12 conducted on a particular body region, based on some indication and from some special examination types. The DRLs for pediatric CT-examinations are proposed and are based on patient data of over 750 patients in 4 university hospitals. Two indications for head CT, four for thorax, two for abdomen and two for whole body CT were considered. Methods: The DRLs for adults and part of the proposed pediatric DRLs for different age groups are proposed according to the third quartile approach. For the other pediatric examinations, the DRLs are in terms of patient weight using a DRL curve. Results: The new partially indication-based DRLs for adult CT-examinations came into effect on June 2013 and are given as CTDIvol and DLP values. On average, the DRLs for a particular body region dropped approximately 20% from the previous DRLs. Concerning the pediatric DRLs, for all four indications selected for thorax CT (angiography, infection, trauma, tumour), the same DRL is proposed. For head CT two different DRLs are proposed (“head routine” with higher DRLs and “ventricular size” with lower DR. 5.9. Iterative reconstruction methods in computed tomography Presenter: Robert Miner, Michener Institute CE, Canada Authors: Robert Miner Introduction: Filtered back projection is the dominant computed tomography image reconstruction method used today, though the use of other methods such as iterative reconstruction is increasing. Iterative reconstruction techniques for computed tomography image reconstruction offer improved image quality, lower image noise and lower patient radiation dose. Methods: Current IR methods will be compared and contrasted. Performance metrics (dose reduction, image quality, image noise and reconstruction times) gained from patient studies, phantom studies and manufacturers product information are discussed. Results: Iterative image reconstruction can offer significant dose reduction, low image noise and quality images at full or reduced dose levels. Most iterative reconstruction methods require increased image processing times when compared to filtered back projection methods. 5.10. The possibility of performing Dose Analysis using “Radiation Exposure Repository” on retrospective CT data in a mid-size hospital Presenter: Ting Hei Edward Wong, Hong Kong Sanatorium & Hospital, Hong Kong Authors: Wong Ting Hei Edward, Gladys Lo, Ben Yu, May Chiu Introduction: The growth of CT has been cited as the fastest imaging technology used in human medicine. The associated ionizing radiation dominates the growing source of population-wide iatrogenic ionizing radiation exposure. The community becomes aware of the trend particular when incidences of overdose to patients due to improper techniques are publicized. When dose monitoring methods are developed and implemented, institution-specific workflow and vendor-specific technologies happens to be significant barriers. As such, it is difficult for imaging centers to participate in centralized dose registry like ACR’s Dose Index Registry. This study will make use of the automatic extraction function of “Radiation Exposure Repository (RER)” on dose summary pages of > 3000 CT examinations collected from a mid-size hospital and explore the possibility to build a Dose Reference Level Registry in a mid-size institution setting. Methods: A self-developed dose monitoring software called “RER” was launched. K factor conversion table based on body parts was utilized to calculate the Effective Dose by multiplying with the exam DLP. Dose data within 3 months are collected and verified. Results: Diagnostic Reference Level of different examinations are acquired. There are some Dose summary page recognition errors and these are investigated for further improvement of the software. As we have 3 CT machines in our institution, DRL is useful to compare examinations done with different machines and provide a good starting point for machine selection. DRL give us a clearer picture of what is present standard which is essential for new machines or new protocol evaluation in the future. 5.11. The Study of Automatic kV Selection for Radiation Dose Reduction in coronary CT angiography Presenter: Katsura Egami, Department of Radiology Yokohama Sakae Kyosai Hospital in Japan Authors: Katsura Egami, Eiji Yasuda, Takae Aoki, Kenichi Hirano, Keiichiro Suzuki, Mitsuyuki Takahashi Introduction: Practical implementation of lower kV in CT for dose reduction has been hampered by the difficulty in predicting the proper kV and mAs setting for each patient. Our goal is to assess the performance of automatic kV selection tool in reducing radiation dose in Cardiac CT angiography. Methods: 1601patiens underwent the CTA, expect for using CAREkV was 647patients, 954patiens CTA were performed using an automatic kV selection tool. Three radio technologist evaluated the image sharpness, noise, artifacts. Dose savings were calculated. Results: A overall dose reduction of 54.8% (DLP) from the reference 120 kV protocol was achieved (prospectivescan:59.1%, retrospective scan 27.3%). 100% exams were considered to be of the similar quality as previous CTA exam. The automatic kV selection tool provides an efficient and quantitative way to guide the selection of the most dose-efficient kV in CTA. 5.12. Clinical self-assessment and changes in pelvic imaging and in patient dose by using higher kVp setting: evaluation in one Finish radiology department in Medical Imaging Centre of Southwest Finland Presenter: Jarno Huhtanen, Medical Imaging Centre of Southwest Finland Authors: Huhtanen Jarno, Paasio M., Erjomaa P., Tiensuu J., Järvinen J., Hartikainen M. Introduction: Recent advances in plain film imaging has seen a shift from film-screen (FS) imaging to computed radiography (CR) and digital radiography (DR). Many studies have outlined the possibility for dose savings after FS imaging mostly because of the DR capability for wider dynamic range than FS imaging. Also the reverse is true leading to possibility for dose creep in DR. In DR imaging the importance of dose indicators is essential for radiographers to follow after examinations avoiding dose creep phenomenon. In every examination the ALARAprinciple should be followed and importance of using dose saving methods in DR. Dose saving methods include e.g. filtration, collimation, using appropriate kVp and mAs combination and SID. Doses do vary in different body parts including dose saving methods. Doses can be estimated either using entrance surface dose (ESD) or dose area product (DAP). DAP is useful in everyday practice because it’s easily evaluated after each examination. DAP measurement varies on different manufacturers and can be measured e.g. in mGycm², μGycm² or μGm² so caution is needed if evaluated DAP value between two different systems. Pelvic imaging is an examination that leads to greater radiation dose for patients in DR imaging. Also in pelvic imaging primary radiation is in the field of reproductive organs of male and female so more caution should be used in radiation protection. Many studies have outlined the importance for dose reduction in pelvic imaging. The purpose of this study is to present dose saving method for pelvic imaging (AP projection) in one department in Medical Imaging Centre of Southwest Finland by using higher kVp setting. Methods: Patients’ were selected randomly. Standard patient orientation was used and higher kVp (N=42,n=32) was used. Patient weight(kg), height(cm) and dose(DAP dGycm²) were collected and IQ was evaluated by radiologist (N=1).BMI and dose were compared. Results: From the 32 images conducted with 96 kVp only three (3) were labelled as "not good" and one being marked as diagnostic. None of the three”not goot” resulted in rejection of the image. In BMI and DAP comparison with 85kVp and 96kVp the latter resulted in lower doses for patients’ in Pelvis imaging. No significant reduction in IQ was detected so higher kVp is now being used. Knowledge and assessment about doses and dose-creep is important in DR imaging and in radiographers’ work.
ISRRT | Book Of Abstracts
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