The Feasibility of the Pa Projection for Tomography of the Petrous Bone (original) (raw)
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Computed Tomography of the Petrous Bone: Particularities in Children
Advances in Molecular Imaging, 2018
Like any organ in children, the ear has particular anatomical features that are well shown in imaging. The petrous bone computed tomography (CT) is a valuable tool for diagnosing ear pathologies and evaluating surgical possibilities. In children, the ear has the peculiarity of having the morphology and size of adults, and the only difference resides in the components of the middle and inner ear related to the growth of the temporal bone and the state of ossification which are progressive with age. Some aspects of growth can simulate pathology and must be known. The pneumatisation of the temporal bone occurs gradually after birth and in several outbreaks until adulthood. The external auditory canal, the internal auditory meatus and the petromastoid canal progressively reach the adult aspect because of the growth of the petrous bone. This work aims to highlight the particularities of the petrous bone CT in pediatrics, since it has become widely used in the exploration of malformations, trauma, infectious complications of the ear and in the assessment of deafness.
Pediatric Radiology
Background Various imaging modalities, such as multi-detector computed tomography (CT) and cone beam CT are commonly used in infants for the diagnosis of hearing loss and surgical planning of implantation hearing aid devices, with differing results. Objective We compared three different imaging modalities available in our institution, including a high-class CT scanner, a mid-class CT scanner and an angiography system with a cone beam CT option, for image quality and radiation exposure in a phantom study. Materials and methods While scanning an anthropomorphic phantom imitating a 1-year-old child with vendor-provided routine protocols, organ doses, surface doses and effective doses were determined for these three modalities with thermoluminescent dosimeters. The image quality was evaluated using the signal difference to noise ratio (SDNR) and the spatial resolution of a line-pair insert in the phantom head. The dose efficiency, defined as the ratio of SDNR and effective dose, was als...
Reduction in Lens Dose in Temporal Bone Computed Tomography by Modification of Scanning Plane
Hong Kong Journal of Radiology, 2016
Objectives: To evaluate the radiation dose reduction to the lens by modifying the scanning plane to exclude the orbit in temporal bone computed tomography (CT). The effect on diagnostic image quality was also evaluated. Methods: Radiation dose reduction was evaluated using a phantom head and calibrated thermoluminescent dosimeters. Image quality was assessed in 34 patients. Two radiology fellows independently reviewed the image and assessed the image quality of 20 temporal bone structures. The image quality was scored on a 4-point scale and analysed with Mann Whitney U test. Results: We demonstrated a 31.4% to 46.1% dose reduction to the lens by excluding the orbit in the scan field. The dose-length products before and after the modification were comparable (p = 0.267). None of the assessed temporal bone structures demonstrated any significant difference in image quality (p > 0.05). Conclusion: Modification of the scanning plane in temporal bone CT can reduce radiation dose exposure to the lens and preserve the diagnostic image quality. This protocol should be considered to minimise the radiation exposure to patients.
American Journal of Neuroradiology, 2008
BACKGROUND AND PURPOSE: For CT scan planning, scan projection radiographs (SPR) are used. Tube tension and current for head SPR can be reduced to a minimum because of the small head diameter and because only high-contrast structures need to be visualized for planning. The goal of this study was to investigate SPR of the head in respect to effective doses, the influence of dose-reduction measures, and comparison with conventional x-ray. MATERIALS AND METHODS: Entrance doses for default and minimal settings were measured on a LightSpeed Ultra CT scanner and on conventional x-ray equipment. Effective doses for different scanning fields of the head were calculated for an adult, a 10-year-old child, and a neonate by using the commercially available software PCXMC. RESULTS: Depending on projection and technique, SPR effective doses for adults were 1.9-27.7 Sv; for the 10-year-old child, 2.1-31.1 Sv; and for the neonate, 5.2-97.2 Sv. Doses with the tube under the table were 1.3-3.4 times lower. Doses for conventional radiography were higher than SPR doses for adults and partially lower for children. CONCLUSIONS: Depending on the scanning technique, effective doses for head SPR can differ up to 17-fold. The dose is significantly reduced by lowering tube voltage and current, by positioning the tube under the table, and by keeping the thyroid out of the scan or by protecting it with a lead collar. Compared with the conventional x-ray technique, SPR doses tend to be lower due to x-ray beam characteristics.
Pediatric Phantom Dosimetry of Kodak 9000 Cone-beam Computed Tomography
2017
PURPOSE The purpose of the study was to evaluate the radiation dose of the Kodak 9000 cone-beam computed tomography (CBCT) device for different anatomical areas using a pediatric phantom. METHODS Absorbed doses resulting from maxillary and mandibular region three by five cm CBCT volumes of an anthropomorphic 10-year-old child phantom were acquired using optical stimulated dosimetry. Equivalent doses were calculated for radiosensitive tissues in the head and neck area, and effective dose for maxillary and mandibular examinations were calculated following the 2007 recommendations of the International Commission on Radiological Protection (ICRP). RESULTS Of the mandibular scans, the salivary glands had the highest equivalent dose (1,598 microsieverts [μSv]), followed by oral mucosa (1,263 μSv), extrathoracic airway (pharynx, larynx, and trachea; 859 μSv), and thyroid gland (578 μSv). For the maxilla, the salivary glands had the highest equivalent dose (1,847 μSv), followed closely by o...
