Dose surveys and DRLs: critical look and way forward

Development of acceptable quality radiation dose levels for common computed tomography examinations: A focused multicenter study in United Arab Emirates

Purpose

Diagnostic Reference Level (DRL) is a practical tool for radiation dose optimization, yet it does not indicate the patient size or image quality. The Acceptable Quality Dose (AQD) introduced to address the limitations of the DRLs and it is based on image quality, radiation dose, and patient weight. The aim of this study is to establish the AQD for adult patients' undergoing Computed Tomography (CT) examinations (Head, chest, abdomen).

Methods

This study is conducted in the four main hospitals at the Ministry of Health and Prevention. Patient information and exposure parameters were extracted. All the acceptable images are scored for their quality assessments. Data is classified as seven weight groups, <50, 50-59, 60-69, 70-79, 80-89, 90-99, and ≥100 kg. The mean ± SD, median, and 75th are calculated for the CTDIvol and DLP for each weight group per examination.

Results

Out of 392, 358 CT examinations are scored with acceptable quality. The median CTDIvol values for the weight groups are obtained as 24.6, 25.4, 25.4, 25.0, 26.0, 27.0, and 29.0 mGy. Moreover, median DLP values are obtained as 576.7, 601.0, 616.5, 636.1, 654.0, 650.0, 780.0, and 622.5 mGy.cm, respectively, for head CT without Contrast Media (CM). Similar calculation for head CT with (CM), chest without CM, abdomen without CM, and chest and abdomen (with and without CM) CTs are presented.

Conclusion

Images with bad, unacceptable and higher than necessary qualities contribute to increasing patient dose and increasing the DRLs. The AQD for the selected examinations were lower than the proposed DRLs in the United Arab Emirates. The integration of image quality and patients size in the assessment of the AQD values provide effective model to compare radiation dose indices within facility and compare with others. The obtained results may be useful in terms of improving dose and the diagnostic quality in the national and international levels.

Development of image quality related reference doses called acceptable quality doses (AQD) in paediatric CT exams in Qatar

OBJECTIVES

To describe first experience of integrating assessment of image quality in paediatric X-ray computed tomography (CT) with analysis of the radiation dose indices to develop reference doses called acceptable quality dose (AQD).

METHODS

Image quality was scored by the radiologists at a tertiary care hospital in Qatar on a scale of 0 to 4 using the recently published scoring criteria. The patients undergoing head, chest and abdomen CT were divided in different weight groups as follows: < 5 kg, 5-< 15 kg, 15-< 30 kg, 30-< 50 kg, 50-< 80 kg and > 80 kg. The images that were clinically acceptable (score of 3) were included for assessment of median values of CTDIvol and DLP to obtain AQDs in different weight groups.

RESULTS

After initial training in image quality scoring of CT images of 49 patients by three radiologists, the study on 715 patients indicated 665 studies (93%) were clinically acceptable as per scoring criteria. The median CTDIvol values for the above weight groups were 16, 20, 22, 22, 27 and 27 mGy and the median DLP values for these weight groups were 271, 377, 463, 486, 568 and 570 mGy cm, respectively, for head CT. Similar values are presented for chest and abdomen CTs.

CONCLUSIONS

The first ever experience of starting with image quality assessment and integrating it with analysis of dose indices to obtain AQD values shall provide a workable model for others and values for comparison within the facility and in other facilities leading to optimisation.

KEY POINTS

• The first study to integrate image quality assessment with analysis of patient dose indices shows feasibility for routine practice in other centres. • The values of acceptable quality dose (AQD) were provided for head, chest and abdomen CT of children divided into weight groups rather than age. They shall act as reference values for future studies. • Verification of our findings on proportional increase in exposure parameters (CTDIvol and DLP) with weight by other investigators shall be helpful.

Radiation Dose of Patients in Fluoroscopically Guided Interventions: an Update

The benefits of fluoroscopically guided interventional procedures are significant and have established new standards in the clinical management of many diseases. Despite the benefits, it is known that they come with known risks, such as the exposure to ionizing radiation. To minimize such risks, it is crucial that the health professionals involved in the procedures have a common understanding of the concepts related to radiation protection, such as dose descriptors, diagnostic reference levels and typical dose values. An update about these concepts will be presented with the objective to raise awareness amongst health professionals and contribute to the increase in knowledge, skills and competences in radiation protection in fluoroscopically guided interventional procedures.

Development and validation of image quality scoring criteria (IQSC) for pediatric CT: a preliminary study

OBJECTIVE

To develop and assess the value and limitations of an image quality scoring criteria (IQSC) for pediatric CT exams.

METHODS

IQSC was developed for subjective assessment of image quality using the scoring scale from 0 to 4, with 0 indicating desired anatomy or features not seen, 3 for adequate image quality, and 4 depicting higher than needed image quality. Pediatric CT examinations from 30 separate patients were selected, five each for routine chest, routine abdomen, kidney stone, appendicitis, craniosynostosis, and ventriculoperitoneal (VP) shunt. Five board-certified pediatric radiologists independently performed image quality evaluation using the proposed IQSC. The kappa statistics were used to assess the interobserver variability.

RESULTS

All five radiologists gave a score of 3 to two-third (67%) of all CT exams, followed by a score of 4 for 29% of CT exams, and 2 for 4% exams. The median image quality scores for all exams were 3 and the interobserver agreement among five readers (acceptable image quality [scores 3 or 4] vs sub-optimal image quality ([scores 1 and 2]) was moderate to very good (kappa 0.4-1). For all five radiologists, the lesion detection was adequate for all CT exams.

