SS 1814 - Getting the radiation dose as low as possible
Positioning for a conventional skyline patella projection: evaluation of torso position and its relationship with eye lens and thyroid dose
Purpose: Numerous techniques exist for
acquire a skyline projections of the knee. Within these techniques
it is common for the x-ray field to be directed towards the eyes
and thyroid. The position of the torso may play a role in the dose
received to these organs and this was investigated.
Methods and Materials: A full body adult anthropomorphic phantom was positioned supine for a conventional skyline projection, the torso at 90 degrees in relation to the hip joint. Data for surface skin dose was recoded using a solid state dosimeter at the level of the eyes and thyroid gland. The angle of the torso was then adjusted in 15 degree increments and the phantom was re-imaged. Dose measurements were recorded and this continued until the torso angle was 180 degrees.
Results: When moving from 90 degrees to 180 degrees the dose to the eyes and thyroid was shown to increase, peaking at 135 degrees for the eyes and 105 degrees for the thyroid and then fell. Dose differences ranged from 0.0 to 0.168 microGy for the lens of the eye and 0.0 to 1.3 microGy for the thyroid, between torso positions.
Conclusion: Torso position has been shown to effect the skin dose at the eye and thyroid levels during traditional skyline knee projections. Further work is needed to understand the effects of different exposure factors and also across a range of technique variations.
Purpose: Although diagnostic X-ray
examinations provide great benefits their use carries a small but
not insignificant risk. For some radiographic examinations lead
rubber shields are available to limit exposure. The use of lead
rubber shields often varies between countries, departments,
radiographers and can depend on the patient. The aim of this study
was to evaluate the utility of a lead rubber shield in paediatric
patients undergoing upper limb radiography.
Methods and Materials: A full body paediatric anthropomorphic phantom was position for an antero-posterior (AP) elbow examination and exposed to ionising radiation using standard acquisition parameters. The skin dose was measured at five different anatomical locations (eyes, thyroid, flank and testes). Lead rubber was then placed over the pelvis and abdomen and the phantom was re-imaged. For each situation (with/without shielding) the exposure factors were sequentially increased.
Results: The skin dose received at the orbit, right flank and testes increased with increasing exposure factors when no shielding was applied. When shielding was applied no skin dose was measured at either the flank sites or testes for any exposure factor combinations. Eye and thyroid does were marginally higher when shielding was applied.
Conclusion: Secondary lead rubber may provide an option for reducing scattered radiation to the abdomen and pelvis during skeletal radiography in paediatrics. A more detailed understanding of the effects of this intervention on all organs and tissues is essential.
The impact of paediatric computed tomography tube current and tube voltage modulation intensity in organ dose and image quality
Purpose: Taking into account that head and
chest Computed Tomography (CT) examinations are the most frequently
performed in paediatric the aim of this study is to analyse the
impact of the different tube current and tube voltage modulation
intensities in dose values and image quality.
Methods and Materials: Head and trunk CT examinations (n=22) were performed in a Siemens® Somatom Definition AS CT scanner (64 detector row) using a 5 years old paediatric anthropomorphic phantom (ATOM-705-CIRS). A thee channel Patient Skin Dose (PSD Unfors) detector (right eye lens, the left mammary gland and gonads) was used to analyse the organ dose (μSv). The CT dose values in terms of CT Dose Index (CTDIvol - mGy) and Dose Length Product (DLP - mGy.cm) were directly collected on the CT scanner. Objective image analysis was based on the image noise measured in homogeneous regions of interest. Phantom quality control kit images were subjective analysed by 3 radiographers with more than 10 years of experience.
Results: The combination tube current and tube voltage modulations allowed examination dose reduction of 19 % and 75 % for head and trunk CT, respectively. The organ dose decreased 46 % and 72 % for the same procedures. No significant differences were founded for dose values and image noise using the different modulation intensities in head and trunk paediatric CT examinations.
Conclusion: Considering the results for dose values (examination and organ) and image quality, the average modulation intensity was considered the most suitable for head and trunk CT examinations.
Purpose: To assess the entrance skin dose
reduction in the eye lens and thyroid by using radiation
protections in orthopantomography exams, in adults.
Methods and Materials: In this experimental quantitative research, a full body anthropomorphic phantom for radiographic training was placed in the orthopantomography equipment, according to the correct positioning criteria. An optically stimulated luminescence (OSL) dosimeter was placed in the left eye and another was placed over the thyroid region. Five radiation expositions with standard parameters were done. The dosimeters were replaced and 1 lens barium protection (equivalent to 0.125mm of lead) and 1 thyroid lead protection (0.5mm) were appropriately placed, outside the region of interest. Five radiation expositions with standard parameters were repeated.
