ICRP 129 and cone beam computed tomography

La radiologia medica

Background Radiation-induced health risks are broadly questioned in the literature. As cone beam computed tomography (CBCT) is increasingly used in non-dental examinations, its effective dose needs to be known. This study aimed to review the published evidence on effective dose of non-dental CBCT for diagnostic use by focusing on dosimetry system used to estimate dose. Materials and methods A systematic review of the literature was performed on 12 November 2017. All the literature up to this date was included. The PubMed and web of science databases were searched. Studies were screened for inclusion based on defined inclusion and exclusion criteria according to the preferred reporting items for systematic reviews. Results Fifteen studies met the inclusion criteria and were included in our review. Thirteen and two of them examined one and two anatomical areas, respectively. The anatomical areas were: ear (6), paranasal sinuses (4), ankle (3), wrist (2), knee (1), and cervical spine (1). Effective dose was estimated by different methods: (i) RANDO phantom associated with thermoluminescent dosimeters (6), metal oxide semiconductor field-effect transistor dosimeters (3), and optically stimulated luminescent dosimeters (1). (ii) Scanner outputs, namely computed tomography dose index (1) and dose area product (2). (iii) Monte Carlo simulations (2). Conclusion CBCT of extremities, cervical spine, ears and paranasal sinuses was found to be a low-dose volumetric imaging technique. Effective doses varied significantly because of different exposure settings of CBCT-units and different dosimetry systems used to estimate dose.

Polymer Degradation and Stability

Objective: To estimate the absorbed organ dose and effective dose for a wide range of cone beam computed tomography scanners, using different exposure protocols and geometries. Materials and methods: Two Alderson Radiation Therapy anthropomorphic phantoms were loaded with LiF detectors (TLD-100 and TLD-100H) which were evenly distributed throughout the head and neck, covering all radiosensitive organs. Measurements were performed on 14 CBCT devices: 3D Accuitomo 170, Galileos Comfort, i-CAT Next Generation, Iluma Elite, Kodak 9000 3D, Kodak 9500, NewTom VG, NewTom VGi, Pax-Uni3D, Picasso Trio, ProMax 3D, Scanora 3D, SkyView, Veraviewepocs 3D. Effective dose was calculated using the ICRP 103 (2007) tissue weighting factors. Results: Effective dose ranged between 19 and 368 Sv. The largest contributions to the effective dose were from the remainder tissues (37%), salivary glands (24%), and thyroid gland (21%). For all organs, there was a wide range of measured values apparent, due to differences in exposure factors, diameter and height of the primary beam, and positioning of the beam relative to the radiosensitive organs. Conclusions: The effective dose for different CBCT devices showed a 20-fold range. The results show that a distinction is needed between small-, medium-, and large-field CBCT scanners and protocols, as they are applied to different indication groups, the dose received being strongly related to field size. Furthermore, the dose should always be considered relative to technical and diagnostic image quality, seeing that image quality requirements also differ for patient groups. The results from the current study indicate that the optimisation of dose should be performed by an appropriate selection of exposure parameters and field size, depending on the diagnostic requirements.

Oral Surgery Oral Medicine Oral Pathology Oral Radiology and Endodontology, 2008

Objectives. This study compares 2 measures of effective dose, E 1990 and E 2007 , for 8 dentoalveolar and maxillofacial cone-beam computerized tomography (CBCT) units and a 64-slice multidetector CT (MDCT) unit. Study design. Average tissue-absorbed dose, equivalent dose, and effective dose were calculated using thermoluminescent dosimeter chips in a radiation analog dosimetry phantom. Effective doses were derived using 1990 and the superseding 2007 International Commission on Radiological Protection (ICRP) recommendations. Results. Large-field of view (FOV) CBCT E 2007 ranged from 68 to 1,073 Sv. Medium-FOV CBCT E 2007 ranged from 69 to 560 Sv, whereas a similar-FOV MDCT produced 860 Sv. The E 2007 calculations were 23% to 224% greater than E 1990 . Conclusions. The 2007 recommendations of the ICRP, which include salivary glands, extrathoracic region, and oral mucosa in the calculation of effective dose, result in an upward reassessment of fatal cancer risk from oral and maxillofacial radiographic examinations. Dental CBCT can be recommended as a dose-sparing technique in comparison with alternative medical CT scans for common oral and maxillofacial radiographic imaging tasks.

Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics (AIFB), 2017

The aim of the guideline presented in this article is to unify the test parameters for image quality evaluation and radiation output in all types of cone-beam computed tomography (CBCT) systems. The applications of CBCT spread over dental and interventional radiology, guided surgery and radiotherapy. The chosen tests provide the means to objectively evaluate the performance and monitor the constancy of the imaging chain. Experience from all involved associations has been collected to achieve a consensus that is rigorous and helpful for the practice. The guideline recommends to assess image quality in terms of uniformity, geometrical precision, voxel density values (or Hounsfield units where available), noise, low contrast resolution and spatial resolution measurements. These tests usually require the use of a phantom and evaluation software. Radiation output can be determined with a kerma-area product meter attached to the tube case. Alternatively, a solid state dosimeter attached t...

Medical Physics, 2012

Objective: To measure surface skin dose from various cone-beam computed tomography (CBCT) scanners using point-dosimeters.

