体不同器官吸收的辐射剂量,为相应的防护措施提供客观依据。方法 应用具有完整骨骼的仿真体模详细测定了拍摄全口１４张牙片时脑垂体、眼晶体、腮腺、颌下腺、舌下腺、甲状腺、乳腺、卵巢及睾丸等器官和各牙位照射野中心的皮肤辐射剂量。结果 吸收的辐射剂量：眼晶体为２４９μＧｙ,甲状腺为１２５μＧｙ,甲状腺为１２５μＧｙ,垂体为１１２μＧｙ,腮腺为１５３μＧｙ,颌下腺为６２９μＧｙ,舌下     

Absorbed doses at varying tube voltage in lateral cephalography

Absorbed doses in organs of special interest from lateral cephalography were measured by thermoluminescence dosimetry in a tissue equivalent phantom head. The radiographic examination was performed in a standardized manner by using a carefully collimated radiation field and a near-focus dodger. The actual tube voltages ranged from 63-127 kVp. The absorbed dose was described as a function of tube voltage. In all measurement sites the absorbed dose decreased with increasing tube voltage. This reduction was most obvious in the low tube voltage range. From the results a lowest recommendable tube voltage was given for the different measurement sites varying from approximately 75 kVp (thyroid region) to approximately 100 kVp (parotid region). A high tube voltage was found to be important for a low absorbed dose in different organs in lateral cephalography.     

Effect of long-term, peroral administration of sugar alcohols on man

Certain sugar alcohols (polyols), notably mannitol, sorbitol and xylitol have gained use in food manufacturing for sweetening and technical purposes. These compounds are natural polyols that occur in small amounts in animals and plants. Some sugar alcohols, like xylitol, appear as normal intermediates in the carbohydrate metabolism. Exogenous mannitol, sorbitol and xylitol are metabolized in the human body along pre-existing, physiological pathways. Moderate doses of least xylitol and sorbitol are almost totally absorbed and metabolized, chiefly in the liver cells, thereby eventually contributing to the formation of glucose and liver glycogen. Various slowly absorbed carbohydrates, including sugar alcohols, when taken in orally in large quantities, can give rise to osmotic diarrhea. The available data indicate that the severity of such gastro-intestinal disturbances, induced by large doses of polyols, decrease in the following order: mannitol, sorbitol, xylitol. This osmotic diarrhea resembles that caused by lactose in subjects with restricted or frank lactose intolerance. The quantities of xylitol, for example, required to elicit diarrhea are so high that the consumption of xylitol for dental purposes does not cause any problems in children or adults. Long-term feeding trials and peroral loading experiments on human subjects have been unable to show any clinically significant differences between chronic users of xylitol and comparative human material in factors related to various metabolic functions of the body. These subjects have not shown any delayed or acute reactions which could be distinguished from those caused by the consumption of a sucrose diet. The available clinical data generally suggest that moderate consumption of the above polyols is not harmful to human metabolism.     

Absorbed dose determination for tomographic implant site assessment techniques.

A set of data to compare the absorbed dose delivered by tomographic implant site assessment techniques was generated. Absorbed doses were measured in fourteen anatomic sites from (1) computed tomography scans and (2) a series of tomographic cuts performed on a linear tomography unit. The doses to the thyroid gland, the active bone marrow, the brain, the salivary glands, and the eyes were determined with the use of a tissue-equivalent phantom with lithium fluoride thermoluminescent dosimeters at the appropriate locations.     

Radiation doses and risks in dento-maxillofacial radiology

Radiation doses and risks in dento-maxillofacial radiology are discussed. The basic processes of interaction between X-rays and living tissue are described and the quantities and units used in dose estimates are defined. Experimental values for doses absorbed by various organs/tissues, mainly in the head and neck region, are presented. The effects of proper collimation and shielding on dose values are demonstrated. Examples from the literature are given. The necessity for and methods for radiation protection in dento-maxillofacial radiography are discussed.     

Absorbed doses from temporomandibular joint radiography

Thermoluminescent dosimeters were used in a tissue-equivalent phantom to measure doses of radiation absorbed by various structures in the head when the temporomandibular joint was examined by four different radiographic techniques--the transcranial, transorbital, and sigmoid notch (Parma) projections and the lateral tomograph. The highest doses of radiation occurred at the point of entry for the x-ray beam, ranging from 112 mrad for the transorbital view to 990 mrad for the sigmoid notch view. Only the transorbital projection a radiation dose to the lens of the eye. Of the four techniques evaluated, the lateral tomograph produced the highest doses to the pituitary gland and the bone marrow, while the sigmoid notch radiograph produced the highest doses to the parotid gland.     

Evaluation of skin dose in a low dose spiral CT protocol.

AIM: The authors evaluated radiation and skin doses absorbed by the eye lens, as well as the parotid and thyroid glands, during a low dose maxillary spiral computed tomography (CT). METHODS: Three spiral CTs were carried out, one after the other, changing from time to time MAS, pitch factor, Kv and consequently, CTDI/Vol, until the minimum values detectable by the equipment were reached (MAS 28, Kv 80, CTDI/Vol 2.5, Pitch 1). The quality of the images was evaluated on the grounds of being able to visualise the anatomic structures considered. The amount of radiation effectively absorbed by the soft tissue (skin doses) can be measured with the help of dosimeters placed at the level of eye lens, parotid and thyroid glands. The spiral CTs were performed with a Siemens 16 CT sensation machine, using a tissue equivalent Head-Neck RT Humanoid phantom. RESULTS: From the results of this study, it appears possible to obtain high quality images, useful for diagnosing numerous skeletal pathologies in orthodontics, reducing of about 90% the radiation dose per unit of volume and, at the same time, reducing the soft tissue (skin) dose of about 85% when compared to pre-established settings. CONCLUSION: The authors conclude their research emphasizing the possibility of applying low dose protocols, not only in orthodontics but in any dental field, whenever a spiral CT is needed for a more detailed diagnosis.     