Journal of Medical Physics, 2020
Globally, 480 million diagnostic dental examinations are performed yearly. [1] Although the radiation dose associated with dental radiography is comparatively less, the patient may undergo a dental radiography diagnosis process many times during their life span. While considering the health effects associated with dental radiography, the cumulative doses have to be estimated. [2] Diagnostic reference level (DRL) is a tool used to optimize the radiation exposure to a level appropriate for the medical imaging task. DRLs can be used for all modes of diagnostic radiology. Several methods have been used for assessing the panoramic reference level. [3-12] Dose width product method used by Napier [3] can be related to dose area product (DAP) by multiplying it with the beam height. Lee et al. [13] and Doyle et al. [14] used a solid-state dosimeter for dose measurements in panoramic radiography. Establishing reference levels for dental radiography will ensure a safer diagnosis procedure from the patient's viewpoint. Many radiographers and dentists knew that optimization of the exposure parameter is a key tool for dose reduction. Thus, a reference dose level is required for safe practice. It is an effective method for the significant reduction in collective dose, especially for repeated procedures and in the procedures containing more radiosensitive patients, like children. The present work, initiated by PSG Institute of Medical Sciences and Research in consultation with and grant from the Atomic Energy Regulatory Board (AERB), is a logical extension of the previous study, [15] conducted for the adult panoramic procedures in Tamil Nadu as a part of the establishment of national DRL for dental radiography for the country. Thus, the objective of our study was to calculate DAP for pediatric panoramic radiography to propose DRL and compare it with other country DRL. MaterIals and Methods To establish a regional DRL, it is necessary to sample as many dental hospitals/clinics as possible in the region. The hospitals Aim: The current work aims to calculate dose area product (DAP) and to determine regional diagnostic reference level (DRL) for pediatric panoramic radiography in Tamil Nadu. Materials and Methods: In this study, DAP was calculated after finding the product of air kerma on the detector side of scanner with the corresponding exposed area. The obtained DAP values were further analyzed, and DRL was calculated using Microsoft Excel. The study was carried out with routine pediatric exposure parameters. Results: The obtained mean, range, and third quartile values for pediatric panoramic radiography are found to be 65 mGycm 2 , 11-148 mGycm 2 , and 82 mGycm 2 , respectively. The proposed DRL is comparable with the other countries' DRL. Conclusion: Based on the results of the present study, it was observed that there exists a wide difference in mean doses among the panoramic scanners. The variation in radiation doses between the clinics/hospitals and similar scanners suggests a large potential for optimization of panoramic procedures.
A comparison of the effective dose from scanography with periapical radiography
Dentomaxillofacial Radiology, 2002
Objectives: To compare organ and eective doses from analogue scanographic and periapical radiography. Methods: Thermoluminescent dosimeters (TLD-700) were inserted in the parotid glands (bilateral), submandibular glands (bilateral) and bone marrow (left ascending ramus) of three human cadavers. Dosimeters were also attached to the skin, thyroid gland and lens of both eyes. Central, left lateral and left posterior scanograms were obtained with a Cranex Tome 1 (Soredex, Helsinki, Finland) multimodal imaging system. A similar procedure was applied for periapical radiographs of the midline, left lateral and left molar regions using E-speed ®lm both with and without rectangular collimation. Organ and eective doses were calculated for scanograms and periapical radiographs. Results: The eective doses for the scanograms were 0.001 mSv (central), 0.011 mSv (lateral) and 0.015 mSv (posterior). The eective doses for periapical radiographs were 0.001 mSv (anterior), 0.001 mSv (lateral) and 0.003 mSv (posterior) for rectangular collimation and 0.001 mSv (anterior), 0.002 mSv (lateral) and 0.005 mSv (posterior) for round collimation. Conclusions: When a larger area of the upper or lower jaw needs to be visualised, scanograms might be considered as an alternative to periapical radiography since the eective dose is lower.
Dose evaluation in paediatric patients undergoing skull examinations
Radiation Physics and Chemistry, 2022
This study aimed to estimate the incident air kerma in chest X-ray examinations, for lateral (LAT) and anteriorposterior (AP) (together with posterior-anterior (PA)) projections, in one of the largest paediatric hospitals in Brazil, and to compare these with the results obtained in a general hospital of the same city. The dosimetric results were analysed along with the patient characteristics and radiographer strategies. The examinations of 225 (119 male and 106 female) patients were studied and 389 X-ray scans (200 AP/PA projections and 189 LAT projections) of paediatric patients were acquired. For analysis of the results, the patients were divided into the following age groups: 0-1 y, 1-5 y, 5-10 y, and 10-15 y. Patient's thickness can be determined from age, height or weight with an uncertainty of 20-30%. In different hospitals, the difference in patient's thicknesses between the same age groups can reach 25-55%. A minimal correlation between the patient dose and thickness was observed, with a 4-fold difference in the dose for patients of the same thickness. By standardizing radiological protocols, it should be possible to keep the dose within intervals of 50-100 μGy for LAT projection and 40-80 μGy for AP/PA projection.