Results: Without radiation protection, the radiation dose was 0.022 mGy in the lens and 0.013 mGy in the thyroid. With the lens barium protection and the thyroid lead protection, radiation doses were 0.034 mGy and 0.009 mGy, respectively. So, the use of lens barium protection increases the radiation dose in the lens by 54.5% and the use of thyroid lead protection reduced the radiation dose by 30.8%.
Conclusion: The use of thyroid lead protection is highly recommended since it can reduce the radiation dose in this radiosensitive organ during orthopantomography exams, attending the ALARA principle. Nonetheless, the use of lens barium protection is not recommended once a dose increase was observed in this organ.
An investigation of how to improve recall and awareness of radiation dose levels associated with cardiovascular interventional procedures
Purpose: Staff awareness of cardiovascular
(CV) interventional radiation dose is essential. This study tested
a protocol involving real-time recall and review of procedural
dose, evaluating its impact upon staffs’ awareness level of
Methods and Materials: A pre-intervention survey (22 questions) was completed by radiographers (n=29) and cardiologists (n=15) in 3 centres (2 adult/1 paediatric). A “Record and Report” intervention was implemented for a two-week period. A poster portraying agreed reference levels for common CV interventional procedures (adult/paediatric) was displayed at CV exposure consoles. Following procedures, radiographers verbally informed clinicians of dose/procedure time. Clinicians classified procedures as routine, slightly complex, complex. Verbal confirmation of the procedural dose as low, comparable or high compared to displayed references was affirmed. A post-intervention survey determined the impact on recall/awareness of dose.
Results: 31 % of participants stated increased awareness of dose levels, 21 % reporting increased radiation safety culture in their CV suite. Post-intervention, 50 % correctly ranked the four most common procedures according to average doses, a 5 % improvement noted post-intervention. 59 % stated dose responses closer to provided reference values post-intervention, a 23 % increase on pre-intervention figures. Clinicians and radiographers reported increases in dose discussion (55%), 73 % reporting that consideration of high/middle/low dose had a positive impact on their practice. 54 % stated they would make changes to build into their own practice in the future.
Conclusion: Overall, cardiac clinicians and radiographers benefited from the “Record and Report” intervention. Implementation of this intervention as routine practice requires further review and this is recommended.
Purpose: To investigate the impact of
additional copper filtration on dose and image quality for adult
chest radiography. Limited literature incorporates digital imaging
technology and the impact of copper filtration tested on both
anthropomorphic phantoms and patient cohorts.
Methods and Materials: Based on anthropomorphic phantom (PBU-60) findings which tested 38 potential imaging combinations derived from current Slovenian practice (10 centres) optimal exposure parameters were determined for adult chest imaging; postero-anterior projection, these were 125 kV, with lateral chambers selected, SID 180 cm and additional 0.2mm Cu filtration. These experimental imaging parameters were then applied to 100 patients, with a second group of patients (n=100) imaged using current practice: 150 kV, with lateral chambers selected, SID 180 cm and additional 0.1mm Cu filtration. A cohort of the patients (n=10) were imaged with both parameters, at two separate outpatient clinic reviews within a 3 month time frame. This subset of patient images was reviewed by three radiologists who performed visual grading analysis to facilitate visual characteristic comparisons.
Results: No statistically significant difference was found in BMI between two groups or in DAP measurement (p=0.552). A statistically significant difference (p=0.018) in image quality was noted in favour of the current imaging parameters. No significant differences were founded for global radiologist acceptability and fair inter-observer agreement (K=0,391) was verify.
Conclusion: Anthropomorphic phantom experiments identified optimal imaging protocols based on dose and SNR/CNR findings. When tested on a patient cohort image quality was reduced compared to current practice. This study highlights the importance of patient imaging in optimisation research.
Purpose: To assess the viability of bismuth
breast shield in thorax CT scans.
Methods and Materials: Dose measurements on phantom (Cardinal Health 76 415) with an ionization chamber were performed with and without bismuth breast protection and in different configurations using the routine thorax CT protocol. Image quality control tests were performed using the phantom (Gammex 464) with and without bismuth breast protection in different configurations.
Results: In all measurement with bismuth protection (no sponges) we observed dose decrease by 22.6%, 19.9% with protection (one sponge), 17.6% with protection (two sponges) and 28.2% with protection coupled to the gantry. Regarding the image quality, with bismuth protection, these have improved when compared to scans with and without sponges.