Radiation Physics and Chemistry, 2020

During the last decade, the development of cone beam computed tomography (CBCT) has led to a large range of imaging methods. CBCT has advantages compared to other extraoral radiographic imaging, but its contribution to radiation dose in patients is a point of concern. This study aims to provide a full understanding and determination of absorbed dose and an estimation of effective dose to the thyroid, bone marrow, salivary glands and brain in patients during CBCT examinations and to estimate the radiogenic risk resulting from radiation exposure. In this study, a total of 157 pediatric and adult patients with different indications were investigated at the dental clinic. All procedures were performed using Planmeca ProMax 3D Max. Sensitive organ equivalent doses were estimated using PCXMC software. Organ equivalent doses were also estimated using PCXMC software. The fixed tube voltage was set to 90.0 kVp, the mean tube current was 12.7.0 mA (range: 8.0 to 14.0) and the mean exposure time was 12.5 ± 1.8 s (range: 12.0-16.0). The overall mean patient effective dose was 150.8 μSv (range: 22.4-210.0). Salivary gland equivalent dose was the highest of all the organs measured as no protective shield was used in these patients. Patient doses were slightly higher compared to those in previous studies. Poor patient protection conditions were noted. Staff training is a vital priority regardless of a low dose of CBCT compared to other imaging modalities.

American Journal of Orthodontics and Dentofacial Orthopedics, 2013

Introduction: With the advent of cone-beam computed tomography (CBCT) scans, there has been a transition toward these scans' replacing traditional radiographs for orthodontic diagnosis and treatment planning. Children represent a significant proportion of orthodontic patients. Similar CBCT exposure settings are predicted to result in higher equivalent doses to the head and neck organs in children than in adults. The purpose of this study was to measure the difference in equivalent organ doses from different scanners under similar settings in children compared with adults. Methods: Two phantom heads were used, representing a 33-year-old woman and a 5-year-old boy. Optically stimulated dosimeters were placed at 8 key head and neck organs, and equivalent doses to these organs were calculated after scanning. The manufacturers' predefined exposure settings were used. Results: One scanner had a pediatric preset option; the other did not. Scanning the child's phantom head with the adult settings resulted in significantly higher equivalent radiation doses to children compared with adults, ranging from a 117% average ratio of equivalent dose to 341%. Readings at the cervical spine level were decreased significantly, down to 30% of the adult equivalent dose. When the pediatric preset was used for the scans, there was a decrease in the ratio of equivalent dose to the child mandible and thyroid. Conclusions: CBCT scans with adult settings on both phantom heads resulted in higher radiation doses to the head and neck organs in the child compared with the adult. In practice, this might result in excessive radiation to children scanned with default adult settings. Collimation should be used when possible to reduce the radiation dose to the patient. While CBCT scans offer a valuable tool, use of CBCT scans should be justified on a specific case-by-case basis.

Radiotherapy and Oncology, 2010

Background and purpose: This study explores methods to reduce dose due to kV-CBCT imaging for patients undergoing radiation therapy. Material and methods: Doses resulting from kV-CBCT scans were calculated using Monte Carlo techniques and were analyzed using dose-volume histograms. Patients were modeled as were CBCT acquisitions using both 360°and 200°gantry rotations. The effects of using the half fan bow-tie and the full fan bow-tie filters were examined. Results: Doses for OBI 1.3 are 15 times (head), 5 times (thorax) and 2 times (Pelvis) larger than the current OBI 1.4. When using 200°scans, the doses to eyes and cord are 0.2 (or 0.65) cGy and 0.35 (or 0.2) cGy when rotating the X-ray source underneath (or above) the patient, respectively. The 360°Pelvis scan dose is 1-2 cGy. The rectum dose is 1.1 (or 2.8) cGy when rotating the source above (or below) the patient with the 200°Pelvis scan. The dose increases up to two times as the patient size decreases. Conclusions: The dose can be minimized by reducing the scan length, the exposure settings, by selecting the gantry rotation angles, and by using the full fan bow-tie whenever possible.

Dentomaxillofacial Radiology, 2014

Cone beam CT (CBCT) is a relatively new imaging modality, which is now widely available to dentists for examining hard tissues in the dental and maxillofacial regions. CBCT gives a three-dimensional depiction of anatomy and pathology, which is similar to medical CT and uses doses generally higher than those used in conventional dental imaging. The European Academy of DentoMaxilloFacial Radiology recognizes that dentists receive training in twodimensional dental imaging as undergraduates, but most of them have received little or no training in the application and interpretation of cross-sectional three-dimensional imaging. This document identifies the roles of dentists involved in the use of CBCT, examines the training requirements for the justification, acquisition and interpretation of CBCT imaging and makes recommendations for further training of dentists in Europe who intend to be involved in any aspect of CBCT imaging. Two levels of training are recognized. Level 1 is intended to train dentists who prescribe CBCT imaging, such that they may request appropriately and understand the resultant reported images. Level 2 is intended to train to a more advanced level and covers the understanding and skills needed to justify, carry out and interpret a CBCT examination. These recommendations are not intended to create specialists in CBCT imaging but to offer guidance on the training of all dentists to enable the safe use of CBCT in the dentoalveolar region. maxillofacial radiology (DMFR), nor is it intended to cover training for operators, technicians or radiographers. It is applicable to all dentists who are not specialized in radiology and takes into account the varying roles a dentist may play in the use of CBCT. Throughout this document, the term "dentist" is used to encompass dental practitioners engaged in general dental care and/or specialist practice other than DMFR.

Dentomaxillofacial Radiology, 2009