Radiation absorbed doses in cephalography

Radiation absorbed doses to different organs in the head and neck region in lateral (LAT) and postero-anterior (PA) cephalography were investigated. The doses were measured by thermoluminescence dosimeters (TLD) on a tissue equivalent phantom head. Lanthanide screens in speed group 4 were used at 90 and 85 kVp. A near-focus aluminium dodger was used and the radiation beam was collimated strictly to the face. The maximum entrance dose from LAT was 0.25 mGy and 0.42 mGy from a PA exposure. The doses to the salivary glands ranged between 0.2 and 0.02 mGy at LAT and between 0.15 and 0.04 mGy at PA exposures. The average thyroid gland dose without any shielding was 0.11 mGy (LAT) and 0.06 mGy (PA). When a dodger was used the dose was reduced to 0.07 mGy (LAT). If the thyroid gland was shielded off, the dose was further reduced to 0.01 mGy and if the thyroid region was collimated out of the primary radiation field the dose was reduced to only 0.005 mGy.     

免疫乳清对葡萄糖基转移酶活性的影响

目的 了解免疫乳清对变形链球菌葡萄糖基转移酶（ｇｌｕｃｏｓｙｌｔｒａｎｓｆｅｒａｓｅ,ＧＴＦ）活性的影响。方法 免疫乳清来源于ＧＴＦ过表达株Ｂ－２９－３３免疫孕牛中获得的牛奶。对照乳清从未免疫孕牛中获得。用ｇｔｆＢ基因缺陷株Ｂ－２９吸收免疫乳清中的抗体获得免疫吸收乳清。采用蒽酮定糖法检测３种乳清在５０、７０及９０μｌ３种剂量条件下对ＧＴＦ合成水不溶性葡聚糖的影响。结果 对照乳清具有增强酶活性的作用     

Absorbed doses from intraoral radiography with special emphasis on collimator dimensions

Thermoluminescence dosimeters were used in a phantom head and on patients to measure the absorbed dose to organs of special interest from full surveys with intraoral films (20 exposures) and single bitewing exposures. Two x-ray machines were used, operating at 65 kVp. The apertures of the circular tube collimators had diameters of 55 mm and 48 mm. Rectangular (35 mm X 44 mm) tube collimators were also used. The distance from the x-ray focus to the open end of the collimators (FSD) was 0.20 and 0.35 m. Exposure values for Kodak Ultra-Speed film (speed group D) were used. The maximum skin dose measured from the full surveys decreased by 25 per cent on changing from the circular to the rectangular apertures. Using 0.35 m FSD and rectangular collimator the maximum skin dose was 13 mGy. The absorbed doses to the salivary glands and the thyroid gland were significantly reduced on changing from circular to rectangular apertures. The doses in the central part of the parotid and the thyroid glands were then 0.5 and 0.12 mGy, respectively, from a full survey with 20 intraoral films. With a leaded shield the thyroid dose was reduced to 0.05 mGy. All dose values could be further reduced by 40 per cent by using Kodak Ektaspeed film (speed group E).     

Dose reduction by direct-digital cephalometric radiography.

Patient radiation exposure was determined for conventional and direct-digital cephalometric radiography. An anthropomorphic phantom was positioned to expose lateral cephalographs from the patient's left side. The conventional radiographs were exposed with a Siemens Orthophos C unit (77 kV, 14 mA, 0.5 s) and a film-screen system of a relative speed of 400. The direct-digital radiographs were exposed with a Siemens Orthophos DS Ceph (73 kV, 15 mA, 15.8 s). A set of 108 thermoluminescence detectors (TLDs; Bicron STI/Harshaw, Solon, Ohio) was used for dose measurements. For each measurement, 84 TLDs were placed at the surface of the head and neck, as well as inside the phantom, at anatomically relevant positions. The remaining detectors were employed for calibration purposes and quality control. The highest absorbed doses were recorded for the conventional technique at the skin of the left parotid region (132 microGy), in the left parotid gland (103 microGy), and in the ocular lens of the left eye (81 microGy). Digital cephalometry resulted in an absorbed dose about 2 times lower than the dose received by the conventional technique. The effective doses had the same relation (conventional 2.3 microSv; digital 1.1 microSv). The results demonstrate that direct-digital cephalometric radiography cuts the patient's dose in half compared with the conventional screen-film technique. Direct-digital cephalometry is more advantageous than the conventional technique from the perspective of radiation protection.     

Side effects of triazolam in children

PURPOSE: This study examined the incidence of side effects occurring with three doses of orally administered triazolam in children undergoing restorative dental procedures. METHODS: Thirty children, aged 39-81 months, participated in the study. The children were pretested for gait ataxia, amnesia, visual acuity, stereoscopic depth perception, and diplopia during a screening session. In a subsequent appointment, children received one of three triazolam dosages (0.005, 0.015, and 0.030 mg/kg) prior to dental treatment. Dosage assignment was random and double blind. Each child received a single triazolam dosage. Tests for gait ataxia, amnesia, and visual disturbances were repeated following drug administration. RESULTS: The proportion of children experiencing ataxia, amnesia, and diplopia increased with increasing triazolam dosages. The 0.030-mg/kg triazolam dosage impaired visual acuity and stereoscopic depth perception. CONCLUSION: Triazolam produces ataxia, amnesia, and diplopia in a dose-dependent manner in children.