CONCLUSIONS

The image quality scoring criteria covering routine and some clinical indication-based imaging scenarios for pediatric CT examinations has potential to offer a simple and practical tool for assessing image quality with a reasonable degree of interobserver agreement. A more extensive and multi-centric study is recommended to establish wider usefulness of these criteria.

Long-term experience and analysis of data on diagnostic reference levels: the good, the bad, and the ugly

OBJECTIVES

To analyze 11-year data of France for temporal trends in dose indices and dose optimization and draw lessons for those who are willing to work on creation and update of diagnostic reference levels (DRLs).

METHODS

The data from about 3000 radiology departments leading to about 750,000 imaging exams between 2004 and 2015 was analyzed, and patterns of reductions in dose for those below and above the DRLs were estimated and correlated with technology change.

RESULTS

Dose optimization achieved was important and significant in departments which were above or just below the DRL (p = .006) but not in those which were around half of the DRL values. The decrease in 75th percentile value of Kerma air product (KAP) for chest radiography by 27.4% between 2004 and 2015 was observed with the number of flat panel detectors increase from 6 to 43%. A good correlation between the detector type distribution and the level of patient radiation exposure is observed. Otherwise, setting DRLs for standard-sized patient excludes patients lower and higher weighted than "standard."

CONCLUSIONS

The concept of DRL may become obsolete unless lessons drawn from the experience of users are taken into account. While establishing DRLs should be part of the regulations, setting up and updating values should be governed by bodies whose decision-making cycle is short, at the most 1 year. A local rather than national approach, taking into account body habitus and image quality, needs to be organized.

KEY POINTS

• The technology changes faster than regulations. Requirement of DRL establishment should be part of the regulations; however, setting and updating values should be the role of professional societies. • The concept of DRL, highlighting the 75th percentile values and dedicated to standard-sized adult, misses optimization opportunities in the majority of patients who are below the 75th percentile value and outside the range of standard-sized adult. • The ugly aspects of the DRL concept include its non-applicability to individuals, no customization to clinical indications, and lack of consideration of image quality.

Organ doses evaluation for chest computed tomography procedures with TL dosimeters: Comparison with Monte Carlo simulations

Purpose

To evaluate organ doses in routine and low‐dose chest computed tomography (CT) protocols using an experimental methodology. To compare experimental results with results obtained by the National Cancer Institute dosimetry system for CT (NCICT) organ dose calculator. To address the differences on organ dose measurements using tube current modulation (TCM) and fixed tube current protocols.

Methods

An experimental approach to evaluate organ doses in pediatric and adult anthropomorphic phantoms using thermoluminescent dosimeters (TLDs) was employed in this study. Several analyses were performed in order to establish the best way to achieve the main results in this investigation. The protocols used in this study were selected after an analysis of patient data collected from the Institute of Radiology of the School of Medicine of the University of São Paulo (InRad). The image quality was evaluated by a radiologist from this institution. Six chest adult protocols and four chest pediatric protocols were evaluated. Lung doses were evaluated for the adult phantom and lung and thyroid doses were evaluated for the pediatric phantom. The irradiations were performed using both a GE and a Philips CT scanner. Finally, organ doses measured with dosimeters were compared with Monte Carlo simulations performed with NCICT.

Results

After analyzing the data collected from all CT examinations performed during a period of 3 yr, the authors identified that adult and pediatric chest CT are among the most applied protocol in patients in that clinical institution, demonstrating the relevance on evaluating organ doses due to these examinations. With regards to the scan parameters adopted, the authors identified that using 80 kV instead of 120 kV for a pediatric chest routine CT, with TCM in both situations, can lead up to a 28.7% decrease on the absorbed dose. Moreover, in comparison to the standard adult protocol, which is performed with fixed mAs, TCM, and ultra low‐dose protocols resulted in dose reductions of up to 35.0% and 90.0%, respectively. Finally, the percent differences found between experimental and Monte Carlo simulated organ doses were within a 20% interval.

Conclusions

The results obtained in this study measured the impact on the absorbed dose in routine chest CT by changing several scan parameters while the image quality could be potentially preserved.

Radiological Justification for and Optimization of Nuclear Medicine Practices in Korea

Nuclear medicine is a rapidly growing discipline that employs advanced novel hybrid techniques that provide unique anatomical and functional information, as well as targets for molecular therapy. Concomitantly, there has been an increase in the attention paid to medical radiation exposure. A radiological justification for the practice of nuclear medicine has been implemented mainly through referral guidelines based on research results such as prospective randomized clinical trials. The International Commission on Radiological Protection recommends diagnostic reference levels as a practical mechanism to optimize medical radiation exposure in order to be commensurate with the medical purpose. The Korean Society of Nuclear Medicine has been implementing radiological optimization through a survey of the protocols on how each hospital determines the dose of administration of each radiopharmaceutical. In the case of nuclear medicine, radiation exposure of caregivers and comforters of patients discharged after administration of therapeutic radiopharmaceuticals can occur; therefore, optimization has been implemented through written instructions for patients, based on international recommendations. The development of patient-radiation-dose monitoring software, and a national registry and management system of patient-radiation-dose is needed to implement radiological optimization through diagnostic reference levels. This management system must work in agreement with the "Institute for Quality Management of Nuclear Medicine", and must take into account the medical reality of Korea, such as low medicine fee, in order to implement reasonable radiological justification and optimization.