Conclusion: We obtained acceptable results for both image quality and dose reduction in the phantom. It´s appropriate to implement this protection configuration coupled to the gantry as a protective measure of patients in thorax CT scans.
Does radiation awareness of CT technologists change, when a dose monitoring software is used for real-time monitoring of patient dose?
Purpose: Radiation protection is an
important part of quality assurance in radiology department and can
be ensured by a patient dose monitoring software. The purpose of
the present study was to evaluate whether real-time monitoring of
patient dose increases dose awareness of computed tomography
Methods and Materials: Study was split in 2 periods: in period 1 (p1) dose monitoring software ran in the background, in period 2 (p2) technologists were instructed to check software for dose alerts (dose values above diagnostic reference levels) after each scan (=real-time dose monitoring of patient dose). Dose data from 2 scanners (clinical routine CT, mainly out-patients; emergency CT, mainly emergency/intensive care patients) was compared in both periods using chi-square tests.
Results: Total of 6,413 scans were performed (p1=3,214; p2=3,199) and 330 alerts occurred (p1=210; p2=120). Significantly more alerts were detected on clinical routine CT in p1 (p<0.001), while no difference between scanners was evident in p2 (p=0.135). Most dose alerts were due to overweight (p1=35%; p2=49%), patient miscentering (p1=45%; p2=23%), and scan repetition (p1=10%; p2=14%). Overall, number of alerts significantly declined in p2 (p<0.001). Miscentering was more often seen on clinical routine CT and significantly decreased in p2 on both scanners and for both scanners together (p<0.05). Relative values of dose notifications from overweight or scan repetition were higher in p2, but differences were not significant (p>0.05).
Conclusion: Real-time monitoring of patient dose with dose monitoring software increases CT technologists’ dose awareness, thereby leading to decline of dose alerts due to human error.
Purpose: To quantify the scatter radiation
exposure from mobile x-ray examinations and determine what
radioprotection procedures should be adopted in order to adequately
protect both radiographers and patients.
Methods and Materials: A survey of technical parameters used in the mobile x-ray examinations was performed using a sample of 199 patients to determine the average parameters (77kVp and 2.5mAs). Using these parameters, quality control of the mobile equipment was made with a semiconductor detector (Unfors Xi). Then, 163 exposures were made using a full body anthropomorphic phantom in 3 different configurations: (1) chest AP projection in supine position and (2) semi-sitting position, and (3) tangential projection of the abdomen in supine position. The scattered radiation was measured considering different combinations of voltage, current-time product, angle, height and distance of the dosimeter (Atomtex AT1123) to the anatomical region under study.
Results: Considering the legal dose limits for occupational radiation exposures, to distances less than 1 meter, the dose limit for exposed workers was not exceeded (12 mSv/year) but for the general public it was (2 mSv/year). Furthermore, the isodose curves obtained allowed to determine the distance, safer location and the type of radiological protection that we should use in each configuration.
Conclusion: Exposed workers should use personal dosimeter and they must employ protective measures and stand behind the mobile equipment. It is important to use radiological protection measures (e.g. increase the distance to the source and use a protector shield) to not exceed the dose limits, attending the ALARA principle.
Paediatric imaging radiation dose awareness and use of referral guidelines amongst radiology practitioners and radiographers
Purpose: To investigate radiologists' and
radiographers' awareness of radiation doses associated with
paediatric MI examinations and their use of referral
Methods and Materials: This study followed a prospective cross-sectional survey design whereby 168 questionnaires were handed out to 22 radiology practitioners and 146 radiographers performing duties at the primary Maltese referral centre for paediatric patients. Participants were asked to indicate the typical effective dose (ED) for several commonly performed paediatric imaging examinations, answer five true-false statements about radiation protection principles, and indicate their use of referral guidelines for paediatric imaging.
Results: A total of 112 questionnaires were returned resulting in an overall response rate of 66.7%. In general a poor level of awareness concerning the ED associated with paediatric imaging examinations was demonstrated. Indeed, only 20 % of imaging practitioners provided a correct ED estimate for the given radiation-based paediatric imaging examinations; 35 % indicated that they 'did not know'; 24 % underestimated the ED, and the remaining 21 % overestimated the ED. Nearly all participants had undertaken radiation protection training, with the type and duration of training undertaken varying across the sample. When asked about the use of referral guidelines for paediatric imaging, 77.3% claimed that they 'did not' or 'were not sure' if they made use of them.
Conclusion: Poor awareness of the doses associated with paediatric imaging examinations and the non-use of referral guidelines may limit imaging practitioners' role in the justification and optimisation of paediatric imaging examinations. Education and training activities to address such shortcomings are therefore encouraged.